| VOCs are the general name for a series of hydrocarbons.VOCs could be emitted from anthropogenic VOCs and biogenic VOCs.Biogenic VOCs emissions from vegetation were estimated to account for more than 90%of total VOCs emissions globally.Researches have shown that biogenic VOCs could lead to significant photochemical ozone formation,with its abundances and high chemical reactivity.Biogenic VOCs play an important role in the formation of tropospheric ozone.In the present work,biogenic emissions over the Yangtze River Delta?YRD?region for year 2014 were developed based on the interpretation of remote sensing image and MODIS data using the Model of MEGAN.Impact of biogenic VOCs emissions over the YRD region on ozone formation was investigated based on WRF–CMAQ modeling system for July 2014.To investigate the impact of biogenic emissions on ozone formation in the YRD region,two parallel CMAQ simulations were conducted with identical model configurations except the emissions:Scenario 1(Sa+b)included both anthropogenic and biogenic VOCs emissions while Scenario 2?Sa?only included anthropogenic emissions for the YRD region.Driving inputs for MEGAN include the leaf area index?LAI?,plant functional types?PFT?,emission factor,meteorology.The results show that annual biogenic VOCs emissions in the YRD estimated by MEGAN were 18.86×105ton yr-1 for year2014,of which isoprene?ISOP?,monoterpenes?MON?,and other VOCs account for7.04×105?37.33%?,3.03×105?16.07%?,and 8.79×105ton yr-1?46.60%?,respectively.Anthropogenic VOCs emissions in the YRD region were estimated to be40.3×105 ton yr-1.BVOCs emissions showed significant seasonal variations with highest emissions in summer?July,August,September??60.9%?and lowest in winter?January,February,December??3.2%?.In addition to the seasonal changes,biogenic VOCs emissions also exhibited diurnal variations.Biogenic VOCs emissions reach its peak value near local noon time due to high temperature and strong solar radiation.For isoprene,there are zero emissions during night time because isoprene emissions are light-dependent.In contrast,monoterpenes and other VOCs are being consistently emitted because they are not light-dependent.The southern of YRD emits more biogenic VOCs than the northern part.Annual emissions from Zhejiang?ZJ?,Anhui?AH?,Jiangsu?JS?provinces,and Shanghai?SH?were estimated to be 8.42×105?44.6%?,7.60×105?40.3%?,2.72×105?14.4%?,and0.12×105ton yr-1?0.7%?,respectively.The results show that the spatial distribution of biogenic and anthropogenic VOCs emissions over the YRD region.Anthropogenic VOCs emissions were higher in Shanghai,Jiangsu and the eastern coastal areas of China,where there are more developed districts with high industrial activities and population.Biogenic VOCs emissions were higher in the southern YRD part?such as Zhejiang and the southern Anhui?than the northern part.The effects of biogenic VOCs on ozone concentrations were examined by comparing the results from the two scenarios.Findings from this work will provide important scientific support for the mitigation of ozone pollution in the YRD region.The impact of biogenic VOCs on ozone is mainly concentrated in the middle part of the YRD region,which is the downwind of the region in summer period.The daily average ozone values was calculated at national control points of Putuo,Caochangmen,Shanxi Road,Chengxiang town and Mingzhu square in YRD.The monthly average,maximum 8-h average and maximum 1-h ozone concentrations at 5urban sites contributed by biogenic VOCs emissions are 11±6.96%,12±7.76%,and6.6±6.96%,respectively in July 2014.The monthly average,maximum 8-h average and maximum 1-h ozone concentrations are over 15.12,33.56 and 55.35?g/m3 in YRD region,suggesting significant impact of biogenic VOCs emissions on ozone formation in the YRD region.Impact of biogenic emissions on ozone formation exhibited a strong spatial pattern:high contributions were observed in the middle YRD region,including Bengbu,Tongling,Hefei,Huzhou,Nanjing and Zhenjiang,with the maximum hourly ozone contribution of 23.2243.04?g/m3 for July.The influence of biogenic VOCs on ozone formation in rural area is higher than urban area.The research is more reliability than traditional methods.The results can provide some scientific basis for some problems about air pollution and ozone pollution.The uncertainty of data acquisition and the uncertainty of the model itself will be the research direction of future work. |
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