Tracing the Nitrate Sources of the Yili River in the Taihu Lake Watershed: A Dual Isotope Approach

Abstract

Abstract:As the third largest freshwater lake in China, Taihu Lake has experienced severe cyanobacterial blooms and associated water quality degradation in recent decades, threatening the human health and sustainable development of cities in the watershed. The Yili River is a main river of Taihu Lake, contributing about 30% of the total nitrogen load entering the lake. Tracing the nitrate sources of Yili River can inform the origin of eutrophication in Taihu Lake and provide hints for effective control measures. This paper explored the nitrate sources and cycling of the Yili River based on dual nitrogen (δ

Using Dual Isotopes and a Bayesian Isotope Mixing Model to Evaluate Nitrate Sources of Surface Water in a Drinking Water Source Watershed, East China

“…A dual isotope bi-plot approach (δ 15 N-NO3 − and δ 18 O-NO3 − ) is adopted to qualitatively identify predominant NO3 − sources for surface water in different periods [4]. The ranges of δ 15 N-NO3 − and δ 18 O-NO3 − in precipitation were from −10.9‰ to 6.8‰ and from 49.8‰ to 70.2‰, respectively.…”

“…During nitrification process (NH 4 + oxidized to NO 3 − ), it has revealed that there exists considerable .4‰, which were calculated using δ 18 O in precipitation and surface water in the study area. Therefore, the range of δ 18 O derived from nitrification of NH 4 + was from −3.3‰ to +10.78‰, which was close to (but a little narrower than) the values found in other studies (−5‰-+15‰) [43,44].…”

“…In this study, the end member isotopic signatures of M & S, NF, NFA, and NS were based on other relevant studies (rather than measured directly in this study). In addition, sources from manure and sewage, as well as nitrate derived from NH 4 + fertilizer and rainfall, were difficult to distinguish. Moreover, the posterior distributions of the output have a large range, and dynamic varieties of nitrate source contributions at finer time scales should be further studied.…”

“…Furthermore, excess nitrate in drinking water is regarded as a health hazard as it is linked to infant methemoglobinemia and esophageal cancer [2]. Therefore, the World Health Organization (WHO), the United States Environmental Protection Agency, and the Ministry of Environmental Protection of China have set NO 3 − -N concentration of 10 mg/L (measured as nitrogen) as the upper limit for drinking water [3][4][5]. Nitrate contamination has increasingly become an environmental proportions of nitrate from different sources when there are more than three sources, and the temporal and spatial variability of δ 15 N-NO 3 − and δ 18 O-NO 3 − in sources is not incorporated [18].…”

Tracing Nitrate-Nitrogen Sources and Modifications in a Stream Impacted by Various Land Uses, South Portugal

“…In water studies, chloride is generally used as a conservative tracer of mixing within the streams, as it is an effective indicator of sewage and dilution effects which has minimal affects from physical, chemical and biological processes [52]. Hence, the ratio of NO 3 -N/Cl − was also considered for the study of N dynamics and sources.…”