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PubMed2005

Quantum yields for Cl(2P(j)) atom formation from the photolysis of chlorofluorocarbons and chlorinated hydrocarbons at 193.3 nm.

Cl(2P(3/2)) and Cl*(2P(1/2)) atoms produced from the photodissociation of chlorofluorocarbons (CFCs) and chlorinated hydrocarbons at 193.3 nm have been detected quantitatively by a technique of vacuum ultraviolet laser-induced fluorescence (VUV-LIF) spectroscopy at 135.2 and 134.7 nm for j = 1/2 and 3/2, respectively. The quantum yields for total Cl-atom formation in the 193.3 nm photolysis at 295 +/- 2 K have been determined to be 1.03 +/- 0.09, 1.01 +/- 0.08, 1.03 +/- 0.08, 1.03 +/- 0.10, 1.41 +/- 0.14, 1.02 +/- 0.08, and 0.98 +/- 0.08 for CF2Cl2, CFCl3, CH2Cl2, CHCl3, CCl4, CHFCl2, and CCl3CF3, respectively. Those results suggest that the single C-Cl bond rupture always occurs in the photolysis of these molecules except for CCl4. Formation of two Cl atoms partly takes place in the photodissociation of CCl4. The quantum yields for total Cl-atom formation in the 193.3 nm photolysis of CHBr2Cl and CHBrClCF3 are 0.27 +/- 0.02 and 0.28 +/- 0.02, respectively, which suggests that the C-Br bond rupture is a main channel in the photodissociation processes. The branching ratios between the spin-orbit states, Cl*(2P(1/2)) and Cl(2P(3/2)), have also been determined for the photodissociation of the chlorinated compounds at 193.3 nm. The UV photodissociation processes giving rise to formation of Cl(2P(j)) atoms from the chlorinated compounds studied here have been discussed.

Journal Article↗
PubMed2003

Synergy of combining sonolysis and photocatalysis in the degradation and mineralization of chlorinated aromatic compounds.

Merits of using advanced oxidation processes such as sonolysis and photocatalysis as well as a combination of the two have been explored using model herbicides such as 2,4-dichlorophenoxy acetic acid and 2,4-dichlorophenoxypropionic acid and the chlorinated phenols 2,4-dichlorophenol and 2,4,6-trichlorophenol. Whereas sonolysis is quite effective in the initial degradation of chlorinated aromatic molecules, complete mineralization is difficult to achieve. Photocatalysis is selective toward the degradation of polar compounds but causes the build up of undesirable chemical intermediates. In contrast to sonolytic degradation, photocatalysis is very effective toward achieving complete mineralization. By simultaneously carrying out high-frequency sonolysis and photocatalysis we have succeeded in achieving faster and complete mineralization with no build up of toxic intermediates even at very low catalyst loadings. The synergy of combining the two advanced oxidation processes is discussed.

Environmental Pollution↗
PubMed1994

Polychlorinated biphenyls (PCBs) in the UK population: estimated intake, exposure and body burden.

This paper presents a detailed congener-specific estimate of PCB exposure to the UK population. The average sigma PCB intake (i.e. the sum of IUPAC congeners No. 28, 44, 52, 61/74, 66, 99, 101, 105, 110, 118, 138, 151, 153, 156, 170, 180, 183, 187, 189, 194/205, 201, 202, 206 and 209) for the contemporary UK population was estimated to be 0.53 micrograms/person/day. Food consumption accounted for 97% of the sigma PCB exposure, with fish, milk and dairy products, vegetables and meat and animal fat accounting for 32, 24, 24 and 15%, respectively. The congener pattern for different food products varied, with vegetables playing a major part in the intake of lower chlorinated compounds, whilst fatty foods such as fish, dairy products and meat, were of greater importance for the intake of higher chlorinated compounds. Theoretical body burdens and body fat concentrations of selected PCB congeners were derived for the UK population, based on the estimated contemporary human daily intake of PCBs and a number of assumptions. PCB body burdens and adipose tissue concentrations were generally predicted to increase with age. However, adipose concentrations increased at a slower rate in the older population, due to a dilution effect caused by the increase in body fat weight with age. These theoretical estimates were then compared with measured values for adipose tissue from the Welsh population. Theoretical body burdens and adipose tissue concentrations (not accounting for any metabolic losses) were below the actual values measured for the contemporary Welsh population by between a factor of 2.5 and 4. This discrepancy becomes greater when metabolic losses are included, and probably occurs because present day exposure to PCBs through foodstuffs is likely to be lower than in the past. The lower chlorinated congener No. 28 is more readily removed from the body and is predicted to reach an equilibrium concentration in humans. In contrast, the higher chlorinated No. 153 was predicted to accumulate in the body throughout life. The effect of PCB transfer via breast milk is shown to be important in lowering the body burden of the mother (by approximately 20% over 3 months) and substantially increasing that in the offspring.

Adipose Tissue↗
PubMed2003

Zinc and mechanical prowess in the jaws of Nereis, a marine worm.

Higher animals typically rely on calcification to harden certain tissues such as bones and teeth. Some notable exceptions can be found in invertebrates: The fangs, teeth, and mandibles of diverse arthropod species have been reported to contain high levels of zinc. Considerable quantities of zinc also occur in the jaws of the marine polychaete worm Nereis sp. High copper levels in the polychaete worm Glycera dibranchiata recently were attributed to a copper-based biomineral reinforcing the jaws. In the present article, we attempt to unravel the role of zinc in Nereis limbata jaws, using a combination of position-resolved state-of-the-art techniques. It is shown that the local hardness and stiffness of the jaws correlate with the local zinc concentration, pointing toward a structural role for zinc. Zinc always is detected in tight correlation with chlorine, suggesting the presence of a zinc-chlorine compound. No crystalline inorganic phase was found, however, and results from x-ray absorption spectroscopy further exclude the presence of simple inorganic zinc-chlorine compounds in amorphous form. The correlation of local histidine levels in the protein matrix and zinc concentration leads us to hypothesize a direct coordination of zinc and chlorine to the protein. A comparison of the role of the transition metals zinc and copper in the jaws of two polychaete worm species Nereis and Glycera, respectively, is presented.

Animals↗
PubMed1988

[Volatile organochlorine compounds in human tissue].

Between November 1978 and June 1979 a total of 150 tissue sample (subcutaneous adipose tissue, perinephric fat, liver, lung and muscle tissue) from 30 autopsy cases were examined for their content of volatile organic chlorinated compounds. The ages of the deceased ranged from 29 to 82 years, whereas the majority was 60-70 years old and most were male. Volatile organic chlorinated compounds are detected in all tissue samples investigated. The compounds chloroform, 1,1,1-trichloroethane, carbon tetrachloride, trichloroethylene and tetrachloroethylene are always found. The mean values vary between 2 and 25 micrograms/kg wet tissue. The values increase from carbon tetrachloride over 1,1,1-trichloroethane, trichloroethylene and tetrachloroethylene to chloroform. With the exception of 1,1,1-trichloroethane much lower values are found in the liver, lung and muscle tissues than in the fatty tissues. The mean value of chloroform detected in subcutaneous adipose tissue amounted to 23,4 micrograms/kg wet tissue, in perinephric fat 24.8 micrograms/kg, in liver tissue 10.8 micrograms/kg, in lung tissue 9.9 micrograms/kg and in muscle tissue 10.0 micrograms/kg. Maximum values are 10 to 20 times higher. The chloroform content of the tissues increase with age and reach a maximum between 50 and 70 years of age. This increase is not influenced by the fat content of the tissues.

Adipose Tissue↗
PubMed1996

Are chlorine-free compounds a solution for health problems caused by ozone-depleting substances?

In January 1996, the Government of Croatia and United Nations Environment Programme (UNEP) signed an agreement on the phasing out of ozone-depleting substances in Croatia, making the problem of identifying adequate substitutes a high priority. In this paper, the main ecologic characteristics of chlorine-containing fully halogenated chlorofluorocarbons (CFCs) and partially halogenated chlorofluorocarbons (HCFCs) compared with chlorine-free hydrofluorocarbons (HFCs) are presented. The data showed HCFCs to be ecologically more acceptable than CFCs, particularly regarding the ozone-depleting potential (ODP), and have therefore been proposed as substitutes for CFCs. However, although having lower ODP, long-term they could still harm the stratospheric ozone layer, and are therefore hardly acceptable. HFCs are promising substitutes which, having no chlorine, have no ODP. Six were toxicologically evaluated; three of them were found flammable. Toxicological characteristics of three nonflammable compounds (HFC 125, HFC 134a and HFC 227ea) are presented. Their toxicity, not yet completely evaluated, appears to be low.

Animals↗
PubMed2005

Dependence of mechanochemically induced decomposition of mono-chlorobiphenyl on the occurrence of radicals.

Mechanochemically induced dechlorination of mono-chlorobiphenyl (BP-Cl) on the surfaces of metal oxides was compared with that on metal hydroxides, using the three metals of Mg, Al, and La as examples. The metal oxides, such as gamma-alumina (gamma-Al2O3), magnesium oxide (MgO) and lanthanum oxide (La2O3) showed an efficient ability to dechlorinate the BP-Cl; however, BP-Cl remained in the ground samples when the hydroxides were used. From the product analysis using gas chromatography/mass spectrometry (GC/MS) and electron spin resonance (ESR) measurements, it was confirmed that the charge transfer from the O2- site on the surface of the oxide additives due to the intense grinding has plays a significant role in the decomposition of the chlorinated compound. Based on the observed dependence of the dechlorination on the radical occurrence, some practical methods were proposed to improve the destruction efficiency of the chlorinated organic compounds.

Aluminum Hydroxide↗
PubMed1984

Microbial biodegradation of 4-chlorobiphenyl, a model compound of chlorinated biphenyls.

The biodegradation products of 4-chlorobiphenyl were analyzed in an Achromobacter sp. strain and a Bacillus brevis strain. Both strains generated the same metabolites, with 4-chlorobenzoic acid as the major metabolic product. Our results corroborate previous observations whereby most bacterial strains degrade the chlorobiphenyls via a major pathway which proceeds by an hydroxylation in position 2,3 and a meta-1,2 fission. However, we also detected several metabolites whose structure suggests the existence of other routes for the degradation of chlorinated biphenyls.

Alcaligenes↗
PubMed2004

Coupled reduction of chlorinated hydrocarbons and heavy metals by zerovalent silicon.

The feasibility of using zerovalent silicon (Si0) as a novel reductant to remove chlorinated compounds and heavy metals in contaminated sites was investigated. The kinetics and degradation mechanism of carbon tetrachloride (CT) by Si0 were also examined. Results showed that zerovalent silicon could effectively dechlorinate the chlorinated compounds. A nearly complete dechlorination of CT by Si0 was obtained within 14 h. The produced concentrations of chloroform (CF) accounted for 71-88% loss of CT, showing that reductive dechlorination is the major degradation pathway for the degradation of chlorinated hydrocarbons by Si0. The degradation followed pseudo first-order kinetics and the normalized surface reaction rate constant (k(sa)) for CT dechlorination ranged between 0.0342 and 0.0454 L m(-2) h(-1) when CT concentrations were in the range of 3-20 microM. A linear relationship between the k(sa) and pH value was also established. In addition, zerovalent silicon has a high capability in the removal of heavy metals. 83% of Cr(VI) was removed by 0.5g Si0 within 5 h, which is higher than that by Fe0. The removal efficiency of divalent metal ions by Si0 followed the order of Cu(II) > Pb(II) > Ni(II). This indicates that zerovalent silicon is an alternative reductant and can undergo coupled reduction of heavy metals and chlorinated hydrocarbons in contaminated groundwater.

Carbon Tetrachloride↗
PubMed2004

Aerobic biodegradation of vinyl chloride by a highly enriched mixed culture.

Lower chlorinated compounds such as cis-dichloroethene (cis-DCE) and vinyl chloride (VC) often accumulate in chloroethene-contaminated aquifers due to incomplete reductive dechlorination of higher chlorinated compounds. A highly enriched aerobic culture that degrades VC as a growth substrate was obtained from a chloroethene-contaminated aquifer material. The culture rapidly degraded 50-250 microM aqueous VC to below GC detection limit with a first-order rate constant of 0.2 day(-1). Besides VC, the culture also degraded ethene as the sole carbon source. In addition, the culture degraded cis-DCE, but only in the presence of VC. However, no degradation of trans-DCE or TCE occurred either in the presence or absence of VC. The ability of the TRW culture to degrade cis-DCE is significant for natural attenuation since both VC and cis-DCE are often found in chloroethene-contaminated groundwater. Experiments examining the effect of oxygen threshold on VC degradation showed that the culture was able to metabolize VC efficiently at extremely low concentrations of dissolved oxygen (DO). Complete removal of 150 micromoles of VC occurred in the presence of only 0.2 mmol of oxygen (1.8 mg/L DO). This is important since most groundwater environments contain low DO (1-2 mg/L). Studies showed that the culture was able to withstand long periods of VC starvation. For example, the culture was able to assimilate VC with minimal lag time even after 5 months of starvation. This is impressive from the point of its sustenance under field conditions. Overall the culture is robust and degrades VC to below the detection limit rendering this culture suitable for field application.

Aerobiosis↗
PubMed2005

Simultaneous anaerobic-aerobic biodegradation of halogenated phenolic compound under oxygen-limited conditions.

The successful application of co-immobilized aerobic-anaerobic biomass under limited aeration in wastewater treatment systems would eliminate the problems associated with the intermediates mono-chlorophenol (MCP) and di-chlorophenol(DCP) accumulations. With low initial pentachlorophenol (PCP) concentration, all PCP could be completely removed under oxygen-limited strict anaerobic conditions, and the removal efficiencies with different initial headspace oxygen percentage (IHOP) were not obviously different from each other. While at high initial PCP concentration, under strictly anaerobic conditions PCP and their intermediates were clearly higher than that under other conditions, and produced obvious accumulation, the highest PCP reduction was achieved by the system receiving 30 IHOP, oxygen-limited system also exhibited lower residual TOC concentration and lower concentration of metabolic intermediates MCP and DCP. These results suggested that under strictly anaerobic condition the reductive dechlorination of low chlorinated compounds became rate limiting in the reductive dechlorination pathway, less chlorinated compounds be more amenable to aerobic degradation, and the aerobes of outer layers could function under limited oxygen. The co-immobilized aerobic-anaerobic biomass for methanogenesis under limited-aeration for chlorophenol degradation might be an attractive and efficient alternative for the sequential anaerobic/aerobic system to achieve mineralization of a broad range of recalcitrance highly chlorinated organics and low final TOC concentrations.

Anaerobiosis↗
PubMed1987

Microbial degradation of chlorinated aromatic compounds.

Many microorganisms are capable of utilizing anthropogenic chloroaromatics as the sole source of carbon and energy. Techniques of co-cultivation, conjugation, and in vitro cloning have been used to extend the range of haloaromatic degradation in bacteria. Employment of suitable 'degrader' strains may contribute significantly towards the removal of these compounds from the environment.

Alcaligenes↗
PubMed1994

[Effects of chloroform, chlorobenzene and polychlorinated biphenyls on erythrocyte lipid peroxidation and membrane fluidity in poisoned rabbits].

Effects of three chlorinated compounds, i.e., chloroform, chlorobenzene and Aroclor 1254 (PCBs), on lipid peroxidation and membrane fluidity of erythrocytes in poisoned rabbits were studied. Results revealed daily intraperitoneal injection of peanut oil containing chlorinated compounds into rabbits showed nonenzymic promotion effects on its erythrocyte lipid peroxidation in varying degrees, but different effects on erythrocyte membrane fluidity, promoting by chloroform and inhibiting by Aroclor 1254. It suggested the constitutional characteristics of toxicant molecules also had effects on membrane fluidity. In addition, it was found there existed potential relationship between maintenance of cell morphology and membrane fluidity.

Animals↗
PubMed2006

Bank security dye packs: synthesis, isolation, and characterization of chlorinated products of bleached 1-(methylamino)anthraquinone.

Banknote evidence is often submitted after a suspect has attempted to disguise or remove red dye stain that has been released because of an anti-theft device that activates after banknotes have been unlawfully removed from bank premises. Three chlorinated compounds have been synthesized as forensic chemical standards to indicate bank security dye bleaching as a suspect's intentional method for masking a robbery involving dye pack release on banknotes. A novel, facile synthetic method to provide three chlorinated derivatives of 1-(methylamino)anthraquinone (MAAQ) is presented. The synthetic route involved Ultra Clorox bleach as the chlorine source, iron chloride as the catalyst, and MAAQ as the starting material and resulted in a three-component product mixture. Two mono-chlorinated isomers (2-chloro-1-(methylamino)anthraquinone and 4-chloro-1-(methylamino)anthraquinone) and one di-chlorinated compound (2,4-dichloro-1-(methylamino)anthraquinone) of the MAAQ parent molecule were detected by gas chromatography mass spectrometry (GC-MS), and subsequently isolated by liquid chromatography (LC) with postcolumn fraction collection. Although GC-MS is sensitive enough to detect all of the chlorinated products, it is not definitive enough to identify the structural isomers. Liquid-state nuclear magnetic resonance (NMR) spectroscopy was utilized to elucidate structurally the ortho- and para-mono-chlorinated isomers once enough material was properly isolated. A reaction mechanism involving iron is proposed to explain the presence of chlorinated MAAQ species on stolen banknotes after attempted bleaching.

Journal Article↗