Coastal streams and sewage outfalls: Hot spots of mercury discharge, pollution and cycling in nearshore environments

Zhijia Ci; Xiong Tang; Wenjie Shen; Baowei Chen

doi:10.1016/j.marpolbul.2023.115536

Coastal streams and sewage outfalls: Hot spots of mercury discharge, pollution and cycling in nearshore environments

Mar Pollut Bull. 2023 Oct:195:115536. doi: 10.1016/j.marpolbul.2023.115536. Epub 2023 Sep 12.

Authors

Zhijia Ci¹, Xiong Tang², Wenjie Shen³, Baowei Chen⁴

Affiliations

¹ Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, School of Marine Sciences, Sun Yat-sen University, Zhuhai 519082, China. Electronic address: cizhj@mail.sysu.edu.cn.
² Guangdong Eco-Engineering Polytechnic, Guangzhou 510520, China.
³ School of Earth Sciences and Engineering, Sun Yat-sen University, Zhuhai 519082, China; Guangdong Key Laboratory of Geological Process and Mineral Resources Exploration, Zhuhai 519082, China.
⁴ Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, School of Marine Sciences, Sun Yat-sen University, Zhuhai 519082, China.

PMID: 37708606
DOI: 10.1016/j.marpolbul.2023.115536

Abstract

The coastal streams (CSs) and sewage outfalls (SOs) are widely distributed and direct anthropogenic stress on global coastal ecosystems. However, the CS/SO-associated mercury (Hg) discharge, pollution and cycle in nearshore environment are less quantified. Here, we report that total Hg (THg) and methylmercury (MMHg) concentrations in waters of CSs (n = 8) and SOs (n = 15) of the northern China were ∼10² to 10³ times of coastal surface waters and 10 to 10² times of major rivers in China and other regions. The CS/SO discharges resulted in the increase of total organic carbon (TOC) contents, THg and MMHg concentrations and TOC-normalized THg and MMHg concentrations in sediments of CS/SO-impacted coasts. The laboratory experiments further illustrated that the CS/SO-impacted sediments characterized with high potentials of dissolved THg and MMHg productions and releases. Our findings indicate that the layout optimization of SOs is able to reduce the Hg risk in coastal environment.

Keywords: Coastal stream; Mercury; Methylmercury; Nearshore environment; Sewage outfall.