精异丙甲草胺对小麦药害及其安全剂解毒作用初步研究

为了探索精异丙甲草胺在小麦田的应用技术,室内研究了精异丙甲草胺对小麦的安全性,对安全剂进行筛选,并对安全剂作用机制进行初步研究。结果表明,精异丙甲草胺对小麦的生长抑制作用随着土壤含水量增大及温度的下降而上升。对4种安全剂进行筛选,结果表明,解草酮0.5、5g/kg种子处理能够显著降低精异丙甲草胺对小麦的药害,解草啶、二氯丙烯胺、苯叉酰胺在低剂量下能够一定程度缓解精异丙甲草胺药害,但高剂量无缓解作用。进一步研究表明,解草酮0.5~4g/kg种子处理能够有效降低精异丙甲草胺150~600g/hm2(有效成分含量)造成的小麦药害,缓解率均在20%以上,其中1g/kg解草酮种子处理缓解效果最好,提高小麦对精异丙甲草胺的耐药性可达4倍以上。生理指标测定结果表明,解草酮1g/kg种子处理可显著提高小麦出苗期(播后4~6d)GSTs比活力,而GSH含量与对照相当或降低。表明解草酮可能通过提高小麦GSTs活力来增强GSH对精异丙甲草胺的轭合代谢作用,而非通过增加GSH含量来提升精异丙甲草胺降解。     

鱼藤酮在3种土壤中的吸附-解吸附特性

为了综合评价鱼藤酮在土壤环境中的吸附-解吸附特性,采用批量平衡法,系统研究了鱼藤酮在砂壤土、黏壤土及壤土3种农业土壤中的吸附-解吸附行为。结果表明,鱼藤酮在3种土壤中的吸附-解吸附行为符合Freundlich模型 (R2≥0.946 8),吸附常数 (K_f-ads) 在1.52~11.39之间,吸附能力为:黏壤土 > 砂壤土 > 壤土;而解吸附常数 (K_f-des) 在1.02~4.55之间,解吸附强弱次序为壤土 > 黏壤土 > 砂壤土。鱼藤酮在砂壤土、黏壤土和壤土3种土壤中有机碳吸附常数 (K_OC) 分别为982、101 7和219,而滞后系数 (H) 分别为0.687 3、0.556 9和0.892 3,表明鱼藤酮在黏壤土及砂壤土中移动性较弱,有正迟滞作用,而在壤土中移动性较强,无迟滞作用。该研究将对鱼藤酮的环境风险评估具有一定的理论指导意义。     

咪鲜胺及其制剂在六种水稻土中的吸附

研究了咪鲜胺(prochloraz)及其制剂施保克(Sportak,25%咪鲜胺乳油)在6种水稻土中的吸附行为和吸附机理。结果表明:咪鲜胺和施保克在水稻土中的吸附平衡时间为5~10 h,其吸附过程符合Freundlich吸附等温式;咪鲜胺和施保克在6种水稻土中有机质吸附常数(KOM)的平均值分别为 2 439和2 111,表明它们易被水稻土吸附,属难移动的物质,且吸附反应自由能的变化量均小于40 kJ/mol, 表现为物理吸附过程;吸附常数(Kf值)与土壤理化性质的相关性分析结果表明,咪鲜胺和施保克在土壤中的吸附主要受土壤有机质含量、阳离子交换量和粘粒含量的影响,并呈正相关;咪鲜胺在加工成制剂后,不但在土壤中的吸附量减少了,而且Kf值也下降了近1/3。     

精异丙甲草胺不同剂量和苦荞不同种植密度的除草和产量效应

为了筛选苦荞田中适宜的96%精异丙甲草胺乳油剂量和种植密度的配置,以云荞1号为材料,设置人工除草(CK1)、不除草(CK2)以及96%精异丙甲草胺乳油剂量[分别为750 mL/hm~2(C1)、1 050 mL/hm~2(C2)、1 350 mL/hm~2(C3)、1 650 mL/hm~2(C4)]和种植密度[95万株/hm~2(A1)、145万株/hm~2(A2)、195万株/hm~2(A3)]配置处理,研究96%精异丙甲草胺乳油不同剂量和种植密度对苦荞田中的除草效应及苦荞产量的影响。结果表明,随着96%精异丙甲草胺乳油剂量的增加,禾本科草和阔叶草的株数防效和鲜重防效表现值增大,并且对禾本科草的防效大于阔叶草。当96%精异丙甲草胺乳油剂量为C3和C4时,各种植密度下禾本科草的株数防效和鲜重防效大于50%,能抑制苦荞出苗并影响其产量。当种植密度达到A3时,96%精异丙甲草胺乳油剂量为C3和C4下的苦荞产量很高,并且显著高于人工除草对照处理;但考虑到大量使用化学除草剂会导致农药残留,建议使用96%精异丙甲草胺乳油C3剂量。由于96%精异丙甲草胺乳油用量与土壤条件有密切的关系,因此不同地区要选好适合当地土壤的96%精异丙甲草胺乳油用量。     

Cu(Ⅱ)和温度对丁吡吗啉在土壤中吸附的影响

采用振荡平衡法研究了Cu(Ⅱ)和温度对丁吡吗啉在内蒙砂土,北京壤土,广西粘土中吸附等温线的影响。结果表明,丁吡吗啉添加Cu(Ⅱ)前后在3种土壤中的吸附均可以采用Langmuir方程和Freundlich方程较好的描述,Cu(Ⅱ)降低了3种土壤对丁吡吗啉的吸附,3种土壤对丁吡吗啉的吸附量及Cu(Ⅱ)对土壤吸附丁吡吗啉影响的大小顺序为:粘土壤土砂土。根据综合试验结果,Cu(Ⅱ)与丁吡吗啉在占用土壤的吸附位点上可能存在竞争,土壤有机质含量高有利于Cu(Ⅱ)的吸附,丁吡吗啉与Cu(Ⅱ)之间的相互作用减少了土壤对丁吡吗啉的固定量,增加了其在土壤中的活动性;在10、25、35℃,丁吡吗啉在3种土壤中的吸附规律亦可以较好的用Langmuir方程和Freundlich方程描述,丁吡吗啉在3种土壤中的吸附会受到温度的影响,丁吡吗啉的吸附常数Kd和吸附自由能△G的绝对值随着温度的升高而减小,说明温度的升高不利于土壤对丁吡吗啉的吸附。     

烟嘧磺隆在土壤中的吸附及与土壤性质的相关性研究

采用平衡振荡法研究了烟嘧磺隆在8种不同类型土壤中的吸附,结果表明,其吸附过程均符合经典的Freundlich模型,最大吸附常数为6.891,最小吸附常数为0.798。根据土壤有机吸附常数和吸附自由能的大小对该除草剂的移动性能进行了评价,认为其在8种土壤中均以物理吸附为主,且具有中等或较高的移动性能。通过对吸附常数Kf与土壤有机质含量、粘土含量和pH值的关系进行分析,发现土壤有机质含量、粘土含量和pH值在吸附过程中均属支配因素,Kf与土壤有机质含量、粘土含量呈正相关,而与土壤pH值呈负相关。     

丙炔氟草胺与精异丙甲草胺复配对花生田杂草的防除效果

为明确丙炔氟草胺、精异丙甲草胺的联合作用效果和50%丙炔氟草胺·精异丙甲草胺SE(悬乳剂)对花生田杂草的防除效果以及对花生的安全性,采用土壤喷雾法测定2种除草剂室内联合作用试验,并对筛选的50%丙炔氟草胺·精异丙甲草胺SE进行田间药效试验。丙炔氟草胺、精异丙甲草胺以质量比1∶9复配对花生田一年生杂草的联合作用较好,50%丙炔氟草胺·精异丙甲草胺SE的推荐使用剂量为600～750 g a. i./hm~2,施药后45 d对杂草的总体鲜重防效可达到93. 5%～96. 4%。丙炔氟草胺、精异丙甲草胺复配互补性强,对反枝苋等杂草增效作用明显,50%丙炔氟草胺·精异丙甲草胺(SE)能够有效防除花生田一年生杂草,并对花生安全。     

三氟苯嘧啶在5种土壤中的吸附与解吸附行为

为研究三氟苯嘧啶的吸附-解吸附特性,采用振荡平衡法研究了三氟苯嘧啶在采集于吉林通化、江苏扬州、江西萍乡、广西南宁和海南海口等地的5种土壤中的吸附-解吸附行为及其环境影响因素。结果表明:三氟苯嘧啶在土壤中的吸附动力学符合Elovich模型,吸附和解吸附等温线符合Freundlich模型,吸附常数在1.886~7.626。温度的升高更有利于吸附,土壤对三氟苯嘧啶的吸附主要是物理吸附;随着溶液中pH值的升高,土壤对三氟苯嘧啶的吸附能力逐渐下降。除广西南宁黏壤土外,三氟苯嘧啶在5种土壤中的解吸附过程中存在滞后现象,不易在土壤中长期积累,具有一定的迁移特性。     

毒死蜱和氰戊菊酯在土壤中的吸附与迁移

为评估被用作白蚁预防药剂的毒死蜱和氰戊菊酯在土壤中的移动性,采用平衡吸附法和薄层层析法分别测定了两种农药在浙江宁波地区的东钱湖土(粉砂质壤土)、青岭土(粉砂质壤土)和象山土(粉砂质黏壤土)3种土壤中的吸附常数(Kd)和迁移率(Rf)。结果表明,两种供试药剂在东钱湖土中的吸附等温线线性化程度均较高,而在青岭土和象山土中的吸附等温线均近似于 "L"型。从Kd和有机质吸附常数Koc的数值看,氰戊菊酯在土壤中的吸附作用主要受土壤有机质因素影响,而毒死蜱的吸附并非只受土壤有机质因素的影响。毒死蜱在3种供试土壤中的Kd和Rf值均高于氰戊菊酯。这表明由Kd值推测不同农药在土壤中的相对移动性可能会存在一定偏差。毒死蜱和氰戊菊酯在3种土壤中的Rf值由大到小的顺序为:东钱湖土>青岭土>象山土;而Kd值由大到小顺序为象山土>青岭土>东钱湖土。对Kd和Rf值与土壤理化性质的多元线性回归分析表明:1)土壤有机质含量和阳离子代换量在决定Kd和Rf值中所起的作用相互重叠;2)土壤有机质含量(或土壤阳离子代换量)和土壤黏粒含量是影响Kd和Rf值的关键因素,而土壤pH值对于Kd和Rf值无决定性影响。     

双氟磺草胺在不同类型土壤中的吸附与淋溶特性研究

农药在土壤中的吸附和淋溶特性是评价其环境行为的重要指标。采用批量平衡法和土柱淋溶法,研究了双氟磺草胺在小麦种植区3种代表性土壤中的吸附和淋溶特性。结果表明:双氟磺草胺在安徽黏土、山东砂质壤土和河南砂质黏壤土中的吸附规律均可以较好地用Freundlich方程描述,其吸附系数(Kf)在0.39~0.62之间;土壤有机碳归一化吸附系数(Koc)在66.91~81.35之间,表明双氟磺草胺在3种土壤中均属于难吸附型;吸附自由能(ΔG)在-10.90~-10.42kJ/mol之间,均属于物理吸附。双氟磺草胺在3种土壤中的淋出率在71.7%~74.1%之间,说明其在3种土壤中的淋溶性均较强。双氟磺草胺初始添加量和腐殖酸对淋出率具有一定影响。综合试验结果,认为双氟磺草胺在3种土壤中的吸附和淋溶可能受土壤有机质含量、黏粒含量、阳离子交换量和土壤pH值等多个因素的综合影响,其对地下水的污染风险较大,因此应引起高度重视。     

Adsorption-desorption studies of alachlor, metolachlor, EPTC, chlorothalonil and pirimiphos-methyl in contrasting soils

Five soils with different organic matter contents ranging from 0.48 to 10.4% were used to study the adsorption and desorption of alachlor, metolachor, EPTC, chlorothalonil and pirimiphos-methyl in batch experiments. The isotherm shapes according to Giles classification were S-type for alachlor, metolachlor and chlorothalonil, changing to L-type for the latter as the level of soil organic matter increased, and L-type for EPTC and pirimiphos-methyl. The adsorption isotherms fitted the Freundlich equation x/m = KfCe1/n. The Kf values increased with the increase of organic matter content. The amounts of pesticides adsorbed over a range of concentrations of 0.1-20 mg litre-1 reached 63.1% for alachlor, 69.2% for metolachlor, 89.3% for EPTC, 98.4% for chlorothalonil and 96.3% for pirimiphos-methyl. The increase of the amounts desorbed with acetone indicated that the sorption of organic compounds onto organic matter occurred principally via weak London-type induction forces, or dispersion forces which are characteristics of the physical adsorption process.     

Activity, adsorption and mobility of three acetanilide and two new amide herbicides

Activity, adsorption, and mobility of emulsifiable concentrate (EC) and microencapsulated (ME) formulations of alachlor and acetochlor as well as of metolachlor, S-metolachlor, dimethenamid and flufenacet were studied. Petri-dish bioassay, based on root response of oats ( Avena sativa L.), was used for their activity in sand and in a silty clay loam soil, and for determination of herbicide concentrations in soil solution (not adsorbed) and in column leachates of the adsorption and mobility studies respectively. Flufenacet and both acetochlor formulations showed the highest activity in both soils and ME-alachlor and metolachlor the lowest; the activity of dimethenamid, EC-alachlor and S-metolachlor was intermediate. Activity of both formulations of alachlor and acetochlor decreased with increasing organic matter content, but alachlor activity was reduced more than that of acetochlor. Lower amounts of dimethenamid and S-metolachlor were adsorbed by soil compared with the other herbicides and, consequently, greater amounts of these two herbicides were leached through that soil. None of the herbicides tested was detected below 30 cm. Less alachlor and acetochlor were biologically available in soil solution after their application as ME-formulations and, therefore, lower amounts of both ME-alachlor and ME-acetochlor were leached through the soil compared with those applied as EC-formulations.     

Bentazone Leaching in Spanish Soils

Adsorption, incubation and soil-column experiments with bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] were carried out in ten different soils from the marches surrounding the Doñana National Park (Huelva, SW Spain). Adsorption isotherms for the different soils showed a good fit with the Freundlich equation. Bentazone was poorly adsorbed in all the soils studied, with no significant relationship between theK_f values and soil characteristics. A significant correlation was obtained between the soil organic matter content and the distribution constant values (K_d) calculated at an equilibrium concentration of 200 μg cm⁻³. The low adsorption and non-degradation of bentazone on these soils suggest that the herbicide readily percolates through soils to reach the surface and ground waters. The mobility of bentazone through three soil columns was also studied. The mass balances carried out showed that bentazone was totally eluted from the soil columns. The theoretical model applied to explain bentazone leaching under our experimental conditions seems to be suitable for soil columns with a uniform water-flow rate.     

Copper and Zinc Competitive Adsorption: Desorption in Calcareous Soils

The behavior in competitive adsorption-desorption reactions of Cu and Zn was studied in four calcareous soils. Cu and Zn were added to the soil by Cu, Zn, and Cu+Zn sulfate solutions in a CaSO4 background. Soil sorption of these cations was described by equilibrium isotherms that fitted either Freundlich- or Langmuir type equations, although Cu desorption data fitted only Freundlich isotherms. Cu and Zn competition was quantified by distribution coefficients, Kd, relating cation distribution between soil and solute and by the competitive Langmuir equation. The competitive Langmuir equation was the better suited to describe the Cu-Zn competitive adsorption in these soils. Distribution coefficients presented lower values when both cations were present, decreasing when the Cu and Zn concentration in solution increased (decreasing soil affinity for these cations), thereby increasing their mobility through the soil. However, the distribution coefficient of specifically adsorbed Cu in equilibrium with cations extracted by a Mg (NO) solution increased with Cu concentration. Cu adsorption was more depres 3 se 2 d by Zn than Zn adsorption by Cu. The different behavior of Cu and Zn seems dependent on the percentage Ca (CO) and, to a lesser degree, on Cu and Zn organic matter complexes, free iro 3 n 2 content, and surface precipitation on oxides and carbonates.     

Adsorption,decomposition and movement of oxamyl in soil

A study was conducted of the behaviour of oxamyl in Israeli soils of varying clay and organic matter contents. The adsorption isotherms for oxamyl were linear, and the adsorption coefficient (K_d) could be correlated to the clay content of the soils, as well as to the organic matter content of the soil. Oxamyl adsorption was underestimated by using published correlations between the adsorption and the chemical properties of pesticides, such as their solubility or octan-1-ol-water partition coefficient. The decomposition of oxamyl in soils followed first-order kinetics. The half-life ranged from 4 to 33 days in a Bet Dagan soil. The reaction rate increased with increasing moisture content of the soil until field capacity was reached, at which point it levelled off. The Arrhenius relationship was followed, with degradation proceeding more rapidly at higher temperatures. In several soils of varying composition, which were kept at field capacity, no difference in the degradation rates was observed. Oxamyl was applied to a Bet Dagan soil from a point source in a single pulse, as a split application, and on a continuous basis. The distribution patterns of oxamyl under the various treatments differed significantly. After the single-pulse application, oxamyl was leached out of the emitter zone. While the split application decreased the oxamyl-free zone, the best results were obtained by continuous application, which gave a nearly uniform distribution of oxamyl in the soil.     

氯胺嘧草醚在土壤中的吸附行为研究

为评价氯胺嘧草醚的环境安全性,采用批量平衡法测定了氯胺嘧草醚在5种土壤中的吸附-解吸行为,并运用数学模型对其吸附-解吸特性及移动性能进行了分析。结果表明:氯胺嘧草醚在5种土壤中的等温吸附-解吸曲线符合Freundlich模型,吸附常数（Kf值）范围在6.991~18.49之间;不同土壤对其的吸附作用强弱依次为:黑土 > 水稻土 > 褐土 > 潮土 > 红土。氯胺嘧草醚在5种土壤中的有机碳吸附常数（KOC）范围在704.4~1 579之间,推测其在土壤中具有低移动性;薄层层析试验也表明,氯胺嘧草醚在土壤中的移动性较弱。氯胺嘧草醚在5种土壤中的吸附自由能绝对值均小于40 kJ/mol,表明其吸附机理主要是物理吸附。其Kf值与土壤有机质含量、黏粒含量呈正相关,而与土壤pH值呈负相关。解吸试验表明,氯胺醚在其中3种土壤中的解吸过程存在滞后现象。研究表明,在正常使用情况下,氯胺嘧草醚不易对地表水或地下水造成污染风险。     

Adsorption-desorption behaviour of flufenacet in five different soils of India

Adsorption-desorption of the herbicide flufenacet (FOE 5043) has been studied in five soils from different locations in India (Delhi, Ranchi, Nagpur, Kerala and Assam) varying in their physicochemical properties. The organic matter (OM) content varied from 0.072 to 0.864%, clay content from 2.5 to 43.7% and pH from 4.45 to 8.35. The adsorption studies were carried out using a batch equilibration technique. Ten grams of soil were equilibrated with 20 ml of aqueous 0.01 M CaCl2 solution containing different concentrations (0-30 mg litre-1) of flufenacet. After equilibration, an aliquot of supernatant was taken out for analysis. During desorption, the amount withdrawn for analysis was replenished with fresh 0.01 M CaCl2 solution and further equilibrated. Desorption studies were carried out with the 30 mg litre-1 concentration of flufenacet only. The adsorption studies revealed that there was moderate to high adsorption of flufenacet considering the comparatively low organic carbon content in the five test soils. Average Kd values ranged from 0.77 to 4.52 and Freundlich KF values from 0.76 to 4.39. The highest adsorption was observed in Kerala soil (OM 0.786%; clay 25%; pH 4.45) followed by Ranchi, Nagpur and Delhi soils, and the lowest in Assam soil (OM 0.553%; clay 2.5%; pH 6.87). The trend in adsorption could be attributed to the chemical nature of flufenacet and the physicochemical properties of the soil such as pH, OM and clay contents. OM and clay contents were positively correlated whereas pH was negatively correlated. Soils having low pH, high OM and high clay contents showed higher adsorption. Desorption studies revealed that there was a hysteresis effect in all the soils. Hysteresis coefficient values (ratio of n(ad) and n(des)) varied from 0.09 to 0.45. The study implies that, because of its moderate to high adsorption, flufenacet is likely to persist in soil for some time. However, the possibility of its movement by leaching or surface run off is less.