Department of Soil Science and Engineering, Faculty of Agriculture, Shahrekord University, P.O. Box 115, Shahrekord, Iran.
Ecotoxicology. 2021 Aug;30(6):1071-1083. doi: 10.1007/s10646-021-02433-2. Epub 2021 Jun 8.
Salinity may increase metal mobilization with a potentially significant consequence for soil enzymatic activity and nutrient cycling. The goal of this study was to investigate changes in soil enzyme activity in response to salinization of a clay loam soil artificially polluted with cadmium (Cd) and lead (Pb) during a 120-day incubation experiment. Soil samples were polluted with Cd (10 mg Cd kg), Pb (150 mg Pb kg), and a combination of Cd and Pb, then preincubated for aging and eventually salinized with three levels of NaCl solution (control, low and high). NaCl salinity consistently increased the mobilization of Cd (12-22%) and Pb (5-16%) with greater increases at high (17-22% for Cd, 9-16% for Pb) than low (12% for Cd, 5-7% for Pb) salinity levels. While the increased Cd mobilization was greater in co-polluted (22%) than Cd-polluted (17%) soils, the increase of Pb mobilization was lower in co-polluted (9%) than Pb-polluted (16%) soils at high salinity level. The salinity-induced increases in metal mobilization significantly depressed soil microbial respiration (up to 43%), microbial biomass content (up to 63%), and enzymatic activities (up to 87%). The multivariate analysis further supported that the increased soil electrical conductivity, Cd mobilization, and pH after salinization were the most important factors governing microbial activity and biomass in metal-polluted soils. Results showed that changes in microbial biomass and mobile metal pool with increasing salinity had a major effect on enzyme activities, particularly under the combined metals. This study indicated that the secondary salinization of metal-polluted soils would impose an additional stress on enzymatic activities as biochemical indicators of soil quality, and therefore should be avoided for the maintenance of soil microbial and biochemical functions, especially in arid regions. In metal-polluted soils, the observed responses of extracellular and intracellular enzymes to salinity can be used to advance our knowledge of microbial processes when modeling the carbon and nutrient cycling.
盐度可能会增加金属的移动性，这对土壤酶活性和养分循环可能会产生重大影响。本研究的目的是在 120 天的孵育实验中，研究粘壤土中土壤酶活性对盐分胁迫的响应变化，该土壤样本是人工添加了镉（Cd）和铅（Pb）污染的。土壤样本先被 Cd（10mgCdkg）、Pb（150mgPbkg）和 Cd 和 Pb 的混合物污染，然后进行预孵育以老化，最后用三种浓度的 NaCl 溶液（对照、低盐和高盐）进行盐化。NaCl 盐度持续增加 Cd（12-22%）和 Pb（5-16%）的移动性，在高盐度（Cd 增加 17-22%，Pb 增加 9-16%）时比低盐度（Cd 增加 12%，Pb 增加 5-7%）时增加更大。虽然 Cd 污染土壤（22%）的 Cd 移动性增加大于 Cd 和 Pb 复合污染土壤（17%），但在高盐度水平下，Pb 移动性的增加低于 Pb 污染土壤（9%）和 Cd 和 Pb 复合污染土壤（16%）。盐分诱导的金属移动性增加显著抑制了土壤微生物呼吸（高达 43%）、微生物生物量含量（高达 63%）和酶活性（高达 87%）。多元分析进一步表明，盐化后土壤电导率、Cd 移动性和 pH 的增加是控制金属污染土壤微生物活性和生物量的最重要因素。结果表明，随着盐度的增加，微生物生物量和可移动金属库的变化对酶活性有重大影响，特别是在复合金属条件下。本研究表明，金属污染土壤的次生盐化会对酶活性产生额外的压力，酶活性作为土壤质量的生化指标，因此应避免次生盐化，以维持土壤微生物和生化功能，特别是在干旱地区。在金属污染土壤中，观察到的胞外和胞内酶对盐度的响应可以为我们在模拟碳和养分循环时，对微生物过程的认识提供帮助。
