Assessing mercury pollution at a primary ore site with both ancient and industrial mining and smelting activities

Bin Zhao; David O'Connor; Hao Zhang; Yuanliang Jin; Yidong Wang; Xiaodong Yang; Renjie Hou; Deyi Hou

doi:10.1016/j.envpol.2023.122413

Assessing mercury pollution at a primary ore site with both ancient and industrial mining and smelting activities

Environ Pollut. 2023 Nov 1:336:122413. doi: 10.1016/j.envpol.2023.122413. Epub 2023 Aug 18.

Authors

Bin Zhao¹, David O'Connor², Hao Zhang³, Yuanliang Jin⁴, Yidong Wang⁴, Xiaodong Yang⁴, Renjie Hou⁵, Deyi Hou⁶

Affiliations

¹ Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou, 510650, China; School of Environment, Tsinghua University, Beijing, 100084, China.
² School of Real Estate and Land Management, Royal Agricultural University, Stroud Rd, Cirencester, GL7 6JS, United Kingdom.
³ Technical Centre for Soil, Agriculture and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing, 100012, China.
⁴ School of Environment, Tsinghua University, Beijing, 100084, China.
⁵ School of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin, Heilongjiang, 150030, China.
⁶ School of Environment, Tsinghua University, Beijing, 100084, China. Electronic address: houdeyi@tsinghua.edu.cn.

PMID: 37598928
DOI: 10.1016/j.envpol.2023.122413

Abstract

The Minamata Convention on Mercury has mandated a renewed global effort to tackle Hg pollution. The present study evaluates Hg pollution at a primary Hg production site exploited since the Qin Dynasty (200s BC), with intensive industrial scale production over the past four decades. This single location accounts for over 95% total Hg production in China in recent years. To assess the environmental risk and effectiveness of recently implemented control measures, we collected 90 soil samples, 60 plant tissue samples, 47 sediment samples, and 47 river water samples from the site and its vicinity. A site-specific conceptual site model was established based on the sources, migration transformation pathways of Hg pollutant and its exposure scenarios. The maximum soil Hg concentration reached 10,451 mg kg^-1, posing a high health and ecological risk. Vegetable and crop Hg concentrations outside the site reached 0.23 mg kg^-1 in rice grains and 4.24 mg kg^-1 in green onion. The highest health risk, with a hazard quotient of 130.66, was observed in the Ore Storage Site, which reduced to 17.14 when Hg bioavailability was considered. Risk control measures implemented in recent years included a stormwater collection system and capping of the tailing pond area with clean imported soil. These measures were generally successful; however, Hg in the tailings were found to be contaminating the imported surficial soil due to rainfall saturation and upward migration, suggesting a need for long-term post remedial site monitoring and maintenance. We also found that mining and smelting activities have contaminated a 6 km stretch of a nearby river, with sediment Hg concentrations reaching 2819 mg kg^-1, and water column concentrations reaching 193.21 ng L^-1. The sediment and water concentrations are highly correlated (R² = 0.78), suggesting that, with risk control measures in place, a reservoir of Hg in polluted river sediment is now driving pollution in the water column. This work demonstrates that primary Hg mining has caused widespread and serious soil and water pollution. Risk control measures can reduce human health and ecological risks, but robust monitoring and maintenance are required for remediation to be effective in the long-term.

Keywords: Contaminated soil; Health risk assessment; Mercury; Primary mercury mining; Risk management.