Studies on methods for evaluation of influence of pollutants on soil ecosystems

土壤受酸、重金属等污染物的污染日益严重，但这些污染物对土壤生态系统的影响尚不清楚。本研究的目的是明确污染物对土壤生态系统的影响，建立污染物对土壤生态系统影响的评价方法。以酸为污染物，采用人工加酸和天然酸性土壤，研究了酸对土壤生态系统的影响。主要结果如下。(1)向土壤中加入不同量的硫酸后，对土壤中的微生物种群进行了计数。随着土壤pH值的降低，土壤细菌总数和革兰氏阴性菌数量呈下降趋势，真菌数量呈上升趋势。pH值低于3.5时，土壤中碳、氮的矿化受到影响，pH值低于4时，土壤中的硝化作用不发生。(2)研究了硫酸（pH 3）和蒸馏水（对照）灌溉土壤中的微生物种群。酸灌土壤中放线菌和革兰氏阴性细菌数量均低于对照土壤。两种土壤的真菌数量、酶活性和呼吸活性基本相同，但硝化活性受到酸灌溉的影响。(3)对天然酸性土壤的微生物区系和微生物活性进行了研究。放线菌数量与土壤pH的相关系数最大，土壤酶活性和呼吸活性与土壤pH无关，但硝化活性在pH 4以下较小。

Soil pollution by pollutants such as acids, heavy metals is increasing, but the influence of these pollutants on soil ecosystems is not clear. The purpose of this study is to make clear the influence on soil ecosystems and to establish the methods for evaluation of pollutants on soil ecosystems. Acids were used as pollutant, and the influence of acids on soil ecosystems was investigated using the soils added with acid artificially and natural acid soils. The main results are as follows.(1) After various amounts of sulfuric acid were added to soils, the population of microorganisms in the soils was enumerated. The numbers of total bacteria and gram-negative bacteria tended to decrease and that of fungi tended to increase as the soil pH become lower. The mineralization of carbon and nitrogen was influenced below pH3.5, while the nitrification did not occurred below pH4.(2) The population of microorganisms in soils irrigated with sulfuric acid (pH 3) and with distilled water (control) was investigated. The numbers of actinomycetes and gram-negative bacteria in the soil irrigated with acid were less than those in control soil. The number of fungi, enzyme activities and respiration activity were almost same in both soils, while nitrification activity decreased by the irrigation of acid.(3) Microflora and microbial activities in natural acid soils were investigated. The number of actinomycetes has the highest correlation coefficient with soil pH.Enzyme activities and respiration activity did not related to soil pH, but the nitrification activity was less below pH 4.These results suggest that the number of actinomycetes or gram-negative bacteria is the best indicator of the soil pollution.