Evolution of and mechanisms controlling water chemistry in the Beijiang River Basin over the past four decades

IF 3.4 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Journal of Geochemical Exploration Pub Date : 2025-02-25 DOI:10.1016/j.gexplo.2025.107736

Zaizhi Yang , Tao Jiang , Zuobin Liang , Xinfeng Zhao , Kun Ren , Di Tian , Lei Gao , Qirui Wu , Shaoheng Li , Rui Li , Lichun Xie , Jianyao Chen

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Abstract

This study investigated long-term hydrochemical data from the main channel (Beijiang) and three tributaries (Lianjiang, Wujiang, and Zhenjiang) in the middle and upper Beijiang River, the second-largest tributary of the Pearl River, from 1985 to 2023. The results showed that Ca²⁺ (>44.1 %) and HCO₃⁻ (>76.17 %) are the dominant cation and anion, respectively. These results indicate that weathering of carbonates and silicates was the primary natural factor influencing riverine chemistry in the basin. Total dissolved solids (TDS) fluctuated between 33.3 and 399 mg/L and pH between 6.5 and 9.2, with the highest TDS levels in Wujiang (191 mg/L), followed by Lianjiang (175 mg/L), Beijiang (149 mg/L), and Zhenjiang (84.7 mg/L). The TDS trend in Beijiang exhibited a significant decline before 2001, followed by a subsequent increase, while the average concentrations of acidic substances (Cl⁻, NO₃⁻, and SO₄²⁻) increased by >38 %, while pH value does not decrease in response to the elevated SO₄²⁻ due to dissolution of carbonate. Ion concentrations mostly decline with discharge rate, except for NO₃⁻, which showed transport limitation and enrichment with increasing discharge rate. The ion flux patterns were classified as discharge-dominated or concentration-dominated. The annual TDS flux of Beijiang was approximately 5.0 × 10⁶ tons and the ionic runoff modulus was 148.4 t·km⁻²·yr⁻¹, which was relatively high compared to that of other rivers in the world. The correlation between ions concentrations and socioeconomic factors suggests that socio-economic activities significantly influence water chemistry. Industrial relocation and large hydraulics project may lead to abrupt fluctuations and sustained increases in water chemistry parameters. The generalized additive models showed that natural factors explained 40.8–50.7 % of the deviance, while socioeconomic factors related to anthropogenic activities explained >79.5 % due to increasing SO₄²⁻, NO₃⁻ and Cl⁻ trends. Given the importance of the river to the Guangdong–Hong Kong–Macao Greater Bay Area, enhanced management and monitoring are needed to protect the regional water supply.

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来源期刊

Journal of Geochemical Exploration 地学-地球化学与地球物理

CiteScore

7.40

自引率

7.70%

发文量

148

审稿时长

8.1 months

期刊介绍： Journal of Geochemical Exploration is mostly dedicated to publication of original studies in exploration and environmental geochemistry and related topics. Contributions considered of prevalent interest for the journal include researches based on the application of innovative methods to: define the genesis and the evolution of mineral deposits including transfer of elements in large-scale mineralized areas. analyze complex systems at the boundaries between bio-geochemistry, metal transport and mineral accumulation. evaluate effects of historical mining activities on the surface environment. trace pollutant sources and define their fate and transport models in the near-surface and surface environments involving solid, fluid and aerial matrices. assess and quantify natural and technogenic radioactivity in the environment. determine geochemical anomalies and set baseline reference values using compositional data analysis, multivariate statistics and geo-spatial analysis. assess the impacts of anthropogenic contamination on ecosystems and human health at local and regional scale to prioritize and classify risks through deterministic and stochastic approaches. Papers dedicated to the presentation of newly developed methods in analytical geochemistry to be applied in the field or in laboratory are also within the topics of interest for the journal.