Characteristics of atmospheric PM in stands and non-forest cover sites across urban-rural areas in Beijing, China.

Monitoring air pollution at a city scale is essential for controlling urban air pollution in cities, especially megacities, in China. In this paper, data for 1 city center site and 5 paired (stands and non-forested) PM monitoring sites across urban-rural areas in Beijing were collected, and air PM and influential factors were analyzed. The results showed that the mean value of PM (February to December 2013) was lower in the stands (67.00 μg m) than in the non-forested sites (78.02 μg m). The diurnal variation was a bimodal double-dip type, and the average daily PM was lower in the vegetation areas than in the non-vegetation areas in both Changping Dingling (vegetation) and Changping town (non-vegetation) and showed day > night. In the typical pollution process, accompanied by an increase or decrease in PM and air quality index values, the higher the PM, the lower the wind speed. PM in the vegetation areas lagged behind PM in the non-vegetation areas on typical sunny days but not on typical rainy and windy days. On typical sunny days, the variation of PM in the vegetation areas was less than that in the non-vegetation areas. PM did not change significantly under rainy conditions and before a rain, but the variation was smaller after a rain under the typical rainfall process; under typical windy conditions, the variation was not significant. Therefore, in the typical pollution process and under typical weather conditions, the annual and diurnal variations of PM were smaller in the vegetation areas than in the non-vegetation areas. The above results confirm that the forest has a strong ability to purify air and absorb PM particulate matter and that the air quality in vegetation areas is better than the air quality in non-forested areas. [ABSTRACT FROM AUTHOR]