Pollution Characteristics,sources,health Risk And Emission-reduction Measures Of Atmospheric Pahs In Ningdong Energy And Chemical Industry Base

Polycyclic aromatic hydrocarbons?PAHs?consisting of more than two fused aromatic rings,which are recognized as carcinogenic,teratogenic,and genotoxic and are prevalent in environment.Large amounts of PAHs are emitted by unintentional emissions from human activities:in particular,incomplete combustion of fossil fuels is the main source of PAHs in the atmospheric environment.Ningdong Energy Chemical Base is a state-level key development zone approved by the State Council,and also is a state-level large-scale coal production base as well as a coal chemical industry base.The heavy emission from industrial activities must cause serious inhalation exposure risks to local residents.The thesis would like to investigate the atmospheric pollution levels,characteristics,sourcesof PAHs in PM_2.5,PM_1.0,and gas phase and their emissions influence on the air quality of the downwind region of Ningdong Energy and Chemical Industry Base.In addition,the health risk would be evaluated based on these observed data,assessmentand then the measures for reducing emissions and the selection of reasonable PAHs control technologies weresuggested.The conclusions of this thesis are as follows:?1?Atmospheric PAHs pollution characteristics of Ningdong Energy and Chemical Industry Base:?₁₆PAHs concentrations in PM_2.5,PM_1.0,and gas phase were at the range of 17.95 to 325.12 ng/m³,12.66 to 311.96 ng/m³ and 26.33 to 97.88 ng/m³,respectively.The average annual concentrations were 99.42 ng/m³,78.88 ng/m³,and 57.89 ng/m³,respectively.The concentration of PAHs in atmospheric PM_2.5 of Ningdong Energy and Chemical Base was 5-10 times higher than that of European and American countries,about 3 times higher than most domestic cities and wasequivalent to that of Taiyuan City,Shanxi province in which the atmospheric PAHs pollution is serious.Duringthe heating season,the PAH congeners in fine particle were mainly 4-5 rings,but during non-heating season the PAH components were dominated by the 5-6 rings;the atmospheric PAHs in gas phase were mainly dominated by 3 rings congeners for both the heating season and the non-heating season,and the generally PAHs concentration was higher at night.than that at daytime.?2?The inhalation exposure health risks of atmospheric PAHs for local people:the health risks caused by inhalation exposure to atmospheric?gas phase+particulate phase?PAHs in the study area is 6.41×10^-3,which were much higher than those limit values recommended by the US Environmental Protection Agency(exposure risk should be under 10^-6)with the 2 to 3 orders of magnitude higher.It can be inferred that atmospheric PAHs emissions from Ningdong Energy and Chemical Base must have a significant health effect to local residents.?3?The sources of atmospheric PAHs emission in Ningdong Energy and Chemical Industry Base:The sources of PAHs were mainly from biomass and coal combustion,followed by the contribution of transportation sources.The result of backward trajectory?possibly input source?by HYSPLIT model simulation indicated that Urumqi may have a certain contribution and influence on air PAHs levels in the Ningdong Energy and Chemical Base in both the non-heating period and the heating period,while the Xi'an City only contributed in the non-heating period.For the non-heating period,the forward trajectory influence?output characteristics?area included the eastern part of Shanxi Province,Taiyuan,the provincial capital of Shanxi Province,and Shijiazhuang,Inner Mongolia and Outer Mongolia;while during the heating period the PAHs emission covered the capital of Inner Mongolia,Hohhot,and the central province of Shanxi includes the provincial capitals Taiyuan,Shijiazhuang in HeBei province,northern Shandong,northern Shaanxi,and northern Henan including Zhengzhou,which indicated that atmospheric PAHs pollution in the Ningdong during the non-heating period wouldhave some impact on the atmospheric environment in these areas.These may be regional sources of potential PAHs in the atmosphere.?4?The thesis suggested that relevant control and emission reduction proposals for addressing the contribution of vehicle emissions to atmospheric PAHs and potential sources of PAHs in the downwind region,including:control of PAHs on raw coal;more effective control devices by adoption of PAHs;establishment of special regulations for prevention and control of motor vehicleemission;establishment of regions joint defense system;clarifying government responsibilities and increasing penalty policy;improving air pollutant emission standards for new coal chemical industry?coal gas,coal to oil?;and formulatinga long-term plan for reasonable pollution control.