Variation in nitrate isotopic signatures in sewage for source apportionment with urbanization: a case study in Beijing, China.
Nitrate (NO3-) pollution is a severe problem in urban aquatic systems especially within megacity undergoing rapid urbanization, and mostly, sewage is supposed as the prevailing NO3- source. A dual isotope approach (δ 15N-NO3- and δ 18O-NO3-) was applied to explore the variation in NO3- isotopic signatures in sewage processed by wastewater treatment plants (WWTPs) in Beijing from 2014 to 2015. We found that the raw and treated sewage owned the different NO3- isotopic signatures, including δ 15N from 1.1 to 24.7 ‰ and δ 18O from 1.6 to 22.8 ‰ in raw sewage, as well as δ 15N from 6.1 to 22.8 ‰ and δ 18O from 1.6 to 13.2 ‰ in treated effluents. The WWTP processing would result in the enrichment of NO3- isotopic compositions in discharged effluents with NO3- concentrations increasing. Besides, advanced sewage treatment technology with more pollutant N reduction may raise the heavier NO3- isotopic compositions further. The NO3- isotope value ranges of urban sewage and manure should be separated, and the seasonal and tighter NO3- isotope value ranges are supposed to improve the accuracy of source apportionment. The NO3- isotope value ranges conducted in this study might provide useful information for tracing NO3- sources towards the implementation of efficient water pollution control in Beijing.
['Xian|Chaofan|C|', 'Ouyang|Zhiyun|Z|', 'Li|Yanmin|Y|', 'Xiao|Yang|Y|', 'Ren|Yufen|Y|']
D000068476:Beijing D004784:Environmental Monitoring D008372:Manure D009566:Nitrates D009587:Nitrogen Isotopes D045483:Rivers D012621:Seasons D012722:Sewage D014507:Urbanization D062065:Waste Water D014874:Water Pollutants, Chemical
Nitrate Source apportionment Beijing Dual isotope Sewage treatment