Legacy of contaminant N sources to the NO3− signature in rivers: a combined isotopic (δ15N-NO3−, δ18O-NO3−, δ11B) and microbiological investigation
نویسندگان
چکیده
Nitrate content of surface waters results from complex mixing of multiple sources, whose signatures can be modified through N reactions occurring within the different compartments of the whole catchment. Despite this complexity, the determination of nitrate origin is the first and crucial step for water resource preservation. Here, for the first time, we combined at the catchment scale stable isotopic tracers (δ15N and δ18O of nitrate and δ11B) and fecal indicators to trace nitrate sources and pathways to the stream. We tested this approach on two rivers in an agricultural region of SW France. Boron isotopic ratios evidenced inflow from anthropogenic waters, microbiological markers revealed organic contaminations from both human and animal wastes. Nitrate δ15N and δ18O traced inputs from the surface leaching during high flow events and from the subsurface drainage in base flow regime. They also showed that denitrification occurred within the soils before reaching the rivers. Furthermore, this study highlighted the determinant role of the soil compartment in nitrate formation and recycling with important spatial heterogeneity and temporal variability.
منابع مشابه
Tracing the Nitrate Sources of the Yili River in the Taihu Lake Watershed: A Dual Isotope Approach
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 Yil...
متن کاملIsotopic overprinting of nitrification on denitrification as a ubiquitous and unifying feature of environmental nitrogen cycling.
Natural abundance nitrogen and oxygen isotopes of nitrate (δ15NNO3 and δ18ONO3) provide an important tool for evaluating sources and transformations of natural and contaminant nitrate (NO3-) in the environment. Nevertheless, conventional interpretations of NO3- isotope distributions appear at odds with patterns emerging from studies of nitrifying and denitrifying bacterial cultures. To resolve ...
متن کاملNitrate Pollution and Preliminary Source Identification of Surface Water in a Semi-Arid River Basin, Using Isotopic and Hydrochemical Approaches
Nitrate contamination in rivers has raised widespread concern in the world, particularly in arid/semi-arid river basins lacking qualified water. Understanding the nitrate pollution levels and sources is critical to control the nitrogen input and promote a more sustainable water management in those basins. Water samples were collected from a typical semi-arid river basin, the Weihe River watersh...
متن کاملEvaluation of nitrogen isotopes as indicators of nitrate contamination sources in an agricultural watershed
Determining the relative contributions of nitrate contamination in agricultural watersheds characterized by applications of both mineral and animal waste nitrogen to fields is important in evaluating the environmental consequences of these practices. Here, the use of nitrate–nitrogen (NO3−–N) stable isotopes to identify contaminant sources was examined in surface waters of an agricultural water...
متن کاملSources and transport of nitrogen in arid urban watersheds.
Urban watersheds are often sources of nitrogen (N) to downstream systems, contributing to poor water quality. However, it is unknown which components (e.g., land cover and stormwater infrastructure type) of urban watersheds contribute to N export and which may be sites of retention. In this study we investigated which watershed characteristics control N sourcing, biogeochemical processing of ni...
متن کامل