Min Wang

Understanding groundwater quality and its controlling mechanisms is vital for the sustainable use of water resources in agriculturally intensive regions. This study evaluates the hydrochemical characteristics, controlling geochemical processes, and overall water quality of 226 groundwater samples collected from a typical agricultural reclamation area in the Sanjiang Plain, northeastern China. Major ion compositions indicate that groundwater is predominantly of the Ca–HCO₃ type, with bicarbonate, calcium, and magnesium as the dominant constituents. Spatial and statistical analyses reveal that rock weathering—particularly the dissolution of carbonates and silicates—is the primary natural process influencing groundwater chemistry, while cation exchange contributes moderately. Anthropogenic inputs, especially from fertilizers, livestock waste, and wastewater discharge, were found to elevate concentrations of NO₃⁻, Cl⁻, and SO₄²⁻ in localized zones. The entropy-weighted water quality index (EWQI) was applied to assess overall groundwater suitability. Results show that 89.8% of samples fall into “excellent” or “good” categories, though 6.6% of samples indicate poor to very poor water quality. This study identified the hydrochemical characteristics, sources of substances, and water quality of groundwater in the reclamation area, providing a basis for scientific prevention and control, rational utilization, and protection of groundwater resources.

Groundwater is vital to local human life and agricultural irrigation, and the quality of the water is critical to human health. As a result, it is critical to investigate the hydrochemical evolution and water quality of groundwater in the Sanjiang Plain. There were 259 samples obtained. Furthermore, hydrogeochemical simulation was performed to highlight groundwater’s hydrochemical features, evolution process, and water quality. The analytical results show that the groundwater in the study area is somewhat alkaline with a mean TDS of 285.94 mgL⁻¹ and the primary contributing ions being Ca²⁺ and HCO₃⁻. The closer the concentration of TDS and NO₃⁻ is to the city, the higher the concentration, indicating that the chemical composition of the water body has been affected by certain human activities. The Piper diagram, Gibbs diagram, and correlation analysis results demonstrate that the chemical type of groundwater is mostly HCO₃-Ca and the hydrochemistry is primarily regulated by weathering and carbonate and silicate dissolution. According to the entropy-weighted water quality index, the groundwater quality in this location is pretty acceptable. This study could help strengthen groundwater quality monitoring based on local conditions, identify the source of nitrate, provide data support for the safe use of local water resources, and serve as a reference for global water chemical evolution and water quality evaluation in cold regions.

Groundwater resources are an essential component of global water resources. Long-term consumption of groundwater exceeding the standard levels for iron and manganese can lead to chronic diseases, posing a threat to human health. The Sanjiang Plain is the largest swamp wetland area in China and has high levels of iron and manganese in the groundwater, but the cause still needs to be clarified. Based on the results of water quality tests of 41 groundwater samples in the Eastern Sanjiang Plain, this paper analyzes the distribution characteristics and causes of iron and manganese from the perspectives of the original strata environment, redox conditions, pH conditions, and hydrochemical indicator factors in the research area, using statistical methods and GIS technology. The results show that high iron and manganese content in groundwater is prevalent in the Eastern Sanjiang Plain, and the exceedance rate of manganese is higher than that of iron (87.80% and 82.90%, respectively). The primary sources of iron and manganese in groundwater are iron and manganese minerals in the original strata environment. Influenced by factors such as acidic conditions, reducing environment, and rich organic matter, insoluble high-valent iron and manganese oxides are reduced to low-valent and soluble divalent iron and manganese. At the same time, groundwater’s high mineralization and evaporation concentration are conducive to increased iron and manganese content, while the influence of human activities is small.