Increasing anthropogenic contributions on hydrochemical evolution of groundwater in the Yellow River basin over the past decade

Abstract

The temporal evolution of groundwater chemistry is crucial for guiding sustainable water resource management. In China, the Yellow River Basin features active geological structures, diverse lithology, and significant human impacts, leading to unclear patterns and factors governing groundwater chemistry evolution. In this study, we investigated the characteristics, sources, and controlling factors of groundwater chemistry in the Yellow River Basin during the period of 2011–2022, with a view to providing guidance for water chemistry management in the region. The results indicate that over time, major ions (Na⁺, Mg²⁺, Cl⁻, SO₄²⁻, NO₃⁻, and F⁻) in the Yellow River Basin's groundwater rise then fall, with pH initially increasing before stabilizing at a mild alkaline level. The anions in groundwater chemistry are dominated by HCO₃⁻, which accounts for 38.89–60.78% of the anion concentration equivalent, and cations are dominated by Na⁺, which accounts for 31.43–72.22%. Hydrochemical types shift among HCO₃–Ca, Cl–SO₄–Na, and mixed HCO₃–Ca–Mg, with Cl–SO₄–Na type correlating positively with human activity level. Dissolution of minerals are the primary sources of groundwater chemistry. Hydrochemical evolution is driven by rock weathering alongside human activities such as sewage discharge and fertilizer application. Initially, mineral weathering was the key factor, with the chemical composition becoming dynamically altered as human activity increased. In summary, the groundwater chemistry in the Yellow River Basin mainly stems from mineral reactions, initially by rock weathering and later affected by rising human activities. This study advances knowledge of groundwater geochemical dynamics in the Yellow River Basin, supporting improved management and sustainable water resource use.