The detection and monitoring of available heavy metal content in soil: A review

With the rapid development of economy and society, the problem of heavy metal contamination in soil is becoming serious increasingly, which threatens the food security and human health. However, the detection method of total concentration of heavy metal in soil can not accurately reflect the actual toxicological bioavailability of heavy metal in soil. To further analyze the existing forms of heavy metal in soil and their biotoxicity, it is necessary to assess both the existing forms and the contents of heavy metal. This article described the definition of availability of heavy metal and its transfer mechanism in soil-organism system. According to related data and documents, divided the detection methods of availability of heavy metal in soil into two kinds of methods:direct methods (chemical detection methods and physical detection methods) and indirect methods (biological indicator methods). The research progress, application scope and characteristics of chemical extraction methods, diffusive gradients in thin-films (DGT), spectrum analysis methods, plant indicator method, microbial indicator method and soil animal indicator method were systematically set forth, and the major problems of existing detection methods were summarized. At last, the paper pointed out that it was urgent to ensure food security and human health by preventing soil pollution and remediation of contaminated soil based on rapid, in-situ and non-invasive detection and monitoring of forms, contents and pollution degrees of heavy metals in soil in large-area. However, it depends on developing of more accurate detection methods by understanding the mechanism of the translocation and accumulation of heavy metal in system of soil-crop-human. In addition, the in-situ stereo detection and monitoring methods combined with remote sensing (RS), geographic information system (GIS) and global positioning system (GPS) are the hot spots of the detection and monitoring of heavy metal speciation in soil in future, and with the development of hyperspectral remote sensing technology and data processing technology, this kind of detection and monitoring methods of heavy metals can meet the requirements of large area and accurate detection and monitoring of available heavy metals contents in soil.