Cd胁迫下稻田土壤生物活性与酶活性综合研究

Effects of Cd^(2+) on the Biological Activities and the Enzyme Activities in Submerged Paddy Soil

试验室盆栽条件下,研究了不同程度的外源重金属Cd胁迫对淹水稻田土壤生物活性和土壤酶活性的影响。结果表明,重金属Cd胁迫对不同的土壤生化过程具有不同效应,低浓度Cd的添加对水稻田土壤呼吸强度有一定刺激作用,高浓度则产生抑制;对与厌氧微生物相关的生物活性的影响中,以产甲烷活性所受影响最大,硫酸盐还原活性次之,反硝化活性最小,而且在整个处理期间对Cd的反应较为稳定,是表征稻田土壤重金属污染程度的良好生物指标。Cd胁迫对土壤酶活性的影响中,对土壤的脲酶活性有很显著的抑制作用,最大抑制率达到57.4%,而对过氧化氢酶、转化酶、磷酸酶等活性影响较小,最大抑制率均未达到25%,转化酶对Cd具有很强的拮抗作用。

As the important biological parameter, the biochemical activities are important indexes of heavy metal environmental safety assessment. The influence of Cd2+ on the dynamics of the biological activities and the enzyme activities in submerged red paddy soil in Jiangxi province was studied using traditional incubation method under laboratory conditions. The soil respiration was promoted by Cd2+ at lower concentrations, but was inhibited at higher concentrations. The effects of different concentrations of Cd2+ on other soil biochemical process in soils were also different significantly: the lower concentration of cadmium was helpful to increase most of the biochemical processes, but the higher concentrations of Cd2+ greatly inhibited microbial activities; the higher the concentration of cadmium applied, the more significant the inhibition to the observed activities. Compared with other aerobic biochemical activities, the methane emission activity was most sensitive to Cd2+ , followed by the sulfate reduction activity. The inhibition of Cd2+ for the denitrification activity was slightly less and very stable during the whole treated stage, and could be as an indicator of the Cd2+ pollution degree in paddy soil. The sensitive order to cadmium of four soil enzyme activities was: urease>catalase>phosphatases>invertase. Cadium inhibited urease activities most with the maximum inhibition rate of 57.4% and had less influence on other soil enzyme activities with the maximum inhibition rates less than 25% . There were significant negative correlations between the cadmium concentration and microbial respiration, the sulfate reduction activity, the methane production activity, urease activity, and catalase activity, which suggested that these indexes might indicate the contamination degree of paddy soil by Cd2+ . According to these microbial indexes, about 1～ 5mg· kg- 1 was considered the critical level of cadmium in submerged paddy soil.