Degradation Of Herbicides Atrazine And Acetochlor In Soil

Atrazine is a kind of trazine herbicides which was developed by Geigy Corporation in Switzerland in 1952.Acetochlor is a kind of amide herbicides which was developed by Monsanto Corporation in the United States in 1971.They are both widely used in the world because of their weedicidal spectrum and high efficiency.However,through the processes of migration,leaching and volatilization,atrazine and acetochlor remain in the soil transfer into the water,the atmosphere,and ultimately enriched to the organism,posing a threat to the ecological environment and human health.In order to help people understand their pollution patterns and harm to the environment,use them more scientifically and legitimately,it is significant to study the degradation behaviors in the soil.Firstly,the residual detection methods of atrazine and acetochlor in soils of Nanjing sand clay loam,Yancheng sand loam and Jiangxi clay loam were established.High performance liquid chromatography(HPLC)was used to determine atrazine in soil.The concentration of atrazine ranged from 0.1 mg/L to 10 mg/L with a correlation coefficient of 0.9997.Atrazine in the three soils was extracted by acetone:water with a volume ratio of 3:1,then was purified by the extraction of petroleum ether,and detected by HPLC.The average spiked recoveries of atrazine in the three soils ranged from 83.3%to 97.9%in Nanjing sand clay loam,94.61%to 97.64%in Yancheng sand loam,91.35%to 100.43%in Jiangxi clay loam,respectively.The relative standard deviations ranged from 1.02%to 8.43%in Nanjing sand clay loam,2.39%to 4.96%in Yancheng sand loam,2.75%to 4.13%in Jiangxi clay loam,respectively.Gas chromatography(GC)was used to determine acetochlor in soil.The concentration of acetochlor ranged from 0.1 mg/L to 1 mg/L with a correlation coefficient of 0.9999.Acetochlor in Nanjing sand clay loam and Yancheng sand loam was extracted with an acetone:water with a volume ratio of 3:1,acetochlor in Jiangxi clay loam was extracted with a mixed solution of acetone,water and ammonia,purified by a C-18 solid-phase extraction(SPE)column,and detected by GC.The average spiked recoveries of atrazine in the three soils ranged from 87.3%to 95.57%in Nanjing sand clay loam,91.46%to 98.33%in Yancheng sand loam,83.63%to 100.04%in Jiangxi clay loam,respectively.The relative standard deviations ranged from 1.28%to 3.02%in Nanjing sand clay loam,1.01%to 2.87%in Yancheng sand loam,2.42%to 5.30%in Jiangxi clay loam,respectively.All methods were suitable to use for analysis of pesticide residue.The effect of different environmental factors on the degradation of atrazine in soil was investigated.The results showed that the soil(Nanjing sand clay loam)moisture had a greater impact on the degradation of atrazine.When the soil moisture was 30%of the maximum water capacity in the field,the degradation half-life of atrazine was 77 d.When the soil moisture was 60%of the maximum water capacity in the field,the degradation half-life of atrazine was 43.3 d.The degradation rate was 1.8 times of the former.Under the single-factor condition,soil(Nanjing sand clay loam)microorganism had a weak effect on the degradation of atrazine.The degradation half-life of atrazine was 40.8 d in unsterilized soil and 46.2 d in sterilized soil.Illumination had a significant effect on the degradation of atrazine in sterilized soil(Nanjing sand clay loam).The degradation half-life of atrazine was 46.2 d under the condition of darkness and 12.2 d under the condition of Xenon lamp as the light source simulating sunlight.The degradation rate of atrazine under the light was 3.8 times of the darkness.The soil type had a great influence on the degradation of atrazine.The degradation half-life of atrazine was 43.3 d in Nanjing sand clay loam,99 d in Yancheng sand loam,34.6 d in Jiangxi clay loam,respectively.The rate of degradation in Jiangxi clay loam was about 1.3 times that of Nanjing sand clay loam and 2.9 times that of Yancheng sand loam.Soil clay content and pH were the main factors.Ten degradation products of atrazine in Jiangxi clay loam were determined by ultra-high performance liquid chromatography mass spectrometer(UPLC-MS/MS).Among them,DEHA,HA-Glc and DIA-Glc were found in Jiangxi clay loam for the first time.Possible degradation pathways of atrazine in soil was speculated.The influence of different environmental factors on the degradation of acetochlor in soil was studied.The results showed that soil(Nanjing sand clay loam)microorganism has a significant effect on the degradation of acetochlor.The degradation half-life of acetochlor was 3 d in unsterilized soil and 27.7 d in sterilized soil.The degradation rate was 9.2 times of the former.The soil(Nanjing sand clay loam)moisture had a greater impact on the degradation of acetochlor.When the soil moisture was 30%of the maximum water capacity in the field,the degradation half-life of acetochlor was 7.2 d.When the soil moisture is 60%of the maximum water capacity in the field,the degradation half-life of acetochlor was 3 d.The degradation rate was 2.4 times of the former.Under the single-factor condition,illumination had a significant effect on the degradation of acetochlor in soil(Nanjing sand clay loam).The degradation half-life of acetochlor was 27.7 d under the condition of darkness and 10.3 d under the condition of Xenon lamp as the light source simulating sunlight.The degradation rate of acetochlor under the light was 2.7 times of the darkness.The soil type also had a great influence on the degradation of acetochlor.The degradation half-life of acetochlor was 3 d in Nanjing sand clay loam,4.9 d in Yancheng sand loam,25.7 d in Jiangxi clay loam,respectively.The rate of degradation in Nanjing sand clay loam was about 1.6 times that of Yancheng sand loam and 8.6 times that of Jiangxi clay loam.Soil organic matter content and pH were the main factors.