Total organic carbon atmospheric aerosols

Solvent extraction combined with chromatographic techniques generally is used to study organic compounds associated with the atmospheric aerosol. Combustion to C02 is additionally used to determine total organic carbon in the samples. This includes elemental carbon present as soot. Due to the limited efficiency of solvent extraction and because many compounds show-... 

Particulate emissions are by-products of fuel combustion, industrial processes, and motor vehicles and are believed to have a significant potential for causing adverse health effects. Carbonaceous material present in atmospheric aerosols is a combination of elemental carbon and organic and inorganic compounds. Particulate matter may also consist of fly ash, minerals, or road dust and contain traces of a number of heavy metals. Population-based studies have consistently found that the association between adverse respiratory effects and particulate concentrations occurs in a number of regions throughout the United States. This association is strongest for PM]o and PM2.5 indices (particulate matter less than 10 and 2.5 pm in diameter, respectively). The observed adverse effects include increases in total mortality, mortality due to respiratory and cardiovascular causes, chronic bronchitis, and hospital visits and admissions for asthma. Elderly or unhealthy individuals and infants appear to comprise subpopulations that are most sensitive to the adverse health effects of PM. 

Carbon-14 content is measured by specially designed gas proportional counters (7. Aerosol samples are first converted to CO2 by combustion in a macroscale version of the thermal evolution technique. A clam shell oven was used to heat the sample for sequential evolution of organic and elemental carbon under equivalent conditions. Due to the possibility of thermal gradients, conditions in the macroscale apparatus were adjusted to produce the same recoveries of total carbon (yg C per cm of filter area) as for the microscale apparatus. Carbon-14 data are reported as % contemporary carbon based on the 1978 1 C02 content in the atmosphere. Aldehyde data referred to in this paper were obtained by impinger sampling in dinitrophenylhydrazine/acetonitrile solution and analysis of the derivatives by HPLC with UV detection (12). Olefin measurements were made by a specially designed ozone-chemiluminescence apparatus (13) difficulties in calibration accuracy and background drift with temperature limit its use to inferences of relative reactive hydrocarbon levels. 

As seen in Fig. 10b, total diacids accounted for 0.8-6.2% of TC (av. 3.1%, median 3.0%) with a maximum in August. These values are consistent with those (1.1-4.9%, av. 3.2%) reported in the western Pacific at 35°N to 40°S (Sempere and Kawamura, 2003). However, they are three times higher than those (0.18-1.8%, av. 0.95%) obtained in Tokyo (Kawamura and Ikushima, 1993), although a summer time maximum was found in Tokyo. Higher values for Jeju Island indicate that diacid carbon contributes more to the total aerosol carbon possibly due to higher emissions of organic precursor compounds in the source areas than in Tokyo and their subsequent conversion to dicarboxylic acids in the atmosphere. 

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