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At least 73 records · Page 4Linked to original sources
PubMed2000

Investigation into the effects of temperature and stirring rate on the solid-phase extraction of diuron from water using a C18 extraction disk.

A novel experimental method for determining the equilibrium constant, Keq, and the uptake rate constant, kup, for the solid-phase extraction (SPE) of diuron from water using a C18 Empore extraction disk is reported. Log Keq and log kup are determined at 7.0, 11.0, 18.0 and 23.0 degrees C and for stirring rates of 100, 200 and 400 rpm. From a Van 't Hoff plot of log Keq versus T-1 the enthalpy of sorption, delta H0, is shown to be negative which indicates that the thermodynamic process of uptake is exothermic. The rate of stirring has no effect on log Keq over the temperature range 7.0-23.0 degrees C. The enthalpy of activation, delta H0, calculated from Arrhenius plots of log kup versus T-1 at 100, 200 and 400 rpm show that the kinetic process of uptake is endothermic. At 100 rpm the rate of uptake is limited by the aqueous diffusion of diuron. At 200 rpm or greater the aqueous diffusion layer around the disk is sufficiently small to prevent diffusion from being a limiting factor. The method described in this paper is limited to the analysis of analytes that contain a significant UV chromophore and are relatively soluble in water, but it can also be used to investigate pH and salinity effects on the SPE of diuron from water.

Chromatography, Liquid↗
PubMed1998

Biodegradation of the herbicide Diuron in soil by indigenous actinomycetes.

Three actinomycete strains isolated from soil treated with 2,4-D were able to degrade the herbicide Diuron in vitro. Strain CCT 4916 was the most efficient, degrading up to 37% of applied Diuron (100 mg Kg-1 soil) in 7 days, as measured by HPLC and UV/VIS spectroscopy. All strains showed protease and urease activity; intracellular activity of metapyrocatechase and pyrocatechase were not found. Actinomycete strain CCT 4916 produced manganese peroxidase, which could be potentially related to degradation of Diuron.

Actinomycetaceae↗
PubMed1999

Degradation of three phenylurea herbicides (chlortoluron, isoproturon and diuron) by micromycetes isolated from soil.

As part of a study conducted on the fate of xenobiotics in the environment, a selection of 100 strains of micromycetes (Ascomycetes, Basidiomycetes and Yeasts) have been cultivated in liquid synthetic medium with 3 phenylurea herbicides: chlortoluron and isoproturon (100mg L-1) and diuron (20mg L-1). While 17 strains depleted isoproturon over 50% only 4 depleted diuron and 2 chlortoluron at the same level. The best results were obtained with Bjerkandera adusta and Oxysporus sp which were the most efficient towards the 3 substrates. After 2 weeks Bjerkandera adusta depleted chlortoluron 98%, diuron 92% and isoproturon 88%.

Ascomycota↗
PubMed1982

Aerobic degradation of diuron by aquatic microorganisms.

Degradation of diuron [3-(3,4-dichlorophenyl)-1,1-dimethyl-urea] by microorganisms obtained from pond water and sediment was determined under aerobic conditions. Enrichment procedures were used to isolate cultures capable of degrading the herbicide. Several mixed fungal/bacterial and mixed bacterial cultures were isolated that could degrade diuron. The mixed cultures degraded 67-99% of the added diuron forming from six to seven products which were separated via TLC. The major degradation product detected in most culture extracts was 3,4-dichloroanaline. Other identified products formed were 3-(3,4-dichlorophenyl)-1-methyl-urea and 3-(3,4-dichlorophenyl)urea.

Aerobiosis↗
PubMed1989

Nuclearly inherited diuron-resistant mutations conferring a deficiency in the NADH--or succinate--ubiquinone oxidoreductase activity in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, diuron, antimycin and myxothiazol block the respiratory pathway at the bc1 complex level. Nuclearly inherited mutations located at the DIU3 and DIU4 loci confer in vitro resistance to diuron and cross-resistance to antimycin and myxothiazol at the NADH oxidase level. The mutant strains do not exhibit diuron resistance at the quinol-cytochrome-c oxidoreductase level. Thus, the apparent resistance does not seem to be the result of a modification of the inhibitory sites. Instead, the quinone reduction rate was found to be altered in the mutant. The diu3 mutations lead to a deficiency of the NADH--ubiquinone oxidoreductase activity, and the diu4 mutations to a deficiency of the succinate--ubiquinone oxidoreductase activity. On the basis of the model of Kröger and Klingenberg, a decrease of quinone reduction could explain the resistance to the bc1 complex inhibitors. Thus, the apparent resistance to the bc1 complex inhibitors was found to be due to a modification of the electron transfer kinetics.

Antimycin A↗
PubMed2001

Degradation products of a phenylurea herbicide, diuron: synthesis, ecotoxicity, and biotransformation.

The degradation products of diuron (photoproducts and metabolites), already described in the literature, were synthesized in order to carry out further investigations. Their ecotoxicity was determined using the standardized Microtox test, and most of the derivatives presented a nontarget toxicity higher than that of diuron. Therefore, the biotransformation of these compounds was tested with four fungal strains and a bacterial strain, which were known to be efficient for diuron transformation. With the exception of the 3,4-dichlorophenylurea, all the degradation products underwent other transformations with most of the strains tested, but no mineralization was observed. For many of them, the biodegradation compound for which the toxicity was important was 3,4-dichlorophenylurea. This study underlines the importance of knowing the nature of the degradation products, which has to be kept in mind while analyzing natural water samples or soil samples.

Bacteria↗
PubMed2005

Movement of diuron and hexazinone in clay soil and infiltrated pond water.

Pre-emergence herbicide residues were detected in domestic wells sampled near Tracy, CA. This study sought to determine the source of contamination by comparing soil distribution of diuron [N'-(3,4-dichlorophenyl)-N,N-dimethylurea] and hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] in an agricultural field where the soil was a cracking clay to infiltration of residues in water captured by an adjacent holding pond. Diuron and hexazinone were applied in December to a 3-yr-old alfalfa (Medicago sativa L.) crop. Water content of soil taken after major rainfall but before irrigation at 106 d after application was elevated at the lowest depth sampled centered at 953 mm, indicating water was available for percolation. Herbicide residues (reporting limit 8 microg kg(-1)) were confined above the 152 mm soil depth, even after subsequent application of two border-check surface irrigations. The pattern of distribution and concentration of residues in the soil were similar to results obtained from the LEACHM model, suggesting that macropore flow was limited to a shallow depth of soil. Herbicide residues were measured in runoff water at the first irrigation at 20 microg L(-1) for diuron and 1 microg L(-1) for hexazinone. Runoff water captured in the pond rapidly infiltrated into the subsurface soil, causing a concomitant rise in ground water elevation near the pond. Herbicide residues were also detected in the sampled ground water. We concluded that the pond was the predominant source for movement to ground water. Since addition of a surfactant to the spray mixture did not reduce concentrations in runoff water, mitigation methods will focus on minimizing infiltration of water from the pond.

Aluminum Silicates↗
PubMed1998

[The determination of diuron and chlortoluron residues in beef and beef products by high performance liquid chromatography].

Amethod for the determination of diuron and chlortoluron in beef and beef products with high performance liquid chromatography is described. The sample was extracted with a mixture of acetonitrile and methanol (50:50, V/V). After filtration, the filtrate was defatted with petroleum ether, then water was added and further extracted with chloroform. The chloroform collected was evaporated in a rotary evaporator(45 degrees C). The residue was dissolved in acetonitrile-methanol(50:50, V/V) mixture, poured into an Al2O3 column and eluted with the same mixture. The eluate was collected for HPLC analysis. The analytical column was Selectosil C18 (5 microns, 250 mm x 4.6 mm i.d.), mobile phase was methanol-water(60:40, V/V) and detection wavelength was UV-245 nm. The minimum amounts of detection were 0.4 ng for diuron and 0.5 ng for chlortoluron. Recoveries were 87.34%-87.64% for diuron and 88.78%-91.94% for chlortoluron.

Animals↗
PubMedDate not supplied

Levels of 3,3',4,4'-tetrachloroazobenzene in diuron and linuron herbicide formulations.

Levels of 3,3',4,4'-tetrachloroazobenzene (TCAB) were determined by capillary gas chromatography (GC) with electron-capture detection (ECD) in 25 samples of diuron and linuron formulations obtained from the Canadian market. Acidic aqueous methanol was used to retain urea herbicide and the neutral TCAB was allowed to partition into hexane. Silica gel was used for cleanup of the hexane extract, followed by GC/ECD determination. Recovery data obtained at 4 different spiking levels (i.e., 0.3, 0.1, 1.0, and 5.0 ppm) in linuron averaged 93, 86, 85, and 97%, respectively. For diuron, spiking was done at 0.5, 1.0, and 5.0 ppm levels and the corresponding average percent recoveries were 95, 101, and 104. The TCAB contamination level observed in diuron on a 100% active ingredient basis ranged from 0.15 to 3.38 ppm, whereas in linuron, it varied from 0.91 to 10.28 ppm.

Azo Compounds↗
PubMed1988

Molecular basis for resistance to antimycin and diuron, Q-cycle inhibitors acting at the Qi site in the mitochondrial ubiquinol-cytochrome c reductase in Saccharomyces cerevisiae.

The bc1 complex of the mitochondrial respiratory chain transfers electrons from ubiquinol to cytochrome c oxidase. Cytochrome b, a transmembranous protein, is thought to form a transmembrane electron circuit, transferring electrons between two ubiquinone redox sites, (Qi) and (Qo), respectively, near the inner and outer sides of the inner mitochondrial membrane. Antimycin and diuron appear to block cytochrome b oxidation-reduction at one ubiquinone site, presumably Qi. The cytochrome b gene is carried by the organelle DNA. Yeast mutants resistant to antimycin and diuron have been previously isolated and mapped to specific loci of the cytochrome b gene. In the present work the mutated amino acid residues from nine antimycin- and three diuron-resistant mutants have been identified by sequencing the relevant segments of the resistant cytochrome b gene. The sequencings were performed by primer extension in the presence of dideoxynucleotides on total mitochondrial RNA preparations using reverse transcriptase. Regions of the cytochrome b protein affecting the inhibitor and putative quinone-binding sites have been defined.

Amino Acid Sequence↗
PubMed1978

Bromacil and diuron residue levels in Florida citrus soils.

The widespread use of herbicides in Florida citrus groves raises the possibility of residue accumulation following repeated applications. To determine residue levels of commonly used herbicides, soil samples were taken from large experimental plots in commercial groves in Polk and Hardee Counties. Bromacil and diuron had been applied in combination at both locations for 7-8 years. Analyses of samples showed low levels of both herbicides at various soil depths to 60 cm. Only a small amount of bromacil was detectable one year after applications, but diuron levels were higher. Continuous applications at recommended rates and frequencies have resulted in maximum bromacil and diuron levels of 3.9 percent and 13.1 percent, respectively, of their total application.

Bromouracil↗
PubMed2000

Soil dissipation of diuron, chlorotoluron, simazine, propyzamide, and diflufenican herbicides after repeated applications in fruit tree orchards.

In a pear tree orchard planted on loam soil, each plot was treated in April 1998 with either one of the ureas diuron or chlorotoluron, or triazine simazine herbicides applied at 3, 4, and 2 kg AI ha(-1), respectively. Some plots had not been previously treated with one of these herbicides. Other plots had been treated annually during the past 12 years with the same herbicide. One herbicide, and always the same, was thus applied to each plot. In the plots treated for the first time with either diuron, chlorotoluron, or simazine, the soil half-lives of these herbicides in the 0-10 cm surface soil layer were 81, 64, and 59 days, respectively. In the plots treated with the same herbicide for 12 years, the corresponding soil half-lives were 37, 11, and 46 days. Diuron thus produced a moderately enhanced biodegradation, chlorotoluron a high one, and simazine a low but significant one. In another pear tree orchard planted on sandy loam soil, each plot was treated in April 1998 with one of the amide propyzamide (1.25 or 1.0 AI kg ha(-1)) or diflufenican (250 g AI ha(-1)) herbicides. In the plots not previously treated with propyzamide, the propyzamide soil half-life was the same for both doses, i.e., about 30 days. In the plots treated annually for 3 or 14 years with propyzamide, the soil half-life was 12 and 10 days, respectively. In the plots treated for the first time with diflufenican and in those treated annually with diflufenican for 3 years, the diflufenican soil half-life was the same, i.e., 65 days. Propyzamide thus already showed a highly accelerated biodegradation after 3 years of repeated annual applications. Diflufenican, however, did not show enhanced biodegradation after 3 years of repeated annual applications.

Fruit↗
PubMed2002

Effect of cropping cycles and repeated herbicide applications on the degradation of diclofop-methyl, bentazone, diuron, isoproturon and pendimethalin in soil.

A greenhouse study was conducted to investigate the ability of four crops (wheat, corn, oilseed rape and soybean) to influence the degradation of bentazone, diclofop-methyl, diuron, isoproturon and pendimethalin in soil. The present study showed that microbial biomass-carbon was significantly higher in planted soils than in bulk soil, especially with wheat and corn, after several cropping cycles. The biomass in corn and soybean planted soils was adversely affected by bentazone but recovered after three cropping cycles. In wheat-planted soils, diclofop-methyl application resulted in persistent increase of the amount of microbial biomass. Bentazone did not show accelerated degradation even after five successive treatments, differing from diclofop-methyl, for which two applications were sufficient to enhance significantly its rate of degradation. Enhanced degradation of diclofop-methyl was even more pronounced in wheat-planted soil. The rates of mineralisation of diuron, isoproturon and pendimethalin were not affected after the first cropping cycle, but were significantly increased in planted soils after five cropping cycles. The results confirm that plants may promote pesticide degradation in soil by stimulating biodegradation processes. In the case of diclofop-methyl, stimulation of accelerated degradation was observed.

Agriculture↗
PubMed2000

Effects of carbofuran, diuron, and nicosulfuron on acetylcholinesterase activity in goldfish (Carassius auratus).

Juvenile goldfish (Carassius auratus) were exposed to three widely used pesticides; carbofuran, diuron, and nicosulfuron. Acetylcholinesterase (AChE) activity and molecular forms of AChE were first characterized in brain and skeletal muscle of unexposed fish. Skeletal muscle had higher AChE activity than brain (306 and 215 nmol/min/mg protein, respectively). In brain, four molecular forms of AChE were found: A12, G4, G2, and G1. In the muscle, three molecular forms were found A12, A8, and G2. AChE activity was then evaluated in both tissues of fish exposed to different concentration of pesticides (5, 50, and 500 microg/L) for 6, 12, 24, and 48 h. In brain, AChE activity was significantly inhibited during all the periods of exposure in response to 50 microg/L (19-28%) and 500 microg/L (85-87%) carbofuran. Such effect was observed in the muscle only at 500 microg/L (86-92%). Carbofuran had no effect on the distribution of molecular forms. Significant inhibitions (9-12%) of brain AChE activity were also observed in response to diuron and nicosulfuron at 500 microg/L during all periods of exposure and for 50 microg/L nicosulfuron after 24 and 48 h. This study pointed out short-term effects of exposure to sublethal concentrations of the three pesticides, ranging among different chemical families, on brain and muscle AChE in goldfish.

Acetylcholinesterase↗
PubMed1989

Two nuclearly inherited loci conferring increased diuron resistance to NADH oxidase in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, diuron blocks the respiration pathway at the level of the bc1 complex. Nuclear diuron-resistant mutations which confer in vitro resistance to mitochondrial NADH oxidase have been identified. Five mutations were found to be clustered at two distinct nuclear loci DIU3 and DIU4. The distance between the two loci was estimated to be about 36.7 cM. These loci do not appear to be centromere-linked and did not show a linkage to any of the genes coding for bc1 complex subunits. DIU3 and DIU4 loci might, therefore code for other components of the respiratory chain.

Alleles↗
PubMed2000

Detoxication of the herbicide diuron by Pseudomonas sp.

A strain of bacteria able to detoxicate the herbicide diuron in pure culture was isolated from sites contaminated with different urea herbicides. Diuron was used as a sole source of carbon and energy by this isolate which is a Gram-negative, aerobic, rod-shaped bacterium with a single polar flagellum, and grows at 40 degrees C. The strain has been identified as Pseudomonas sp.

Biodegradation, Environmental↗
PubMed1998

Chronic effects of the herbicide diuron on freshwater cladocerans, amphipods, midges, minnows, worms, and snails.

The chronic effects of the herbicide diuron on survival and reproduction of Daphnia pulex, and survival and growth of the amphipod Hyalella azteca, the midge Chironomus tentans, juvenile and embryo/larval fathead minnows, Pimephales promelas, annelid worms, Lumbriculus variegatus, and snails, Physa gyrina, were determined in laboratory static and static-renewal tests. D. pulex 96-h and 7-day LC50 values were 17.9 and 7.1 mg/L; 7-day LOAEL and NOAEL values based on mortality and reproduction were 7.7 and 4.0 mg/L. H. azteca 96-h and 10-day LC50 values were 19.4 and 18.4 mg/L; 10-day LOAEL and NOAEL values based on survival and reduced weight were 15.7 and 7.9 mg/L. C. tentans 10-day LC50 value was 3.3 mg/L; 10-day LOAEL and NOAEL values based on growth were 7.1 and 3.4 mg/L, and 3.4 and 1.9 mg/L based on mortality. Juvenile fathead minnows had a 10-day LC50 of 27.1 mg/L and 10-day LOAEL and NOAEL values based on growth of 3.4 and <3.4 mg/L. The fathead minnow embryo-larval test had a 7-day LC50 value of 11.7 mg/L and 7-day LOAEL and NOAEL values based on reduced growth of 8.3 and 4.2 mg/L. L. variegatus had 10-day LOAEL and NOAEL values based on reduced weight of 3.5 and 1.8 mg/L. P. gyrina had 10-day LOAEL and NOAEL values based on reduced weight of 22.8 and 13.4 mg/L. Laboratory effects concentrations were higher that those found in normal field application situations, except in areas of localized pooling after recent herbicide applications, indicating that there would probably be little harm to these fish and invertebrates from diuron exposure in the field.

Animals↗
PubMed1988

Two changes of the same nucleotide confer resistance to diuron and antimycin in the mitochondrial cytochrome b gene of Schizosaccharomyces pombe.

Diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) and antimycin, both inhibitors of mitochondrial respiration, block electron flow between cytochromes b and c1. Mutants resistant to either drug have been selected using Schizosaccharomyces pombe strains with an extrachromosomally inherited mutator. In analogy to Saccharomyces cerevisiae these mutational sites were assumed to map in the cytochrome b gene. DNA sequence analysis showed that two changes in the same nucleotide are responsible for resistance to antimycin and diuron. Analysis of resistant and sensitive progeny of crosses between the mutants and the wild type confirmed the correlation between mutational alteration and resistant phenotype.

Amino Acid Sequence↗