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为获得不同因素对异丙甲草胺水乳剂物理稳定性的影响规律,同时验证Turbiscan Lab分散稳定性分析仪预测和评价水乳剂物理稳定性的可行性,利用Turbiscan Lab分散稳定性分析仪,结合加速试验[(54±2)℃,14d]结果,研究了乳化剂用量、体系pH和电解质离子等对磷酸酯盐稳定的异丙甲草胺水乳剂物理稳定性的影响。结果表明:乳化剂三苯乙烯基苯酚聚氧乙烯醚磷酸酯三乙醇胺盐(SCP)用量为6.0%(质量分数)时,水乳剂稳定性最好;过酸或过碱均会破坏水乳剂的稳定性,pH=9时水乳剂可获得较好的稳定性;Mg2+压缩油水界面双电层,导致水乳剂稳定性下降,且Mg2+添加浓度越大,水乳剂越不稳定。Turbiscan Lab分散稳定性分析仪以多重光散射为技术核心,在不破坏样品的前提下,能够准确测定乳状液中浮油、沉淀和液滴粒径大小的变化情况,与加速试验结果吻合度高,不仅能够缩短试验周期,而且可以分析不稳定现象发生的机理。 相似文献
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Metolachlor retention on a Sharkey clay soil was quantified using a kinetic batch method for different initial solution concentrations.Time-dependent adsorption was carried out by monitoring solution concentration at different reaction times.Adsorption was kinetic multireaction model which includes reverible and irreversible retention processes of the equilibrium and kinetic types,The predictive capability of the model for the dexcription of experimental results for metolachlor retention was examined and proved to be adequate。 相似文献
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BACKGROUND: Variations in soil properties with depth influence retention and degradation of pesticides. Understanding how soil properties within a profile affect pesticide retention and degradation will result in more accurate prediction by simulation models of pesticide fate and potential groundwater contamination. Metolachlor is more persistent than other acetanilide herbicides in the soil environment and has the potential to leach into groundwater. Reasonably, information is needed about the dissipation and eventual fate of metolachlor in subsoils. The objectives were to evaluate the adsorption and desorption characteristics and to determine the dissipation rates of metolachlor in both surface and subsurface soil samples. RESULTS: Adsorption of metolachlor was greater in the high‐organic‐matter surface soil than in subsoils. Lower adsorption distribution coefficient (Kads) values with increasing depth indicated less adsorption at lower depths and greater leaching potential of metolachlor after passage through the surface horizon. Desorption of metolachlor showed hysteresis, indicated by the higher adsorption slope (1/nads) compared with the desorption slope (1/ndes). Soils that adsorbed more metolachlor also desorbed less metolachlor. Metolachlor dissipation rates generally decreased with increasing soil depth. The first‐order dissipation rate was highest at the 0–50 cm depth (0.140 week?1) and lowest at the 350–425 cm depth (0.005 week?1). Degradation of the herbicide was significantly correlated with microbial activity in soils. CONCLUSION: Metolachlor that has escaped degradation or binding to organic matter at the soil surface might leach into the subsurface soil where it will dissipate slowly and be subject to transport to groundwater. Copyright © 2009 Society of Chemical Industry 相似文献
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Off-site movement of pesticides from furrow-irrigated agriculture has been a concern in the Ord River Irrigation Area, Western Australia. This paper reports on the effectiveness of incorporation of pesticides by cultivator or power harrows before irrigating, and spraying pesticides only onto beds to minimise off-site transport. Incorporation of pesticides by power harrows prior to irrigation was found to be more effective in decreasing the off-site transport of a more strongly sorbed pesticide, endosulfan. The average load of total endosulfan (alpha + beta + sulfate) decreased by 74% (P < 0.01) from 11.41 g ha(-1) from the conventionally treated bays to 2.96 g ha(-1) from the incorporated irrigation bays. The total average load of atrazine leaving the irrigation bays was decreased by 81% (P < 0.05) from 87.82 g ha(-1) under the conventional practice of spraying the whole field to 16.95 g ha(-1) by spraying the beds only. A reduction of 52% in total average load of metolachlor was observed following incorporation with power harrows, but this was not significant. Incorporation by cultivator or by power harrows decreased the total load of atrazine or metolachlor leaving the irrigation bays over the whole irrigation period, but these treatments were not shown to be statistically significant, which may have been due to the limited number of field replicates. Incorporation of strongly sorbed pesticides (e.g. endosulfan) prior to irrigation significantly decreased the off-site transport of these pesticides in a furrow irrigation system and may be a useful practice to minimise off-site transport of other similar pesticides. Minimising off-site transport of weakly sorbed pesticides (e.g. atrazine and metolachlor) from a furrow irrigation system is more difficult. The nature of furrow irrigation makes it highly conducive to pesticide transport, particularly of weakly sorbed pesticides, and further work is needed to develop strategies to minimise the movement of this group of pesticides to water bodies. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(3-4):465-479
Abstract Soil organic matter and its chemical fractions have a profound impact on soil chemical and physical properties. In turn, the effect of management (cropping and tillage) on the quantity and chemical properties of soil organic matter can be substantial. The objective of this study was to compare the effects of specific tillage regimes and crop sequences commonly used in the central Great Plains of the United States on the quantity, quality, and distribution with depth of soil organic carbon (SOC). Soils were sampled in 1 cm or 2 cm increments to a depth of 10 cm from experimental field plots on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll). The plots had been under 6 continuous tillage regimes since 1978 and cropped to continuous corn, continuous soybean, or corn‐soybean in rotation since 1985. Soils were analyzed for total SOC, fulvic acid (FA) carbon, and humic acid (HA) carbon. No‐till and continuous corn (Zea mays L.) management generally had the highest SOC, with a sharp reduction in SOC below 2 cm. Only no‐till increased FA, which also decreased with depth, especially between 2 and 4 cm. Humic acid concentration was highest under continuous corn but was unaffected by tillage. Humic acid also was highest in the 1‐ to 2‐cm increment of continuous corn. Two ratios which are used as indices of degree of humification, HA/FA and (HA+FA)/SOC, gave different estimates of the effect of management. Only continuous com increased HA/FA, suggesting increased humification. No treatment affected (HA+FA)/SOC. Overall, continuous corn and no‐till contributed the greatest amounts of residue and maintained a soil environment conducive to preserving the resulting organic matter. These management options increase not only total SOC, but also alter the quality of that SOC as measured by HA and FA. These changes in SOC characteristics may have implications for long‐term soil quality and soil productivity. 相似文献
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Herbicides atrazine and metolachlor have been detected in water bodies across the world. The objective of this study was to assess the efficiency of 0‐m, 3‐m, 6‐m and 9‐m grass filter strips to reduce masses of dissolved metolachlor, atrazine and deethylatrazine (a degradation product of atrazine) exported in runoff. For that purpose, 16 uncultivated plots (3‐m wide × 65‐m long) with 0‐m‐, 3‐m‐, 6‐m‐ and 9‐m‐long grass filter strips were setup in a completely randomized block design. During four seasons, masses of dissolved atrazine, metolachlor and deethylatrazine were determined for the first four to five rain events, under natural rain conditions, after atrazine and metolachlor application. Generally, grass filter strips reduced exported herbicide masses by more than 90% and influenced atrazine and metolachlor dissipation kinetics in the field. The 3‐m grass filter strip (area ratio source/strip of 22:1) usually provided a reduction in exported herbicide masses similar to the 6‐ or 9‐m grass filter strips. Therefore, under the present experimental soil and climate conditions, a grass filter strip of 3 m would be a good compromise between environmental protection of surface waters against atrazine and metolachlor contamination and conservation of agricultural land use. Such an approach contributes to the acceptability by producers to implement optimized best management practices such as vegetated filter strips for the preservation of the quality of water resources. 相似文献
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The resolved isomer of metolachlor, S-metolachlor, was registered in 1997. New formulations based primarily on the S-metolachlor isomer are more active on a gram for gram metolachlor basis than formulations based on a racemic mixture of metolachlor containing a 50:50 ratio of the R and S isomers. The labelled use rates of S-metolachlor-based products were reduced by 35% to give equivalent weed control to metolachlor. However, several companies have recently registered new metolachlor formulations with the same recommended use rates for weed control as S-metolachlor. This research was done to compare the soil behaviour and the biological activity of metolachlor and S-metolachlor in different soils under greenhouse and field conditions. Although K(d) ranged from 1.6 to 6.9 across the five soils, there were no differences in the binding of metolachlor and S-metolachlor to soil or in the rate of soil solution dissipation in a given soil. However, both greenhouse and field studies showed that S-metolachlor was 1.4-3-fold more active than metolachlor against Echinochloa crus-galli (L.) Beauv. in five different soils and that S-metolachlor was more active than metolachlor in three Colorado field locations. When the rates of metolachlor and S-metolachlor were adjusted for S isomer concentrations in the formulations, there were no differences between the formulations in field, greenhouse or bioassay studies. Thus herbicidal activity is due to the S isomers, with the R isomers being largely inactive. 相似文献