• Korean Journal of Environmental Agriculture
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• v.10 no.2
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• pp.149-157
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• 1991

In order to elucidate the possible change in the non-extractable bound residue of TCAB(3,3' 4,4' - tetrachloroazobenzene) in soil as a function of aging period, uniformly ring-labelled $^{14}C-TCAB$ was treated to soil(organic matter : 1.8%), and aged for 3, 6, 9, 12 and 15 months at $21{\pm}1^{\circ}C$, respectively. $^{14}CO_2$ evolution and volatilization loss during the aging were negligible. The amounts of non-extractable bound residue of TCAB increased gradually from 7.55% in 3-month aging to 19.32% in 15-month aging. Partition data suggested no formation of polar groups in the chemical structure of TCAB. Most of $^{14}C-radioactivity$ of bound residues was present in humin in the range of 50.52 to 58.93%. The fact that the number of microorganisms in soil decreased relative to the control suggested no chance of their involvement in the formation of non-extractable bound residues. Accordingly, the increase in the non-extractable bound residue of TCAB in soil with aging period is believed to be due to the transformation of the trans isomer to the cis one which is more polar and more adsorptive than the former.

• The Korean Journal of Pesticide Science
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• v.3 no.2
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• pp.29-36
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• 1999

The leaching behaviour of $^{14}C$-paraquat in soil was investigated using soil columns (5 cm I.D. ${\times}$ 30 cm H.) parked with two soils of different physicochemical properties. $^{14}C$-Activities leached from the soil A (loam) columns with and without rice plants for 117 days were 0.42 and 0.54% of the originally applied, whereas those from the soil B (sandy loam) were 0.21 and 0.31%, respectively. $^{14}C$-Activities absorbed by rice plants from soil A and B were 3.87 and 2.79%, respectively, most of which remained in the root. Irrespective of soil types, more than 96% of the total $^{14}C$ resided in soil, mostly in the depth of $0{\sim}5$ cm. The water-extractable $^{14}C$ in soil was in the range of $6.10{\sim}9.01%$ of the total $^{14}C$ applied. The rest of $^{14}C$, which corresponds to non-extractable soil residues of [$^{14}C$]paraquat, was distributed in humic substances in the decreasing order of humin>humic acid>fulvic acid. The soil pH of the columns without rice plants increased after the leaching experiment due to the flooded anaerobic condition resulting in the reduction of the $H^{+}$ concentration, whereas that of the columns with rice plants did not increase by the offsetting effect of the acidic exudates from the roots. Low mobility of paraquat in soil strongly indicates that no contamination of ground water would be caused by paraquat residues in paddy soils under normal precipitation.

• Korean Journal of Environmental Agriculture
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• v.19 no.4
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• pp.300-308
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• 2000

The degradation of herbicide $^{14}C-bifenox$ was studied in soils under anaerobic conditions. $^{14}C-bifenox$ was treated in silty loam and sandy loam soils, respectively at a rate of 2.1 mg/kg, and the soil was incubated under anaerobic conditions at $25^{\circ}C$ for 180 days. The mineralization, solvent extractable and non-extractable residues, degradation products of bifenox were investigated during the experiments. The relative amounts of $^{14}CO_2$ were 1.97 and 0.9% of applied $^{14}C$ in silty loam and sandy loam soils, respectively. The non-extractable residues of sandy loam soil increased dramatically up to 79.12% of applied $^{14}C$, and were higher than those of silt loam soil, suggesting physico-chemical properties and especially organic matter contributed to the difference of $^{14}C$ between two soils. The non-extractable residues were formed mainly humin fraction and increased with time. The major metabolites were nitrofen, 5-(2,4-dichlorophenoxy)-2-Nitrobenzoate, 2,4-dichlorophenoxy aniline and methyl 5-(2,4-dichlorophenoxy) anthranilate by GC/MS analysis. From the results of volatilization, mineralization and degradation of bifenox, bifenox was stable chemically and biologically in soil.

• The Korean Journal of Pesticide Science
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• v.3 no.2
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• pp.8-18
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• 1999

The degradation of a fungicide, $^{14}C$-propiconazole, in sterile and nonsterile soil from different depths was investigated. $^{14}C$-propiconazole plus propiconazole standard was treated on the soil at the rate of 7.55 mg/kg and the soil was incubated at $25^{\circ}C$ for 20 weeks. The amounts of $^{14}CO_{2}$ solvent extractable and non-extractable $^{14}C$, and degradation products of $^{14}C$-propiconazole were investigated during incubation time. The relative amounts of $^{14}CO_{2}$ released in the sterile and nonsterile soils were ranging from 0.7 to 1.3% and from 4.8 to 7.6% of applied $^{14}C$, repectively. The amounts of solvent non-extractable residues in the sterile and nonsterile soils were ranging from 11.2 to 22.1% and from 22.2 to 41.9% of of applied $^{14}C$, repectively. The amounts of solvent non-extractable residues were increased with incubation time and most of $^{14}C$ were detected in the humin fraction. The hydroxylated and ketone compound were confirmed as a degradation products of propiconazole by GC/MS analysis, whereas parent compound was detected in sterile soil, which suggested that propiconazole was not degraded biologically under the sterile soil. From the results of volatilization, mineralization and degradation of propiconazole, propiconazole was stable chemically and bilogically in soil.

• The Korean Journal of Pesticide Science
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• v.3 no.1
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• pp.66-77
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• 1999

In order to elucidate the fate of the residues of the bipyridylium herbicide paraquat in soil, maize plants were grown for 4 weeks on the specially-made pots filled with two different types of soils containing fresh and 6-week-aged residues of [$^{14}C$]paraquat, respectively. The mineralization of [$^{14}C$]paraquat to $^{14}CO_{2}$ during the aging period and the cultivation period of maize plants amounted to $0.13{\sim}0.18%$ and $0.02{\sim}0.17%$, respectively, of the original $^{14}C$ activities. At harvest the roots and shoots contained less than 0.1% and 0.01% of the originally applied $^{14}C$ activities, respectively, whereas the $^{14}C$ activities remaining in soil were more than 97% in both soils. The water extractability of the soil where maize plants were grown for 4 weeks was less than 1.2% of the original $^{14}C$ activities. Most of the non-extractable soil-bound residues of [$^{14}C$]paraquat were incorporated into the humin fraction. Soil pHs during the aging of soil B and after cultivation in all treatments increased. The distribution of the $^{14}C$ activities in subcellular particles of the maize plant roots was the highest in the residue fraction(incompletely homogenized tissue). Dehydrogenase activities increased after vegetation, regardless of soil aging.

• The Korean Journal of Pesticide Science
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• v.2 no.3
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• pp.96-106
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• 1998

Rice plants were grown for 42 days in the specially made micro-ecosystem(pot) containing two different soils treated with fresh and 60-day-aged residues of [$^{14}C$]quinclorac, respectively, to elucidate the behaviour of the herbicide quinclorac residues in the soils. Amounts of $^{14}CO_{2}$ evolved from two soils treated with different residues with and without vegetation were all less than 2.2% of the total $^{14}C$, indicating that there was little microbial degradation of quinclorac in soil. $^{14}C$-Radioactivity absorbed and translocated into rice plants from soil A and B containing fresh quinclorac residues was 8.4 and 24.2%, respectively, of the originally applied $^{14}C$, while 5.5 and 17.7%, in aged residue soils. These results indicate that larger amounts of $^{14}C$ were absorbed by rice plants from soil B with less organic matter and clay than soil A, and the uptake of [$^{14}C$]quinclorac and its degradation products decreased with aging in soil. After 42 days of rice growing, 84.5 and 61.8% of the $^{14}C$ applied freshly to soil A and B, respectively, remained in soil, whereas, in the case of aged soils, 86.3 and 67.7% of the $^{14}C$ applied did. Meanwhile, without vegetation, more than 98.3% of the $^{14}C$ applied, in both fresh and aged residues, remained in soil, suggesting that quinclorac was relatively persistent chemically and microbiologically. Most of the non-extractable soil-bound residues of [$^{14}C$]quinclorac were incorporated into the organic matter and largely distributed in the fulvic acid portion.

• The Korean Journal of Pesticide Science
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• v.8 no.3
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• pp.198-209
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• 2004

In order to elucidate the behavior of the fungicide hexaconazole in soil and rice plants, rice plants were grown for 42 days in a microecosystem (pot) containing fresh and 28 day-aged soil residues of $[^{14}C]$hexaconazole. The amount of $^{14}CO_2$ evolved during 28 days of aging was 0.11 % of total $^{14}C$-radioactivity treated and the averaged weekly degradation rate was 0.03%. Mineralization rates for 42 days of rice cultivation on fresh and aged paddy soils were 0.67% of the total $^{14}C$ in case of non-rice planting on aged soil and 1.17% in case of rice planting on aged soil, whereas 1.25% in non-rice planting on fresh soil and 1.72% in case of rice planting on fresh soil, suggesting that the amounts of $^{14}CO_2$ were evolved higher from fresh soils than aged ones and from rice-planting soils than non-planting ones. The amounts of volatiles collected were very low as background levels. Most of $^{14}C$-Radioactivity was remained in soil after 42 days of rice cultivation and $^{14}C$ absorbed through rice roots was distributed more in shoots than roots and translocated into the edge of shoots of rice plants. Amounts of non-extractable $^{14}C$ in soils were higher in rice planted soil than in non-planting soil. The distribution of non-extractable $^{14}C$ was increased in the order of humin>fulvic acid>humic acid. The amounts of $^{14}C$ translocated into rotational crop Chinese cabbage were 2.36 and 3.69% of the total $^{14}C$ in case of rice planted soil containing fresh and aged residues, respectively, suggesting that small amounts of $[^{14}C]$hexaconazole and its metabolite(s) were absorbed and their bound residues were more available than their fresh ones to Chinese cabbage.

• Korean Journal of Environmental Agriculture
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• v.14 no.2
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• pp.202-212
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• 1995

In order to elucidate the degrading characteristics of the pyrethroid acaricide-insecticide, acrinathrin in two different types of soils, Soil A(pH, 5.8; organic matter, 3.4%; C.E.C., 115 mmol(+)/kg soil; texture, sandy loam) and Soil B(pH, 5.7; organic matter, 2.0%; C.E.C., 71 mmol(+)/kg soil; texture, sandy loam), residualities of the non-labeled compound under the field and laboratory conditions, extractability with organic solvents and formation of non-extractable bound residues, and degradabilities of [$^{14}C$]acrinathrin as a function of aging temperature and aging period were investigated. The half lives of acrinathrin in Soil A treated once and twice were about 18 and 22 days and in Soil B about 13 and 15 days, respectively, in the field, whereas, in the laboratory, those in Soil A and B were about 36 and 18 days, respectively, suggesting that the compound would be non-persistent in the environment. The amounts of $^{14}CO_2$ evolved from [$^{14}C$]acrinathrin in Soil A and B during the aging period of 24 weeks were 81 and 62%, respectively, of the originally applied $^{14}C$ activity, and those of the non-extractable soil-bound residues of [$^{14}C$]acrinathrin were about 70% of the total $^{14}C$ activity remaining in both soils, increasing gradually with the aging period. Degradation of [$^{14}C$]acrinathrin in both soils increased with the aging temperature. Three degradation products of m/z 198(3-phenoxy benzaldehyde), m/z 214(3-phenoxybenzoic acid), and m/z 228(methyl 3-phenoxybenzoate) as well as an unknown were detected by autoradiography of acetone extracts of both soils treated with [$^{14}C$]acrinathrin and aged for 15, 30, 60, 90, 120, and 150 days, respectively, and the degradation pattern of acrinathrin was identical in both soils. Acrinathrin in soil turned out to be degraded to 3-phenoxybenzaldehyde cyanohydrin by hydrolytic cleavage of the ester linkage adjacent to the $^{14}C$ with a cyano group, the removal of hydrogen cyanide therefrom led to the formation of 3-phenoxybenzaldehyde as one of the major products, and the subsequent oxidation of the aldehyde to 3-phenoxybenzoic acid, followed by decarboxylation would lead to the evolution of $^{14}CO_2$.

• Korean Journal of Environmental Agriculture
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• v.7 no.1
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• pp.1-7
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• 1988

In order to clarify how much of the residues of Bentazon could be taken up by crops, soybean and radish were grown for 28 days in soils containing freshly treated $^{14}C-Bentazon$ and non-extractable soil-hound residues of $^{14}C-Bentazon.$ The results obtained are summarized as follows. 1. $^{14}CO_2$ evolution from $^{14}C$-Bentazon during the 6-month pre-incubation in soil was 14.79% relative to the applied radioactivity. 2. Mineralization of ^$^{14}C$-Bentazon in soil to $^{14}CO_2$ during 28 days of crop growing was much higher in the freshly treated soil than in the bound soil, and much higher in radish than in soybean. 3. The amounts of $^{14}C-Bentazon$ and its metabolites absorbed by soybean and radish were 45.41 and 21.48%, respectively, in freshly treated soil, whereas those were 3.92 and 1.23% in bound soil, respectively. The translocation ratios of radioactivity .from the root to the shoot were much higher in radish than in soybean, remarkably. 4. The uptake ratios of the freshly treated $^{14}C-Bentazon$ to the bound $^{14}C-Bentazon$ by soybean and radish were 12 : 1 and 17 : 1, respectively. 5. It was well verified that the presence of crops enhanced the mineralization to $^{14}CO_2$ and the transformation to polar metabolites of Bentazon.

• Applied Biological Chemistry
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• v.32 no.4
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• pp.393-400
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• 1989

The amounts of $^{14}CO_2$ evolved during the $^{14}C-bentazon$ aging in soil for 3 and 6 months were 6.1 and 14.8% of the original radioactivity, respectively. The presence of earthworms in soil tended to increase the uptake of $^{14}C-bentazon$ by the roots of rice plants, even if it was not statistically significant. The evolution of $^{14}CO_2$ from $^{14}C-bentazon$ in soil increased in the presence of rice plants and earthworms compared with in the absence of them. The uptake of $^{14}C-bentazon$ residues by rice plants decreased remarkably with increasing the aging period within the limit of 3 months both in the absence and presence of earthworms, but there is not much difference between 3-month-aging and 6-month-aging. Much larger amounts of $^{14}C-labelled$ compounds were translocated to the shoots, compared with the data from a previous investigation using maize plants. The amount of non-extractable bound residue increased remarkably with the aging period up to 3 months. The polarity of the compounds extracted from soil increased with the aging and the growing of rice plants, indicating the formation of some polar metabolites.