典型钢铁企业VOCs污染特征及SOA生成潜势估算

摘要

To characterize air pollution from the iron and steel industry, pollutants such as VOCs, PM2. 5 , and NMHC were measured on-line at selected industrial sites in July 2016. The secondary organic aerosol ( SOA) formation potentials were estimated based on the FAC coefficient. The average concentration of VOCs was (106. 08±63. 81) μg∕m3 during the sampling period. The level of VOCs in the air correlated well with that of NMHC ( R2>0. 8, P<0. 05) . The main categories of VOCs were alkanes and aromatics. The concentrations of benzene and toluene increased by 47. 0% and 37. 2% respectively during the episode of high ozone concentrations. During the period of high VOCs concentration, aromatic hydrocarbons contributed 46. 0% of VOCs due to the emissions of BTEX ( benzene, toluene, ethylbenzene and xylene) from coking in the iron and steel industry. The peak concentrations of VOCs, NMHC, alkanes and aromatic hydrocarbons occurred once in the morning and once in the evening. The diurnal variation of olefin concentration was characterized by a single peak in the midday, as the concentration of isoprene was affected by natural source emissions. The SOA formation potential was observed to be 2. 54 μg∕m3 , 76. 4% higher than that of urban areas, indicating SOA from steel enterprises has significant contribution to PM2. 5 . Benzene, m-xylene, ethylbenzene, o-di-p-xylene and toluene, considered as aromatic hydrocarbons, contributed 97. 2% to the formation of SOA. To control VOCs pollution from the iron and steel industry, more attention should paid to control of BTEX, while alkane emissions should not be also ignored.%为了解钢铁企业的大气污染特征,使用在线监测仪器于2016年7月对某典型钢铁企业VOCs(挥发性有机化合物)、PM2.5和NMHC(非甲烷烃)等污染物进行观测,同时基于FAC(气溶胶生成系数)估算了该区域的SOA(二次有机气溶胶)生成潜势.结果表明:观测期间ρ(总VOCs)为(106.08±63.81)μg∕m3,与ρ(NMHC)(以C计)的相关系数(R2)达到了0.8(P<0.05)以上;VOCs中主要类别为烷烃和芳烃;ρ(O3)超标期间的ρ(苯)和ρ(甲苯)分别比ρ(O3)未超标时间段高47.0%和37.2%,并且高ρ(总VOCs)期间芳烃占比高达46.0%,这可能与钢铁企业在炼焦时苯系物(苯、甲苯和二甲苯)排放有关.ρ(总VOCs)、ρ(NMHC)、ρ(烷烃)、ρ(芳烃)和ρ(乙炔)均呈早晚高峰值的日变化特征,而ρ(烯烃)由于异戊二烯受天然源排放影响,呈午间单峰值的特征.观测期间的SOA生成潜势为2.54μg∕m3,较城区高出76.4%,显示钢铁企业SOA对PM2.5具有一定贡献;其中芳烃对SOA生成贡献高达97.2%,主要贡献组分包括苯、间∕对-二甲苯、乙苯、苯、邻-二甲苯.研究显示,钢铁企业VOCs污染治理应重点控制苯系物,同时烷烃的排放也不容忽视.