Evaluation of Mercury Transformation and Benthic Organisms Uptake in a Creek Sediment of Pearl River Estuary, China

Long Chen,Wenrou Huang,Zhi Li,Mingguang Chen,Feng Li

doi:10.3390/w11061308

Abstract

A large fraction of mercury contaminant in the environment is from industrial production, and it potentially impairs human health once entering the food chain. Millions of people reside in the Pearl River Delta region, and water quality in the estuary directly affects their drinking water safety. Considering the highly intense anthropogenic activities and industrial productions, we attempted to measure the sediment mercury concentration in the Pearl River estuary. In this work, samples of a creek sediment within this region were collected and mercury concentrations were quantified. Total mercury, simultaneously extracted mercury, methylmercury, and bio-accumulated mercury were individually assayed. Results indicated that total mercury concentrations of investigated sites ranged from 1.073 to 4.450 µg/g dry sediment. The mercury in the sediment also transformed into more toxic methylmercury, which then adversely affected benthos biodiversity. Correlation analysis revealed that, mercury was accumulated into benthic microorganisms, mainly through the uptake of methylmercury. High concentrations of acid-volatile sulfide in the sediment indicated the presence of active sulfate-reducing bacteria, which could also catalytically transform inorganic mercury into methylmercury. Correlation analysis further showed that sulfate-reducing bacteria activity accounted for methylmercury formation.

Highlights

Mercury contamination is a global issue due to its significant toxic effects on human health, and its cytotoxicity being higher than many other heavy metals
We investigated mercury content in the sediments of the Pearl River estuary, since anthropogenic activities are highly intensive in this area
It has been reported that sediment microbes possessing the methylating genes hgcA and hgcB [25,58], such as Sulfate-reducing bacteria (SRB), play an important role to convert inorganic mercury ion into methylmercury

Summary

Introduction

Mercury contamination is a global issue due to its significant toxic effects on human health, and its cytotoxicity being higher than many other heavy metals. One of the most notorious instances is the outbreak of Minamata disease in Japan in 1956 that caused profound concern about mercury contamination around the world [1,2,3]. Most mercury emitted in the environment is from anthropogenic activity, such as fossil fuel power plants [4,5,6]. Later investigations revealed that different forms of mercury exhibit quite different levels of toxicity. Mercury with a methyl group (methylmercury, MeHg) is the most toxic species, the toxicity of which is around 50–100 times higher than that of inorganic mercury [7,8,9].

Methods

Results

Conclusion