کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6332768 | 1619798 | 2013 | 8 صفحه PDF | دانلود رایگان |
- Nitrate concentration in water displayed significant temporal variation in a subtropical watershed.
- Chemical and isotopic characteristics were combined for nitrate source identification.
- Bayesian model stable isotope analysis in R (SIAR) was used for nitrate source apportionment.
- The merits and uncertainties of SIAR were discussed.
Nitrate (NO3â) pollution in aquatic system is a worldwide problem. The temporal distribution pattern and sources of nitrate are of great concern for water quality. The nitrogen (N) cycling processes in a subtropical watershed located in Changxing County, Zhejiang Province, China were greatly influenced by the temporal variations of precipitation and temperature during the study period (September 2011 to July 2012). The highest NO3â concentration in water was in May (wet season, mean ± SD = 17.45 ± 9.50 mg Lâ 1) and the lowest concentration occurred in December (dry season, mean ± SD = 10.54 ± 6.28 mg Lâ 1). Nevertheless, no water sample in the study area exceeds the WHO drinking water limit of 50 mg Lâ 1 NO3â. Four sources of NO3â (atmospheric deposition, AD; soil N, SN; synthetic fertilizer, SF; manure & sewage, M&S) were identified using both hydrochemical characteristics [Clâ, NO3â, HCO3â, SO42 â, Ca2 +, K+, Mg2 +, Na+, dissolved oxygen (DO)] and dual isotope approach (δ15N-NO3â and δ18O-NO3â). Both chemical and isotopic characteristics indicated that denitrification was not the main N cycling process in the study area. Using a Bayesian model (stable isotope analysis in R, SIAR), the contribution of each source was apportioned. Source apportionment results showed that source contributions differed significantly between the dry and wet season, AD and M&S contributed more in December than in May. In contrast, SN and SF contributed more NO3â to water in May than that in December. M&S and SF were the major contributors in December and May, respectively. Moreover, the shortcomings and uncertainties of SIAR were discussed to provide implications for future works. With the assessment of temporal variation and sources of NO3â, better agricultural management practices and sewage disposal programs can be implemented to sustain water quality in subtropical watersheds.
Journal: Science of The Total Environment - Volumes 463â464, 1 October 2013, Pages 340-347