Tracing the sources of nitrate in the rivers and lakes of the southern areas of the Tibetan Plateau using dual nitrate isotopes

Hu, Mingming; Wang, Yuchun; Du, Pengfei; Shui, Yong; Cai, Aimin; Lv, Cong; Bao, Yufei; Li, Yanhui; Li, Shanze; Zhang, Panwei

doi:10.1016/j.scitotenv.2018.12.149

Cited by 61 publications

(22 citation statements)

References 44 publications

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“…The δ 18 O values (2.5‰ and −1.0‰) (Table 1) are similar to the estimated δ 18 O value in nonatmospheric nitrate in the hydrological system of the Mt. Everest region (Figure 4) and previous observations in the Southern TP at Yalu Tsangpo River (Hu et al, 2019). The isotopic similarity indicates that the source of nonatmospheric nitrate at this site is likely nitrification of soil organic nitrogen (Hu et al, 2019).…”

Section: Resultssupporting

confidence: 87%

“…Although the TP is one of the most remote regions in the Eurasian continent, many studies have shown that air pollutants emitted from South Asia have caused significant impacts on environmental and climatic changes over this region (see a recent review by Kang et al, 2019). As a major component of anthropogenic pollution and nitrogen nutrients, nitrate in snow, ice, and runoff water over the TP plays an important role in hydrological ecosystems over not only the TP but also Asia (Hu et al, 2019;Xia et al, 2019). In addition, the TP is the world's highest (mean altitude > 4 km) and largest (area > 2.5 × 10 6 km 2 ) plateau, and it strongly influences the Asian monsoon and global atmospheric circulation patterns through dynamical and thermal effects (An et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

“…− concentration, and their interpretations possess uncertainties due to multiple sources and complex chemical transformation mechanisms for NO 3 − (Kang et al, 2000(Kang et al, , 2004Wake et al, 1994;Zhang et al, 2016). Recent nitrate studies have benefitted from the developments of nitrate isotopic analytical techniques, and isotopic investigations on the fate of atmospherically deposited nitrate over the TP have been reported (Hu et al, 2019;Li et al, 2020;Xia et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Complete Isotope (δ¹⁵N, δ¹⁸O, Δ¹⁷O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region

et al. 2020

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The Himalayas and Tibetan Plateau, identified as the Third Pole (TP), is a unique region because of its insertion into global environmental and climatic changes. Deposition of atmospheric nitrate in this region is one of the most important sources of reactive nitrogen to glacial-hydrologic system and ecosystems. The isotopic composition of atmospherically deposited nitrate preserved in ice bodies plays a central role in delineating environmental and climatic changes, present, and past. Here, we provide an overview of the complete isotopic compositions (δ 15 N, δ 18 O, and Δ 17 O) of nitrate in aerosol, snow, ice, and water samples (n = 46) collected across the Southern, Southeastern, Central, and Northern TP to constrain complex nitrogen cycles of the atmosphere, cryosphere, hydrosphere, and, potentially, the biosphere. A large variability of snow nitrate isotopic compositions is observed across the TP at different spatial scales (from a single glacier to the entire plateau), likely due to the complex landscape and relevant physical and chemical processes across the TP. Large nitrate Δ 17 O values are observed in water samples collected from the Mt. Everest region, highlighting the considerable fraction (up to 45%) of atmospheric nitrate to the nitrate load in this Himalayan hydrologic system. Our work reveals the complex chemical, depositional, and postdepositional processes over the TP that are greater than previously thought and identifies further comprehensive investigations, which entail using nitrate isotopic compositions as an identifier for nitrate source apportionment in various ecosystems and understanding past atmospheric and climatic conditions in this region. The Himalayas and Tibetan Plateau hosts the largest number of glaciers (>36,000) on the planet outside of polar regions with thousands of lakes and is referred to as the Third Pole (TP) (Yao et al., 2012). This massive water reservoir within this pristine region sustains the water supply and food security for billions of people in ©2020. American Geophysical Union. All Rights Reserved.

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Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Complete Isotope (δ¹⁵N, δ¹⁸O, Δ¹⁷O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region

et al. 2020

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“…Measuring the isotopic composition in nitrate (δ 15 N/δ 18 O-NO 3 ) provides important information on nitrate sources and potential transformations (Fadhullah et al, 2020;Hu et al, 2019;Kendall and McDonnell, 1998;Xue et al, 2009). Merits of the isotope-based approach include less ancillary information requirements, high precision, and direct identification of pollution sources.…”

Section: Introductionmentioning

confidence: 99%

A support vector regression model to predict nitrate-nitrogen isotopic composition using hydro-chemical variables

Yang

Shang

Chen

et al. 2021

Journal of Environmental Management

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Nitrate is a prominent pollutant in surface and groundwater bodies worldwide. Isotopes in nitrate provide a powerful approach for tracing nitrate sources and transformations in waters. Given that analytical techniques for determining isotopic compositions are generally time-consuming, laborious and expensive, alternative methods are warranted to supplement and enhance existing approaches. Hence, we developed a support vector regression (SVR) model and explored its feasibility to predict nitrogen isotopic composition of nitrate (δ 15 N-NO 3 − ) in a ruralurban river system in Southeastern China. A total of 16 easily obtained hydro-chemical variables were measured in the wet season (September 2019) and dry season (January 2020) and used to develop the SVR prediction model. The grading method utilized ~75% (35) of the samples for model building while the remaining 11 samples assessed model performance. Principal component analysis (PCA) extracted 7 principal components for SVR model inputs as PCA reduces superfluous variables. We optimized tuning parameters in the SVR model using a grid search technique coupled with V-fold cross-validation. The optimized SVR model provided accurate δ 15 N-NO 3 − predictions with a determination coefficient (R 2 ) of 0.88, Nash-Sutcliffe (NS) of 0.87, and mean square error (MSE) of 0.53‰ in the testing step, and performed much better than the corresponding multivariate linear regression model (R 2 = 0.60, NS = 0.58 and MSE = 1.76‰) and general regression neural network model (R 2 = 0.66, NS = 0.65 and MSE = 1.45‰). Overall, the SVR model provides a potential indirect method to predict environmental isotope values for water quality management that will complement and enhance the interpretation of direct measurements of δ 15 N-NO 3 − .

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“…For δ 18 O of nitrate, atmospheric deposition and NO 3 − fertilizer are +17 to +25‰ and +25 to +75‰, respectively, while the δ 18 O-NO 3 − values sourced from microbial nitrification of NF, SN and MS are appreciably lower than those of AD and NO 3 − fertilizer, and often vary from −5‰ to +15‰ (Kendall and McDonnell, 1998;Mayer et al, 2001). Nowadays, several studies reported successful application of the dual stable isotopes of NO 3 − to characterize the sources and processes affecting NO 3 − in water bodies such as Adebowale et al (2019) and Hu et al (2019b). Furthermore, to develop quantitative information on NO 3 − source apportionment in water bodies, Xue et al (2012) introduced a powerful tool known as the Markov Chain Monte Carlo mixing model that was adopted from isotopic analysis of food-webs.…”

Section: Introductionmentioning

confidence: 99%

Riverine nitrate source apportionment using dual stable isotopes in a drinking water source watershed of southeast China

Shang

Huang

Mei

et al. 2020

Science of The Total Environment

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Tracing the sources of nitrate in the rivers and lakes of the southern areas of the Tibetan Plateau using dual nitrate isotopes

Cited by 61 publications

References 44 publications

A Complete Isotope (δ¹⁵N, δ¹⁸O, Δ¹⁷O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region

A Complete Isotope (δ¹⁵N, δ¹⁸O, Δ¹⁷O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region

A support vector regression model to predict nitrate-nitrogen isotopic composition using hydro-chemical variables

Riverine nitrate source apportionment using dual stable isotopes in a drinking water source watershed of southeast China

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Tracing the sources of nitrate in the rivers and lakes of the southern areas of the Tibetan Plateau using dual nitrate isotopes

Cited by 61 publications

References 44 publications

A Complete Isotope (δ15N, δ18O, Δ17O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region

A Complete Isotope (δ15N, δ18O, Δ17O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region

A support vector regression model to predict nitrate-nitrogen isotopic composition using hydro-chemical variables

Riverine nitrate source apportionment using dual stable isotopes in a drinking water source watershed of southeast China

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Product

Resources

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A Complete Isotope (δ¹⁵N, δ¹⁸O, Δ¹⁷O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region

A Complete Isotope (δ¹⁵N, δ¹⁸O, Δ¹⁷O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region