| Object:To explore the spatial distribution,migration and transformation process and sources proportion of nitrate in surface water and groundwater in Manas River Basin(MRB)oasis.Methods:This thesis selects MRB oasis as the target research area,the sampling sites adopt grid method.The surface water samples including 9 Manas River points,10 points from Xi'an Canal,16 other points from canals and reservoirs and 21 points from groundwater.Samples were collected during July 20 th to August 10 th each year during 2015 to 2017.The spatial distribution of nitrate in surface-and groundwater was analyzed by Arc GIS software.The sources of nitrate were analyzed by dual stable environmental isotopes with revealed typical range of potential nitrate sources.The SIAR model was applied to quantify the proportion of nitrate sources.The nitrate control proposal of MRB oasis were given according to the research results and the survey data.Results:The concentration of nitrate was only exceeded in groundwater in 2015.The range of each ion concentration in Xi'an Canal is greater than Manas River.The mean concentration of ions in Xi'an Canal is higher than Manas River except nitrate.The ions in groundwater are strongly variable.The nitrates in the surface water are contributed by soil nitrogen(48.33%),sewage(4.09%),fertilizer(44.89%),atmospheric deposition(1.57%)and ammonia fertilizer(1.11%).The nitrates in the groundwater are contributed by soil nitrogen(32.68%),sewage(30.50%),fertilizer(24.54%),atmospheric deposition(3.19%)and ammonia fertilizer(9.09%).Conclusion:Surface water and groundwater in MRB oasis mainly affected by anthropogenic activities.Mixing process is the main process in surface water while the denitrification process only existed in groundwater.The main sources of nitrate in surface water are soil nitrogen and nitrate fertilizer,the main sources of nitrate in groundwater are soil nitrogen,nitrate fertilizer and manure and sewage. |
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