| Volatile organic compounds（VOCs）play an important role in the atmospheric chemical reactions of the troposphere.As significant precurcors of ozone and secondary organic aerosols（SOA）,VOCshavedirect and indirent influences on regional atmospheric environmental quality and global atmospheric radiation balance.With the rapid economic development in recent years,Beijing and its surrounding areasare suffering from air quality problems caused by the photochemical pollution and haze event.Understanding of the concentration characteristics,influencing factors and atmospheric reactive activities of VOCs in Beijing and its surrounding areas is very important to controlthe air pollution.In this study,we measured ambient VOCs from June 2013 to December 2015 at four sites in Beijing and its surrounding areas,including Beijing Urban Station,the background station of North China-Shangdianzi Station,Gucheng Rural Station and Raoyang Rural Station in Hebei province.The spatial distributions and temporal variations of VOCs concentrations and composition were studied,the contributions of VOCs to yield ozone and secondary organic aerosols were caculated,the influence of meteorological factors on VOCs concentration was discussed,and the reduction rate of VOCs was estimatedin Beijing station during the period of emission control in September of 2015.The main results of this work were listed as follows:1.From June 2013 to December 2015 theaverage concentration of total VOCs in Beijing urban stations was（16.38 ± 10.18）× 10-9and the range varied from 0.08 × 10-9 to 60.72 × 10-9;in Shangdianzi stationthe average concentration of VOCs was（12.25 ± 10.05）× 10-9 with the rangebetween 0.09 × 10-9 and 55.83 × 10-9;from June 2013 to March 2014,the concentration ofVOCs in the Gucheng urban area varied from0.11 × 10-9 to 57.43 × 10-9,with an average concentration of（19.92 ± 19.68）× 10-9;the concentration of VOCs in the rural stations of Raoyang was at the range of 0.01 × 10-9 to 44.01 × 10-9,and the average concentration was（11.82 ± 7.03）× 10-9.At four sites,aromatic hydrocarbons were the dominant contributor to atmospheric VOCs concentrations.2.In Beijing urban stations the annualconcentration of VOCsdecreased from 2013 to2015.At four sites,the highest concentrations of VOCs were observed in summer.At the same observation time,the concentration of VOCsat Gucheng rural station was higher than the other three sites.3.The VOCs concentration in Beijing urban area is mainly affected by the southwest and northeast winds.In spring and winter the concentration of VOCs is mainly affected by southwest wind and in summer.In autumn are affected by southerly and northeast winds.Atmospheric VOCs of Shangdianzi station are obviously affected by the dominant wind direction in the northeast（summer and autumn）and southwest（winter）.In summer,the VOCs concentration of Gucheng was affected by N-NE,W-NW and W-SW winds.The VOCs in the rural station of Raoyang are greatly affected by the north wind in summer.4.In the Beijing Station,the emission of VOCs and PM2.5were reduced by 69% and 74%,respectively,by comparison the similar of the meteorological conditions to the 2015 emission reduction period.5.The total OH consumption rates(LOH)of Beijing,Shangdianzi,Raoyang and Gucheng stations were 641.54s-1 and 657.14s-1,515.77s-1 and 838.34s-1,respectively.The total ozone formation potential（OFP）of Beijing,Shangdianzi,Gucheng and Raoyang stations were 61.28×10-9,42.76×10-9,75.91×10-9 and 39.00×10-9,respectively.The maximum potential formation of secondary organic aerosols（SOA）was 184.97μg/m3 in Gucheng.The second-highest SOA was 138.31μg/m3 in Beijing,and then the third-highest SOA was 100.95μg/m3 in Shangdianzi.The lowest SOA was 85.78μg/m3 in Raoyang.Aromatics contributed the largest parts of LOH,OFPand SOA.Although alkanes were the most abundant components of VOCs in the atmosphere,it is not the main contributor of LOH,OFP and SOA.So,the control of the aromatics emission should be strengthened. |
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