摘要:

Dissipation and degradation of14C‐p,p'‐DDT (Faisalabad and Peshawar locations) and14C‐p,p'‐DDE (Faisalabad location) were studied for one year in soils under field conditions. Both DDT and DDE dissipated more rapidly under the Pakistani subtropical climate than reported for temperate regions. More binding to soil of14C‐DDT was observed at Peshawar than that at Faisalabad. Overall halflives were 144 and 313 days in Faisalabad and Peshawar respectively. The main degradation products of p,p'‐DDT extracted from soils at the two locations were p,p'‐DDE and p,p'‐DDD.14C‐DDE showed an overall halflife of 191 days under Faisalabad field conditions. Since the degradation of both DDT and DDE was not substantial, it is maintained that dissipation of both chemicals was largely due to volatilization/codistillation.

ISSN:0360-1234    

DOI:10.1080/03601239409372853

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Dissipation, binding, and degradation of14C‐p, p'‐DDT in Indonesian soils were studied under field conditions in Pasar Jumat (lowland) and Cipanas (highland). A study on14C‐p, p'‐DDE was also conducted at Pasar Jumat. The observed time for 50% loss of radiocarbon was 25, 9 and 12 weeks for DDT lowland, DDT highland and DDE respectively. The corresponding overall half‐lives of dissipation were 236, 159 and 228 days respectively. Bound residue formation progressed slowly to 7% in lowland. After one year, total14C residues from DDT remaining in lowland and highland soils were 34.3% and 20.4% respectively. Degradation of p,p'‐DDT in lowland was faster than in highland and the major degradation product was p,p'‐DDE. In the DDE experiment no metabolite was found. It is concluded that both DDT and DDE dissipate from tropical Indonesian soils at much faster rates than those reported for temperate zones.

ISSN:0360-1234    

DOI:10.1080/03601239409372854

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Dissipation and degradation of14C‐p,p'‐DDT in soil was studied under field conditions in the Philippines for two consecutive years. Extractable radioactivity decreased with time while there was a gradual increase of bound activity. Half‐life of dissipation of total14C was 261 days and 210 for the two field trials while the half‐life of extractable radioactivity was 173 and 134 days. p,p'‐DDE was the major metabolite in the extracts and the half‐life of extracted DDT was 105 days. In the laboratory, the soil mineralized 70% of14C‐DDT at 35°C in six weeks, while organic volatiles contributed < 1%. Almost 80% of soil‐bound14C was released by addition of fresh soil; presumably through the action of microflora.

ISSN:0360-1234    

DOI:10.1080/03601239409372855

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The behaviour of14C‐p,p'‐DDT was studied in upland and paddy soils. Under field conditions in subtropical Hangzhou the initial amount declined to 67% after 43 weeks. In tropical upland soil at Guangzhou the original amount was reduced to 46% after 34 weeks indicating faster dissipation rates. Bound residues formed slowly and accounted for approximately 10% of the initial14C after 43 and 34 weeks in Hangzhou and Guangzhou respectively. Overall dissipation half‐lives were 75 and 31 weeks for Hangzou and Guangzhou respectively. The extractable residues contained predominantly DDT and smaller amounts of DDE, DDD and DDA. In paddy flooded soil, 50% of the radioactivity dissipated after approximately six weeks. Extractable residues declined gradually while bound residues slowly increased to represent >50% of the terminal residue after 25 weeks. The dominant product in the extracts after 25 weeks was DDD. It may be concluded that tropical climatic and soil conditions at Guangzhou resulted in a relatively rapid dissipation of DDT, while flooded conditions were highly effective in removing the insecticide. Up to one third of bound14C‐residues formed in paddy flooded soil could be released by incubation with a fresh soil inoculum (1:1) for four months. DDD was a major component in the released products.

ISSN:0360-1234    

DOI:10.1080/03601239409372856

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The dissipation and degradation of14C‐DDT and14C‐DDE in Egyptian soil were studied under field conditions. Both chemicals dissipated readily from soil; DDE, at a slightly higher rate. The time required for 50% initial dissipation of radiocarbon was estimated to be 55 and 50 days for DDT and DDE respectively. After 9 months, the organic extracts of a 14 cm soil column showed the absence of DDT from14C‐DDT treated soils. In14C‐DDE treated soils, extractable residues showed the presence of unchanged DDE as the main component. Throughout the experiment, binding from both chemicals was low (about 2%).

ISSN:0360-1234    

DOI:10.1080/03601239409372857

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The dissipation and degradation of14C‐p,p'‐DDT in tropical soils of Nairobi were studied under field and laboratory conditions for a period of six months. DDT was found to dissipate much more rapidly from the soil under field conditions than reported for temperate regions. The dissipation curve was found to be biphasic; a rapid phase from 0–37 days after application and a slower phase from 51–172 days. Based on first order kinetics an overall half‐life of 65 days was calculated. The bound residues initially constituted a very small percentage (1.3%) of the applied pesticide and gradually increased to 5.9% after 64 days. The main degradation products extracted from the soil were p,p'‐DDE and a small percentage of p,p'‐DDD. While the amount of p,p'‐DDT decreased with time, there was a slow increase in the amount of p,p'‐DDE extracted from the soil.

ISSN:0360-1234    

DOI:10.1080/03601239409372858

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

14C‐labelled p,p'‐DDT and p,p'‐DDE were used to study the dissipation and degradation rates in soil under tropical field conditions in two locations. Dissipation of DDT was more rapid at Magugu (with hot and wet climate) than at Arusha (with cool and wet climate). After 350 days the methanol‐extractable residues declined to 14.44% and 33.76% for Magugu and Arusha respectively; while the bound residues gradually increased to a maximum of 10.03% after 106 days in Magugu and 11.99% after 286 days in Arusha. The overall half‐life for14C‐dissipation was 174 days for Magugu and 335 days for Arusha. DDT degraded mainly to DDE and to a smaller extent to DDD. The dissipation rate of14C‐DDE in Arusha was little higher than DDT under similar field conditions, with an overall half life of 233 days.

ISSN:0360-1234    

DOI:10.1080/03601239409372859

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The persistence, metabolism and binding of14C‐p,p'‐DDT in soil were studied for two years under field sub‐tropical conditions in Delhi, India. Two experiments were conducted at initial concentrations of 3.7 and 12.8 ppm and it was shown that about 80% of the DDT was lost from the soil in two years. The half life of DDT was 319 and 343 days in the two experiments. At zero‐time p,p'‐DDT accounted for 93–95% of the extractable residues. Gradually, the proportion of p,p'‐DDT declined with time to 58–71% of the extractable residues after two years. In addition to DDT, the extractable residues contained DDE and DDD. DDE was the major metabolite of DDT in soil and accounted for about 22% of the extractable residue after 245 days and 37% after 18 months. DDD accounted for only 5% of the extractable residues after 18 months. Initially, the amount of bound residues was very small, but it gradually increased reaching a maximum of about 8% after one year. However, the bound residues declined thereafter to 4.5–5.45% after 1.5 years and to 3.4–4.2% after 2 years. The soil‐bound residues were chemically released by sulfuric acid treatment and were found to consist of DDT, DDE and DDD.

ISSN:0360-1234    

DOI:10.1080/03601239409372860

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Soil was treated with14C‐p,p'‐DDE and left under field conditions for 545 days. The dissipation of the chemical was apparently biphasic; halflife of dissipation 271 days. After one year, 61% of the initially applied radiocarbon was lost from soil. Methanol‐extractable residues declined to about 29% after one year and were shown by TLC and HPLC, to contain mainly p,p’, DDE and a small amount of DDMU. Initially, the proportion of bound (unextractable) residues was very small but increased gradually to 8.7% after one year and declined thereafter to 7% after 1.5 years. These soil‐bound residues, released by treatment with sulfuric acid consisted exclusively of p,p'‐DDE. Volatilization and to a lesser extent mineralization were the main mechanisms for the loss of DDE residues from the soil.

ISSN:0360-1234    

DOI:10.1080/03601239409372861

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Dissipation of14C‐p,p'‐DDT in two Panamanian soils was studied up to two years under field conditions. The highland soil from Cerro Punta had an organic matter content of 7.1% and pH 6.1, while the lowland soil from El Coco had an organic matter content of 1.9% and pH 5.5. The time required for the initial dissipation of 50% of14C was 135 and 365 days for Cerro Punta and El Coco soils respectively. After 2 years, extractable14C was 16% and 28% for Cerro Punto and El Coco soils respectively. As the climatic conditions were the same, these differences in dissipation rates must relate to the soil properties. While the organic content and microbiological complexes may differ, it is also likely that the soil pH can play a role, where the higher acidity may retain the insecticide and its products for longer periods. Binding to soil amounted to approximately 9% after 2 years in both soils. It is concluded that p,p'‐DDT dissipates from Panamanian tropical soils at rates higher than those reported for temperate zones.

ISSN:0360-1234    

DOI:10.1080/03601239409372862

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor