污泥与园林废弃物混合堆肥施用量对林地土壤重金属质量分数及微生物活性的影响

  目的  研究了城市污泥与园林废弃物混合堆肥在人工林地施用2 a后重金属质量分数和土壤微生物活性的变化，以期为城市污泥产品在林业上的资源化利用提供科学依据。  方法  在榆树Ulmus pumila林地设计随机区组试验，根据堆肥中污泥含量设置4种混合堆肥施加量水平(0、15、30、60 t·hm?2)，施用2 a后采集土样测定其中铬、铅、铜、锌、镉和镍等7种重金属指标(总量及形态)、土壤微生物碳氮质量分数、土壤呼吸强度及4种土壤酶活性等7种土壤微生物指标，分析不同施肥量对林地土壤质量的影响。  结果  污泥堆肥施用2 a后，6种重金属总量有一定的增加趋势，但各施加量之间差异不显著，同时不同形态的质量分数变化较小，表明土壤中重金属总体污染风险较低；土壤酶和微生物碳氮随施加量增加无明显变化趋势，但施肥样地的土壤酶指数和土壤呼吸强度都比对照样地高，表明施污泥堆肥提高了土壤微生物活性。  结论  污泥堆肥的施加量低于30 t·hm?2时，榆树林生态系统可承受其增加的重金属风险并提高土壤微生物活性，改善土壤质量。图1表4参22

Effect of sludge and garden waste composting rates on heavy metal content and microbial activity in plantation soil

  Objective  This study aims to explore the changes of heavy metal content and soil microbial activity in plantations after 2 years of mixed composting of municipal sludge and garden waste, in order to provide basis for utilization of municipal sludge products in forestry.  Method  A randomized block design was carried out in an experimental Ulmus pumila plantation. According to the sludge content in the compost, four levels of mixed compost (0, 15, 30 and 60 t·hm?2 of composted sludge) were set. After two years of application, soil samples were collected for analysis of six heavy metals(Cr, Pb, Cu, Zn, Cd, Ni), as well as seven soil microbial indicators, including microbial carbon and nitrogen, soil respiration and four enzyme activities. The effects of different fertilization rates on soil quality were analyzed.  Result  After 2 years of sludge composting, the total amount of six kinds of heavy metals increased, but there was no significant difference between different application amounts, indicating that the application of mixed compost had low risk of heavy mental pollution. Soil enzymes, microbial carbon and nitrogen had no obvious change with increment of compost amount, but the soil enzyme index and soil respiration intensity of the fertilized plot were greater than those of the control plot, suggesting that the mixed compost improved soil microbial activity.  Conclusion  When the amount of sludge compost is lower than 30 t·hm?2, the elm forest ecosystem could withstand the increased risk of heavy metals, increase soil microbial activity and improve soil quality. [Ch, 1 fig. 4 tab. 22 ref.]