Study On The Translocation Of Atrazine In Soils And Its Bioavailability To Weeds

Worldwide,pesticide use has increased yearly.Pesticides play an important role in controlling pests,plant diseases and ensuring crop yields.However,the excessive use of pesticides has brought about more serious environmental and ecological problems,and the pesticide residues has attracted moreattention overseas.Therefore,studying the migration behavior of pesticides in the soil environment and the bioavailability of herbicides for weeds is greatly significant for reduction use of pesticides and environmental protection to achieve sustainable use of resources.The adsorption-desorption and migration behaviors of atrazine in Nanjing soil,Yancheng soil and Jiangxi soil were determined by batch balance,thin layer chromatography and soil column leaching method.The results showed that the adsorption and desorption isotherms of atrazine in the three soils could be fitted by the Freundlich equation well.The adsorption capacity of atrazine gradually decreased in Nanjing,Yancheng and Jiangxi soils.Strong adsorption capacity indicated weak leaching performance.The conclusions drawn by thin layer chromatography and soil column leaching experiments were consistent with the adsorption desorption experiments.By predicting the relationship between adsorption constant(Kf)and soil physical and chemical properties,soil total carbon(TOC),soil total nitrogen(TN)and soil total phosphorus(TP)were positively correlated with atrazine adsorption capacity.There was negative hysteresis in Nanjing soil and Yancheng soil,and there was positive hysteresis in Jiangxi soil.The absolute values of the Kf of the three soils were all less than 5,the absolute value of Gibbs free energy change(ΔG)was less than 20,and the values of groundwater pollution exponent(GUS)were all greater than 2.8,indicating that the adsorption capacity of atrazine(ATR)on the three soils was weak.The adsorption total amount of atrazine by the three soils was less,meanwhile ATR migrated in the environment and polluted groundwater easily.The bioavailability of weeds was investigated.Barngard grass,rumex,amaranthus retroflexus and chenopodium glaucum were selected to experimental weeds,respectively.The effect of atrazine residues on the growth of these four weeds was studied.The result showed that the sensitivity of the four weeds to atrazine was from low to high:barngard grass,rumex,amaranthus retroflexus,and chenopodium glaucum.Barngard grass could grow at the concentration of 0.2 mg kg-1 at atrazine,although grass was inhibited but not herbicidal.Chenopodium glaucum,rumex,and amaranthus retroflexus were dead atthe concentrion of atrazine 0.04 mg kg-1,0.1 mg kg-1,0.09 mg kg-1,respectively.Meanwhile,we studied the effect of atrazine residues in soil on the application amount of atrazine to remove weeds.Chenopodium glaucum was sensitive to atrazine spray,and low concentration of Atrazine spray could achieve the herbicidal effect.Barngard grass could not survive after spraying 90 mg L-1 atrazine solution at an ATR residual concentration of 0.05 mg kg-1,and could be dead by spraying 60 mg L-1 atrazine solution at an ATR residual concentration of 0.1 mg kg-1 in soil.Rumex could be weeded out by spraying 90 mg L-1 atrazine solution at a residual concentration of 0.1 mg kg-1 atrazine in soil.In the soil residual concentration of atrazine at a dose of 0.05 mg kg-1,the amaranthus retroflexus could not survive after spraying 40 mg L-1 atrazine solution.Finally,the effect of weed on pesticide residues was studied.When herbicide residues could kill the weeds,the small absolute amount of ATR residue in soil was used by weeds,and there was no significant difference in soil residue reduction compared with the unplanted weeds.However,when the amount of ATR residues in soil could not eliminate weeds,the absolute amount of ATR in the soil used by weeds was large,which was significantly different from that of non-planting.In summary,atrazine is a kind of pesticide that is easy to migrate but relatively stable.Frequent atrazine application will cause a large amount of residues in the environment.In addition,atrazine residues in soil can achieve weeding effect on sensitive weeds,and reduce the amount of its application,which can provide a basis for scientific and rational use of pesticides,and reducing the application dose of ATR.