Civil Engineering, University of British Columbia, 6250 Applied Science Lane, Vancouver, BC, V6T 1Z4, Canada.
Civil Engineering, University of British Columbia, 6250 Applied Science Lane, Vancouver, BC, V6T 1Z4, Canada.
Environ Pollut. 2018 Apr;235:74-84. doi: 10.1016/j.envpol.2017.12.030. Epub 2017 Dec 21.
A critical review of existing publications is presented i) to summarize the occurrence of various classes of per- and polyfluoroalkyl substances (PFASs) and their sources in landfills, ii) to identify temporal and geographical trends of PFASs in landfills; iii) to delineate the factors affecting PFASs in landfills; and iv) to identify research gaps and future research directions. Studies have shown that perfluoroalkyl acids (PFAAs) are routinely detected in landfill leachate, with short chain (C4-C7) PFAAs being most abundant, possibly indicating their greater mobility, and reflecting the industrial shift towards shorter-chain compounds. Despite its restricted use, perfluorooctanoic acid (PFOA) remains one of the most abundant PFAAs in landfill leachates. Recent studies have also documented the presence of PFAA-precursors (e.g., saturated and unsaturated fluorotelomer carboxylic acids) in landfill leachates at concentrations comparable to, or higher than, the most frequently detected PFAAs. Landfill ambient air also contains elevated concentrations of PFASs, primarily semi-volatile precursors (e.g., fluorotelomer alcohols) compared to upwind control sites, suggesting that landfills are potential sources of atmospheric PFASs. The fate of PFASs inside landfills is controlled by a combination of biological and abiotic processes, with biodegradation releasing most of the PFASs from landfilled waste to leachate. Biodegradation in simulated anaerobic reactors has been found to be closely related to the methanogenic phase. The methane-yielding stage also results in higher pH (>7) of leachates, correlated with higher mobility of PFAAs. Little information exists regarding PFAA-precursors in landfills. To avoid significant underestimation of the total PFAS released from landfills, PFAA-precursors and their degradation products should be determined in future studies. Owing to the semi-volatile nature of some precursor compounds and their degradation products, future studies also need to include landfill gas to clarify degradation pathways and the overall fate of PFASs.
对现有文献进行了批判性回顾，旨在：i）总结各种类别的全氟和多氟烷基物质 (PFAS) 及其在垃圾填埋场中的来源；ii）确定垃圾填埋场中 PFAS 的时间和地理趋势；iii）确定影响垃圾填埋场中 PFAS 的因素；iv）确定研究差距和未来的研究方向。研究表明，全氟烷基酸 (PFAAs) 通常在垃圾填埋场渗滤液中被检测到，其中短链 (C4-C7) PFAAs 最为丰富，这可能表明它们的迁移性更强，反映了工业向短链化合物的转变。尽管其使用受到限制，但全氟辛酸 (PFOA) 仍然是垃圾填埋场渗滤液中最丰富的 PFAAs 之一。最近的研究还记录了在垃圾填埋场渗滤液中存在 PFAA 前体（例如，饱和和不饱和氟调聚物羧酸），其浓度与最常检测到的 PFAAs 相当或更高。垃圾填埋场环境空气中也含有浓度较高的 PFAS，主要是半挥发性前体（例如，氟调聚物醇），与上风控制点相比，这表明垃圾填埋场是大气 PFAS 的潜在来源。PFAS 在垃圾填埋场内的命运受生物和非生物过程的共同控制，生物降解将填埋废物中大部分 PFAS 释放到渗滤液中。在模拟厌氧反应器中的生物降解已被发现与产甲烷阶段密切相关。产甲烷阶段还导致渗滤液的 pH 值升高（>7），与 PFAAs 的迁移性增加相关。关于垃圾填埋场中 PFAA 前体的信息很少。为了避免对从垃圾填埋场释放的总 PFAS 产生重大低估，未来的研究应确定 PFAA 前体及其降解产物。由于一些前体化合物及其降解产物具有半挥发性，未来的研究还需要包括垃圾填埋气，以阐明降解途径和 PFAS 的整体命运。
