The blocking effect of atmospheric particles by forest and wetland at different air quality grades in Beijing China.

To understand the effect of forests and wetlands on air quality, the PM10 and PM2.5 concentration and meteorological data were collected in the forest and wetland in the Beijing Olympic Forest Park in China from May 2106 to May 2017. The blocking rates of forest and wetland to PMs were calculated under different air quality grades which were divided into six levels base on a technical regulation. And we have got three main conclusions. (1) The diurnal variations of PMs were different in the forest and wetland. It showed a first decrease and then an increase in the forest; the lowest value (PM10 = 40.00 µg/m3, PM2.5 = 5.37 µg/m3) was at approximately 12:00. In the wetlands, the lowest values were recorded at 16:00 (PM10 = 39.63 µg/m3 and PM2.5 = 15.89 µg/m3). (2) Another result showed that the blocking in the forest were significantly higher than that at the wetlands (P < .05), and the blocking effects were much better under lower air quality grades. The blocking rate of PM10 and PM2.5 was the highest when the air quality is excellent in the forest. When it comes to wetland, the highest blocking rate of PM10 appears at good air quality, and the highest of PM2.5 was at serious polluted. (3) In addition, there was negative correlation between PM concentrations and temperature, whereas the correlation between PM concentrations and relative humidity is positive. However, the correlation between blocking and meteorological parameters is weak.