| Fine particulates in the air is one of the major pollutants of air pollution in our country,which is also an important factor affecting the haze phenomenon in most of the more developed regions in our country.Fine particles of the atmosphere are mainly produced by human activities in production and life,including surface dust,industrial production,direct emissions of automobile exhaust,etc.Fine particulates that accumulates over the city,due to its small mass and strong adsorption properties,can stay in the subsoil for a long time,then interact and transform.Fine particulates suspended in the atmosphere adsorbs toxic and harmful substances in the environment and poses a serious threat to the human health of the surrounding people.It will increase the incidence of respiratory diseases among local residents.At the same time,it can affect human activities such as local agricultural production and transportation indirectly by influencing local climatic conditions.In recent years,with the rapid economic development in of our country,the phenomenon of atmospheric particulate matter pollution is worsening day by day.The current situation of atmospheric particulate matter pollution in the eastern region with relatively fast economic development and dense population in our country is especially severe.PM2.5.5 pollution has become a hot issue both at home and abroad.Hebei Province is located in the eastern of Taihang Mountains,southern of Yanshan Mountains.Affected by its special geographical location and climatic characteristics,the perturbation effect of the relevant air flow on the inland plain is greatly weakened,making it difficult for the air pollutants produced from the ground to effectively migrate outwards and dissipating,resulting in the local being the hardest hit by PM2.5.5 pollution.In order to get a deeper understanding of the complicated relationship between ground pollution sources,meteorological conditions and atmospheric particulate matter concentration in Hebei Province and to reveal the spatio-temporal distribution of PM2.5.5 in the study area,this paper take Hebei Province as the research area,based on the quantitative study of mixed-effects model,establishing the relationship model between aerosol optical thickness?AOD?,meteorological factors,land use factors and spatio-temporal distribution variations of PM2.5.5 concentration in the near-surface layer.And then get the simulation result of spatio-temporal distribution of PM2.5.5 concentrations with high temporal resolution?daily?and spatial resolution of 10×10km,realizing the quantitatively identify between the contribution of regional influencing factors and the spatio-temporal distribution of atmospheric particulate matter concentration,and then to provide pollution control of atmospheric particulate matter Scientific support,which will provide scientific support to the pollution control of atmospheric particles.In this study,the ten-fold cross-validation method was used to test the accuracy of the mixed-effects model.We retained the effective influence factor of PM2.5.5 in the model and removed the prediction model with over-fitting phenomenon.The correction factor calculated by monitoring ground PM2.5.5 concentration data was used to correct the sampling deviations due to non-random AOD deficiencies.It will further improve the prediction accuracy of the mixed-effects model and obtain the spatio-temporal distribution of PM2.5.5 concentration in the near-surface layer of the study area.The results showed that the prediction accuracy R2 of the mixed-effects model in Hebei Province reached 0.85.After cross-validation,the R2 was 0.77,RMSE and RPE were18.28?g/m3 and 28.68%.It improved the simulation effect of PM2.5.5 concentration in the area greatly.In addition,the annual correction factor of Hebei province calculated by the PM2.5.5 monitoring data ranged from 1.24 to 2.05,indicating that the PM2.5.5 data in the modeling dataset is difficult to represent for the atmospheric quality in the high pollution period.After correcting the model simulation results by the regional correction factors,the average PM2.5.5 concentration in the study area was 89.84?g/m3,which was close to the actual monitoring data.It can solve the annual average under-estimation caused by the sample sampling deviation effectively.The above results show that the mixed-effects model can simulate the spatio-temporal variations of PM2.5.5 effectively.Proper combination of forecasting factors and model correction factor not only help to improve the prediction accuracy of the model,but also make up for the lack of spatial and temporal data of ground monitoring stations effectively.This will provide scientific reference for our country's environmental governance and planning. |
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