Search

The uptake of 14C-chlorpyrifos by clams (Katalysia opima) was studied to determine the bioaccumulation potential over a period of five days. Chlorpyrifos was applied to a model ecosystem in beakers at the rate of 3 mg l-1 of seawater. Clams showed a maximum uptake of 14C-chlorpyrifos in the first 8 hours of exposure. Subsequently these residues decreased significantly and at the end of 5 days about 1.5% of the applied activity could be recovered from the clam samples. The half-life of chlorpyrifos in this marine water system was about a day. However, after 5 days about 28% of the applied 14C-activity was present in water. This may be significant and could possibly play a role in finding the residue of this insecticide in water bodies. Clams brought about rapid degradation of chlorpyrifos in the first 48 hours. The stabilised residues in water were reflected later in clams. [ABSTRACT FROM AUTHOR]

Metabolism of 14C-naphthalene was studied in aerobic and anaerobic marine sediments from the Mumbai coast, India using a continuous flow-through system for 5 weeks. There was no volatilisation of naphthalene from anaerobic sediment. Naphthalene underwent more extensive mineralization in aerobic sediment (31.6% of the applied activity) than in anaerobic sediment (5% of the applied activity). No metabolite of naphthalene was present in sediments at the end of the incubation period. [ABSTRACT FROM AUTHOR]

Hairy root cultures of Cichorium intybus and Brassica juncea were used for their ability to uptake and degrade DDT (1,1,1-trichloro-2,2-bis-(4'-chlorophenyl)ethane). After 24 h of 14C DDT treatment, only 12-13% of the total applied radioactivity was detected in the culture media, indicating the efficient uptake of DDT by the hairy roots. The majority of the applied radioactivity was associated with the roots. DDT was degraded to various other products such as DDD, DDE and DDMU, along with some unknown compounds by hairy root cultures, which were detected by thin layer chromatography (TLC) and autoradiography. The rate of in situ degradation was found to be higher during the initial stages of culture and the residual 14C DDT in the roots was found to decrease from 77% to 61% over a period of 10-days. There was no spontaneous degradation of 14C DDT in media lacking hairy root cultures or in media with autoclaved hairy roots. This suggests that endogenous root enzymes play a role in the breakdown of 14C DDT. These results suggest the potential applicability and advantage of using these plant species for phytoremediation of persistent xenobiotics such as DDT in an eco-friendly and efficient manner for environmental clean up.

Metabolism of 14C-naphthalene was studied in aerobic and anaerobic marine sediments from the Mumbai coast, India using a continuous flow-through system for 5 weeks. There was no volatilisation of naphthalene from anaerobic sediment. Naphthalene underwent more extensive mineralization in aerobic sediment (31.6% of the applied activity) than in anaerobic sediment (5% of the applied activity). No metabolite of naphthalene was present in sediments at the end of the incubation period.

The uptake of 14C-chlorpyrifos by clams (Katalysia opima) was studied to determine the bioaccumulation potential over a period of five days. Chlorpyrifos was applied to a model ecosystem in beakers at the rate of 3 mg l(-1) of seawater. Clams showed a maximum uptake of 14C-chlorpyrifos in the first 8 hours of exposure. Subsequently these residues decreased significantly and at the end of 5 days about 1.5% of the applied activity could be recovered from the clam samples. The half-life of chlorpyrifos in this marine water system was about a day. However, after 5 days about 28% of the applied 14C-activity was present in water. This may be significant and could possibly play a role in finding the residue of this insecticide in water bodies. Clams brought about rapid degradation of chlorpyrifos in the first 48 hours. The stabilised residues in water were reflected later in clams.

Degradation of 14C-chlorpyrifos was studied in a marine ecosystem for 60 days and in marine sediment under moist and flooded conditions using a continuous flow system allowing a total 14C-mass balance for a period of 40 days. In the marine ecosystem, 14C-chlorpyrifos underwent rapid degradation and very little (1-2%) 14C-residues of the applied activity were detected after two months in sediments. Clams were major component of the ecosystem and played a significant role in degradation of the insecticide. In the continuous flow system chlorpyrifos did not undergo substantial mineralization. Volatilization accounted for 0.8-1% loss during first ten days of application. The amounts of extractable 14C-activity were higher in flooded sediments than in moist sediment. More bound residues were formed under moist conditions. TCP (3,5,6-trichloro-2-pyridinol) was the major degradation product formed under both moist and flooded conditions, its formation being higher in the latter conditions. These studies underline the role of clams in degradation of chlorpyrifos and lack of microbial degradation. In absence of clams, chlorpyrifos underwent abiotic degradation in marine sediment with formation of bound residues.

Degradation of 14C-DDT was studied in a marine ecosystem for 60 days and in marine sediments under moist and flooded conditions using a continuous flow system for a period of 130 days. 14C-DDT residues were recovered in sediments of the marine ecosystem at uniform level of 60-65% of the applied 14C-activity throughout the incubation period. DDD was a major metabolite in sediments while DDMU was a major metabolite in clams. Clams brought about substantial degradation of DDT. However, 14C-residues recovered form clams are not suggestive of significant bioaccumulation. In the continuous flow experiment, under both moist and flooded conditions, DDT underwent degradation and about 22% of the applied 14C-activity was recovered as volatiles under both conditions. In sediments, extractable 14C-residues accounted for about 30 and 19% under moist and flooded conditions, respectively. DDT was the major compound in extractable residues as identified by TLC-autoradiographic procedures. More bound residues were formed under flooded than under moist conditions.

Trichoderma pseudokoningii MTCC 3011 is a very useful strain for biological control of the plant pathogen Sclerotium rolfsii under post-harvest conditions. In the present investigation, several benomyl-tolerant phenotypic mutants of this strain have been generated using a two step mutagenesis-chemical followed by gamma irradiation. The mutants differed from the wild type strain in antibiotic and disease control potential. Some of the mutants are superior to the wild type in biocontrol potential on S. rolfsii.