Accumulation And Degradation Of Ametryn-Contaminated Soil In Four Plants

Ametryn is a novel triazine herbicide which was modified by atrazine,and it belongs to the selective and uptake herbicides.Ametryn has been used in a large area to sweep pre and post emergence of broadleaf and grass weeds in farmlands planted mostly with maize,potato,sugar cane,bananas,citrus and pineapple,etc.However,owing to its stability structure,and long duration,it has made a bad effect on the soil,plants and human health.Therefore,the research of ametryn degradation in soil is significant.The experiment was performed to compare the capabilities which were to degrade and accumulate ametryn among four plants(wheat,ryegrass,alfalfa and maize).Wheat,ryegrass,alfalfa and maize were cultivated in the soil with 1 mg kg-1 ametryn for 10 d,there are difference among wheat,ryegrass,alfalfa and maize to degrade and accumulate ametryn.The aboveground of four plants accumulated ametryn more than the underground.Among the four plants,the maximum ametryn-accumulating plant was alfalfa and wheat,and there was no significant difference between them.The TF values of ryegrass was 5.122,much larger than the other three plants.The concentrations of ametryn in plants cultured soil were less than the control(wothout plants).After cultivated for 10 d,ametryn removal was 16.6%in the control,while the soil with plants removel ametryn was 26.4%-50%,indicating that the cultivation of wheat,ryegrass,alfalfa and maize enhanced the degradation of ametryn.The rhizosphere soil with plants which wiping off ametryn 41.1%-73.0%was residues the least ametryn.The reason might be related to the plant rhizosphere microbial communities and secretions.Ryegrass was cultivated in the soil with 1 mg kg-1 ametryn for 10 d,the activities of CAT,GST and LAC in ryegrass showed that significantly higher than the control.The activities of CAT and DHA in soil were not varied with 1 mg·kg-1 ametryn,but enhance the activity of PO.When cultivated with wheat,ryegrass,alfalfa and maize,CAT and DHA activities in the soil with ametryn is higher than the control,while the activity of PO has a downward trendency.Wheat,ryegrass,alfalfa and maize were cultivated in the soil which was added with 1 mg kg-1 ametryn or without ametryn for 10 d,the concentration of malonic acid,citric acid and malic acid in the rhizosphere soil were the highest respectively,and the lowest concentration in non rhizosphere soil.When cultivated with wheat and ryegrass in the soil with 1 mg kg-1 ametryn,the concentration of organic acids were reduced,while,when cultivated with alfalfa,the concentration of organic acids were increased,when cultivated with maize,the concentration of malonic acid,citric acid were reduced,the concentration of malic acid were increased.These results showed that organic acids in the soil were influenced by types of pesticides and plants.Activities of soil enzymes and the concentration of organic acids had the tendency that:rhizosphere soil>bulk soil>non-rhizosphere soil,indicating that rhizosphere environment is beneficial to degrade ametryn.