Abstract:

Since the Action Plan for Prevention and Control of Atmospheric Pollution was issued in 2013, the Chinese air quality has been significantly improved and the concentration of PM_2.5 has been decreasing, but near-surface ozone (O₃) has been on the rise, and it has become another key pollutant to be controlled after PM_2.5. Controlling the emission of volatile organic compounds (VOCs), which are important precursors of O₃ and secondary organic aerosols (SOA) in the air, especially industrial emissions, is the focus of air pollution prevention and control. In order to understand the VOCs pollution characteristics of industrial zones in small and medium-sized cities in Chengdu-Chongqing region, finely regulate the VOCs emission and improve the regional air quality, Suining city, the main axis of the region, was selected as the research object. The off-line monitoring data of 106 kinds of VOCs at the monitoring points and upwind background point in the industrial park in the summer of 2019 were analyzed. The VOCs pollution level and their generation potentials for O₃ and SOA were studied, and the priority species were screened out and the source apportionment was employed. The results showed that during the observation period, the volume fraction of VOCs at the monitoring point was 58.4×10^-9, which was 1.9 times of that at the background point. OVOCs and alkanes were the two components with the highest concentrations, accounting for 79.0%. The formation potentials of VOCs for O₃ and SOA at the monitoring point were 243.6 μg·m^-3 and 4.1 μg·m^-3, respectively, which were 2.0 and 2.2 times higher than those at the background point. Alkanes, OVOCs, alkenes and aromatic hydrocarbons were the components with larger potentials for O₃ generation, accounting for 97.7%, while aromatic hydrocarbons was the component with the largest potential for SOA generation, accounting for 77.8%. The predominant species of VOCs and their contributions to formation potentials of O₃ and SOA were mainly low carbon hydrocarbons, OVOCs and benzene series. Acetone, ethylene and cyclopentane were the two controlling species of VOCs and O₃. Cyclopentane, m/p-xylene and methylcyclohexane were the two controlling species of O₃ and PM_2.5. Cyclopentane was the preferred species for the joint control of VOCs, O₃ and PM_2.5. The emission sources and their contribution to VOCs were as follows: industrial emission sources (39.0%), vehicle exhaust (30.0%), use source of solvent (11.9%), gasoline volatilization sources (9.1%), combustion sources (8.9%) and plant sources (1.1%). Controlling industrial emission is the key to prevent and control VOCs pollution in the air of Suining industrial park. Except for the leading industry that prints circuit board (PCB), the main industries that emit VOCs include pharmaceutical, food, brewing and printing packaging, and so on.

Key words: volatile organic compounds, ozone formation potential (OFP), SOA formation potential (SOAFP), priority species, source apportionment

摘要：

自2013年《大气污染防治行动计划》实施以来，中国空气质量得到明显改善，PM_2.5浓度已在下降，但近地面臭氧（O₃）却呈现上升态势，已成为继PM_2.5后另一个重点防控污染物。控制O₃和二次有机气溶胶（SOA）的重要前体物挥发性有机物的排放（VOCs），尤其是工业排放，是目前大气污染防治的工作重点。为掌握成渝地区中小城市工业园区VOCs污染特征，助推VOCs排放精细化管控，改善区域空气质量，选取该区域主轴中心城市——遂宁为研究对象，分析了该市2019年夏季工业园区监控点和上风向背景点106种VOCs离线监测数据，研究了VOCs污染水平及其对O₃和SOA的生成潜势，筛选出优控物种，并进行了VOCs来源解析。结果显示：观测期间监控点VOCs体积分数为58.4×10^-9，是背景点的1.9倍，OVOCs和烷烃是浓度最高的2个组分，贡献了79.0%。监控点VOCs对O₃和SOA的生成潜势分别为243.6 μg·m^-3和4.1 μg·m^-3，是背景点的2.0倍和2.2倍，烷烃、OVOCs、烯烃和芳香烃是O₃生成潜势较大的组分，贡献了97.7%，芳香烃是SOA生成潜势最大的组分，贡献了77.8%。VOCs及其对O₃和SOA生成潜势的优势物种以低碳烃类、OVOCs及苯系物为主。丙酮、乙烯和环戊烷是VOCs和O₃防治的双控物种，环戊烷、间/对-二甲苯、甲基环己烷是O₃和PM_2.5防治的双控物种，环戊烷是VOCs、O₃和PM_2.5共同防治的优控物种。监控点VOCs排放源及其贡献率分别为：工业排放源（39.0%）、机动车源（30.0%）、溶剂使用源（11.9%）、汽油挥发源（9.1%）、燃烧源（8.9%）、植物源（1.1%），控制工业排放是防治遂宁市工业园VOCs污染的关键，除主导行业印刷电路板（PCB）外，主要排放VOCs行业还有制药、食品、酿酒和印刷包装等。

关键词: 挥发性有机物, 臭氧生成潜势（OFP）, SOA生成潜势（SOAFP）, 优控物种, 源解析