Weekly patterns of aerosol in the United States

Abstract

Abstract. Data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network of aerosol samplers and NOAA monitoring sites are examined for weekly cycles. At remote and rural sites, fine particle elemental carbon, crustal elements, and coarse particle mass had pronounced (up to 20%) weekly cycles with minima on Sunday or Monday. Fine particle organic carbon and mass had smaller amplitude cycles, also with Sunday or Monday minima. There was no statistically significant weekly cycle in fine particle sulfate despite a 5 to 15% weekly cycle in power plant SO 2 emissions. Although results for nitrate may be more susceptible to sampling artifacts, nitrate also showed a pronounced weekly cycle with an amplitude similar to elemental carbon. The only species found with a weekend maximum was Pb, probably from general aviation on weekends. Aerosol optical properties at NOAA monitoring sites were consistent with the IMPROVE chemical data, with significant weekly cycles in aerosol light absorption but not light scattering. These results support a large role of diesel emissions in elemental carbon aerosol over the entire United States and suggest that a large fraction of the airborne soil dust is anthropogenic. They also suggest that studies of weekly cycles in temperature, cloudiness, precipitation, or other meteorological variables should look for causes more in light-absorbing particles and possible ice nucleation by dust rather than sulfate or total aerosol. There are also implications for personal exposure and epidemiological studies of aerosol health effects.

A multi-year study of lower tropospheric aerosol variability and systematic relationships from four North American regions

“…The weekly σ sp and σ ap cycles are likely the result of a build-up of scattering and absorbing aerosols in the PBL during the first half of the week. Sunday σ ap minima and weekly cycle amplitudes of ∼ 25-35 % during spring and fall are consistent with the timing and amplitudes of weekly EC concentration cycles reported for the rural US (Murphy et al, 2008) and with weekday-weekend EC concentration differences in the urban US (Bae et al, 2004;Blanchard et al, 2008). Smaller but significant weekly σ sp cycle amplitudes of ∼ 15-20 % during spring, summer, and fall are larger than weekly cycles in OC and sulfate reported by Murphy et al (2008).…”

“…Our weekly σ sp cycle amplitude for the entire year (Fig. 3c) is similar to that of Murphy et al (2008).…”

“…Aerosol optical properties at the four sites vary primarily on seasonal timescales. Day of week variability in AOPs can be used as a tool for distinguishing anthropogenic from natural aerosol sources, since natural sources would not be expected to have AOPs that vary on weekly scales (Murphy et al, 2008). Diurnal variability is used along with co-located meteorological data to infer the influence of local pollution sources and mixing layer height on measured AOPs.…”

Variation in Parameters of Ambient Air Quality in National Capital Territory (NCT) of Delhi (India)

“…Reddy and Venkataraman [7] and Abera et al [8] note that the pollutants like CO and NO x emanate from automobile exhausts, whereas use of coal based fuels causes heavy emissions of SO 2 . Murphy (2008) et al [2] and Rosibeto et al [9] find that the levels of O 3 , NO x and particulate matter are an issue of concern in the urban environment. The variation in concentration of such pollutants strongly relates to the pattern of human activities in the city.…”

“…On the other hand, changing patterns of vehicular traffic and industrial activities also act as a factor for variation in pollution levels. Authors such as Blanchard et al [1], Murphy (2008) et al [2], Fujita et al [3], Gour et al [4], Murphy (2007) et al [5] and Kakoli et al [6] note that weekly cycle of activities of population explains divergent temporal variation in pollution levels from weekdays (Monday to Friday) to weekend (Saturday and Sunday). The paper attempts to carry out an assessment of 24 h daily average concentration of six major pollutants for a period of five years (from 2006 to 2010).…”