Degradation Of Chlorsulfuron Research Articles

Alkaline Soil Degradation and Crop Safety of 5-Substituted Chlorsulfuron Derivatives.

Sulfonylurea herbicides can lead to serious weed resistance due to their long degradation times and large-scale applications. This is especially true for chlorsulfuron, a widely used acetolactate synthase inhibitor used around the world. Its persistence in soil often affects the growth of crop seedlings in the following crop rotation, and leads to serious environmental pollution all over the world. Our research goal is to obtain chlorsulfuron-derived herbicides with high herbicidal activities, fast degradation times, as well as good crop safety. On account of the slow natural degradation of chlorsulfuron in alkaline soil, based on the previously reported results in acidic soil, the degradation behaviours of 5-substituted chlorsulfuron analogues (L101–L107) were investigated in a soil with pH 8.39. The experimental data indicated that 5-substituted chlorsulfuron compounds could accelerate degradation rates in alkaline soil, and thus, highlighted the potential for rational controllable degradation in soil. The degradation rates of these chlorsulfuron derivatives were accelerated by 1.84–77.22-fold, compared to chlorsulfuron, and exhibited excellent crop safety in wheat and corn (through pre-emergence treatment). In combination with bioassay activities, acidic and alkaline soil degradation, and crop safety, it was concluded that compounds L104 and L107, with ethyl or methyl groups, are potential green sulfonylurea herbicides for pre-emergence treatment on wheat and corn. This paper provides a reference for the further design of new sulfonylurea herbicides with high herbicidal activity, fast, controllable degradation rates, and high crop safety.

A Novel Magnetically Recoverable Photocatalyst for Removal of Organic Compounds from Contaminated Water

A novel magnetically recoverable core-shell Fe3O4@Ag3PO4/AgCl photocatalyst has been developed featuring fast magnetic separation, stability and high photocatalytic activity under simulated solar light. This novel core-shell photocatalyst exhibited high photocatalytic activity towards degradation of chlorsulfuron (ChS) under simulated solar light. The complete degradation of ChS over the Fe3O4@Ag3PO4/AgCl photocatalyst took only about 60min. As a result, the developed photocatalytic integrated microspheres can effectively degrade organic pollutants and can be easily recovered by a magnet, and reused at least five times without appreciable reduction in photocatalytic efficiency. Therefore, the Fe3O4@Ag3PO4/AgCl photocatalyst developed in this study is a promising alternative for degrading organic pollutants.

Rhizoremediation of residual sulfonylurea herbicides in agricultural soils using Lens culinaris and a commercial supplement

ABSTRACTSulfonylureas (SU) are a popular herbicide used today for controlling weeds. While beneficial for this purpose they present a persistent problem in agricultural treated areas, with this treatment proving detrimental for successive crops. This study assessed the phytoremediative properties of lentils (Lens culinaris) grown in uncontaminated and chlorsulfuron-contaminated soil, with and without the addition of a growth supplement, PulseAider™. The results show that in the presence of lentils the degradation of chlorsulfuron is enhanced and this degradation rate is significantly increased when the PulseAider™ supplement was included during seed sowing. The supplement PulseAider™ also significantly increased shoot and root biomass, root branching, and nodule number under control conditions. While this was not so for plants grown in contaminated soils, the PulseAider™ supplement seemed to alter root branching and morphology. Most Probable Number (MPN) assays showed increased numbers of potential chlorsulfuron-degrading bacteria in soil treated with PulseAider™, although this was found to be significant only in the control soil. Sequencing of the 16S ribosomal gene showed the presence of Pseudomonas fluorescens bacterial species which is a known chlorsulfuron-degrading bacterium. This study is one of the first to address the remediation of residual SU herbicides and offers an economically feasible solution that may have an impact on global food security.

WITHDRAWN: Chlorsulfuron degradation through bio-augmentation of soils by fungal strains and chemical hydrolysis

Abstract Bioremediation of pesticides is imperative for a sustainable environment. For this purpose soil borne, pure fungal strains; Aspergillus niger and Penicillium chrysogenum were augmented in soils spiked with herbicide, Chlorsulfuron from four distinct regions of Pakistan. These strains were found to utilize Chlorsulfuron as their carbon and energy sources. Solid-liquid extraction of pesticide was followed by analysis through high performance liquid chromatography and gas chromatography mass spectrometry. Chemical hydrolysis experiments, performed on the same soils were also found to degrade Chlorsulfuron (50%) but to a lesser extent than biodegradation (76 and 74% by both strains). Degradation rate followed first order reaction kinetics. Two major metabolites were obtained after degradation; 2-chlorobenzenesulfonamide and 2-amino-4-methoxy-6-methyl-1,3,5-triazine. Aspergillus niger degraded Chlorsulfuron (76%) slightly more than Penicillium chrysogenum (74%). R 2 for degradation rates for all soil samples by both fungal strains were close to 1 and P values were less than 0.05, indicating significance of results.

Electrochemical Degradation of Chlorsulfuron Herbicide from Water Solution Using Ti/IrO<sub>2</sub>-Pt Anode

Chlorsulfuron (ChS) which is a nonbiodegradable herbicide was effectively removed using an electrochemical method at the Ti/IrO2-Pt anode. The influences of current density, initial ChS concentration, initial solution pH and different NaCl dosages on electrochemical degradation of ChS were investigated. HOCl formed during electrolysis and quickly generated .OH radicals would likely play an important role in the electrochemical degradation of ChS with the presence of NaCl. At current density of 20 mA?cm–2, ChS concentration decreased from 1 mg.L–1 to 0 mg.L–1 after 10 min electrolysis with 0.2 g?L–1 NaCl dosage. It was found that the ChS removal rate increased with increasing current density and the ChS degradation was similar at different initial pH values, which means that Ti/IrO2-Pt anode can be used in a wide pH range. The electrochemical performance of Ti/IrO2-Pt anode for degradation of ChS will not decrease after serviced for a long time. These results reveal that an electrochemical approach would be a novel treatment method for effective and rapid degradation of ChS herbicide from aqueous solution.

Photocatalytic degradation of a sulfonylurea herbicide over pure and tin-doped TiO 2 photocatalysts

The heterogeneous photocatalytic degradation of chlorsulfuron (ChS), a sulfonylurea herbicide, has been studied using home-made Sn-doped TiO 2 samples and TiO 2 P25 from Degussa as photocatalysts. First-order kinetics were found for the disappearance of chlorsulfuron using both types of materials. Three synthesized photocatalysts were used, two of them containing 11 and 20 mass% of Sn, respectively, and one composed of pure anatase TiO 2. The sample with the lower content of tin is formed by anatase and rutile crystallites, whereas the one with a higher doping level contains anatase, rutile and SnO 2 phases. Comparison between their efficiency in the photocatalytic degradation of chlorsulfuron indicated a beneficial effect of the presence of Sn 4+ in the TiO 2 lattice, whereas segregated SnO 2 phase induced a slower degradation of ChS when compared to pure TiO 2. However, Degussa TiO 2 P25 remains the most active material for this reaction. Based on DRIFTS and adsorption observations, an inverse dependence of the photocatalytic activity on the water adsorption capacity of the samples is proposed.

Degradation of chlorsulfuron and triasulfuron in alkaline soils under laboratory conditions

The degradation of chlorsulfuron and triasulfuron was investigated in alkaline soils (pH 7.1–9.4) spiked at 40 μg a.i. kg–1 under laboratory conditions at 25 °C and a moisture content corresponding to 70% field capacity (–33 kPa), using high‐performance liquid chromatography. Degradation data for the two herbicides did not follow first‐order kinetics, and observed DT50 values in surface soils ranged from 19 to 42 days and from 3 to 24 days for chlorsulfuron and triasulfuron respectively. Disappearance of both chlorsulfuron and triasulfuron was faster in non‐sterile than in sterile soil, demonstrating the importance of microbes in the breakdown process. The persistence of chlorsulfuron increased with increasing depth, which can be attributed to the decline in the microbial populations down the profile. The DT50 value for chlorsulfuron at 30–40 cm depth was nearly four times higher than that in the top‐soil. The results obtained show that persistence of these herbicides in alkaline surface soils at 25 °C and at a moisture content of 70% field capacity is similar to those reported in other European and North American soils. The study shows that if these herbicides are contained in surface soil layers, the risk of residue carry‐over under southern Australian conditions is small. However, the rate of their degradation in alkaline subsoils is very slow, and under conditions conducive to leaching their prolonged persistence in the soil profile is possible.

Rates of chlorsulfuron degradation in three Brazilian oxisols

SummaryThe degradation of chlorsulfuron was studied in laboratory experiments in three oxisols from south and south–east Brazil. Three soil profiles were sampled by horizon, and classified according to USDA soil taxonomy and the Brazilian system. Degradation assays were made to evaluate the influence of temperature, humidity and liming on chlorsulfuron decomposition. Further experiments were set up to study enhanced biodegradation. Abiotic degradation was also studied in sterile soils, to evaluate, by comparison with non–sterile soils, the role of microorganisms in degradation. The degradation always followed first–order kinetics and was generally faster in samples from A than B horizons. An increase in temperature (from 25 to 40°C) increased chlorsulfuron degradation. Further, an increase in moisture content increased chlorsulfuron degradation in samples from the A horizons of all soils, whereas for two out of three soils, degradation in samples from the B horizon was greater at lower water content. The biotic contribution to degradation was significant only for the soil with higher fertility. Soil liming significantly increased chlorsulfuron half–life in all samples. Significant enhancement of degradation (decrease in half–life on reapplication) was observed only in soil from A horizons, where a higher microbial activity was likely.

Field leaching and degradation of soil applied herbicides in a gradationally textured alkaline soil: chlorsulfuron and triasulfuron

A bioassay method was used to monitor changes in the leaching and degradation of chlorsulfuron and triasulfuron in a field experiment on a gradationally textured alkaline cropping soil. Following application in May 1991, it was estimated that approximately 46% of chlorsulfuron and 21% of triasulfuron were leached beyond 50 cm by late winter 1991 with 103 mm of cumulative rainfall. No leaching was detected from mid spring 1991 to early autumn 1992. During this time the sulfonylureas were rapidly degraded, with a 50% reduction in residues complete by 80 days. The degradation was increased by increasing soil temperatures and not constrained by lowering soil water contents. Leaching of the sulfonylureas took place again in the following growing season, between late autumn and mid spring 1992, where trace quantities of the herbicides moved from shallower depths to reaccumulate at higher levels, deeper in the soil profile. A part of these residues still remained within the 20-30 cm, 30-40 cm and 40-50 cm soil layers at mid spring 1992, after 344 mm of growing season rainfall. The residues were in the range 0.1 to 0.4 ng g-1 soil of chlorsulfuron and triasulfuron, for this last sampling taken approximately 18 months after the commencement of the experiment. These residue levels are known to be phytotoxic to leguminous crop and pasture species, and oilseed crop species.

Evaluation of a simulation model for prediction of chlorsulfuron fate in an Umbrian soil

A mathematical model described by Nicholls et al. ( Pestic. Sci., 12 (1982) 484–494) has been used to simulate the movement and the degradation of chlorsulfuron in an Umbrian soil, following application to the soil surface in autumn. Experiments were also performed on soil columns that had been surface-treated with chlorsulfuron and irrigated daily with water doses corresponding to the pluviometric records. The comparison between experimental and simulation data suggests that the model gives a reasonable description of the fate of chlorsulfuron and that it should prove of value in assessing variations in pesticide movement after different periods of application and at different sites. The differences found in the bottom layers of the columns could be due to the fact that capillary water movement is affected by the ending of the soil columns. The physical model could show a lower chlorsulfuron mobility in deeper layers where the stratum of soil ends. A defect in the physical model may have been responsible for the observed differences.

Aspergillus nigerand aPenicilliumsp. are not directly involved in the degradation of chlorsulfuron

When Aspergillus niger or a Penicillium sp. were grown in potato dextrose broth supplemented with chlorsulfuron, the herbicide concentration decreased by 97–99% within 78–96 h and the pH of the medium fell from 7.2 to between 2.4 and 3.1. If, during growth, the pH was maintained at or near neutrality, no decrease in herbicide concentration occurred. When sterile medium containing the herbicide was titrated with acid to mimic acid formation during fungal growth, the herbicide concentration again declined. Precipitation was not responsible for the observed decrease. The data indicate that, in laboratory media, these fungi do not directly metabolise the herbicide as previously thought. Chlorsulfuron degradation in perfused soil cores was not enhanced by inoculation with A. niger. Our results show that A. niger and a Penicillium sp. do not degrade chlorsulfuron.

Adsorption and degradation of chlorsulfuron and metsulfuron‐methyl in soils from different depths

SummaryAdsorption and degradation rates of chlorsulfuron and metsulfuron‐methyl were measured in soil taken from depths of 0–20, 20–40 and 40–60 cm at eight sites. Adsorption of both herbicides was negatively correlated with soil pH, and positively correlated with soil organic matter content. When two soils with very high organic matter were excluded from the calculations, the correlations with organic matter content were no longer statistically significant but those with soil pH were affected only slightly. Degradation rates of both herbicides generally decreased with increasing depth in the soil and were positively correlated with microbial biomass and negatively correlated with soil pH. The possible significance of the results to persistence of the herbicides in the field is discussed.

Crop responses to applications of both chlorsulfuron and monoammonium phosphate

Field studies were conducted at two locations of different soil pH in Saskatchewan using preemergence chlorsulfuron and granular monoammonium phosphate. In year one, barley was not adversely affected by chlorsulfuron applied in the spring at 11.25 and 22.5 g a.i. ha−1 (Kernen location, soil pH 7.5) or 22.5 and 45.0 g a.i. ha−1 (Scott location, soil pH 5.5). In year two, the residual chlorsulfuron did not affect flax seed yield on the acid soil, but caused substantial crop damage to flax and lentil on the neutral soil. In general, flax and lentil were more injured by chlorsulfuron residues where lower rates of MAP had been applied the previous year, suggesting that the presence of a MAP band in the soil at the time of herbicide application may have slowed the rate of chlorsulfuron degradation. A corn-root bioassay procedure was adapted to estimate residue levels in soil samples taken from the field trials.

Field Duration of Chlorsulfuron Bioactivity in the Central Great Plains

AbstractThe duration of chlorsulfuron {2‐chloro‐N [(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl)aminocarbonyl]benzenesulfonamide} bioactivity in Central Great Plains soils was determined by measuring the influence of several environmental factors on chlorsulfuron degradation. Chlorsulfuron was applied at 35 and 70 g ha−1 to four soils: Platner sandy loam and Weld (Aridic Paleustolls) loam at Akron, CO; Roxbury (Cumulic Haplustoll) silt loam at Jetmore, KS; and Rosebud (Aridic Argiustolls) sandy loam at Chugwater, WY. Soil pH, organic matter level, number of precipitation events >0.25 cm, and leaching were the major environmental factors influencing chlorsulfuron duration of bioactivity. A chlorsulfuron rate × soil × year interaction occurred, but this interaction was not consistent over all soils. A model developed for predicting chlorsulfuron duration of bioactivity would be more accurate if designed for soils with similar organic matter levels, as organic matter level influenced duration of bioactivity and leaching of chlorsulfuron. Chlorsulfuron leaching was also affected by soil type and year of study. In greenhouse bioassay studies, sunflower (Helianthus annuus L.) did not differ from corn (Zea mays L.) in sensitivity to chlorsulfuron residues in soil.

Degradation of Chlorsulfuron by Soil Microorganisms

Degradation of chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-yl)amino] carbonyl] benzenesulfonamide} in acidic and alkaline soils was evaluated using plant bioassay and high-performance liquid chromatography (HPLC) radiotracer techniques. Soil sterilization with either ethylene oxide (Et0) or gamma irradiation significantly reduced breakdown of chlorsulfuron; the ability for degradation was restored by reinoculation with indigenous soil microorganisms. Streptomyces griseolus (a soil actinomycete), Aspergillus niger, and Penicillium sp. (soil fungi) were demonstrated to degrade 14C-chlorsulfuron in pure culture. In addition to microbial breakdown, chemical hydrolysis was an important factor in the disappearance of chlorsulfuron from soil. The contribution of chemical hydrolysis to total degradation was a function of soil pH, with hydrolysis occurring most rapidly in acidic soils. Both dissipation processes slowed markedly at low temperatures.

Residual Phytotoxicity of Chlorsulfuron in Two Soils

AbstractChlorsulfuron {2‐chloro‐N‐[(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl) amino carbonyl] benzenesulfonamide} selectively controls broad‐leaf weeds in winter wheat (Triticum aestivum L.), but also is extremely persistent in soil, resulting in residual injury to succeeding crops that are susceptible to chlorsulfuron. To determine the factors affecting chlorsulfuron degradation, the effect of environmental variables and method of application on chlorsulfuron persistence was measured in a loam and sandy loam soil using a corn (Zea mays L.) root bioassay. Increasing soil temperature from 20 to 40°C decreased chlorsulfuron persistence, with significant differences in chlorsulfuron concentration occurring 31 d after application to the sandy loam soil. Soil water level affected chlorsulfuron persistence only in the loam soil, where increasing the soil water level decreased persistence. Adding wheat residue to the soils increased chlorsulfuron persistence in the sandy loam, but not in the loam soil. One possible explanation for this reduced degradation in the sandy loam was a shift in pH toward basicity, as the addition of 0.050 kg kg−1 wheat residue raised the pH from 6.1 to 7.2. In the loam soil, the wheat residue did not affect soil I~H. Chlorsulfuron persistence was affected by texture, with longer activity occurring in the loam soil in all studies. Incorporating chlorsulfuron caused a greater loss of chlorsulfuron activity in the sandy loam, indicating that incorporation may influence chlorsulfuron persistence.

Basis for Response Differences of Two Broadleaf Weeds to Chlorsulfuron

The basis for differences in response of eastern black nightshade (Solanum ptycanthumDun.), a tolerant species, and velvetleaf (Abutilon theophrastiMedic. ♯3ABUTH), a susceptible species, to foliar-applied chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide} was investigated by evaluating differences in spray retention and herbicide absorption, translocation, and metabolism. Based upon a foliar-applied rate causing a 50% reduction in dry weight, velvetleaf was greater than 20000 times more susceptible to chlorsulfuron than was eastern black nightshade. The differences detected in spray retention, absorption, and translocation were inadequate to account for the large response differences between the two species. The primary difference found was in the rate of chlorsulfuron degradation. In eastern black nightshade, 69.9% of the absorbed chlorsulfuron was metabolized within 24 h of application and 81.1% within 72 h of application. Only 7.1% of absorbed chlorsulfuron was metabolized in velvetleaf in a 72-h period.