Bioavailability Assessment of Heavy Metals Using Various Multi-Element Extractants in an Indigenous Zinc Smelting Contaminated Site, Southwestern China.

Jun-Xian Wang,Da-Mao Xu,Rong-Bing Fu,Jia-Peng Chen

doi:10.3390/ijerph18168560

Abstract

Despite recent studies have investigated the strong influences of smelting activities on heavy metal contamination in the soil environment, little studies have been conducted on the current information about the potential environmental risks posed by toxic heavy metals in smelting contaminated sites. In the present study, a combination of the bioavailability, speciation, and release kinetics of toxic heavy metals in the indigenous zinc smelting contaminated soil were reliably used as an effective tool to support site risk assessment. The bioavailability results revealed that the bioavailable metal concentrations were intrinsically dependent on the types of chemical extractants. Interestingly, 0.02 mol/L EDTA + 0.5 mol/L CH3COONH4 was found to be the best extractant, which extracted 30.21% of Cu, 31.54% of Mn, 2.39% of Ni and 28.89% of Zn, respectively. The sequential extraction results suggested that Cd, Pb, and Zn were the most mobile elements, which would pose the potential risks to the environment. The correlation of metal bioavailability with their fractionation implied that the exchangeable metal fractions were easily extracted by CaCl2 and Mehlich 1, while the carbonate and organic bound metal fractions could be extracted by EDTA and DTPA with stronger chelating ability. Moreover, the kinetic modeling results suggested that the chemical desorption mechanism might be the major factor controlling heavy metal release. These results could provide some valuable references for the risk assessment and management of heavy metals in the smelting contaminated sites.

Highlights

Heavy metal contamination around mining and smelting sites have received global concern [1,2]
The results indicated that the heavy metal enrichment was mainly caused by the long-term smelting activities
28.39–33.88%, 10.62–14.48%, 17.81–32.55%, 31.20–36.93%, and heavy metals determined by seven chemical extractants in the indigenous zinc smelting

Summary

Introduction

Heavy metal contamination around mining and smelting sites have received global concern [1,2]. Many studies have reported that toxic heavy metals, such as, Cd, Pb, and Zn, have posed the potential risks to the ecosystem and human health around the smelting areas [5,6]. The risk assessment of heavy metal pollution in the smelting contaminated sites is an important task and challenge for the sustainable development of non-ferrous metal smelting industry [7,8]. It is well acknowledged that heavy metal toxicity depends on their geochemical fractions based on the bioavailability and sequential extraction method instead of their total contents in soils [9,10,11]. The previous studies are mostly concentrated on the total metal concentrations in soil near smelters to assess the potential risks resulted

Objectives

Methods

Results

Conclusion