Observation of aerosol optical properties and particulate pollution at background station in the Pearl River Delta region

Measurements of fine particles (PM2.5), coarse particles (PM10) and aerosol optical properties were carried out at a background station-Dinghushan in the Pearl River Delta (PRD) region from 2009 to 2012. It showed that the long-term mean concentrations of PM2.5 and PM10 were as high as (51 ± 31) μg/m3 and (76 ± 43) μg/m3, respectively. Particulate pollution in the PRD region was mitigated over the last four years, and the annual mean concentrations of PM2.5 was decreased to (39 ± 25) μg/m3 in 2012 from (65 ± 33) μg/m3 in 2009. The concentrations of PM2.5 and PM10 were low in summer and high in the other three seasons. The correlation between the daily concentrations of PM2.5 and PM10 was generally high (R > 0.90). The long-term mean PM2.5/PM10 ratio reached up to 0.67, the ratio was high in autumn (0.71) and low in summer (0.57). Atmospheric visibility was poor, the long-term mean of aerosol optical depth (AOD) at 500 nm was 0.91 ± 0.40, and Ångström exponent was 0.97 ± 0.36. The values of AOD were low in winter and summer, and high in spring and autumn. The correlation between particulate matter (PM) concentrations and AOD was high. The correlation coefficient in dry season (October–next March) was better than that was in wet season (April–September). In addition, the correlation also demonstrated great differences for different air masses.