Heavy metals in soils

Chemical stabilization remediation for heavy metals in contaminated soils on the latest decade: Available stabilizing materials and associated evaluation methods－A critical review

Intercropping improves heavy metal phytoremediation efficiency through changing properties of rhizosphere soil in bamboo plantation

Biochar-bacteria-plant partnerships: Eco-solutions for tackling heavy metal pollution.

Mechanism of microbial dissolution and oxidation of antimony in stibnite under ambient conditions.

Soil stabilization is a remedial technique that reduces the exposure of the soil environment to soil contaminants. Its efficacy can be assessed by determining whether the environmental availability of a contaminant decreases following treatment. We evaluated several chemical leaching treatments by assessing both contaminant leachability and bioaccumulation in the earthworm Eisenia fetida, and determined the most effective treatment for achieving soil stabilization. Soil samples contaminated with As, Cd, Cu, Pb, and/or Zn were collected from abandoned mine areas and stabilized by adding limestone and steel slag (5% and 2% w/w, respectively). All leaching and earthworm tests were conducted using both contaminated and stabilized soils. In addition to bioaccumulation in earthworms, several toxicity parameters (number of cocoons, growth changes, and survival rates) were also assessed to determine the effects of the treatments on the earthworms. The study showed that treatment of soil with EDTA-NH4OAc resulted in a significant decrease in contaminant leachability following soil stabilization. There was an increase in survival and growth of earthworms exposed to the stabilized soil compared with those exposed to the non-stabilized soil. Bioaccumulation in earthworms was found to be statistically correlated with the leachability of As by EDTA-NH4OAc. We conclude that limestone and steel slag effectively decreased the availability of heavy metals in the soil and reduced the toxicity to earthworms. Leaching with EDTA-NH4OAc has the potential to be predictive in estimating the bioavailability of As in soils, but further studies are needed if it is to be proposed as a standard method.

Assessment of the stabilization of heavy metal contaminants in soils using chemical leaching and an earthworm bioassay

The remediation of soil contaminated with heavy metals is an ongoing environmental concern. Paddy soils contaminated with Cd and Zn were collected from around abandoned metals mines in Korea. Limestone and steel slag were mixed with the collected soil, as amendments for Cd and Zn immobilization. Sequential extraction, lettuce cultivation and five single extraction methods were carried out to assess the effects on Cd and Zn immobilization using amendments. The exchangeable fraction of Cd and Zn was decreased and Fe-Mn oxides fraction increased by stabilization using amendments. In addition, the accumulation of Cd and Zn in lettuce decreased in treated soil and indicated the Cd and Zn immobilization effect in soil by the amendments. The extractable Cd and Zn by CaCl2 and Mehlich-3 in the untreated soils were higher than that of treated soils, whereas Cd and Zn extraction by ethylenediaminetetraacetic acid (EDTA), diethylene tetramine penta-acetic acid (DTPA) and toxicity characteristic leaching procedure (TCLP) has a small or no difference between the untreated and treated soils. The extraction results by CaCl2 and Mehlich-3 methods present reasonable results for Cd and Zn immobilization in soil than EDTA, DTPA and TCLP methods. Therefore, the choice of appropriate extraction method is very important when there is the assessment of Cd and Zn immobilization efficiency.

Comparison of five extraction methods for evaluating cadmium and zinc immobilization in soil

Possibility of bacterial leaching of antimony, chromium, copper, manganese, nickel, and zinc from contaminated sediment

Effect of tungsten-resistant bacteria on uptake of tungsten by lettuce and tungsten speciation in plants.

Environmental geochemists have attempted to select proper soil extraction methods that deeply reflect the bioavailability, phytoavailability, and geochemical mobility of elements for the assessment of heavy metal contamination in soil. However, they are faced with complications during the process due to the complexity of heavy metal forms in soil and diversity in existing soil extraction methods. The present study summarizes the information on soil contaminated with heavy metals in Korea and current research trends on various single and sequential extraction techniques through a literature survey. This work is expected to serve as a fundamental reference for researchers to select an appropriate extraction method for evaluating bioavailability, phytoavailability, and geochemical mobility of heavy metals in soil.

Hyeop-Jo Han

Papers

Assessment of the stabilization of heavy metal contaminants in soils using chemical leaching and an earthworm bioassay

Comparison of five extraction methods for evaluating cadmium and zinc immobilization in soil

Possibility of bacterial leaching of antimony, chromium, copper, manganese, nickel, and zinc from contaminated sediment

Effect of tungsten-resistant bacteria on uptake of tungsten by lettuce and tungsten speciation in plants.

Study on Soil Extraction Methods for Contamination Assessment of Heavy Metals in Soil