和田市城区PM_(2.5)中PAHs的浓度、来源及致癌风险

Study on PAHs in PM_(2.5) in Urban Area of Hotan City:Concentration,Source and Carcinogenic Risk

2014年在新疆和田市城区分冬、春、夏、秋4个季节采集大气PM2.5样品,分析了其中16种多环芳烃(PAHs)的含量、组成和来源,并评估了其致癌风险。结果表明:PAHs浓度年均值为99.02 ng/m^3,且具有明显的季节性分布,即冬季(241.52 ng/m^3)>秋季(87.50ng/m^3)>春季(30.81 ng/m^3)>夏季(10.39 ng/m^3),冬季苯并[a]芘(Ba P)的浓度高达16.57 ng/m^3;全年PAHs以4~6环为主,冬季4环PAHs比例(46.03%)明显高于夏季的比例(15.97%),表明气粒两相分配对PAHs分布有显著影响。PAHs浓度与气温和风速显著负相关,与相对湿度显著正相关,表明相对低的气温和风速、相对高的湿度是冬季PAHs污染较高的重要原因。特征比值法源解析结果显示,PAHs主要来源于燃烧源,其中冬季PAHs来源以燃煤及薪柴燃烧为主,春、秋季以燃煤源和交通源的混合污染来源为主,夏季以交通源为主。后向轨迹分析表明,除和田市东北部的局地输送外,来自中亚、西亚其他国家外部输入的气团也对和田市城区PAHs有重要影响。苯并[a]芘毒性当量浓度(Ba P_(eq))年均值为10.51 ng/m^3,终身呼吸性肺癌风险(CR)为9.14×10^(-4),是美国环保署(USEPA)可接受致癌风险指数的9.14倍,表明和田市城区居民具有一定的潜在健康风险。

Seasonal sampling of ambient air PM_（2.5） was conducted in Hotan＇s urban area in 2014. This paper reported on the samples analysis concerning concentrations, compositions, sources of 16 priority PAHs and the evaluation of their carciongenic risks. The results suggested that the annual mean concentration of total PAHs was 99.02 ng/m3, with notable seasonal variation as winter（241.52 ng/m3）autumn（87.50 ng/m3） spring（30.81 ng/m3）summer（10.39 ng/m3）, and especially, concentration of benzo（a）pyrene was as high as 16.57 ng/m3 in winter; PAHs were dominated by 46 rings for the whole year, the proportion of 4-ring PAH in winter（46.03%） was obviously higher than in summer（15.97%）, reflecting the effects of two-phase（gas-particle） partitioning on PAHs distributions. It was showed that PAHs were significantly negative correlated with temperature and wind speed, while positive correlated with relative humidity, which indicated that the relatively lower temperature, wind speed and higher humidity were the main cause leading to the higher PAHs pollution in winter. Furthermore, the source apportionment by PAH diagnostic ratios indicated that PAHs were mainly from combustion sources： coal and wood burning were the main sources in winter, the mixed sources of coal and traffic dominated in spring and autumn, and traffic wasthe crucial source in summer. The air mass coming from Central and West Asia in addition to the north and northeast parts of Hotan had greatly affected the distribution of PAHs. Besides, Ba P equivalent carcinogenic potency（Ba Peq） was calculated to evaluate the cancer risk of carcinogenic PAHs, the average concentration of Ba Peqwas 10.51 ng/m3 and the value of cancer risk（CR） was 9.14×10（-4）, 9.14 times the acceptable carcinogenic risk index recommended by the USEPA, which indicated that there were certain potential health risks facing the residents of Hotan City.