Assessment of Open Biomass Burning Impacts on Surface PM2.5 Concentration

Abstract

Open biomass burning plays an important role in the formation of heavy pollution events during harvest seasons in China by releasing gases and particulate matters into the atmosphere. A better understanding of open biomass burning in China is required to assess its impacts on the air quality and especially on heavy haze pollution.By using datasets of MODIS fire spot, land cover, vegetation cover, biomass loading and emission factors, a biomass emission model is developed, which is then embedded to an air quality model (WRF-CUACE) to quantitatively assess impacts of biomass burning on surface PM2.5 concentration in China through sensitivity tests. Three simulation scenarios are designed to ensure that simulation results of revised scenarios are closer to actual atmospheric conditions according to the model evaluation. Results show that in October 2014, Northeast, South and Southwest China are regions of the largest contribution to biomass burning with the average monthly increased concentration of PM2.5 up to 30-60 μg·m-3, and even more than 100 μg·m-3 at local regions. In North, East and South China, biomass burning generally provides a contribution of PM2.5 concentration of 5-20 μg·m-3. In terms of the percentage of relative contribution, the value in Northeast China exceeds 50% in most regions. In South China, the relative contribution of biomass burning reaches 20%-50%, and even exceeds 60% in parts of Southwest China. While in North, Central and East China, the relative contribution of biomass burning is generally 10%-20%. In addition, the contribution of secondary aerosols in PM2.5 from biomass burning is also estimated. A group of sensitivity experiments are set up, with and without the gas emission from biomass burning. In Northeast China, the contribution concentration of secondary aerosols is only 0-10 μg·m-3, significantly lower than that in North, Central, East and South China, where the contribution concentration of secondary aerosols could reach 5-15 μg·m-3. In terms of the percentage of contribution to secondary aerosols in PM2.5 from biomass burning, the value in Northeast China is the lowest, which is less than 30% in most regions. And in South and Southwest China, the contribution percentage is relatively larger, which can reach 30%-50%. While in North, Central, East China and vast remote areas, the contribution percentage almost exceed 70%. Based on the above analysis, it is found that the percentage of secondary aerosols in PM2.5 from biomass burning drops when the biomass burning grows.

Keywords

• open biomass burning
• emission model