草酸对镉污染土壤油葵生物量及土壤酶活性和镉形态的影响

探究草酸浓度与施入时间对Cd污染土壤酶活性、Cd形态及油葵生物量的影响。采用盆栽试验,以油葵为供试植物,研究了不同草酸施用浓度(1、2、3、4、5 mmol·kg~(-1)和6 mmol·kg~(-1))和施入时间(出苗后20、30、40、50 d)对土壤酶活性、油葵干物质量及土壤Cd形态的影响。结果表明,施用草酸提高了土壤过氧化氢酶和蔗糖酶活性,比CK分别提高4%～84.4%和2%～147%。草酸提高了油葵地上部分及根干生物量,比CK处理分别提高7%～126%和11.4%～139%;施用2～3 mmol·kg~(-1)浓度草酸,地上部和根干质量较高,在出苗后30～40 d时施入草酸,地上部和根干质量较高。草酸降低了土壤可交换态、铁锰氧化物结合态及有机物结合态Cd浓度;施入2～3 mmol·kg~(-1)浓度草酸,土壤可交换态、铁锰氧化物结合态及有机物结合态Cd浓度较低,在出苗后30～40 d时施加草酸,可交换态、铁锰氧化物结合态及有机物结合态Cd浓度较低。在油葵出苗后30 d时施入4 mmol·kg~(-1)浓度草酸,土壤Cd去除率最高,相比CK提升89.2%;草酸可有效提高油葵修复Cd污染土壤能力,具有一定的应用潜力。

Effects of oxalic acid on oil sunflower biomass, enzyme activity, and the Cd speciation of Cd-polluted soils

The effects of oxalic acid concentration and application time on the soil enzyme activity, dry matter content of oil sunflower, and content of different forms of Cd in Cd-polluted soils were studied using a pot experiment, with sunflowers as the test plant. The effects of different oxalic acid concentrations(i.e., 1, 2, 3, 4, 5, and 6 mmol·kg^-1)and application times(i.e., 20, 30, 40, and 50 days after emergence)on soil pH, enzyme activity, and the dry matter content of oil sunflowers and content of Cd in different forms was analyzed in this study. The results indicated that the application of oxalic acid promoted the activities of catalase and invertase in the soil, which were 4%~84.4% and 2%~147% higher than that of treatment without oxalic acid(CK). The application of oxalic acid could also improve the dry weight of the above-ground part and root of oil sunflower; it was 7%~126% and 11.4%~139% higher than that of CK. The dry weights of the above-ground parts and root of sunflowers were the highest at acid concentrations of 2~3 mmol·kg^-1 and application times of 30~40 days. Oxalic acid also reduced the exchangeable, Fe-Mn oxide and organic matter-bound Cd content in the soil. These exchangeable, bound Cd contents were the lowest in the rhizosphere soil at acid concentrations of 2~3 mmol·kg^-1 and application times of 30~40 days. When oxalic acid was applied at a concentration of 4 mmol·kg^-1 30 days after the emergence of oil sunflowers, the rate of Cd removal in the rhizosphere soil was maximized at 88.4%, higher than that of CK. Therefore, oxalic acid could be used to effectively improve the ability of oil sunflowers to repair Cd-polluted soils, which has potential for soil remediation applications.