The Study Of NO_x And SO₂ Emission Flux Remote Sensing Method And The Error For Point And Area Sources

Study on source emissions is of great importance in atmosphere science research.NOx and SO2 are important inorganic pollutants in the atmosphere.Quantitative study on their emissions is thus significant for air pollution control,atmospheric environmen-tal chemistry and other researches.Therefore,developing remote sensing methods for NOx and SO2 emissions from point and area sources has important scientific meaning.A variety of factors affect the measurements of NOx and SO2 emission flux from point sources based on mobile platform remote sensing technology.The lack of comprehen-sive study on the influences of these factors on the mobile platform remote sensing leads to the difficulty in improving the measurement accuracy,which makes the meas-uring considitions rather difficult to determine.Compared with point source,new chal-lenges to area NOx emission measurements also appear due to the quick changes of area sources in China.The technologies for area source measurements are also rare.With mobile DOAS,the measurement methods and the errors were studied with generality and particularity on NOx and SO2 emission flux from point and area sources.For the emission flux remote sensing model and the error evaluation,the NOx and SO2 emission flux measurement method based on mobile DOAS was studied.The flux measurement model was established.And in the model,the wind field and the displace-ment vector were separated in the model.The model for NOx and SO2 emission flux measurement based on mobile DOAS was optimized.The NOx and SO2 flux error eval-uation method was also studied.The flux error evaluation method according to error source properties(random or systematic)and their influences was also developed.The model study laid a foundation for the further study of the method for NOx and SO2 flux measurement.For the study of NOx and SO2 point source emission flux measurement affected by many factors,the influence from atmospheric radiation transfer on point source slant column density measurement correction was studied and a simulation model for point source emission flux measurements of mobile DOAS was established based on Gauss-ian plume dispersion model and NOx photochemical model.Influences from the wind field uncertainty,Air Mass Factor(AMF),detection limit,sampling resolution,and other factors were analyzed.From the data analysis,when close to the source,it was found that the main error sources of NOx and SO2 are NO.ratio correction error with R2?1 and wind speed uncertainties with R2>0.4,respectively.The errors in close meas-uring distance also significantly affected by the error combination effect.When at a long measuring distance,undetectable flux is the main error source since long distance causes more dispersion,which even leads to unmeasure.According to the recom-mended observation conditions,the simulted results was verified by an experiment.With these analysis,the measuring conditions for point source NOx and SO2 emission fluxes based mobile DOAS were determined.For mobile DOAS NOx and SO2 measurements of area sources,the key parameters acquisition and statistical method were studied.The NO2 and SO2 vertical column den-sity(VCD)retrieval method for area sources was studied.According to the wind field characteristics,an average wind field and its uncertainty statistical method for urban area NOx emissions was established.Portable UV DOAS to obtain the NOx ratio along the roads was also put forward.For urban area source(Beijing,Wuhan)and industrial park area source(Rizhao),experiments were performed.The experiment results show that the main error source of urban area source was the wind field uncertainties with R2>0.8(including the wind speed and the wind direction uncertainties),and further in-dicates the necessity of real-time wind field.Compared with coarse wind,the usage of real-time wind field reduced the area NOx emission flux measuring error by 7%?50%.The NOx ratio study shows that the real-time NOx ratio could be effectively reduced the influence of NOx ratio error with R2<0.1 when there is no centralized emission source on the ground.The main error source of the industrial park emission measurements was wind speed uncertainty.This study provides a theoretical basis for the remote sensing method of NOx and SO2 emission flux,and also provides guidance for the accurate measurement of point and area source emissions.The studied NOx and SO2 emission flux measurement method provides useful mean for the atmosphere research and pollution control in China.