北京市某垃圾焚烧厂周边大气二噁英污染特征及暴露风险

Pollution Characteristics of PCDD/Fs in Ambient Air and Exposure Risk Assessment Around a Municipal Solid Waste Incinerator in Beijing

2014年4月至2015年1月对北京市某生活垃圾焚烧发电厂周边6 km范围内7个采样点采集环境空气,应用高分辨气相色谱-高分辨质谱(HRGC-HRMS)联用技术对二英(PCDD/Fs)浓度水平进行监测并对其组成特征及时空特征进行了分析.结果表明该生活垃圾焚烧发电厂周边环境空气中PCDD/Fs质量浓度的变化范围为8.9~140 pg·m^(-3),毒性当量(TEQ)变化范围为0.11~1.8 pg·m^(-3),其中秋季霾天4个采样点和冬季全部采样点超出日本环境空气质量标准限值(TEQ:0.6pg·m^(-3)).1,2,3,4,6,7,8-Hp CDF和OCDD是四季空气中PCDD/Fs质量浓度的主要贡献单体,年平均贡献率分别为20.5%和14.0%,而2,3,4,7,8-Pe CDF是总TEQ贡献最大的单体,年平均贡献率为43.3%.空间分布特征表现为各采样点浓度水平与距污染源距离远近没有显著相关性;季节变化特征表现为冬季值显著高于其他季节,分析可能与冬季燃煤采暖及大气扩散条件差导致的大气颗粒物污染较重有关,与各季采样时段内大气PM_(10)和PM_(2.5)的平均浓度水平呈正相关相一致.样品中二英同族体及异构体分布指纹谱图与该焚烧设施排放烟气存在差别,主成分分析(PCA)源解析结论与指纹谱图特征分析结论一致.二英呼吸暴露剂量估算结果表明该区域人群呼吸暴露风险总体处于较为安全的水平[0.060~0.224 pg·(kg·d)^(-1)],但仍需关注大气颗粒物重污染天气发生时的呼吸暴露风险.

Ambient air was sampled and analyzed around a municipal solid waste incinerator（MSWI） in Beijing from April 2014 to January 2015 to investigate the concentrations,profiles and seasonal variations of PCDD/Fs in the region using HRGC-HRMS technique.The mass concentrations and TEQ of 2,3,7,8-substituted PCDD/Fs in the air samples ranged from 8.9 to 140 pg·m^（-3）and from 0.11 to 1.8 pg·m^（-3）,respectively.The concentration values at 4 sampling sites in haze day in autumn and all 7 sampling sites in winter were higher than the ambient air standard of 0.6 pg·m^（-3）for dioxins regulated in Japan.1,2,3,4,6,7,8-Hp CDF and OCDD dominated PCDD/Fs in all the samples for all four seasons with average contribution fractions of 20.5% and 14.0%,respectively,while 2,3,4,7,8-Pe CDF was the dominant congener contributing to TEQ（43.3%）.The spatial distribution basically exhibited a trend that the concentrations at all sites were comparable and not related to the distances from the source.Seasonal variation showed obviously higher concentration in winter than the other three seasons,which may attribute to the high concentration of ambient particulate matter due to domestic heating and worse atmospheric dispersion that occurred in winter.The homologue and congener profiles of PCDD/Fs in the air samples differed from those of the flue gas emission from the MSWI,consistent with the principle component analysis results.Dioxin inhalation exposure dose estimation showed that the dioxin inhalation exposure risk of residents living in the studied area was at a relatively safe level [0.060-0.224 pg·（kg·d）^-1].However,the dioxin inhalation exposure risk in heavily polluted seasons still needs great concerns.