Study Of Carbonyl Compounds In The Atmosphere Of Shanghai By Using Filter Packing System(FP) And GC/MS

Secondary organic aerosol(SOA), the major species in the atmospheric particles, was the research focus in atmospheric environmental chemistry. SOA can be directly or indirectly formed by the carbonyl compounds because they played important roles in atmospheric photo-oxidation and heterogeneous reaction by non-radical and radical reactions. However, the concentrations of carbonyl compounds were very low in the atmosphere(ppb or below ppb level) and they were easily volatized, decomposed and oxidized as they had a strong polarity, volatility and reactivity. Therefore, the detecting methods of carbonyl compounds had been a challenging problem.In recent years, many researchers focused on the gas phase carbonyl compounds. Few studies had simultaneously detected both in the gas and particle phase carbonyls in the atmosphere. Recently, the annular denuder-filter pack(AD-FP) system was used to collect gaseous and particle carbonyl compounds at the same time. We also established a method to simultaneously collect the gaseous and particle carbonyls by using AD-FP system coated with the DNPH or PFBHA and followed detected by GC/MS. However, the sample system had obvious drawbacks, including the complexity of the preparatory work before sampling and the vulnerability the annular denuder. On the other hand, AD-FP system was difficult to be used for field sampling because of its large size and its exorbitant price.In this paper, we compared the collection efficiency of three sampling systems, including AD-FP, FP and FRM Omni PM2.5. Finally we chose the FP system to collect the carbonyl compounds in Baoshan district of Shanghai atmosphere. The Filter-Pack system was easy to operate and fit to sample in the field. Samples were extracted by hexane and then analyzed by GC/MS. The chromatograms of 15 standard samples were well separated. The recovery of the target compounds were from 79.3% to 100%. And the collection efficiency of the target compounds on the single filter was 75% to 89%, while the total collection efficiency on the two filters was over 94%. The good collection efficiency was achieved at the coating amount of PFBHA was 12 μmol and the sampling flow was 4 L?min-1 for 4 h.In order to explore the concentration levels and variations of carbonyl compound in the atmosphere, the FP system was applied for collecting gaseous and particulate carbonyl compounds simultaneously in Shanghai ambient air. Seasonal and diurnal variations of carbonyl compounds as well as the gas-particle partitioning were discussed. The results showed as follows: 1) 15 target carbonyl compounds were all detected in Shanghai ambient air, including 13 mono-carbonyls and 2 dicarbonyls; 2) the carbonyl compounds showed significant seasonal and diurnal variations with higher concentrations in summer, the concentrations of gaseous carbonyls reached the maximum at noon while the particle phases achieved the minimum value at the same time; the total concentration of carbonyls was 33.8±15.9 μg?m-3 in summer, significantly higher than the level in winter(10.5±5.0 μg?m-3) and spring(14.0±7.0 μg?m-3); 3) gas-particle partitioning of carbonyl compounds was found to be positively correlated with ambient temperature while negatively correlated with relative humidity. Compare to the annular denuder–filter pack(AD-FP) system, the FP system was more suitable for field observation.