ABSTRACT
The impact of heavy metal contamination on soil health Santanu Bakshi and Chumki Banik, Iowa State University, USA; and Zhenli He, University of Florida, USA
1 Introduction
2 Current levels of soil contamination by heavy metals
3 Natural and anthropogenic sources of heavy metals
4 Chemical transformation of heavy metals in soils
5 Bioavailability of heavy metals in soils
6 Effects of heavy metals on soil health: soil chemistry, biochemistry and microbiology
7 Effects of heavy metals on plant health and crop production
8 Indicators of soil contamination
9 Remediation of contaminated soil
10 Conclusions and future trends
11 References
Heavy metals are ubiquitous in the earth’s environment and can result from both anthropogenic and natural activities (He et al., 2005b). Industrialization, urbanization and intensified agriculture are the main causes of heavy metal contamination of soils and the environment. Heavy metals are elements with metallic properties, a density of >5 g cm−3 and an atomic mass of >20. The most common heavy metals in the environment are (He et al., 2015b):
• arsenic (As) • cadmium (Cd) • chromium (Cr) • copper (Cu) • mercury (Hg)
• lead (Pb) • zinc (Zn)
According to Iimura et al. (1977), half-lives (in years) of Zn, Cd, Cu and Pb are 70-510, 13-1100, 310-1500 and 740-5900, respectively, whereas Bowen et al. (1979) estimated residence times (in years) of 75-380 for Cd, 500-1000 for Hg and 1000-3000 for Cu, Ni, Pb and Zn under temperate climatic conditions (Kabata-Pendias, 2011).
