Characteristics And Health Risk Assessment Of Volatile Organic Pollutants In Zhengzhou During Heating Period

In recent years,Zhengzhou has suffered from severe haze pollution during the winter heating season,and SOA(secondary organic aerosol,SOA)has contributed significantly to the pollutant PM2.5.Therefore,in order to control the pollution problem in the heating season,it is urgent to control and control the VOCs(volatile organic compounds,VOCs)precursors of SOA.This paper is based on the online VOCs data of February 2018 and October 15-December 15,2018 to study the comparison of pollutants before and after heating,SOA,health risk assessment,source analysis,and to study the heavy pollution process and holiday effects during heating.First,analyze the difference in pollution before and after heating.The highest proportion of alkanes in the four different periods before and after heating is 42.94%,44.57%,40.92%,and 45.01%.The potentials of SOA generation in the non-polluting non-polluting period before heating and the non-polluting period after heating were 25.57,14.73,30.81 and 14.96×100ug/m3,respectively.The top six emission sources(motor vehicles,industry,combustion,biomass,LPG,solvents)contributed 29.06%,20.36%,11.44%,11.89%,14.18%,and 13.04% of VOCs emissions,respectively.After heating,the six emission sources contributed 17.50%,18.37%,25.90%,12.30%,16.63%,and 9.18% to VOCs emissions,respectively.The cumulative risk indexes of non-carcinogenic risks of VOCs in four different periods before and after heating were 3.31,2.67,5.78,and 3.25,respectively,with a certain degree of non-carcinogenic risk.The carcinogenic risks of benzene in four different periods are 7.20E-06,4.06E-06,1.09E-05,and 3.58E-06,all of which exceed the safety thresholds set by the US EPA(1.00E-06),indicating that The exposed population has a certain carcinogenic risk.Secondly,analyze the heavy pollution process during heating.Analysis of meteorological conditions and conventional pollutants found that meteorological conditions with low wind speed,low PBL,low radiation intensity and high humidity were the main reasons leading to reduced visibility and increased PM2.5 concentration.And the change of VOCs concentration is similar to that of PM2.5.The average VOCs concentration in the three pollution processes during the heating period were 91.51 ppbv,61.55 ppbv,and 82.55 ppbv,respectively.The analysis results indicate that the main cause of pollution incident 1 is local high emissions.Unfavorable meteorological conditions during pollution event 2 were the key factors causing pollution during this period.During the pollution process 3,the particulate matter pollution was the most serious and the VOCs were at a higher concentration level.And meteorological conditions are not conducive to the spread of pollutants.Therefore,high emissions and unfavorable meteorological conditions are the main causes.In the three pollution processes,alkanes accounted for 51.43%,59.38% and 53.44% of VOCs,including propane,ethane,n-butane,isobutane and isopentane.Therefore,the volatilization of natural gas and liquefied petroleum gas(LPG)may have an important impact on pollution.Before,during and after the Spring Festival holiday,the average concentration of total VOCs was 68,57 and 68 ppbv,respectively.Compared with nonChinese New Year holidays,the concentration of VOCs during Chinese New Year holidays is reduced by 20%.And during the fireworks events during the Spring Festival holiday,TVOC concentrations were higher,with maximum concentrations of 69 and 80 ppbv,respectively,indicating that fireworks and firecrackers released more VOCs.PM2.5 is also at a higher concentration level up to 295 ug/m3.The VOCs are traced through PMF.The five major sources of volatile organic compounds are:(1)solvent utilization(2)industrial emissions(3)automobile exhaust(4)LPG(5)coal + biomass combustion.