北京市典型城区环境空气中苯系物的污染特征、来源分析与健康风险评价

自2013年6月以来,利用Airmo VOC在线分析仪在北京市典型城区开展了环境空气中挥发性有机物(VOCs)的连续观测,选取2014年4个季节中各1个月的苯系物在线数据,分析了其浓度水平、变化特征、光化学反应活性,利用美国环保署(US EPA)提出的健康风险评价方法开展了有毒有害苯系物物种的健康风险评价,结合来源分析结果,明确北京市应重点控制的苯系物污染来源。研究区观测期间环境空气中16种苯系物的质量浓度为(22.64±16.83)μg·m-3,且具有秋季冬季春季夏季的特点,其中BTEX(苯、甲苯、乙苯和二甲苯)的质量浓度为(19.27±14.46)μg·m-3,占苯系物浓度水平的41.09%~95.16%。研究区观测期间苯系物质量浓度夜间高于日间,日变化呈V字形,在13:00—15:00时质量浓度低。16种苯系物的臭氧生成潜势(OFP)的范围为66.62~170.67μg·m-3,其中间+对二甲苯、甲苯和邻二甲苯的OFP值相对较大;二次有机气溶胶生成潜势(SOAFP)的范围为0.71~1.86μg·m-3,其中甲苯、间+对二甲苯和乙苯的SOAFP值相对较大。研究区观测期间6种苯系物(BTEX和苯乙烯)的危害指数在8.19E-03~5.01E-02之间,在4个季节中对暴露人群尚不存在非致癌性风险;而Ⅰ类致癌物质苯的风险值处于7.13E-08~8.13E-06之间,在夏、秋和冬季对研究区暴露人群的人体健康均存在潜在的致癌性风险。来源分析结果表明,研究区春、秋季苯系物主要来源于机动车尾气的排放,其中春季还受到溶剂等挥发的影响,夏、冬季苯系物则主要来自于燃煤源。

Pollution Characterization, Source Apportionment and Health Risk Assessment of Benzene Homologues in the Ambient Air of a Typical Urban Area in Beijing, China

The continuous observation of volatile organic compounds (VOCs) in the ambient air has been carried out in a typical urban area of Beijing by using an Airmo VOC online monitor since June 2013.The data sets in one month for each of the four seasons in 2014 was selected to study the ambient levels,variation characteristics,pho-tochemical reactivities of 16 benzene homologues, health risk assessments of the toxic benzene homologues were made by adopting U.S.EPA's method,and the key emission sources for control management of benzene homo-logues were determined based on the source analytical results.The mass concentrations of 16 benzene homologues in the ambient air were(22.64±16.83)μg·m-3in the study area during the observation period,which had the sea-sonal variation characteristics of autumn>winter>spring>summer.The total mass concentrations of BTEX(benzene, toluene,ethylbenzene and xylene)were(19.27±14.46)μg·m-3,accounting for 41.09%-95.16% of the mass concen-trations of benzene homologues.The mass concentrations of benzene homologues were relatively higher at night than that in the daytime,and the diurnal variation was"V-shaped"with the lowest value being occurred at 13:00-15:00. The ozone formation potential(OFP)of the 16 benzene homologues were in the range of 66.62-170.67 μg·m-3,and the values of OFP for m/p-xylene,toluene and o-xylene were relatively higher;whereas,the secondary organic aero-sol formation potential(SOAFP)of the 16 benzene homologues were in the range of 0.71-1.86 μg·m-3,and the val-ues of SOAFP for toluene,m/p-xylene and ethylbenzene were relatively higher.Hazard index(HI)of BTEX and sty-rene changed from 8.19E-03 to 5.01E-02,which suggested that there was no non-cancer risk from such toxic com-pounds to the exposed population in the study area in four seasons.On the other hand,carcinogenic risk (Risk) of benzene ranged from 7.13E-08 to 8.13E-06,indicating that there was a potential cancer risk from benzene to the ex-posed population in the three seasons of summer,autumn and winter.Source analytical results showed that benzene homologues were mainly from vehicle emission source in spring and autumn,and they were also affected by solvent usage in spring;while the main source of benzene homologues was coal combustion in summer and winter.