July 2007
Trends in the Elemental Composition of Fine Particulate Matter in Santiago, Chile, from 1998 to 2003
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Sonja N. Sax,
Gradient Corporation, Cambridge, MA
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Petros Koutrakis,
Harvard School of Public Health, Boston, MA
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Pablo A. Ruiz Rudolph,
Centro Mario Molina Chile, Santiago, Chile; and Harvard School of Public Health, Boston, MA
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Francisco Cereceda-Balic,
Department of Chemistry, Federico Santa Maria Technical University, Valparai´so, Chile
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Ernesto Gramsch,
Department of Physics, University of Santiago, Santiago, Chile
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Pedro Oyola,
Centro Mario Molina Chile, Santiago, Chile
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AbstractSantiago, Chile, is one of the most polluted cities in South
America. As a response, over the past 15 yr, numerous
pollution reduction programs have been implemented by
the environmental authority, Comisio´n Nacional del Medio
Ambiente. This paper assesses the effectiveness of
these interventions by examining the trends of fine particulate
matter (PM2.5) and its associated elements. Daily
fine particle filter samples were collected in Santiago at a
downtown location from April 1998 through March
2003. Additionally, meteorological variables were measured
continuously. Annual average concentrations of
PM2.5 decreased only marginally, from 41.8 g/m3 for the
1998–1999 period to 35.4 g/m3 for the 2002–2003 period.
PM2.5 concentrations exceeded the annual U.S. Environmental
Protection Agency standard of 15 g/m3.
Also, approximately 20% of the daily samples exceeded
the old standard of 65 g/m3, whereas approximately half
of the samples exceeded the new standard of 35 g/m3
(effective in 2006). Mean PM2.5 levels measured during
the cold season (April through September) were three
times higher than those measured in the warm season
(October through March). Particulate mass and elemental
concentration trends were investigated using regression
models, controlling for year, month, weekday, wind
speed, temperature, and relative humidity. The results
showed significant decreases for Pb, Br, and S concentrations
and minor but still significant decreases for Ni, Al,
Si, Ca, and Fe. The larger decreases were associated with
specific remediation policies implemented, including the
removal of lead from gasoline, the reduction of sulfur
levels in diesel fuel, and the introduction of natural gas.
These results suggest that the pollution reduction programs,
especially the ones related to transport, have been
effective in reducing various important components of
PM2.5. However, particle mass and other associated element
levels remain high, and it is thus imperative to
continue the efforts to improve air quality, particularly
focusing on industrial sources.
ImplicationsThis paper reports particle composition measurements
taken in Santiago from 1998 to 2003. Although PM2.5 concentrations
did not decrease substantially in the 5-yr period
of the study, there were large decreases in Pb, Br, and S as
a result of the phaseout of leaded gasoline and the introduction
of low sulfur fuels. These results show that the
pollution reduction programs implemented by the environmental
authority have been successful. However, particle
mass levels continue to exceed national and international
standards, thus, efforts to reduce air pollution should
continue.
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