| Urban ozone（O3）formation can be limited by NOx、VOCs,or both,the relationship of O3-NOx-VOCs were studied,which conbrituting to the design of effective O3 abatement plans.In order to study the temporal characterization of VOCs,NOx and O3,based on the ground-level pollutant（O3,PM2.5,NO2,PM10,SO2 and CO）data,volatile organic compounds（VOCs）,and meteorological（temperature,humidity,wind speed,precipitation and sunshine duration）data in Shijiazhuang City,the temporal dynamic and correlation analysis were adopted.In order to study the spatio-temporal evolution patterns and spatial factors affecting of VOCs,NOx and O3 in city-regions,based on the surface pollutant concentration data from 46 state-controlled and provincial-controlled environmental monitoring stations in Shijiazhuang City,three different functional regions were selected to conduct VOCs sampling data in Shijiazhuang city,the inverse distance weighted（IDW）interpolation and moran model has been applied to analyze the temporal spatial evolution pattern in Shijiazhuang.In order to study the contribution rate and direction of pollution sources in Shijiazhuang City,the sources of VOCs were analyzed by positive matrix factorization（PMF）.As well as the spatial autocorrelation and backward trajectories analysis were performed to explore the spatial agglomeration characteristics and potential source areas distribution of O3 pollutant in Shijiazhuang by combining with global data assimilation system（GDAS）meteorological.The research results were as follows.The results indicate that the monthly variations from 2014 to 2017 show a unimodal type trend.The typical period of O3 pollution(O3≥160μg·m-3)was from May to September.The monthly variations from May to September show a unimodal type trend with a peak in June,and the diurnal variations show a unimodal trend with a peak of 15:00～16:00 in TPOP of 2019.During the sampling period,the average concentration of ambient total VOCs（TVOCs）was（137.23±64.62）μg·m-3.Haloalkane were the most predominant VOC compound,accounting 31.77%of total VOCs mass,followed by aromatic（30.97%）and oxygenated VOCs（OVOCs,23.76%）.The O3 concentration correlated negatively with the VOCs and NO2,and positively with the temperature,sunshine duration,wind speed,and visibility.Furthermore,from 2014 to 2017,the variations of O3 concentration showed a clear upward trend during the pasted 4 years in city-regions of Shijiazhuang.The O3concentration increased since 2015 in main urban area of Shijiazhuang,and the control zone was changed from NO2 to VOCs.The seasonal variation of concentration of VOCs followed the trend of winter>autumn>spring>summer,the concentration of VOCs shows a trend of increasing gradient from west to east.Furthermore,from May to September,the ozone concentration range is 207 to 260μg·m-3,presenting a spatial pattern of high in the midwest and low in the peripheral areas.During the changes from 6:00 to12:00 and 12:00 to 15:00,the ozone concentration shows a trend of increasing gradient from southeast to northwest.In other words,the spatial factors affecting of O3 were mainly concentrated in the four dimensions of industry,agriculture,economy and population in city-regions of Shijiazhuang.Moreover,finally six potential sources to VOCs were quantified by PMF model,including emissions of gasoline（24.78%）,emissions of diesel vehicles（24.69%）,solvent usage（18.64%）,chemical industry（11.87%）,regional background（10.84%）,and pharmaceutical industry（9.17%）.At last,the potential source of ozone pollution is mainly concentrated in a space of 600 km,and the potential source areas with a larger weight concentration contribution is within the range of 200 km.Central and southern Hebei,central and northern Henan,western Shandong and central Shanxi are the concentrated areas of potential pollution sources,which have great impact on ozone pollution in Shijiazhuang. |
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