Research On The Release And Bioavailability Of Phthalate Esters After Death Of Potamogeton Crispus L.

The project entitled "Study on effects of submerged plants on the environmental behaviors of endocrine disrupting chemicals"was supported by the National Natural Science Foundation.Dibutyl phthalate (DBP) and diethylhexyl phthalate (DEHP), two typical endocrine disruptors and micro-pollutants, were selected as the target compounds. Potamogeton crispus L. (P. crispus) is a typical submerged plant and was as the test plant. The release and bioavailability of PAEs, sequestered by P. crispus, after plant death and cellular disruption were studied by stimulating laboratory experiments. This study has great theoretical significance and reference value in the environmental field.Experimental results are as follows:Identification of the degrading bacterium: Strain H-1 was isolated from sediment of Haihe River, it was able to grow by utilizing DBP and DEHP as sole source of carbon and energy. By the study of morphological and physio-biochemical characters, strain H-1 was identified as Deinococcus.Results of kinetics of PAEs sorption showed that: Sorption equilibrium of DBP and DEHP on the P. crispus particles was reached quickly, 0.5 h for DBP and 2 h for DEHP; the solid-water partition coefficients of DBP and DEHP increased gradually during 24 hours, and reached the maxima of 1305 and 1284, which were really close. Results of kinetics of PAEs desorption showed that: the desorption equilibrium of DBP and DEHP was reached quickly, about 0.5 h for DBP and 1 h for DEHP. The results indicated that DEHP was more difficult to desorpt from P. crispus particles.Results of the effect of initial PAEs concentrations on biodegradation characteristics of strain H-1 showed that: DBP and DEHP can be degraded effectivly by Strain H-1, and the biodegradation can be expressed in the first-order kinetics. As the concentration of DBP and DEHP increased from 0.1 to 1.0 mg/L, no significant difference of the degradation kinetic constants was observed, when the concentration increased to 10 mg/L, the degradation kinetic constant decreased significantly. Results of release and bioavailability experiment showed that: PAEs sequestered by P. crispus were released and biodegraded after plant death and cellular disruption. Compared to the simple desorption process, the release of DBP and DEHP increased, and the time for the release equilibrium extended after incubation with strain H-1. Compared to DEHP, DBP is released more easily. The bioavailability of DBP and DEHP sequestered by P. crispus was less than that added directly to the solution, particularly DEHP. Compared to MBP, very less MEHP was formed so that there is less both in the aqueous phase and solid phase, MEHP is more easily adsorbed to the P. crispus particles. The degradation efficiency of MBP, MEHP may be lower than that of DBP, DEHP respectively, ie, the bioavailability of monoester of strain H-1 may be lower.