The Gas-Particle Partitioning Study Of Persistent Organic Compounds

Partitioning of organic compounds between the gas and particulate phases has an decisive role on the sedimentation that influences the reaction activity, atmospheric fate,persistance,transport and transformation of these compounds.The adsorption and accumulation of organic compounds on the particles is one of basic approaches composing exposition risk for human.It is important to study the distribution of organic compounds between the gas and particulate phases and provide basic data and methods in order to estimate the atmospheric fate of organic compounds accurately.In this reaserch,the comparison of soxhlet and ultrasonic extraction was made.The extraction efficiency indicated the soxhlet was better.The fectors influenting extraction efficiency including circulation times,back-flow velocity and slection of solvent and its use level were also investigated. Experimental and quantitative analysis conditions were as follows:soxhlet 6h using 120ml acetone/methylene dichloride with the back-flow velocity 3～4 times/h.HPLC analysis conditions:methanol 0.85ml/min,water 0.15ml/min, flow rate:1ml/min,column temperature:30℃,UV detective wavelength:254 nm,chromatographic column:Shimadzu Shim-pack VP-ODS 4.6×150mm, 5μm.Using pint-sized aerosol-chamber and simulation atmospheric particulate to simulate the gas/particle partitioning process of the first seven PAHs among the 16 PAHs proposed by EPA(acenapthylene,acenapthene,fluorene, phenanthrene,anthracene,fluoranthene and pyrene).The adsoption isotherm of the PAHs at different conditions were plotted and fitted by Langmuir and Freundlich models to determine the gas/particle partition coefficient Kp. Study on the relationship among the Kp and Kow,Kw,p_L~0.The results indicated that the partition process accorded with the Langmuir model and experimentally determined logKp values correlated well with the logKow,logKw,log p_L~0 of PAHs as follows: logKp=-0.2415logKw-0.1821,logKp=0.5345logKow-1.3291,logKp=-0.53log p_L~0-0.5264.The positive correlations were found among Kp and qm,K_L.So it is viable to forecast Kp values through the physicochemical propertyies of PAHs.The particles characteristics,the physicochemical properties of PAHs and the environmental conditions are the major factors impacting the distribution between gas and particle phase of organic compounds.