| In this study,we focused focused on the O3 concentration of Beijing,selected the O3 data in 2014-2019 released by Beijing environmental protection monitoring center and four urban forest ecological environmental monitoring stations by Beijing Forestry Fruit Science Research Institute,and combined with the meteorological data of China Weather Network and forest meteorological monitoring stations.At the same time,we used the handheld O3 monitor to obtain O3 concentration data of different kinds of tree species arrangement models.In other words,based on real-time monitoring of the ecological stations and manual experiment,combined with meteorological data,determine the background value and distribution characteristics of O3 concentration in different areas of Beijing,as a reference to explore the characteristics of O3 concentration changes inside and outside the urban forest,to clarify the influencing factors on O3 concentration,to select the tree species with the change concentration of O3 for urban greening in Beijing.The main conclusions of this study were as follows:?1?The O3 concentration in 2014-2019 in Beijing basically increased year by year: 2019?60.71±8.06?g/m3?> 2018?59.93±9.12 ?g/m3?> 2017?58.82±9.02 ?g/m3?> 2015?57.43±10.16?g/m3?> 2016?56.59±9.10?g/m3?> 2014?56.52±11.69 ?g/m3?.The spatial distribution characteristics of O3 concentration gradually decrease from north to South??=0.05,P<0.05?,northeast?68.27±8.43 ?g/m3?> northwest?63.88±6.66 ?g/m3?> southwest?58.01±7.55 ?g/m3?> southeast?57.16±3.84 ?g/m3?> center or six district?53.93±9.02 ?g/m3?,The seasonal variation of O3 concentration shows an inverted U-shaped trend,that is,the highest in summer,followed by spring and autumn,and the lowest in winter,with the peak in June and July.?2?The annual mean value of O3 concentration in Beijing is 15.55% higher in the vegetation area?70.40±1.27 ?g/m3?than in the non-vegetation area?59.54±2.25 ?g/m3?.However,the annual mean concentration of O3 in vegetation area?Badaling,northwest of Beijing??58.04±3.96 ?g/m3?is lower than that in non vegetation area?Yanqing town??65.35±3.33 ?g/m3?11.19%.Comparing the difference of O3 concentration in summer and winter,it is found that the vegetation area is larger than the non vegetation area.?3?The distribution characteristics of O3 concentration in urban forest of different pollution degree areas in Beijing are decreasing from suburb to urban area.Mountain forest area in suburb — Songshan Nature Reserve?86.36±36.17 mg/m3?,shallow mountain forest area in suburb — Xishan Forest Park?74.75±48.42 mg/m3?,wet forest area in suburb — Daxing Nanhaizi Park?60.16±25.52 mg/m3?,Central City — Chaoyang Park?57.47±39.47 mg/m3?.The mountainous forest area in the outer suburbs is 1.50 times of that in the central urban area.The annual concentration of O3 in urban forest is higher than that outside the forest 1.0719.09 ?g/m3?except chaoyang park and chaoyang agricultural exhibition hall?.Comparison results of O3 concentration in and out of the forest at each monitoring point were as follows,chaoyang agricultural exhibition hall?outside the forest??60.42±33.89 ?g/m3?> chaoyang park?inside the forest??57.47±39.47 ?g/m3?,West Mountain National Forest Park?inside the forest??74.75±48.42 ?g/m3?> Beijing Botanical Garden?outside the forest??65.68±30.63 ?g/m3?,Nanhaizi Park?inside the forest??60.16±25.52 ?g/m3?> Yizhuang Development Zone?outside the forest??59.09±29.91 ?g/m3?,Songshan Nature Reserve?inside the forest??86.36±36.17 ?g/m3?> Yanqing town?outside the forest??67.27±28.04 ?g/m3?.The inside of the forest is 1.021.28 times of the outside.?4?The variation of O3 concentration is affected by wind speed,temperature and humidity.O3 concentration was positively correlated with wind speed?inside:P=0.000,r=0.673;outside:P=0.000,r=0.735?and temperature?inside:P=0.000,r=0.810;outside:P=0.000,r=0.791?,negatively correlated with relative humidity?inside:P=0.000,r=-0.740;outside:P=0.008,r=-0.502?,and the significant degree was in forest > out of forest.?5?O3 concentration is related to PM2.5,NOX and NAI concentration.The concentration of O3 is negatively correlated with PM2.5?P=0.000,r=-0.431?and NOx?P=0.000,r=-0.564?,and positively correlated with NAIC?P=0.000,r=0.154?.?6?From March to October,the daily variation trend of O3 concentration of 26 different plant allocation mode in the Daxing Nanhaizi Park of Beijing showed a "single peak" trend,it usually peaks at 14:00 and 16:00.Monthly trend: September > August > July > June > may > April > March > October.Pure coniferous forest is the optimal allocation mode of urban forest,the order of O3 concentration is: pure coniferous forest < mixed coniferous forest < mixed coniferous and broad-leaved forest < multiple layer forest?coniferous broad-leaved irrigation?< pure broad-leaved forest < mixed broad-leaved forest < multiple layer forest?broad irrigation?.The concentration range of O3 in different planting combinations is between?149.02±35.80??g/m3 and?203.14±43.36??g/m3,multiple layer forest?broad irrigation?is 1.36 times higher than pure coniferous forest. |
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