天津武清大气挥发性有机物光化学污染特征及来源

大气VOCs(挥发性有机物)是臭氧的重要前体物之一,研究其光化学污染特征和来源对控制近地面臭氧污染具有重要意义. 于2006年8月10日—9月18日在天津郊区武清采用在线监测的方法,同步观测了VOCs、O₃和NO₂等气态污染物,以及温度和紫外辐射等气象因子. 对9月10—15日臭氧浓度较高时段VOCs的浓度水平、化学反应活性、臭氧生成潜势和来源进行了分析. 结果表明:天津郊区武清环境空气中VOCs体积混合比平均浓度为24.6×10-9；VOCs主要由烷烃和烯烃组成,机动车排放、轻烃工艺、生物排放、沼气和碳氢溶剂是其重要来源. 根据等效丙烯浓度和MIR方法评估,烯烃对臭氧光化学产生的贡献占主导性地位,其中异戊二烯、丙烯、二甲苯和甲苯是臭氧生成潜势较大的物种. 通过与天津城区比较发现,郊区与城区的大气VOCs不仅组成不同,而且化学活性物种也不同. 

Photochemical Characteristics and Sources of Volatile Organic Compounds in Wuqing, Tianjin

Because volatile organic compounds (VOCs) are one of the most important precursors of tropospheric ozone, understanding their characteristics and sources are of great significance in controlling ozone. The contents of VOCs, O₃, NO₂, temperature and UV radiation were simultaneously monitored by online method from 10th August to 18th September 2006 at Wuqing Meteorology Bureau in a Tianjin suburb. In addition, the concentrations, propene-equivalent concentrations (Prop-Equiv), and OFP of the VOCs were investigated from September 10th to 15th during an ozone episode. The results showed that:1) the mean mixing ratio of hourly VOCs was about 24.6×10-9; 2) alkanes were the most abundant components followed by alkenes and aromatics, and vehicle emissions, light hydrocarbon industrial processes, biogenic sources, biogas and hydrocarbon solvents were their major sources. According to assessment using both the OH-reactivity-based method (Prop-Equiv) and maximum incremental reactivity, alkenes were shown to play a dominant role in photochemical ozone production, and isoprene, propene, xylene and toluene were the top compounds with the highest ozone formation potential. VOCs in the suburban and urban areas of Tianjin City were different, not only in the chemical composition, but also in their chemical-reactive species.