Distributions and influencing factors of heavy metals in the coastal areas of the Yangtze River Estuary, China

Abstract

The sediment of coastal wetlands is the primary source and sink of heavy metals. Many heavy metal pollutants enter the wetlands with runoff, and the physicochemical processes such as adsorption/desorption and sedimentation/resuspension occur under the interaction of runoff, tide, and wave. Through field investigation, this paper studied the spatial and temporal distribution of heavy metal concentrations of particulate, dissolved, and sediment in the Yangtze River estuary in January and May 2021 and discussed the influence of water physicochemical conditions such as temperature (TEMP), dissolved oxygen (DO), pH, redox potential (Eh), salinity (SAL), electrical conductivity (EC), and suspended particulate matter (SPM) on heavy metal concentration. The risks of heavy metals in sediment in the Yangtze estuary were comprehensively evaluated by the geo-accumulation index (I_geo) method, potential ecological risk assessment, and the Sediment Quality Guidelines (SQGs). The principal component analysis (PCA) was adopted to explain the sources of different heavy metals. It was found that the particulate Cr and Cu in water mainly originated from atmospheric deposition. The dissolved Zn in water was attributed to ship emissions. The Cu in sediment mainly originated from anthropogenic emissions, and the Cd in sediment was mainly from atmospheric deposition.