珠江三角洲不同成土母质发育水稻土镉活动性差异及其影响因素

随着我国经济社会的快速发展，土壤重金属的超标问题越来越突出，尤其是Cd。土壤Cd活动性受到各种因素的影响，但成土母质对土壤Cd活动性影响的研究成果还鲜有报道。以珠江三角洲为研究区，系统采集了由第四纪沉积物、酸性侵入岩和陆源碎屑岩3种不同成土母质发育形成的水稻土样品235件，查明了土壤理化特征，探讨了Cd全量及其活动态的影响因素。结果表明：不同成土母质发育形成的水稻土理化性质、Cd全量及其活动态的影响因素存在差异。第四纪沉积物发育形成的水稻土CaO、K₂O、Na₂O、TFe₂O₃、阳离子交换量(CEC)、pH、有机质、黏粒平均含量显著高于酸性侵入岩和陆源碎屑岩，Cd超标最为严重，不同方法提取的Cd活动态含量也最高；陆源碎屑岩发育形成的水稻土中Cd全量与土壤理化指标的相关性均强于其他两类成土母质；酸性侵入岩发育形成的水稻土中Cd全量与土壤理化指标的相关性较弱。Cd全量对其活动态含量有重要影响，此外，第四纪沉积物发育的水稻土中Cd活动态含量与pH、有机质和TFe₂O₃

Differences of Cadmium Mobility in Paddy Soils from Different Parent Materials in the Pearl River Delta and Its Influencing Factors

With the rapid development of economy, heavy metals in soil exceed the environment standards more and more seriously, especially for Cd. The mobile fraction of Cd in soils is affected by various factors, but there are few reports about its influencing factors from the perspective of different parent materials. We collected and measured 235 paddy soil samples which were formed by Quaternary sediments, acid intrusive rocks and terrigenous clastic rocks in the Pearl River Delta. The physicochemical characteristics of paddy soils were summarized, and factors affecting total and the mobile fractions of Cd were discussed. The results showed that there were significant differences in physicochemical properties, total Cd concentrations of paddy soil formed by different parent materials. The average concentrations of CaO, K₂O, Na₂O, TFe₂O₃, cation exchange capacity (CEC), pH, organic matter and clay in paddy soil formed by Quaternary sediments are significantly higher than those of acid intrusive rocks and terrigenous clastic rocks. Cd in paddy soil developed from Quaternary sediments exceed the standard most seriously. Meanwhile, the concentration of Cd in mobile fractions extracted by different metho-ds in this type soil is also the highest. The correlation between the total Cd concentration and soil physicoche-mical parameters in paddy soil formed by terrigenous clastic rocks is stronger than that of the other two types of parent materials. The correlation between the total Cd concentration and soil physicochemical parameters in paddy soil formed by acid intrusive rock is weak. The total Cd concentration has an important impact on Cd in mobile fractions. In addition, the correlation between Cd in mobile fraction and pH, organic matter, TFe₂O₃ of paddy soils developed from Quaternary sediment is significantly higher than that of the other two types of parent materials. The correlation between Cd in mobile fraction and Tl, CEC, clay and Mn in paddy soil formed by terrigenous clastic rocks is significantly higher than that of the other two types of parent materials. Cd in mobile fraction is mainly affected by the total Cd,CEC, TFe₂O₃ and Mn in paddy soils formed by acid intrusive rocks.