除草剂的土壤残留及对作物的影响

防除杂草所使用的除草剂散布到土壤以后,在土壤的物质变化过程中,进行了种种的代谢分解,随着时间的变化,最终除草剂失去它原有的特性,而变成简单的化合物或者变为自然界物质合成的材料。但是,在这些变化过程中,由于除草剂的种类和土壤环     

除草剂在土壤中的吸附行为研究

除草剂在土壤上的吸附和解吸行为是支配该除草剂在环境中的生物有效性和持久性的重要因素之一 ,同时对于预测除草剂在土壤和潜层水中的运动也是有重要作用。本文从吸附机理、实验技术、动力学、影响因素、常数的计算方法等方面阐述了除草剂在土壤中的吸附行为及其环境学意义。     

除草剂在土壤中的吸附行为研究

除草剂在土壤上的吸附和解吸行为是支配该除草剂在环境中的生物有效性和持久性的重要因素之一，同时对于预测除草剂在土壤和潜层水中的运动也是有重要作用。本文从吸附机理、实验技术、动力学、影响因素、常数的计算方法等方面阐述了除草剂在土壤中的吸附行为及其环境学意义。     

杀虫双环境影响和降解研究

杀虫双是由我国自行开发的沙蚕毒系的一个农药新品种,本研究旨在提供该农药对环境的影响及其降解特性的资料,为杀虫双的环境安全性评价、合理使用和出口创汇注册提供科学依据,完成了下述各项内容的研究: 1.环境样品(土壤、水和生物)的测试方法研究,以建立高灵敏度的仪器分析技术,解决杀虫双环境样品的痕量检测方法。 2.杀虫双在农作物(水稻)和土壤中的残留水平和消解动态研究,并获得南北两地两年的残留数据和杀虫双在作物和土壤中消失动态资料。 3.杀虫双在土壤中的降解特性和淋溶动态研究,主要完成杀虫双在土壤中的降解动力学特性(包括降解半衰期)、环境因素(温度等)对杀虫双降解过程的影响以及杀虫双在土壤中淋溶速率及对地下水可能影响的研究。 4.杀虫双在模拟水生和陆-水生态系统中的分配特性研究,主要完成~(36)S-杀虫双在模拟生态中的迁移,转化及归宿研究。 6.杀虫双对水生生物的影响,主要完成杀虫双对水生生物的急性毒性、慢性毒性和致突变试验,以及蓄积水平等研究。     

丁草胺与镉复合污染对土壤呼吸强度的影响

研究了除草剂丁草胺和重金属镉(Cd)复合污染对两种土壤呼吸强度的影响及其随时间的动态变化.结果表明,单一污染中,丁草胺和Cd对土壤呼吸强度的影响,随土样不同而异,随农药浓度及培养时间的变化而变化;复合污染中,两种土样的复合污染对土壤呼吸强度的影响存在明显的交互作用,与单一污染相比,对土壤呼吸强度的影响依次表现为:丁草胺＞Cd与丁草胺复合污染＞Cd.建立了丁草胺和Cd在不同浓度配比下对土壤呼吸强度影响的多元回归分析模型.     

除草剂的降解、代谢、毒性、污染的现状与展望

随着农业现代化的实现,除草剂在我国将会得到普遍应用。本文仅就除草剂的降解、代谢、毒性、污染的现状与展望综述如下。一、在土壤中的残留动态除草剂使用后,一部分挥敞、蒸发到大气中,一部分被阳光照射发生光化学分解,而大部分被土壤粒子所吸附,呈水溶液、悬浊液或气态而扩散于土壤中。在此过程中,一部分被农作物、杂草根系吸收,一部分被溶脱到地下,而大部分残留干耕作层土壤中,逐渐分解而消失。 1、蒸发一般除草剂从土壤表面的蒸发量很少,但对于易于挥发或者土壤中难以分解的药剂,蒸发就成为消失的主要原因。例如,氯苯胺灵(CIPC)在高温条件下迅速失去活性,其原因在于其易挥发性;敌草腈(DBN)在室内试验半衰期平均为6个月,但在田     

甲基叔丁基醚(MTBE)在不同粘性土壤中的吸附特性

土壤对有机物的吸附是污染土壤及地下水原位修复技术中的重要参数.通过静态间歇吸附实验研究了甲基叔丁基醚(MTBE)在不同粘性土壤中的吸附特性.结果表明,MTBE在粘性土壤中的吸附行为均可用线性方程很好描述,粘粒是土壤对MTBE吸附的主要影响因素,吸附常数与土壤粘粒含量呈y=4.382×10-3x-0.817 ×10-3直线关系.对不同温度下的吸附数据分析发现,粘性土壤对MTBE的平衡吸附量随温度的升高而降低,由吸附热力学推导可得等量吸附焓变△H与平衡吸附量无关,且△H＜0,表明该吸附为故热过程.     

粘土矿物修复重金属污染土壤

简要介绍了我国土壤重金属污染的现状与危害.通过粘土矿物在重金属污染土壤中净化功能的阐述,提出利用粘土矿物修复土壤重金属污染的观点.继而从天然和改性粘土矿物特性,叙述了粘土矿物修复土壤重金属污染的机制与应用进展及其影响因素.最后讨论了粘土矿物在修复土壤重金属污染过程中值得注意的几个问题,并展望了粘土矿物在该领域应用中的发展方向.     

除草剂对麦类病害发生的影响

本文根据现有的研究报道讨论了除草剂与麦类病害发生的关系。田间条件下,除草剂一般不抑制甚至有时还促进病害发生。除草剂的效应受剂量、作用时间、土壤理化性质的影响,但一般并不降低病原菌侵染潜力;而月,作物周际微生物群落对药剂的反应,寄主植物抗病性以及药剂混用的交互作用都是影响病害发生的因素。     

乙氧氟草醚在花生上的残留动态研究

为防止新除草剂乙氧氟醚对农业生态环境污染，作者进行了该农药在花生上残留动态试验研究。结果表明：乙氧氟草醚在土壤中的半衰期为１１～１２天，生长后期，花生壳、花生仁及花生植株中均未检出。同时提出了乙氧氟草醚在花生上的安全使用准则。     

Abiotic degradation (photodegradation and hydrolysis) of imidazolinone herbicides

The abiotic degradation of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was investigated under controlled conditions. Hydrolysis, where it occurred, and photodegradation both followed first-order kinetics for all herbicides. There was no hydrolysis of any of the herbicides in buffer solutions at pH 3 or pH 7; however, slow hydrolysis occurred at pH 9. Estimated half-lives for the three herbicides in solution in the dark were 6.5, 9.2 and 9.6 months for imazaquin, imazethapyr and imazapyr, respectively. Degradation of the herbicides in the light was considerably more rapid than in the dark with half lives for the three herbicides of 1.8, 9.8 and 9.1 days for imazaquin, imazethapyr and imazapyr, respectively. The presence of humic acids in the solution reduced the rate of photodegradation for all three herbicides, with higher concentrations of humic acids generally having greater effect. Photodegradation of imazethapyr was the least sensitive to humic acids. The enantioselectivity of photodegradation was investigated using imazaquin, with photodegradation occurring at the same rate for both enantiomers. Abiotic degradation of imidazolinone herbicides on the soil surface only occurred in the presence of light. The rate of degradation for all herbicides was slower than in solution, with half-lives of 15.3, 24.6 and 30.9 days for imazaquin, imazethapyr and imazapyr, respectively. Abiotic degradation of these herbicides is likely to be slow in the environment and is only likely to occur in clear water or on the soil surface.     

Abiotic degradation (photodegradation and hydrolysis) of imidazolinone herbicides

The abiotic degradation of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was investigated under controlled conditions. Hydrolysis, where it occurred, and photodegradation both followed first-order kinetics for all herbicides. There was no hydrolysis of any of the herbicides in buffer solutions at pH 3 or pH 7; however, slow hydrolysis occurred at pH 9. Estimated half-lives for the three herbicides in solution in the dark were 6.5, 9.2 and 9.6 months for imazaquin, imazethapyr and imazapyr, respectively. Degradation of the herbicides in the light was considerably more rapid than in the dark with half lives for the three herbicides of 1.8, 9.8 and 9.1 days for imazaquin, imazethapyr and imazapyr, respectively. The presence of humic acids in the solution reduced the rate of photodegradation for all three herbicides, with higher concentrations of humic acids generally having greater effect. Photodegradation of imazethapyr was the least sensitive to humic acids. The enantioselectivity of photodegradation was investigated using imazaquin, with photodegradation occurring at the same rate for both enantiomers. Abiotic degradation of imidazolinone herbicides on the soil surface only occurred in the presence of light. The rate of degradation for all herbicides was slower than in solution, with half-lives of 15.3, 24.6 and 30.9 days for imazaquin, imazethapyr and imazapyr, respectively. Abiotic degradation of these herbicides is likely to be slow in the environment and is only likely to occur in clear water or on the soil surface.     

Adsorption of imidazolinone herbicides on ferrihydrite-humic acid associations.

Adsorption of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was studied on two binary systems (ferrihydrite-humic acid) prepared by treating ferrihydrite (Fh) immediately after its precipitation with a soil humic acid (HA) at different loadings (4% and 8% HA content), and on a blank ferrihydrite sample prepared in the same way, but without HA addition. Imidazolinone adsorption on pure Fh and on the 4% Fh-HA decreased with increasing of the herbicide hydrophobicity (imazaquin相似文献   

Herbicide safeners: Tools for improving the efficacy and selectivity of herbicides

Abstract

Safeners (also known as antidotes) are chemical or biological agents that reduce the toxicity of herbicides to crop plants by a physiological or molecular mechanism. Commercialized safeners are mainly chemical compounds that enhance the tolerance of selected grass crops such as maize (Zea mays L.), grain sorghum [Sorghum bicolor (L.) Moench], rice (Oryza sativa L.), and wheat (Triticum aestivum L.) to chloroacetanilide, thiocarbamate, sulfonylurea, imidazolinone, and aryloxyphenoxypropionate herbicides. In practice, safeners are applied either to the crop prior to planting (seed safeners) or to the soil together with the herbicide, formulated as a prepackaged mixture. Safeners act as "bioregulators”; controlling the amount of a given herbicide that reaches its target site in an active form. A safener‐induced enhancement of the metabolic detoxification of herbicides in protected plants is the most apparent mechanism for the action of all commercialized safeners. Herbicide‐detoxifying enzymes such as glutathione transferases (GST), cytochrome P‐450 monooxygenases (CytP450), esterases, and UDP‐glucosyltransferases are induced by herbicide safeners. At the molecular level, safeners appear to act by activating or amplifying genes coding for these enzymes (e.g., GST).     

Utilization and degradation of imazaquin by a naturally occurring isolate of Arthrobacter crystallopoietes

A species of bacteria that is capable of utilizing imazaquin as the sole carbon source was isolated from soil with repeated imazaquin applications, and was identified as Arthrobacter crystallopoietes (designated as strain “WWX-1”). This isolate degrades imazaquin as high as 200 μg ml⁻¹, and the estimated dissipation half-lives increased from 1.51 d for the treatment at 50 μg ml⁻¹ to 4.75 d for 200 μg ml⁻¹. Optimal growth of WWX-1 in mineral salt medium with 50 μg ml⁻¹ imazaquin was obtained at 35 °C and a pH of 5.0. Growth of WWX-1 was also observed in mineral salt medium with the addition of other imidazolinone herbicides such as imazethapyr and imazapyr, but not with different classes of herbicides such as metsulfuron-methyl. Two imazaquin metabolites were detected, and spectral analysis with HPLC–MS, ¹H NMR, and IR revealed one metabolite with a molecular weight (MW) of 199 as quinoline-2,3-dicarboxylic anhydride. We propose that A. crystallopoietes (WWX-1) could serve as an efficient biodegradation system for remediation of water and soils that are heavily contaminated with imazaquin or other structurally similar chemicals.     

农业管理实践对除草剂环境行为的影响

除草剂的土壤环境行为与受人为控制的农业管理实践有密切的关系。本文通过文献调研综合分析了农田灌溉、耕作制度、施肥、作物秸秆还田和除草剂施用量等农业管理实践对除草剂土壤环境行为的影响 ,并据此提出了减轻除草剂污染地下水的若干思路。     

Toxic effects of four sulphonylureas herbicides on soil microbial biomass

The effect of four triazinyl-sulfonylurea herbicides (cinosulfuron, prosulfuron, thifensulfuron methyl, triasulfuron) on soil microbial biomass, soil respiration, metabolic activity, metabolic quotient, and some enzymatic activities (acid and alkaline phosphatase, β-glucosidase, arylsulphatase, and fluorescein diacetate hydrolysis) were monitored under controlled conditions over 30 days. The herbicides were applied at the normal field dose (FD) and at ten-fold (10 FD) the field dose, in order to mimic a long term toxic effect. The measured soil microbial parameters showed that the FD had slight effects on soil microflora, while at 10 FD the tested herbicides exerted a stronger detrimental effect on soil microbial biomass and its biochemical activities.     

Toxic effects of four sulphonylureas herbicides on soil microbial biomass

The effect of four triazinyl-sulfonylurea herbicides (cinosulfuron, prosulfuron, thifensulfuron methyl, triasulfuron) on soil microbial biomass, soil respiration, metabolic activity, metabolic quotient, and some enzymatic activities (acid and alkaline phosphatase, β-glucosidase, arylsulphatase, and fluorescein diacetate hydrolysis) were monitored under controlled conditions over 30 days. The herbicides were applied at the normal field dose (FD) and at ten-fold (10 FD) the field dose, in order to mimic a long term toxic effect. The measured soil microbial parameters showed that the FD had slight effects on soil microflora, while at 10 FD the tested herbicides exerted a stronger detrimental effect on soil microbial biomass and its biochemical activities.     

Sorption, degradation, and leaching of tebuthiuron and diuron in soil columns

A study in small outdoor lysimeters was carried out to determine the leaching of the herbicides tebuthiuron and diuron in different soil types, using undisturbed soil columns. Soil sorption and degradation for both herbicides were also studied in the laboratory. The multi-layered AF (Attenuation Factor) model was evaluated for predicting the herbicides leaching in undisturbed soil columns. Tebuthiuron leached in greater amounts than diuron in both soils. Sorption was well represented by linear and Freundlich equations, however parameters from the linear equations were used in the AF model. In general, both herbicides presented very low sorption, with diuron presenting lower values of sorption coefficient than tebuthiuron in the two soils. Chromatographic data indicated rapid late degradation of diuron and tebuthiuron in both soil types at two different depths. Simple exponential equation was not able to represent degradation, thus a bi-exponential equation was used, and some model adjusting was needed. Average measured amounts of each herbicide were compared with amounts predicted by the multi-layered-soil AF model. The AF model was able to predict leaching amounts in the sandy soil, especially for diuron, however it did not perform well in the clayey soil.     

Sorption-desorption behavior of metsulfuron-methyl and sulfosulfuron in soils

Sorption of metsulfuron-methyl and sulfosulfuron were studied in five Indian soils using batch sorption method. Freundlich adsorption equation described the sorption of herbicides with K(f) (adsorption coefficient) values ranging between 0.21 and 1.88 (metsulfuron-methyl) and 0.37 and 1.17 (sulfosulfuron). Adsorption isotherms were L-type suggesting that the herbicides sorption decreased with increase in the initial concentration of the herbicide in the solution. The K(f) for metsulfuron-methyl showed good positive correlation with silt content (significant at p = 0.01) and strong negative correlation with the soil pH (significant at p = 0.05) while sorption of sulfosulfuron did not correlate with any of the soil parameter. Desorption of herbicides was concentration dependent and, in general, sulfosulfuron showed higher desorption than the metsulfuron-methyl. The study indicates that these herbicides are poorly sorbed in the Indian soil types and there may be a possibility of their leaching to lower soil profiles.