| Based on the daily remote sensing data of formaldehyde from OMI satellite sensor,the NDVI data from MODIS satellite sensor,the meteorological data and the socio-economic data of Shandong Province,the temporal and spatial characteristics of the formaldehyde vertical columns and their affecting factors in the troposphere over the Shandong Province during the years of 2009-2016 were analyzed with the methods of remote sensing image processing technology,Kriging interpolation and grey relational model.The result showed as follows:(1)An increasing trend of tropospheric formaldehyde column concentration in Shandong Province from 2009 to 2016 was shown and their average annual growth rate was0.97%.The maximum annual growth rate was 9.99% which appeared from 2009 to 2016.During the period of 2009 to 2016,the column concentration of formaldehyde was fluctuating.The minimum and maximum column concentrations occured in 2013 and 2009,respectively.The seasonal column concentration level of formaldehyde over Shandong Province showed that the summer’s level(17.22 × 1015 molec·cm-2)> autumn’s level(14.21 × 1015 molec·cm-2)> spring’s level(13.55 × 1015 molec·cm-2)> winter’s level(13.54 × 1015molec·cm-2).In the past 8 years,formaldehyde column concentration values have generally increased In all seasons,except for the decreasing trend in autumn.The minimum and maximum values of formaldehyde column concentrations in Shandong Province in the 96 months from January 2009 to December 2016,appeared in December2014(9.99 × 1015 molec·cm-2)and June 2010(19.92×1015 molec·cm-2),respectively.(2)Most of the first-level and second-level regions of tropospheric formaldehyde column concentrations in Shandong Province were located in the Jiaodong Peninsula,including Weihai,Yantai,and Qingdao while the areas of level 4 and level 5 were mainly located in the central and western regions in Shandong Province.The characteristics of seasonal spatial distribution and monthly spatial distribution were consistent with the spatial distribution rules,but the seasonal and monthly distributions had obvious seasonal variations.(3)The grey correlation model was used to explore the relationship between annual average formaldehyde values and local socioeconomic factors over the past 8 years in Shandong Province.The results showed that the three factors of coal consumption、population density and gasoline consumption had a significant correlation with the annual averageformaldehyde column concentration,and the correlation coefficients in order were 0.88,0.82 and 0.80.(4)The change of formaldehyde column concentration in Shandong Province was closely related to the change of NDVI vegetation index in the study area.The seasonal spatial distribution of NDVI in Shandong Province from 2009 to 2016 showed that the Western Shandong and Southern Shandong were higher than those in other regions of Shandong Province,which was basically consistent with the spatial distribution of formaldehyde.The average NDVI vegetation index of seventeen prefecture-level cities in Shandong Province was significantly positively correlated with the mean value of formaldehyde column concentration in the corresponding area in 2016,and the correlation coefficient was 0.554.In terms of time,NDVI also highlighted the obvious seasonal variation characteristics.Specifically,the average NDVI value The average NDVI value over Shandong Province showed that the summer’s level > autumn’s level > spring’s level > winter’s level,which was exactly the same as the seasonal variation of formaldehyde,according to 2009-2016 in Shandong Province.The relationship between NDVI index and HCHO column concentration in 32 seasons shows that the correlation between NDVI vegetation index and formaldehyde column concentration in the study area is as high as 0.708.(5)There was a big difference between the formaldehyde column concentration values and different meteorological factors in Shandong Province.The concentration of formaldehyde over this region was positively with the monthly mean ground surface temperature and monthly average radiation while negatively correlated with the average monthly surface air pressure.Humidity had different effects on formaldehyde column concentration in different regions of Shandong Province.The impact of wind on formaldehyde is as follows: in the coastal areas including Weihai、eastern and northern part of Yantai,the formaldehyde column concentration value was low,while in the inland areas where the wind speed was smaller,the formaldehyde column concentration value was higher.The temporal and spatial characteristics of the concentration of formaldehyde column over Shandong Province were affected generally by the combination of natural factors such as local vegetation、 meteorology and human factors such as social economy. |
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