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

酸、重金属等污染物对土壤的污染日益严重，但这些污染物对土壤生态系统的影响尚不清楚。本研究旨在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，采用人工加酸土壤和天然加酸土壤，研究了酸对土壤生态系统的影响。主要结果如下：(1)在土壤中加入不同量的硫酸后，列举了土壤中微生物的数量。随着土壤pH值的降低，细菌总数和革兰氏阴性菌数量呈减少趋势，真菌数量呈增加趋势。ph低于3.5时，碳和氮的矿化受到影响，而ph低于4时，硝化作用不发生。(2)研究了硫酸（pH 3）和蒸馏水（对照）灌溉土壤中微生物的数量。灌酸土壤放线菌和革兰氏阴性菌数量明显少于对照土壤。两种土壤的真菌数量、酶活性和呼吸活性基本相同，而硝化活性因灌酸而降低。(3)研究了天然酸性土壤的微生物区系和微生物活性。放线菌数量与土壤pH的相关系数最高，酶活性和呼吸活性与土壤pH无关，但在pH 4以下，硝化活性较低。这些结果表明，放线菌或革兰氏阴性菌的数量是土壤污染的最佳指标。

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.