Metabolic fate of [14C]endrin in bluegill fish

Bluegill absorbed 85% of 1 ppb of endrin from water within 48 hr under static exposure conditions. The absorbed radiocarbon was eliminated linearly with a half-life of about 4 weeks. Analyses of eliminated radioactivity revealed only conjugated metabolites. 12-anti-Hydroxyendrin and 12-syn-hydroxyendrin were tentatively identified by cochromatography using thin-layer chromatography/autoradiography and gas chromatography. These metabolites were also present as conjugates in the fish organs. Seventy-three percent of the absorbed radioactivity recovered from fish extracts was in the form of unchanged endrin.     

Metabolic fate of [14C]photodieldrin in goldfish

Goldfish (Carassius auratus) exposed to 20 parts per billion [¹⁴C]photodieldrin in a static system absorbed 80% of the radioactivity within 20 hr. The absorbed radioactivity was eliminated slowly with a half-life of 3 weeks. Photodieldrin and a ketone derivative were the major form of the radiocarbon eliminated in water, accounting for, respectively, 59 and 10.4% of the eliminated radioactivity. The ketone derivative was characterized by cochromatography (thin-layer and gas chromatography, gc) and gc-mass spectrometry. Approximately, 15 other polar and nonpolar metabolites were detected in the aqueous medium. The radioactivity in the fish consisted of 13 metabolites along with photodieldrin. Photodieldrin and the ketone derivative were the most abundant residues in the fish, accounting for 77 and 5.4% of the radioactivity, respectively.     

Metabolism of [14C]dieldrin in bluegill fish

The exposure of bluegill fish to 50 parts per billion [¹⁴C]dieldrin in a static system resulted in the absorption of 73.00% of the radioactivity in 48 hr. Following transfer of the fish to clean water, only 16.20% of the absorbed radiolabel was eliminated in 23 days. Out of the 93.65% of the absorbed radioactivity recovered, 9 radioactive spots were isolated which included unchanged dieldrin (74.39%), pentachloroketone (8.17%), and aldrin-trans-diol (8.04%) as major metabolites.     

Uptake and translocation of [14C]asulam and [14C]bromacil by roots of maize and bean plants

The uptake and translocation of ¹⁴C-ring-labeled asulam (methylsulfanilcarbamate) and bromacil (5-bromo-3-sec-butyl-6-methyluracil), were compared after root application to maize (Zea mays L.) and bean (Phaseolus vulgaris L.). Autoradiographs showed the distribution of bromacil throughout these and other plant species, and the retention of asulam in the roots. The recovery of both compounds in quantitative radioassays was between 90 and 100%. The absorption of bromacil and asulam was rather similar. Absorption of bromacil increased up to 20% of the applied dose in bean plants after 2 days of exposure, and up to 11% in maize plants after 4 days. Absorption of asulam in bean plants was 22% of the applied dose after 2 days, and 8% in maize plants after 4 days. The pattern of distribution of bromacil and asulam was completely different. After 4 h of exposure of the roots about half of the absorbed bromacil had accumulated in the shoots, while two-thirds or more was translocated to the shoots after exposure periods of 1 to 4 days. Not more than one-eighth of the absorbed asulam was found in the shoots. In consequence, the bromacil content in the transpiration stream relative to that in the ambient solution was much higher than that of asulam. The leakage of asulam from bean and maize roots into herbicide-free nutrient solution was lower than that of bromacil. The reasons for these differences are not yet clear. There was only some metabolism of asulam in maize, but not in bean plants. No metabolites of bromacil were detected in the two plant species.     

Metabolism of [14C]vernolate in soybeans

Penetration and metabolism of [¹⁴C]vernolate in soybean [Glycine max (L.) Merr. var Ransom] pods and seeds were measured 0, 1, 4, 24, 48, or 72 hr after treatment which occurred at 40 days after flowering. Total ¹⁴C recovery decreased ca. 50% within 4 hr and the loss of ¹⁴C was considered to be a measure of volatility. Total nonpolar extractants decreased in a logarithmic pattern which approached 10% of total ¹⁴C recovered within 24–48 hr. Total polar extractants increased in a logarithmic pattern to a maximum of 90% of total ¹⁴C recovered within 24 hr. Seed nonpolar extractants never exceeded 2% of the total ¹⁴C recovered while pod nonpolar extractants consisted of vernolate plus an unidentified component that did not thin-layer chromatograph (TLC) as the sulfone or sulfoxide. Pod polar extractants increased with time to ca. 75% of the total ¹⁴C recovered (24–48 hr) and decreased to ca. 58% at 72 hr after treatment. Seed polar extractants averaged ca. 10% of total ¹⁴C recovered for the first 48 hr after treatment and then increased to 30% of total ¹⁴C recovered. Thus, [¹⁴C]vernolate per se concentration decreased to <1% of applied material within 72 hr through volatilization and degradation of nonpolar extractants to polar products. Polar metabolites showed two major patterns of vernolate detoxification. One detoxification system produced ¹⁴C-metabolites whose R_f's were equivalent to that reported in corn (Zea mays L.) [J. P. Hubbell and J. E. Casida, [J. Agric. Food Chem. 25, 404 (1977)] and accounted for <30% of the pod polar extractants. A second detoxification system was most prevalent in soybean pod and seed tissues and resulted in very rapid modification of vernolate with an unidentified product that was 85% of the extracted ¹⁴C within 4 hr after treatment and which decreased in concentration with time. Therefore, unexplained vernolate detoxification system(s) exist in soybean pod and seed.     

Balance of conversion of [14C]lindane in lettuce in hydroponic culture

After application of [¹⁴C]lindane to the nutrient medium (1.45 ppm), 14.1% of the radioactivity was taken up by 12 lettuce plants during 4 weeks; in the nutrient medium, 7.8% was recovered after the same time interval. The radioactivity in the nutrient extract comprised: unchanged lindane (about 82%); free 2,3,4,6-tetrachlorophenol, free pentachlorophenol, conjugates of pentachlorophenol, and an unidentified polar compound (a total of 15%); 1,2,3-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, 2,3,4,5,6-pentachlorocyclohex-1-ene, and probably 1,2,3,4,5,6-hexachlorocyclohexene (a total of 3%). The radioactivity extracted from plants consisted of unchanged lindane (about 77%); free 2,3,4,6-tetrachlorophenol, conjugates of a tetrachlorophenol and pentachlorophenol, and a strongly hydrophilic compound that was not identified (a total of 20%); 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, pentachlorobenzene, 2,3,4,5,6-pentachlorocyclohex-1-ene, and probably 1,2,3,4,5,6-hexachlorocyclohexene (a total of 3%). Identification was carried out by means of comparisons of chromatographic properties and of the mass spectra with those of authentic reference compounds. The significance of hexachlorobenzene as a metabolite of lindane is discussed.     

Conversion of [14C]buturon in soil and leaching water under outdoor conditions

[¹⁴C]Buturon, a urea herbicide, was sprayed on soil and winter wheat as an aqueous formulation (2.98 kg/ha) under outdoor conditions. Three months after application, a total of 49.2% of the applied radiocarbon was recovered: 46.9% in the soil, 0.3% in the leaching water (depth > 50 cm), and 2.0% in the plants. Radioactive residues in the soil were distributed to a depth of 50 cm and decreased with increasing depth of the soil. An average of 47% of the radioactivity present in the soil could be extracted with cold chloroform; by this extraction method, the formation of artefacts was avoided. Between one and two thirds of the extracted radioactivity was unchanged buturon. In the soil extracts, the following eight conversion products were isolated and identified by combined gas chromatography/mass spectrometry: N-(p-chlorophenyl)-N-methyl-O-methyl carbamate; N-(p-chlorophenyl)-O-methyl carbamate; N-(p-chlorophenyl)-N′-methyl-N′-isobutenyl-urea; N-(p-chlorophenyl)-N′-methyl-urea, N-(p-chlorophenyl)-N′-methyl-N′-isobutenylol-urea; p-chloroaniline in “biologically bound” form; N-(p-chlorophenyl)-N′-methyl-N′-methoxyisobutenyl-urea; and N-(p-chlorophenyl)-N′-methyl-N′-ethoxyisobutenyl-urea. In the leaching water, which contained only 0.005–0.006 mg/liter of radioactive substances, the following three conversion products were isolated and identified by gas chromatography/mass spectrometry: p-chloroformanilide; N-(p-chlorophenyl)-N-methyl-O-methyl carbamate; and an N-hydroxyphenyl-N′-methyl-N′-isobutinyl-urea. The results are discussed in relation to the factors responsible for the formation of these products.     

Behavior of 14C oryzalin in soil and plants

Radiochemical studies of field soil treated with ¹⁴C oryzalin (3,5-dinitro-N⁴,N⁴-dipropylsulfanilamide) indicated that the compound was readily degradable. One year after soil treatment with oryzalin, 45% of the original radioactivity had dissipated, 25% was extractable, and 30% was “soil bound”. The extractable fraction contained oryzalin and several degradation products, some of which were isolated and identified. No single degradation product accounted for more than 3% of the applied oryzalin. The “soil-bound” radioactivity was extractable with hot alkali. No significant radioactive residues were detectable in either seed or forage of soybean and wheat plants. No specific metabolites of oryzalin were identified in soybean plants. Trace amounts of radioactivity found in plant tissue appeared to be associated with the various plant constituents.     

Effects of herbicides and herbicide analogs on [14C]leucine incorporation by suspension-cultured Solanum nigrum cells

Assays of [¹⁴C]leucine incorporation were used to measure effects of herbicides on suspensioncultured heterotrophic Solanum nigrum cells. Most herbicidal vs. nonherbicidal chemicals in a set of 47 compounds could be distinguished from each other based on their extent of inhibition of leucine incorporation by S. nigrum cells. Herbicides which failed to inhibit leucine incorporation were photosynthetic inhibitors. Both phytotoxic and nonphytotoxic thiocarbamate analogs (as determined by whole-plant studies) tended to inhibit leucine incorporation. It was concluded that the leucine incorporation screen could detect a majority of compounds tested which are herbicidal, and that it may also be useful to detect compounds which have cellular toxicity which is not observed in the whole plant.     

Penetration of triolein and methyl oleate through isolated plant cuticles and their effect on penetration of [14C]quizalofop-ethyl and [14C]fenoxaprop-ethyl

The penetration of two model seed oil compounds, [¹⁴C]triolein (TRI) and [¹⁴C]methyl oleate (MEO) through plant cuticles and their effects on the penetration of [¹⁴C]quizalofop-ethyl and [¹⁴C]fenoxaprop-ethyl were investigated. Experiments were carried out using isolated cuticles from rubber plant (Ficus elastica Roxb.) leaves and from tomato (Lycopersicon esculentum Mill,) and pepper (Capsicum annuum L.) fruits. Chemicals were deposited in droplets on to cuticle discs maintained on agar blocks under controlled conditions. TRI and MEO were used at 1% (V/V). The transfer of radiolabel through cuticles was negligible for TRI and varied from 6 to 13% after 72 h, according to species, for MEO, The penetration results obtained for quizalofop-ethyl (0.084 mg mL^-1) and fenoxaprop-ethyl (0.189 mg mL^-1) were very similar and varied according to species. The greatest diffusion intoagar was observed for pepper (12.8% and 10.7% after 72 h, for quizalofop-ethyl and fenoxaprop-ethyl respectively), the lowest for rubber plant cuticles (1.4 and 1.3% respectively). Addition of MEO produced significant increases in the penetration of quizalofop-ethyl and fenoxaprop-ethyl through rubber plant and tomato cuticles. TRI had an enhancing effect on the two herbicides only with rubber plant cuticles. Results are discussed with particular consideration of the variations between plant species and the possible mode of action of seed oil adjuvants.     

The in vitro degradation of [14C]malathion by enzymatic extracts from resistant and susceptible strains of Drosophila melanogaster

Enzyme preparations from Drosophila melanogaster flies degraded [¹⁴C]malathion to α- and β-malathion monoacids and, hence, were considered to contain malathion carboxylesterase (ME) activity. Although ME- activity was stable during preincubation in the absence of malathion, it decreased dramatically during the course of the reaction, and could not be completely recovered by Sephadex G-25 chromatography. Furthermore, the protein fraction after chromatography still contained ¹⁴C, suggesting that the enzyme had become inhibited by a bound, ¹⁴C-labeled derivative. Extracts from a resistant (malathion-selected), an intermediate control, and the susceptible Canton S strains of D. melanogaster differed in the lability of ME activity during the reaction. This difference was partly attributed to the production of small amounts of malaoxon (2–8%) by the extracts from the more resistant strains. No consistent strain differences were found when the rate of malathion degradation was measured during the first minute of reaction, either with or without a microsomal oxidase inhibitor (metyrapone) present. These results, together with the cross-resistance of the malathion-selected strain to other insecticides and the lack of a synergistic effect of two carboxylesterase inhibitors (triphenyl phosphate and S,S,S-tributylphosphorotrithioate) suggested that malathion carboxylesterase does not contribute significantly to the observed differences in malathion resistance between strains.     

Disposition and metabolism of [14C]chlorpyrifos in the black imported fire ant, Solenopsis richteri Forel

The short-term disposition and metabolism of topically administered [¹⁴C]chlorpyrifos was assessed in the black imported fire ant (Solenopsis richteri Forel) in the presence and absence of the mixed-function oxidase inhibitor piperonyl butoxide. Chlorpyrifos is readily absorbed into an internal organosoluble fraction which was quickly converted into a water-soluble fraction. The radioactivity was slowly excreted over a 24-hr period. Piperonyl butoxide slowed the conversion of the internal organosoluble radioactivity to the water-soluble fraction. Thin-layer chromatography indicated that piperonyl butoxide slowed the conversion of chlorpyrifos to material remaining at the origin, presumably water-soluble metabolites. The results of acid hydrolysis studies indicated that the water-soluble radioactivity was comprised mainly of conjugates. Although very little chlorpyrifos oxon was recovered in the metabolism experiments, in vitro studies on fire and head homogenates showed the compound to be an extremely potent anticholinesterase, with an I₅₀ of 4.6 × 10^?10M, while a major metabolite, 3,5,6-trichloropyridinol, was an ineffective acetylcholinesterase inhibitor.     

Metabolism and balance studies of [14C]monolinuron after use in spinach followed by cress and potato cultures

[¹⁴C]Monolinuron was added to soil which was then successively cropped with spinach, cress, and potatoes. Incubation was carried out in a closed system which allowed recoveries even of volatile degradation products and gave an overall recovery of 96% of the applied radioactivity at the end of the experiment. The spinach was found to contain 4.1% of the applied activity; the cress, 5.6%; old potatoes + leaves, 9.5%; new tubers, 1%; and the soil, 68.6%. The total amount of [¹⁴C]carbon dioxide liberated was 5.3%. The quantitative separation and characterization of the extractable radioactivity in spinach yielded 10.6% as unaltered monolinuron, 12% as 4-chlorophenylurea plus 4-chlorophenyl-hydroxymethylurea, 3.7% as 4-chlorophenylmethylurea, 1.4% as 4-chlorophenyl-hydroxymethyl-methoxyurea, 1.1% as 4-chlorophenyl-methoxyurea, and 71.2% as polar metabolites. Of these polar metabolites, 67.1% were cleaved with β-glucosidase, resulting in 2.9% unknown aglucone, 48.1% 4-chlorophenyl-hydroxymethyl-methoxyurea, and 16.1% 4-chlorophenyl-hydroxymethylurea. Similar results have been obtained in cress and potatoes. The soil contained 58% of monolinuron residues and 4.7?6.5% of the same types of metabolites as were found in plants. Twenty-one percent were found as polar metabolites.     

逐级温度热解法在黄土古土壤样品~(14)C测年中的应用

利用已知可靠年代的黄土古土壤样品,采用逐级热解的方法,获取不同温度下的热解组分,运用加速器14C测年技术,测试各个组分的14C年龄,探讨获得可靠测年组分所需的逐步解热的实验条件。研究表明,逐级热解过程中,100℃～600℃温度段的热解挥发组分为年轻碳,而600℃～800℃温度段热解残余物(Py-R)则为老碳,600℃～800℃热解挥发组分(Py-V)是黄土-古土壤14C测年的可靠组分。     

Biotransformation of [ring-U-14C]atrazine to dealkylated and hydroxylated metabolites in cell-suspension cultures

The biconversion of [¹⁴C]atrazine to deaikyt-ated and hydroxylated products was studied in heteroirophic cell-suspension cultures of carrot ( Daucus caroia L.), Agrostemma githago L. (corn cockle). Digitalis purpurea L. (purple foxglove), soyabean ( Giycine max L. Merr; four different cultivars). Datura stramonium L. (thorn-apple) and wheat ( Tritician aestivum L.). During 48 h of incubation, the herbicide was biotransformed by all species; turnovers yields differed considerably and were between 10.1% and 88.0% of applied ¹⁴C. Differences were also observed among the soyabean cultivars (10.1-73.5%). Hydroxy-atrazine, de-ethyl-, deisopropyl- and de-ethyt-deisopropylatrazine formed in the cultures were identified by thin-layer chromatography (tlc) (co-chromatography with reference compounds); deaikyiated metabolites were also proved by gas chromatography–mass spectrometry (gc–ms). In addition, highly polar transformation products emerged that were not identified. Portions of non-extractable residues were below 5% (one soyabean cultivar: 8.9%). Atrazine was metabolized by the cells, mainly to its dealkylated derivatives and hydroxyatrazine (totals of 9.4-54, 5%), whereas portions of highly polar products were lower (0.1-26.1%). Exceptions were A. githago (26.0 and 33.6%, respectively) and D, purpurea (4.5 and 25.2% respectively). Thus, plants generally contribute to the environmental degradation of atrazine.     

Determination of extractable and non-extractable radioactivity from prairie soils treated with carboxyl- and ring-labelled [14C]2,4-D

Ring- and carboxyl-labelled [¹⁴C]2,4-D were incubated under laboratory conditions, at the 2 g/g level, in a heavy clay, sandy loam, and clay loam at 85% of field capacity and 20 1C. The soils were extracted at regular intervals for 35 days with aqaeous acidic acetonitrile, and analysed for [¹⁴C]2,4-D and possible radioactive degradation products. Following solvent extraction, a portion of the soil residues were combusted in oxygen to determine unextracted radioactivity as [¹⁴C]carbon dioxide. The remaining soil residues were then treated with aqueous sodium hydroxide, and the radioactivity associated with the fulvic and humic soil components determined. In all soils there was a rapid decrease in the amounts of extractable radioacitivity, with only 5% of that applied being recoverable after 35 days. All recoverable radioactivity was attributable to [¹⁴C]2,4-D, and no [¹⁴C]-containing degradation products were observed. This loss of extractable radioactivity was accompanied by an increase in non-extractable radioactivity. Approximately 15% of the applied radioactivity, derived from carboxyl-labelled [¹⁴C]2,4-D, and 30% from the ring-labelled [¹⁴C]2,4-D was associated with the soil in a non-extractable form, after 35 days of incubation. After 35 days, less than 5% of the radioactivity from the carboxyl-labelled herbicide, and less than 10% of the ringlabelled material, was associated with the fulvic components derived from the three soils. Less than 5% of the applied radioactivities were identifiable with any of the humic acid components. It was considered that during the incubation [¹⁴C]2,4-D did not become bound or conjugated to soil components, and that non-extractable radioactivity associated with the three soil types resulted from incorporation of radioactive degradation products, such as [¹⁴C]carbon dioxide, into soil organic matter.     

Soil persistence studies with [14C]MCPA in combination with other herbicides and pesticides

The persistence of [¹⁴C]MCPA at a rate equivalent to 1 kg ha^?1 was studied under laboratory conditions in a clay loam, heavy clay and sandy loam at 85% of field capacity moisture and 20±1°C both alone and in the presence of tri-allate, trifluralin, tri-allate and trifluralin, malathion, Vitaflow DB, malathion and Vitaflow DB, bromoxynil, bromoxynil and asulam, bromoxynil and difenzoquat, dicamba, dicamba and mecoprop, linuron, MCPB, metribuzin, propanil, TCA, benzoylprop-ethyl, diclofop-methyl, and flamprop-methyl. Except in the soils treated with asulam, the half-lives of [¹⁴C]MCPA in all three soil types were similar, being approximately 13±1 days, thus indicating that none of the other chemicals studied adversely affected the soil degradation of MCPA. In the asulam treated soils, the half-lives of the MCPA were about 3 days longer than in non-asulam treated soils; the effect was most marked in the clay loam.     

Soil persistence studies with bromoxynil, propanil and [14C]dicamba in herbicidal mixtures

The persistence of bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), [¹⁴C]dicamba (3,6-dichloro-2-methoxybenzoic-7-¹⁴C acid) and propanil [N-(3,4-dichlorophenyl)propionamide] at rates equivalent to 1 kg ha^?1, were studied under laboratory conditions in a clay loam, a heavy clay and a sandy loam at 85% of field capacity and at 20±1°C, both singly and in the presence of herbicides normally applied with these chemicals as tank-mix or split-mix components. The degradation of bromoxynil was rapid with over 90% breakdown occurring within a week in the heavy clay and sandy-loam soils, while in the clay-loam approximately 80% of the bromoxynil had broken down after 7 days. In all three soils degradation was unaffected by the presence of asulam, diclofop-methyl, flamprop-methyl, MCPA, metribuzin or propanil. Propanil underwent rapid degradation in all soil treatments, with over 95% of the applied propanil being dissipated within 7 days. There were no noticeable effects on propanil degradation resulting from applications of asulam, barban, bromoxynil, dicamba, MCPA, MCPB, metribuzin or 2,4-D. The breakdown of [¹⁴C]dicamba in a particular soil was unaffected by being applied alone or in the presence of diclofop-methyl, flampropmethyl, MCPA, metribuzin, propanil or 2,4-D. The times for 50% of the applied dicamba to be degraded were approximately 16 days in both the clay loam and sandy loam, and about 50 days in the heavy clay.     

Persistence studies with [14C] 2,4-D in soils previously treated with herbicides and pesticides

The persistence of [¹⁴C] 2,4-D at a rate equivalent to 1 kg/ha was compared under laboratory conditions in samples of heavy clay, sandy loam, and clay loam at 85% of field capacity moisture and 20 ± 1°C which had either received no pre-treatment, or had been pre-treated for 7 days at the 2 μg/g level with the herbicides benzoylprop-ethyl, diclofop-methyl, dinitramine, flamprop-methyl, nitrofen, picloram, tri-allate, trifluralin, and a combination of tri-allate and trifluralin. The breakdown of [¹⁴C] 2,4-D was also studied in the same soils that had similarly received pre-treatments of 2 μg/g of the cereal seed dressing Vitaflo-DB, the insecticide, malathion, and a combination of Vitaflo-DB and malathion. In each soil type, the half-life of the 2,4-D was similar regardless of whether the soil had, or had not, received any pre-treatment, indicating that none of the chemicals investigated adversely affected the soil degradation of 2,4-D.     

The fate of [3-14C]metamitron in sugar beets after preemergence application in a lysimeter study

In a lysimeter experiment, [3-¹⁴C]metamitron was sprayed in a preemergence treatment of sugar beets, corresponding to approx 4.9 kg metamitron (7 kg Goltix)/ha. After 6 months, the beets contained metamitron equivalents amounting to 0.1 mg/kg fresh wt, calculated on the basis of the specific radioactivity of the [3-¹⁴C]metamitron employed. Radioactivity was also detected in the pure sugar isolates. The ¹⁴C activity represented approx 0.2 mg metamitron equivalent/kg pure sugar. Since the specific radioactivities of the sugar fractions were too low to employ physicochemical methods, a microbial degradation was used to investigate whether the radiocarbon was incorporated in the sucrose molecule. Microorganisms (Proteus vulgaris) degraded [U-¹⁴C] sucrose and the sugar isolates at the same ¹⁴CO₂ release rates under strictly controlled experimental conditions. This result indicates that about one fourth of the carbon from the C-3 position of the triazine ring of the metamitron, found in the sugar beets at harvest time, is partly being used as a substrate in the production of sucrose possibly via assimilation of mineralized ¹⁴CO₂.