Passive Air Sampling Networks Combined with Multivariate Statistics Reveal Widespread Non-Aroclor Polychlorinated Biphenyl Sources to the Canadian Atmosphere

Polychlorinated biphenyls (PCBs) in the North American atmosphere were originally thought to arise through volatilization of commercial Aroclor mixtures, but there is growing evidence of atmospheric emissions of non-Aroclor, i.e., unintentionally produced, PCBs. Here, we report on measurements of all 209 PCB congeners in 169 passive air samples collected between 2019 and 2022 using networks established around the Salish Sea, British Columbia (BC), and along the St. Lawrence River and Estuary, Quebec (QC), in Canada. Hierarchical cluster analysis and positive matrix factorization were employed to identify, distinguish, and quantify different PCB sources to the atmosphere. PCBs were detected at every single site, with elevated levels found in the urban centers of the region (Vancouver, BC; Montreal, Quebec City, QC), including in the vicinity of a municipal waste incinerator. We found evidence that suggests legacy Aroclor emissions, e.g., associated with electrical equipment storage in Pointe-Claire, QC, and building emissions in Burnaby, BC. We also identified several locations (e.g., in Sept-Îles and Alma, QC) where non-Aroclor sources are estimated to contribute over 40% of PCBs. In particular, PCB congeners 47, 51, and 68, known byproducts of 2,4-dichlorobenzoyl peroxide (2,4-DCBP) decomposition during silicone rubber and polyester production, were strongly associated with PCB-7 and -25. Although Aroclors were estimated to remain the main contributors of PCBs to the Canadian atmosphere, unintentional production is making a non-negligible contribution (estimated to be at least 10%). Of the known non-Aroclor sources, 2,4-DCBP is likely still used in North America with little to no regulation.北美大气中的多氯联苯（polychlorinated biphenyls, PCBs）最初被认为源自商用Aroclor混合物的挥发作用，但越来越多的研究证据表明，大气中还存在非Aroclor型多氯联苯排放，即无意生成的多氯联苯。本研究针对2019至2022年间采集的169份被动空气样品中的全部209种多氯联苯同系物开展了检测，采样网络覆盖加拿大不列颠哥伦比亚省（BC）萨利希海周边区域，以及魁北克省（QC）圣劳伦斯河及其河口沿岸地带。本研究采用分层聚类分析（hierarchical cluster analysis）与正定矩阵因子分解法（positive matrix factorization），对大气中不同的多氯联苯污染源进行识别、区分与定量解析。所有采样点位均检出多氯联苯，在该区域的城市中心（不列颠哥伦比亚省温哥华；魁北克省蒙特利尔、魁北克市），包括某城市垃圾焚烧厂周边区域，均检测到升高的多氯联苯浓度。研究发现了与遗留Aroclor排放相关的证据，例如魁北克省庞特克莱尔地区与电气设备存储相关的排放，以及不列颠哥伦比亚省本拿比市的建筑排放。此外，研究在魁北克省塞普蒂-伊尔斯和阿尔马等多个点位发现，非Aroclor型污染源对大气中多氯联苯的贡献占比超过40%。具体而言，多氯联苯同系物47、51和68——作为2,4-二氯苯甲酰过氧化物（2,4-dichlorobenzoyl peroxide, 2,4-DCBP）在硅橡胶与聚酯生产过程中分解的已知副产物——与PCB-7和PCB-25呈现显著相关性。尽管估算结果显示，Aroclor仍是加拿大大气中多氯联苯的主要贡献源，但无意生成型多氯联苯的贡献已不可忽视（估算占比至少为10%）。在已知的非Aroclor污染源中，2,4-DCBP目前在北美可能仍在被使用，且几乎不受任何监管。