Neutral Herbicides Research Articles

Distributions of OCPs and CUPs in the Sediment and Surface Water Close to a Drinking Water Reservoir in Northeastern China

In the Chinese city of Wuchang, Heilongjiang Province, a survey was conducted to track the concentrations and distributions of several organic pollutants near drinking water reservoirs, such as conventional organochlorine pesticides (OCPs) and currently in use pesticides (CUPs), including organophosphorus pesticides (OPPs) and neutral herbicides (NHs). From October 2007 to July 2008, a total of 32 pairs of water and sediment samples were gathered and examined. The results showed that the total concentrations of OCPs, OPPs, and NHs in the sediments were 0.42–7.8 ng/dm3 below the detection limit of these pollutants in sediments. The total concentration of OPPs in the water varied from the LoD to 180 ng/dm3 while NHs were 6.3 to 740 ng/dm3. While the CUP concentrations changed significantly throughout the year, the OCP concentrations were less impacted by seasonal fluctuations, indicating no recent introduction of these chemicals. The use of pesticides on crops in the primarily agricultural area was the main factor contributing to higher concentrations of CUPs during the summer.

Relationship between biochars' porosity and adsorption of three neutral herbicides from water.

The porous biochars have exhibited good adsorption to many organic pollutants, but the relationship between biochars' porosity and their adsorption capacity is not clear at the moment. In this work, six biochars were produced from different feedstocks and under different pyrolysis conditions, and used for adsorption of three neutral herbicides from water. The results demonstrated that the adsorption capacity was dominated by the mesopore (1.7-50 nm) area of biochars, instead of their total surface area, according to the analysis of surface area-normalized adsorption data with both Langmuir model and a mixed adsorption and partition model. The results implied the inaccessibility of most micropores in biochars to the organic molecules with nano-scale molecular dimension, and alkalis in feedstock and an oxygen-containing atmosphere in heat treatment for producing biochars would favor the development of mesopores.

Examining impacts of current-use pesticides in Southern Ontario using in situ exposures of the amphipod Hyalella azteca.

In situ exposures with Hyalella azteca were used to assess impacts of current-use pesticides in Southern Ontario, Canada. Exposures were conducted over 2 growing seasons within areas of high pesticide use: 1 site on Prudhomme Creek and 3 sites on Twenty Mile Creek. Three sites on Spencer Creek, an area of low pesticide use, were added in the second season. Surface water samples were collected every 2 wk to 3 wk and analyzed for a suite of pesticides. Hyalella were exposed in situ for 1 wk every 4 wk to 6 wk, and survival and acetylcholinesterase (AChE) activity were measured. Pesticides in surface waters reflected seasonal use patterns: lower concentrations in spring and fall and higher concentrations during summer months. Organophosphate insecticides (chlorpyrifos, azinphos methyl, diazinon) and acid herbicides (2,4-dichlorophenoxyacetic acid [2,4-D], mecoprop) were routinely detected in Prudhomme Creek, whereas neutral herbicides (atrazine, metolachlor) dominated the pesticide signature of Twenty Mile Creek. Spencer Creek contained fewer pesticides, which were measured at lower concentrations. In situ effects also followed seasonal patterns: higher survival and AChE activity in spring and fall, and lower survival and AChE activity during summer months. The highest toxicity was observed at Prudhomme Creek and was primarily associated with organophosphates. The present study demonstrated that current-use pesticides in Southern Ontario were linked to in situ effects and identified sites of concern requiring further investigation.

Assessment of three vermicomposts as organic amendments used to enhance diuron sorption in soils with low organic carbon content

SummaryVermicomposts from the wine and distillery industry containing spent grape marc (V1), biosolid vinasse (V2) and alperujo (V3) from the olive‐oil industry were investigated as organic amendments to a sandy and a clay soil with low organic carbon (OC) contents (≤1%). The sorption‐desorption process was studied in batch experiments using diuron as a non‐ionic herbicide model. The effect of soil and vermicompost characteristics, the solution's ionic strength and incubation time of amended soils on the sorption process was studied. The addition of vermicompost changed soil properties and enhanced sorption capacity by two‐ to four‐fold. The Koc variability showed that exogenous OC composition influenced diuron sorption. Vermicompost V1, which had the largest OC and lignin content, recorded the largest sorption increment. Vermicompost V3, which had the greatest dissolved organic carbon content and a high degree of humification, made the smallest contribution to sorption. Sorption was also dependent on extraneous calcium in the solution. The incubation of amended soils reduced diuron sorption efficiency except with V3. Pyrolysis‐gas chromatography (Py‐GC) analysis was a useful tool to characterize the vermicomposts and to understand the variation of diuron sorption constants after vermicompost incubation. This research encourages the use of vermicompost from agro‐industrial wastes as a sustainable means to minimize the side effects of neutral herbicides.

Atmospheric concentrations and gas-particle partitions of pesticides: Comparisons between measured and gas-particle partitioning models from source and receptor sites

Atmospheric concentrations and gas-particles partition were measured for 83 pesticides including organochlorines (OCs), acid herbicides (AHs), neutral herbicides (NHs) and organophosphorus pesticides (OPs). Samples have been collected in June 2005 at two sites, located in Québec, named St. Anicet (agricultural area) and Bay St. François wetland (receptor site). The highest vapor concentration was measured for metolachlor which was 23,600 pg m −3 and 12,200 pg m −3 at St. Anicet and Bay St. François (BSF), respectively. In the particulate phase, MCPA exhibited the highest level (323 pg m −3) at St. Anicet. Gas-particle partitions (GPPs) were also investigated and it was expressed as a function of the fraction of chemical in the particulate phase ( ϕ). The highest average of ϕ was observed for the AHs which were MCPB (75%) and MCPA (50%) at BSF and St. Anicet, respectively. Likewise, the GPPs were estimated by several models, namely Junge–Pankow model, K OA model, and polyparameter linear free energy relationships (ppLFERs). The estimated GPPs were compared to the observed ones and data showed a better correlation at BSF (receptor site) than that at St. Anicet. This suggests a kinetic effect on the GPPs of chemicals.

Pesticides in the Atmosphere Across Canadian Agricultural Regions

The Canadian Atmospheric Network for Currently Used Pesticides (CANCUP) was the first comprehensive, nationwide air surveillance study of pesticides in Canada. This paper presentsthe atmospheric occurrence and distribution of pesticides including organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), acid herbicides (AHs), and neutral herbicides (NHs) during the spring to summer of 2004 and 2005 across agricultural regions in Canada. Atmospheric concentrations of pesticides varied within years and time periods, and regional characteristics were observed including the following: (i) highest air concentrations of several herbicides (e.g., mecoprop, triallate, and ethalfluralin) were found at Bratt's Lake, SK, a site in the Canadian Prairies; (ii) the west-coast site at Abbotsford, BC, had the maximum concentrations of diazinon; (iii) the fruit and vegetable growing region in Vineland, ON, showed highest levels for several insecticides including chlorpyrifos, endosulfan, and azinphos-methyl; (iv) high concentrations of atrazine and metolachlor were measured at St. Anicet, QC, a corn-growing region; (v) the Kensington site in PEI, Canada's largest potato-producing province, exhibited highest level of dimethoate. Analysis of particle- and gas-phase fractions of air samples revealed that most pesticides including OCPs, OPPs, and NHs exist mainly in the gas phase, while AHs exhibit more diversity in particle-gas partitioning behavior. This study also demonstrated that stirred up soil dust does not account for pesticides that are detected in the particle phase. The estimated dry and wet deposition fluxes indicate considerable atmospheric inputs for some current-use pesticides (CUPs). This data set represents the first measurements for many pesticides in the atmosphere, precipitation, and soil for given agricultural regions across Canada.

Environmentally Friendly Slow Release Formulations of Alachlor Based on Clay-Phosphatidylcholine

A new clay-liposome complex was developed for reducing leaching of herbicides and contamination of groundwater. The liposomes were composed of the neutral and Environmental Protection Agency approved phospholipid phosphatidylcholine (PC). Adsorption of PC liposomes on the clay mineral montmorillonite could exceed the cation exchange capacity of the clay, and was well simulated by the Langmuir equation. X-ray diffraction results for 6 mM PC and 1.6 g/L clay (3 day incubation) yielded a basal spacing of 7.49 nm, which was interpreted as the formation of a supported planar bilayer on montmorillonite platelets. Fluorescence methods demonstrated structural changes which reflected adsorption of PC followed by loss of vesicle integrity as measured by the penetration of dithionite into the internal monolayer of fluorescently labeled liposomes, resulting in a decrease in fluorescence intensity to 18% of initial after 4 h. Energy transfer was demonstrated after 1 h from labeled liposomes to montmorillonite labeled by an acceptor. The neutral herbicide alachlor adsorbed on the liposome-clay complex, yielding a formulation of up to 40% active ingredient, and 1.6-fold reduction in herbicide release in comparison to the commercial formulation. Hence, the PC-montmorillonite complex can form a basis for environmentally friendly formulations of herbicides, which would yield reduced leaching.

Orthogonal array optimization of a multiresidue method for cereal herbicides in soils

Nearly 40 herbicides, commonly used for barley, were selected for analysis in soils of this crop. The primary objective was to develop a multiresidue method taking into account that herbicides belonged to different chemical families. Some preliminary experiments with different solvents in combination with water, acetic acid and ammonium hydroxide, were developed in order to design the predefined region covered by the orthogonal array design used for optimization. Final extracts were splitted in two aliquots, one of them was directly analyzed by gas chromatography–mass spectrometry (GC–MS), and the other one was derivatized before the acidic analyte analysis. Principal component analysis (PCA) was applied to the data generated in the preliminary experiments, in order to clarify the relationships among the different variables studied. According to the obtained results, the following variables were selected: solvent type and ratio, amount of acetic acid and extraction time. The statistical analysis revealed that all the factors were significant being the most important, the type and ratio of solvent for basic and neutral herbicides and the acetic acid percentage for acid herbicides. The final optimized method consisted of shaking previously wet soil samples for 30 min with 30 ml of acetone acidified with 1% acetic acid. Method validation was evaluated following the EU guidelines.

Simultaneous determination of phenyl- and sulfonylurea herbicides in water by solid-phase extraction and liquid chromatography with UV diode array or mass spectrometric detection

A method for the simultaneous determination of 10 sulfonyl- and phenylurea herbicides (chlorsulfuron, triasulfuron, fenuron, monuron, fluometuron, chlorotoluron, isoproturon, diuron, metobromuron, linuron) and one of their most common degradation products (3-chloro-4-methyl-phenyl urea) has been developed. Liquid chromatography with diode array UV detection (LC–DAD UV) and positive ion electrospray mass spectrometry (LC–ESI–MS) were used for the separation, identification and quantification of these analytes. In the LC–DAD UV method, chromatographic separation was achieved in about 27 min; however, analysis time can be reduced to less than 13 min when LC–MS is applied, since no complete separation of the chromatographic peaks was required. A preconcentration step based on solid-phase extraction was applied for the simultaneous extraction of sulfonylureas (acidic in nature) and phenylureas (neutral compounds) from water samples. Different types of sorbents were evaluated: silica-based C 18 and two polymeric sorbents, Oasis HLB and LiChrolut EN. The best results were obtained with Oasis HLB, a co-polymer of poly(divinylbenzene-co- N-vinylpyrrolidone). Other parameters, such as the elution solvent and sample volume, were optimised in order to maximise extraction efficiency; the recoveries obtained varied between 70 and 95% for the acidic and neutral herbicides extracted jointly without acidification of the sample. Both procedures, SPE LC–DAD UV and SPE–LC–MS, were applied to spiked river waters and were compared in terms of selectivity and sensitivity. The detection limits obtained in river water samples were below 50 ng L −1 for both procedures.

Variability of herbicide losses from 13 fields to surface water within a small catchment after a controlled herbicide application.

Diffuse losses from agricultural fields are a major input source for herbicides in surface waters. In this and in a companion paper, we present the results of a comprehensive field study aimed at assessing the overall loss dynamics of three model herbicides (i.e., atrazine, dimethenamid, and metolachlor) from a small agricultural catchment (2.1 km2) and evaluating the relative contributions of various fields having different soil and topographical characteristics. An identical mixture of the three model herbicides as well as an additional pesticide for identification of a given field were applied within 12 h on 13 cornfields (total area approximately 12 ha), thus ensuring that the herbicides were exposed to identical meteorological conditions. After the simultaneous application, the concentrations of the compounds were monitored in the soils and at the outlets of three subcatchments containing between 4 and 5 cornfields each. Particular emphasis was placed on the two rain events that led to the major losses of the herbicides. The rank orders of herbicide dissipation in the soils and of the compound-specific mobilization into runoff were the same in all three subcatchments and were independent of the field characteristics. In contrast, the field properties caused the relative losses from two subcatchments to differ by up to a factor of 56 during the most important event, whereas compound-specific differences of the three neutral herbicides caused the losses to vary only by a factor of 2 during the same event. The enormous spatial variability was mainly caused by factors influencing the fraction of rain that was lost to surface water by fast transport mechanisms. Thus, the key factors determining the spatially variable herbicide losses were the permeability of the soils, the topography, and the location of subsurface drainage systems. These results illustrate the large potential to reduce herbicide losses by avoiding application on risk areas.

Determination of rice herbicides, their transformation products and clofibric acid using on-line solid-phase extraction followed by liquid chromatography with diode array and atmospheric pressure chemical ionization mass spectrometric detection

A simultaneous method for the trace determination of acidic, neutral herbicides and their transformation products in estuarine waters has been developed through an on-line solid-phase extraction method followed by liquid chromatography with diode array and mass spectrometric detection. An atmospheric pressure chemical ionization (APCI) interface was used in the negative ionization mode after optimization of the main APCI parameters. Limits of detection ranged from 0.1 to 0.02 ng/ml for 50 ml of acidified estuarine waters preconcentrated into polymeric precolumns and using time-scheduled selected ion monitoring mode. Two degradation products of the acidic herbicides (4-chloro-2-methylphenol and 2,4-dichlorophenol) did not show good signal response using APCI-MS at the concentration studied due to the higher fragmentor voltage needed for their determination. For molinate and the major degradation product of propanil, 3,4-dichloroaniline, positive ion mode was needed for APCI-MS detection. The proposed method was applied to the determination of herbicides in drainage waters from rice fields of the Delta del Ebro (Spain). During the 3-month monitoring of the herbicides, 8-hydroxybentazone and 4-chloro-2-methylphenoxyacetic acid were successively found in those samples.

Use of solid phase extraction disks for the GC-MS analysis of acidic and neutral herbicides in drinking water

An analytical procedure was developed in which thirteen herbicides (10 acidic and 3 neutral compounds) may be extracted from drinking water samples using solid phase extraction disks and subsequently analyzed by gas chromatography-mass spectrometry. Using 8 replicate samples consisting of reagent water fortified with nanogram quantities of each herbicide, the average percent recoveries and method detection limits were determined for each analyte. The method was found to be suitable for the determination of individual herbicides in drinking water at concentrations of approximately 10 ng/L.

Micellar electrokinetic capillary chromatography with in situ charged micelles: 3. Evaluation of alkylglucoside surfactants as anionic butylboronate complexes.

This article represents an extension to a new approach introduced very recently by our laboratory for the control of the surface charge density as well as the hydrophobic character of micellar phases used in micellar electrokinetic capillary chromatography (MECC). The approach is based on the complexation of polyolic surfactants, e.g., alkylglucosides, with butylboronate to form in situ branched, anionic surfactants. The butylboronate can also incorporate into the micelle via its alkyl tail and acts as a "class I" organic additive that mainly modifies the micelle by decreasing the critical micellar concentration, i.e., increasing the hydrophobic character of the micelle, while exhibiting little influence on the aqueous phase. The net result is an in situ charged micellar entity whose hydrophobic character is dynamically altered. The alkylglucoside-butylboronate micellar phases yielded high separation efficiencies and proved useful in the separation of charged and neutral herbicides as well as the chiral separations of medicarpins and precursors, and dansylated D and L-amino acids in the presence of native or modified cyclodextrin chiral selectors.

Determination of MCPA, Bromoxynil, 2, 4-D, Trifluralin, Triallate, Picloram, and Diclofop-Methyl in Soil by GC-MS Using Selected Ion Monitoring

Abstract A double space extraction procedure was developed to simultaneously determine neutral herbicides (trifluralin, dlclofop- methyl, and triallate) and acid herbicides (MCPA, 2,4-D, bromoxynil, and picloram) in soil. The method uses capillary column gas chromatography (GC) and mass spectrometry (MS) detection with a high degree of confidence in the interpretation of herbicides in many soil types to the 0.003 ppm level. Detection limits at these low levels are possible because extracts can be concentrated by a factor of 50 with few coextractlve interferences evident in the chromatography. Recovery data are excellent for both groups of herbicides (81.5-97.8%, average); relative standard deviations vary from 15-23% because of a larger response variation using GC/MS detection.

Binding of Ionic and Neutral Herbicides by Soil Humic Acid

AbstractThe gel filtration method of Hummel and Dreyer has been used for the study of binding of bromacil (5‐bromo‐3‐sec‐butyl‐6‐methy‐luracil), diuron [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea], chlortoluron [3‐(3‐chloro‐4‐methylphenyl)‐1,1‐dimethylurea], simazine (2‐ chloro‐4,6‐bis‐ethylamino‐s‐triazine), glyphosate [N‐(phosphonomethyl) glycine], and diquat (1,1‐ethylene‐2,2‐bipyridylium ion) by humic acid. The chromatographic method was found germane for the study of the ionic, as well as the nonionic herbicides. The results expressed as the number of moles of herbicide complexed per unit weight humic acid indicated the utility and reliability of the procedure for the quantitative evaluation of binding. Valid quantitative data on the interaction of herbicides with humic acid would be indispensable for the assessment of these chemicals mobility and transport in soil and water environments.

Gas Chromatographic Determination of Trifluralin, Diallate, Triallate, Atrazine, Barban, Diclofop-Methyl, and Benzoylprop-Ethyl in Sediments at Parts Per Billion Levels

Abstract A sensitive gas chromatographic method was developed for the multiresidue determination of 7 neutral herbicides in sediment. The sediment sample was ultrasonically extracted 3 times with acetone. The extract was concentrated to about 50 mL and then partitioned with 2% KHCO3 and CH2C12. The organic phase was dried over anhydrous Na2So4. The concentrated extract was then cleaned up on a 10% deactivated Florisil column, and the herbicides were separated into 2 fractions. Further cleanup of these fractions was performed on activated Florisil columns. Electron capture detection was used for analysis except for atrazine which was analyzed by nitrogen-phosphorus detection. Recoveries of the herbicides from fortified sediment samples at 3 levels were generally better than 80%. The practical detection limit of this method was 1 ppb or 1 ng/g based on a 50 g sediment sample.

Determination of Trif luralin, Diallate, Triallate, Atrazine, Barban, Diclofop-Methyl, and Benzoylprop-Ethyl in Natural Waters at Parts per Trillion Levels

Abstract A sensitive multiresidue method is presented for the determination of 7 neutral herbicides in natural waters, with practical detection limits between 5 and 100 ng/L(ppt). The extraction was carried out at pH ≼1, using dichloromethane, so that acid-type herbicides can also be incorporated in the future. The entire cleanup procedure involves base partitioning, preliminary cleanup and fractionation on a 10% deactivated Florisil column, and final cleanup of the fractions on an activated Florisil column. However, the cleanup procedure is flexible enough to permit the analyst to use some or all of the cleanup steps, depending on the herbicide levels of interest. Recoveries of the 7 herbicides from distilled and natural water samples were between 82 and 104% at 2 fortification levels. Furthermore, this basic analytical scheme has been demonstrated, separately, to be effective in the determination of other neutral compounds such as PCBs, 18 organochlorine pesticides, and chlorobenzenes and thus has a potential to be developed into a multiclass, multiresidue method.