Biodegradation of high molecular weight PAHs in contaminated soil

污染土壤中高分子量多环芳烃的生物降解

• 批准号: 6587625
• 负责人: MICHAEL AITKEN
• 金额: $ 17.52万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2003-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6587625
• 关键词: bacteria; bioreactors; biotransformation; carbopolycyclic compound; chemical carcinogen; environmental contamination; environmental toxicology; ground water; hazardous substances; industrial waste; microorganism metabolism; molecular weight; soil microbiology; soil pollution; soil sampling; toxin metabolism; waste treatment

Polycyclic aromatic hydrocarbons (PAH) are major contaminants in soil and groundwater at a number of sites across the U.S. Many of the PAH are known or suspected carcinogens, yet many are also known to be biodegradable by bacteria and fungi indigenous to native and contaminated soils. Biological processes have been used to remediate PAH-contaminated sites, but removal of the high-molecular weight, carcinogenic species is often incomplete. Since these compounds are poorly soluble in water, their biodegradation of some of the PAH in contaminated systems is limited by factors other than bioavailability. The purpose of this project is to develop approaches by which the factor(s) that limit the degradation of PAH which appear to resist biodegradation can be identified and, eventually, overcome. Such factors can include the absence of significant numbers of microbes able to degrade these compounds; inherently very low rates of degradation of the compound by all organisms, which may be exacerbated by the presence of other PAH; loss of growth substrates for the microorganisms over time and consequent loss of PAH-degrading activity; loss of growth substrates for the microorganisms over time and consequent loss of PAH-degrading activity; and accumulation of products of incomplete metabolism that may inhibit the degradation of one or more PAH. Achievable removals of the carcinogenic PAH may determine whether active bioremediation is an acceptable technology at a given site. In addition, under emerging risk-based approaches to site management such of the PAH contamination is expected to be left in place at many sites. To understand the limits of natural attenuation and potential long-term risks at such sites, it is essential to improve our knowledge of the rates of PAH degradation and the factors that influence these rates. The proposed research will quantify rates of degradation of high-molecular weight PAH by bacteria isolated from a variety of contaminated soils and the effect of other PAH in mixtures on these rates. Then, actual contaminated soils from an industrial site will be treated will be treated in a bench-scale bioreactor to study the degradation of one or more apparently recalcitrant PAH. The factor(s) that govern the degradation of these compounds will be elucidated by: (i) quantifying the organisms in the treated soil that are capable of degrading of these compounds will be elucidated by: (i) quantifying the organisms in the treated soil that are capable of degrading the recalcitrant PAH; (ii) evaluating the effects of adding readily- degraded, naturally occurring compounds known to stimulate PAH degradation; (iii) examining whether the liquid phase in the bioreactor is inhibitory to PAH-degrading bacteria as a result of metabolite accumulation; and (iv) examining the role of bioavailability in the apparent recalcitrance of these compounds. With knowledge of the factor(s) most responsible for limited degradation of the target compound(s), we will then explore methods of stimulating biodegradation either directly in the bioreactor in treated soil removed from the bioreactor.

多环芳烃 (PAH) 是美国多个地点土壤和地下水中的主要污染物。许多多环芳烃是已知或可疑的致癌物，但也有许多多环芳烃可被原生和受污染土壤中的细菌和真菌生物降解。生物过程已被用来修复多环芳烃污染场地，但高分子量致癌物质的去除往往不完全。由于这些化合物难溶于水，它们对受污染系统中某些 PAH 的生物降解受到生物利用度以外的因素的限制。该项目的目的是开发一些方法，通过这些方法可以识别并最终克服限制 PAH 降解的因素，这些因素似乎会阻碍生物降解。这些因素可能包括缺乏大量能够降解这些化合物的微生物；所有生物体对该化合物的降解率本来就非常低，其他多环芳烃的存在可能会加剧这种降解率；随着时间的推移，微生物生长底物的损失以及随之而来的 PAH 降解活性的损失；随着时间的推移，微生物生长底物的损失以及随之而来的 PAH 降解活性的损失；不完全代谢产物的积累可能会抑制一种或多种多环芳烃的降解。致癌多环芳烃的可实现去除可能决定主动生物修复是否是给定地点可接受的技术。 此外，根据新兴的基于风险的场地管理方法，多环芳烃污染预计将留在许多场地。为了了解这些地点自然衰减的限制和潜在的长期风险，必须提高我们对 PAH 降解率以及影响这些速率的因素的了解。拟议的研究将量化从各种污染土壤中分离出的细菌降解高分子量多环芳烃的速率，以及混合物中其他多环芳烃对这些速率的影响。然后，来自工业场地的实际污染土壤将在小型生物反应器中进行处理，以研究一种或多种明显顽固的 PAH 的降解。控制这些化合物降解的因素将通过以下方式阐明： (i) 量化处理土壤中能够降解这些化合物的生物体 将通过以下方式阐明： (i) 量化处理土壤中的生物体能够降解顽固的多环芳烃； (ii) 评估添加已知可刺激 PAH 降解的易降解、天然存在的化合物的效果； (iii)检查生物反应器中的液相是否因代谢物积累而对PAH降解菌产生抑制； (iv) 检查生物利用度在这些化合物的明显顽抗性中的作用。了解了对目标化合物有限降解最有影响的因素后，我们将探索直接在生物反应器中或从生物反应器中取出的处理过的土壤中刺激生物降解的方法。