Enhanced degradation of carbofuran in Pacific Northwest soils

Persistence of 14C-carbonyl carbofuran was measured in Pacific Northwest soils that had received 1-14 applications of the insecticide for root weevil control on perennial crops. Insecticide decay curves were obtained in nonautoclaved soil and several autoclaved soil samples from previously-treated fields and in nonautoclaved soils from paired control sites not previously treated with carbofuran. The insecticide usually degraded faster in soil from previously-treated fields than in soil from corresponding control fields. Among 26 previously-treated fields, the pseudo half-life (time for 50% loss) of carbofuran was less than one wk in 11 soils, 1-3 wks in 8 soils and greater than 4 wks in the remaining soils. Among the nontreated control fields the pseudo half-life was greater than 2 wks in all cases and greater than 15 wks in 5 of the soils. The carbofuran decay curve always possessed an initial lag phase where soil mixing enhanced insecticide decline. Carbofuran degraded very slowly in autoclaved soil samples. The half-life of carbofuran exceeded 16 wk in all autoclaved soils tested and in most instances 85-90% of the original dosage remained when the tests were terminated 112 days after treatment. These results provided evidence that many of the soils which received applications of carbofuran over the past several years have developed a capacity to degrade carbofuran very rapidly.     

A comparison of the persistence in a clay loam of single and repeated annual applications of seven granular insecticides used for corn rootworm control

In May 1983, granular formulations of carbofuran, chlorpyrifos, disulfoton, fonofos, isofenphos, phorate, and terbufos were applied in incorporated bands to duplicate 2 m2 field plots of clay loam. Insecticide concentrations were determined in the bands at 0,1,2,3,4,6,8,10,12,16, and 20 wk. Following spring cultivation, the insecticides were applied to the same plots in 1984 and 1985. In addition, carbofuran was applied to previously untreated plots in 1984 and all 7 materials were applied to previously untreated plots in 1985. Sampling and analysis were carried out as in 1983. Persistence was assessed on the basis of the disappearance rates measured for the 1st 8 wk and of a calculated Effectiveness Potential (the ratio of the average residue in the upper 5 cm of the band at 8, 10 and 12 wk and the published LC95 for western corn rootworm in clay loam soil). Soils treated with carbofuran and isofenphos in 1984 and all soils treated in 1985 were tested for anti-insecticide activity. Soil cores from some carbofuran, chlorpyrifos and terbufos treated plots were sectioned vertically to establish the distribution of the insecticides during 1985. In addition, granular and pure chemical forms of isofenphos and carbofuran were applied at 10 ppm to anti-isofenphos and anti-carbofuran active and control soils (from field plots) maintained at 10 and 20% moisture in the laboratory to assess the effect of formulation and moisture on persistence in active soils. Insecticide concentrations were determined at 0,1,3,7, 10,14,21,28, and 35 days. The persistence of chlorpyrifos, terbufos and phorate was relatively constant over the 3 years and between plots receiving single and multiple treatments. Disulfoton and fonofos behavior was more variable and that of carbofuran and isofenphos was extremely variable. Anti-insecticide activity against carbofuran and isofenphos was detectable 2 wk after an initial application and was still present the following spring. Anti-insecticide activity against fonofos, terbufos sulfoxide, phorate sulfone and disulfoton sulfone was also generated in this soil. Anti-insecticide activity against chlorpyrifos, disulfoton, terbufos and phorate was not present. Carbofuran, chlorpyrifos and terbufos (+ metabolites) present in the upper 5 cm of soil averaged 93, 94 and 94%, respectively, of the total core contents over 12 wk. Significant moisture dependent differences were observed between the behavior of granular carbofuran and granular isofenphos in anti-insecticide active soils.(ABSTRACT TRUNCATED AT 400 WORDS)     

Enhanced degradation of carbofuran in pacific northwest soils

Abstract

Persistence of ¹⁴C‐carbonyl carbofuran was measured in Pacific Northwest soils that had received 1–14 applications of the insecticide for root weevil control on perennial crops. Insecticide decay curves were obtained in nonautoclaved soil and several autoclaved soil samples from previously‐treated fields and in nonautoclaved soils from paired control sites not previously treated with carbofuran. The insecticide usually degraded faster in soil from previously‐treated fields than in soil from corresponding control fields. Among 26 previously‐treated fields, the pseudo half‐life (time for 50% loss) of carbofuran was < one wk in 11 soils, 1–3 wks in 8 soils and > 4 wks in the remaining soils. Among the nontreated control fields the pseudo half‐life was > than 2 wks in all cases and > than 15 wks in 5 of the soils. The carbofuran decay curve always possessed an initial lag phase where soil mixing enhanced insecticide decline. Carbofuran degraded very slowly in autoclaved soil samples. The half‐life of carbofuran exceeded 16 wk in all autoclaved soils tested and in most instances 85–90% of the original dosage remained when the tests were terminated 112 days after treatment. These results provided evidence that many of the soils which received applications of carbofuran over the past several years have developed a capacity to degrade carbofuran very rapidly.     

Residues of chlorpyrifos-methyl in balsam fir foliage, forest litter, soil, stream water, sediment and fish tissue after double aerial applications of Reldan

Chlorpyrifos-methyl was applied twice at 70 g A.I./ha by means of a fixed-wing aircraft to a mixed coniferous forest near Allardville, New Brunswick. Residue in balsam fir foliage was highest (1 ppm wet wt) 1 hr after spraying and rapidly declined to about 30% within 1 day, but persisted at a very low level (0.03 ppm wet wt) for 125 days. Current year's foliage contained a higher level of residue than old foliage. Chlorpyrifos-methyl persisted longer in forest litter than in soil. After 125 days, trace amounts (less than 6 ppb wet wt) were still found in litter but were not detected in soil. In stream water the residue dissipated very rapidly; more than 90% disappeared 3 hours after the second application and were not detected after 4 days. Low-level residue (less than 0.1 ppm wet wt) was present in the sediment and persisted for 10 days. Although brook trout and slimy sculpin captured in the stream within 3 days of the second application contained residues (less than 0.05 ppm fresh wt) none were detected in any fish captured, 9 and 47 days later.     

Trace elements in soil and biota in confined disposal facilities for dredged material

We studied the relation of trace element concentrations in soil to those in house mice (Mus musculus), common reed (Phragmites australis) and ladybugs (Coccinella septempunctata at five disposal facilities for dredged material. The sites had a wide range of soil trace element concentrations, acid soils and a depauperate fauna. They were very poor wildlife habitat because they were dominated by the common reed. Bioassay earthworms exposed to surface soils from three of the five sites died, whereas those exposed to four of five soils collected a meter deep survived, presumably because the deeper, unoxidized soil, was not as acid. Concentrations of Ni and Cr in the biota from each of the sites did not seem to be related to the concentrations of the same elements in soil. Although Pb, Zn and Cu concentrations in biota were correlated with those in soil, the range of concentrations in the biota was quite small compared to that in soil. The concentrations of Pb detected in mice were about as high as the concentrations previously reported in control mice from other studies. Mice from the most contaminated site (530 ppm Pb in soil) contained only slightly more Pb (8 ppm dry wt) than did mice (2-6 ppm dry wt) from sites containing much less Pb (22-92 ppm in soil). Despite the acid soil conditions, very little Cd was incorporated into food chains. Rather, Cd was leaching from the surface soil. We concluded that even the relatively high concentrations of trace elements in the acid dredged material studied did not cause high concentrations of trace elements in the biota.     

A comparative study on the dissipation and microbial metabolism of organophosphate and carbamate insecticides in orchaqualf and fluvaquent soils of West Bengal

An experiment has been conducted under laboratory conditions to investigate the effect of phorate (an organophosphate insecticide) and carbofuran (a carbamate insecticide) at their recommended field rates (1.5 and 1.0 kga.i.ha-1, respectively) on the growth and multiplication of microorganisms as well as rate of dissipation and persistence of the insecticidal residues including their metabolites in laterite (typic orchaqualf) and alluvial (typic fluvaquent) soils of West Bengal. Application of phorate and carbofuran in general, induced growth and development of bacteria, actinomycetes, fungi, N2-fixing bacteria and phosphate solubilizing microorganisms in both the soils and the stimulation was more pronounced with phorate as compared to carbofuran. Application of phorate recorded highest stimulation of fungi in laterite and actinomycetes in alluvial soil. Carbofuran on the other hand, augmented fungi and N2-fixing bacteria in laterite and actinomycetes in alluvial soil. Bacterial population was inhibited due to the application of carbofuran in alluvial soil. Phorate sulfoxide and phorate sulfone, the two metabolites of phorate and 3-hydroxycarbofuran and 3-ketocarbofuran, the two metabolites of carbofuran isolated were less persistent in both the soils. Phorate persisted in laterite and alluvial soils up to 45 and 60 days, respectively depicting the half-life (T1/2) 9.7 and 11.5 days, respectively while the T1/2 of carbofuran for the said soils were 16.9 and 8.8 days, respectively. No metabolite of carbofuran was detected in soils after 30 days of incubation while phorate sulfone persisted in alluvial soil even after 60 days of application of the insecticide.     

Distribution and availability of arsenic in soils from the industrialized urban area of Beijing, China

Concentrations of arsenic (As) were determined in soils of 5 industrial sites in an urban area of Beijing, China. Fifty seven typical surface soils were sampled to determine total concentrations of metals, pH and dissolved organic carbon (DOC). One hundred and eight deep soils were submitted to a four-step, sequential extraction to assess the relative mobility and bioavailability of As in the soil profiles. Total concentrations of As in surface soils ranged from 5.7 to 2.3 x 10(1) mg kg(-1), dw with greater concentrations inside the perimeter of the chemical plant which had greater concentrations than did other plants. 75.4% of surface soil samples in the industrial area contained concentrations of As that were greater than was considered to be the background concentration of 7.8 mg kg(-1), dw for the region. The mean concentration (9.9 mg kg(-1), dw) in the industrial soils was greater than that soils from other type of land use. Concentrations of As were significantly and negatively correlated with soil pH and DOC in industrial soils. Although mean concentration of total As in the soils from all sites were less at greater depths, the entire range from 0 to 180 cm (especially 0-80 cm) contained concentrations of As that were greater than background. Sequential extractions of soil indicated that only some surface soils had relatively great amount of extractable fraction of As. Most soils had relatively great amount of residual As. This result suggests that most arsenic in Beijing industrial soils should be immobile and of limited bioavailability.     

Residues of chlorpyrifos‐methyl in balsam fir foliage,forest litter,soil, stream water,sediment and fish tissue after double aerial applications of Reldan®

Abstract

Chlorpyrifos‐methyl was applied twice at 70 g A.I./ha by means of a fixed‐wing aircraft to a mixed coniferous forest near Allardville, New Brunswick. Residue in balsam fir foliage was highest (1 ppm wet wt) 1 hr after spraying and rapidly declined to about 30% within 1 day, but persisted at a very low level (0.03 ppm wet wt) for 125 days. Current year's foliage contained a higher level of residue than old foliage. Chlorpyrifos‐methyl persisted longer in forest litter than in soil. After 125 days, trace amounts (< 6 ppb wet wt) were still found in litter but were not detected in soil. In stream water the residue dissipated very rapidly; more than 90% disappeared 3 hours after the second application and were not detected after 4 days. Low‐level residue (< 0.1 ppm wet wt) was present in the sediment and persisted for 10 days. Although brook trout and slimy sculpin captured in the stream within 3 days of the second application contained residues (< 0.05 ppm fresh wt) none were detected in any fish captured, 9 and 47 days later.     

Comparison of batch, stirred flow chamber, and column experiments to study adsorption, desorption and transport of carbofuran within two acidic soils

Different methods (batch, column and stirred flow chamber experiments) used for adsorption and desorption of carbofuran studies were compared. All tested methods showed that the carbofuran adsorption was higher in the soil with the higher organic matter content, whereas the opposite behaviour was observed for the percentage of carbofuran desorbed. However, different methods have revealed some discrepancies in carbofuran adsorption/desorption kinetics. Although batch method showed interesting data on equilibrium experiments, such as a low heterogeneity for the carbofuran adsorption sites independent of soil organic matter content, it had some disadvantages for carbofuran adsorption/desorption kinetic studies. The disadvantages were related with the excessive limitations of this method on kinetics, i.e., no difference could be detected between different soils. However, with column and stirred flow chamber methods the carbofuran adsorption/desorption kinetics of different soils could be compared. Moreover, the absolute values of carbofuran adsorption/desorption and its rate were higher in the stirred flow chamber than in the batch and column experiments. Using stirred flow chamber experiments the carbofuran desorption was significantly faster than its adsorption, whereas carbofuran using column experiments they were similar. These discrepancies should be considered when the results obtained only with one method is discussed.     

Carbofuran degradation in soil profiles

Abstract

Two soils, Puyallup fine sandy loam from Puyallup, WA, and Ellzey fine sand from Hastings, FL, each with a prior history of carbofiiran exposure but with different pedological and climatological characteristics, were found to exhibit enhanced degradation toward carbofiiran in surface and subsurface soil layers. The treated Puyallup and Ellzey soils exhibited higher mineralization rates for both the carbonyl and the aromatic ring of carbofiiran when compared to untreated soils. Disappearance rates of [¹⁴C‐URL (uniformly ring labeled)] carbofiiran in the treated Ellzey soil was faster than in untreated soil, and also faster in surface soil than in subsurface soil. Initial degradation patterns in the treated Ellzey soil were also different from those in the untreated soil. The treated Ellzey soil degraded carbofuran mainly through biological hydrolysis, while untreated soil degraded carbofuran through both oxidative and hydrolytic processes.     

Effects of conditioning,cross‐conditioning,and microbial growth on development of enhanced biodegradation of insecticides in soil

Abstract

Pretreatment of a Drummer‐Catlin soil mixture with granular formulations of carbofuran or trimethacarb enhanced biodegradation of subsequent treatments with the technical formulations. Degradation of carbofuran was enhanced by pretreatments with trimethacarb, and degradation of trimethacarb was enhanced by pretreatments with carbofuran. Bendiocarb degradation was enhanced by pretreatments of soil with carbofuran or trimethacarb. In bioassays with southern corn rootworm larvae, biological activity of carbofuran, trimethacarb, and bendiocarb was rapidly lost in soils pretreated with granular formulations. Pretreatment of soil with granular terbufos did not enhance the biodegradation of subsequent applications of technical terbufos. Several microbial biomass assays showed an increase in specific carbofuran‐degrading bacteria in soils that were pretreated with carbofuran. Bacteria were isolated that could grow on carbofuran and apparently degrade it when present with another carbon source.     

Residues of carbosulfan and its metabolites carbofuran and 3-hydroxy carbofuran in rice field ecosystem in China

The fate of carbosulfan (seed treatment dry powder) was studied in rice field ecosystem, and a simple and reliable analytical method was developed for determination of carbosulfan, carbofuran, and 3-hydroxyl carbofuran in brown rice, rice straw, paddy water, and soil. The target compounds were extracted using acetonitrile or dichloromethane, cleaned up on acidic alumina or florisil solid phase extraction (SPE) cartridge, and analyzed by gas chromatography. The average recoveries of carbosulfan, carbofuran and 3-hydroxy carbofuran in brown rice, rice straw, paddy water, and soil ranged from 72.71% to 105.07%, with relative standard deviations of 2.00–8.80%. The limits of quantitation (LOQs) of carbosulfan, carbofuran and 3-hydroxy carbofuran in the samples (brown rice, rice straw, paddy water and soil) were 0.011, 0.0091, 0.014, 0.010 mg kg^?1, 0.016, 0.019, 0.025, 0.013 mg kg^?1, and 0.031, 0.039, 0.035, 0.036 mg kg^?1, respectively. The trials results showed that the half-lives of carbosulfan, carbofuran and 3-hydroxy carbofuran in rice straw were 4.0, 2.6 days, 3.9, 6.0 days, and 5.8, 7.0 days in Zhejiang and Hunan, respectively. Carbosulfan, carbofuran and 3-hydroxy carbofuran were detected in soils. Carbosulfan and 3-hydroxy carbofuran were almost undetectable in paddy water. Carbofuran was detected in paddy water. The final residues of carbosulfan, carbofuran and 3-hydroxy carbofuran in brown rice were lower than 0.05 mg kg^?1, which were lower than 0.5 mg kg^?1 (MRL of carbosulfan) or 0.1 mg kg^?1 (MRL of carbofuran). Therefore, a dosage of 420 g active ingredient per 100 kg seed was recommended, which could be considered as safe to human beings and animals. These would contribute to provide the scientific basis of using this insecticide.     

Influence and persistence of phorate and carbofuran insecticides on microorganisms in rice field

An experiment was conducted in microplots (4 m x 4 m) with two insecticides, phorate and carbofuran at rates of 1.5 and 1.0 kga.i.ha(-1) respectively, to investigate its effect on the population and distribution of bacteria, actinomycetes and fungi as well as the persistence of the insecticidal residues in rhizosphere soils of rice (Oryza sativa L., variety IR-50). Application of the insecticides stimulated the population of bacteria, actinomycetes and fungi in the rhizosphere soils, and the stimulation was more pronounced with phorate as compared to carbofuran. Both the insecticides did not have marked effect on the numbers of Streptomyces and Nocardia in the rhizosphere soils. However, the growth of Bacillus, Escherichia, Flavobacterium, Micromonospora, Penicillium, Aspergillus and Trichoderma with phorate and that of Bacillus, Corynebacterium, Flavobacterium, Aspergillus and Phytophthora with carbofuran were increased. On the other hand, the numbers of Staphylococcus, Micrococcus, Fusarium, Humicola and Rhizopus under phorate and Pseudomonas, Staphylococcus, Micrococcus, Klebsiella, Fusarium, Humicola and Rhizopus under carbofuran were inhibited. Both the insecticides persisted in the rhizosphere soil for a short period of time and the rate of dissipation of carbofuran was higher than that of phorate in the soil depicting the half-life (T1/2) 9.1 and 10.4 days, respectively.     

Heavy metals in urban soils of East St. Louis, IL, Part I: Total concentration of heavy metals in soils

The city of East St. Louis, IL, has a history of abundant industrial activities including smelters of ferrous and non-ferrous metals, a coal-fired power plant, companies that produce organic and inorganic chemicals, and petroleum refineries. A protocol for soil analysis was developed to produce sufficient information on the extent of heavy metal contamination in East St. Louis soils. Soil cores representing every borough of East St. Louis were analyzed for heavy metals--As, Cd, Cu, Cr, Hg, Ni, Pb, Sb, Sn, and Zn. The topsoil contained heavy metal concentrations as high as 12.5 ppm Cd, 14,400 ppm Cu, ppm quantities of Hg, 1860 ppm Pb, 40 ppm Sb, 1130 ppm Sn, and 10,360 ppm Zn. Concentrations of Sb, Cu, and Cd were well correlated with Zn concentrations, suggesting a similar primary industrial source. In a sandy loam soil from a vacated rail depot near the bank of the Mississippi River, the metals were evenly distributed down to a 38-cm depth. The clay soils within a half-mile downwind of the Zn smelter and Cu products company contained elevated Cd (81 ppm), Cu (340 ppm), Pb (700 ppm), and Zn (6000 ppm) and displayed a systematic drop in concentration of these metals with depth. This study demonstrates the often high concentration of heavy metals heterogeneously distributed in the soil and provides baseline data for continuing studies of heavy metal soil leachability.     

The effect of fonofos and carbofuran on microbiological population, and persistence of fonofos in four organic soils infested with onion maggot

One hundred days after field-application of fonofos as bands under the onion seed, 39 to 59% of that material was present in 3 moderately humified organic soils of pH varying from 5.4 to 6.7. In a low humified organic soil, only 21 to 24% of the applied fonofos remained. Thus humus enhanced the persistence of fonofos and curtailed the stimulating effect of fonofos on soil microbial populations. An assessment of low damage caused by onion maggot was found in a poorly humified soil with an even higher natural infestation than in a moderately humified soil. The effects of fonofos in other soils and of the low rate of carbofuran applied to four different types of soils on the numbers of fungi, bacteria, and actinomycetes were difficult to assess.     

Modelling the fate of organic chemicals in the soil plant environment: Model study of root uptake of pesticides

The fate of organic chemicals in the soil-plant-atmosphere environment and the governing processes were studied with a coupled dynamic soil transport and plant compartment model. Scenarios with applications of pesticides on sand and loam soils with chemical uptake in barley and wheat were used in the model calculations. Root uptake and concentrations in the plant compartments stem, leave and fruit were calculated for the pesticides terbuthylazine, isoproturon and carbofuran.

The effectivity of uptake from soils with different soil sorption coefficients had been shown for sand and loam soils. The processes degradation in plant and volatilization from leaves to atmosphere are especially effective for carbofuran and terbuthylazine. Although the concentrations in corn at harvest are lower than the maximum allowed concentrations, the peak concentrations in the course of the vegetation period are significantly higher (factor ≤ 200).     

Heavy Metals in Urban Soils of East St. Louis,IL, Part I: Total Concentration of Heavy Metals in Soils

ABSTRACT

The city of East St. Louis, IL, has a history of abundant industrial activities including smelters of ferrous and non-ferrous metals, a coal-fired power plant, companies that produce organic and inorganic chemicals, and petroleum refineries. A protocol for soil analysis was developed to produce sufficient information on the extent of heavy metal contamination in East St. Louis soils. Soil cores representing every borough of East St. Louis were analyzed for heavy metals—As, Cd, Cu, Cr, Hg, Ni, Pb, Sb, Sn, and Zn. The topsoil contained heavy metal concentrations as high as 12.5 ppm Cd, 14,400 ppm Cu, ppm quantities of Hg, 1860 ppm Pb, 40 ppm Sb, 1130 ppm Sn, and 10,360 ppm Zn. Concentrations of Sb, Cu, and Cd were well correlated with Zn concentrations, suggesting a similar primary industrial source. In a sandy loam soil from a vacated rail depot near the bank of the Mississippi River, the metals were evenly distributed down to a 38-cm depth. The clay soils within a half-mile downwind of the Zn smelter and Cu products company contained elevated Cd (81 ppm), Cu (340 ppm), Pb (700 ppm), and Zn (6000 ppm) and displayed a systematic drop in concentration of these metals with depth. This study demonstrates the often high concentration of heavy metals heterogeneously distributed in the soil and provides baseline data for continuing studies of heavy metal soil leachability.     

Characterization and growth response of bacteria in soil following application of carbofuran.

Enhanced biodegradation of carbofuran (2, 3-dihydro-2, 2 dimethyl-7-benzofuranyl methyl carbamate) is an economically significant, but poorly understood, microbial phenomenon in soil. A series of experiments was conducted to examine short term changes in soil bacterial populations stimulated by carbofuran application at field rates. In the field experiment, commercially formulated carbofuran and butylate (S-ethyl diisobutyl carbamothioate) were applied at 5.6 kg ai ha-1 and 8.4 kg ai ha-1, respectively, on a soil (Putnam silt loam) exhibiting enhanced degradation of carbofuran. In laboratory studies, technical grade carbofuran (20 mg kg-1 soil) was applied to samples of the field soil. Bacterial populations were estimated using non-selective (tryptic soy agar) and selective media containing carbofuran or butylate. Largest population increases in pesticide-treated soil were observed between 7 and 15 days after treatment (DAT) compared to populations in non-treated soil. Significant increases (P less than 0.05) in total bacterial populations and presumed carbofuran-degraders due to carbofuran application were associated with increased populations of Pseudomonas spp. and Flavobacterium spp. Application of carbofuran appeared to provide a competitive advantage to these species over actinomycetes persisting beyond 20 DAT. Growth responses of bacteria to carbofuran in the Putnam soil were compared to those in a native prairie soil (Mexico silt loam), which exhibited a much slower rate of carbofuran degradation. Bacterial population response to carbofuran was measurable, but small and short-lived. Perpetuation of the enhanced degradation phenomenon may lie in a persistent pesticide-induced competitive advantage given to a very small segment of the microbial population. This advantage may not be detectable after 20 days using conventional plating techniques.     

Fenvalerate concentrations in a mineral and an organic soil receiving multiple applications during the growing season

Abstract

Fenvalerate EC at 140 g AI/ha was applied 7 times at 2 wk intervals to duplicate plots of Plainfield sand and an organic soil contained in 2.2 x 0.9 m field microplots with and without an onion crop present in 1980 and 1981 respectively. Soil samples were taken immediately before and after each application and at 2, 4, and 6 wk after the last application in 1980. Additional samples were taken at 22 and 34 wk for the 1981 treatment. Concentrations of fenvalerate were determined by glc. In the crop‐free mineral soil, fenvalerate levels declined from. 0.07–0.11 ppm immediately after spraying to 0.01–0.03 ppm after 2 wk; in the organic soil the rate of addition of fenvalerate exceeded the rate of disappearance and the concentration in the soil gradually increased over the 14 wk treatment period to the 0.9–1.0 ppm range. This concentration decreased slowly over the next 10 wk to 0.7–0.8 ppm and was still 0.5–0.7 ppm the following spring. Results were similar for cropped soils. Concentrations in the top third of the 15 cm cores were 6x and 15x those in the middle third for sand and organic soil, respectively. Concentrations, in the onions at harvest were <0.01 ppm.     

Distribution and persistence of carbaryl in some terrestrial and aquatic components of a forest environment

Abstract

An oil‐based formulation of carbaryl (1‐naphthyl N‐methyl‐carbamate) (Sevin‐2‐Oil) was applied twice by a fixed‐wing aircraft at a dosage rate of 280 g of A.I./ha/application to a coniferous forest near Allardville, New Brunswick. The highest concentrations of the chemical in fir foliage, litter and forest soil 1 h after application were respectively 4.20, 1.21 and 0.59 ppm (fresh weight). The residues dissipated rapidly and the DT50 values obtained from the depletion curves were 2.3 d for foliage and 1.5 d for litter and soil samples. Very low levels (<0.1 ppm) of carbaryl persisted in foliage and litter beyond the 10 d sampling period. The maximum residue level found in stream water was 0.314 ppm and more than 50% of it had dissipated within 1 h. Low but detectable levels (0.001 ppm) of the chemical persisted in water until the end of the 10 d sampling period. Sediment samples contained a maximum level of 0.04 ppm, which dissipated below the detection limit within 5 h. Brook trout and slimy sculpins captured in the stream 1 d after the spray contained on average about 0.04 ppm of carbaryl and none of it was found in 3 d postspray samples.