利用2,4-二硝基苯肼采样管采样-高效液相色谱仪分析的方法,在济南市夏季典型臭氧污染时期(2022年6月14~22日)对两个不同市区点位(建大和创业园)大气中醛酮化合物开展同步采样分析,利用基于观测的化学箱式模型(OBM)对主要醛酮化合物的光化学反应进行模拟,识别主要醛酮化合物的二次生成途径及重要前体物.采样期间醛酮化合物总浓度为(19.78±9.83)×10-9,甲醛、乙醛和丙酮贡献率分别为36.75%、21.39%、14.64%,是最主要的醛酮化合物.建大点位甲醛浓度存在午间与夜间双峰高值,创业园点位甲醛浓度存在早晚高峰变化特征,两点位乙醛浓度呈"夜高昼低"日变化特征.两点位甲醛和乙醛特征比值(C1/C2)分别为1.97、1.47,乙醛和丙醛特征比值(C2/C3)分别为9.27、8.76,建大点位C1/C2存在明显的午间峰值.OBM模拟结果显示,甲醛最大生成速率为6.17×10-9h-1,乙醛最大生成速率为1.67×10-9h-1,丙酮最大生成速率为0.66×10-9h-1,烷氧自由基(RO)+O2反应是二次生成的主要途径.结合相对增量反应活性(RIR)结果发现,烯烃对济南市大气中甲醛和乙醛的二次生成有重要影响,乙烯、异戊二烯和丙烯是甲醛的重要前体物,丙烯和2-丁烯是乙醛的重要前体物,对人为烯烃重点排放行业进行科学合理管控将有利于阻抑大气中主要醛酮化合物的二次生成.
Carbonyl compounds in the atmosphere at two different urban sites(Jianda and Chuangyeyuan)of Jinan were synchronously collected using 2,4-dinitrophenylhydrazine sampling tubes during a typical summer ozone pollution period(from June 14 to 22,2022)and quantified using high-performance liquid chromatography.The photochemical reactions of major carbonyls were simulated with the Observation-based model(OBM)to identify the secondary formation pathways and critical precursors of these carbonyl compounds.The total concentration of carbonyl compounds was(19.78±9.83)×10 9 of which formaldehyde,acetaldehyde,and acetone accounted for 36.75%,21.39%and 14.64%,respectively.The formaldehyde concentration showed"double peak"characteristics at noon and night in Jianda and had a peak change in morning and evening in Chuangyeyuan,exhibiting relatively higher concentrations at night and minimal concentrations around noontime.The concentration ratios of formaldehyde to acetaldehyde(C1/C2)of the two urban sites were 1.97 and 1.47,respectively.The concentration ratios of acetaldehyde to propionaldehyde(C2/C3)of the two sites were 9.27 and 8.76,respectively.The maximum formation rate was simulated to be 6.17×10-9h-1 for formaldehyde,1.67×10-9h-1 for acetaldehyde,and 0.66×10-9h 1 for acetone;and the alkoxy radical(RO)+O2 reaction was the main secondary formation pathway.We also observed that alkene had an important effect on the secondary formation of formaldehyde and acetaldehyde in the atmosphere;and ethylene,isoprene,and propylene were important precursors of formaldehyde,while propylene and 2-butylene served as precursors of acetaldehyde.Obviously,effectively controlling artificial alkene emissions from industries will help mitigate the secondary formation of major carbonyl compounds in the atmosphere.