We compared the acute (96 h) lethal toxicity to six freshwater invertebrate species of NaHCO3 and two synthetic CBM waters, with ionic proportions representative of water from CBM wells across New South Wales (NSW) and Queensland (Qld), in Australia. The ranking of LC50 values expressed as total salinity was consistent with the hypotheses. However, when toxicity was expressed as bicarbonate concentration, the hypothesis that the toxicity of coal bed waters would be explained by bicarbonate concentration was not well supported, and other ionic components were either ameliorating or exacerbating the NaHCO3 toxicity. Our findings showed NaHCO3 was more toxic than NaCl and that the NaHCO3 proportion of synthetic CBM waters drives toxicity, however other ions are altering the toxicity of bicarbonate.Concentrations of major ions in coal mine discharge waters and unconventional hydrocarbon produced waters derived from coal bed methane (CBM) production, are potentially harmful to freshwater ecosystems. Bicarbonate is a major constituent of produced waters from CBM and coal mining. However, little is known about the relative toxicity of differing ionic proportions, especially bicarbonate, found in these CBM waters. As all freshwater invertebrates tested are more acutely sensitive to sodium bicarbonate (NaHCO The concentrations of major ions or salinity is increasing in freshwaters from a range of human activities (Jackson and Funk 3-) which is much less abundant in sea water (about 0.3% of anions)  https://cfpub.epa.gov/ecotox/ showed that six of the nine freshwater animals compared , were 1.2 to 4.1 times more sensitive to NaHCO3 than NaCl  mortality of six freshwater invertebrate species. Additionally, we used previously published sodium bicarbonate data  Department of Planning, Industry and Environment had collected from 15 mines across five geological basins . This represents five of the six basins in NSW with coal mines, one of these (Clarence-Moreton) crosses into southern Queensland. These data included concentrations of major ions: sodium, potassium, calcium, magnesium, chloride, sulphate, and bicarbonate from 235 samples. Data collected were checked for ionic balance; any sample which was not balanced or did not contain data for all major ions, was removed from the data set.To determine the effect of coal bed waters on stream invertebrates, we sought to characterise the ionic compositions of these waters, and then determine if they could be grouped into waters with similar ionic compositions or “water types”. Alternatively, the changes in ionic composition from site to site may have rested on a continuous gradient, preventing grouping into water types.To show the relative concentrations of anions and cations within the water, we converted the concentration data (mg/L) into milliequivalents per litre (m equiv/L). As variability between samples from the same site was minimal, the mean concentrations (in m equiv/L) of each ion were then determined for each site. A range-standardisation was then conducted to determine the relative proportions of ions in each of the 15 sites. These range standardisations were then plotted on a Schoeller Diagram Fig. .Fig. 1ScAccess to coal bed waters from working mines was not granted, as such water chemistry data that had been previously collected from mine sites, were used to produce synthetic coal bed waters. Two synthetic coal bed waters WT1 and WT2) were prepared by adding reagent grade  salts to dechlorinated Sydney tap water. These synthetic waters were made to match the mean proportions identified for Water Types 1 and 2  were not able to be tested to all water types but were included to increase the generality of our findings across species.We prioritised testing of  Kefford . Other sA. pusillus and J. kutera, were collected from Rouchel Brook  and the Hunter River , respectively. P. australiensis was collected from South West Arm Creek  within the Royal National Park. These three field-collected species were obtained using hand nets after disturbing the bankside vegetation or stream substrate.Three of the six species studied were collected from near Sydney, NSW, Australia: The invertebrates were transported to the laboratory in the water from their collection site, in a portable cooler containing nylon mesh and conditioned leaves collected at the site, to provide substrate and food. Water was kept cool using ice placed outside the coolers and the water was aerated. On arrival at the laboratory, the invertebrates were placed in the control water: dechlorinated Sydney tap water , Jappa kutera [Ephemeroptera: Leptophlebiidae], Cherax destructor [Decapoda:Parastacidae] and Isidorella newcombi [Hygrophila: Planorbidae].A pusilis, and J kutera nymphs were 5–11 mm body length excluding cerci. C. dubia were neonates (less than 24 h old). P. australiensis were 15–30 mm in length. C. destructor were 40–80 mm in length. Mature I. newcombi were chosen.C. dubia, which was conducted according to  did not exceed 10% or one individual at the end of the test. All tests conducted were valid.With the exception of to USEPA , each teto USEPA . Ten indMajor ions in the test waters were determined by ion chromatography at the beginning of the experiments, in accordance with APHA, 4110-B, using a National Association of Testing Authorities, Australia (NATA) accredited commercial laboratory . Total alkalinity and bicarbonate alkalinity were determined by a double-indicator titration method at the beginning and end of experiments. Osmotic pressure was measured as osmolality (mOsm/kg) using a Fiske Model 210 micro-osmometer .All statistical analysis was conducted using SPSS 20. Concentration response curves were generated using Probit regression, with mortality as the dependent variable and total salinity (mg/L), electrical conductivity , bicarbonate concentration (mg/L), or osmolality (mOsm/kg) S the index values and concentration response curves based on total salinity, EC, bicarbonate (HCO3−) concentration, and osmolality values after 96 h. Osmolality data are presented in the supplementary material as it resulted in identical findings to that of EC. NaHCO3 toxicity data obtained using the identical methods and calculated in Hills et al.  which had relatively high levels of chloride (60–90% of anions) but still had significant amounts of bicarbonate (5–30% of anions). The remaining six were designated Water Type 2 (WT2) and had relatively lower chloride (10–25% of anions) and relatively higher bicarbonate (70–80% of anions). In both water types, sodium was the dominate cation (90–95% of cations). One of the WT2 mines also exhibited a higher proportion of sulphate, calcium, and magnesium than any of the other samples. Given this ionic proportion was relatively rare (≈6% of sites) in our dataset, we will not consider it further  had a lower LC10 for WT1 than WT2 and C. dubia had a similar LC10 for both WT1 and WT2.Regardless of whether salinity is expressed as EC Table , total sP. australiensis, mortality is achieved with a lower concentration of bicarbonate ion in WT1 compared with NaHCO3 alone, and a higher concentration of bicarbonate ion in WT2 compared with NaHCO3 alone.Expressing toxicity in terms of bicarbonate concentration  shows a different pattern Table , and 4b.In water collected from 15 mines across five geological basins  ionic proportions were generally consistent with that previously reported in eastern Australia (NSW and Queensland)—that is Surat —where sodium and chloride are the dominant cation and anion respectively, and the proportion of bicarbonate (5–30%) being less than chloride (60–90%)WT2 (sodium and bicarbonate based)—where sodium and bicarbonate are the dominant cation and anion respectively, with the proportions of chloride (10–25%) being less than bicarbonate (70–80%). In both water types, sodium represented 90–95% of the measured cations. All coal bed waters examined for their toxicity had measurable but relatively low calcium (0.03–2.10%), magnesium (0.04–1.39%), potassium (0.20–3.99%), and sulphate (0.00–0.63%) concentrations.Geochemical processes, including biogenic and thermogenic processes, are typically associated with coal beds and lead to the comparable ionic compositions described above: high sodium, bicarbonate and chloride, and low calcium, magnesium and sulphate . Based on LC50 values expressed against salinity; the synthetic coal bed water with the highest proportion of bicarbonate (WT2) was also more toxic than the water with a lower proportion of bicarbonate (WT1), in three of the four species tested. The mayfly A. pusillus and J. kutera) having a lower LC10 for WT1 than WT2, and C. dubia having a similar LC10 for both WT1 and WT2. Two of the exceptions, A. pusillus and J. kutera are mayflies (Ephemeroptera). This insect order is considered to be particularly sensitive to salinity with low bicarbonate concentrations, relative to other insects  do not overlap, which is predicted if bicarbonate is solely driving toxicity in these waters. For P. australiensis, which was the most sensitive to bicarbonate, the NaHCO3 water was more toxic than WT2, which was more toxic than WT1. This indicates that other ions within the artificial coal bed waters were reducing the toxicity of bicarbonate, or the concentrations of other ions and/or their ratios were otherwise increasing the survivability of P. australiensis within these waters  within WT2 may have been having an ameliorating effect, while other ions (or their ratios) in WT1 were increasing toxicity.Furthermore, when toxicity was expressed in bicarbonate concentration (mg/L), the concentration response curves for each water type  which was more toxic than the sodium chloride type water (WT1), although for LC10 values there were exceptions. A coal bed water with higher bicarbonate concentration is acutely toxic to freshwater invertebrates at lower salinity than one with a lower bicarbonate concentration.In general, when we compare the acute toxicity of each synthetic coal bed water in terms of salinity , against each of the three key species tested Figs. , and 4, The bicarbonate concentration and salinity of both WT1 and WT2 at their respective LC10 and LC50 concentrations determined by these experiments, closely match the bicarbonate concentrations and salinities commonly found in coal bed waters of Australia and the USA. In some cases, bicarbonate concentrations of up to 3.5 g/L have been measured in coal bed waters (Hoke et al. 3 Supplimentary Data


With continuous population growth and farmland decrease, the food security is seriously threatened. Farmland reclamation has been used as a means of raising the agricultural productivity and improving the ecological environment. However, the lack of reclaimed soil represents a serious problem. To verify the feasibility and effect of using large amounts of iron tailings to construct farmland, ten treatments (T1–T10) were designed to represent different soil profiles of regional normal farmland and constructed profiles using iron tailings. All treatments involving an iron tailings layer below topsoil exhibited higher soil water contents. The field capacity under T3 (20-cm iron tailings layer below cinnamon soil (b)) was 19.20% higher than that under T7 (20-cm red clay layer below cinnamon soil (b)), and the field capacity under T5 (20-cm iron tailings layer below cinnamon soil (a)) was 2.26% higher than that under T9 (20-cm red clay layer below cinnamon soil (a)). The soil water contents under T3 and T5 were almost the same as those under T7 and T9, respectively. The water-holding capacity of the 30-cm iron tailings layer (T6) was better than that of the 20-cm iron tailings layer (T2). Additionally, none of the treatments caused salt injury to maize. The maize height and stem thickness under the treatments employing iron tailings layers below topsoil were significantly greater than those in normal farmland; the maize height and stem thickness under T3 were 136.82% and 32.02% greater, respectively, than those under T7, and the values under T5 were 9.13% and 9.56% greater, respectively, than those under T9. The maize yields matched or even surpassed those in normal farmland, namely, the maize yield under T5 was equal to that under T9, and the maize yield under T3 was 12.69% higher than that under T7. In general, the application of an iron tailings layer below topsoil to construct farmland is a feasible and environmentally friendly way to realize sustainable farmland utilization and is beneficial to soil quality and crop yield improvement. Collectively, these results provide insight into the efficient utilization of iron tailings and environmental protection. China is one of the first countries worldwide to exploit and utilize iron ore, with abundant reserves and a high annual output. The increasing scale of mining inevitably causes large-scale land disturbance and severe damage to the vegetation, soil, and landscape of the original landform, posing a serious threat to the regional ecological security5. The conflict between human development and farmland protection in China has become increasingly aggravated7. Therefore, it is necessary to reclaim abandoned mines, construct farmland and accelerate ecological restoration9.Mining is an economic activity that intensified during the twentieth and twenty-first centuries to satisfy the demands of industrial development, which has caused serious social, environmental and economic impacts, especially in resource-rich regions10. Among these stages, soil reconstruction constitutes the core component of land reclamation and ecological restoration in mining areas, and the quality of reconstructed soil directly determines the quality of land reclamation11. Soil reconstruction refers to the implementation of appropriate reconstruction techniques and application of engineering measures and physical, chemical, biological and ecological methods to construct appropriate soil profiles and soil fertility conditions for soil restoration purposes in industrial and mining areas. At the same time, it is necessary to stabilize the landscape, restore and improve the soil productivity rapidly, and improve the environmental quality of the reconstructed soil11. The materials used for soil reconstruction include both soil and the soil matrix and other mine waste materials, such as rock, gangue, fly ash, slag, low-grade ore, or a mixture of two or more of these materials12. The most ideal soil reconstruction material is the original soil stripped in the mining process, but it is difficult to obtain sufficient high-quality soil13. Especially in China, many historical legacy mines exist, and there is a serious lack of soil resources, which makes appropriate soil substitute materials vital to mine site reclamation.Land reclamation can be divided into five stages from the perspective of the corresponding workflow, including landform reshaping, soil reconstruction, vegetation reconstruction, landscape representation, and biodiversity reorganization and protection14, involve a reasonable ratio of solid waste and other nontopsoil resource materials from the perspective of land reclamation and sustainable environmental development in mining areas to provide new soil suitable for plant growth15. The preferred soil substitute materials are generally industrial solid waste materials obtained from mining areas. Many laws and regulations concerning land reclamation in Western countries stipulate that it is necessary to analyze the physicochemical properties and heavy metal content in the soil matrix and overlying strata and subsequently select suitable soil substitute materials before mining17. For example, in Germany, there occur fewer topsoil sources, some of which include stripped topsoil in mining areas and artificial soil18. In the United States of America, it is necessary to identify and screen suitable soil substitute materials from the overburden strata of coal seams when the amount of stripped soil is insufficient. Baker et al.19 used coal gangue prepared from combustion products such as fly ash and sludge to produce stable soil that could be directly applied in farmland. Wilson and Skousen20 used unweathered gray sandstone and weathered brown sandstone in soil reconstruction of an open-pit mine in West Virginia, USA, and experimental observations over eight consecutive years revealed that weathered brown sandstone soil exhibited satisfactory physicochemical properties and was an ideal soil substitute material. In Indonesia, the utilization of fly ash as a soil substitute material in mining areas was achieved by mixing topsoil and fly ash based on the physical characteristics and boron amount eluted from fly ash21. The incorporation of eco-engineering tailings into soil-like growth media has been advocated as a promising technique for cost-effective and sustainable rehabilitation of iron tailings without the need for large volumes of natural topsoil22. However, few studies have considered iron tailings as a soil substitute material.Soil substitute materials, also referred to as artificial soil or new soil source materials24 and fly ash26 are usually selected as alternative materials for soil reconstruction. Through pot and plot experiments, Hu et al.13 used the overlying rock and soil layer in an open-pit coal mine in Inner Mongolia as a matrix and incorporated different additives to improve topsoil alternatives for dump reclamation, and the results demonstrated that Layer III of the matrix after weathering was more suitable as a topsoil substitute material. In addition, his team added peat27, modified straw28, vermiculite29, and humic acid30 and improved and optimized the formula of the applied soil substitute material by assessing alfalfa growth and resisting performance. Because of the different ore-forming geological conditions occurring in different regions, the physical and chemical properties of mining solid waste materials are different, so the proportion of solid waste materials exhibits notable regional characteristics. Hu et al.31, Duo and Hu32, and Zhao et al.33 proposed a new technology of using Yellow River sediments as reconstructed soil material to mitigate coal mining-induced subsidence. In regard to soil reconstruction during iron ore reclamation, Lu34 studied the physical and chemical properties of dry discharge iron tailings and corresponding reclamation technology and found that a grinding cultivation matrix covering a 30-cm iron tailings layer could represent a suitable reclamation mode. Fan35 used the pot test method to transform iron ore waste rocks and soil into reclamation mixed soil according to different mixing proportions. By analyzing the physical and chemical properties of the obtained mixed soil and its impact on maize growth, it was found that iron ore waste reclamation mixed soil at a 3:7 ratio was the most suitable for maize growth.Research on soil substitute materials in China started relatively late. Regarding coal mining area reclamation, coal gangue36. These tailings ponds not only involve a large amount of land occupation but also involve the need for passive tailings pond reclamation. There are many similar places in the world. Western Liaoning Province, a region with large amounts of iron tailings, belongs to the semiarid and typical ecologically fragile area, where the native topsoil is relatively infertile, and reclamation soil resources are seriously lacking, which has become a serious bottleneck in the land reclamation process in this area and has caused various problems, such as an insufficient soil cover thickness and poor vegetation growth. Wei and Liang37 innovatively proposed the idea of mixing iron tailings with topsoil to increase the soil layer thickness and improve medium- to low-yield fields in western Liaoning Province. It has also been demonstrated that the incorporation of an appropriate amount of iron tailings into topsoil can improve soil physical properties and crop yields and does not contaminate farmland soil38. In addition, Davila et al.39 and Almeida et al.40 evaluated productivity and metal accumulation in the Fundao dam area , released large amounts of iron tailings and determined that the concentrations of metals remained within the limits allowed for human consumption, thus not posing long-term risks; they indicated that the deposited tailings would not cause future regional heavy metal contamination. The results of our previous study revealed that the contents of heavy metals such as Cd, Cr, Cu, Zn, Pb, Ni, Hg and As did not exceed the risk intervention values for farmland contamination in China41, and the heavy metal content was even lower than that in regional native soil, with no toxicity and no pollution sources for soil and crops38. Thus, constructing farmland with large amounts of iron tailings could represent a promising method for farmland reclamation.At present, waste iron tailings are mostly used as soil fertilizers worldwide, but their usage is limited, making it difficult to solve various problems, such as iron tailing accumulation and pollution. In northern China, large amounts of iron tailings produced during iron ore mining and selection are stored in tailings ponds and are often regarded as waste materialsFew studies regarding the notable use of iron tailings for farmland construction in mining areas have been reported to date. Therefore, our general aim was to demonstrate the feasibility of farmland construction involving large amounts of iron tailings. Via full utilization of common raw materials in the mining area, including topsoil, iron tailings, waste rocks and stripped soil, 10 types of farmland soil profiles were designed. Considering the semiarid climatic conditions in the study area, soil moisture characteristics were closely monitored. Additionally, crop growth conditions and yields were regularly monitored. The main objectives of this study were to (1) verify the feasibility of a new soil reconstruction material (iron tailings) that could be used to construct farmland and describe the associated reclamation technology and construction process and (2) to analyze soil properties and crop growth and yield after reclamation.43. The original farmland in the region exhibits a thin tillage layer (approximately 15 cm), heavy clay soil texture, weak soil moisture regimes, and low soil organic matter content, which leads to the farmland in western Liaoning Province mostly providing medium- and low-yield fields. Aridity is the primary limiting factor of the regional farmland quality44. In addition, the thin topsoil layer leads to an extreme lack of soil resources for land reclamation.The experimental site is located in a newly reclaimed farmland area in Xincheng village , Xiaotang town, Jianping County, Chaoyang city, Liaoning Province, northern China , with no toxicity and pollution risks to soil and crops. Topsoil was obtained from topsoil dumps formed via topsoil stripping during mining, exhibiting two colors, i.e., brown and yellow, but both these soils were cinnamon soil in the Chinese soil classification system43. Thus, these soils were named cinnamon soils (a) and (b), respectively. In addition, all the structural materials were stacked near the experimental site, and the essential traits of the red clay, iron tailings, and stripped topsoil are listed in Table Considering the specific local conditions, 10 experimental plots (12 × 6 m) were established combined with previous research results for iron tailings mixing into topsoil  Fig. . In eachZea mays L., i.e., Gaoke 985) was planted in each experimental plot according to the national guidelines for maize cultivation. The planting density was 60,000 plants per hectare. The seeding depth ranged from approximately 3 to 5 cm. Before seeding, 450 kg of stable composite fertilizer (the effective content of N-P2O5-K2O = 25-11-12%) was applied per hectare as base fertilizer. All the fertilizer was first evenly broadcast across the surface and then incorporated with a rotary tiller. Drip irrigation pipes were laid in the experimental plots, and supplementary irrigation was performed via drip irrigation.After reclamation, each plot was covered with mulch, and maize , and crop growth and yield under the different treatments were monitored. The bulk density reflects the effect of iron tailings on improving the local clayey soil texture. The feasibility of replacing soil with iron tailings as a water-retaining layer to obtain reclaimed soil was reflected by soil moisture indicators, and the feasibility of using iron tailings to increase crop yields was characterized by crop growth and yield indicators.45. Both the soil water content and soil EC were measured with a moisture teller (PICO-BT 0809)48. The plant height and stem thickness of maize were measured once every 5 days during the growing period using a standard meter and Vernier caliper, respectively. The dry weight and maize yield were measured at harvest to determine the grain yield of 30 randomly selected plants in each experimental plot, which was converted into the per hectare yield.Soil and crop samples were collected in July 2020 and October 2020, and during each sampling, the ten experimental plots were sampled. Samples were obtained from the topsoil layer (0–20 cm). Both the bulk density and field capacity were measured via the cutting ring method49. One-way analysis of variance (ANOVA) followed by Tukey’s test (P < 0.05) was used to calculate the significant difference in soil physical indicators among the different treatments. Origin 2017 was used to graph and present the data.The experimental data were first processed in Excel 2016 , and the STDEVP function in Excel 2016 was used to calculate the standard deviation (SD) of each treatment. Then, the experimental data were analyzed using statistical software SPSS 25 −3 and was ranked as T8 < T4 < T1 < T5 < T2 < T9 < T6 < T10 < T3 < T7. Among all treatments, a 5-cm mixed iron tailings-topsoil layer was employed under T1, T4 and T8, and the bulk density was lower than that under the other treatments. The topsoil under the T2, T5, T6, T8 and T10 treatments was cinnamon soil (a), and the bulk density was lower than that under the T3 and T7 treatments, whose topsoil comprised cinnamon soil (b). The bulk density under T8 was 5.50% lower than that under T7, and the value under T4 was 3.08% lower than that under T2. Mixing iron tailings into topsoil could significantly reduce the bulk density. The bulk density of cinnamon soil (a) was lower than that of cinnamon soil (b).The bulk density under the different treatments is shown in Fig. The field capacity data are shown in Fig. The soil water content under the different treatments during maize growth was monitored for one month, and the results are shown in Fig. −1, followed by T4, with values ranging from 0.24 to 0.40 S m−1. Overall, the soil EC was ranked as T8 < T4 < T10 < T1 < T3 < T9 < T6 < T2 < T5 < T7. Normal growth and development of crops require soil nonsalinization, in which the soil EC value should be lower than 2 S m−144. The maximum EC of the topsoil under all treatments was 0.46 S m−1, which is far lower than the threshold limit. Therefore, the soil EC under each treatment indicated suitable growth and development conditions for crops.A moisture teller was used to monitor the soil EC under each treatment during maize growth for one month, and the results are shown in Fig. The plant height of maize was measured for one month during the maize growing period. As shown in Fig. The stem thickness of maize was determined while measuring the plant height, and the results are shown in Fig. The dry weight data of maize are shown in Fig. −1 and indicated no significant differences among the different treatments (P < 0.05), while the crop yields could be ranked as T1 < T2 < T6 < T4 < T7 < T10 < T5 < T9 < T8 < T3. T3 attained the maximum yield . The yield under T4 was 19.24% higher than that under T2, and the value under T8 was 7.32% higher than that under T7. The yield under T3 was 12.69% higher than that under T7, and the crop yield under T5 was basically the same as that under T9. Compared to the T2 treatment, the yields under the T6, T5 and T10 treatments were all higher, by 17.66%, 26.72% and 25.83%, respectively.Maize was harvested in October 2020. The crop yields under each treatment are shown in Fig. 50. In this study, based on the theory of soil-forming factors and reconstruction of soil parent material, different farmland soil profiles were constructed using solid waste materials  generated during mining as soil substitute materials. The entire reclamation project was completed in two months, and maize was planted in the same year. The maize growth level was basically consistent with that in local normal farmland, and there was no contamination in the reclaimed farmland plots, which indicate the feasibility of constructing farmland involving large amounts of iron tailings.The theory of soil-forming factors posits that soil is the product of multiple natural factors, such as biology, climate, parent material, topography, and time, as well as human activities51. Improving the soil storage capacity above that attributable to atmospheric precipitation is the key to agricultural production in western Liaoning. Due to the clayey soil texture of native soil in western Liaoning, its water retention capacity is poor. Therefore, the main purpose of using iron tailings to reclaim farmland is to obtain a certain thickness of the iron tailings layer below topsoil as a water-retaining layer in farmland and improve the water-retaining capacity. The field capacity is frequently used to measure the water retention capacity of soil, which exhibits significance in guiding agricultural production and irrigation53. The results of the field capacity and soil water content in the experiment revealed that the field capacity under all treatments entailing the placement of iron tailings below topsoil was higher than that under the treatments entailing the placement of red clay below topsoil. In addition, increasing the filling thickness of iron tailings could effectively improve the field capacity. The reason is that the specific surface area is closely related to the field capacity, and the higher the specific surface area is, the greater the ability to accept water molecules and the greater the ability to conserve water54. Iron tailings are mostly irregular granular materials55, and their specific surface area is higher than that of clay particles, resulting in an increase in the field capacity. With increasing filling thickness of iron tailings, the water retention capacity increased. Regarding the soil water content, variation may be affected by regional rainfall. At the early stage of monitoring (1st–18th days), i.e., in early and middle July, regional rainfall occurred frequently, and the soil water content increased and stabilized. However, during the late monitoring period (18th–27th days), i.e., in late July, regional rainfall occurred less frequently, and evaporation was high, resulting in a significant decrease in the soil water content, which eventually stabilized. Moreover, the soil water content obtained by placing iron tailings below topsoil was equivalent to or even higher than that obtained by placing red clay. Although the moisture content in regional dry discharge iron tailings is low, only 8.9%, due to the satisfactory water retention capacity of its irregular particles, iron tailings could effectively store rainfall and provide water for topsoil during regional droughts, so that the moisture content in reclaimed soil was higher than that in regional normal farmland soil. The above fully demonstrates that when a large amount of iron tailings is used to construct farmland in the semiarid area of western Liaoning, placing an iron tailings layer of certain thickness instead of soil below topsoil as a water-retaining layer could represent a suitable way to effectively improve the moisture characteristics of reclaimed soil.Agriculture in the semiarid area of western Liaoning is supported by natural rainfall, and atmospheric precipitation is the main source of soil moisture56. The placement of iron tailings below the topsoil layer as a water-retaining layer may increase the content of water-soluble salts in soil and limit seed germination and crop growth when improving soil moisture in the region. It has been widely reported that the soil EC is an index for soil water-soluble salt determination, which is an important soil property44. The dynamic monitoring results of the soil EC indicated that EC exhibited an overall upward trend from Days 1 to 21 but gradually decreased thereafter. The whole process is consistent with the change in the soil water content. The soil EC under the treatments involving the placement of iron tailings below topsoil was higher than that under the treatments involving the placement of red clay below topsoil during the monitoring period, indicating that placing iron tailings below topsoil could increase the soil EC. The EC of iron tailings is approximately 30% lower than that of topsoil because the moisture content in iron tailings (8.9%) is lower than that in topsoil (approximately 48%). However, placing iron tailings below topsoil could increase the topsoil EC because when iron tailings are used as a water-retaining layer, the resulting moisture content is higher than that in regional native soil, and when there occurs high evaporation in the region and a lack of rainfall, the iron tailings layer could provide more moisture for topsoil so that more salt could become concentrated in the topsoil layer. Normal growth and development of crops require soil nonsalinization, in which the soil EC value should be lower than 2 S·m−144. Although placing iron tailings below topsoil could increase the soil EC, the dynamic monitoring results indicated that the maximum soil EC under each iron tailings filling structure treatment was 0.43 S m−1, which is far below the salt tolerance limit of crop growth. Therefore, the use of large amounts of iron tailings instead of soil for filling below topsoil as a water-retaining layer will not result in salt injury to crops, which further proves that the use of large amounts of iron tailings in farmland construction is feasible.An increase in soil moisture may lead to an increase in soil salinity. The processes of salt transport with water and salt removal by water vividly describe the influence of water on soil salinity movement57. Soil drought reduces the water use efficiency, destroys photosynthetic organs, hinders crop metabolism and root growth, and directly affects the crop chlorophyll content58. Maize is the dominant crop in western Liaoning, its roots are mainly concentrated in the 0–40 cm soil layer, and the soil moisture content in the root layer directly affects crop root development59. The results demonstrated that the plant height and stem thickness of maize under the treatments involving the placement of iron tailings below topsoil were higher than those under the treatments involving the placement of red clay below topsoil, which suggested that the use of iron tailings instead of soil below topsoil could effectively promote maize growth. Compared to normal farmland, the plant height of maize grown in iron tailings-filled farmland was 9.13% greater, and the stem thickness was 9.56% larger at maturity. The reason is that the water-retaining layer comprising iron tailings could effectively improve the soil water content, thereby enhancing the water utilization rate so that maize would not lack moisture during growth and could grow fast. In terms of the maize yield, the value under T3 was 12.69% higher than that under T7, and the maize yields under T5 and T9 were basically the same. The maize yield in normal farmland in western Liaoning is approximately 9,000 kg·ha−160. The yields under T3, T5 and T10 all exceeded 9,000 kg·ha−1, which is higher than that in local normal farmland, indicating that the maize yield in farmland constructed with iron tailings was equivalent to or even better than that in regional normal farmland during the year of construction. compared to T2 (20-cm iron tailings layer below a 20-cm topsoil layer), the yields under T5 (20-cm iron tailings layer below a 30-cm topsoil layer) and T6 (30-cm iron tailings layer below a 20-cm topsoil layer) were 26.72% and 17.66% higher, respectively, indicating that the increase in the thickness of the constructing layer could improve the maize yield to a certain extent. This may occur because the increase in the thickness of the constructing layer could effectively improve the field capacity and moisture content, effectively enhance the growth of maize, and provide the moisture needed for the formation of maize grains during the grain-filling period, thereby increasing the maize yield. Thus, from the perspective of crop growth and yield, it is feasible to use a large amount of iron tailings instead of soil to construct a farmland water-retaining layer, which could promote maize growth and effectively improve the maize yield.Crop growth and yield are important indicators to determine whether the performance of reconstructed farmland is satisfactory. Soil drought and water shortages are important factors restricting crop growth and leading to low yields in western Liaoning60. Mixing sand in clay soil is an effective way to improve the clayey soil texture61, and as expected, the results in this study supported this finding. The bulk density is one of the important indices reflecting the soil texture, which is closely related to soil and agricultural ecosystems and notably influences soil thermal, hydraulic and mechanical properties63. Our results indicated that the bulk density under the treatment with a 5-cm mixed iron tailings-topsoil layer was 3.08% lower than that under the treatment with no iron tailings mixed into topsoil, which indicates that the application of a 5-cm iron tailings layer atop topsoil could effectively reduce the soil bulk density. The reason is that although the bulk density of iron tailings (1.53 g·cm−3) is higher than that of regional stripped topsoil (1.39 or 1.41 g·cm−3) (Table 64. An increase in the sand content could yield a loose and porous soil environment and increase the soil porosity, thereby reducing the bulk density and effectively improving the texture of the native clayey soil.Our research group previously proposed that the application of a 5-cm iron tailings layer atop topsoil in farmland could improve the soil texture and soil moisture characteristics while increasing the soil thickness. Therefore, we applied this technique in the process of using a large amount of iron tailings to construct farmland for further verification. The soil texture of the original farmland soil in western Liaoning is dense, belonging to silty clay loam, which seriously affects crop growth65. An increase in the soil porosity could enhance the distribution of soil pores, expand the soil storage space, store more water in soil pores, and effectively improve the soil water holding capacity. Although the application of a 5-cm iron tailings layer atop topsoil increased the soil moisture content, resulting in an increase in the soil EC to a certain extent, its value was far below the maximum salt tolerance limit of crop growth and would not result in salt injury to crops. Soil texture improvement and soil moisture content increase could effectively promote maize growth, and the plant height and stem thickness of maize during the growth period were 9.13% and 9.56% greater, respectively, than those under the treatments without iron tailings application. At the maize grain-filling stage, the increase in soil moisture was beneficial to the formation of maize grains, and the yield of maize was 12.69% higher than that under the treatments without iron tailings application. These results are also consistent with the findings of Yang38 and Ji et al.66, who reported that applying iron tailings to topsoil significantly promoted crop growth. Other studies have also reported that restoration efforts in arid ecosystems should focus on increasing the sand content in soils near the surface to reduce the evaporative water loss and improve the soil quality and crop health67.Changes in the soil texture could lead to changes in soil hydrothermal conditions, thereby affecting the soil quality and crop growth and yield. In our study, the field capacity, soil water content, maize plant height, stem thickness and yield obtained by placing a 5-cm iron tailings layer atop topsoil were all better than those obtained by not mixing iron tailings into topsoil. The reason is that the application of iron tailings to topsoil followed by plowing and mixing could increase the soil porosity and decrease the bulk density. Moreover, the bulk density and soil porosity greatly influence the soil water content3 per hectare, and if the local price of topsoil is approximately 30 CNY ·m−3, then, in this case, the reclamation investment cost can be reduced by 45,000 CNY per hectare50. While saving many guest soil sources, secondary land damage is reduced. Finally, the problem of the disposal of solid waste generated in the mining process can be solved. Agricultural resource utilization of iron tailings, used for medium- and low-yield field improvement and reclamation, not only consumes large amounts of beneficiation iron tailings accumulated in inventories but also prevents land occupation and contamination problems attributed to iron tailings accumulation and improves medium- and low-yield fields, thereby greatly protecting soil resources. It can thus be observed that using solid waste as a soil substitute material can provide certain economic and ecological benefits.The selection of a reasonable construction scheme based on experiments using solid waste materials produced in mining processes as soil substitute materials is of great significance for land reclamation in mining areas with scarce soil resources. First, this allows the problem of poor vegetation growth due to an insufficient thickness of the overlying soil in these areas to be solved. Second, the cost to mining enterprises of purchasing reclaimed soil is greatly reduced, as soil reconstruction using substitute materials can save more than 50% of the available soil; for example, assuming a soil cover thickness of 30 cm, the total amount of soil needed is less than 1500 mThe study preliminarily analyzed the physical and hydrological characteristics of soil under different construction measures in experimental plots using iron tailings to replace soil for farmland construction and revealed that it was feasible to use iron ore waste materials such as iron tailings and waste rocks for soil and farmland construction enhancement. Since the experimental demonstration was only conducted for one year, the relevant experimental observation data are insufficient. In the future, it is necessary to establish long-term experimental monitoring campaigns, further study the influence of various factors on the soil structure, continue to optimize the best structural measures, improve the application effect of this technology, and promote its application accordingly.Iron tailings should be popularized and applied according to local conditions. At present, most iron tailings are used as fertilizer substrates, and their consumption is low. The use of iron tailings to improve barren soil and construct farmland prevents the problem of passive tailings pond reclamation due to the notable accumulation of mineral processing tailings in the past, which is a suitable method for resource utilization of iron tailings and can provide broad application prospects. However, due to the limitations of the obtained monitoring data and other aspects, this study only preliminarily verified the soil characteristics and effects of the application level of iron tailings in Jianping County, and more comprehensive research and analysis and evaluation studies should be conducted in the future. In addition, mining waste rock and soil fill pit and reclamation projects are underway, which can improve the entire iron ore waste agricultural resource utilization technique, forming a complete set of technical systems.Aiming at the problem of iron ore waste resource utilization and lack of soil for soil reconstruction, we proposed the technology of using a large amount of iron tailings to reconstruct reclaimed farmland soil. The experimental application of various treatments to newly reclaimed farmland revealed that iron tailings could be considered effective soil substitute materials to construct farmland and improve the soil texture and water content. Moreover, the maize growth in the experimental plots was normal, and the crop yields were close to or even higher than those in local normal farmland. Iron tailings could be recommended as a feasible and harmless material for farmland construction because of the advantages in improving the soil quality and crop yield.For relatively barren local topsoil layers, the application of a 5-cm mixed iron tailings-topsoil layer could effectively improve the textural characteristics of clayey soil in western Liaoning, increase the soil water capacity, and enhance soil moisture, atmosphere, and thermal conditions, which was conducive to maize growth and achieved the purpose of generating a high yield.Given the semiarid climatic conditions in western Liaoning, solid waste resulting from iron ore mining could be used as farmland construction material to establish a water-retaining layer below topsoil, and satisfactory results could be obtained. At the same time, the accumulated waste rocks, topsoil stripping materials, iron tailings, and other waste materials could be consumed, resulting in higher economic and ecological benefits, which represents a suitable way for agricultural resource utilization of iron ore waste materials.


Introduction: Nutritional counseling is relevant to physiatry practice. However, physiatrists’ nutrition knowledge base and their frequency of incorporating nutritional education into routine clinical encounters are currently unknown. The objective of this study was to assess physiatrists’ nutrition education, nutrition knowledge, willingness to implement nutrition counseling in clinical practice, and perceived barriers to providing nutritional counseling to patients, using an online survey. The hypothesis was that few physiatrists offer dietary counseling to their patients on a routine basis and that barriers likely include time constraints in a typical office visit, lack of provider confidence in providing dietary recommendations, and lack of provider reimbursement.Methods: This study was a cross-sectional online survey that was distributed via email to a convenience sample of 179 resident, fellow, and attending physiatrists associated with two major academic institutions. The survey consisted of 26 questions regarding demographics, nutrition counseling practices and attitudes, basic nutrition knowledge, and perceived barriers to providing nutrition counseling.Results: Of 59 participants, 78% reported receiving education in nutrition and/or behavioral counseling in medical school. In contrast, 39% of participants did not feel adequately trained to discuss nutrition and diet-related issues with patients. Barriers to providing nutritional counseling were time constraints (83%), socioeconomic factors outside of patients’ control preventing them from adhering to a healthier diet (76%), and not having enough nutrition knowledge to do so appropriately (62%). Respondents (86%) either agreed or strongly agreed that additional training in nutrition would allow them to provide better clinical care in the prevention of progressive cardiovascular and neurovascular disease. Further, respondents (85%) either agreed or strongly agreed that they would be interested in a web-based continuing medical education training in nutrition behavioral counseling and evidence-based dietary recommendations.Conclusions: The findings refuted the hypothesis that few physiatrists in the sample offer dietary counseling to their patients on a routine basis. Results demonstrated that many of them acknowledge its relevance and would be interested in further education on the subject. Physiatrists also appear to have perceived barriers to offering nutritional counseling, but some of them varied by the amount of medical experience. Based on these findings, this study demonstrated that it would be worthwhile to develop such a continuing medical education activity with a focus on populations commonly treated by physiatrists. The prevalence of conditions that increase cardiovascular risk such as type 2 diabetes mellitus and overweight/obesity has been increasing -5. The pWhile studies have generally examined nutrition education among physicians, nurse practitioners, and other healthcare professionals , little The purpose of this study was to assess physiatrists’ prior nutrition education, nutrition knowledge, willingness to implement nutrition counseling in clinical practice, and perceived barriers to providing nutritional counseling to patients. Based on previous research on other healthcare providers ,23, it wPhysiatry '22) on May 26, 2022. The abstract was subsequently published in the American Journal of Physical Medicine & Rehabilitation's July supplement containing the "Abstracts of Scientific Papers and Posters Presented at Physiatry ’22" .The preliminary results of this survey study were previously presented as a meeting abstract and poster at the 2022Association of Academic Physiatrists(AAP) Annual Meeting  residency programs in Philadelphia, PA.Study populationThe study population consisted of a convenience sample of resident, fellow, or attending physicians in PM&R. Those not currently practicing and prospective physiatrists in internship were excluded. Participants self-selected by responding to an email to complete the survey. This study was deemed exempt by the University of Pennsylvania Institutional Review Board. Survey toolThe survey consisted of 26 questions regarding demographics, nutrition counseling practices and attitudes, basic nutrition knowledge, and perceived barriers to providing nutrition counseling (see Appendixfor the administered survey). The estimated time to complete the questionnaire was no more than 15 minutes. The questionnaire was adapted from a previous survey study by Harkin et al. . The surSurvey measuresThe measures included the following four domains: demographics and clinical practice, nutrition counseling practices and attitudes, nutrition knowledge, and barriers to nutrition counseling. Demographics and Clinical PracticeDemographic and clinical practice variables including age, gender identity, stage of career, years in practice since training, practice environment, and foci of physiatry practice were collected.Nutrition Counseling Practices and AttitudesIn this domain, participants answered items describing settings in which they might have received prior nutrition education, incorporation of nutrition counseling in practice, attitudes about the relevance of nutrition to their practice, perceptions about their abilities to counsel patients on nutrition, perceptions about their effectiveness in helping patients improve their diet, perceived importance of various modifiable lifestyle factors, the proportion of time spent during a routine encounter providing diet and/or lifestyle counseling, the proportion of patients they refer to allied professionals to implement these changes, and attitudes about further nutrition education. One item queried diets routinely recommended to patients, and if a diet was not identified in the choices, participants could specify it in a subsequent open-ended item. The respondents' perceived importance of six separate modifiable lifestyle factors were answered in a 1-10 point Likert scale format within one item.Nutrition Knowledge This domain featured two multiple-choice items and one true/false item testing basic dietary knowledge.Barriers to Nutrition CounselingParticipants were presented with statements about potential barriers to providing nutrition counseling and were asked to respond using a Likert scale from 1 to 5  toward these statements.Statistical analysisStandard summary statistics such as frequencies and percentages, means with standard deviations (SD), or medians with interquartile range (IQR) were used to describe the data. To determine differences in the perceived importance of modifiable lifestyle factors and barriers to nutrition counseling, by years of practice , a one-way analysis of variance was performed. For barriers to counseling, the Likert scales were flipped for ease of comprehension, so that strongly disagree = 1 and strongly agree = 5. To adjust for multiple post-hoc pairwise comparisons, Tukey-Kramer tests were used. All analyses were performed using SAS statistical software .Participant demographicsOf the 179 physiatrists invited to participate in the study, 59 (33.0%) respondents completed all survey items. The median participant age was 35 years (IQR: 31-46.5) and 35 (59.3%) of the participants identified as male. Of the respondents, 52.5% were attending physicians, 37.3% were residents, and 10.2% were fellows. For practice experience, 28 (47.5%) respondents were still in training, 3 (5.1%) had fewer than five years, and 28  5-15 years, or greater than 15 years of experience. For the primary practice environment, 78.0% of respondents were within an academic medical center, 15.3% were in private practice, and 6.8% were in community hospital-based practice. The most common practice focus among respondents was general physiatry (62.7%), followed by brain injury medicine or stroke rehabilitation (32.2% each), interventional pain/spine rehabilitation (30.5%), spasticity management, and pain medicine or gait evaluation  reported having received education in nutrition and/or behavioral counseling in medical school; 3.4% reported not having had any of this education. While 84.7% of respondents felt discussing nutrition and diet-related issues with patients was relevant to their practice and 81.4% felt that they could be at least slightly effective in helping patients improve their diet, 39.0% of participants did not feel adequately trained to discuss nutrition and diet-related issues with patients. In response to the diet(s) recommended, the most common response was that they do not routinely recommend any specific diet(s) 42.4%). Of those who recommended diets, the Mediterranean diet (28.8%) was the most common, followed by a low-carbohydrate diet such as the Atkin's diet (16.9%), and intermittent fasting  reported that they spend approximately 1-10% of their visits counseling patients about diet and/or lifestyle interventions to prevent cardiovascular and neurovascular disease. None of the respondents reported spending more than 30% of their encounters on this.Among the modifiable lifestyle factors, the respondents ranked smoking cessation the highest importance based on a mean of 9.4 ± 1.2, followed by physical activity (8.6 ± 1.1), proper nutrition (8.5 ± 1.5), stress/mental health management (7.7 ± 1.4), adequate sleep (7.7 ± 1.6), and statin therapy (6.50 ± 1.8). Although statin therapy was ranked the least important, trainees were more likely to rank statin therapy higher in importance (mean of 7.1) compared to those practicing independently  training in nutrition behavioral counseling and evidence-based dietary recommendations.Basic nutrition knowledgeOf respondents, 84.7% knew that the Mediterranean diet was shown to reduce cardiovascular events in a randomized controlled trial . SimilarBarriers to nutrition counselingAll groups felt insufficient behavioral counseling skills, inadequate potential reimbursement, or socioeconomic factors outside of patients’ control were barriers to providing nutritional counseling. Those in practice longer were more likely to disagree with time, reimbursement, or knowledge being a barrier Figure . Those pThe purpose of this cross-sectional survey study was to characterize nutrition education, practices, attitudes, and perceived barriers to nutritional behavioral counseling among physiatrists. In contrast to the hypothesis, it was found that 93.2% of the physiatrists spend at least 1% of their time during a routine encounter counseling patients on diet and/or lifestyle changes. When asked to estimate the proportion of time spent doing this, however, the majority (72.9%) selected 1-10% of the encounter, while none selected 31-40% or greater. This is not entirely surprising, as patients receiving physiatric care have numerous complex needs, such as evaluation of adaptive equipment or gait, which require significant attention.Indeed, when given the opportunity to select diets routinely recommended in their clinical practice, 42.4% of respondents reported that they do not routinely recommend any specific diet(s). This result contrasts with a similar survey item administered by Harkin et al. to cardiologists and internists - only 16% of their respondents were in this category . These fInterestingly, none of the respondents disagreed with the statement “I feel that discussing nutrition and diet-related issues with patients is relevant to my practice,” but in response to whether respondents felt adequately trained to discuss these issues with patients, responses were relatively discordant, mostly distributed among selections of “agree,” “neutral,” and “disagree.” Even though only 35.6% agreed or strongly agreed with this statement, this is still more than double the number of internists and cardiologists who responded this way to the analogous item in Harkin et al., which was 13.5% .In terms of perceived effectiveness in helping patients improve diet, almost half of the respondents (49.2%) felt they could be slightly effective, with the other half of responses among “very effective,” “effective,” and “not very effective.” This may indicate that there is a mismatch between physiatrists’ perception of nutrition relevance to their practice and their perception of their ability to use it to help patients make lifestyle improvements. This study demonstrates that a considerable number of physiatrists (39.0%) do not feel adequately trained to discuss nutrition and diet-related issues with patients, similar to many cardiologists and internists as shown by Harkin’s survey .It should be noted that an overwhelming majority (86.5%) of the respondents either agreed or strongly agreed with the statement “additional training in nutrition would allow me to provide better clinical care in the prevention of cardiovascular/neurovascular disease.” Similarly, 84.8% agreed or strongly agreed with the statement “I would be interested in a web-based CME training in nutrition behavioral counseling and evidence-based dietary recommendations.”The respondents’ performance on the nutrition knowledge questions shows that most of the respondents already have at least some basic familiarity with the subject, as >70% of the respondents answered 3/3 questions correctly. These questions may serve as a starting point in the development of potential nutrition CME with a physiatrist target audience. Physiatrists would greatly benefit from CME specifically designed for their specialty due to the diverse and medically complex populations they serve. Regarding ranking the importance of the modifiable lifestyle factors, the highest three ranked lifestyle factors  may be reflective of the ones most often addressed by this group. Indeed, these factors did not significantly differ in rank based on respondents’ time practicing physiatry. A secondary objective of this study was to assess duration in physiatric practice as a factor in lifestyle counseling. Several differences were found in the perceived importance of various modifiable lifestyle factors by duration in practice. The more seasoned physiatrists tended to rank stress/mental health management and adequate sleep higher than those with <15 years in practice. It is unclear why more experienced physicians recognize these factors as more important than their less experienced counterparts; perhaps it reflects their experience with patients, themselves, or both. The in-training physiatrists tended to rank statin therapy as more important than those with more experience did. A potential explanation could be trainees’ knowledge of recent evidence of statin use’s association with decreased risk of all-cause and cardiovascular mortality in a large retrospective cohort study in US veterans 75 years and older . PerhapsThe most common barriers to offering dietary counseling in this study include time constraints in a typical office visit (endorsed by 84.5% of the sample), socioeconomic factors outside of patients’ control preventing them from adhering to a healthier diet (endorsed by 77.5% of the sample), and lack of provider confidence in providing dietary recommendations (endorsed by 62.1% of the sample). Some differences in perceived barriers to practicing nutritional behavioral counseling were identified by the duration of physiatric practice. The physiatrists in practice with <15 years were more likely to agree with time constraints as a barrier to providing nutritional counseling to patients, while those with >15 years’ experience tended to disagree with time constraints as a barrier. A survey administered to primary care providers by Kushner revealed that lack of time was the top perceived barrier by its respondents, perhaps because there are often a variety of topics to cover in this setting, such as tracking age-appropriate screenings and vaccinations, in addition to a patient’s individual medical problems . The phyStudy limitationsThis study had a number of limitations. First, the study population was a convenience sample, as the prospective participants were associated with either of two PM&R training programs in the same city. Further, given that the participants were associated with urban PM&R training programs in one city, the study population is likely not reflective of the physiatrist population in the US. Finally, the sample size is small. There were 66 individuals who gave consent and proceeded with the questionnaire, but 59 completed it in full. Although this may appear as a study weakness, the authors felt that allowing some questionnaire items to be optional would reduce respondent fatigue and maximize participation.This study refuted the hypothesis that few physiatrists in the sample offer dietary counseling to their patients on a routine basis. It was discovered that many of them acknowledge its relevance in their specialty and would be interested in further education on the subject. Physiatrists also appear to have perceived barriers to offering nutritional counseling, but some of them varied by the amount of medical experience, including time constraints, lack of nutrition knowledge, and socioeconomic factors outside of patients’ control. Future research should include developing a CME program on nutrition and its related behavioral counseling, with physiatrists both in training and practice as the target audience, followed by an analysis of the educational activity for effectiveness in practice.


Microbial contaminations are responsible for many chronic, healthcare, persistent microbial infections and illnesses in the food sector, therefore their control is an important public health challenge. Over the past few years, essential oils (EOs) have emerged as interesting alternatives to synthetic antimicrobials as they are biodegradable, extracted from natural sources and potent antimicrobials. Through their multiple mechanisms of actions and target sites, no microbial resistance has been developed against them till present. Although extensive documentation has been reported on the antimicrobial activity of EOs, comparisons between the use of whole EOs or their active components alone for an antimicrobial treatment are less abundant. It is also essential to have a good knowledge about EOs to be used as alternatives to the conventional antimicrobial products such as chemical disinfectants. Moreover, it is important to focus not only on planktonic vegetative microorganisms, but to study also the effect on more resistant forms like spores and biofilms. The present article reviews the current knowledge on the mechanisms of antimicrobial activities of EOs and their active components on microorganisms in different forms. Additionally, in this review, the ultimate advantages of encapsulating EOs or combining them with other hurdles for enhanced antimicrobial treatments are discussed. Essential oils; Antimicrobial activity; Encapsulation; Hurdle technology; Disinfection. These contaminations and their subsequent consequences result in an increase of occurrence of food-borne diseases, outbreaks, reduced shelf-life of food products, costly socio-economical losses, along with healthcare-associated infections. The centers for disease control (CDC) estimates that annually, around 48 million Americans suffer from foodborne illnesses resulting in 3000 deaths and 128,000 hospitalizations . The EurSeveral synthetic antimicrobials and control measures have been adopted to overcome microbial contaminations. Nevertheless, due to the recent negative perception of consumers towards synthetic antimicrobials, the resistance developed by certain microorganisms towards them, their possible side toxic effects along with their low biodegradability and negative environmental impacts, increased efforts are urgently needed to find some new effective control measures to limit microbial contaminations .Salmonella spp., Staphylococcus aureus, Candida sp., Listeria monocytogenes., Escherichia coli, Klebsiella sp., Proteus sp., and Pseudomonas aeruginosa  and their active components have received remarkable attention and emerged as vigorous and convenient natural alternatives for synthetic antimicrobials. For many years, EOs have been used in therapies, pharmaceuticals, perfumes, cosmetics and in food industries. They are environmental-friendly, biodegradable into non-toxic products with potent antimicrobial activity against different types of microbial contaminations . Additioruginosa . EOs werruginosa . Thereforuginosa . Anotherruginosa .This review provides an overview of the published data and current knowledge on EOs and their active components as potent antimicrobial tools used to fight different forms of microbial contaminations along with their mechanisms of action. Moreover, this review highlights the strategies used to improve EOs antimicrobial activity by micro- and nano-encapsulation and by their combination with other hurdles.2In this review, the specialized databases Scopus, ScienceDirect, PubMed and Web of Science were used for the literature search using different combinations of the following keywords: essential oils, antimicrobial, hurdle technology, and encapsulation.2.1Vegetative cells are the most common form of microbial contaminations that are easily detectable and generally inhibited by conventional treatments. Under harsh and stressful conditions as temperature, osmotic stress, desiccation and/or regular cleaning and disinfection procedures, some vegetative cells may adapt by implementing physiological, structural and/or molecular mechanisms making them more resistant . Sporula2.2E. coli, E. coli O 157:H7, L. monocytogenes, S. aureus, H. pylori, P. aeruginosa, Salmonella spp., Enterococcus faecalis, Yersinia, Bacillus coagulans, Micrococcus luteus, Lactobacillus brevis and Vibrio spp.  and have become up to 1000 fold more resistant than their planktonic microbial cells . BiofilmS. aureus dry biofilms have shown higher heat resistance than wet biofilms and planktonic cells with a reduction of 2, 7 and 8 logs, respectively  and others in trace amounts . The che5H8) n where “n” represents the number of isoprene units (5-carbon blocks) (10H16), sesquiterpenes (C15H24), diterpenes (C20H32) and triterpenes (C30H40)  constitute 90% of EOs composition but have shown no remarkable antimicrobial activity when used alone as they have a benzene ring with no functional groups on their side chains  . Dependi(C30H40) . Monotere chains .The biochemical modifications of terpenes by adding oxygen molecules, and removing or moving methyl groups via enzymes results in the formation of terpenoids  . TerpenoSome EOs contain other oxygenated molecules known as phenylpropanoids . They arThe greatest antimicrobial activity was reported for phenolic compounds mainly carvacrol, thymol and eugenol . This is3.2The activity of EOs and their active components has been reported against several types of bacteria, yeasts, molds and was found to be related to EOs chemical composition and structure, in addition to the type and structure of targeted microorganisms .Against yeasts and molds, EOs were found to disrupt their membranes and damage their endomembrane system . AdditioAcinetobacter baumannii and Vibrio parahaemolyticus were the most sensitive microorganisms to Eucalyptus camaldulensis EO , E. coli and B. subtilis to Amomum villosum Lour and Origanum compactum EOs induced a leakage of macromolecular molecules such as DNA, RNA and proteins  carvacrol induced significant production of heat shock proteins 60  and inhibited significantly the synthesis of flagella  in L. monocytogenes biofilms  signaling and to prevent cell division and thus lead to cell death without causing a damage to bacterial cell membranes . EOs andbiofilms . Cinnamabiofilms . Also, abiofilms .3.3Several free EOs and their active components have been screened for their potent antimicrobial activity against a broad range of microorganisms. They were reported to induce significant reductions or inhibitions of microbial contaminations , as wellCymbopogon nardus and cinnamon compared to that of their major components used alone  planktonic and sessile microorganisms of L. monocytogenes, E. coli, S. enterica and H. pylori, respectively  in Aeromonas spp. and Enterococcus spp., Salmonella and E. coli  S. aureus LPMA63 biofilms were detected on stainless steel after 15 min exposure to EOs active components oregano (10 μl/ml) and carvacrol (5 μl/ml), whereas 15 min exposure to 250 mg/L of a synthetic antimicrobial (sodium hypochlorite) was ineffective to eliminate biofilms and induced approximately 3.5 log CFU/cm2 reductions because of its limited diffusion  and L. monocytogenes when compared to commercial synthetic sanitizers such as alkyl dimethyl benzyl ammonium chloride (ADBAC), sodium hypochlorite and hydrogen peroxide  (L. monocytogenes harboring quaternary ammonium compounds (QACs) resistance genes (qacH and bcrABC) were found to be prevalent in food processing environments  . In anotronments . Severalle cells . Synthetbiofilms . Also, Land QACs . C. perfperoxide . QACs webiofilms .Additionally, a potential risk of exposure to QAC disinfectants was reported as they are discharged from several sources and eventually reach freshwater and marine environments, soils, sediments and wastewater systems . DespiteDue to these limitations and side effects of the conventional synthetic antimicrobial agents, the interest in biosourced antimicrobials as natural alternatives has increased remarkably. EOs are being favored as no particular resistance have been developed against them as they are composed of different active components, have multiple targets in bacterial cells and subsequently multiple modes of antimicrobial activity . Additio44.1Several strategies have been adopted to encounter the different limitations and improve the antimicrobial activity of free EOs including the development of new delivery systems as micro- and nano-capsules. The different encapsulation systems entrapping EOs were able to reduce or to eliminate microorganisms in different states as vegetative , and bioThe enhanced antimicrobial activity of the encapsulated EOs against the different types of microbial contaminations could be mainly linked to the reduced size of the particles and their increase in surface to volume ratio, which facilitates the diffusion of EOs into microbial cells . Also, t4.1.1Carum copticum EO enhanced its antimicrobial activity against S. epidermidis, S. aureus, B. cereus, E. coli, S. Typhimurium and P. vulgaris , synergism was reported on the reduction and/or elimination of formulas .Another promising intervention involves the combination of EOs with VP and MAP, which has been assessed for the packaging of different food products. Combination of EOs with VP and/or MAP showed a synergistic effect with an enhanced reduction of spoilage and/or pathogenic bacteria in marinated chicken samples , in paprAcinetobacter baumannii when coriander EO was combined with Cefoperazone and Piperacillin antibiotics , EOs showed remarkable synergistic effects against dermidis .The combination of an optimized mixture of EOs with other hurdles showing synergistic effect may reduce the concentrations required to yield the same antimicrobial activity when compared to EOs used alone. This may result in lower economic costs and lower sensorial impacts on food products, while maintaining their microbiological safety . Also, c5In this review, the advances and major trends in the use of EOs as potent tools to fight microbial contaminations were addressed. Additionally, the functional role and mechanisms of action of the different active EO components were discussed. Among the different active EO components, phenolic compounds were found to exhibit the greatest antimicrobial activity by acting principally on the disruption and increase in permeability of cell membranes, inducing a leakage of vital intracellular contents and eventually leading to microorganisms' inactivation and death. In most studies, the antimicrobial activity of active compounds was more pronounced than that of whole EOs, thus minimizing the amounts of EOs being used while achieving more reproducibility and standardization. EOs and their active components were effectively used in their free, micro- and nano-encapsulated forms and combined with other hurdles for antimicrobial purposes. Generally, encapsulation of EOs and their combination with other hurdles provided an enhanced antimicrobial activity when compared to free EO applications, with lower amounts being used. This could be promising technologies to control the different types of microbial contaminations and achieve microbiological safety. Further research studies should explore: i) the antimicrobial mode of action of EOs combined with other hurdles as one strategy could promote or modify the action of the other; ii) the combination of encapsulated EOs with other hurdles to determine their potential antimicrobial efficiencies as it is expected to have a synergistic or additive effect; and iii) the impact of the strong odor of EOs on the sensorial properties of food products. Additional studies should also assess the activities of EOs encapsulated or combined with other hurdles against microorganisms in different states as biofilms, viable but not culturable cells, spores and molds. Moreover, robust national and international frameworks and regulations should be set towards the use of EOs and their active components before being applied in diverse applications and fields.All authors listed have significantly contributed to the development and the writing of this article.Qatar National Library.This work was supported by the Partenariat Hubert Curien (PHC)- Cèdre program [42281SD] and the open access funding was provided by the No data was used for the research described in the article.The authors declare no competing interests.No additional information is available for this paper.