杭州市主城区VOCs污染特征及影响因素

采用在线气相色谱仪，2013年在杭州市主城区对56种挥发性有机物（VOCs）开展1年的连续观测. 研究VOCs组成、季节变化特征和日变化规律，总VOCs年均体积分数为42.1×10^?9，其中烷烃占54.0%，烯烃占23.4%，芳香烃占14.4%，炔烃占8.2%. 日变化规律表现为夜晚体积分数高于白天，在14:00达到全天最低值. 分析VOCs特征物种发现，机动车尾气可能是主城区VOCs的主要来源. 丙烯等效体积分数和臭氧生成潜势（OFP）均表明，VOCs反应活性较大的是烯烃，对OH活性和OFP的贡献率均超过60%，其次芳香烃和烷烃. 分析气象要素与VOCs体积分数关系发现，在11~40 °C下VOCs体积分数随着温度的升高而降低，与湿度有明显的正相关. 光照对VOCs体积分数的影响较大，降水对VOCs的冲刷不明显. 杭州全年以东风、北风为主导风向，但不同风向下的VOCs体积分数分布规律不明显. 不论是主导还是非主导风向，VOCs体积分数始终随着风速的增大而减小，对于不同季节，风速影响幅度依次是秋季>冬季>春季>夏季.

Ambient VOCs characteristics and associated effects in urban Hangzhou

Measurements of 56 volatile organic compounds (VOCs) species were obtained using online GC-FID/PID through one-year observation in urban Hangzhou in 2013. The VOCs composition, seasonal variation and diurnal cycles were analyzed. The annually averaged total VOCs was 42.1×10^?9, with alkane accounting for 54%, followed by alkene (23.4%), aromatic (14.4%) and acetylene (8.2%). The diurnal cycles of VOCs showed lower values in daytime than nighttime, with minimum value at 14:00. Further analysis on typical species showed that the vehicle emissions were possibly regarded as the major VOCs source in urban Hangzhou. Both propene-equivalent concentration and ozone formation potential (OFP) analysis indicated that alkenes contributed over 60% of total VOCs reactivity. Associated meteorological effects showed that VOCs volume fractions were negative to temperature in 11-40 °C, while positive to relative humidity. Solar radiation has significant impact on VOCs values, while wet removal effect was not obvious. Eastern and northern winds were dominated for the whole year, but the volume fraction distribution of VOCs in different wind directions was not obvious. The VOCs volume fractions decreased as wind speed increased, regardless any wind direction. For different seasons, the impact extent of wind speed followed order as autumn>winter>spring>summer.