An Approach for Straw Burning in China to Minimize Air Pollution

Agricultural residue burning has been recently limited or banned during harvest seasons in China due to air pollution concern. But this policy is unlikely to be a long-term solution without providing effective alternative approaches for farmers to remove straw. In fact, straw burning in many areas of China is still very common, indicating a need to explore other solutions to air pollution problem from straw burning. This study proposes approach based on the role of rainfall in removing smoke particles. For a severe air pollution event happened during a period (usually under dry condition) in a specific region that was accompanied by massive straw burning nearby or in a remote area, we find a rainfall event before or after the period and move the burning from the actual date (s) to a time just before the rain event. We assume that this would substantially reduce air pollution with washing out by rain. To evaluate this assumption, HYSPLIT simulation of 8 air pollution events in China were conducted, with straw burning spots and emissions from the Global Fire Emissions Dataset as well as crop yield information, meteorological data from the NOAA/NCAR global reanalysis, and air quality data from ground PM_2.5 measurements. A majority of the events had PM_2.5 values over 100 μg m-3. The concentrations are reduced by 50-95% with application of proposed approach. This suggests that, in the case of policy permitting, farmers could be advised of selecting burning date according to precipitation prediction so that straw is burned with possibly minimum air pollution consequence.