珠三角典型地区挥发性有机化合物浓度水平及化学反应活性季节变化特征

Seasonal variation characteristics of concentration and chemical reactivity of VOCs in typical areas of the Pearl River Delta

为探究珠三角典型地区挥发性有机化合物(VOCs)及其化学反应活性的季节变化特征,于2016年在广东大气超级监测站,开展四季VOCs、NO x、O 3和PM 2.5的连续观测,共获得2142组有效数据。结果表明:(1)VOCs、羟基自由基消耗速率(L OH)、O 3生成潜势(OFP)和二次气溶胶生成潜势(SOAFP)均具有明显季节变化特征。VOCs的L OH由大到小依次为春季、秋季、夏季、冬季;OFP和SOAFP由大到小依次为春季、冬季、秋季、夏季。低碳(C2~C5)烯烃和苯系物对本地区L OH、OFP的贡献分别为85%、82%;苯系物对SOAFP的贡献最大,占97%~98%。(2)VOCs、NO x和PM 2.5的四季浓度日变化均反映出早晚高峰现象。观测站点所在区域在夏、秋季属于光化学反应活跃区,本地O 3浓度主要取决于上风向O 3前体物的排放状况及传输过程中的反应条件。(3)根据甲苯和苯体积比可知,观测站点受附近工业活动影响较大,且在冬、春季扩散条件不佳时影响更明显。

In order to explore the seasonal variation characteristics and chemical reactivity of VOCs in typical areas of the Pearl River Delta(PRD),the continuous observation of VOCs,NO x,O 3 and PM 2.5 was carried out at Guangdong Atmospheric Supersite(GAS)in the four seasons of 2016.During the observation period,a total of 2142 groups of valid data were obtained.The results showed that:(1)VOCs,·OH loss rate(L OH),Ozone Formation Potential(OFP)and Secondary Oragnic Aerosol Formation Potential(SOAFP)of VOCs had obvious seasonal variation characteristics during the observation period.L OH of VOCs from large to small followed by spring,autumn,summer and winter,while OFP and SOAFP of VOCs from large to small followed by spring,winter,autumn and summer.The C2-C5 alkenes and BTEX contribution to L OH and OFP in this region was respectively 85%,82%.BTEX contributed the most SOAFP in this region,and its contribution was between 97%-98%.(2)The diurnal variations of VOCs,NO x and PM 2.5 all reflected the morning and evening peaks.In the summer and autumn,the study area belongs to the active region of photochemical reaction,and the local O 3 concentration mainly depended on the emissions of its precursors at the upper wind and the reaction conditions during the transmission.(3)According to the ratios of toluene to benzene,the observation site was greatly affected by the nearby industrial activities,and the influence was more significant in winter and spring when the diffusion conditions were poor.