Studies On The Uptake And Phytoremediation Of Pesticides By Plants

The uptake and phytoremediation of some pesticides by some higher plants were investigated.Research results of dimethoate and dicofol uptake by rice (Oryza sativa L.), canna (Canna L. indica), tnro(Colocasia esculenta Schott),and alligator (Alternanthera philoxeroides Griseb) in soil, by water hyacinth (Eichhornia crassipes Solms)in water showed that both systemic and non-systemic pesticides could be absorbed by plant roots and transplaced to the other plant tissues. The uptake amount increased with the increasing of pesticide concentrations in the culture media. However, the amount absorbed and transplaced differed among pesticides and plants. The order of uptake amount of a same pesticide by plants was water hyacinth > rice > canna > taro > alligator > willow > tea plant, and the uptake of dimethoate was greater than that of dicofol. The rates of dimethoate concentration in plant leaves to roots for rice, taro, and canna were 16.29,2.33, and 0.77, and those of dicofol were 0.72.0.14, and 0.06 respectively. The growth of rice, taro, and alligator was significantly inhibited while they were planted in soils added with 50 nig/Kg of dicofol. the biomasses were 30.72%. 37.19%, and 25.05% as those grown in soils without dicofol, though all the test plants grown well in soils with 5 ing/kg of dicofol and 50 mg/kg of dimethoate. Canna could tolerate 50 nig/kg of dicofol and dimethoate. There were no visible morphologicalchange in water hyacinth exposed to a mixture of ethion, dicofol, fenvalerate, fenpropathrin, deltamethrin, and cyhalothrin with the concentrations of 0.01 mg/L, 0.1 mg/L, and 1 mg/L, but the fresh biomasses were increased by 49.79%, 40.34%, and 83.88% respectively compared to those planted in water solutions without pesticides.The removal dynamics of pesticides by plants was corresponded with the first order kinetic reaction. The half lives of dimethoate, malathion, and methyl parathion with a concentration of 10 mg/L, ethion, dicofol, and cyhalothrin with a concentration of 1 mg/L in 250 ml planted with 10-11 g water hyacinth were 236 hrs, 77 hrs, 25 hrs, 65 hrs, 62hrs, and 80 hrs, and those in unplanted water solutions were 338 hrs, 274 hrs, 226 hrs, 236 hrs, 114 hrs, and 365 hrs respectively. Therefore, the dissipation rates of those pesticides were increased by 43.41%, 255.73%, 804.91%, 260.20%, 80.06%, and 357.37% respectively by water hyacinth compared to the unplanted control. Plant uptake, accumulation, and phytodegradation might be the main phytoremediation process, and the role of microorganism degradation was relatively smaller except that of dimethoate.The dissipation rate constants of malathion and methyl parathion with a concentration of 3 mg/L, and ethion, dicofol, and cyhalothrin with a concentration of 0.5 mg/L in 2000 ml of 55-60 g canna planted water sulution were respectively increased by 77.66%, 117.44%, 64.80%, 38.11%, and 15.35% compared to those in unplanted water solutions. More than 70% of the amount of ethion, dicofol, and cyhalothrin uptaken by canna maintened at roots, and this ratio increased with the decreasing of water solubility of the pesticide.The concentrations of ethion, dicofol, and cyhalothrin in plantedwillow cutting soils were decreased to 1.65 mg/kg, 0.07 rag/kg, and 0.23% nig/kg respectively from 5 mg/kg in 8 weeks of treatment in field condition, which were 80.88%, 3.93%, and 39.66% as those in unplanted soils. The majority of the pesticides uptaken by willow was at the roots, amount in barks followed secondly highist, and almost no pesticide residues were found in the naked stem.The phytoremediation efficiency of a pesticide by plants might be water hyacinth > canna > willow > tea plant.