Interaction Between Submerged Plants And Phthalate Esters

In this paper, toxicity, bioconcentration and biodegradation of dibutyl phthalate (DBP) and diethylhexyl phthalate (DEHP), listed as priority pollutants by the US EPA and China, in typical submerged plants in bioremediation, Hydrilla verticillata and Potamogeton crispus L. were investigated. Field monitoring of accumulation of DBP and DEHP in Potamogeton crispus L. in Haihe was also carried out.Experimental results showed that ethanol had obvious effects on Potamogeton crispus L. chlorophyll a compared with Hydrilla verticillata in the range of 0.25 mL/L to 4.0 mL/L, and Potamogeton crispus L. chlorophyll a decreased obviously. Ethanol with high concentration (2.0 mL/L and 4.0 mL/L) stimulated Potamogeton crispus L. chlorophyll a markedly. Potamogeton crispus L. can acclimatize itself to ethanol by changing the Peroxidase enzyme activity. The endurable capability of Potamogeton crispus L Peroxidase enzyme to ethanol was better than that of Hydrilla verticillata in the range of ethanol concentration studied. The endurable capability of Potamogeton crispus L. chlorophyll a was better than that of Hydrilla verticillata in the range of 0.4 to 13 mg/L for DBP, and 0.2 to 0.4 mg/L for DEHP, respectively. Dissolvable albumen of Hydrilla verticillata and Potamogeton crispus L. was composed under the stimulation of DBP and DEHP. The endurable capability of Potamogeton crispus L. Peroxidase enzyme to DBP and DEHP was much better than that of Hydrilla verticillata.Plants have an ability to accumulate and degrade DBP and DEHP. The experimental results indicated that the biodegradation of DBP and DEHP in plants and water could be described by a first-order kinetic equation. The accumulation and degradation processes of Hydrilla verticillata and Potamogeton crispus L. included three stages, which were surface adsorption, transfer in plants and degradation. It took 24 hours for the surface adsorption of Hydrilla verticillata, which was four times longer than that of Potamogeton crispus L.. By transferring into the plants, concentrations and bioaccumulation factors of DBP and DEHP in plants reached the maxima of 11.97 mg/kg and 55.84 mg/kg in Hydrilla verticillata, and 9.74 mg/kg and 7.80 mg/kg in Potamogeton crispus L, respectively. This stage was slow. Results from the experiment of accumulation of DBP and DEHP in different organs of plants showed that the bioaccumulation factors of DBP and DEHP in leaves were higher than those in stalks. The bioaccumulation factors of DBP were lower than that of DEHP in leaves and stalks of Hydrilla verticillata, however, the opposite phenomenon appeared in Potamogeton crispus L.. The results of the degradation of DBP and DEHP in the submerged plants showed that Hydrilla verticillata and its table companion microbe can degrade DBP and DEHP more efficiently. The degradation rates of DBP and DEHP were 2.19×10-2 h-1 and 1.09×10-2 h-1 by Hydrilla verticillata and its table companion microbe, 0.78×10-2 h-1and 0.17×10-2 h-1 by Potamogeton crispus L. and its table companion microbe, respectively.Results of field sampling at Sanchakou of Haihe showed that DBP and DEHP were detected in water and Potamogeton crispus L.. Concentrations of DBP and DEHP in water and Potamogeton crispus L. were the highest in the flourishing time of Potamogeton crispus L.. In Potamogeton crispus L., the bioaccumulation factors of DBP and DEHP in the leaves and stalks increased to the maxima in the period of withering and the bioaccumulation factors of DBP and DEHP were higher in leaves than those in stalks and individual plants.