The role and effect of applying attapulgite to controlling Cd-contaminated soil

Abstract: Attapulgite is a kind of clay mineral of Mg-rich silicate, and it also constitutes a kind of abundant non-metallic mineral resources in Jiangsu Province. As a kind of chemical remediation or immobilization material to tackle Cd-contaminated soil, its advantage in controlling heavy metal mobility is quite obvious. On the basis of choosing typical Cd-contaminated sites from vegetable garden and paddy land, a preliminary control test was systematically conducted to treat soil pollution of heavy metals so as to apply some doses of attapulgite powder in the southern area of Jiangsu Province. The related test data and controlling effect are reported in this paper to decrease Cd content of vegetable and rice from Cd-contaminated sites. Some conclusions have been reached: (1) when Cd concentration is 0.3-0.45 mg/kg in soil of the site, Cd content of vegetable can be decreased by 30% or so by applying attapulgite powder in excess of 750 g/m2 , and maximum effective applying dose is 1500 g/m2 to contaminated soil annually; (2) when Cd concentration is about 3 mg/kg and pH is lower than 6.5 in soils of the site, Cd content of rice can be dramatically decreased from more than 0.5 mg/kg to less than 0.2 mg/kg after 2 years’ application of attapulgite powder in excess of 2000 g/m2 to polluted soil annually, and there are distinct negative correlated relationship between Cd content of rice and pH in polluted soil, with the correlation coefficient being -0.95; (3) the significance of applying attapulgite to the above-mentioned polluted soil is obvious in elevating pH values and cation exchange capacity (CEC), and at the same time the element concentrations of Cu and Zn can be decreased in the vegetable or rice samples. It is thus held that the prospect of applying attapulgite to soil should be relatively huge or wide in curing Cd-contaminated lands.