Abstract
The mass composition of Particulate Matter (PM) with an aerodynamic diameter of 2.5 microns (PM2.5) in San Joaquin Valley (SJV) is dominated by ammonium nitrate (NH4NO3), a secondary pollutant. The goal of this research was the investigation of the relationship between emissions, meteorology and PM2.5 concentrations in Fresno for the winter season. It was found that location of sites near emission sources such as freeways compared with residential sites strongly affected measured PM2.5 concentrations. It was found that although long-term trends showed declines in both emissions and PM2.5 concentrations, there was substantial variability between the years in the PM2.5–emissions relationship. Much of the yearly variation in the relationship between emissions and PM2.5 concentrations can be attributed to yearly variations in weather, such as atmospheric stability, precipitation frequency and average wind speed. There are moderate correlations between PM2.5 concentrations and temperature differences between nearby surface stations at varying elevations which explains some of the daily and seasonal variation in PM2.5. Occurrence of precipitation was related to low PM 2.5, although the higher wind speeds and lower atmospheric stability associated with precipitation likely explain some of the low PM2.5 as well as washout of PM.
Highlights
Particulate Matter (PM) is a major contributor to poor air quality in the San Joaquin Valley (SJV; [1,2])
A key goal of this research was to investigate the relationship between emissions, meteorology and PM2.5 concentrations in Fresno for the winter season
For the winters of 2015–2017, the highest PM2.5 concentrations occurred during December 2017 and January 2018
Summary
Particulate Matter (PM) is a major contributor to poor air quality in the San Joaquin Valley (SJV; [1,2]). The SJV covers the lower portion of central California, extending downward from. Sacramento through Fresno until it ends in the Tehachapi Mountains north of Los Angeles (Figure 1). Valleys limit pollutant dispersion and dilution and the topography of the SJV is a factor that contributes to the high PM concentrations, especially during winter [3]. Van Donkelaar et al [4] found high PM2.5 (PM with an aerodynamic diameter of
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