THE PARTITIONING MODEL OF POLYCYCLIC AROMATIC HYDROCARBON BETWEEN GASEOUS AND PARTICULATE (PM10-MU) PHASES IN URBAN ATMOSPHERE WITH HIGH HUMIDITY

At present, temperature is usually the only environmental factor in the partitioning model of PAHs between gaseous and particulate phases in atmosphere. In this study, the effect of humidity on the partition of semi-volatile polycyclic aromatic hydrocarbons (PAHs), fluoranthene and pyrene, between gaseous phase and PM10mu particulate was first investigated, which has not yet been done before. It was shown that there was a relation between partition coefficient, K(p), i.e. F/[A (PM10)], and humidity (g/m3), which range from 8.2 to 25.8 g/m3 corresponding to 52-93% of relative humidity. A and F stand for PAH amount in gaseous and particulate phases, respectively. PM10mu stands for concentration of PM10mu in ng/m3. The partition coefficient increases with increasing humidity. However, the coefficient of humidity variable in the regression model indicated that the effect of the humidity on the partition coefficient is low. Furthermore, the partitioning model incorporated humidity was set up in the form of log (K(p)) = b0 + b1(1/T) + b2H + b3(1/T)H and was evaluated by stepwise regression in the humid atmosphere at Taipei. T is ambient temperature and H is humidity in g/m3, b0, b1 and b3 are coefficients of the multiple regression between log (K(p)) and 1/T, H and (1/T)H. The results indicated that the model with the inverse of temperature is sufficient and in the form of log (K(p)) = b0 + b1(1/T) The coefficient of correlation is 0.86 and 0.89 for fluoranthene and pyrene, respectively. The sampling experiments of gaseous and particulate PAHs were conducted using PUF plugs and PM10mu sampler in the downtown area of Taipei city from June 1988 to May 1990. The samples were analyzed by GC/MS for the PAH substances.