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

Water ◽  
2014 ◽  
Vol 7 (12) ◽  
pp. 188-201 ◽  
Author(s):  
Haiao Zeng ◽  
Jinglu Wu
Keyword(s):  
Taihu Lake ◽  
Nitrate Sources ◽  
Dual Isotope

scholarly journals Stable Isotopes of Water and Nitrate for the Identification of Groundwater Flowpaths: A Review

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 138 ◽  
Author(s):  
Hyejung Jung ◽  
Dong-Chan Koh ◽  
Yun Kim ◽  
Sung-Wook Jeen ◽  
Jeonghoon Lee
Keyword(s):  
Stream Water ◽  
Isotope Analysis ◽  
Nitrate Contamination ◽  
Hydrograph Separation ◽  
Nitrate Sources ◽  
Dual Isotope ◽  
Contaminant Sources ◽  
The Difference ◽  
Stable Isotopes Of Water ◽  
Groundwater Flowpaths

Nitrate contamination in stream water and groundwater is a serious environmental problem that arises in areas of high agricultural activities or high population density. It is therefore important to identify the source and flowpath of nitrate in water bodies. In recent decades, the dual isotope analysis (δ15N and δ18O) of nitrate has been widely applied to track contamination sources by taking advantage of the difference in nitrogen and oxygen isotope ratios for different sources. However, transformation processes of nitrogen compounds can change the isotopic composition of nitrate due to the various redox processes in the environment, which often makes it difficult to identify contaminant sources. To compensate for this, the stable water isotope of the H2O itself can be used to interpret the complex hydrological and hydrochemical processes for the movement of nitrate contaminants. Therefore, the present study aims at understanding the fundamental background of stable water and nitrate isotope analysis, including isotope fractionation, analytical methods such as nitrate concentration from samples, instrumentation, and the typical ranges of δ15N and δ18O from various nitrate sources. In addition, we discuss hydrograph separation using the oxygen and hydrogen isotopes of water in combination with the nitrogen and oxygen isotopes of nitrate to understand the relative contributions of precipitation and groundwater to stream water. This study will assist in understanding the groundwater flowpaths as well as tracking the sources of nitrate contamination using the stable isotope analysis in combination with nitrate and water.

scholarly journals Nitrogen Cycle Dynamics Revealed Through δ18O-NO3− Analysis in California Groundwater

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 95
Author(s):  
Nate Veale ◽  
Ate Visser ◽  
Bradley Esser ◽  
Michael Singleton ◽  
Jean Moran
Keyword(s):  
United States ◽  
Land Use ◽  
Oxygen Isotope ◽  
Nitrogen Cycle ◽  
The United States ◽  
Nitrate Contamination ◽  
Nitrate Sources ◽  
Oxygen Isotope Fractionation ◽  
Dual Isotope ◽  
Quality Issue

Nitrate is a significant water-quality issue in California, the United States as a whole, and the world. Critical to addressing nitrate contamination is understanding the presence and extent of denitrification, and further refining the techniques used to identify nitrate sources. The use and understanding of nitrate isotopic signatures to identify nitrate sources have advanced tremendously; however, knowledge gaps remain concerning specific fractionation pathways and the role of denitrification in altering source values. Using a large unique database of California groundwater nitrate isotopic compositions, we explored the utility of nitrate–oxygen isotope ratios in determining specific nitrate origins. Lawrence Livermore National Lab (LLNL) samples were supplemented by United States Geological Society (USGS) data to create a dataset of over 1200 dual-isotope results. Methods used at LLNL allowed for the determination of δ15N-NO3−, δ18O-NO3−, δ18O-H2O, δ2H-H2O, excess air, major dissolved gases, and excess N2. Results were examined for the degree to which δ18O-NO3− conforms to the model of nitrification in which two atoms of oxygen are sourced from ambient water and one from the atmosphere. Almost 80% of the results fall within one standard deviation of predicted values. However, 19% of samples had significantly higher values, suggesting the preservation of a synthetic nitrate source signature, mixing of sources, or widespread denitrification. Results were examined with respect to general land-use classifications and, while nitrate concentrations followed the expected pattern of being higher in agricultural settings, δ18O-NO3−patterns are complicated by application of N-fertilizer in various forms, and subsequent N cycling in the soil zone. We found that the current understanding of oxygen isotope-fractionation mechanisms cannot yet explain the prevalence of oxygen-isotope compositions with higher than predicted δ18O values, but when paired with related data such as land use and indicators of denitrification, oxygen-isotope compositions of nitrate can help to assess nitrogen cycle dynamics.

Identification of nitrate sources in Taihu Lake and its major inflow rivers in China, using δ15N-NO3− and δ18O-NO3− values

2012 ◽  
Vol 66 (3) ◽  
pp. 536-542 ◽  
Author(s):  
Zi-Xiang Chen ◽  
Guang Liu ◽  
Wei-Guo Liu ◽  
Michael H. W. Lam ◽  
Gui-Jian Liu ◽  
...  
Keyword(s):  
Atmospheric Deposition ◽  
Water Samples ◽  
Wet Deposition ◽  
Taihu Lake ◽  
Dilution Effect ◽  
Spatial Variations ◽  
Organic N ◽  
Nitrate Sources ◽  
Temporal And Spatial Variations ◽  
Temporal And Spatial

In the present study, δ15N and δ18O-NO3− values, as well as concentrations of some major ion tracers were determined in seasonal water samples from Taihu Lake and major watersheds to investigate the temporal and spatial variations of nitrate sources and assess the underlying nitrogen (N) biogeochemistry process. The results lead to the conclusion that the nitrate concentrations in Taihu Lake are lower in summer than that in winter due to the dilution effect of wet deposition. In winter, sewage and manure were the primary nitrate sources in major inflow rivers and North Taihu Lake (NTL), while nitrate sources in East Taihu Lake (ETL) probably derived from soil organic N. In summer, atmospheric deposition and sewage/manure inputs appear to play an important role in controlling the distribution of nitrates in the whole lake. The δ18O-NO3− values suggest that the nitrate produced from microbial nitrification is another major nitrate source during both winter and summer months. The variations in isotopic values in nitrate suggest denitrification enriched the heavier isotopes of nitrate in NTL in winter and in ETL in summer.

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