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: 6443920
• 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: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至 2002-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6443920
• 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）是美国许多地方土壤和地下水中的主要污染物。许多PAH是已知或疑似致癌物，但许多PAH也被认为是可被原生和污染土壤中的细菌和真菌生物降解的。生物过程已被用于补救多环芳烃污染的场地，但高分子量，致癌物质的去除往往是不完整的。由于这些化合物难溶于水，它们在污染系统中对某些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方法，通过这些方法可以识别并最终克服似乎抵抗生物降解的限制PAH降解的因素。这些因素可以包括缺乏大量能够降解这些化合物的微生物;所有生物体对化合物的固有降解速率非常低，这可能因其他PAH的存在而加剧;微生物的生长底物随时间的损失和随之而来的PAH降解活性的损失;微生物的生长底物随时间的损失和随之而来的PAH降解活性的损失;以及可能抑制一种或多种PAH降解的不完全代谢产物的积累。致癌多环芳烃的可持续清除可能决定了在特定地点，主动生物修复是否是一种可接受的技术。 此外，根据新出现的基于风险的现场管理方法，预计许多现场的PAH污染将留在原地。要了解自然衰减的限制和潜在的长期风险，在这样的网站，这是至关重要的，以提高我们的多环芳烃降解率和影响这些率的因素的知识。拟议的研究将量化从各种污染土壤中分离出的细菌对高分子量多环芳烃的降解速率，以及混合物中其他多环芳烃对这些速率的影响。然后，将在实验室规模的生物反应器中处理来自工业场地的实际污染土壤，以研究一种或多种明显不可降解的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）定量处理过的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）定量处理过的土壤中能够降解难降解PAH的生物体;（ii）评价添加已知刺激PAH降解的易降解的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由于代谢物积累而抑制PAH降解细菌;和（iv）检查生物利用度在这些化合物的表观降解中的作用。随着对目标化合物有限降解的最主要原因的了解，我们将探索直接在生物反应器中在从生物反应器中去除的经处理的土壤中刺激生物降解的方法。