A Comparative Study of the Capacity of Different Extractants to Extract Heavy Metals in Soil

The extraction capacity of different extractants, the species distribution of heavy metals in different multi-stage extraction methods, and the relationship between the extracted heavy metal content and the species distribution of heavy metal were investigated in detail. Several classical extractants, including deionized water (DI), sulfuric acid-nitric acid (AA), diethylenetriaminepentaacetic acid (DTPA), toxicity characteristic leaching procedure (TCLP), and calcium chloride (CC) were used to detect the content of available heavy metals in soil contaminated in combination with Cu, Ni, Pb and Cd. Furthermore, the BCR sequential extraction proposed by European Community Bureau of Reference and Sequential Extraction Procedures (SEP) were carried out to analyze the species distribution of heavy metals in the contaminated soil. The results showed that the extraction capacity of each extractant ranks from strong to weak as DTPA, TCLP, CC, AA, DI. The content of active components extracted with the BCR method is similar to that extracted with the SEP method. The content of heavy metals leached with TCLP is closely related to the form of heavy metals in BCR. The availability of heavy metals in TCLP extraction was an acid extractable fraction. The content of heavy metals leached with DTPA is also closely related to the form of heavy metals in SEP. The availability of heavy metals in DTPA extraction was exchangeable, bound to carbonates and Fe-Mn oxide-bound. This study can improve the evaluation methodology of soil heavy metal pollution.