Characteristics of Heavy Metals in Seawater and Sediments from Daya Bay (South China): Environmental Fates, Source Apportionment and Ecological Risks

Wei Tao,Jian Gong,Wanping Zhang,Haidong Li,Xiaojuan Peng,Quansheng Lou,Jianjun Ye

doi:10.3390/su131810237

Abstract

In this study, the spatiotemporal distributions, potential sources, and ecological risks of Hg, Cr, and As in seawater, and Hg, As, Zn, Cd, Pb, and Cu in sediments from Daya Bay were investigated. The five-year average concentrations of Hg, Cr, and As in seawater were 0.020 μg/L, 0.79 μg/L, and 2.08 μg/L, respectively. The five-year average concentrations of Hg, As, Zn, Cd, Pb, and Cu in surface sediments were 0.04 mg/kg, 7.34 mg/kg, 63.81 mg/kg, 0.23 mg/kg, 25.60 mg/kg, and 11.78 mg/kg, respectively. Annual variations in Hg, Cr, and As in seawater exhibited different trends. HMs in sediments, such as As, Zn, Pb, and Cu, exhibited similar annual variations, whereas Hg and Cd exhibited different annual variations. The spatial distribution of metal species in seawater and sediments showed significant variability, and the concentrations decreased gradually from the coast to the open sea. The comprehensive potential ecological hazard index (RI) of HMs in sediments indicated a relatively high risk, especially for Hg and Cd contamination. The geoaccumulation indices (Igeo) of As, Zn, Pb, and Cu suggested that these metals did not pollute Daya Bay, whereas those of Cd and Hg indicated mild and moderate pollution. The environmental fates of HMs were discussed based on Pearson correlation analysis, revealing that concentrations of HMs were greatly affected by parameters, such as pH, salinity, dissolved oxygen (DO), and total organic carbon (TOC). Principal component and factor analyses indicated that Hg, Cr, As, and dissolved inorganic nitrogen (DIN) in water originated from similar sources, including domestic sewage and wastewater from fishing ports, runoffs, and outlets. For sediments, it was proposed that Cu, Zn, As, Pb, and TOC exhibited similar sources, including cage culture and waste discharge from outlets. Meanwhile, Hg and Cd originated from other point sources, such as a harbor. The study suggests that sustainable management and economic development be integrated to control pollutant emissions in Daya Bay.

Highlights

Heavy metals (HMs) are major pollutants in marine environments because of their persistence, high toxicity, and bioaccumulation properties [1,2]
Daya Bay covers an area of about 600 km2 and is located north of the South China Sea (Figure 1) (22◦ 300 –22◦ 500 N and 114◦ 290 –114◦ 490 E); it is surrounded by Hong Kong in the southwest, Dapeng Cove in the west, and Red Bay in the east
The pollution status of Daya Bay the -4Igeo values is consistent with the results provided by the potential ecological risk (Eir)

Summary

Introduction

Heavy metals (HMs) are major pollutants in marine environments because of their persistence, high toxicity, and bioaccumulation properties [1,2]. HMs in marine environments often originate from various natural and anthropogenic sources, such as geologic weathering, urban runoff, domestic sewage, and industrial and agricultural activities [4]. Sustainability 2021, 13, 10237 bays are affected by human activity, such as wastewater discharge, land use, and land cover transformations [5]. In Daya Bay (Huizhou, Guangdong Province, China), marine aquaculture, nuclear power plants, petrochemical industries, and industrial enterprises coexist and contribute to HM pollution in water and sediment [6,7,8]. Zhao et al did not find high levels of Cd, Cr, Cu, Hg, or Zn in sediments from Daya Bay [12].

Methods

Results

Conclusion