Shanahan Caitlin E, Spak Scott N, Martinez Andres, Hornbuckle Keri C
School of Urban and Regional Planning, The University of Iowa , 345 Jessup Hall, Iowa City, Iowa 52242-1316, United States.
Department of Civil and Environmental Engineering & IIHR-Hydroscience and Engineering, The University of Iowa , Iowa City, Iowa 52242-1316, United States.
Environ Sci Technol. 2015 Dec 1;49(23):13878-88. doi: 10.1021/acs.est.5b00906. Epub 2015 Oct 29.
Urban areas are important regional sources of airborne polychlorinated biphenyls (PCBs) and population-scale airborne exposure, yet a comprehensive bottom-up source inventory of PCB emissions has never been quantified at urban scales in the United States. Here we report a comprehensive parcel level inventory of PCB stocks and emissions for Chicago, Illinois, developed with a transferable method from publicly available data. Chicago's legacy stocks hold 276 ± 147 tonnes ∑PCBs, with 0.2 tonnes added annually. Transformers and building sealants represent the largest legacy categories at 250 and 20 tonnes, respectively. From these stocks, annual emissions rates of 203 kg for ∑PCBs and 3 kg for PCB 11 explain observed concentrations in Chicago air. Sewage sludge drying contributes 25% to emissions, soils 31%, and transformers 21%. Known contaminated sites account for <1% of stocks and 17% of emissions to air. Paint is responsible for 0.00001% of stocks but up to 7% of ∑PCBs emissions. Stocks and emissions are highly concentrated and not correlated with population density or demographics at the neighborhood scale. Results suggest that strategies to further reduce exposure and ecosystem deposition must focus on the largest emissions sources rather than the most contaminated sites or the largest closed source legacy stocks.
城市地区是空气中多氯联苯（PCBs）的重要区域来源和人口规模的空气传播暴露源，但在美国城市尺度上，从未对多氯联苯排放进行过全面的自下而上的源清单量化。在此，我们报告了伊利诺伊州芝加哥市多氯联苯存量和排放的综合地块层面清单，该清单是通过一种可转移的方法从公开数据中编制而成的。芝加哥的遗留存量为276±147吨多氯联苯总量，每年增加0.2吨。变压器和建筑密封剂分别是最大的遗留类别，存量分别为250吨和20吨。从这些存量中，多氯联苯总量的年排放率为203千克，多氯联苯11的年排放率为3千克，这解释了在芝加哥空气中观测到的浓度。污泥干燥对排放的贡献率为25%，土壤为31%，变压器为21%。已知的污染场地占存量的比例不到1%，占向空气中排放的比例为17%。涂料占存量的0.00001%，但占多氯联苯总量排放的比例高达7%。存量和排放高度集中，在社区尺度上与人口密度或人口统计学特征无关。结果表明，进一步减少暴露和生态系统沉积的策略必须聚焦于最大的排放源，而非污染最严重的场地或最大的封闭源遗留存量。
