TP7 Fugacity Models: New and Different Uses
Room 18C/D, Level 4
2:10 PM - 5:30 PM, Tuesday, 11 November 2003
Chair: Diamond, Miriam ,
(305) Changes Of 
HCH Concentrations In Various Media In Tianjin, China From 1953 To 1992.
Tao, S1, Cao, H1, 1 Peking University
ABSTRACT- A level IV fugacity model was performed to describe the changes of hexachlorocyclohexane (HCH) concentrations in bulk compartments in Tianjin, China during a period of four decades starting from 1953 when full scale industrial production and extensive agricultural application of the insecticide began in the area. The HCH concentrations in air, water, soil, and sediment reached 95% of the steady-state levels after 2, 2, 7, and 6 years of continuous loading, respectively. The model was validated by comparison between the estimated and the independently observed steady-state concentrations in water, soil, and sediment and a fairly good agreement between them was found. The absolute differences between the modeled and observed HCH concentrations in various media are from 0.15 to 0.61 log-units. The dominant input and output pathways of HCH were agricultural application, wastewater discharge and degradation in soil and sediment. As the dominant sink, soil accumulated more than 80% of HCH in the area at the steady-state. All input parameters except gas constant were subject to a sensitivity analysis. 17 key parameters were identified based on the results of the sensitivity analysis and perturbation of the parameters themselves. The steady-state estimates were very sensitive to application rate, wastewater discharge rate, degradation rates in soil and sediment, sedimentation rate, and thickness of soil and sediment, while the unsteady-state estimates were especially sensitive to the degradation rates in soil and sediment. The uncertainty of the model was tested by repeatedly running the model for 3000 times with randomly selected values of all key parameters based on log-normal distribution with given means and coefficient of variances. The results of the Monte Carlo simulation are discussed.
Key words: organochlorine pesticide, multimedia model, HCH, fugacity