Black carbon aerosols over an urban area in south-eastern Spain: Changes detected after the 2008 economic crisis
Metadatos
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Elsevier
Materia
Black carbon Anthropogenic aerosol Emission decline
Fecha
2011-07-30Patrocinador
Spanish Ministry of Science and Technology through projects CGL2010-18782 and CSD2007-00067; Andalusian Regional Government through projects P10- RNM-6299 and P08-RNM-3568Resumen
Continuous measurements of black carbon (BC) concentrations performed at Granada, an urban location in
southeast Spain, using aMulti-Angle Absorption Photometer from December 2005 to November 2008, are
analysed and discussed here. The daily mean BC concentrations showed considerable day-to-day variations
and were found to vary from low values of 0.5 mgm 3 to high values of 8.6 mgm 3, with overall mean
and standard deviation of 3.0 1.5 mgm 3. The annual mean BC concentrations were similar during 2006
and 2007 (3.2 1.4 mg m 3 and 3.1 1.6 mg m 3, respectively), but decreased by about 16e18%
to 2.6 1.4 mgm 3 in 2008. This reduction is not only observed in the mean value, but also in the median,
third and first quartiles. A ManneWhitney test at 0.05 significance level confirms that the BC concentration
difference between 2006 and 2007 is statistically no significant while the BC concentration in 2008 tends
to be less than that in 2006e2007. Analysis of meteorological conditions suggested that although the dayto-
day variations in BC concentrations were drivenmostly by meteorology, the reduction in the use of fossil
fuels due to economic slowdown contributed significantly to the observed decrease in BC concentrations in
2008. Under conditions dominated by local source emissions, the effect of the economic crisis on BC
concentration was more pronounced. For the three analysed years, BC concentrations obtained during
winter were higher than those measured during summer, probably due to increased emissions from
domestic heating and less intense vertical mixing in winter season, which lead to the confinement of the BC
particles near the surface. The monthly mean BC concentrations were lower in 2008 than in 2006e2007 for
almost every month of the year. In all years BC concentrations exhibited a clear diurnal pattern, with two
maxima and two minima within a day. There were no differences among the daily patterns for 2006, 2007
and 2008 except for a general reduction in BC concentrations on 2008, especially during morning and
evening traffic hours. For every day of the week, BC concentrations were lower on 2008 than in 2006 and
2007 and this reduction was more pronounced on working days, when BC concentrations were high.