Construction And Application Of A Real-time Emission Model Of Open Biomass Burning

Open bio-mass burning plays an important role in the formation of heavy pollution events during harvest seasons in China by releasing the trace gases and particulate matters into the atmosphere.A better understanding of spatial-temporal variations of open bio-mass burning in China is required to assess its impacts on the air quality and especially on the heavy haze pollution.In this study,by using the datasets of MODIS fire spot,land cover,vegetation cover,bio-mass loading and emission factors,a real-time emission model of bio-mass burning was constructed,which was then embedded to an air quality model?WRF-CUACE?to form an air quality forecasting system including the effect of bio-mass burning.On the one hand,the system can be used to carry out forecasting and improve the effect of model results.On the other hand,it can also be used to quantitatively assess the impact of bio-mass burning on China's air quality in historical periods.Firstly,based on the above work,the temporal and spatial distribution of open bio-mass burning in China was studied.It was found that the fire spots were found mainly concentrated in three key periods?March-April,June and October-November?and two zones?Zone 1 and Zone2?with inter-annual variations of burned areas.In addition,the contribution of major vegetation types burning was studied,the cropland occupied the largest proportion of burned area of more than 70%in any period time,followed by forest.Finally,from the perspective of climate and human activities,the causes of inter-annual variations were discussed.By comparing the average temperature and precipitation in the two zones from 2013 to 2017,it was found that the burned forest area was positively related to the average temperature of the zones and negatively related to the average precipitation.At the same time,the impact of the El Ni?o events on bio-mass burning was discussed.In addition,based on the above model,the impact of bio-mass burning on the surface PM_2.5concentration in China in October 2014 was quantitatively evaluated by sensitivity test.The results showed that in October 2014,Northeast China,South China and Southwest China were the regions of the largest contribution to bio-mass burning with the average monthly increased concentration of PM_2.5 up to 30-60?g/m³,and even more than 100?g/m³ at local regions.In North,East and South China,bio-mass burning generally provided a contribution of PM_2.5concentration of 5-20?g/m³.In terms of the percentage of relative contribution,the value in Northeast China exceeded 50%in most regions.In South China,the relative contribution of bio-mass burning reached 20%-50%,and even exceeded 60%in parts of Southwest China.While in North,Central and East China,the relative contribution of bio-mass burning was generally between 10%and 20%.In addition,it was found that,more severe bio-mass burned,smaller the percentage of secondary aerosols in PM_2.5 from bio-mass burning was,and vice versa.