西南地区典型土壤酸化特征及其与重金属形态活性的耦合关系

采用空间代替时间的方法，采集了西南地区主要类型和不同酸化阶段的土壤样品，分析了土壤理化性质特征、酸缓冲性能和重金属赋存形态，结合小白菜盆栽生物试验，探讨土壤酸化和重金属形态活性变化的耦合关系.结果表明，紫色土和黄壤随着土壤酸化程度增加，土壤交换性盐基离子降低，由交换性Ca²⁺流失引起.不同酸化阶段紫色土和黄壤对酸敏感性差异较大，紫色土在pH>7.50和pH<4.50时，酸缓冲容量较大；黄壤酸缓冲容量和土壤交换性盐基离子含量呈较强的相关性，且随着酸添加量增加，酸缓冲容量的增大倍数和土壤盐基离子消耗速率有关.重金属Cd和Pb在土壤中的赋存形态和土壤类型、酸化程度紧密相关，紫色土与黄壤中Cd和Pb主要以可交换态和残渣态为主，且随土壤酸化程度增加交换态占比增加，残渣态占比减少；红壤中以残渣态和Fe-Mn结合态为主，Cd的Fe-Mn结合态分别是紫色土和黄壤的2.15倍和1.73倍，Pb的Fe-Mn结合态是紫色土与黄壤的4.30倍和3.91倍，与红壤铁含量较高有关.盆栽试验表明土壤酸化一定程度上抑制小白菜的生长量，酸化严重的黄壤(pH<5.70)中小白菜生物...

Characteristics of Typical Soil Acidification and Effects of Heavy Metal Speciation and Availability in Southwest China

Using a spatial instead of temporal approach, soil samples were collected from the main types and different stages of acidification in Southwest China, and the characteristics of soil physicochemical properties, acid-buffering properties, and heavy metal fugacity patterns were analyzed, combined with biological experiments in small cabbage pots, to explore the coupling relationship between soil acidification and changes in heavy metal morphological activity. The results showed that the exchangeable salt-based ions of the soil decreased with increasing acidification in purple and yellow soils, caused by the loss of exchangeable Ca²⁺. The acid-buffering capacity of purple and yellow soils was higher at pH>7.50 and pH<4.50. The acid-buffering capacity of yellow soils was strongly correlated with the content of soil exchangeable salt-based ions, and the increase in acid-buffering capacity was related to the rate of depletion of soil salt-based ions with the increase in acid addition. The distribution of Cd and Pb in the soil was closely related to the soil type and degree of acidification: in the purple and yellow soils, Cd and Pb were mainly in the exchangeable and residue states, and the proportions of the exchangeable state and residue state increased and decreased, respectively, with increasing acidification; in the red soils, the residue state and Fe-Mn bound state were predominant; the Fe-Mn bound state of Cd was 2.15 and 1.73 times higher than that of the purple and yellow soils, respectively, and the Fe-Mn bound state of Pb was 4.30 and 3.91 times higher than that of purple and yellow soils, which was related to the higher iron content in red soils. Pot experiments showed that soil acidification inhibited the growth of Chinese cabbage to a certain extent, and the biomass of Chinese cabbage in the heavily acidified yellow soil (pH<5.70) was significantly lower than that in the non-acidified yellow soil.