宝鸡市夏季不同功能区挥发性有机物污染特征及健康风险评价

Characteristics and Health Risk Assessment of Volatile Organic Compounds in Different Functional Zones in Baoji in Summer

关中地区大气臭氧污染近年呈加剧趋势,研究城市不同功能区VOCs污染特征及其健康风险至关重要.夏季在宝鸡市交通区、综合区、工业区和风景区(对照点)设置4个采样点,利用气相色谱-质谱/氢火焰离子检测器联用(GC-MS/FID)和高效液相色谱(HPLC)检测了115种挥发性有机物(VOCs),分析了不同功能区的污染特征,通过臭氧生成潜势(OFP)、·OH消耗速率(L_(·OH))和二次气溶胶生成潜势(SOAFP)评估其环境影响,并计算毒性VOCs的危害指数(HI)和终生致癌概率(LCR).结果表明,采样期间交通区、综合区、工业区和风景区的φ(TVOCs)平均值分别为(59.63±23.85)×10^(-9)、(42.92±11.88)×10^(-9)、(60.27±24.09)×10^(-9)和(55.54±7.44)×10^(-9),其中交通区烷烃占比最高,其它功能区均为含氧挥发性有机物(OVOCs)占比最高;不同功能区乙醛、丙酮、正丁烷和异戊烷等均较为丰富.交通区、综合区、工业区和风景区的甲苯与苯比值(T/B)的均值分别为1.84、2.39、1.28和1.64,同时还存在较多低于1的时段,异戊烷与正戊烷比值(i/n)多数集中在1~4之间,表明宝鸡市VOCs受到机动车尾气和油气挥发、生物质和煤燃烧以及工业涂装和铸造等工业源的影响较大.4个功能区的间/对-二甲苯与乙苯的比值(X/E)均低于2,风景区最小为1.79,表明宝鸡市VOCs一定程度上受到区域传输的影响;根据甲醛与乙醛比值(C1/C2)和乙醛与丙醛比值(C2/C3),表明醛酮类VOCs存在较明显的人为排放源且受到光化学反应的影响.各功能区OFP为:工业区>风景区>交通区>综合区,OVOCs和烯烃贡献大;各功能区L_(·OH)的范围为8.77~15.82 s^(-1),工业区乙醛贡献最大,其它功能区异戊二烯贡献大;各功能区SOAFP为:风景区>综合区>交通区>工业区,甲苯、间/对-二甲苯和异戊二烯为关键物种.根据EPA的健康风险评价方法,各功能区的毒性VOCs的危害指数(HI)均低于1,处于可接受水平,但工业区HI>1的天数占总采样天数的42.86%,存在较大风险;交通区、综合区、工业区和风景区的终生致癌风险(LCR)分别为1.83×10^(-5)、1.21×10^(-5)、1.85×10^(-5)和1.63×10^(-5),均处于评价体系的第Ⅲ等级,表明有较大可能的致癌风险,LCR超过10-6的物种有:甲醛、乙醛、1,2-二溴乙烷、1,2-二氯乙烷、1,2-二氯丙烷和氯仿.

The situation of air pollution in Guanzhong Plain has been increasing in recent years;hence,it is very important to study the characteristics of volatile organic compounds(VOCs)and their health risks in urban functional zones.We analyzed 115 VOCs using gas chromatography-mass spectrometry/hydrogen ion flame detector(GC-MS/FID)and high performance liquid chromatography(HPLC)at four sampling sites in the traffic,comprehensive,industrial,and scenic zones of Baoji.We analyzed the main components and key species in the different functional zones.Ozone formation potential(OFP),·OH consumption rate(L_(·OH)),and secondary organic aerosol formation potential(SOAFP)were used to evaluate the environmental impact,and the hazard index(HI)and lifetime cancer risk(LCR)methods were employed.The results revealed that the mean values ofφ(TVOCs)in the traffic,comprehensive,industrial,and scenic zones were(59.63±23.85)×10^(-9),(42.92±11.88)×10^(-9),(60.27±24.09)×10^(-9),and(55.54±7.44)×10^(-9),respectively.The dominant contributors at the traffic zone were alkanes,and those at the other functional zones were OVOCs.Acetaldehyde,acetone,n-butane,and isopentane were abundant at different functional zones.According to the characteristic ratios of VOCs,the average ratio of toluene to benzene(T/B)at the traffic,comprehensive,industrial,and scenic zones were 1.84,2.39,1.28,and 1.64,respectively,and the ratio of iso-pentane to n-pentane(i/n)was mainly between 1 and 4.The results indicated that VOCs in Baoji were significantly affected by vehicle emissions and gasoline evaporation,biomass and coal combustion,and industrial coatings and foundry.The ratio of m/p-xylene to ethylbenzene(X/E)was lower than 2 at the four functional zones,and the minimum was 1.79 at the scenic zones;the results revealed that X/E was small,and the aging degree of air masses was high,indicating the influence of regional transport.According to the ratio of formaldehyde to acetaldehyde(C1/C2)and the ratio of acetaldehyde to propanal(C2/C3),it was suggested that there may have been evident anthropogenic emission sources,and the photochemical reaction had an important effect on aldehydes and ketones.Environmental impact assessment results revealed that OVOCs and alkenes contributed significantly to OFP and OFP from large to small was as follows:industrial zone>scenic zone>traffic zone>comprehensive zone.The range of L_(·OH)in each functional zone was 8.77-15.82 s^(-1),with isoprene contributing the most in the industrial zone and acetaldehyde contributing the most at other functional zones.The SOAFP of each functional zone was as follows:scenic zone>comprehensive zone>traffic zone>industrial zone.Toluene,m/p-xylene,and isoprene were the notable species.According to the health risk assessment of EPA,the HI of toxic VOCs in all functional zones was lower than 1,which was at an acceptable level.However,the number of days with HI>1 in industrial zones accounted for 42.86%of the total sampling days,indicating a high risk.The lifetime carcinogenic risk(LCR)of the traffic,comprehensive,industrial,and scenic zones were 1.83×10^(-5),1.21×10^(-5),1.85×10^(-5),and 1.63×10^(-5),respectively,which were all in gradeⅢof the rating system,indicating a high probability of cancer risk.Species with LCR greater than 10-6 were formaldehyde;acetaldehyde;1,2-dibromoethane;1,2-dichloroethane;1,2-dichloropropane;and chloroform.