盐渍化与酸化对设施栽培土壤镉活化的叠加作用

为深入了解同时发生盐渍化和酸化对设施栽培土壤镉活性的影响,采用模拟试验方法研究不同pH、盐分种类和盐分积累程度下土壤中水溶性镉及蔬菜对镉吸收的变化。结果表明,土壤中水溶性镉含量和蔬菜地上部分镉积累量均随土壤酸化与盐渍化程度的提高而增加。当土壤pH值为5.00~5.50时,土壤水溶性镉含量随盐渍化增加的变化最为明显。当土壤镉含量为0.55 mg·kg^-1、盐分积累量为2.50 g·kg^-1时,在土壤pH值分别为6.15、5.50和5.00的条件下,土壤水溶性镉含量分别较对照(未盐化)增加10.53%、44.00%和51.06%,蔬菜镉含量分别较对照(未盐化)增加20.00%、16.85%和36.36%,当土壤pH值由6.15降低至4.00后,土壤水溶性镉和蔬菜地上部分镉含量分别提高了近4倍和8倍。土壤镉活化因盐分离子种类不同而异:阳离子的影响程度为Ca²⁺、Mg²⁺>K⁺>NH4+,阴离子的影响程度为Cl^->SO42->NO3-。土壤中水溶性镉和蔬菜对镉的吸收同时随酸化和盐渍化增强而增加的结果表明,土壤盐渍化和酸化对镉的活化具有叠加作用。

Combined effects of salinization and acidification on cadmium activation in greenhouse soil

Soil salinization and acidification are common in greenhouse soil. Both of them could change the balance of chemical elements in soil, and thus affect the chemical behavior of heavy metals in soil. To understand the effects of simultaneous salinization and acidification on Cd activity in greenhouse soil, changes of soil water-soluble Cd in soil and Cd uptake by vegetable as functions of soil pH, salinity and salt accumulation were observed using simulation experiments. It was shown that water-soluble Cd content in soil and Cd accumulation in upper parts of vegetable increased obviously with the increase of soil acidification and salinization. The change of soil water-soluble Cd concentration in soil with increasing salinity was most obvious at pH 5.00-5.50. For soil with total Cd of 0.55 mg·kg^-1 and soil salinity of 2.50 g·kg^-1, the concentrations of water-soluble Cd in soil increased by 10.53%, 44.00% and 51.06% , respectively, under pH of 6.15, 5.50, and 5.00, as compared with the control soil without salinization. Correspondingly, Cd accumulation in upper parts of vegetable increased by 20.00%, 16.85% and 36.36%, respectively. Meanwhile, concentration of water-soluble Cd in soil and Cd content in the upper parts of vegetable increased by about 4 and 8 times of the control, respectively, when soil pH was reduced from 6.15 to 4.00. The activation of Cd in soil varied with ion composition of salt, and the effect decreased in the order of Ca²⁺,Mg²⁺>K⁺>NH4+ for cation, and Cl^->SO42->NO3- for anion. The results suggested that acidification and salinization occurred simultaneously in the protected soil could significantly increase the activity of soil cadmium. Those two processes had a superimposed effect on the activity of soil Cd.