钙对土壤镉有效性的影响及其机理

采用盆栽试验，研究了赤红壤上两种镉污染水平下，施用4种钙量（0、40、100、200 mg·kg^-1）对小油菜生物量、镉吸收量及土壤溶液中钙、镉浓度的影响.结果表明：在低镉或者高镉污染水平下，与对照相比，小油菜干质量均以高钙用量处理的增幅最大，两季平均增加了5.5%（低镉）和17.3%（高镉）;增加钙的施用量，使土壤溶液中钙浓度明显增加，小油菜体内钙浓度也明显增加;当钙施用量为100 mg·kg^-1时，土壤溶液中镉浓度较对照分别增加74.5%（低镉）和31.0%（高镉），而小油菜体内镉浓度较对照分别降低4.5％（低镉）和13.1％（高镉）.两种镉污染水平下，土壤溶液中钙/镉（质量比）值与小油菜体内镉浓度均呈显著正相关.土壤溶液中钙/镉比值影响土壤镉的有效性，进而影响小油菜对镉的吸收.

Effects of calcium on cadmium bioavailability in lateritic red soil and related mechanisms

A pot experiment with Cd-polluted lateritic red soils was conducted to study the effects of applying different concentration (0, 40, 100, and 200 mg·kg-1) Ca on the rape biomass, its Cd uptake, and the Ca and Cd concentrations in soil solution. Comparing with no Ca application, applying Ca increased the rape dry mass, whether under high or low level Cd pollution. The increment of the dry mass in two cropping seasons was averagely 5.5% (low level Cd pollution) and 17.3% (high level Cd pollution). The Ca concentration both in soil solution and in rape plant increased markedly with increasing Ca application rate. At the Ca application rate 100 mg·kg-1, the Cd concentration in soil solution increased by 74.5% (low Cd pollution) and 31.0% (high level Cd pollution), while that in rape plant decreased by 4.5% (low Cd pollution) and 13.1% (high level Cd pollution). There was a positive relationship between the Ca/Cd (mass ratio) in soil solution and the Cd concentration in rape plant under both low and high levels Cd pollution. The Ca/Cd (mass ratio) in soil solution affected the bioavailability of soil Cd, and further, affected the Cd uptake by rape.