Evaluating the first‐order effect of intraannual temperature variability on urban air pollution

Abstract

[1] The direct effect of intraannual temperature variability on ozone and PM2.5 concentrations at the urban scale was simulated using a high-resolution air quality model that tracks the temperature-dependant formation of secondary organic and inorganic aerosol components. Calculations show that the concentration of ozone and non-volatile secondary particulate matter will generally increase at higher temperatures due to increased gas-phase reaction rates. The concentration of semi-volatile reaction products also will increase at higher temperatures, but the amount of this material that partitions to the particle-phase may decrease as equilibrium vapor pressures rise. Calculations performed for Southern California on September 25, 1996 predict that intraannual temperature variability may cause peak ozone and PM2.5 concentrations to fluctuate by up to 16% and 25% respectively. 24-hour average PM2.5 concentrations will decrease with increasing temperatures for inland portions of the South Coast air basin during most of the day. Slight increases in 24-hour average PM2.5 concentrations were predicted for coastal regions. The majority of the predicted shift in PM2.5 concentrations was related to increased production rates for nitric acid and condensable organic compounds balanced against increased volatilization of these products. Semi-volatile particulate ammonium nitrate concentrations are most sensitive to volatilization losses at hotter temperatures and when the ratio of gas-phase ammonia to nitric acid concentrations is approximately unity. Background sulfate particles and particles released from non-catalyst equipped gasoline-powered engines, diesel engines, and food cooking were shifted to smaller sizes as ammonium nitrate volatilized at hotter temperatures.

The toxicology of climate change: Environmental contaminants in a warming world

“…Climate change is projected to generally degrade air quality, but for tropospheric ozone and PM, there continues to be uncertainty as to the direction and magnitude of changes in environmental distribution patterns (Aw and Kleeman, 2003;Ebi et al, 2006;IPCC, 2007c,e;Racherla and Adams, 2006).…”

“…However, despite estimates of net global declines, several studies project regional scale increases in ozone pollution linked to climate change (Aw and Kleeman, 2003;Cheng et al, 2007;Hogrefe et al, 2004;Langner et al, 2005;Stevenson et al, 2006). For example, tropospheric ozone concentrations are predicted to increase in Southern California as a result of accelerated gas phase reaction rates associated with rising temperatures (Aw and Kleeman, 2003).…”

“…For example, tropospheric ozone concentrations are predicted to increase in Southern California as a result of accelerated gas phase reaction rates associated with rising temperatures (Aw and Kleeman, 2003). Similarly, using the IPCC A2 high CO 2 emission scenario, Hogrefe et al (2004) estimate increases in summertime average daily maximum 8-hour ozone concentrations over the eastern U.S. of 2.7 ppb by the 2020s, 4.2 ppb by the 2050s, and 5.0 ppb by the 2080s.…”

“…Climate change-induced shifts in precipitation patterns will also affect PM fate and behavior (Aw and Kleeman, 2003;Forster et al, 2007;Racherla and Adams, 2006). PM consists of both natural and anthropogenic sources of soils, dusts, acids, organic chemicals, and metals.…”

“…1, Legend Item B). Aw and Kleeman (2003) modeling of PM interactions with climate change in the Southern California region indicate that non-volatile secondary PM may increase with rising temperatures, but that semi-volatile secondary PM could increase or decrease.…”