水淹生境下秋华柳对Cd污染土壤微生物数量及酶活性的影响

Effects of Salix variegata on soil microorganisms and enzymatic activity in contaminated soils under flooding conditions

三峡库区消落带面临水淹及Cd污染双重胁迫,为探究秋华柳(Salix variegata Franch.)在水淹条件下对Cd污染土壤的修复能力,以秋华柳扦插苗为试验材料,设置正常供水(CK)和水淹组(FL)两个水分处理方式,4个Cd浓度梯度:对照组(0mg/kg)、低浓度(0.5mg/kg)、中浓度(2mg/kg)及高浓度(10mg/kg),分别对处理60 d和120 d的土壤微生物数量及酶活性变化特征进行研究。试验结果表明:(1)Cd浓度处理均未显著影响土壤微生物数量(P>0.05),水淹显著降低处理60 d土壤细菌数、真菌数及处理120 d的土壤放线菌数及真菌数(P<0.05)。(2)种植秋华柳显著提高处理60 d土壤细菌数量(P<0.05),对土壤放线菌、真菌数量也有一定提升。(3)Cd浓度处理显著影响处理60 d土壤磷酸酶活性及处理120 d脲酶活性(P<0.05),水淹显著降低处理60 d土壤磷酸酶活性及处理120 d脲酶、蔗糖酶和磷酸酶活性(P<0.05)。(4)正常供水及水淹条件下,种植秋华柳对土壤酶活均有一定改善作用。种植秋华柳显著提高了处理60 d土壤磷酸酶活性以及处理120 d脲酶和蔗糖酶活性(P<0.05)。研究结果表明:水淹生境中,秋华柳对Cd污染土壤微生物数量及酶活性具有改善作用,在Cd污染土壤修复方面有一定应用前景。

The altered water regime and cadmium pollution in the Three Gorges Reservoir of the Yangtze River, China, has caused many serious environmental problems. Consequently, it is of great importance to restore the riparian vegetation and soil. Salix variegata is potentially a suitable species for the phytoremediation of Cd-contaminated areas under environmental flooding conditions. To determine the microorganism community and enzymatic activity in Cd-contaminated soils under flooding conditions, an experiment with a factorial design was conducted. Treatments included two water regimes and four Cd concentrations. The water treatments were ambient water supply （CK） and light flooding （FL）. In terms of cadmium, there was a control （0 mg/kg）, and cadmium treatments with low （0.5 mg/kg）, moderate （2 mg/kg）, and high concentrations （10 mg/kg）. Each cadmium treatment was conducted with and without S. variegata. Soil samples were collected on the 60^th and 120^th day following treatment, and the characteristics of soil microorganisms and enzymatic activities were determined. The results showed that： （1） S. variegata plantings significantly increased the quantity of bacteria in the soils on the 60^th day （P 〈 0.05） and slightly increased the quantity of actinomycetes and fungi. （2） The quantity of soil microorganisms under flooding conditions was much lower than that in the normal water supply groups. Flooding significantly decreased the quantity of bacteria and fungi on the 60^th day, and the quantity of actinomycetes and fungi on the 120^th day compared with that of the normal water supply groups （P 〈 0.05）. （3） The Cd treatments had little effect on the quantity of soil microorganisms （P 〉 0.05）. The primary reason may be the relatively low concentrations of Cd in this study. （4） Planting S. variegata significantly improved the activity of phosphatase in the soils on the 60^th day and the activities of urease and invertase in the soils on the 120^th day （P 〈 0.05）. （5） The activity of phosphatase on the 60^th day, and the activity of urease, invertase, and phosphatase on the 120^th day were significantly reduced by flooding. （6） The activity of phosphatase on the 60^th day and the activity of urease on the 120^th day were significantly reduced by Cd stress. In summary, microorganisms and enzymatic activity in soils, which were sensitive to Cd stress and flooding, could be used to estimate the effect of phytoremediation on Cd-contaminated soils in the riparian area of Three Gorges Reservoir. Planting S. variegata could improve the status of microorganisms and enzymatic activity in Cd-contaminated soils under flooding conditions. S. variegata has significant potential to improve Cd-contaminated soils in a flooded environment.