Adsorption Of Herbicides Research Articles

광산화 및 광촉매 공정에서 VOCs의 산화반응 속도 산출에 관한 연구

Adsorption of chloroacetanilide herbicide acetochlor, alachlor, metolachlor and propachlor on soils and soil components was determined, and the structural differences of these herbicides were used to explain the order of sorptivity. Adsorption isotherms for all herbicide-soil combinations conformed to the Freundlich equation, and Ki increased with increasing soil organic carbon content. Kd on soil humic acid was greater than that on clay, but association of humic acid with clay reduced the overall adsorption. On all soils and soil humic acids, herbicide adsorption decreased in the order: metolachlor > acetochlor > propachlor > alachlor. On Ca(2+)-montmorrilonite, the order changed to metolachlor > acetochlor > alachlor > propachlor. FT-IR spectra of herbicide-clay or herbicide-humic acid-clay mixtures showed that H-bonding and charge transfer were the primary interaction pathways between these compounds and the surface of clay or humic acids. The different moieties attached to 2-chloro-acetanilide and their unique arrangement may have influenced the binding mechanisms and thus the sorptivity of these herbicides. This study indicates that the structural difference of pesticides in the same classes may be used as a molecular probe to obtain a better understanding of sorption mechanisms of pesticides on soil.

Adsorption of sugar beet herbicides to Finnish soils

Three sugar beet herbicides, ethofumesate, phenmedipham and metamitron, are currently used on conventional sugar beet cultivation, while new varieties of herbicide resistant (HR) sugar beet, tolerant of glyphosate or glufosinate-ammonium, are under field testing in Finland. Little knowledge has so far been available on the adsorption of these herbicides to Finnish soils. The adsorption of these five herbicides was studied using the batch equilibrium method in 21 soil samples collected from different depths. Soil properties like organic carbon content, texture, pH and partly the phosphorus and oxide content of the soils were tested against the adsorption coefficients of the herbicides. In general, the herbicides studied could be arranged according to their adsorption coefficients as follows: glyphosate > phenmedipham > ethofumesate ≈ glufosinate-ammonium > metamitron, metamitron meaning the highest risk of leaching. None of the measured soil parameters could alone explain the adsorption mechanism of these five herbicides. The results can be used in model assessments of risk for leaching to ground water resulting from weed control of sugar beet in Finland.

Infiltration and adsorption of dissolved atrazine and atrazine metabolites in buffalograss filter strips.

Vegetated filter strips (VFS) potentially reduce the off-site movement of herbicides from adjacent agricultural fields by increasing herbicide mass infiltrated (Minf) and mass adsorbed (Mas) compared with bare field soil. However, there are conflicting reports in the literature concerning the contribution of Mas to the VFS herbicide trapping efficiency (TE). Moreover, no study has evaluated TE among atrazine (6-chloro-N-ethyl-N'-isopropyl-[1,3,5]triazine-2,4-diamine) and atrazine metabolites. This study was conducted to compare TE, Minf, and Mas among atrazine, diaminoatrazine (DA, 6-chloro[1,3,5]triazine-2,4-diamine), deisopropylatrazine (DIA, 6-chloro-N-ethyl-[1,3,5]triazine-2,4-diamine), desethylatrazine (DEA, 6-chloro-N-isopropyl-[1,3,5]triazine-2,4-diamine), and hydroxyatrazine (HA, 6-hydroxy-N-ethyl-N'-isopropyl-[1,3,5]triazine-2,4-diamine) in a buffalograss VFS. Runoff was applied as a point source upslope of a 1- x 3-m microwatershed plot at a rate of 750 L h(-1). The point source was fortified at 0.1 microg mL(-1) atrazine, DA, DIA, DEA, and HA. After crossing the length of the plot, water samples were collected at 5-min intervals. Water samples were extracted by solid phase extraction and analyzed by high performance liquid chromatography (HPLC) photodiode array detection. During the 60-min simulation, TE was significantly greater for atrazine (22.2%) compared with atrazine metabolites (19.0%). Approximately 67 and 33% of the TE was attributed to Minf and Mas, respectively. These results demonstrate that herbicide adsorption to the VFS grass, grass thatch, and/or soil surface is an important retention mechanism, especially under saturated conditions. Values for Mas were significantly higher for atrazine compared with atrazine's metabolites. The Mas data indicate that atrazine was preferentially retained by the VFS grass, grass thatch, and/or soil surface compared with atrazine's metabolites.

Activated carbon adsorption of chloroacetanilide herbicides and their degradation products from surface water supplies

A recent (1995–2001) 175-site surface drinking water monitoring programme in the United States showed that one community water system (Nashville, Illinois) was particularly successful at removing chloroacetanilide herbicides and their degradation products from source water. Nashville adds powdered activated carbon (PAC) just prior to a clarifier in which settled solids are recirculated, increasing the PAC residence time. We conducted bench-scale studies to quantify the effects of PAC dose and contact time on removal efficiency. Results indicate that 90% of the parent herbicides and 40–45% of the acetanilide degradation products are removed for a contact time of 60 min and a PAC dose of 20 mg/l, from Nashville, IL, source water. Removal of these compounds by the same PAC dose and contact time was even higher in three other US water sources (Idaho, Kansas, Missouri) and a European (Dutch) water source, generally 60–80% for the degradation products and over 95% for the parent compounds. Removal percentages substantially increased with higher PAC dose and contact time, fell slightly with decreasing pH or higher NOM, but remained constant when the inlet concentration was raised from 2 to 10 µg/l.

Soluble and Solid Organic Matter Effects on Atrazine Adsorption in Cultivated Soils

Soil organic matter can be divided into solid (SOM) and water-dissolved (DOM) fractions; both of which can associate with herbicides. The objective was to examine the effects of DOM in applied solutions on atrazine adsorption in soil containing various SOM contents. A sandy loam with low (0.14%, Soil L), medium (1.2%, Soil M), or high (6.7%, Soil H) total organic matter, and artificial soil (Soil A) with no organic matter were used. These soils were treated with several different atrazine concentrations, dried, and extracted with water; the DOM concentrations in these extracts were 0, 10.1, 41.1, and 156.5 mg L−1, respectively. These extracts and the untreated soils were used in batch experiment. The distribution coefficients (Kd) for atrazine of Soils L, M, and H under mixing with Soil A extract were 0.19, 0.52, 2.51, respectively, indicating that the higher the SOM content, the higher the atrazine affinity to the soil solid phase. The effects of the DOM concentration on atrazine adsorption were estimated from the ratios (Rd) between the Kd for applied solution with no DOM and those for applied solutions containing DOM. Rd > 1 indicates that the DOM decreases the herbicide adsorption. The Rd values for Soils L, M, and H, each soil mixed with its extract, were 2.68, 1.93, and 1.07, respectively. In contrast, in the case where the soil was mixed with a solution that contained a higher DOM concentration than the soil extract, an increase in the DOM concentration in the applied solution decreased the Rd value. This was probably because of adsorption of DOM-atrazine complexes on the SOM.

The Adsorption of Herbicides and Pesticides on Clay Minerals and Soils. Part 2. Atrazine

The adsorption of atrazine and two model compounds,2-chloropyrimidine and 3-chloropyridine on clay minerals(bentonite, montmorillonite and kaolinite), organic matter (humic acid) and soil (with and without organic matter) has beenstudied using FT-infrared spectroscopy (IR), thermogravimetric analysis (TGA), high pressureliquid chromatography (HPLC) and X-ray diffraction (XRD).3-Chloropyridine, 2-chloropyrimidine and atrazine were adsorbedthrough hydrogen bonding on bentonite, montmorillonite, humic acid and soil. In addition tohydrogen bonding, protonation of 3-chloropyridine and atrazine was also observed.In the adsorption of 2-chloropyrimidine on bentonite and montmorillonitean ion exchange mechanism also occurred. No adsorption of 3-chloropyridine or 2-chloropyrimidine wasobserved on the kaolinite clay mineral.Both the clay minerals and organic matter of soil contribute tothe adsorption of organic compounds on soil but the clay minerals bentonite and montmorilloniteplay a major role in their adsorption on soil.

Influence of herbicide structure, clay acidity, and humic acid coating on acetanilide herbicide adsorption on homoionic clays.

Adsorption of chloroacetanilide herbicides on homoionic montmorillonite was studied by coupling batch equilibration and FT-IR analysis. Adsorption decreased in the order metolachlor > acetochlor > alachlor > propachlor on Ca(2+)- or Mg(2+)-saturated clays and in the order metolachlor > alachlor > acetachlor > propachlor on Al(3+)- or Fe(3+)-saturated clays. FT-IR spectra showed that the carbonyl group of the herbicide molecule was involved in bonding. For the same herbicide, adsorption of alachlor, acetachlor, and metolachlor on clay followed the order Ca(2+) approximately Mg(2+) < Al(3+) < or = Fe(3+), which coincided with the increasing acidity of homoionic clays. Adsorption of propachlor, however, showed an opposite dependence, suggesting a different governing interaction. In clay and humic acid mixtures, herbicide adsorption was less than that expected from independent additive adsorption by the individual constituents, and the deviation was dependent on the clay-to-humic acid ratio, with the greatest deviation consistently occurring at a 60:40 clay-to-humic acid ratio.

Adsorption of Dinitrophenol Herbicides From Water by Montmorillonites

AbstractThe adsorption of two dinitrophenol herbicides, 4,6-dinitro-o-cresol (DNOC) and 4,6-dinitro-o-sec-butyl phenol (dinoseb), by two reference smectite clays (SWy-2 and SAz-1) was evaluated using a combination of sorption isotherms, Fourier transformation infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and molecular dynamic simulations. Clays were subject to saturation with various cations, and charge reduction. The DNOC adsorption decreased with increasing pH indicating that DNOC was primarily adsorbed as the neutral species. The FTIR spectra of DNOC-clay films showed that DNOC molecules are oriented parallel to the clay surface. Interlayer cations have a strong effect on adsorption depending largely on their hydration energies. Weakly hydrated cations, e.g. K+ and Cs+, resulted in greater sorption compared to more strongly hydrated cations such as Na+ or Ca2+. Lower hydration favors direct interactions of exchangeable cations with -NO2 groups of DNOC and manifests optimal interlayer spacings for adsorption. In the presence of sorbed DNOC, an interlayer spacing for K-SWy-2 of between 12 and 12.5 Å was maintained regardless of the presence of water. This d-spacing allowed DNOC molecules to interact simultaneously with the opposing clay layers thus minimizing contact of DNOC with water. The charge density of clays also affected sorption by controlling the size of adsorption domains. Accordingly, DNOC adsorption by low-charge clay (K-SWy-2) was much higher than by high-charge clay (K-SAz-1) and Li-charge reduction greatly enhanced dinoseb adsorption by K-SAz-1. Steric constraints were also evident from the observation that adsorption of DNOC, which contains a methyl substituent, was much greater than dinoseb, which contains a bulkier isobutyl group. Adsorption of DNOC by K-SAz-1 was not affected in the presence of dinoseb, whereas dinoseb adsorption was greatly reduced in the presence of DNOC.

The Adsorption of Herbicides and Pesticides on Clay Minerals and Soils. Part 1. Isoproturon

The adsorption of isoproturon and two model compounds, N,N-dimethylurea and4-isopropylaniline, on clay minerals (bentonite,montmorillonite and kaolinite), organic matter (humic acid) and soil (with and without organic matter) has been studied using FT-infrared spectroscopy (IR), thermogravimetric analysis (TGA), high pressure liquid chromatography (HPLC) and X-ray diffraction (XRD).N,N-dimethylurea interacted with bentonite and montmorillonite by the coordination of the carbonyl group, directly or indirectly through water molecules, with exchangeable cations. Adsorption on humic acid was due to hydrogen bonding with the active sites of the adsorbent. The amino group ofN,N-dimethylurea appears tobe relatively inactive during adsorption. The mechanisms involved in the adsorption of 4-isopropylaniline were hydrogen bonding and protonation. No adsorption of 4-isopropylaniline was observed on kaolinite. The investigation of isoproturon suggested that both the carbonyl and amino groups of isoproturon were involved in interactions with the active sites of the adsorbents. Both the clay minerals and organic matter of soil contribute to the adsorption of organic compounds on soil but the clay minerals bentonite and montmorillonite play a major role in their adsorption on soil.

Effect of Soil Characteristics on Atrazine and Linuron Adsorption

除草剤の吸着に影響する土壌の理化学的性質を明らかにするため,「吸着割合 (AR)」を用いた. ARの計算式は以下のとおりである; AR (%)=(土壌1kgに対する除草剤の吸着量)/(土壌1kgに対する除草剤の初期投入量)×100. 除草剤の初期投入量を5水準設けてARを分布 (DAR) にまとめ, アトラジンとリニュロンの吸着のしやすさと吸着容量を日本の土壌42点について評価した. アトラジンとリニュロンのDARを多変量解析すると, 双方とも土壌を6グループに分類できた. 各グループについて理化学的性質の影響を検討した結果, 双方とも有機物因子 (OM) の寄与が最も高かった. しかし, 理化学的性質の影響がアトラジンとリニュロンの場合で異なり, 土壌の分類パターンは異なっていた. 塩基飽和度が高い土壌では, アトラジンの初期投入量が多くなるにつれてARが急激に減少した. そのような土壌ではアトラジンの吸着容量が少ないことをDARで示せた.

Adsorption of imidazolinone herbicides on smectite-humic acid and smectite-ferrihydrite associations.

Adsorption of imazapyr (IMZ), imazethapyr (IMZT), and imazaquin (IMZQ) was studied on two smectite-humic acid and two smectite-ferrihydrite binary systems prepared by treating a Wyoming smectite with a humic acid extracted from soil (4 and 8% w/w of the smectite) and with just-precipitated synthetic ferrihydrite (8 and 16% w/w of the smectite). Adsorption of the three herbicides on the smectite was not measurable at pH >4.5, presumably because of negative charges on the surface of the smectite. Adsorption on the smectite-humic acid systems was also not measurable, presumably because of negative charges on the surface, despite the high affinity of the three herbicides for humic acid, the adsorption order of which was IMZ < IMZT << IMZQ. Adsorption decreased in the order IMZ < IMZT < IMZQ on the smectite-ferrihydrite systems and IMZQ < IMZT < IMZ on ferrihydrite, although here the differences were small. These results show that even though pure smectite cannot adsorb herbicides, it modifies the adsorption capacity of ferrihydrite. The mutual interaction of active phases such as humic acid, ferrihydrite, and smectite alters the characteristics of the resulting surface and hence the adsorption process. Investigations of herbicide adsorption have been seen to produce more reliable results if conducted on polyphasic systems rather than on single soil components.

Determination of linuron in soil by stripping voltammetry with a carbon fiber microelectrode

A carbon fiber microelectrode was used for the electroanalytical determination of Linuron (LIN) in soil extracts. The microelectrode was subjected to an electrochemical pretreatment in order to improve the herbicide adsorption on the electrode surface. With this preconcentration step, detection limits of 80 ng ml(-1) and determination limits of 260 ng ml(-1) were reached. Optimal conditions with respect to accumulation time and potential, scan rate and pH were established. The LIN was determined in a soil sample with the method proposed and the results found were comparable to those obtained by HPLC.

Improved efficiency of a divalent herbicide in the presence of clay, by addition of monovalent organocations

A severe decrease in efficacy of contact herbicides such as diquat (DQ) is caused by dust accumulated on the weeds. Such inactivation was explained by the adsorption of herbicides on dust particles. As a result of this inactivation, the rates of pesticides needed for efficient pest control are usually larger than the recommended rates, which increases the expenses, and pose a real danger to the environment and to the ecological balance of watersheds. We proposed the hypothesis that the addition of a monovalent organic cation to the herbicide formulation might improve the efficacy by lowering the amount of herbicide that is inactivated by the sorption to clay minerals. This hypothesis was tested on lettuce and pepper plants dusted with clay, using the commercial formulation of diquat (“Reglone”) and adding the monovalent organic cations acriflavin (AF) and mepiquat (MQ). We observed that a clay mineral with a high cation exchange capacity (CEC), such as montmorillonite, reduced the herbicidal activity of DQ more than a lower CEC clay as sepiolite. However, addition of 5–20 mM concentrations of AF or MQ may overcome the influences of a clay dust on the activity of a cationic herbicide. Such addition allowed the obtainment of good herbicidal results with less than 1/3 of the normal used amount of herbicide. The results of our research point out to a mechanism that may lower the needed doses of contact herbicides, due to a competitive adsorption on the clay–dust particles between the pesticide and monovalent organic cations that leaves more herbicide available to act on the weed.

Organo-clay formulations of pesticides: reduced leaching and photodegradation

Adsorption of organic cations on several clay minerals is reviewed with an emphasis on the effect of ionic strength and modeling. The clay exchanged with suitable organic cations forms a basis for ecologically acceptable formulations of herbicides with reduced leaching, ground water contamination and enhanced weed control efficacy. Incomplete neutralization of the clay surface charge by an organic cation may be advantageous in achieving maximal adsorption of hydrophobic herbicides. One conclusion from these studies is that optimization of clay-based herbicide formulations requires a selection of structurally compatible organic cations preadsorbed on the clay at optimal coverage. New experimental results are presented for alachlor formulations, which significantly reduce herbicide leaching under conditions of heavy irrigation. We were able to demonstrate that organo-clay formulations of alachlor and metolachlor can increase crop yields in a 1-year field experiment. The photostabilization of pesticides is reviewed and improved organo-clay formulations of the herbicides trifluralin and norflurazon are described. A pillared clay, nanocomposite micro- and/or meso porous material, was effective in reducing leaching and in conferring photostabilization, without added organic cations.

Clay-based formulations of metolachlor with reduced leaching

The current research in herbicide application aims to develop formulations that reduce leaching of the herbicide to deep layers of the soil and to concentrate its biological activity at the top layers. Adsorption of metolachlor on clay minerals, their organic derivatives or pillared forms provides the best possibility to develop slow-release formulations. Metolachlor is a selective pre-emergence herbicide widely used in irrigated crops to control annual weeds. It is adsorbed by bentonites and montmorillonites, but the amount adsorbed strongly depends on the type of bentonite and possible pretreatment reactions. Wyoming bentonites adsorbed considerable amounts of metolachlor but other bentonites did not bind this herbicide. An acid-activated pillared montmorillonite was also an effective adsorbent of metolachlor. Modification of this sample by preadsorbing different amounts of benzyl trimethylammonium ions did not influence the level of herbicide adsorption. The biological efficiency of the formulations was tested with bioassay soil columns. Slow-release formulations could be prepared with raw bentonites and the acid-activated pillared montmorillonite. A formulation, prepared by adsorbing metolachlor from aqueous solution on the acid-activated pillared montmorillonite, showed high herbicide activity at the top 10 cm, and did not diffuse significantly to greater depths. This formulation should allow a better weed control than the commercial formulations.

Entrapping pesticides by coagulating smectites

Highly delaminated montmorillonite (from Wyoming) with a high specific surface area when dispersed in water was used as an adsorbent of the hydrophobic herbicide metolachlor. The montmorillonite was coagulated with Na +, Ca 2+, Al 3+ and benzyl trimethylammonium ions. Ca 2+ and Al 3+ screened the surface charges and the adsorption of metolachlor was strongly enhanced by the interaction of metolachlor with the hydrophobic siloxane oxygen atoms and the water molecules of the hydration shell of the interlayer cations. With increasing salt concentration the mechanism changed from a cooperative adsorption process on a heterogeneous surface (S-type isotherm) to adsorption on a homogeneous surface (L-type). Coagulation with Ca 2+ and Al 3+ increased the amounts of metolachlor adsorbed from 14–41% (Na +) to 57–86% (Ca 2+) and 67–91% (Al 3+). The light microscopic images revealed that increasing amounts of metolachlor changed the band-type network into spherical “potato-like” aggregates. The enhanced herbicide adsorption hydrophobized the particles that crowded together to form spherical aggregates. Entrapping the herbicide molecules in clay mineral aggregates—either band-type networks or spherical aggregates—offers a useful tool in creating leaching-resistant herbicide formulations.

Adsorption and desorption of imazosulfuron by soil.

Understanding and quantifying the adsorption and desorption of herbicides by soil is important for predicting their fate and transport in the environment. Here we report a study concerning the adsorption and desorption, by four different soils, of imazosulfuron, 1-(2-chloroimidazo[1,2-a]pyridin-3-ylsulfonyl)-3-(4, 6-dimethoxypyrimidin-2-yl)urea, a new sulfonylurea herbicide. Both phenomena are well-described by the Freundlich equation, which shows this herbicide to be little adsorbed by each of the four soils investigated. The Freundlich adsorption constants, K(f-ads), ranged from 1.46 to 3.02. Distribution coefficients between soil and water, Kd, measured on soils of different organic matter contents and pH values showed an important effect of these two parameters on imazosulfuron retention. The Freundlich desorption data indicated that a significant amount of the imazosulfuron sorbed is not easily desorbed. The desorption process showed an evident hysteresis phenomenon, which may contribute to the persistence of imazosulfuron in soil.

Adsorption of Highly Soluble Herbicides from Water Using Activated Carbon and Hypercrosslinked Polymers

Adsorption of water-soluble herbicides, namely benazolin, bentazone, imazapyr and triclopyr, has been investigated using commercial Chemviron F-400 activated carbon and Purolite MN-200 hypercrosslinked polymer. Batch adsorption isotherms at pH 3 and 10 show that adsorption of water-soluble herbicides is significantly greater on F-400 than MN-200. Rapid small-scale mini-column adsorption studies of each herbicide on F-400 and MN-200 have also been performed. For Chemviron F-400, the breakthrough of each herbicide at the EU limit of 0.1 μg l-1 is as follows: imazapyr (80,000 BV), bentazone (105,000 BV), benazolin (140,000 BV) and triclopyr (160,000 BV). These experiments operated at an emptybed- contact-time (EBCT) of 2.3 secondswith feed water containing 20 μg l-1 of each herbicide in the absence of natural organic matter. MN-200 is less effective in removing these herbicides from contaminated water under similar conditions. The presence of fulvic acid in the feed water significantly diminishes the uptake of each herbicide for F-400 and MN-200. Low temperature regeneration of Chemviron F-400 activated carbon and Purolite MN-200 hypercrosslinked polymer was achieved using ethanol solution at 50°C and pH 12. Virtually complete regeneration is achieved with MN-200 in 10 BV. Approximately 200 BV of eluent is required with F-400 and the regenerant efficiencies are about 100%for benazolin and triclopyr and about 40-50% for bentazone and imazapyr after two cycles.

HYSTERETIC BEHAVIOR OF METOLACHLOR ADSORPTION-DESORPTION IN SOILS

Adsorption and desorption of herbicides are important processes that influence the amount of herbicide retained by the soil and that which is susceptible to runoff or movement in the soil profile. In this study, we examined the adsorption and desorption characteristics of metolachlor in two Louisian

Optimization of Adsorption of Hydrophobic Herbicides on Montmorillonite Preadsorbed by Monovalent Organic Cations: Interaction between Phenyl Rings

This study aimed to optimize organo-clay formulations for reduction of leaching of the herbicides alachlor, metolachlor, and norflurazon, which include a phenyl ring in the structure. The adsorbed amounts of herbicides increased severalfold when montmorillonite was preadsorbed by an organic cation; benzyltrimethylammonium (BTMA) was more effective than benzyltriethylammonium (BTEA). Fourier transform infrared studies indicated interactions between alachlor molecules and adsorbed BTMA. The adsorption affinity of the herbicides increased with BTEA loading up to the cation exchange capacity (CEC) of montmorillonite but reached a maximum at a BTMA loading of 5/8 of the CEC. The enhanced adsorbed amounts of herbicides are mainly due to interactions between the phenyl rings of herbicide molecules and organic cations, which are favored with the smaller cation, BTMA. BTMA preadsorbed on the clay up to the CEC forms a fraction (14−18%) of charged dimers so that less phenyl rings are available for interacting with ...