Coupling stable isotopes to evaluate sources and transformations of nitrate in groundwater and inflowing rivers around the Caohai karst wetland, Southwest China

Cao, Xingxing; Yang, Shi-di; Wu, Pan; Liu, Shan; Liao, Jia-Hao

doi:10.1007/s11356-021-13827-4

Cited by 18 publications

(5 citation statements)

References 50 publications

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“…Having a significantly higher level of Cl – with much lower ratios of NO 3 – /Cl – is a specific characteristic of municipal sewage-contaminated groundwater. , It was observed that few groundwater samples showed clues of contamination and mixing with municipal sewage or wastewater with shallow groundwater (Figure a). Samples with much lower Cl – concentrations and higher NO 3 – levels could be ascribed to nitrate contamination of recently infiltrated rainwater by agricultural runoff in the wet season. , Thus, nitrate could be leached from the inorganic fertilizers from extensive agricultural lands, urban runoff, and municipal sewage or wastewater in the NCP. Anthropogenic pollution of groundwater in the NCP was confirmed by the cumulative probability analysis as well (Text S8 and Figure S9).…”

Section: Resultsmentioning

confidence: 99%

“…Samples with much lower Cl − concentrations and higher NO 3 − levels could be ascribed to nitrate contamination of recently infiltrated rainwater by agricultural runoff in the wet season. 42,43 Thus, nitrate could be leached from the inorganic fertilizers from extensive agricultural lands, urban runoff, and municipal sewage or wastewater in the NCP. Anthropogenic pollution of groundwater in the NCP was confirmed by the cumulative probability analysis as well (Text S8 and Figure S9).…”

Section: Groundwater As Irrigation Watermentioning

confidence: 99%

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Spatiotemporal Variation of Groundwater Quality in North Central Province, Sri Lanka

Indika

Wei

et al. 2023

ACS EST Water

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This study focused on fulfilling the demand for a comprehensive investigation of groundwater quality in the North Central Province (NCP) of Sri Lanka to achieve United Nations Sustainable Development Goal 6 (Ensure availability and sustainable management of water and sanitation for all). The NCP was selected as the study area due to its highest prevalence of chronic kidney disease with unknown etiology within Sri Lanka. Here, 334 shallow and deep groundwater samples were collected at the end of wet and dry seasons, respectively. Results revealed that elevated and unexpected levels of salinity, hardness, fluoride, nitrate, sulfate, and dissolved organic carbon and the alkaline nature of groundwater were the main issues, and the Ca-HCO3 type was dominant in the groundwater. Water quality index analyses showed that 8.9% and 13.8% of wells had poor quality undrinkable groundwater in wet and dry seasons, respectively. Only 7% of samples were susceptible to sodium and salinity hazards for irrigational use. Reverse osmosis technology with a softening and activated carbon pretreatment process was identified as the most suitable way to treat groundwater with high salinity for many regions of the NCP. The groundwater quality atlas for the NCP created by this study was very useful for making a master plan of safe drinking water supplies and developing and implementing cost-effective water purification technologies in the NCP.

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Section: Resultsmentioning

confidence: 99%

Section: Groundwater As Irrigation Watermentioning

confidence: 99%

Spatiotemporal Variation of Groundwater Quality in North Central Province, Sri Lanka

Indika

Wei

et al. 2023

ACS EST Water

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“…In this study, the NO 3 − /Cl − ratios in the groundwater across Alesa, Ogale, and Ebubu overall were elevated, suggesting an anthropogenic in uence. The relationship of the NO 3 − /Cl − vs Cl − concentration appears to be constant, implying that the groundwater has a consistent, nonvariable source of NO 3 − (Cao et al 2021). All the samples showed signi cantly higher Cl − levels with lower NO 3 − /Cl − (Fig.…”

Section: Field Measurements and Chemical Datamentioning

confidence: 95%

Source, transport and fate of nitrate in shallow groundwater in the eastern Niger Delta

Aleku,

Dähnke,

Pichler

2024

Preprint

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The eastern Niger Delta region in Nigeria is a hotspot for reactive nitrogen pollution due to extensive animal husbandry, pit latrine usage and agricultural practices. Despite the high level of human activity, the sources and processes affecting nitrogen in groundwater remain understudied. Groundwater nitrate (NO3−) concentrations are highly variable, with some areas recording values well above the safe drinking water threshold of 50 mg/L. This is particularly true near municipal sewage systems. Elevated nitrite (NO2−) and ammonium (NH4+) concentrations were also detected in the study area. Sewage analysis revealed NO3− concentrations ranging from 1 to 145 mg/L, NO2− from 0.2 to 2 mg/L, and notably high NH4+ concentrations. A comparison of major ions indicated that 71%, 90%, 87%, and 92% of groundwater samples surpassed reference site levels for calcium (Ca2+), sodium (Na+), potassium (K+), and chloride (Cl−), respectively, pointing to sewage as a likely source of contamination. The NO3−/Cl− ratios at several sites suggested that most groundwater NO3− originates from human waste. Stable isotope analysis of NO3− showed a general enrichment in 15N and, in some cases, a depletion in 18O, indicating that the NO3− originates from sewage-derived NH4+ nitrification. Although denitrification, a process that reduces NO3−, is present, the high dissolved oxygen (DO) and NO3− levels in the groundwater suggest that denitrification is insufficient to fully mitigate NO3− pollution. Consequently, there is a risk of NO3− leaching from shallow aquifers into the Niger Delta’s surface waters and ultimately into the coastal ocean.

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“…Its catchment area is 19.8 km 2 during the dry season and 26.0 km 2 during the rainy season. With a water storage capacity of 3.9 × 10 7 m 3 [24], this basin is characterized by a subtropical monsoon climate with an average annual temperature of 10.6 • C and an annual rainfall of 1000 mm, with the rainfall mainly concentrated in summer, making this basin one of the least rainy areas in Guizhou [25]. The lake's primary water source is rainfall, followed by groundwater [26].…”

Section: Methodsmentioning

confidence: 99%

Water Level Fluctuation Rather than Eutrophication Induced the Extinction of Submerged Plants in Guizhou’s Caohai Lake: Implications for Lake Management

Chao,

Jiang,

Wang

et al. 2024

Water

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The intensifying global decline in submerged aquatic lake plants is commonly attributed to lake eutrophication, while other drivers such as water levels are seldom considered. This study focused on the sudden extinction of the submerged plants in Caohai Lake, Guizhou, and employed long-term data and a whole-lake water level manipulation experiment to explore the impacts of nutrients and water level changes on the decline in submerged plants. The results indicated that over the past 40 years, the total nitrogen and ammonia nitrogen in the water did not change significantly, while the total phosphorus showed a significant decreasing trend. In recent years, however, the water level rose. The biomass of submerged plants continuously increased until a sudden large-scale extinction occurred in 2021; chlorophyll a also significantly increased. It is speculated that the large-scale extinction of the submerged plants was caused by water level fluctuations rather than eutrophication. After the restoration of the natural hydrological regime of low water levels in winter and spring and high levels in summer and autumn, the submerged plants gradually recovered, with the biomass increasing to 922.6 g/m2 in 2023. The structural equation modeling indicated that the water depth and bottom light availability were the main drivers for the changes in the submerged plants. However, in lake protection and management, more attention is often paid to controlling nutrients, while other influencing factors are neglected. These findings confirm the importance of water levels in the decline in and restoration of submerged plants in shallow lakes, suggesting a focus on water level management in lake protection and aquatic vegetation restoration.

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Coupling stable isotopes to evaluate sources and transformations of nitrate in groundwater and inflowing rivers around the Caohai karst wetland, Southwest China

Cited by 18 publications

References 50 publications

Spatiotemporal Variation of Groundwater Quality in North Central Province, Sri Lanka

Spatiotemporal Variation of Groundwater Quality in North Central Province, Sri Lanka

Source, transport and fate of nitrate in shallow groundwater in the eastern Niger Delta

Water Level Fluctuation Rather than Eutrophication Induced the Extinction of Submerged Plants in Guizhou’s Caohai Lake: Implications for Lake Management

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