不同改良剂对污染土壤中Cd形态影响的研究

Effects of Various Amendments on the Fractions of Cadmium in a Polluted Soil

采用室内培养试验，研究了4种改良剂对污染土壤中Cd形态的影响。外源添加cd的土壤中，重金属cd主要以可交换态cd的形式存在，所占比例为全量的35．2％～44．0％。施加改良剂可在一定程度上增加土壤pH值，从而影响土壤中cd的形态分布，其影响效果为改良剂1〉改良剂4〉改良剂3〉改良剂2。施加改良剂并在室温下培养35d后，土壤中cd形态分布发生了明显的变化。在1mg·kg。和10mg·kg。的cd污染土壤中，可交换态cd含量降低，残渣态cd含量增加，而在5mg·kg。的cd污染土壤中，残渣态cd含量降低，可交换态cd含量增7311；培养过程中碳酸盐结合态cd和铁锰氧化物结合态cd含量并未产生较大变化，土壤中有机质结合态cd所占比例非常小，改良剂施用对其含量的影响也不明显。总体上来讲，改良剂的施用可使土壤cd由可交换态向残渣态转化，Cd的生物有效性降低。

Amendments have been widely applied to remediate heavy metal polluted soils. In this paper, an experiment was conducted in laboratory to study the effects of four different amendments on the fractions of Cd in a polluted soil. The main fraction of Cd was exchange- able and its percentage was 35.2%~44.0% of the total Cd in soil. Addition of amendments increased soil pH to some extent, thereby affect- ing the distribution of Cd fractions in the soil, with the order of #1 〉#4〉#3〉#2. Compared with the control treatment, the four types of amend- ments remarkably reduced the exchangeable Cd concentrations and increased the residual Cd concentrations after 35-days incubation, at slight pollution of Cd （ 1 mg. kg-1） and high Cd concentration （ 10 rag＂ kg-I ）, on the contrary, the exchangeable concentrations increased and the T＇esidual concentration reduced at Cd contaminated soil of 5 mg＇ kg-j. During the process of incubation, carbonate-bound Cd and Fe-Mn oxide-bound Cd scarcely transformed. As the experiment carried on, the exchangeable Cd concentration increased at first and reduced after- wards, oppositely, the residual Cd concentration firstly reduced then increased but reduced overall. Carbonate-bound, Fe-Mn oxide-bound and organic-bound Cd did not transform as much as exchangeable and residual Cd. In other words, the transformation of Cd fractions caused by the amendments was mainly between exchangeable Cd and residual Cd, and this led to the decline of Cd bioavailability.