Assessing the environmental risk, fractions, and remobilization of copper and zinc in the sediments of the Jialing River

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RESEARCH ARTICLE

Assessing the environmental risk, fractions, and remobilization of copper and zinc in the sediments of the Jialing River—an important tributary of the Yangtze River in China Tuo Zhang 1

&

Lijuan Li 2 & Fei Xu 1 & Xiangyu Chen 1 & Li Du 1 & Yunxiang Li 1

Received: 11 March 2020 / Accepted: 30 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract Copper (Cu) and zinc (Zn) are two heavy metal pollutants that pose a serious risk in the Jialing River. Cu and Zn are transported into the sediment primarily due to the activities of the mining and smelting industries. In this study, we employed the diffusive gradient in thin films (DGT) technique, sequential extraction, and two assessment methods to evaluate the remobilization, fractions, and environmental risk in the downstream section of the Jialing River. The total concentrations of Cu and Zn in the four study areas followed the order S3 > S2 > S4 > S1, and the assessment results indicated that Cu and Zn presented a low environmental risk in the study area. Cu and Zn were primarily bound to the Fe/Mn oxide fraction (F2) and the residual fraction (F4). The results of the DGT probe showed a clear vertical distribution of Cu and Zn in the sediment (from 3 to − 12 cm), and both elements showed obvious increasing trends at the bottom of the probe. The correlation analysis indicated that CDGT-Cu correlated well with CDGT-Zn (r = 0.834, p < 0.01). The flux results showed that the sediment in the downstream section of the Jialing River is a major source of Cu and Zn and that there is a potential risk of release to the overlying water. Further analysis found that CDGTFe was negatively correlated with CDGT-Cu and CDGT-Zn, indicating that Fe may influence the remobilization of these metals. In addition, a hotspot of CDGT-Cu and CDGT-Zn at the bottom of the probe corresponded with a dark area in the AgI gel measuring CDGT-S. These results indicate that Fe and S are factors that mitigate the release of Cu and Zn from sediments. Keywords Jialing River . Sediment . Cu . Zn . DGT

Introduction Currently, heavy metal pollution in sediments is of great concern due to its toxicity, resistance to degradation, and tendency to bioaccumulate (Ndiba et al. 2008; Zhang et al. 2014; Yin and Zhu 2016). Heavy metals may originate from both natural processes and anthropogenic activities. Natural processes include rock and soil weathering and erosion, which are generally very slow processes and generally do not result in substantial environmental pollution (Dalman et al. 2006). Responsible Editor: Philippe Garrigues * Tuo Zhang [email protected] 1

College of Environmental Science & Engineering, China West Normal University, Nanchong 637009, Sichuan, China

2

Institute of Agricultural Environment and Sustainable Development, Chinese Academy of Agriculture Sciences, Beijing 100081, China

Conversely, major anthropogenic activities, such as mining, smelting, municipal wastewater treatment, and urban and agricultural runoff, can be major sources of e