Evaluation of Two Amendments (Biochar and Acid Mine Drainage Sludge) on Arsenic Contaminated Soil Using Chemical, Biological, and Ecological Assessments.

Min-Suk Kim,Sang-Hwan Lee,Hyun Park,Jeong-Gyu Kim

doi:10.3390/ma14154111

Abstract

Various types of organic and inorganic materials are widely examined and applied into the arsenic (As) contaminated soil to stabilize As bioavailability and to enhance soil quality as an amendment. This study deals with two types of amendments: biochar for organic amendment and acid mine drainage sludge (AMDS) for inorganic amendment. Each amendment was applied in two types of As contaminated soils: one showed low contaminated concentration and acid property and the other showed high contaminated concentration and alkali property. In order to comprehensively evaluate the effect of amendments on As contaminated soil, chemical (As bioavailability), biological phytotoxicity (Lactuca sativa), soil respiration activity, dehydrogenase activity, urease activity, ß-glucosidase activity, and acid/alkali phosphomonoesterase activity, an ecological (total bacterial cells and total metagenomics DNA at the phylum level) assessment was conducted. Both amendments increased soil pH and dissolved organic carbon (DOC), which changes the bioavailability of As. In reducing phytotoxicity to As, the AMDS was the most effective regardless of soil types. Although soil enzyme activity results were not consistent with amendments types and soil types, bacterial diversity was increased after amendment application in acid soil. In acid soil, the results of principal component analysis represented that AMDS contributes to improve soil quality through the reduction in As bioavailability and the correction of soil pH from acidic to neutral condition, despite the increases in DOC. However, soil DOC had a negative effect on As bioavailability, phytotoxicity and some enzyme activity in alkali soil. Taken together, it is necessary to comprehensively evaluate the interaction of chemical, biological, and ecological properties according to soil pH in the decision-making stages for the selection of appropriate soil restoration material.

Highlights

A soil amendment is any materials added to soil to improve soil quality and to achieve the goal of improvement
Kim et al [9] investigated the applicability of acid mine drainage sludge (AMDS) in trace elements contaminated soil by using chemical and biological assessments and it was reported that AMDS effectively reduced the mobility and bioavailability of trace elements
In order to evaluate the leaching possibility from AMDS, Korea standard leaching test (KSLT) was conducted [23] and the results showed that only Pb is detected at 0.01 mg L−1 [16]

Summary

Introduction

A soil amendment is any materials added to soil to improve soil quality and to achieve the goal of improvement. The soil amendments are often used for remediation of arsenic (As) contaminated soil as a stabilizer of As in soil through the formation of insoluble fraction and the decreases in mobility, bioavailability, and toxicity [1]. The most common form of iron oxides includes ferrihydrite, hematite, goethite, and lepidocrocite and these adsorption sites decreases as a density of adsorption sites are diminished with the crystallization process [5]. In oxidizing conditions such as the environment near an abandoned mine, As is mainly present in the form of arsenate (V) and it binds to iron oxide minerals as an inner-sphere complex such as bidentate and binuclear surface complex [6]. Industrial by-products exhibit high efficiency with respect to the immobilization of As, they inevitably contained toxic trace elements, resulting in environmental ecotoxicology risk

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