重庆市VOCs浓度特征和关键活性组分

2015年8月22日至9月26日利用在线GC-MS/FID和离线Canister-GCMS/FID采样并分析了重庆城区7个监测点位的96种VOCs,结果表明,城区总挥发性有机化合物平均体积分数为42.43×10-9,且空间分布特征为"中心城区高,周边低"。重庆本地高乙烷、高乙烯和高乙炔浓度呈区域污染现象,且城市监测点位主要受交通源、工业排放和溶剂挥发的影响,缙云山站则主要以生物源排放为主。重庆市城区气团的OH自由基反应速率平均值为8.86×10-12cm3/(mol·s),最大反应增量活性平均值为4.08 mol/mol,与乙烯相当,说明本地大气化学反应活性较强。重庆城区对OH自由基损耗速率贡献最大的组分是烯/炔烃(35%),对臭氧生成潜势贡献最大的组分是芳香烃(39%)。乙醛、乙烯和甲苯等物质是VOCs的关键活性组分。

Concentration Characteristics and Key Reactive Species of Ambient VOCs in Chongqing

96 species of VOCs were monitored using on-line GC-MS/FID and off-line Canister-GCMS/FID at 7 sites in urban areas of Chongqing from 22^th August to 26^th September in 2015. Results showed that the Total VOCs(TVOCs)concentration was 42.43×10^-9, and spatial distribution of TVOCs was high in the central urban while low in the surrounding areas. Regional pollution with high concentrations of ethane, ethylene and acetylene was found in Chongqing, and the urban sites were mainly affected by traffic sources, industrial emissions and solvent volatilization, while downtown sites were mainly affected by biogenic sources. The constant of ambient VOCs radical loss rate K_?OH was 8.86×10^-12cm³/(mol·s) and the MIR was 4.08 mol/mol, which stated that chemical reactivity of ambient air in Chongqing was similar as ethylene. For the OH radical loss rate, the (alkenes+alynes) were the most important contributors(35%), while the aromatics was the most important contributors(39%) to OFP. Respectively, the key reactive species of ambient VOCs in Chongqing were acetaldehyde, ethylene and toluene.