Transport process of trichloroethylene and trichlorobenzene across the water-maize-air interface.

Corn seedlings were exposed separately to culture solutions of trichloroethylene(TCE)or 1,2,3-trichlorobenzene(TCB).Concen-trations of TCE and TCB in xylem saps,dewdrops,and final culture solutions were determined to evaluate the transport processes of the two organic compounds in water-corn-air systems.The results indicated that TCE and TCB in dewdrops originated mainly from their volatilization with water vapor from the seedling leaves.The TCB concentrations in xylem saps were positively related to the respective concentrations in the externa(lculture)solution.In contrast,the TCB concentrations in dewdrops were negatively related to those in the external solution.The transpiration stream concentration facto(rTSCF)was found to vary with the exposure time.The TCB concentrations were higher in dewdrops than in xylem saps when the seedlings were exposed to low TCB concentrations in the external solution;the reverse occurred when the seedlings were exposed to high TCB concentrations in the external solution.The TCE concentration in dewdrops increased with increasing TCE concentration in the external solution,and was generally much higher than that in the xylem sap;the TCE concentration in xylem saps decreased sharply with increasing TCE concentration in the external solution.