Khan Khalid Saifullah, Joergensen Rainer Georg
Department of Soil Biology and Plant Nutrition, University of Kassel, Nordbahnhofstr. 1a, 37213 Witzenhausen, Germany.
Chemosphere. 2006 Nov;65(6):981-7. doi: 10.1016/j.chemosphere.2006.03.038. Epub 2006 May 4.
Two incubation experiments were conducted to evaluate differences in the microbial use of non-contaminated and heavy metal contaminated nettle (Urtica dioica L.) shoot residues in three soils subjected to heavy metal pollution (Zn, Pb, Cu, and Cd) by river sediments. The microbial use of shoot residues was monitored by changes in microbial biomass C, biomass N, biomass P, ergosterol, N mineralisation, CO(2) production and O(2) consumption rates. Microbial biomass C, N, and P were estimated by fumigation extraction. In the non-amended soils, the mean microbial biomass C to soil organic C ratio decreased from 2.3% in the low metal soil to 1.1% in the high metal soils. In the 42-d incubation experiment, the addition of 2% nettle residues resulted in markedly increased contents of microbial biomass P (+240%), biomass C (+270%), biomass N (+310%), and ergosterol (+360%). The relative increase in the four microbial properties was similar for the three soils and did not show any clear heavy metal effect. The contents of microbial biomass C, N and P and ergosterol contents declined approximately by 30% during the incubation as in the non-amended soils. The ratios microbial biomass C to N, microbial biomass C to P, and ergosterol to microbial biomass C remained constant at 5.2, 26, and 0.5%, respectively. In the 6-d incubation experiment, the respiratory quotient CO(2)/O(2) increased from 0.74 in the low metal soil to 1.58 in the high metal soil in the non-amended soils. In the treatments amended with 4% nettle residues, the respiratory quotient was constant at 1.13, without any effects of the three soils or the two nettle treatments. Contaminated nettle residues led generally to significantly lower N mineralisation, CO(2) production and O(2) consumption rates than non-contaminated nettle residues. However, the absolute differences were small.
进行了两项培养实验，以评估在受河流沉积物重金属污染（锌、铅、铜和镉）的三种土壤中，微生物对未受污染和重金属污染的荨麻（Urtica dioica L.）茎残体的利用差异。通过微生物生物量碳、生物量氮、生物量磷、麦角固醇、氮矿化、二氧化碳产生和氧气消耗率的变化来监测茎残体的微生物利用情况。微生物生物量碳、氮和磷通过熏蒸提取法进行估算。在未改良的土壤中，微生物生物量碳与土壤有机碳的平均比率从低金属土壤中的2.3%降至高金属土壤中的1.1%。在42天的培养实验中，添加2%的荨麻残体导致微生物生物量磷（增加240%）、生物量碳（增加270%）、生物量氮（增加310%）和麦角固醇（增加360%）的含量显著增加。三种土壤中这四种微生物特性的相对增加相似，且未显示出明显的重金属效应。与未改良的土壤一样，在培养过程中，微生物生物量碳、氮和磷的含量以及麦角固醇含量大约下降了30%。微生物生物量碳与氮的比率、微生物生物量碳与磷的比率以及麦角固醇与微生物生物量碳的比率分别保持在5.2、26和0.5%不变。在6天的培养实验中，未改良土壤中呼吸商CO₂/O₂从低金属土壤中的0.74增加到高金属土壤中的1.58。在用4%荨麻残体改良的处理中，呼吸商恒定在1.13，不受三种土壤或两种荨麻处理的影响。受污染的荨麻残体通常导致氮矿化、二氧化碳产生和氧气消耗率显著低于未受污染的荨麻残体。然而，绝对差异很小。
