Geochemistry, stable isotopes and statistic tools to estimate threshold and source of nitrate in groundwater (Sardinia, Italy)

Biddau, Riccardo; Dore, Elisabetta; Pelo, Stefania Da; Lorrai, Mario; Botti, Paolo; Testa, Maurizio; Cidu, Rosa

doi:10.1016/j.watres.2023.119663

Cited by 27 publications

(5 citation statements)

References 61 publications

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“…NO 3 sources were not identi ed in those studies, although agricultural activities, pit latrines and animal waste were hypothesized as possible sources. Similar investigations in other parts of the world suggested that, most commonly, anthropogenic sources such as nitrogen fertilizer, manure, municipal and domestic sewage discharge, pit latrines, soil organic nitrogen and atmospheric deposition contribute to NO 3 loading of groundwaters (Biddau et al 2023, Kendall et al 2007).…”

Section: Introductionmentioning

confidence: 62%

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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Section: Introductionmentioning

confidence: 62%

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

Aleku,

Dähnke,

Pichler

2024

Preprint

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“…− of the groundwaters in the middle region supported the dominant role of wastewater (Figures 5b and 6b) [71][72][73]. A few points were scattered from the correlation, which can be ascribed to the evaporate (e.g., gypsum) dissolution in the arid region [74,75] or as a result of using CF enriched with SO 4 2− [13,76]. In addition, most of the groundwater samples in the study area exhibited TDS concentrations below 1000 mg/L associated with a low (NO 3 − + Cl − )/HCO 3 − ratio.…”

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confidence: 89%

“…− levels in groundwater cause ecological issues such as eutrophication of nearby surface water and hypoxia [1,[12][13][14][15][16][17][18]. Furthermore, NO 3 − in drinking water has been associated with health risks such as methemoglobinemia and cancer [19][20][21][22].…”

Section: High Nomentioning

confidence: 99%

Nitrate Source and Transformation in Groundwater under Urban and Agricultural Arid Environment in the Southeastern Nile Delta, Egypt

Kasem,

Xu,

Jiang

et al. 2023

Water

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With the intensification of human activities, nitrate pollutants in groundwater are receiving increasing attention worldwide. Especially in the arid Nile Delta of Egypt, groundwater is one of the most valuable water resources in the region. Identifying the source of nitrate in groundwater with strong human disturbances is important to effective water resource management. This paper examined the stable isotopes (δ15N/δ18O-NO3 and δ2H/δ18O-H2O) and the hydrogeochemical parameters of the shallow groundwaters in the arid southeast of the Nile Delta to assess the potential sources and transformation processes of nitrate under severe urban and agricultural activities. The results revealed that the groundwaters were recharged by the Nile River. Meanwhile, the infiltration of irrigation water occurred in the west, while the mixing with the deep groundwater occurred in the east regions of the study area. The TDS, SO42−, NO3−, and Mn2+ concentrations of groundwaters (n = 55) exceeded the WHO permissible limit with 34.6%, 23.6%, 23.6%, and 65.5%, respectively. The NO3− concentrations in the shallow groundwaters ranged from 0.42 mg/L to 652 mg/L, and the higher levels were observed in the middle region of the study area where the unconfined condition prevailed. It extended to the deep groundwater and eastward of the study area in the groundwater flow direction. The δ15N-NO3 and δ18O-NO3 values suggested that the groundwater NO3− in the west and east regions of semi-confined condition were largely from the nitrification of soil organic nitrogen (SON) and chemical fertilizer (CF). In contrast, wastewater input (e.g., domestic sewage and unlined drains) and prevalent denitrification were identified in the middle region. The denitrification might be tightly coupled with the biogeochemical cycling of manganese. This study provides the first report on the groundwater NO3− dynamics in the Nile Delta, which generated valuable clues for effective water resource management in the arid region.

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“…The isotopic composition relative to 87 Sr/ 86 Sr; δ 11 B, δ 34 S SO4 in the identified end members were included simultaneously in the mixing model. The Bayesian statistical models calculated confidence intervals for source apportionment while taking into account the uncertainty arising from the input [50][51][52][53]. This statistical model allows for the joint evaluation of multiple isotopes to define the recharge source contributions for each analyzed sample on a probabilistic basis, thereby reducing uncertainties.…”

Section: Isotopic Compositionmentioning

confidence: 99%

Assessing Recharge Sources and Seawater Intrusion in Coastal Groundwater: A Hydrogeological and Multi-Isotopic Approach

Porru,

Arras,

Biddau

et al. 2024

Water

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One of the crucial challenges of our time is climate change. The consequences of rising sea levels and drought greatly impact water resources, potentially worsening seawater intrusion. Characterizing coastal aquifers is an essential step in devising strategies to address these phenomena. Seawater intrusion poses a critical socio-economic and environmental issue in the coastal plain of Muravera, southeastern Sardinia (Italy). This coastal plain is an important agricultural area in Sardinia, and the health of the crops is compromised by the increasing salinization of shallow groundwater. To enhance our understanding of the hydrogeological conceptual model, which is essential for a sustainable resource management system, hydrogeological investigations were conducted and complemented by the chemical and multi-isotopic analyses of groundwater. The main objectives of this study were to identify groundwater recharge areas, understand salinization mechanisms and trace the evolution of water chemistry. Within this framework, a monthly survey monitoring piezometric level and electrical conductivity was carried out for one year. This survey was integrated with chemical and isotope analyses, including δ18OH2O and δ2HH2O, δ11B, δ18OSO4, δ34SSO4, and 87Sr/86Sr. Hydrochemistry analysis results revealed the occurrence of seawater–freshwater mixing, extending up to 4 km inland. H2O isotope analysis confirmed the mixing processes and indicated the meteoric origin of recharge waters for both shallow and semi-confined aquifers. The strontium isotopes ratio facilitated the identification of four main groundwater flow paths, confirmed by the SIAR model. The results of this combined hydrogeological–geochemical–isotopic survey provide essential elements for the future implementation of an integrated and sustainable management system. These findings enable interventions to slow the process of seawater intrusion and meet the economic needs for the development of local communities.

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Geochemistry, stable isotopes and statistic tools to estimate threshold and source of nitrate in groundwater (Sardinia, Italy)

Cited by 27 publications

References 61 publications

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

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

Nitrate Source and Transformation in Groundwater under Urban and Agricultural Arid Environment in the Southeastern Nile Delta, Egypt

Assessing Recharge Sources and Seawater Intrusion in Coastal Groundwater: A Hydrogeological and Multi-Isotopic Approach

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