Distribution, Formation and Human Health Risk of Fluorine in Groundwater in Songnen Plain, NE China

Distribution, enrichment mechanisms, and health risk assessment of high-fluorine groundwater in the Yudong Plain, Henan Province, China

The Yudong Plain is in the eastern part of Henan Province, China, where there is little rain and high evaporation. Compared to other areas in Henan Province, the groundwater fluorine content is generally high, which affects the health of residents. Based on the systematic analysis of water chemistry data of shallow and mid-depth groundwater samples in the Yudong Plain, the causes of shallow and mid-depth high-fluorine groundwater in the Yudong Plain were explored using mathematical statistics, spatial interpolation, and ion ratios. The results show that the fluorine contents of both shallow and mid-depth groundwater in the study area are high. The shallow samples had fluorine contents ranging from 0.1 to 4.89 mg/L, with an exceedance rate of 48% and an average content of 1.15 mg/L. The fluorine content of mid-depth samples ranged from 0.14 to 3.32 mg/L, with an exceedance rate of 68% and an average content of 1.33 mg/L. The shallow high-fluorine groundwater is mainly distributed in the central low-lying area, and its main hydrochemical type is HCO₃-Na·Mg; the mid-depth high-fluorine groundwater is mainly distributed in strips in the north and east of the study area, and its main water chemistry type is HCO₃-Na. Fluorine enrichment in shallow groundwater in the study area is controlled by rock weathering, evaporation concentration, and competitive adsorption, while leaching and dissolution of fluorine-containing minerals in sedimentary strata are the main factors influencing fluorine enrichment in mid-depth groundwater. The results of the human health risk assessment (HRA) showed that the mean non-carcinogenic hazard quotients (HQs) in shallow groundwater were 0.95, 0.64, 0.57, and 0.55 for infants, children, teenagers, and adults, respectively, while the mean non-carcinogenic HQs in mid-depth groundwater were 1.11, 0.74, 0.66, and 0.63, respectively. The study provides a scientific basis for the rational development and use of groundwater in the area and offers theoretical support for the prevention and control of groundwater pollution.

Degradation kinetics and transformation pathway of methyl parathion by δ-MnO2/oxalic acid reaction system

Methyl parathion (MP) is a typical organophosphorus pesticide that is widely used worldwide, and hydrolysis, oxidation and reduction are the main abiotic degradation processes. Manganese dioxide (MnO₂) and organic acid can participate in various geochemical processes of pollutants, a reaction system was constructed to degrade MP using δ-MnO₂ and oxalic acid. The δ-MnO₂/oxalic acid reaction system could efficiently degrade MP, and the removal rate of MP (20 μM) reached 67.83% within 30 h under the optimized conditions (pH 5, [δ-MnO₂] = 2 mM, [oxalic acid] = 100 mM). MP was hydrolyzed by substitution reactions of S_N@P and S_N@C, and reduced by conversion of the nitro groups (-NO₂) in MP and its hydrolysates to amino groups (-NH₂). The primary active substance produced in the reaction system was the complexes dominated by Mn(III)-oxalic acid. This study provides a scientific basis for the degradation of organophosphorus pesticides using MnO₂ and an organic acid. The results have important theoretical significance and application value for pollution control and remediation of organophosphorus pesticides.

Valuation of ecosystem damage induced by soil-groundwater pollution in an arid climate area: Framework, method and case study

Groundwater is an important source of water, even the only source in some arid areas. However, climate changing and ecosystem damage induced by pollution aggravate water resource crisis. The "polluter pays" principle is deeply rooted in efforts to manage the polluted sites, particularly in the soil-groundwater environment. Unfortunately, there is no ecosystem damage compensation mechanism generally accepted by all stakeholders. In this study, we establish an assessment framework and valuation methods for ecosystem damage induced by soil-groundwater pollution in an arid climate area based on a "pollution source → target (soil-groundwater) → receptor (humans, animals, and plants) → damages → stakeholders (human society and ecosystem)" model that is usually applied in groundwater risk assessment research. Five economic loss are included in the valuation methods: (1) human health loss, (2) emergency disposal cost, (3) direct economic loss, (4) ecological restoration cost, and (5) ecosystem services loss. We apply the framework to a case study in an arid climate area, northwest China and calculate the total economic loss from ecosystem damage in the case study at 12.6 million yuan. The largest proportion of the total loss was the ecological restoration cost (85.6%), followed by the emergency disposal cost (11.2%), and finally ecosystem services loss (3.2%). Valuation of ecosystem damage from environmental pollution is essentially a socioeconomic issue. This study supplies a new framework and methods for valuing ecosystem damage induced by pollution, and offers suggestions for environmental management to reduce the damage caused by soil-groundwater pollution to health and ecosystems.

Groundwater Pollution Model and Diffusion Law in Ordovician Limestone Aquifer Owe to Abandoned Red Mud Tailing Pit

Red mud is a strong alkaline solid waste pollutant produced in the process of aluminum smelting, which causes great pollution to the regional groundwater environment due to its high content of fluorine and aluminum and high concentration of strong alkali. In this study, fluoride ion was selected as the model contaminant, and a numerical model of the groundwater flow field and solute transport was developed using GMS software to simulate and analyze the migration patterns of fluoride contaminants caused by the red mud pit for the fractured karst geohydrological conditions. The results demonstrated that the groundwater model and flow pattern were mainly controlled by atmospheric precipitation recharge, given flow boundary conditions and leakage of rivers and drains. When the concentration of fluorine pollutants in the red mud yard was 60.0 mg/L, the maximum migration distance of F− in the groundwater of the ordovician limestone aquifer was 473, 1160, 1595 and 1750 m after 1, 5, 10 and 15 years of bottom leakage, and the additional transport distances were 687, 435 and 155 m every 5 years, respectively. The range of F− pollution plume was 0.37 km2, 1.15 km2, 1.95 km2 and 2.14 km2, respectively and the range of newly added pollution plume was 0.78 km2, 0.80 km2 and 0.19 km2, respectively, every five years. Both indicated that with the extension of time, the migration and diffusion rate of pollutants slow down, and the diffusion volume increased first and then decreased. The F− pollution plume spread from the red mud pit to the northeast, which was consistent with the flow of groundwater. The high-concentration pollution plume was mainly distributed in the Ordovician limestone fractured aquifer in the northeast. This study revealed the migration law of red mud pollutants, and provided a scientific decision-making basis for the prevention and control of red mud groundwater pollution in the future.

River Ecological Restoration and Groundwater Artificial Recharge

There is an extensive water exchange between river water and groundwater in natural conditions [...]