伴矿景天植物汁液还田对土壤重金属形态及植物吸收的影响

超积累植物伴矿景天在Cd和Zn污染土壤修复方面展现出广泛应用前景,但收获物压榨脱水后产生的含重金属汁液处理是目前亟待解决的问题。选用酸性和中性土壤,通过盆栽试验将不同剂量的伴矿景天汁液还田并种植伴矿景天,监测土壤中pH、可溶性有机碳(DOC)浓度和CaCl₂提取态Cd与Zn(CaCl₂-Cd/Zn)浓度动态变化及植物生长和重金属再吸收情况。结果表明:添加汁液后7和30 d,酸性土壤pH升高而中性土壤pH降低,2种土壤中DOC浓度均显著升高;生长中后期土壤pH、DOC浓度与不添加汁液的对照接近;汁液处理的酸性土壤中CaCl₂-Cd/Zn浓度随着生长时间延长逐步升高,在第105天达最高,而中性土壤中浓度呈现逐步降低趋势;汁液处理使伴矿景天生长受到抑制,生物量降低,但其地上部Cd浓度升高;酸性土壤用100 mL/kg汁液处理,伴矿景天地上部Cd和Zn吸收量大于汁液带入量,修复后土壤Cd和Zn浓度低于原土的本底值。因此,酸性土壤适当剂量汁液还田并种植伴矿景天,可将汁液带入的Cd和Zn再次吸收去除,达到汁液处理和净化土壤的双重目的。

Effect of Sedum plumbizincicola liquor returning to soils on the speciation and phytoextraction of heavy metals

Sedum plumbizincicola, a hyperaccumulator, has been widely used in the remediation of cadmium and zinc polluted soils, but the treatment of the crop liquor which contains heavy metals after squeeze and dehydration of harvest biomass is an urgent problem to be solved. Choosing acidic and neutral soils, a pot experiment was conducted to return different doses of liquor to two types of soils and to grow Sedum plumbizincicola. The dynamic changes of soil pH, dissoluble organic carbon (DOC), CaCl2 extractable Cd and Zn (CaCl2-Cd/Zn), as well as plant growth and heavy metal reabsorption were monitored. The results showed that the pH increased in acid soil but decreased in neutral soil, and the DOC concentration of both soils increased significantly on 7 and 30 d after the addition of liquor, while the soil DOC concentration and pH were closed to the controlled soil in the middle and late growth stages. The CaCl2-Cd/Zn concentrations in acid soil treated with liquor increased gradually with growing time, and reached maximum on 105 d, while those in neutral soil showed a gradual decline. The liquor treatment inhibited the growth of Sedum plumbizincicola with reduced biomass, but increased the concentration of Cd in the shoots. With 100 mL/kg liquor treatment of acid soil, Cd and Zn accumulation in Sedum plumbizincicola shoot was higher than the input by addition of liquor, and the soil Cd and Zn concentrations after remediation were lower than soil initial values before liquor addition. Consequently, suitable dosage of liquor returning to the acid soil and planting Sedum plumbizincicola could remove Cd and Zn input by liquor again and achieve the dual purpose of liquor treatment and soil remediation.