Atmospheric removal of PM2.5 by man-made Three Northern Regions Shelter Forest in Northern China estimated using satellite retrieved PM2.5 concentration

摘要

Atmospheric removal of PM_(2.5) by the Three Northern Regions Shelter Forest (TNRSF) - the so called Green Great Wall (GGW) in northern China through dry deposition process was estimated using a bulk big-leaf model and a vegetation collection model. Decadal trend of PM_(2.5) diy deposition flux from 1999 to 2010 was calculated from modeled dry deposition velocity and air concentration retrieved from the satellite remote sensing. Dry deposition velocities of PM_(2.5) calculated using the two deposition models increased in many places of the TNRSF over the last decade due to increasing vegetation coverage of the TNRSF. Both inaeasing deposition velocity due to forest expansion and PM_(2.5) atmospheric level contributed to the increasing deposition flux of PM_(2.5). The highest atmospheric deposition flux of PM_(2.5) was found in the Central-north region covering Beijing-Tianjin-Hebei area, followed by the Northwestern and the Northeastern regions of the TNRSF. While greater coïlection of PM_(2.5) by vegetation was identified in the Northeastern region of the TNRSF due to higher forest coverage over this region, the most significant incline of the PM_(2.5) atmospheric removal due to vegetation collection was discerned in the Central-north region because of the most rapid increase in the vegetation coverage in this region. A total mass of 2.85 x 10~71 PM_(2.5) was estimated to be removed from the atmosphere through dry deposition process over the TNRSF from 1999 to 2010. The two deposition models simulated similar magnitude and spatial patterns of PM_(2.5) dry deposition fluxes. Our results suggest that the TNRSF plays a moderate role in PM_(2.5) uptake, but enhances PM2.5 atmospheric removal by 30% in 2010 than in 1980.