Abstract
Remediation of soil heavy metal by biochar has been extensively studied. However, few studies focused on the role of biochar on the co-immobilization of cadmium (Cd(II)) and arsenate (As(V)) and related soil nutrient availability. Remediation tests were conducted with three types of pristine and ferric trichloride (FeCl3) modified biochar (rice, wheat, and corn straw biochar) in Cd-As co-contaminated soil, with application rates of 1, 5, and 10% (w/w) and the incubation of 1, 7, 10, and 15 days. Using TCLP (Toxicity Characteristic Leaching Procedure) method, 10% of FeCl3 modified corn-straw derived biochar (FCB) had the highest immobilization efficiency of Cd(II) (63.21%) and As(V) (95.10%) after 10 days of the incubation. Iron-modified biochar immobilized higher fractions of water-soluble (F1) and surface-absorbed (F2) metal fractions than pristine biochar. For FCB amendment, Cd was mostly presented in the organic matter (OM) and sulfides associated (F4) and residual (F5) fractions (88.52%), as was found in the Fe-Al (oxides and hydroxides) (F3), F4, and F5 fractions (75.87%). FCB amendment increased soil pH values and available iron contents (p < 0.05), while no changes in soil available phosphorus content (p > 0.05). This study showed that FCB application reduces the environmental mobility of metals in Cd-As contaminated soil, while it also increases soil pH and available nutrient mobility, improving soil environmental quality and reducing remediation costs.
Highlights
As a non-essential element, cadmium Cd (II) is toxic to organisms at a trace concentration [1].Excessive Cd(II) in soil is a risk to the food crops but higher organisms through the trophic transfer along the terrestrial food chain [1]
Debris and impurities adhere to the surface of biochar
Significant peaks of Fe from Fe-modified biochar were shown in Figure 1c,f,m, and they were confirmed by the elementary composition analysis
Summary
Excessive Cd(II) in soil is a risk to the food crops but higher organisms through the trophic transfer along the terrestrial food chain [1]. Oxyanions in soil and organisms are well described [2]. Due to the mining activities and pesticide usage, the co-contamination of Cd and As in soil poses serious threats to food safety [4]. Remediation of these co-contaminated soils has been an important issue for maintaining agriculture activities [5]. Due to the opposite chemical characteristics of Cd(II) and As(V), it is critical to find an efficient method for simultaneous remediating these co-contaminants
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