Johnsen Anders R, de Lipthay Julia R, Sørensen Søren J, Ekelund Flemming, Christensen Peter, Andersen Ole, Karlson Ulrich, Jacobsen Carsten S
Geological Survey of Denmark and Greenland, Department of Geochemistry, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Environ Microbiol. 2006 Mar;8(3):535-45. doi: 10.1111/j.1462-2920.2005.00935.x.
Diffuse pollution with polycyclic aromatic hydrocarbons (PAHs) of topsoil in urban regions has caused increasing concerns in recent years. We simulated diffuse pollution of soil in microcosms by spiking sandy topsoil (A-horizon) and coarse, mineral subsoil (C-horizon) with street dust (PM63) isolated from municipal street sweepings from central Copenhagen. The microbial communities adapted to PAH degradation in microcosms spiked with street dust in both A-horizon and C-horizon soils, in spite of low PAH-concentrations. The increased potential for PAH degradation was demonstrated on several levels: by slowly diminishing PAH-concentrations, increased mineralization of 14C-PAHs, increasing numbers of PAH degraders and increased prevalence of nah and pdo1 PAH degradation genes, i.e. the microbial communities quickly adapted to PAH degradation. Three- and 4-ring PAHs from the street dust were biodegraded to some extent (10-20%), but 5- and 6-ring PAHs were not biodegraded in spite of frequent soil mixing and high PAH degradation potentials. In addition to biodegradation, leaching of 2-, 3- and 4-ring PAHs from the A-horizon to the C-horizon seems to reduce PAH-levels in surface soil. Over time, levels of 2-, 3- and 4-ring PAHs in surface soil may reach equilibrium between input and the combination of biodegradation and leaching. However, levels of the environmentally critical 5- and 6-ring PAHs will probably continue to rise. We presume that sorption to black carbon particles is responsible for the persistence and low bioaccessibility of 5- and 6-ring PAHs in diffusely polluted soil.
近年来，城市地区表土中多环芳烃（PAHs）的扩散污染引发了越来越多的关注。我们通过向从哥本哈根市中心街道清扫物中分离出的街道灰尘（PM63）中添加沙质表土（A层）和粗粒矿物底土（C层），在微观世界中模拟土壤的扩散污染。尽管PAH浓度较低，但在A层和C层土壤中添加街道灰尘的微观世界中，微生物群落适应了PAH降解。PAH降解潜力的增加在几个层面上得到了证明：PAH浓度缓慢降低、14C-PAHs矿化增加、PAH降解菌数量增加以及nah和pdo1 PAH降解基因的流行率增加，即微生物群落迅速适应了PAH降解。街道灰尘中的三环和四环PAHs在一定程度上（10-20%）被生物降解，但五环和六环PAHs尽管频繁进行土壤混合且具有较高的PAH降解潜力，却未被生物降解。除了生物降解外，从A层到C层的二环、三环和四环PAHs的淋溶似乎降低了表层土壤中的PAH水平。随着时间的推移，表层土壤中二环、三环和四环PAHs的水平可能会在输入与生物降解和淋溶的组合之间达到平衡。然而，对环境至关重要的五环和六环PAHs的水平可能会继续上升。我们推测，对黑碳颗粒的吸附是扩散污染土壤中五环和六环PAHs持久性和低生物可及性的原因。
