Carbonaceous aerosols in fine particulate matter of Santiago Metropolitan Area, Chile

Abstract

Measurements of carbonaceous aerosols in South American cities are limited, and most existing data are of short term and limited to only a few locations. For 6 years (2002-2007), concentrations of fine particulate matter and organic and elemental carbon were measured continuously in the capital of Chile. The contribution of carbonaceous aerosols to the primary and secondary fractions was estimated at three different sampling sites and in the warm and cool seasons. The results demonstrate that there are significant differences in the levels in both the cold (March to August) and warm (September to February) seasons at all sites studied. The percent contribution of total carbonaceous aerosol fine particulate matter was greater in the cool season (53 ± 41%) than in the warm season (44 ± 18%). On average, the secondary organic carbon in the city corresponded to 29% of the total organic carbon. In cold periods, this proportion may reach an average of 38%. A comparison of the results with the air quality standards for fine particulate matter indicates that the total carbonaceous fraction alone exceeds the World Health Organization standard (10 µg/m(3)) and the United States Environmental Protection Agency standard (15 µg/m(3)) for fine particulate matter.

Figure 1

Regional topography of Santiago Metropolitan Area (SMA), Chile (with 10 km grid lines). The gray area is the urban region, and the black lines represent the main routes and streets. White dots designate the three air quality monitoring stations of the MACAM-2 network that were used in this study (C: Las Condes, O: Parque O'Higgins, and P: Pudahuel).

Figure 2

Hourly mass concentration (in μg/m³) time series of PM_2.5 (light gray), organic carbon (OC, gray), and elemental carbon (EC, dark gray) in PM_2.5 at the (a) Las Condes (labeled C), (b) Parque O'Higgins (labeled O), and (c) Pudahuel (labeled P) stations. The station labels are the same as in Figure 1. Data source: National Information System of Air Quality, Chilean Ministry of the Environment, Chile.

Figure 3

Daily mass concentration (in μg/m³) in the cool (gray) and warm seasons (black) of PM_2.5(black square, grey square), organic carbon (OC; grey triangle), and elemental carbon (EC; inverted triangle) in PM_2.5 at the (a) Las Condes (labeled C), (b) Parque O'Higgins (labeled O), and (c) Pudahuel (labeled P) stations in the cool (gray line) and warm (black line,) seasons. Label of the stations in Figure 1: Las Condes: C Label, P. O'Higgins: O Label, and Pudahuel: P Label. Data source: Chilean Ministry of Health, Metropolitan area (SEREMI-RM).

Figure 4

Bivariate polar plot for the mean concentration of PM_2.5, OC, and EC for the sites under study in cold (winter and fall seasons) and warm periods (summer and spring seasons). Label of the stations in Figure 1. Las Condes: C Label, P. O'Higgins: O Label, and Pudahuel: P Label.

Figure 5

Scatter plot of OC and EC in PM_2.5, corresponding to the hourly cool and warm season datapairs, for the period from 2002 to 2007 at the three stations studied. Figures i1 and i2 (i = a, b and c) show scatter plots of all data available for the years of the study in a cool (1) and warm (2) seasons of all years. Figures i3 and i4 (i = a, b and c) show scatter plots of the minimum OC/EC ratio in the cool (3) and warm (4) seasons during the years of the study. Label of the stations in Figure 1. Las Condes: C Label, P. O'Higgins: O Label, and Pudahuel: P Label.

Figure 6

Percentage of days per year from 2002 to 2007 in which the concentration was greater than the threshold of the World Health Organization (WHO), the United States Environmental Protection Agency (EPA), and the Chilean Ministry of the Environment (MMA) standards. Label of the stations in Figure 1. Las Condes: C Label, P. O'Higgins: O Label, and Pudahuel: P Label.