Preliminary Study On Indoor And Outdoor Carbonyls In The Air And Their Sources In Guangzhou

Carbonyl compounds are the most common organic pollutants in the atmosphere. They have received more and more attention due to their potential adverse health effects and their important role in the atmospheric chemistry. These compounds are directly emitted by anthropogenic and natural sources and also are formed in situ as the photochemical oxidation products of other gas-phase hydrocarbons in the atmosphere. Some carbonyls are released into indoor air from building materials and human activities, such as smoking, heating and cooking.In this study, a method was developed for measurement of the concentrations of carbonyl compounds in the atmosphere based on the USEPA. First, indoor and outdoor carbonyl compounds were studied in the hotel ballrooms in Guangzhou and the results indicated that almost all the indoor concentrations of carbonyls were higher than that of outdoors. Ballrooms are the leisure place for some people after work but they have to exposure to much higher concentrations of carbonyls than in their offices and homes. The concentrations of carbonyls in the ballrooms were affected by the ventilations and human activities. Acetaldehyde is the most abundant carbonyl and there is positive correlation between the acetaldehyde concentrations and the number of people who smoked.Then, the same method was used to study the concentrations of carbonyl compounds in the atmosphere in Guangzhou. The results showed that the concentrations had no pronounced changes between different sampling sites and times in the districts of Guangzhou. Acetone is the most abundant carbonyl in the atmosphere, followed by formaldehyde and acetaldehyde. Strong correlations were found among low molecular carbonyls in the air outside of ballrooms, but the lower correlations were found among 14 carbonyls in the atmosphere in Guangzhou. This maybe due to the sampling sites separated in the districts of the city and the strong photochemical reactions in the summer. Therefore, Vehicular exhaust was the primary source in autumn and winter while both vehicular exhaust and photochemical reactions were the major sources in summer.According to the measurements above, some important sources of carbonyls in the indoor and outdoor air were studied. It included environmental tobacco smoke (ETS), honeycomb-coal-briquette burning, oil smoke from the exhaust of restaurant and vehicular exhaust. The emissions of carbonyls had different patterns among various sources. Low molecular carbonyls were abundant in all the sources. Acetaldehyde was the highest concentrations in the ETS, while aromatic carbonyls (benzaldehyde, m/o-tolualdehyde and 2,5-dimethylbenzaldehyde) had the higher emission factors in the smoke of honeycomb-coal-briquette burning than that of others. The straight-chain compounds were relatively more abundant than the aromatic aldehydes and the branch-chain aldehydes in the oil smoke. All the target compounds were detected in the vehicular exhaust.All the information from the studies can help us to understand the concentration levels of carbonyl compounds in the atmosphere and the characteristics of the mainly sources. It is also helpful to control the emission sources and provides theoretical basis for the air quality model and for accessing the human health.