Sources, distribution and variability of airborne particles and hydrocarbons in La Plata area, Argentina

Total suspended particles (TSP), particulate- (ALIp) and semi-volatile aliphatic hydrocarbons (ALIsv) were measured in air sampled during the day and night over 7-8 months in industrial, commercial and residential sectors of La Plata, Argentina. TsP, ALIp and ALIsv ranges were 23-219 mu g/m(3), 11-447 and 12-719 ng/m(3) respectively. Maximum values were recorded at a down-town site whereas the residential station showed lower levels. Concentrations were usually higher during the day and during fall and winter. Two- and three-way ANOVA were performed to evaluate the day-night, inter-station, and inter-month variability. The amount of total variability accounted by these factors was 14, 25 and 23% (p < 0.01) for TSP; 0.8, 11 and 39% (p < 0.03) for ALIp; and 0.6, 7.9 and 15% (p < 0.3) for ALIsv, respectively. Overall, the inter-month variability prevailed; inter-station differences were most significant in the summer when the day-night variability was lower. For the particulate phase, the day-night differences were more significant at the downtown and residential sites. The composition of ALIp and ALIsv reflected the contribution from biogenic long chain odd n-alkanes and petrogenic lower molecular weight n-alkanes. Plant cuticular waxes accounted for 34-96% of ALIp with higher values during the summer and at the Residential station. A principal component analysis clearly discriminated ALIsv, almost entirely derived from exhaust and diesel fuel emissions, from ALIp composed of mixed biogenic-petrogenic sources. The lowest day-night differences observed during the summer were related to a higher proportion of biogenic "natural" material during this period of full plant grow and lower vehicle circulation. The larger day-night differences registered at the downtown station were related to an enhanced input of anthropic sources (vehicles, fossil fuels, lubricating oils) during the most active day period. (C) 1999 Elsevier Science Ltd. All rights reserved.