大气中CO2体积分数升高对污染土壤中Cu、Cd形态分布及其生物活性的影响

采用OTC-1型开顶式培养箱,模拟研究了CO2体积分数升高对2种小麦的生长以及根际、非根际中Cu和Cd形态分布的影响.结果表明,CO2体积分数的升高显著提高了小麦地上部和地下部生物量,降低了小麦根际和非根际的pH值.临麦2号和宁麦8号小麦地上部干重分别增加了36.9%和25.2%,地下部干重则分别增加了55.1%和59.7%.此外,CO2体积分数升高对不同重金属形态分布的影响随小麦品种和重金属种类的不同而异.在高CO2体积分数条件下,可交换态(F1)Cu和Cd含量显著提高,其中临麦2号根际土壤可交换态Cu和Cd含量分别较对照增加10.6%和29.6%,宁麦8号根际土壤可交换态Cu和Cd分别较对照增加11.0%和20.3%;碳酸盐结合态(F2)Cu和Cd均有所降低,其中宁麦8号和临麦2号根际Cu降低均达极显著(分别降低73.6%和50.0%);铁锰氧化物结合态(F3),有机结合态(F4)和残渣态(F5)Cu和Cd在CO2体积分数升高情况下变化较小.同时CO2体积分数升高还显著增加了2种小麦地上部和地下部铜累积量,增加了临麦2号地上部和地下部镉累积量和宁麦8号地上部镉累积量,但对宁麦8号地下部镉累积量无显著影响.

Effects of elevated CO2 on fractions and bioactivity of copper and cadmium in contaminated soil

A pot experiment with an open-top chamber (OTC) was conducted to investigate the effects of elevated CO₂ on soil copper and cadmium fractions and their bioaccumulation in two wheat (Tritium aestivum L.) cultivars (cv. Ningmai No.8, and Linmai No.2) grown in a yellow-brown soil amended with sewage sludge. The results showed that both shoot and root weight increased significantly with the elevation of CO₂. At the same time, the significant decrease in soil pH was also found with the elevation of CO₂. The shoot weight of Linmai No.2 and Ningmai No.8 in the treatment with elevated CO₂ (+300×10^-6 CO₂) increased by 36.9% and 25.2%, respectively, and root weight by 55.1% and 59.7%, respectively, compared with the control. Treatment with elevated CO₂ (+300 ×10^-6 CO₂) increased exchangeable fractions of Cu and Cd, but decreased carbonate-bound fractions of Cu and Cd significantly. However, elevated CO₂ had no effects on Fe-Mn-bound, organic-bound or residual Cu and Cd in rhizosphere or non-rhizosphere soils. Meanwhile, elevated CO₂ significantly increased Cu accumulation in the shoots and roots of both wheat cultivars, and Cd accumulation in the shoots and roots of cultivar Linmai No.2 and in the shoots of cultivar Ningmai No.8, but no significant difference was observed in Cd accumulation in the roots of cultivar Ningmai No.8.