土壤-青菜系统中铅污染对土壤微生物活性及多样性的影响

采用盆栽方法研究了青菜种植条件下2种不同类型的人为铅污染土(黄松田土和黄红壤)中不同处理对土壤微生物生物量、生理生态参数以及群落结构的影响.结果表明,2种土壤在外源铅含量为100和300 mg·kg-1时,土壤微生物生物量有微小增加,而高浓度铅污染使土壤微生物生物量显著降低.在高浓度铅污染土壤中,微生物生理生态参数发生明显变化,微生物生物量碳/土壤有机质碳(Cmic/Corg)逐渐下降,代谢熵(qco2)明显上升,表明土壤微生物群落处于胁迫状态.结果还显示,铅污染对土壤微生物的影响与不同的管理方式(青菜种植情况)以及土壤中有机质、粘粒含量等有关,在种植青菜、有机质和粘粒含量高的土壤中,土壤微生物各项参数变化要小.对21种磷脂脂肪酸(PLFA)的图谱进行分析,结果表明,受铅污染土壤的微生物群落结构组成伴随着功能参数的变化而发生了改变;随着铅污染程度的增强,指示真菌和放线菌类的脂肪酸增加,而革兰氏阳性菌与革兰氏阴性菌脂肪酸比值下降.

The influence of lead contamination on soil-microbial activity and community structure diversity in a soil-greengrocery system

In order to examine the influence of lead (Pb) contamination on microbial biomass, two ecophysiological parameters and microbial community structure in soil during the growth of Chinese Cabbage (Brassica chinensis), a 60 days-growth experiment of the plant was conducted in two different soils, namely, marine sediment silty loam (S1) and yellowish red soil (S2). Six application rates of lead acetate were added to obtain the Pb concentrations of 0, 100, 300, 500, 700 and 900 mg·kg-1 soil. The results revealed that the Pb application at the level of 100 and 300 mg·kg-1 soil displayed a slight stimulative effect on microbial biomass, whereas Pb concentrations >500 mg·kg-1 caused an immediate gradual significant decline in microbial biomass for both two soils. Two ecophysiological parameters, the microbial biomass carbon/ organic carbon (Cmic/Corg) ratio was decreased and a consequence the metabolic quotient (qCO2) was increased with elevating Pb concentrations, indicating a stressful condition for soil microflora. The results also showed that less shifts in soil microbial biomass and two ecophysiological parameters were occurred in planted soils as compared with the respective unplanted soils, suggesting that the influences on microorganisms by Pb contamination was related to different management (plant vegetation) and the clay and organic matter contents of the soils. The profiles of 21 phospholipid fatty acids (PLFAs) were used to assess whether observed changes in functional microbial parameters were accompanied by changes in the composition of the microbial communities at Pb application rates of 0, 300 and 900 mg·kg-1 soil. The results of principal component analyses (PCA) indicated there were significant differences in the soil microbial community structure among three Pb treatments. Relative increases in fatty acid indicators for fungi and actinomycetes and gradual increases in the ratio of Gram-positive to Gram-negative bacteria were found with elevating Pb concentrations.