中文摘要：

采用温室盆栽试验，在种植紫花苜蓿的同时，分别施加木霉菌剂、根瘤菌菌剂以及木霉与根瘤菌复合菌剂，并采用离心分级法将处理后土壤分为4个粒径团聚体，即细黏粒（0．1～1μm）、粗黏粒（1～5gm）、粉粒（5～50μm）以及细砂粒（50～250μm），分析了植物域生物联合作用对不同粒径土壤中PAHs的去除效应。研究结果表明：紫花苜蓿一根瘤菌联合作用对PAHs污染土壤的修复效果最优，其降解率达60％以上。不同粒径组分中PAHs含量的分布表现为细砂粒〉粉粒〉粗黏粒〉细黏粒，且PAHs在不同粒径团聚体中去除率差异性较大。低环（2、3环）PAHs在各粒径组分中去除率较低（20％以下），并在不同粒径组分间呈非均衡分配状态；4环PAHs的去除主要集中在粉粒和细砂粒中，而5环PAHs的去除主要发生在细黏粒上。可见，PAHs在土壤不同粒径组分中分布特征及降解效应为进一步阐明PAHs污染土壤的生物修复机制提供了科学依据。

英文摘要：

A pot experiment was conducted to explore the combined remediation of microorganisms （Trichoderma reesei and Rhizobium meliloti） and alfalfa stimulated the degradation of PAHs by rhizosphere microflora in different particle-size fractions of soil aggregates. Soil aggregates were partitioned into 4 particle-size fractions （clay： 0.1 - 1 μm, fine silt： 1 - 5 μm, silt： 5 - 50 μm and fine sand： 50 - 250μm） by using the method of centrifugation in five treatments. The results showed that the degradation rate of PAHs in soil treated with Rhizobiurn meliloti with alfalfa was 60%. The distribution of 16 PAHs concentrations in different soil particle size composition was in the order of fine sand 〉 silt 〉 fine sand 〉 clay, besides, low-molecular （2, 3-ring） PAHs was not degraded and but transferred in different size of particles （degradation rate less than 20%）. The degradation of 4-ring PAHs occurred mainly on silt and fine sand soil particles and 5-ring PAHs degradation on the clay. Ilence, the distribution and degradation of PAils in different size of particles has a great significance on remediation ofPAHs polluted soil.