Reductive Dechlorination Of DDT Research Articles

Enhancement of the DDT reductive dehalogenation by different cosubstrates: Role of sulfidogenic and biogeochemical processes in soil

Reductive dechlorination of DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane) in soil is an important pathway to favor its transformation to DDD (1,1-dichloro-2,2-bis(4-chlorophenyl) ethane) under anaerobic conditions. The reductive dechlorination has been reported to be coupled to the dissimilatory iron reduction and sulfate reduction processes. The aim of this study was to evaluate the reductive degradation of DDT using different types of cosubstrates (electron donors) to stimulate the sulfidogenic process in a pretreated zero-valent iron soil (ZVI-P soil). The addition of easily assimilable cosubstrates (glucose, ethanol, and lactic acid) at a concentration of 2.5 ± 0.1 mgC g−1dry soil, as well as a complex cosubstrate (sugarcane bagasse, 2.5, 5, and 10%, w/w), enhanced the degradation of DDX (i.e., DDT and its degradation products). The highest degradation of DDT (96.1%), DDD (58.3%), DDE (43.9%), and DDNS (54.7%) was observed with the sugarcane bagasse (10% w/w) treatment. The biogeochemical transformation of gypsum and goethite into reactive iron sulfide species (mackinawite, Fe1+xS) suggested that the reductive dehalogenation of DDT to DDD was mediated abiotically for this sulfide species, while the degradation of DDD, DDNS, and DDE may have been linked to the bacterial consortia synergism favored during lignocellulose degradation. Members of the Firmicutes, Proteobacteria, and Actinobacteria were the dominant microorganisms in the soil amended with sugarcane bagasse. This indicated that DDX degradation in ZVI-P treated soil was related to abiotic and biotic processes.

Persistent organic pollutants in wood fiber\u2013contaminated sediments from the Baltic Sea

PurposeMany coastal areas in the Baltic Sea are contaminated with wood fiber and pollutants from pulp and paper industries. These anthropogenic, organic-rich, sediments (fiberbanks) have not been characterized and knowledge about their role as secondary sources for dispersal of persistent organic pollutants (POPs) is limited. Hence, the aim of this study was to elucidate the fate of POPs and the relationships between sorption (KD and KTOC), sediment type, and compound hydrophobicity (KOW) in fiber-contaminated sediments.Materials and methodsPaired sediment and pore water samples (n = 24 sites) from three fiber-contaminated areas, located in the Ångermanälven river estuary in northern Sweden, were analyzed for POPs (viz. PCBs, DDT, and HCB) in sediment types representing different fiber content (i.e., fiberbanks, fiber-rich sediments, and natural less fiber impacted sediments). The freely dissolved concentration in sediment pore water was determined by sediment-polyoxymethylene (POM) partitioning. Instrumental analysis was performed using gas chromatography coupled to a triple quadrupole mass spectrometer (GC-MS/MS).Results and discussionHigher levels of total organic carbon (TOC) were found in the fiberbank sediment (range 8.6–37%) than in fiber-rich sediment (range 2.0–6.5%) and more natural sediment (range 2.0–2.9%). The sediment concentrations of POPs (dry weight basis) were also found to be significantly (p < 0.05) elevated in fiberbanks compared to the other sediment types. The fraction of DDD (48–66% of Σ6DDX) was larger in fiberbanks than in the other sediment types, likely due to anoxic conditions favoring reductive dechlorination of DDT. When sediment levels were normalized to TOC, HCB displayed similar levels across sediment type, suggesting a more diffuse source pattern than for PCB and DDT. Although significantly higher sorption (KD) of POPs was observed in fiberbanks, pore water levels were still elevated due to high bulk concentrations.ConclusionsThis study shows that fiberbanks are coastal hot spots for POPs in the Baltic Sea and that the levels are of ecotoxicological concern. Although the POPs are more strongly sorbed (KD) to this type of organic rich sediment, the high pore water concentrations in fiberbanks compared to the other sediment types investigated show that the risk of contaminant dispersal via pore water is elevated for fiberbanks.

Kinetics of Reductive Dechlorination of DDT in Soil with Zero-Valent Iron

In this study, reductive dechlorination of DDT compounds by zero-valent iron in Jiangxi red soil was investigated. DDT compounds were effectively dechlorinated by zero-valent iron. The pseudo-first-order kinetic model for 2,4¢-DDT and 4,4¢-DDT reduction with zero-valent iron was proposed. The reaction rate constants for 2,4¢-DDT and 4,4¢-DDT were 1.19´10-2(min-1) and 1.44´10-2(min-1), respectively. The dechlorination of 2,4¢-DDT and 4,4¢-DDT were mainly affected by the specific surface area of iron. The data from the variable-pH experiments (between 3.6 and 8.8) suggested that pH does not play a role in the rate-determination step.

Degradation of chlorinated pesticide DDT by litter-decomposing basidiomycetes

One hundred and two basidiomycete strains (93 species in 41 genera) that prefer a soil environment were examined for screening of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) biodegradation. Three strains within two litter-decomposing genera, Agrocybe and Marasmiellus, were selected for their DDT biotransformation capacity. Eight metabolites; 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (DDD), two monohydroxy-DDTs, monohydroxy-DDD, 2,2-dichloro-1,1-bis(4-chlorophenyl)ethanol, putative 2,2-bis(4-chlorophenyl)ethanol and two unidentified compounds were detected from the culture with Marasmiellus sp. TUFC10101. A P450 inhibitor, 1-ABT, inhibited the formation of monohydroxy-DDTs and monohydroxy-DDD from DDT and DDD, respectively. These results indicated that oxidative pathway which was catalyzed by P450 monooxygenase exist beside reductive dechlorination of DDT. Monohydroxylation of the aromatic rings of DDT (and DDD) by fungal P450 is reported here for the first time.

Multielectron Transfer at Heme-Functionalized Nanocrystalline TiO2: Reductive Dechlorination of DDT and CCl4 Forms Stable Carbene Compounds

Hemin (chloro(protoporhyrinato)iron(III)) was found to bind to mesoporous nanocrystalline (anatase) TiO2 thin films from dimethyl sulfoxide solution, Keq=10(5) M-1 at 298 K. Band gap illumination in methanol reduced hemin to heme and led to the appearance of TiO2 electrons, heme/TiO2(e-). Reactions of heme/TiO2(e-) with CCl4 or 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) led to the formation of stable carbene products in greater than 60% yield. The spectroscopic data are fully consistent with a dissociative two-electron organohalide reduction mechanism of CCl4 and DDT to yield (protoporhyrinato)FeIICCl2 and (protoporhyrinato)FeIIC=C(p-Cl-phenyl)2 respectively.

Reductive dechlorination of DDT to DDD by rat blood.

The present study provides evidence that the reductive dechlorination of DDT (p, p'-dichlorodiphenyltrichloroethane) to DDD (p, p'-dichlorodiphenyldichloroethane) mediated by rat blood proceeds in the presence of both a reduced pyridine nucleotide and a flavin. The reduction appears to proceed in two steps. The first step is reduction of a flavin such as FAD, FMN or riboflavin by NADPH or NADH, either enzymatically or nonenzymatically. The second step is nonenzymatic reductive dechlorination of DDT by the reduced flavin, catalyzed by the heme group of hemoglobin.

Enzymatic detoxication of DDT to DDD by rat liver: effects of some inducers and inhibitors of cytochrome P-450 enzyme system.

DDT, in very first step of its detoxication is either transformed to DDD by reductive dechlorination (Walker i969; Hassal 1973) or DDE by dehydrochlorination (Datta 1970). For further detoxication, these metabolites undergo a series of reactions which result in the elimination of DDA in urine (Peterson and Robison 1964; Datta 1970; Gold and Brunk 1982). However, enzymes involved at various steps of DDT-detoxication are not well understood. In general, these reactions are believed to be mediated by cytochrome P-450 containing enzyme system. In earlier studies, nonenzymatic conversion of DDT to DDD was suggested (Jefferies and Walker 1966; Bunyan et al. 1966). Later, Hassal (1973) demonstrated that DDD is formed in liver in at least two ways; one protein dependent and other relatively heat resistant system. The enzyme(s) involved in the reductive dechlorination of DDT to DDD are not well known. Morello (1965) reported the induction of enzyme activity that transforms DDT to DDD in rats preadministered with multiple doses of DDT. Walker (1969) suggested the possible role of cytochrome P-450 in the conversion of DDT to DDD on the basis of inhibition by CO and the absolute requirement of NADPH for the reaction. However, studies on the in vivo and in vitro effects of some classic inducers and inhibit~Tcytochr ome ~450 system on the reductive dechlorination of DDT will much effectively clear the role of this enzyme system in the above conversion. Instead of the multiple administration of DDT (Morello 1965), it would be more desirable to investigate a single threshold dose of DDT for the stimulation of the enzyme involved in the reductive dechlorination of DDT. As far we know, no enzyme has been characterized for the detoxication of DDT to DDD. Therefore, DDD forming activity will be referred to as 'reductase' in this report. This paper describes the enzymatic detoxication of DDT to DDD by rat liver preadministered with a single threshold dose of DDT. Further, effects of some inducers and inhibitors of cytochrome P-450 enzyme system on the detoxication of DDT to DDD are reported. Send reprint requests to S S A Zaidi at the above address.

The postmortem reductive dechlorination of pp′DDT in avian tissues

Pigeons, Bengalese finches, and Japanese quail were dosed with pure pp′DDT, and their tissues were examined for residues immediately after death, or following storage. DDD residues in livers extracted immediately after death were always low (<5% DDT concentration) and sometimes undetectable. Reductive dechlorination of DDT to DDD occurred postmortem, relatively repidly at 20°C (90% after 8 hr), but more slowly at −10 and −20°C. The conversion could not be attributed to bacterial action and was evidently due to processes operating within the cell under anaerobic conditions. During storage at −12 to −15°C, reductive dechlorination occurred in brain and in embryos, but did not occur to any significant extent in depot fat or in eggs without embryos. These findings raise questions about the importance of DDD as an in vivo metabolite in birds and other vertebrates. The interpretation of DDD residues in tissues from laboratory and field studies is discussed.

Reductive dechlorination of DDT by haem proteins

DDT is converted to DDD by reduced myoglobin (rapidly), cytochrome c oxidase, and a haem-containing undecapeptide derived from cytochrome c. Cytochrome c itself is inactive. This demonstrates that an accessible haem site is necessary for the reaction. Spectrophotometric evidence is presented for an interaction between DDT and the undecapeptide. These results cast light on one of the biological pathways for the breakdown of DDT.

Species and sex differences in the reductive dechlorination of DDT by supplemented liver preparations

p, p′-DDT was converted to DDD, 1,1-dichloro-2,2-bis( p-chlorophenyl)ethane, by unheated 12,000 g supernate supplemented with NADPH, made from liver of rat, mouse, hamster, quail, chicken and pigeon. The additional presence of exogenous riboflavin did not augment reduction. If, however, riboflavin was added to unheated microsomes supplemented with NADPH or NADH the rate of reduction was more than doubled. Heated 12,000 g supernate, unsupplemented or containing only exogenous riboflavin, did not reduce DDT. When NAD(P)H was present, big species differences in activity occurred, the pigeon and cockerel scarcely reducing any DDT in 2 hr, the Wistar rat supernate being most active. Addition to heated 12,000 g supernate of 30 μg riboflavin as well as NAD(P)H resulted in increased reductive activity for all six species. The species difference in effect of exogenous riboflavin between the pigeon and rat was also observed using four DDT analogs as substrates. A sex-related difference in activity of preheated, supplemented 12,000 g supernate from livers of the chicken and Norwegian hooded rat was not found when unheated preparations were used. In contrast to the activity possessed by preheated 12,000 g supernate of rat liver supplemented with NAD(P)H, similarly supplemented preheated microsomes did not reduce DDT. On adding riboflavin as well as NAD(P)H, however, preheated hepatic microsomes of both pigeon and rat produced DDD, and this activity was further increased by addition of unheated microsomal (105,000 g) supernate. The biocatalytic system functioning in preheated preparations appears to need at least one component of heated microsomes, NAD(P)H and one or more water-soluble components.

Reductive dechlorination of DDT by heated liver.

DDT undergoes reductive dechlorination in vertebrate liver after death and in liver preparations incubated in anaerobic conditions. The product, DDD, p, p′-dichlorodiphenyldichloro-ethane, is an important environmental pollutant and has been found in tissues of many animals1, including human liver2. Although there is evidence that reductive dechlorination by vertebrate liver is NADPH-dependent and takes place when microsomes and DDT are incubated in nitrogen3, other investigators4 have suggested that the reaction could be non-enzymatic.

Effect of Cooking Utensil Composition and Contents on the Reductive Dechlorination of DDT to DDD

Abstract The reductive dechlorination of DDT to DDD by some cooking utensil compositions and contents is demonstrated and the identification of specific reducing agents of DDT is investigated. Iron is found to be the most active reducing agent of DDT. A progressive loss of DDT and accumulation of DDD from DDT are observed when DDT standard is boiled with double-distilled water in metal utensils (iron, stainless steel, or aluminum) or in glass utensils containing iron powder. Non-metal utensils (Teflon, glass, or enamel) by themselves do not give an accumulation of DDD from DDT despite considerable loss of DDT. Teflon-coated utensils are ineffective in the reduction of DDT and tend to adsorb pesticides on their surface. A substance (or substances) which is present in vegetables also acts as a DDT-reducing agent as shown by boiling DDT with vegetables in glass utensils.

The metabolism of DDT in stored wheat grains

DDT applied to wheat grains is slowly converted to DDE and DDD under aerobic and anaerobic conditions of storage respectively. It seems likely that iron-porphyrin compounds concerned in the peroxidation of unsaturated fatty acids are implicated in the (anaerobic) reductive dechlorination of DDT, which occurs primarily in the germ tissues.

Reductive Dechlorination of DDT by Escherichia coli

Reductive Dechlorination of DDT by Escherichia coli

Metabolites: Reductive Dechlorination of DDT to DDD and Isomeric Transformation of o,p’-DDT to p,p’-DDT In Vivo

Abstract Feeding p,p’-DDT and o,p’-DDT separately at a level of 50 ppm in the diet of rats causes reductive dechlorination of DDT to DDD in the liver. No DDD was found in the fat. DDE is not involved in the metabolic pathway. Feeding o,p’-DDT yields evidence of isomeric conversion to p,p’-DDT in the fat stores. The proportion of the p,p’-DDT found to the o,p’-isomer observed is approximately 7:1.

Announcements

Announcements

Erratum: Reductive Dechlorination of DDT to DDD by Yeast

In the report "Reductive dechlorination of DDT to DDD by yeast," by B. J. Kallman and A. K. Andrews [ Science 141, 1050 (13 Sept. 1963)] there are two errors in Fig. 1. Structure II requires a para chlorine on the second benzene ring, and in structure III the group bound to the carbon atom between the rings should have been Cl-C-H instead of Cl-C-Cl.