Bioavailability and Biodegradation of Polycyclic Aromatic Hydrocarbons

多环芳烃的生物利用度和生物降解

• 批准号: 7067252
• 负责人: MICHAEL AITKEN
• 金额: $ 32.65万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7067252
• 关键词: bioreactors; biotransformation; carbopolycyclic compound; environmental toxicology; microorganism metabolism; molecular probes; soil microbiology; soil pollution; soil sampling; stable isotope; toxin metabolism

Polycyclic aromatic hydrocarbons (PAHs) are among the top 10 contaminants of concern at Superfund sites and are the major contaminants at an estimated 45,000 sites outside the jurisdiction of the Superfund program. The U.S. EPA regulates 16 PAHs, 7 of which are considered to be human carcinogens. PAHs are inherently biodegradable, but a significant fraction of each of the EPA-regulated PAHs is usually not removed during bioremediation of PAH-contaminated systems. Of particular concern is that the 4-, 5- and 6- ring compounds, which include all of the carcinogenic PAHs, are removed less extensively than the lower-molecular-weight compounds. Limitations in PAH biodegradation in field-contaminated soils are typically attributed to limitations in the availability of the PAHs to microorganisms, but this is rarely documented on a site-specific basis and has proven to be untrue of the 5- and 6-ring PAHs in a number of cases. Our ability to elucidate the factors that influence PAH degradation in any field-contaminated system is constrained by the overwhelming complexity of the system and by our relatively limited knowledge of microbial PAH metabolism and the diversity of PAH-degrading microorganisms. In some cases, interventions intended to improve PAH biodegradation can lead to the formation of toxic byproducts of PAH transformation by microorganisms. We propose to investigate the relationships among PAH bioavailability, biodegradation, the formation of toxic biotransformation products, and net risk reduction using two experimental platforms with field-contaminated soil. Soil column systems will be used to evaluate in situ approaches to bioremediation, and slurry-phase bioreactors will be used to study above-ground approaches to bioremediation. We hypothesize that different microbial communities will be selected in these systems, leading to differences in the ability to remove the most bioavailable fractions of the PAHs and in the propensity to form toxic byproducts. We also hypothesize that methods proposed to enhance PAH bioavailability for improved biodegradation are likely to form genotoxic products. Knowledge of the microbial ecology of PAH biodegradation will be expanded by using an emerging cultivation-independent molecular tool (stable-isotope probing) to identify microorganisms responsible for degrading a range of PAHs in relevant, complex systems. This knowledge is important in eventually being able to assess the potential for an indigenous microbial community to degrade specific PAHs in contaminated environments. Because dermal exposure is a major route of exposure to PAHs in contaminated soil, we will also collaborate with Project 4 to investigate the effects of contaminated soil on dermal exposure endpoints. Preliminary experiments will quantify the bioavailable fractions of PAHs relevant to potential uptake by human skin, and the effects of biological treatment of the soil on dermal exposure will be evaluated.

多环芳烃（PAHs）是超级基金场地最受关注的10大污染物之一，也是超级基金项目管辖范围外约45,000个场地的主要污染物。美国环保局规定了16种多环芳烃，其中7种被认为是人类致癌物。多环芳烃本质上是可生物降解的，但在多环芳烃污染系统的生物修复过程中，每一种由epa调节的多环芳烃的很大一部分通常不会被去除。特别值得关注的是，包括所有致癌多环芳烃的4环、5环和6环化合物被去除的程度不及低分子量化合物。多环芳烃在田间污染土壤中生物降解的限制通常归因于微生物对多环芳烃的可得性的限制，但很少有具体地点的记录，并且在许多情况下已证明5环和6环多环芳烃是不真实的。我们阐明在任何田间污染系统中影响多环芳烃降解的因素的能力受到系统的巨大复杂性以及我们对微生物多环芳烃代谢和多环芳烃降解微生物多样性的相对有限的知识的限制。在某些情况下，干预措施旨在改善多环芳烃