Biodegradation of Pyrene in Soil Microcosms: Identification of a Toxic Intermediate

Pyrene is a polycyclic aromatic hydrocarbon (PAH) compound that was a regulated pollutant that limited the rate of bioremediation of wood preservative contaminated soil at the Champion International Superfund Site in Libby, Montana. The half-life of pyrene in soil at field scale may extend beyond one year depending on environmental conditions. The environmental fate of pyrene and other PAHs affected by naturally occurring soil microbes is important in the development of monitoring and bioremediation strategies, and in protecting drinking water supplies originating from groundwater resources threatened by leaching of PAHs. Mycobacterium sp. KMS was isolated from vadose zone soil at the Libby site and was shown to transform more than 60% of 14 C pyrene added to soil microcosms to carbon dioxide within 38 days at 28 0 C. In this study, Pyrene fate was monitored in four soil matrices: an uncontaminated Kidman soil, a site boundary soil (BD), the BD soil with the addition of Mycobacterium sp. KMS, and mercuric chloride poisoned BD soil. The amount of extractable pyrene was relatively constant over the experimental period in Kidman and poisoned soil microcosms, whereas the amount of extractable pyrene decreased with time in BD soil and decreased rapidly in the inoculated BD soil. High-performance Liquid Chromatography (HPLC), Liquid Chromatography Mass Spectrometry (LC/MS) and Nuclear Magnetic Resonance (NMR) spectroscopy analyses showed the formation of a major metabolite, pyrene-4,5-dione (PYRQ) in the BD soil microcosms with and without Mycobacterium sp. KMS inoculation. PYRQ was also identified in solvent extracts of site soil. PYRQ demonstrated a response in the aqueous Microtox® toxicity assay. It can be further degraded in inoculated and uninoculated BD soil, but it accumulates in other systems. The production of PYRQ and its possible release into environment may present a potential risk.

芘是一种多环芳烃（PAH）化合物，是一种受管制的污染物，它限制了蒙大拿州利比的冠军国际超级基金场地中受木材防腐剂污染土壤的生物修复速度。在田间尺度下，芘在土壤中的半衰期可能会根据环境条件延长至一年以上。芘和其他多环芳烃受天然土壤微生物影响的环境归趋，对于监测和生物修复策略的制定以及保护受多环芳烃浸出威胁的地下水资源所产生的饮用水供应非常重要。从利比场地的包气带土壤中分离出了分枝杆菌属KMS，结果表明，在28℃下，38天内它能将添加到土壤微宇宙中的超过60%的¹⁴C - 芘转化为二氧化碳。在这项研究中，对四种土壤基质中的芘的归趋进行了监测：未受污染的基德曼土壤、场地边界土壤（BD）、添加了分枝杆菌属KMS的BD土壤以及氯化汞毒害的BD土壤。在基德曼土壤和受毒害的土壤微宇宙中，可提取芘的量在实验期间相对恒定，而在BD土壤中可提取芘的量随时间减少，在接种了的BD土壤中减少得更快。高效液相色谱（HPLC）、液相色谱 - 质谱联用（LC/MS）和核磁共振（NMR）光谱分析表明，在接种和未接种分枝杆菌属KMS的BD土壤微宇宙中都形成了一种主要代谢产物——芘 - 4,5 - 二酮（PYRQ）。在场地土壤的溶剂提取物中也鉴定出了PYRQ。PYRQ在Microtox®水毒性测定中表现出反应。它可以在接种和未接种的BD土壤中进一步降解，但会在其他系统中积累。PYRQ的产生及其可能释放到环境中可能会带来潜在风险。