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PubMed1985

Induction of sister chromatid exchanges by coal dust and tobacco snuff extracts in human peripheral lymphocytes.

The organic solvent extracts of sub-bituminous coal dust and tobacco snuff, both together and separately, were tested for the induction of sister chromatid exchanges (SCEs) in human peripheral lymphocytes. The results indicate that these extracts induced SCEs, and that when tested together synergistically induced SCEs in two of three donors. Studies with the organic solvent extracts of all five ranks of coal indicate that the extracts of bituminous, lignite, and peat, but not anthracite, induced SCEs. Similar experiments conducted with water extracts show that bituminous, lignite, and peat, but not sub-bituminous extracts, induced SCEs, and that anthracite was equivocal. To determine whether individuals differed in their SCE responses to coal dust extracts, lymphocytes from five donors were tested with organic solvent extracts of bituminous and sub-bituminous coal. An analysis of variance indicates that the SCE response was significantly influenced by the donor (p less than 0.0001) and each of the two coal extracts (p less than 0.0001). From studies of workers occupationally exposed to coal dust, it is known that inhaled coal dust is cleared from the lungs by mucociliary action and introduced into the stomach by swallowing. Coal dust, or coal dust plus snuff, may be responsible for the increased frequency of gastric cancer observed in coal miners. The findings presented here suggest that coal dust, with or without tobacco snuff, may play a role in the elevated incidence of gastric cancer in coal miners. Because water extracts of some ranks of coal induced SCEs, there exists the possibility of adverse environmental effects due to coal leachates.

Coal↗
PubMedDate not supplied

An attempt to improve the SOS chromotest responses.

The SOS Chromotest was carried out on leachates of ten industrial wastes with the standard procedure and a miniaturized version with microplates. The two methods gave identical results in nine samples (eight negative and one positive). A simple additional manipulation is described for the identification of the false positive response that is frequently observed with complex mixtures. It involves challenging the SOS Chromotest bacteria with samples (having previously shown a positive genotoxic response) just before the enzymatic activities (i.e. beta-galactosidase and alkaline phosphatase) are estimated colorimetrically. This additional step eliminates discrepancies between the results for the standard and the miniaturized procedures.

Alkaline Phosphatase↗
PubMed2006

New approach to large-volume injection in reversed-phase high performance liquid chromatography: determination of atrazine and hydroxyatrazine in soil samples.

A well established method of direct injection of larger than conventional sample volumes ranging from 0.1 mL to 10 mL in HPLC is the injection valve method in which a loop of tubing is totally or partially filled with sample. Recent HPLC pumps have a flow-rate setting accuracy of +/- 1-2% over a flow-rate range from 0.1 mL/min to 10 mL/min and the flow stability is 0.2% or less. Quarternary low pressure gradient pumps are widely available and used, but all their hydraulic lines are seldom utilised. The idea of using one line of a common commercial HPLC quaternary low-pressure pump for direct on-column injection (pumping) of large sample volumes ranging from 1 mL to 100 mL was tested. This approach was evaluated during practical work on the development of an RP-HPLC method of determination of residual atrazine and hydroxyatrazine. In lysimetric environmental experiments hydroxyatrazine was formed in situ in a soil column by hydrolysis of atrazine. The results proved the applicability of this approach not only in experiments with model mixtures of analytes at microg/L levels in solutions. Analysis of 20 mL of soil leachates and extracts of soil samples containing atrazine and hydroxyatrazine at the 10 microg/kg level (in dry soil) revealed that good figures-of-merit were preserved, even in the presence of a large excess of humic substances.

Atrazine↗
PubMed2005

Simazine dynamics in a vineyard soil at Casablanca valley, Chile.

Field dissipation, soil movement and laboratory leaching studies were performed to elucidate the effect of two rainfall amounts in the behaviour and environmental fate of simazine under climatic conditions at Casablanca Valley, Chile. Dissipation and soil movement were studied in a field vineyard with a sandy loam soil (Inceptisol; 74.08% sand; 14.87% silt and 11.04% clay). Simazine was applied to bare soil at 2.0 kg AI ha(-1), and its concentration was measured using immunoassay (ELISA) at 0, 10, 20, 40 and 90 days after application under two rainfall amounts, natural field conditions (39 mm) and modified conditions (39 + 180 mm). Simazine leaching was studied using soil core PVC lysimeters (0.9 m height; 0.22 m diameter). Field dissipation data were adjusted with a bi-exponential model. Half-life (DT(50)) values varied between 31.3 (+/-2.5) and 19.0 (+/-4.2) days under natural and modified conditions, respectively. Simazine K(d) varied from 0.42 to 2.15 (K(oc) 32.6-216.2) in the soil profile. Simazine was detected at a 90-cm soil depth in concentrations of 0.0085 (+/-0.0043) mg kg(-1) and 0.0321 (+/-0.001) mg kg(-1) under field and modified conditions, respectively. The maximum simazine leachate concentrations were 0.013 (+/-0.00084) mg litre(-1) (0.012% of total applied simazine) and 0.0084 (+/-0.00082) mg litre(-1) (0.11% of total applied simazine) for field and modified conditions respectively. These data indicate that water quantity has a significant effect on the DT(50) and the amount of simazine that moved through the soil profile, but not on the soil depth reached by this herbicide.

Agriculture↗
PubMed2006

Metribuzin mobility in soil columns as affected by urea fertiliser.

Application of urea fertilisers to soils influences the soil solution characteristics and thus may affect the sorption of soil-applied herbicides. The present investigation reports the influence of urea co-application on sorption and leaching of metribuzin, a triazine herbicide. Urea application at 60 and 120 kg N ha(-1) increased metribuzin sorption in soils over that in untreated natural soil. The Kf (Freundlich adsorption coefficient) values of metribuzin for natural, 60 and 120 kg N ha(-1) treatments were 0.43, 0.46 and 0.84 microg(1 - 1/n) g(-1) ml1/n respectively. Downward mobility of metribuzin was studied in packed soil columns (300 mm length x 59 mm i.d.) at two irrigation intensities, 720 m3 ha(-1) (72 mm) and 3600 m3 ha(-1) (360 mm). After 720 m3 ha(-1) irrigation, metribuzin did not leach out of any column and was not detected in the leachate. Urea amendment slowed the leaching of metribuzin by 20 and 40% in 60 and 120 kg N ha(-1) urea-treated columns respectively. Also, following urea application, greater amounts of metribuzin were retained in the application zone. Upon increasing the irrigation intensity fivefold, urea application did not have any effect on metribuzin mobility, and its breakthrough from both natural and urea-amended columns occurred after 126 mm irrigation. However, there was a marked difference in the maximum concentration of metribuzin in the breakthrough curves obtained from natural and urea-amended columns. The study indicated that co-application of metribuzin and urea fertiliser is a safe practice as far as leaching of herbicide is concerned.

Adsorption↗
PubMed2006

Organic amendments affecting sorption, leaching and dissipation of fungicides in soils.

Metalaxyl and tricyclazole are two fungicides widely used in Spain in vineyard and rice crops respectively. In this study an investigation has been made of the effect of three organic amendments [two commercial amendments, solid fertiormont (SF) and liquid fertiormont (LF), and a residue from the olive oil production industry, alperujo (OW)] on fungicide fate in soils. Changes in soil porosity on amendment were studied by mercury intrusion porosimetry, sorption-desorption studies were performed by the batch equilibration method, dissipation of metalaxyl and tricyclazole in the soil was studied at - 33 kPa moisture content and 20 degrees C and leaching was studied in hand-packed soil columns. Amendments with SF and LF reduced soil porosity, while OW increased porosity through an increase in pore volume in the highest range studied. Tricyclazole sorbed to soils to a much higher extent than metalaxyl. With some exceptions, sorption of both fungicides increased on amendment, especially in the case of SF-amended soils, which rendered the highest K(oc) values. In soils amended with the liquid amendment LF, sorption either remained unaffected or decreased, and this decrease was much higher in the case of metalaxyl and a soil with 70% clay. In this clay soil, amendment with OW, of very high soluble organic matter content, also decreased metalaxyl sorption. Tricyclazole is more persistent in soil than metalaxyl, and both fungicides were found to be more persistent in amended soils than in unamended soils. Leaching of metalaxyl and tricyclazole in soil columns was inversely related to sorption capacity. The low recoveries of tricyclazole in leachates and in soil columns when compared with metalaxyl, a less persistent fungicide, were attributed to diffusion into micropores and to increase in sorption with residence time in the soil, both processes favoured by the low mobility of tricyclazole.

Adsorption↗
PubMed2001

Organoclays for controlled release of the herbicide fenuron.

Organoclays were assayed as matrices in which to associate herbicides, with the aim of decreasing product losses that could give rise to water contamination from agricultural activities. Fenuron was selected as model of a very mobile and highly water-soluble herbicide. Two different organoclays of high (A-HDT) and low (H-C18) reversible fenuron sorption were selected. Herbicide-organoclay complexes were prepared from the two organoclays and with two different fenuron contents (20 and 40 g AI kg-1) and two different mixing times, so as to form a series of weak and strong complexes. The release of fenuron from those complexes into water and water/soil suspensions gave values of T50 (time to release 50% of the fenuron content) ranging from 0.3 min to 2400 h. The total fenuron released in these closed systems ranged from 48 to 80% of the fenuron in the complex. The organoclay type (high or low sorptivity) had the greatest influence on fenuron release, followed by the strong or weak complex, suggesting that herbicide-organoclay interactions are the main factors controlling release. Soil column leaching experiments showed fenuron-organoclay complexes to be effective in reducing the peak herbicide concentration in the leachate to a half (6 microns) or a quarter (3 microns) of that obtained from the free technical compound (12 microns). Herbicide lost through leaching was reduced from 78% for the free technical fenuron to 50-30%, depending on the organoclay used as carrier and the strength of the complex. Bioassay with ryegrass showed that the weak fenuron/H-C18 complex (40 g AI kg-1) gave the same herbicidal activity as technical fenuron. The potential suitability of low-sorptive organoclays for conferring slow-release properties on the fenuron complex has been demonstrated.

Adsorption↗
PubMed2002

Lysimeter study to investigate the effect of rainfall patterns on leaching of isoproturon.

The influence of five rainfall treatments on water and solute leaching through two contrasting soil types was investigated. Undisturbed lysimeters (diameter 0.25 m, length 0.5 m) from a sandy loam (Wick series) and a moderately structured clay loam (Hodnet series) received autumn applications of the radio-labelled pesticide isoproturon and bromide tracer. Target rainfall plus irrigation from the end of November 1997 to May 1998 ranged from drier to wetter than average (235 to 414 mm); monthly rainfall was varied according to a pre-selected pattern or kept constant (triplicate lysimeters per regime). Leachate was collected at intervals and concentrations of the solutes were determined. Total flow (0.27-0.94 pore volumes) and losses of bromide (3-80% of applied) increased with increasing inputs of water and were larger from the Wick sandy loam than from the Hodnet clay loam soil. Matrix flow appeared to be the main mechanism for transport of isoproturon through the Wick soil whereas there was a greater influence of preferential flow for the Hodnet lysimeters. The total leached load of isoproturon from the Wick lysimeters was 0.02-0.26% of that applied. There was no clear variation in transport processes between the rainfall treatments investigated for this soil and there was an approximately linear relationship (r2 = 0.81) between leached load and total flow. Losses of isoproturon from the Hodnet soil were 0.03-0.39% of applied and there was evidence of enhanced preferential flow in the driest and wettest treatments. Leaching of isoproturon was best described by an exponential relationship between load and total flow (r2 = 0.62). A 45% increase in flow between the two wettest treatments gave a 100% increase in leaching of isoproturon from the Wick soil. For the Hodnet lysimeters, a 35% increase in flow between the same treatments increased herbicide loss by 325%.

Aluminum Silicates↗
PubMed2002

Environmental fate of metalaxyl and chlorothalonil applied to a bentgrass putting green under southern California climatic conditions.

Putting greens usually receive high inputs of fertilizers and pesticides to meet the high demand for visual quality and to overcome the stress from close mowing and traffic. In this study, two commonly used fungicides, metalaxyl (methyl N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate) and chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile), were evaluated for their partitioning and persistence in a bentgrass (Agrostis palustris Huds) putting green under southern California climatic conditions. The putting green site was constructed according to the US Golf Association (USGA) specifications. Lysimeter assemblies installed at the center of each plot were used to monitor the leachate, flux chambers were used to measure volatilization, clippings were collected to determine the residues on grass, and soil cores were sampled to determine residues in the soil profile. Results showed that cumulative volatilization loss accounted for 0.10 and 0.02%, clipping removal 0.11 and 0.13%, and cumulative leaching 0.71 and 0.002% of the applied metalaxyl and chlorothalonil, respectively. The two fungicides were mainly found in the top 10 cm of the soil profile due to the high organic carbon content in the thatch and mat layers. The dissipation half-life was 1.4 days for metalaxyl and 4.9 days for chlorothalonil on grass, shorter than those found in agricultural fields. This study showed that, under normal turf management practices, the offsite transport of the parent fungicides was minimal. Future research should focus on investigating the fate and mobility of the metabolites of the fungicides.

Adsorption↗
PubMed2002

Persistence and leaching of beta-cyfluthrin in alluvial soil of India.

Persistence as affected by rate of application and moisture regimes and leaching of beta-cyfluthrin was studied in alluvial soil under laboratory conditions. The effects of rate of application and moisture regimes on persistence were studied by incubating fortified soil at 0.1, 1.0 and 10.0 mg kg(-1) under air-dry, field capacity and submerged moisture regimes. The initial deposits of 0.09, 1.11 and 10.1 mg kg(-1) dissipated with time and 78.4-100% loss was recorded at 90 days. The half-life values varied from 7.8 to 41.8 days. The rate of dissipation decreased as the rate of application increased under field capacity and submerged conditions. However, under air-dry conditions, the effect was less pronounced, and half-life values showed a reverse trend. Persistence of beta-cyfluthrin under different moisture regimes followed the trend: air-dry > field capacity > submerged. The trend could be attributed to the effect of moisture on number and type of microbes. Leaching was studied in a packed soil column under saturated flow conditions. beta-Cyfluthrin was found to be highly immobile in alluvial soil. No residues were detected in any leachate fraction under the experimental conditions. In column soil, residues were detected at 0-10 cm depth and the major amount (>99%) was recovered from 0-5 cm depth. Although beta-cyfluthrin showed moderate persistence in alluvial soil, the possibility of its leaching to ground water is negligible as a result of its immobility.

Algorithms↗
PubMed2002

A refined method for the detection of baculovirus occlusion bodies in forest terrestrial and aquatic habitats.

A sensitive and efficient method was developed for the detection of genetically modified and wild-type baculovirus occlusion bodies (OB) in forest terrestrial and aquatic habitats. The protocol facilitates the analysis of a large number of samples collected and frozen to maintain viral integrity. Lyophilization was used to standardize the size of both field-collected soil samples and test substrates inoculated with OBs for the determination of minimum detection threshold. To simulate natural conditions, terrestrial test substrates were inoculated at a standardized moisture content determined using a soil pressure plate apparatus. OBs, extracted from lyophilized test substrates by washing, sieving and centrifugation, were subjected to alkaline lysis and viral DNA isolated using a purchased DNA purification kit. PCR amplified DNA was visualized using agarose gel electrophoresis. Minimum detection thresholds in terrestrial substrates were 10(3), 10(2), 10(2) and 10(1) OBs from 0.5 g of lyophilized L, F-H and mineral soil horizons, and 1.0 ml of leachate, respectively. Detection thresholds in aquatic substrates were 10(0) and 10(3) OBs from 1.0 ml of pond water and 1.0 g of bottom sediment, respectively.

Animals↗
PubMed2003

Sensitivity analyses for four pesticide leaching models.

Sensitivity analyses using a one-at-a-time approach were carried out for leaching models which have been widely used for pesticide registration in Europe (PELMO, PRZM, PESTLA and MACRO). Four scenarios were considered for simulation of the leaching of two theoretical pesticides in a sandy loam and a clay loam soil, each with a broad distribution across Europe. Input parameters were varied within bounds reflecting their uncertainty and the influence of these variations on model predictions was investigated for accumulated percolation at 1-m depth and pesticide loading in leachate. Predictions for the base-case scenarios differed between chromatographic models and the preferential flow model MACRO for which large but transient pesticide losses were predicted in the clay loam. Volumes of percolated water predicted by the four models were affected by a small number of input parameters and to a small extent only, suggesting that meteorological variables will be the main drivers of water balance predictions. In contrast to percolation, predictions for pesticide loss were found to be sensitive to a large number of input parameters and to a much greater extent. Parameters which had the largest influence on the prediction of pesticide loss were generally those related to chemical sorption (Freundlich exponent nf and distribution coefficient Kf) and degradation (either degradation rates or DT50, QTEN value). Nevertheless, a significant influence of soil properties (field capacity, bulk density or parameters defining the boundary between flow domains in MACRO) was also noted in at least one scenario for all models. Large sensitivities were reported for all models, especially PELMO and PRZM, and sensitivity was greater where only limited leaching was simulated. Uncertainty should be addressed in risk assessment procedures for crop-protection products.

Algorithms↗
PubMed2003

Modelling approaches to compare sorption and degradation of metsulfuron-methyl in laboratory micro-lysimeter and batch experiments.

Results of laboratory batch studies often differ from those of outdoor lysimeter or field plot experiments--with respect to degradation as well as sorption. Laboratory micro-lysimeters are a useful device for closing the gap between laboratory and field by both including relevant transport processes in undisturbed soil columns and allowing controlled boundary conditions. In this study, sorption and degradation of the herbicide metsulfuron-methyl in a loamy silt soil were investigated by applying inverse modelling techniques to data sets from different experimental approaches under laboratory conditions at a temperature of 10 degrees C: first, batch-degradation studies and, second, column experiments with undisturbed soil cores (28 cm length x 21 cm diameter). The column experiments included leachate and soil profile analysis at two different run times. A sequential extraction method was applied in both study parts in order to determine different binding states of the test item within the soil. Data were modelled using ModelMaker and Hydrus-1D/2D. Metsulfuron-methyl half-life in the batch-experiments (t1/2 = 66 days) was shown to be about four times higher than in the micro-lysimeter studies (t1/2 about 17 days). Kinetic sorption was found to be a significant process both in batch and column experiments. Applying the one-rate-two-site kinetic sorption model to the sequential extraction data, it was possible to associate the stronger bonded fraction of metsulfuron-methyl with its kinetically sorbed fraction in the model. Although the columns exhibited strong significance of multi-domain flow (soil heterogeneity), the comparison between bromide and metsulfuron-methyl leaching and profile data showed clear evidence for kinetic sorption effects. The use of soil profile data had significant impact on parameter estimates concerning sorption and degradation. The simulated leaching of metsulfuron-methyl as it resulted from parameter estimation was shown to decrease when soil profile data were considered in the parameter estimation procedure. Moreover, it was shown that the significance of kinetic sorption can only be demonstrated by the additional use of soil profile data in parameter estimation. Thus, the exclusive use of efflux data from leaching experiments at any scale can lead to fundamental misunderstandings of the underlying processes.

Adsorption↗
PubMed2005

Nitrogen-15 in NO3- characterises differently reactive soil organic N pools.

Intercropping with legumes is known to increase the plant-available nitrogen (N) in soil, but can also increase leaching of NO3- to the groundwater. To minimise NO3- leaching risks, knowledge of the N-release processes is essential, including an estimate of the contribution of legumes to total NO3- concentrations in soil. Our objectives were to answer the questions: (1) whether the presence of legume roots increases N mineralisation, and (2) whether the proportion of legume-derived N in NO3- could be calculated with the help of natural abundance 15N in NO3-. We sampled soil monoliths of a Medicago x varia Martyn monoculture in August 2004 and set up three treatments: 'disturbance' (sieved to <2 mm), 'disturbance-roots' (sieved to <2 mm and visible roots removed), and 'control' (left untreated). During an incubation period of 70 days, an N-free nutrient solution was leached through the samples weekly. In the leachates we measured total N, total organic carbon, NO3-, and NH4+ concentrations. Six of the 13 sampling dates were chosen for N isotope analysis in NO3-. Nitrate was separated as AgNO3. During the incubation, 3 to 6% of the initial total mass of total N (192 to 274 mg N) in soil was mineralised. Nitrogen mineralisation followed zero-order kinetics independent of treatments. Mineralisation rates decreased in the order control (day 70: 3.7 microg NO3-N (mg Ninitial)-1)>disturbance-roots (2.6 microg NO3-N (mg Ninitial)-1)>disturbance (1.9 microg NO3-N (mg Ninitial)-1), indicating that mineralisation of legume roots did not play a major role in N mineralisation. The delta15N values jumped from ca. 3 per thousand to ca. 8 per thousand after 2 weeks of incubation, which we attributed to the contribution of two N pools. An exponential two-pool model could not be fitted to the data. Legume-derived soil organic matter, SOM (pool 1), was mineralised at the same rate as SOM accumulated before establishment of the legumes (pool 2). Fresh legume roots did not contribute significantly to N mineralisation.

Fabaceae↗
PubMed2003

Cyst-based toxicity tests XV--application of ostracod solid-phase microbiotest for toxicity monitoring of contaminated soils.

A new "culture/maintenance-free" microbiotest has recently been developed for "direct-contact" toxicity determination of contaminated sediments. The 6-day Ostracodtoxkit F makes use of the neonates of the ostracod crustacean Heterocypris incongruens hatched from dormant eggs (cysts). The new low-cost assay has already been applied in three studies on river sediment from Flanders (Belgium) and from Canada and was found to perform comparably to the 10-day Hyalella azteca and Chironomus riparius tests in detecting and quantifying sediment toxicity. Taking into account that sediments are in fact underwater soils, the ostracod microbiotest was tentatively applied on 15 contaminated soils from Flanders (Belgium), and its sensitivity (based on mortality as the test criterion) was evaluated in comparison to the 28-day reproduction inhibition assay with the springtail Folsomia candida. The results revealed that the ostracod test species was as sensitive as or, in several samples, even more sensitive than the springtails. Leachate experiments on the same soil samples also showed that in most cases ostracod mortality was a result of the (nonsoluble) toxicants bound to the solid-phase particles, rather than of those that had dissolved in the water phase. Providing confirmation of these first findings through additional studies, the new culture/maintenance-free ostracod microbiotest seems to have good potential as a low-cost and user-friendly tool for routine toxicity monitoring of contaminated soils.

Amphipoda↗
PubMed1998

Degradation of 2-nitrodiphenylamine, a component of Otto Fuel II, by Clostridium spp.

Otto Fuel II, a propellant in torpedoes, is composed of 76% 1,2 propanediol dinitrate (PGDN), 22.5% di-n-butyl sebacate, and 1.5% 2-nitrodiphenylamine (NDPA), and is largely recalcitrant to aerobic microbial degradation. Anaerobic microbial degradation of Otto Fuel II was tested by inoculating anaerobic enrichment media, containing either 2% (vol:vol) complete Otto Fuel II or 2% of a 0.02% solution of Otto Fuel II in methanol, with soil and water from sites contaminated with munitions or with landfill leachate. Anaerobic bacterial growth was completely inhibited by 2% Otto Fuel II. Two mixed bacterial enrichments developed in anaerobic media containing 2% (v/v) of a 0.02% solution of Otto Fuel II in methanol. After incubation, PGDN could not be detected in either enrichment, but was also not detectable in sterile controls, suggesting abiotic degradation of low concentrations of PGDN in reduced anaerobic medium. NDPA did not degrade in either enrichment. Similarly, complete Otto Fuel was recalcitrant to degradation by highly reducing methanogenic biomass collected from an upflow anaerobic sludge blanket bioreactor (UASB). A comparison of the degradative ability of autoclaved and viable biomass showed that low concentrations of PGDN autodegraded, however unlike the autoclaved anaerobic biomass, the viable anaerobic biomass degraded the NDPA component of Otto Fuel II. Two strains of anaerobic clostridia, strains SP3 and SPF, that caused the disappearance of NDPA at its limit of solubility in culture media, were isolated from the UASB bioreactor biomass. SP3 and SPF were shown, by comparison of 16S rDNA sequences, to be most closely related to Clostridium butyricum and Clostridium cochlearium respectively. Although NDPA was lost from cultures of both strains, metabolic end products were not identified. Neither strain could degrade NDPA unless supplied with an alternative energy source. In the culture system used, NDPA stimulated the growth of SP3 but it had no appreciable effect on the growth of SPF. Both SP3 and SPF degraded low concentrations of trinitrotoluene (TNT), without the production of detectable concentrations of aromatic amines. A possible method for the remediation of small spills of Otto Fuel II is suggested.

Journal Article↗
PubMed1994

Dissipation and movement of acaricide chlorobenzilate in the environment.

The dissipation of acaricide chlorobenzilate in selected soil and river water samples was studied. Under incubation conditions at 25 degrees C and 90% field capacity of moisture for 21 days, the residues of chlorobenzilate were 14 and 55% in Lukang silty clay loam and Pincheng clay, respectively. More than 80% of chlorobenzilate remained in the natural water (pH 7.2 and 7.3, respectively) and in the water adjusted to pH 5.0 when water samples collected from Green Lake and Wai-Shuang River near Taipei were treated with chlorobenzilate and then incubated for 34 days. But when the pH was adjusted to 9.0, only 60% was found in Green Lake water and 29% in Wai-Shuang River water. The dissipation of chlorobenzilate in the soil was fitted to first-order kinetics with half-lives of 5 to 36 days under various conditions in the laboratory experiments. No chlorobenzilate was detected in the leachate by a leaching experiment on the soil column for 18 days; most chlorobenzilate remained in the upper 3 cm of the column. According to assessment by the groundwater pollution-potential model (GWP), chlorobenzilate seemed to be safe in regard to groundwater contamination.

Benzilates↗
PubMed1998

Trifluralin transfer from top soil.

Leaching of 14C-ring-labeled technical trifluralin from the top 5 cm of soil was followed in a microlysimeter experiment under outdoor conditions. Leaching of water residues from soil was low and represented 2.2, 5.4, and 6.7% of the applied radioactivity after 6, 12, and 18 months, respectively. Two degradation products, called A and B, were clearly detected and represented about 80 and 10% of the leached radioactivity, respectively, whereas other degradation products accounted for about 10%. Trifluralin itself was detected in the leachate only between 3 and 6 months. Cumulated amounts of leached trifluralin were only 1% of the leached radioactivity after 1 year: i.e., 0.06% of the applied product. A second-year microlysimeter experiment demonstrated that the use of formulated trifluralin had no influence on leached amount and content.

Carbon Radioisotopes↗