深圳大学城园区典型OVOCs污染特征与来源解析

Pollution characteristics and source apportionment of typical OVOCs in Shenzhen University Town

采用质子转移反应质谱仪(PTR-MS)对深圳大学城园区2017年不同季节(分干湿两季)的6种典型OVOCs和其他非甲烷烃类(NMHCs)进行连续在线监测,分析其干湿季的浓度特征与日变化规律,并应用光化学龄的参数化方法开展OVOCs的来源解析.结果表明,在观测的6种OVOCs中,甲醇的平均浓度最高,达10×10^(-9)～12×10^(-9),其次是乙酸、丙酮和乙醛,约2～5×10^(-9),甲酸和丁酮的含量最低,仅1×10^(-9)～2×10^(-9).通过日变化观察到的OVOCs湿季峰值浓度时间明显早于干季,乙醛表现出与臭氧(O3)相似的日变化特征,揭示了其可能存在二次来源;甲醇和丁酮的峰值浓度时间均早于O_3,可能存在重要的一次排放源.采用光化学龄模型解析出日间污染物来源比例:在污染较重的干季,甲醇、乙醛、丙酮和丁酮的人为一次源占主导,甲酸和乙酸的二次源是主要贡献者;在较清洁的湿季,天然源成为乙醛、丙酮、丁酮、甲酸和乙酸的主要来源.

Online measurements of typical ambient oxygenated volatile organic compounds(OVOCs)and other non-methane hydrocarbons(NMHCs)were conducted in different seasons(dry and wet seasons)of 2017 in Shenzhen University Town utilized a proton transfer reaction mass spectrometer(PTR-MS).We explored their composition characteristics and diurnal variations,and then quantified different sources of typical OVOCs based on the photochemical age-based parameterization method.Results showed that the mean concentrations of methanol were the highest both in dry and wet seasons(up to 10×10-9~12×10-9)among the measured OVOC species,followed by acetic acid,acetone and acetaldehyde(approximately 2×10-9~5×10-9),while those of formic acid and methyl ethyl ketone(MEK)were always the lowest(approximately 1×10-9~2×10-9).The peak concentrations of measured OVOCs in wet seasons were found significantly earlier than that in dry seasons,and the diurnal variation in the concentration of acetaldehyde was quite similar to that of ozone(O3),suggesting that the elevated concentration throughout the daytime may originated from secondary oxidation.While the peak concentrations of methanol and MEK were found much earlier than that of O3,indicating that they may have prominent contributions from primary emission.According to the OVOCs source apportionments,anthropogenic primary sources played the key roles for methanol,acetaldehyde,acetone and MEK in dry seasons,while formic acid and acetic acid were dominated by anthropogenic secondary sources.Besides,biogenic sources were the dominant source of acetaldehyde,acetone,MEK,formic acid and acetic acid in wet seasons.