Effects Of Agricultural Sources On Air Quality In Jilin Province Based On CMAQ Simulation

In recent years,China has introduced a series of policies and measures to improve air quality,but many cities still have air pollution problems.Jilin province is a large agricultural province in our country,and the pollutants produced by its agricultural activities further aggravate air pollution.Air pollution caused by agricultural sources cannot be ignored.Quantifying the influence of agricultural sources on environmental air quality in Jilin Province is of great significance for preventing and controlling regional air pollution in Jilin Province.In this paper,the WRF-CMAQ model simulation system was constructed to quantify the impact of agricultural sources on air quality in Jilin Province by designing fitting scenarios for increasing or decreasing emissions from agricultural sources.Since only NH₃ emissions are considered in agricultural sources in the standard MEIC,this paper refined the emission inventory of agricultural sources in Jilin Province based on the 2017 MEIC.The MEIC and the agricultural inventory of Jilin Province compiled in this paper were distributed spatiotemporal by the ISAT,and a two-layer nested grid emission inventory input file was constructed.The contribution of agricultural sources to the concentration of air pollutants in Jilin Province was evaluated in April and October when the pollution from agricultural sources was heaviest.In terms of the detailed emission inventory of agricultural sources in Jilin Province,this research focused on the emission factor method to calculate the emissions of 7 types of atmospheric pollutants(SO₂,NOx,NH₃,CO,VOCs,PM₁₀,PM_2.5)of 5 agricultural sources in Jilin Province in 2017,including straw burning,agricultural machinery emission,crop harvesting,soil tillage and grain treatment.The five agricultural sources emitted 5.1 kilotons of SO₂,47.4 kilotons of NOx,4.6 kilotons of NH₃,437.9 kilotons of CO,75.1 kilotons of VOCs,118.2 kilotons of PM₁₀ and 70.2 kilotons of PM_2.5 into the atmosphere.In addition,the uncertainty of agricultural source emission inventory was evaluated by the IPCC error transfer formula.The average uncertainty of 7pollutants was 80%,close to relevant studies and within the reasonable range.In terms of the performance verification of the WRF-CMAQ model,indexes of temperature,wind speed and atmospheric pressure were selected to verify the performance of the WRF model.The correlation coefficient between the simulated and monitored values of the three meteorological elements was between 0.51 and 0.97;NMB was between-0.02 and 0.33;NME was between 0.03 and 0.52.The WRF model has the best simulation effect for atmospheric pressure,and the simulation effect for temperature is better than that for wind speed.In general,meteorological element simulation results were consistent with the monitoring values.WRF model can accurately simulate the meteorological conditions of the study area and provide a reliable meteorological field for CMAQ simulation.CMAQ simulation results show that the correlation coefficients between the simulated values of PM_2.5 and NOx and the monitored values were between 0.41 and 0.49,MFB was between-60%and 60%,and MFE was less than 75%,indicating that the simulation accuracy of the model met the requirements.The simulated value of the model was generally lower than the measured value,which is related to the incomplete source category of the MEIC.In terms of the impact of agricultural sources on air quality in Jilin Province,this paper designed simulation scenarios to quantitatively evaluate the effects of agricultural sources on air quality in Jilin Province.In improving the agricultural source scenario,the agricultural inventory of Jilin Province compiled in this paper was combined with the MEIC,and the air quality of Jilin Province was simulated more accurately by adding the missing source categories.And it was compared with the simulated concentration of the agricultural source reduction scenario.By comparing the spatial distribution of pollutant concentration,it is found that under the scenario of agricultural source zeroing,the concentration of PM_2.5 and CO in Jilin Province in the whole region decreased significantly.The PM_2.5 concentration contribution of agricultural sources in Jilin Province in April and October was 6.02μg/m³ and 4.33μg/m³,respectively,accounting for 21%and 20%of the total PM_2.5 concentration.In April and October,agricultural sources contributed more than 20 percent to the average concentration of PM_2.5 in Jilin Province,which had a significant impact on air quality in Jilin Province.