High-performance liquid chromatography (HPLC) as a tool for monitoring the fate of fluazinam in soil

Fluazinam is a widely used pesticide employed against the fungal disease late blight in potato cultivation. A specific, repeatable, and rapid high-performance liquid chromatography (HPLC) method utilizing a diode array detector (DAD) was developed to determine the presence of fluazinam in soil. The method consists of acetonitrile (ACN) extraction, clean-up with solid-phase extraction (SPE), and separation using a mobile phase consisting of 70% ACN and 30% water (v/v), including 0.02% acetic acid. HPLC was performed with a C18 column and the detection wavelength was 240 nm. The method was successfully applied to an incubation experiment and to soil samples taken from potato fields where fluazinam had been applied two to three times during the on-going growing season. In the 90-day incubation experiment, analytical standard fluazinam and the commercial fungicide Shirlan^® were added to soil samples that had never been treated with fluazinam, and were then extracted with ACN and 0.01 M calcium chloride (CaCl₂). Fluazinam was not extractable with CaCl₂, indicating that it does not leach to watercourses in the dissolved form. Recovery with ACN extraction for sandy soils was 72–95% immediately after application and 53–73% after 90 days of incubation. Out of the eight potato field soil samples, fluazinam was found in two samples at concentrations of 2.1 mg kg^?1 and 1.9 mg kg^?1, well above the limit of quantification (0.1 mg kg^?1).     

Persistence of diflubenzuron and bay sir 8514 in natural and sterile sandy loam and organic soils

Abstract

Disappearance rates of 10 ppm technical diflubenzuron (N(((4‐chloro‐phenyl)amino)carbonyl)‐2,6‐diflurobenzamide, Dimilin^®) and BAY SIR 8514 (2‐chloro‐N(((4‐trifluoromethoxyphenyl)amino)carbonyl)benzamide) applied on quartz sand to natural sandy loam and muck soils were significantly greater than for the corresponding sterilized soils, e.g. 47–51% vs. 68–87% BAY SIR 8514 and 2–12% vs. 80–87% diflubenzuron remaining at 12 wk, indicating that soil microorganisms play a major role in their degradation. Kinetic analysis of the data based on a first order dependence on the insecticide concentration showed that the rate constants for these disappearance reactions decreased with time.     

The penetration of formulated guthion® spray through selected fabrics

Abstract

A technique for comparing pesticide penetration through fabric was devised. It involved passing fabric swatches through a controlled spray system and measuring the pesticide residue transferring on and through the tested fabric. Six variations in fabric were selected for testing: 100% cotton woven chambray,

Scotch‐guard^® treated chambray, Tyvek^® , Crowntex^® , and two variations of Gore Tex^®. Guthion^® (azinphos‐methyl) was chosen as the insecticide for controlled use in this experiment because of its widespread use and relatively high toxicity.

Gas Chromatographie analysis of the amount of Guthion^® transferred through the outer fabric was made by the use of analysis of variance (ANOVA) and Duncan's multiple range test. The ANOVA for experiment replication showed no significant difference among the replications of each fabric. The treatment ANOVA was highly significant at the 0.01 level.

Duncan's multiple range test further analyzed the differences in the treatment, and three groups were found to be significantly different from each other. The two types of Gore Tex^®, Tyvek^® and Crowntex^® comprised the group permitting the least penetration. Scotch‐guard^® treated chambray followed, and untreated chambray allowed the greatest penetration.     

Effect of organic amendment on degradation and formation of bound residues of methabenzthiazuron in soil under constant climatic conditions

Abstract

The degradation of [phenyl‐U‐¹⁴C]methabenzthiazuron (MBT) and formation of bound residues in the surface soil of an orthic luvisol were studied under constant climatic conditions (20°C, 40 % of maximum water holding capacity). In two treatments (with and without preincubation in the soil) maize straw was amended at a rate of 1.5 g/100 g dry soil in addition to the application of MBT. The mineralization of uniformly labeled maize straw was studied simultaneously. In additional flasks, MBT was incubated at 0, 10 and 30°C with and without addition of maize straw.

The turnover of the amended maize straw led to an enhanced dissipation of MBT which was mainly due to the formation of bound residues. This corresponded to a higher microbial activity in the soil after straw amendment and the intensive mineralization of the radiolabeled maize straw. About 2–3 % of the applied radioactivity from the radiolabeled maize straw was measured in the soil microbial biomass 10 and 40 days after application whereas ¹⁴C from MBT was only incorporated into soil microbial biomass in the treatments with straw amendment.

Within the bound residue fractions relatively more radioactivity was measured in fulvic and humic acids after straw amendment. Increasing temperatures promoted the dissipation of MBT and the formation of bound residues in both treatments, but without amendment of maize straw these effects were far less pronounced. The laboratory scale degradation experiment led to similar results as were found in a corresponding lysimeter study. Differences that were observed could be explained by different temperature regimes of the experiments and time of aging in soil.     

Summary of efficacy evaluations using aerially applied Gypchek® against gypsy moth in the U.S.A.

Abstract

Gypchek^®, the gypsy moth (Lymantria dispar L.) nucleopolyhedrosis virus product, is manufactured by the United States Department of Agriculture (USDA) Forest Service, and Animal and Plant Health Inspection Service under controlled conditions in a laboratory strain of gypsy moth larvae. Gypchek was registered with the U.S. Environmental Protection Agency in 1978 as a general use pesticide to control gypsy moth. This product has been the subject of intense research and development targeted toward maximizing efficacy while minimizing the cost of production and application. The current Gypchek tank mix is applied at 1.25 × 10¹²occlusion bodies (OB's) per hectare for each of two applications (3‐days apart) at 18.7 litres/ha per application.     

A fluorometric method to determine rainfastness,volatilization and photostability of glyphosate from glass slides,after application of vision® with two adjuvants

Abstract

A fluorometric method was developed to quantify glyphosate loss from glass surfaces after exposure to the natural forest environment. The method was based on the principle of converting glyphosate into glycine, followed by the fluorogenic labeling with o‐phthalaldehyde. A fluorometer (with λ _Ex = 360 nm / λ_Em =430 nm) was used to quantify the derivatized fluorogenic compound. Response was linear over the concentration range of 143, 286, 572, 858 and 1144 μg of glyphosate (acid equivalent, AE) per mL of the diluted Vision® formulation. Three end‐use mixtures of Vision® were prepared, each at a concentration of 28.6 g AE/L, without and with two adjuvants, Ethomeen® T/25 at 4.5 mL/L and Silwet^® L‐77 at 1.5 mL/L. Several dilutions of the end‐use mixtures were applied on glass slides without and with the coating of cuticular wax extracted from trembling aspen foliage. The slides were left for 5 days in a forest opening to determine rainfastness, volatilization and photostability of glyphosate. The residues were quantified using the method developed. Three calibration curves were required because Silwet decreased the fluorometric response of glyphosate, whereas Ethomeen increased it. The minimum detection limit was 143 μg of glyphosate/mL. Glyphosate was resistant to volatilization and sunlight‐mediated degradation, regardless of the presence of wax coating or the adjuvants. About 64% of the applied glyphosate was washed off after a 9.6 mm rainfall when no adjuvant was present. Both adjuvants provided some amount of rain‐protection to glyphosate, but Silwet reduced the washoff to a greater extent (46%) than Ethomeen (55%).     

Dissipation of DDT in natural water under field conditions

Abstract

¹⁴C‐DDT dissipated gradually from natural water under outdoor conditions and declined to 40% of the applied radioactivity after 5 months. The losses are due to adsorption to particulates and volatilization from the water surface. In natural water DDT undergoes gradual conversion to DDE as the major degradation product and to a lesser extent to DDD. It may be concluded that DDT dissipates and degrades fairly rapidly in subtropical natural waters. Adsorption to particulate matter contributes to partial “removal” of DDT.     

Persistence of granular and EC formulations of chlorpyrifos in a mineral and an organic soil incubated in open and closed containers

Abstract

Samples of a mineral soil (Plainfield sand) and an organic soil (muck) were treated with granular and EC formulations of chlorpyrifos and incubated at 27±1°C and 65±5% RH in open and closed containers. Duplicate samples of each soil‐formulation‐container combination were analyzed for residual chlorpyrifos during a 23 wk period. The disappearance rates observed demonstrate that the relative importance of formulation and containment on overall persistence depends on soil type. For the mineral soil, disappearance was slower from closed containers and formulation had only a slight effect while, in the organic soil the granular formulation disappeared slower than the EC and there was little difference between open and closed containers. The relative importance of degradation and volatilization in the disappearance of chlorpyrifos from soil is discussed.     

Impact of repeated pesticide applications on the binding and release of methyl 14C-monocrotophos and U-ring labelled 14C-carbaryl to soil matrices under field conditions

The dissipation of (O-methyl-¹⁴C) monocrotophos and U-ring labelled ¹⁴C-carbaryl was monitored for over two years in absence and presence of other insecticides using in situ soil columns. The dissipation of ¹⁴C-monocrotophos from soil treated with methomyl and carbaryl showed a faster rate of downward movement than in a control column tagged with the labelled insecticide alone. The same trend was observed in experiments with ¹⁴C-carbaryl that dissipated more readily in soil treated with non-labelled monocrotophos and methomyl. In the presence of other insecticides the percentage of bound residues was generally lower than in control experiments. The bound residues at the top of the column are released at a low rate under conditions prevailing in the field. The overall time required for dissipation of 50% of monocrotophos and carbaryl (t₅₀) as estimated from control experiment was approximately 20 and 24 weeks, respectively. The data indicate that repeated applications of pesticides might enhance the release of ¹⁴C-bound residues.     

Comparison of the droplet size spectra produced by rotary atomizers and hydraulic nozzles under simulated aerial application conditions

Abstract

A wind tunnel was used to characterize the droplet size spectra of liquid sprays from several different atomizers and nozzles used under simulated aerial application conditions. The atomizers included a D8–46 nozzle, a Through Valve Boom (TVB) nozzle, and rotary cage and drum atomizers.

The D8–46 hydraulic nozzle was evaluated, using water, at orientations of 0, 10, 20, 30, 40, 50, 60, 70, 80 and 90° relative to 145 and 180 km/h airstreams. The TVB nozzle was evaluated using water, water with isopropyl alcohol, and water with a non‐ionic surfactant at airstream velocities between 130 and 180 km/h. The rotary atomizers were evaluated at different rotation rates, flow rates of water and an insecticide, in 130 and 180 km/h airstreams.

The volumetric droplet size spectra parameters (D_vo.x) decreased as the angle of the D8–46 nozzle and the airstream velocity increased. Empirical models were developed to predict these values for different windspeed and nozzle angle conditions. The TVB nozzle produced larger droplets than the other atomizers under similar conditions, with a decrease in the D_vo.x parameter values as the airstream velocity increased.

The D_vo.x parameter values produced by the rotary atomizers increased as the liquid flow rate increased, and as the rotation rate and airstream velocity decreased, and were lower for the insecticide than for water. The slotted rotary drum atomizer gave the best control over droplet size, generally producing mono‐modal droplet size spectra where the other atomizers often produced bi‐ and multimodal spectra.     

Factors affecting the removal of aflatoxin M1 from food model by Lactobacillus and Bifidobacterium strains

This paper describes the ability of six dairy strains of Lactobacillus and Bifidobacterium to remove aflatoxin M₁ (AFM₁) from phosphate-buffered saline (PBS) and reconstituted milk. Bacteria were incubated in both PBS and reconstituted milk containing 5, 10 and 20 ng mL^?1 for 0, 4 and 24 h at 37°C. After centrifugation the concentration of AFM₁ was determined in the supernatant fraction using high-performance liquid chromatography. The binding abilities of AFM₁ by viable (10⁸ CFU mL^?1) and heat-killed Lactobacillus and Bifidobacterium strains in PBS ranged from 10.22 to 26.65% and 14.04 to 28.97%, respectively. Similarly, AFM₁-binding capacity in reconstituted milk was found to range from 7.85 to 25.94% and from 12.85 to 27.31% for viable and heat-killed bacteria, respectively within 4 h. While B. bifidum Bb 13 was the best binder, the poorest removal was achieved by L. acidophilus NCC 68. Binding was reversible, and a small proportion of AFM₁ was released back into the solution. The toxin concentration and incubation period had no effect on the removal of AFM₁ by bacteria both in PBS and reconstituted milk.     

Biodegradation of Trifluralin in Harran Soil

Abstract

Degradation of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) was investigated in soils taken from three different locations at Harran region of Turkey under laboratory conditions. Surface (0–10 cm) soils, which were taken from a pesticide untreated field Gürgelen, Harran-1 and Ikizce regions in the Harran Plain, were incubated in biometer flasks for 350 days at 25°C. Ring-UL-¹⁴C-trifluralin was applied at the rate of 2 µg g^?1 with 78.7 kBq radioactivity per 100 g soil flask. Evolved ¹⁴CO₂ was monitored in KOH traps throughout the experiment. Periodically, soil sub-samples were removed and extracted by supercritical fluid extraction (SFE). Unextractable soil-bound ¹⁴C residues were determined by combustion. During the 350 days incubation period 6.6, 5.4, and 3.3% of the applied radiocarbon was evolved as ¹⁴CO₂ from the Harran-1, Gürgelen, and Ikizce soil, respectively. At the end of 350 days the SFE-extractable and bound ¹⁴C-trifluralin residues were 39.0 and 29.2% of the initially applied herbicide in Gürgelen soil. The corresponding values for Harran-1 and Ikizce soils were 36.2, 28.4% and 41.6, 18.5% respectively.     

Fate and degradation of triasulfuron in soil and water under laboratory conditions

The behavior and fate of triasulfuron (TRS) in water and soil systems were examined in laboratory studies. The degradation of TRS in both buffer solution and soil was highly pH-sensitive. The rate of degradation could be described with a pseudo first-order kinetic and was much faster at pH 4 than at pH 7 and 9. Aqueous hydrolysis occurred by cleavage of the sulfonylurea bridge to form 2-(2-chloroethoxy) benzenesulfonamide (CBSA) and [(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] (AMMT). AMMT was unstable in aqueous solutions in any pH condition but it degraded more quickly at pH 4 and 9. CBSA did not degrade in aqueous solutions or in enriched cultures but it underwent a quick degradation in the soil. The rates of TRS degradation in sterile and non-sterile soils were similar, suggesting that microorganisms played a minimal role in the breakdown process. This hypothesis is supported by the results of studies on the degradation of TRS by enriched cultures during which the molecule underwent a prevalently chemical degradation.     

黑土胶体对铅的吸附动力学特征

利用虹吸法从采自于吉林省黑土中分别提取出粒级为5~10、2~5和1~2μm的3种胶体,并通过批次实验法研究不同粒级黑土胶体对Pb2+的吸附动力学。结果表明,不同粒级土壤胶体对Pb2+的吸附过程均表现为快慢2个阶段,其中,10 min内呈现快速吸附阶段,之后为慢速吸附阶段。3种粒级土壤胶体5~10、2~5和1~2μm在pH为6、温度为25℃时,对Pb2+的饱和吸附量为114.45、126.98和131.89 mmol/kg。随pH从2升到6,粒级为5~10、2~5和1~2μm的3种胶体对Pb2+的饱和吸附量分别增加了928%、153%和142%。随温度从25℃升到55℃,粒级为5~10、2~5和1~2μm的3种胶体对Pb2+的饱和吸附量分别增加了16.56%、4.9%和4.89%。不同粒级胶体对Pb2+的吸附量由大到小依次为:1~2μm2~5μm5~10μm。不同粒级胶体对Pb2+的吸附动力学均较好地符合拉格朗日准二级动力学方程,说明该吸附过程以化学吸附为主。准二级动力学吸附速率常数表明,随着吸附剂粒径增大,吸附速率降低。4种温度范围内随着温度升高,吸附速率加快。吸附过程的限速步骤为颗粒间扩散。     

Cu~(2+)助芬顿法处理高浓度邻苯二甲酸二甲酯废水

Cu2+可以与H2O2发生类Fenton反应,用Fenton法处理同时含有难降解有机物和Cu2+的工业废水时,Cu2+对于Fenton氧化难降解有机物的反应具有促进作用。本实验在高浓度邻苯二甲酸二甲酯(DMP)和Cu2+组成的模拟工业废水中投加Fenton试剂(Fe2++H2O2),利用Cu2+辅助Fe2+催化Fenton反应氧化难降解有机物。通过正交实验,优选反应条件,并进行单因素实验,分析不同Cu2+浓度、初始H2O2浓度、H2O2∶Fe2+(摩尔比)、pH及温度对DMP去除率的影响,以确定最佳的反应条件,并对反应机理进行了初步探讨。当Cu2+浓度为10 mg/L、DMP浓度为250 mg/L、初始H2O2的浓度为499.5 mg/L、H2O2∶Fe2+的摩尔比为4∶1、温度为20℃时,DMP的去除率最高可达到98.67%。本研究为类芬顿法处理难降解有机物和重金属离子共存的复杂工业废水奠定了基础。     

超声波/零价铁降解对氯苯胺性能及机理研究

在超声波/零价铁体系中考察了溶液初始pH值、浓度对对氯苯胺降解的影响.在pH值为3～11范围内最佳条件为pH=9;初始浓度为0.1、0.2和0.4 mmol/L时的降解率(180 min)分别为83.2%、63.5%和36.1%.对氯苯胺在单纯铁粉、单纯超声波和超声波/零价铁3种体系中降解符合拟一级反应动力学规律,速率常数分别为6.83×10-4、3.95×10-3和1.01×10-2 min-1,增强因子为218%,表明铁粉与超声波对对氯苯胺降解有明显的协同效应.在体系中加入自由基捕捉剂正丁醇能抑制对氯苯胺的降解,证实对氯苯胺降解主要是依靠羟基自由基的氧化作用.     

Residues of chlorpyrifos‐methyl in balsam fir foliage,forest litter,soil, stream water,sediment and fish tissue after double aerial applications of Reldan®

Abstract

Chlorpyrifos‐methyl was applied twice at 70 g A.I./ha by means of a fixed‐wing aircraft to a mixed coniferous forest near Allardville, New Brunswick. Residue in balsam fir foliage was highest (1 ppm wet wt) 1 hr after spraying and rapidly declined to about 30% within 1 day, but persisted at a very low level (0.03 ppm wet wt) for 125 days. Current year's foliage contained a higher level of residue than old foliage. Chlorpyrifos‐methyl persisted longer in forest litter than in soil. After 125 days, trace amounts (< 6 ppb wet wt) were still found in litter but were not detected in soil. In stream water the residue dissipated very rapidly; more than 90% disappeared 3 hours after the second application and were not detected after 4 days. Low‐level residue (< 0.1 ppm wet wt) was present in the sediment and persisted for 10 days. Although brook trout and slimy sculpin captured in the stream within 3 days of the second application contained residues (< 0.05 ppm fresh wt) none were detected in any fish captured, 9 and 47 days later.     

Field dissipation of oxyfluorfen in onion and its dynamics in soil under Indian tropical conditions

Oxyfluorfen, a diphenyl-ether herbicide is being used to control annual and perennial broad-leaved weeds and sedges in a variety of field crops including onion. The present study was aimed to investigate the dynamics and field persistence of oxyfluorfen in onion plant, bulb and soil under Indian tropical conditions. Application of four rates of oxyfluorfen viz., 200, 250, 300 and 400 g AI ha^?1 as pre-emergence gave good weed control in field experiment with onion. The oxyfluorfen residue dissipated faster in plant than in soil respectively, with a mean half-life of 6.1 and 11.2 days. Dissipation followed first-order kinetics. In laboratory column leaching experiments, 17 percent of the applied oxyfluorfen was recovered from the soil and indicates its solubility in water and mobility in sandy clay loam soil was low. A sorption study revealed that the adsorption of oxyfluorfen to the soil was highly influenced by the soil organic carbon with the K_oc value of 5450. The study concludes that the dissipation of oxyfluorfen in soil and onion was dependent on the physico-chemical properties of the soil and environmental conditions.     

碘掺杂TiO2可见光光催化性能研究

在低于100℃温度条件下,采用溶胶-凝胶法以钛酸正丁酯为钛源,碘酸钾为碘源,制备了I掺杂纳米TiO2催化剂(I-TiO2),运用X-射线衍射(XRD)、透射电镜(TEM)及X-射线光电子能谱(XPS)等对催化剂进行表征,结果表明,TiO2及I-TiO2催化剂均为锐钛矿,I吸附并包裹在TiO2表面或以间隙进入的形式存在,并未进入TiO2晶格。通过在可见光照射下(λ>420 nm)以罗丹明B(Rhodamine B,RhB)的光催化降解为探针反应研究了在不同条件下制备催化剂的催化性能,结果表明,掺杂比为nI:nTi=0.05∶1,焙烧温度为400℃,降解介质条件pH=7时,I-TiO2光催化活性明显优于未掺杂的TiO2。光催化降解过程通过红外光谱(IR),总有机碳(TOC)跟踪测定,比较了TiO2掺杂前后降解RhB和对氯苯酚(4-CP)的光催化特性差异;同时采用苯甲酸荧光光度法跟踪测定体系中的氧化物种,表明在可见光下,I-TiO2光催化体系中产生.OH高活性氧化物种从而氧化降解目标化合物。     

Fate in soil of 14C-sulfadiazine residues contained in the manure of young pigs treated with a veterinary antibiotic

The fate of ¹⁴C-labeled sulfadiazine (¹⁴C-SDZ) residues was studied in time-course experiments for 218 days of incubation using two soils (A_p horizon of loamy sand, orthic luvisol; A_p horizon of silt loam, cambisol) amended with fresh and aged (6 months) ¹⁴C-manure [40 g kg^?1 of soil; 6.36 mg of sulfadiazine (SDZ) equivalents per kg of soil], which was derived from two shoats treated with ¹⁴C-SDZ. Mineralization of ¹⁴C-SDZ residues was below 2% after 218 days depending little on soil type. Portions of extractable ¹⁴C (ethanol-water, 9:1, v/v) decreased with time to 4–13% after 218 days of incubation with fresh and aged ¹⁴C-manure and both soils. Non-extractable residues were the main route of the fate of the ¹⁴C-SDZ residues (above 90% of total recovered ¹⁴C after 218 days). These residues were high immediately after amendment depending on soil type and aging of the ¹⁴C-manure, and were stable and not remobilized throughout 218 days of incubation. Bioavailable portions (extraction using CaCl₂ solution) also decreased with increasing incubation period (5–7% after 218 days). Due to thin-layer chromatography (TLC), 500 μg of ¹⁴C-SDZ per kg soil were found in the ethanol-water extracts immediately after amendment with fresh ¹⁴C-manure, and about 50 μg kg^?1 after 218 days. Bioavailable ¹⁴C-SDZ portions present in the CaCl₂ extracts were about 350 μg kg^?1 with amendment. Higher concentrations were initially detected with aged ¹⁴C-manure (ethanol-water extracts: 1,920 μg kg^?1; CaCl₂ extracts: 1,020 μg kg^?1), probably due to release of ¹⁴C-SDZ from bound forms during storage. Consistent results were obtained by extraction of the ¹⁴C-manure-soil samples with ethyl acetate; portions of N-acetylated SDZ were additionally determined. All soluble ¹⁴C-SDZ residues contained in ¹⁴C-manure contributed to the formation of non-extractable residues; a tendency for persistence or accumulation was not observed. SDZ's non-extractable soil residues were associated with the soluble HCl, fulvic acids and humic acids fractions, and the insoluble humin fraction. The majority of the non-extractable residues appeared to be due to stable covalent binding to soil organic matter.