Study On The Behavior Of Prometryne In Soil Environment

Prometryne[2,4-bis（isopropylamino）-6-（methylthio）-s-triazine], a selective herbicide of the s-triazine chemical family, has been extensively used as a pre- or post-emergence controller of annual grasses and broadleaf weeds. Based on a classification scheme, the Koc value is within 311 to 614, indicating that prometryne is expected to have moderate to low mobility in soil and may be adsorbed to suspended solids and sediment in water. Prometryne’s production and use as a herbicide is expected to result in its direct release to the environment. Half-lives for the biodegradation of prometryne in aerobic and anaerobic soil have been reported as one to three months. A few of research has been conducted on the prometryne behavior in soils, so we enter on study the prometryne behavior of residue, sorption-desorption, mobility, leaching and so on in soils.The thesis includes three parts:In part one: Study on determination of prometryne residues in environment.A method for determination of prometryne residuses in soil, water and wheat of environment was developed by HPLC.Residue in soil was extracted with acetone, followed by cleanup with a silica gel column, residue was purified by LC-18 SPE column in water and was extracted with a mixture of V （methanol） : V （water） = 1 : 1 in wheat, which was adjusted to a volume with distilled water and passed through a LC-18 SPE column. The extracted of three samples were analysed by HPLC-UVD. The correlation coefficients （R²） of this method was 0.9999, and their calibration curves were linear in the range of 0.5-16 mg L^-1,limit of determination was 0.0125 mg L^-1. The recoveries ranged from 88.2-102.4 % for soil, 81.7-102.5 % for water, 88.4¹01.7 % for wheat, with the RSD was 6.3-6.4 %, 4.5-4.6 %, 3.6-5.5 % respectively.In part two: Effects of SOM, surfactant and pH on the sorption-desorption of prometryne in soils.Sorption and desorption of the herbicide prometryne in two types of soil subjected to the changes of pH and soil organic matter （SOM） and surfactant were investigated. The sorption and desorption isotherms were expressed by the Freundlich equation. Freundlich K_f and n values indicate that soil organic matter was the major factor affecting prometryne behavior in the test soils. We also quantified the prometryne sorption and desorption behavior in soils, which arose from the application of Triton X-100, a nonionic surfactant and change in pH. Application of Triton X-100 led to a general decrease in prometryne sorption to the soils and an increase in desorption from the soils when applied in dosages of the critical micella concentration （CMC） 0.5,1 and 2. At the concentration below the CMC, the non-ionic surfactant showed a tendency to decrease prometryne sorption and desorption. It appeared that Triton X-100 dosages above CMC were required to effectively mobilize prometryne. Results indicate that the maximum prometryne sorption and minimum prometryne desorption in soils were achieved when the solution pH was near its pK_?In part three: Study on the mobility of prometryne in soils and effect of surfactant Triton X-100 on remediation of prometryne contaminated soils and water.Influence of Triton X-100 on the mobility of prometryne in soils using soil thin-layer chromatography was examined. Effect of Triton X-100 on remediation of soils contaminated by prometryne using chemic washing method and remediation of water contaminated by prometryne using cloud point extraction （CPE） method was investigated. Surfactant Triton X-100 recycling by solvent extraction in surfactant-aided remediation was also tested. The result showed that Triton X-100 had effective remedy of contaminated soils at Triton X-100 concentrations above the critical micelle concentration （CMC）. The 250 mL of 100 CMC Triton X-100 solution entirety removed 50 g of 499.8 mg·kg^-1 prometryne contaminated soils after washing three cycles. Triton X-100 could also completely remedied contaminated water. The remediation rate of 100 mg·L^-1 prometryne solution was up to 100 % when using 100 CMC Triton X-100.