拉草(Alachlor或Lasso [2-chloro-2, 6 –diethyl-N-(methoxymethyl) acetanilide])是一種萌芽前處理且具有選擇性之殺草劑。設計土壤管柱(Soil column)及圓型容器(Circular container)等裝置研究拉草在淋洗與不淋洗的條件下，於不同溫度及不同時間內在土壤中之垂直與水平移動及殘留情形，若不以水滲濾時拉草在土壤中也會移動至未處理相鄰之土壤中，唯其程度較以水滲濾時為小。拉草經水淋洗後在土壤中之移動與土壤質地有關，其垂直與水平移動在砂質壤中皆比在坋質壤土中為明顯。拉草在不同之土壤及殺菌，未經殺菌處理下之分解有所差別，其分解速率隨著土壤有機質含量增加而增加，而且在殺菌土壤中之分解較未經殺菌之土壤慢。其殘留量分別為坋質粘壤土有67.5%，而在砂質壤土中有54.9%，坋質壤土中有59.4%。拉草在黑暗中不被分解，但在日光下照射，皆有分解現象發生，其分解產物經GC、TLC、MS、IR及NMR等儀器分析時，除了未變化之拉草[Alachlor(I),55.1%]外，被確認出來的分解產物有2-Chloro-2’,6’-diethylacetanilide (II) 11.0%; 2,6-Diethylaniline (III) 8.0%; 2’,6’-Diethyl acetanilide (IV) 4.6%; Monochloroacetic acid (Ⅴ) 14.6%; 2,6 –Diethyl-N-(methoxy-methyl) aniline (Ⅵ) 5.2%和1-Chloroacety1-2,3-dihydro-7-ethyl-indole (Ⅶ) 1.5%等六種。

In order to study the environmental degradation of Alachlor or Lasso, [2-Chloro-2', 6'-diethyl-N-(methoxymethyl) acetanilide) , after applied in the field, experiments have done on the degradation, residues and movement in soils. Some results are summarized as follows: The degradation and movement of alachlor in different soil types was tested in the laboratory under leaching and nonleaching conditions, at different temperatures and various incubation periods. Different apparatus of soil column and circular container had been especially designed for testing the vertical and horizontal movement of the herbicide in soil with and without water. The movement with water through soils was, to a large extent, a function of the soil types. When no water was percolated the herbicide also degraded and moved into untreated soil, but to a lesser degree. The herbicide alachlor was not degraded in the dark. Exposure of alachor to sunlight for 8 hr resulted in the degradation of the herbicide. The degradation was more rapid with non-sterile soils but less with sterile soils. The residues of alachlor after irradiation under sunlight were 67.5% in the silty clay loam and 54.1% in the sandy loam, 59.4% in the silty loam soils. Higher the organic matters content resulted the higher amount of residues. Alachlor decompoed under the sunlight irradiation in soils. Degradation products were detected and identified by GC. TLC. IR. NMR and Mass Spectra after �h�photodecomposition of alachlor. Except alachlor (I, 55.1 %). the others were i dent if ied with authentic compounds as 2-Chloro•2'. 6'-diethylacetanilide (n. 11.0%), 2,6-Diethylaniline (m. 8.0%), 2',6'-Diethyl acetanilide (N', 4.6%), Monochloroacetic acid (V. 14.6%), 2',6 Diethyl-N-(methoxymethyl) aniline (VI, 5.2%) and one minor component was identified by mass spectra as 1,:,Chloroacetyl-2,3- dihydro-? -ethylindole (VII, 1. 5%) .