• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 10
  • 3
  • 1
  • 1
  • Tagged with
  • 16
  • 10
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Cytochrome P4501A Induction by Highly Purified Hexachlorobenzene in Primary Cultures of Avian Hepatocytes

Mundy, Lukas 05 October 2011 (has links)
Hexachlorobenzene (HCB) is a persistent organic pollutant that was primarily produced for use as a fungicide dating back to the 1940s. Worldwide emissions have declined steadily over the past forty years, but HCB is still produced as a by-product of a number of industrial processes and is still detected in remote locations around the globe. Many studies have been conducted to determine the toxic and biochemical effects of HCB, but it has been suggested that reported toxic and biochemical effects initially attributed to HCB exposure may have actually been elicited by contamination of HCB by polychlororinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs). This thesis investigates whether highly purified HCB (HCB-P; defined as HCB containing < 0.2 ppb of any PCDD, PCDF, or co-planar PCB congener [the detection limit of current analytical methods]) can induce cytochrome P4501A (CYP1A) in three avian species in vitro. Primary cultures of chicken (Gallus gallus domesticus), ring-necked pheasant (Phasianus colchicus) and Japanese quail (Corturnix japonica) embryo hepatocytes were used to compare the potencies of reagent-grade (RG-HCB), HCB-P and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as inducers of ethoxyresorufin O-deethylase (EROD) activity, CYP1A4 messenger ribonucleic acid (mRNA) and CYP1A5 mRNA. The potencies of two mono-ortho substituted PCBs, 2,3,3’,4,4’-pentachlorobiphenyl (PCB 105) and 2,3’,4,4’,5-pentachlorobiphenyl (PCB 118) were also assessed in chicken embryo hepatocytes using the same endpoints. All compounds induced EROD activity and up-regulated CYP1A4/5 mRNAs in the hepatocytes of each species. The potency of HCB relative to the potency of TCDD (ReP) was 0.0001, 0.001 and 0.01 in chicken, ring-necked pheasant and Japanese quail embryo hepatocytes, respectively. ECthreshold values were suggested to be more appropriate than EC50 values because ECthreshold values account for differences in maximal EROD and CYP1A4/5 mRNA levels that are observed with HCB exposure in avian embryo hepatocytes more so than EC50 values. Differences in species sensitivity to HCB were also assessed, and did not vary as greatly as the listed ReP values. The results presented herein suggest that HCB is capable of inducing effects downstream of activation of the aryl hydrocarbon receptor, and may warrant its inclusion in the World Health Organization’s toxic equivalency concept.
2

Cytochrome P4501A Induction by Highly Purified Hexachlorobenzene in Primary Cultures of Avian Hepatocytes

Mundy, Lukas 05 October 2011 (has links)
Hexachlorobenzene (HCB) is a persistent organic pollutant that was primarily produced for use as a fungicide dating back to the 1940s. Worldwide emissions have declined steadily over the past forty years, but HCB is still produced as a by-product of a number of industrial processes and is still detected in remote locations around the globe. Many studies have been conducted to determine the toxic and biochemical effects of HCB, but it has been suggested that reported toxic and biochemical effects initially attributed to HCB exposure may have actually been elicited by contamination of HCB by polychlororinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs). This thesis investigates whether highly purified HCB (HCB-P; defined as HCB containing < 0.2 ppb of any PCDD, PCDF, or co-planar PCB congener [the detection limit of current analytical methods]) can induce cytochrome P4501A (CYP1A) in three avian species in vitro. Primary cultures of chicken (Gallus gallus domesticus), ring-necked pheasant (Phasianus colchicus) and Japanese quail (Corturnix japonica) embryo hepatocytes were used to compare the potencies of reagent-grade (RG-HCB), HCB-P and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as inducers of ethoxyresorufin O-deethylase (EROD) activity, CYP1A4 messenger ribonucleic acid (mRNA) and CYP1A5 mRNA. The potencies of two mono-ortho substituted PCBs, 2,3,3’,4,4’-pentachlorobiphenyl (PCB 105) and 2,3’,4,4’,5-pentachlorobiphenyl (PCB 118) were also assessed in chicken embryo hepatocytes using the same endpoints. All compounds induced EROD activity and up-regulated CYP1A4/5 mRNAs in the hepatocytes of each species. The potency of HCB relative to the potency of TCDD (ReP) was 0.0001, 0.001 and 0.01 in chicken, ring-necked pheasant and Japanese quail embryo hepatocytes, respectively. ECthreshold values were suggested to be more appropriate than EC50 values because ECthreshold values account for differences in maximal EROD and CYP1A4/5 mRNA levels that are observed with HCB exposure in avian embryo hepatocytes more so than EC50 values. Differences in species sensitivity to HCB were also assessed, and did not vary as greatly as the listed ReP values. The results presented herein suggest that HCB is capable of inducing effects downstream of activation of the aryl hydrocarbon receptor, and may warrant its inclusion in the World Health Organization’s toxic equivalency concept.
3

Cytochrome P4501A Induction by Highly Purified Hexachlorobenzene in Primary Cultures of Avian Hepatocytes

Mundy, Lukas 05 October 2011 (has links)
Hexachlorobenzene (HCB) is a persistent organic pollutant that was primarily produced for use as a fungicide dating back to the 1940s. Worldwide emissions have declined steadily over the past forty years, but HCB is still produced as a by-product of a number of industrial processes and is still detected in remote locations around the globe. Many studies have been conducted to determine the toxic and biochemical effects of HCB, but it has been suggested that reported toxic and biochemical effects initially attributed to HCB exposure may have actually been elicited by contamination of HCB by polychlororinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs). This thesis investigates whether highly purified HCB (HCB-P; defined as HCB containing < 0.2 ppb of any PCDD, PCDF, or co-planar PCB congener [the detection limit of current analytical methods]) can induce cytochrome P4501A (CYP1A) in three avian species in vitro. Primary cultures of chicken (Gallus gallus domesticus), ring-necked pheasant (Phasianus colchicus) and Japanese quail (Corturnix japonica) embryo hepatocytes were used to compare the potencies of reagent-grade (RG-HCB), HCB-P and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as inducers of ethoxyresorufin O-deethylase (EROD) activity, CYP1A4 messenger ribonucleic acid (mRNA) and CYP1A5 mRNA. The potencies of two mono-ortho substituted PCBs, 2,3,3’,4,4’-pentachlorobiphenyl (PCB 105) and 2,3’,4,4’,5-pentachlorobiphenyl (PCB 118) were also assessed in chicken embryo hepatocytes using the same endpoints. All compounds induced EROD activity and up-regulated CYP1A4/5 mRNAs in the hepatocytes of each species. The potency of HCB relative to the potency of TCDD (ReP) was 0.0001, 0.001 and 0.01 in chicken, ring-necked pheasant and Japanese quail embryo hepatocytes, respectively. ECthreshold values were suggested to be more appropriate than EC50 values because ECthreshold values account for differences in maximal EROD and CYP1A4/5 mRNA levels that are observed with HCB exposure in avian embryo hepatocytes more so than EC50 values. Differences in species sensitivity to HCB were also assessed, and did not vary as greatly as the listed ReP values. The results presented herein suggest that HCB is capable of inducing effects downstream of activation of the aryl hydrocarbon receptor, and may warrant its inclusion in the World Health Organization’s toxic equivalency concept.
4

Kinetics and mechanisms of methoxide substitution and electroreduction of hexachlorobenzene /

Sidhu, Jeswant K. January 2000 (has links)
Thesis (Ph.D.)--University of Western Sydney, Macarthur, [Faculty of Informatics, Science and Technology], 2000. / Bibliography: p. 171-172.
5

Cytochrome P4501A Induction by Highly Purified Hexachlorobenzene in Primary Cultures of Avian Hepatocytes

Mundy, Lukas January 2011 (has links)
Hexachlorobenzene (HCB) is a persistent organic pollutant that was primarily produced for use as a fungicide dating back to the 1940s. Worldwide emissions have declined steadily over the past forty years, but HCB is still produced as a by-product of a number of industrial processes and is still detected in remote locations around the globe. Many studies have been conducted to determine the toxic and biochemical effects of HCB, but it has been suggested that reported toxic and biochemical effects initially attributed to HCB exposure may have actually been elicited by contamination of HCB by polychlororinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs). This thesis investigates whether highly purified HCB (HCB-P; defined as HCB containing < 0.2 ppb of any PCDD, PCDF, or co-planar PCB congener [the detection limit of current analytical methods]) can induce cytochrome P4501A (CYP1A) in three avian species in vitro. Primary cultures of chicken (Gallus gallus domesticus), ring-necked pheasant (Phasianus colchicus) and Japanese quail (Corturnix japonica) embryo hepatocytes were used to compare the potencies of reagent-grade (RG-HCB), HCB-P and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as inducers of ethoxyresorufin O-deethylase (EROD) activity, CYP1A4 messenger ribonucleic acid (mRNA) and CYP1A5 mRNA. The potencies of two mono-ortho substituted PCBs, 2,3,3’,4,4’-pentachlorobiphenyl (PCB 105) and 2,3’,4,4’,5-pentachlorobiphenyl (PCB 118) were also assessed in chicken embryo hepatocytes using the same endpoints. All compounds induced EROD activity and up-regulated CYP1A4/5 mRNAs in the hepatocytes of each species. The potency of HCB relative to the potency of TCDD (ReP) was 0.0001, 0.001 and 0.01 in chicken, ring-necked pheasant and Japanese quail embryo hepatocytes, respectively. ECthreshold values were suggested to be more appropriate than EC50 values because ECthreshold values account for differences in maximal EROD and CYP1A4/5 mRNA levels that are observed with HCB exposure in avian embryo hepatocytes more so than EC50 values. Differences in species sensitivity to HCB were also assessed, and did not vary as greatly as the listed ReP values. The results presented herein suggest that HCB is capable of inducing effects downstream of activation of the aryl hydrocarbon receptor, and may warrant its inclusion in the World Health Organization’s toxic equivalency concept.
6

Polychlorinated Biphenyls and Hexachlorobenzene in SurficialSediments of Kao-Ping Chi Estuary and Nearby Coastal Areas

Yang, Yi-Ning 24 August 2004 (has links)
Persistent Organic Pollutants (POPs), such as Polychlorinated Biphenyls (PCBs) or Hexachlorobenzene (HCB), released into water system. They will adsorb to particles, and incorporate into sediments. Thus the concentrations of PCBs and HCB in surface sediments provide information on recent contaminations. Besides, organisms in marine environment are influenced by the concentration in sediments, and so as the food chain. This study investigated the concentrations and characteristics of PCBs and HCB in surficial sediments of Kao-Ping Chi Estuary and nearby areas. The concentrations of PCBs and HCB in sediments were ranged from 1.432 to 6.681 (ng/g dry wt), and from 0.151 to 8.109 (ng/g dry wt¡^¡Awith an average of 3.219 and 1.978, respectively. Both of PCBs and HCB did not exceed the concentrations suggested by several sediment quality guidelines (SQGs). Compared with studies in other countries, the sediments in Kao-Ping coastal areas were more polluted by HCB. Neither PCBs nor HCB could correlate well with mean particle size or total organic carbon (TOC). The Toxic equivalents (TEQ) of dioxin-like PCBs and HCB were ranged from 0.014 to 0.061 pg-TEQ/g, and from 0.015 to 0.811 pg-TEQ/g, respectively. Using Principal Component Analysis, four possible principal components were found. These four principal components could account for 89.29% of the total variance. The first principal component was composed of highly chlorinated PCBs. The second principal component was composed of particle mean size and TOC. And the third and the fourth principal component were composed of di-, tri- PCBs and HCB. According to the factor score plot, the sample stations in this study could be divided into four groups. The first group was the stations that near the shore. The second group which contained stations were 4Km offshore. The third group contained stations with highly chlorinated PCBs. And the fourth group only contained one stations, D16. It was possible that there were other sources influenced station D16. In conclusion, the pollution in the surficial sediments was influenced by the distances from the pollutant sources and the particle size affected by tidal effect.
7

Investigation of the potential for microbial reductive dechlorination of hexachlorobenzene under iron-reducing conditions

Doikos, Pavlos E. 12 1900 (has links)
No description available.
8

The toxic effects of the pesticide lindane on the early developmental stages of the fathead minnow

Tatis, Anabel G. 25 April 2009 (has links)
Toxic effects of the pesticide Lindane on the eggs, yolksac fry and larvae of the fathead minnow (Pimephales promelas) were investigated over 14 days at 25 and 18°C. The general objective was to understand the effects of the pesticide on the early life stages of the fish, and to evaluate the suitability of these stages as indicators of contaminated environments. Egg, yolk-sac and larval stages that had been exposed to 300, 120, 90, 60, 30, 10, 5, and 0 μg/L of Lindane at 25°C exhibited a 14d-LC₅₀ of 44 μg/L. Similarly, the same stages exposed to 300, 120, 90, 60, 30, 10, and 0 μg/L of Lindane at 18°C exhibited a 14d-LC₅₀ of 37 μg/L. Lower temperature thus seemed to increase the susceptibility of the fish to the pesticide. Mortality data were also used to determine the sensitivity of the early developmental stages of fish to the pesticide. At 25°C, the larval stage was the most sensitive stage. At 18°C, on the other hand, the most sensitive stage was the yolk-sac. Results obtained from experiments in which Lindane doses were applied at different intervals within the 14d-period supported these observations. Low temperatures had a marked effect on the sensitivity of the fathead minnow to Lindane. Embryos exposed to Lindane at 18°C showed different temporal distribution of mortality than those at 25°C. A delay in hatching and emergence of smaller larvae were also noted at 18°C. Lordoscoliosis, edemas and hemorrhages were the most common morphological changes induced by the pesticide during the larval stage. The frequency of these abnormalities was linearly related to doses of Lindane. Impaired swimming behavior was also noted, but it was not related to dosages. / Master of Science
9

"Alteração de características do solo para remoção de hexaclorobenzeno de área contaminada". / Changes in soil properties to hexachlorobenzene removal from contaminated area

Nakagawa, Lia Emi 18 September 2003 (has links)
A contaminação ambiental provocada pelo despejo de resíduos industriais e pela aplicação de agrotóxicos pode resultar no desequilíbrio dos ecossistemas, além de causar danos diretos à saúde humana. No Brasil, existem várias áreas contaminadas com resíduos industriais, tais como o hexaclorobenzeno (HCB), um composto organoclorado usado no passado como fungicida, mas que atualmente tem seu uso proibido devido a sua alta persistência no ambiente e alta capacidade de bioacumulação. Este estudo verificou a possibilidade de remoção de resíduos de HCB do solo contaminado além da possibilidade de contaminação do ar e da água por este composto. Verificou-se: a) o efeito de adição de matéria orgânica, alteração de pH e alagamento da terra sobre a comunidade microbiana e a degradação do HCB; b) a volatilização do HCB e, c) a lixiviação deste composto. A contaminação inicial da terra foi determinada através de extração das amostras de terra contaminada e análise dos extratos por cromatografia gasosa (CG). Alterações das características da terra foram promovidas pela adição de matéria orgânica (bagaço de cana de açúcar ou vermicomposto), adição de Cal ou alagamento das amostras de terra contaminada, além de combinações destes tratamentos. Cada amostra de terra, colocada em frascos de vidro, recebeu uma solução de HCB radiomarcado (14C-HCB). A mineralização do 14C-HCB foi analisada através da captura do CO2 proveniente das amostras de terra por uma solução de hidróxido de potássio e quantificação do 14CO2 por Espectrometria de Cintilação Líquida (ECL). A volatilização do 14C-HCB foi analisada através da captura dos compostos voláteis por lâmina de poliuretano, extração desta lâmina e análise do extrato por ECL, para quantificação dos 14C-compostos voláteis, e por CG, para quantificação dos compostos voláteis (HCB e metabólitos). A formação de 14C-resíduos ligados e de metabólitos do HCB nas amostras de terra foi analisada através da extração destas amostras e posterior análise da terra extraída por ECL e do extrato por CG. Cada amostra de terra também foi analisada quanto à atividade microbiana, medida através da respiração dos microrganismos, e quanto a densidade microbiana, através da metodologia de contagem de unidades formadoras de colônias (UFC) de bactérias e fungos. A mobilidade e a lixiviação do HCB foram estudadas através de percolação de água em tubos de PVC contendo amostras de terra contaminada tratadas com bagaço de cana de açúcar e/ou cal e solução de 14C-HCB, dispostas sobre amostras de terra não contaminada; os tubos foram seccionados e a terra e a água lixiviada foram analisadas por ECL. O período dos estudos foi de 270 dias. A determinação da contaminação inicial da terra indicou a presença do HCB (3400 mg g-1 terra) e dos metabólitos 1,2,4,5 TCB (24 mg g-1 terra), 1,2,3,4 TCB (6 mg g-1 terra) e PCB (267 mg g-1 terra). A volatilização de 14C-compostos ocorreu em todas as amostras, principalmente nas amostras alagadas e com adição de matéria orgânica (29% a 40 %, após 270 dias). O alagamento favoreceu a volatilização provavelmente devido a baixa hidrossolubilidade do HCB e, a presença de matéria orgânica pode ter favorecido a formação de metabólitos mais voláteis através do estímulo à descloração redutiva, que ocorre sob condições de anaerobiose. Entretanto, a descloração redutiva não foi comprovada pois não houve formação nem aumento na concentração de metabólitos do HCB entre os compostos volatilizados. Houve uma diminuição na quantidade de 14C-compostos extraíveis no decorrer do tempo em todas as amostras, mas a concentração de HCB ou de seus metabólitos permaneceu constante independente do tratamento. A atividade e a densidade microbiana foram maiores nas amostras com bagaço de cana de açúcar mas não tiveram efeito sobre a volatilização ou a degradação do HCB. Não ocorreu mineralização ou mobilidade do 14C-HCB na terra contaminada e nem a formação de 14C-resíduos ligados. Portanto, a adição de matéria orgânica, a alteração de pH e o alagamento da terra não se mostraram eficientes para a remoção do HCB de terra contaminada. Além disso, a ocorrência de formação de 14C-compostos voláteis e a ausência de lixiviação do 14C-HCB indicaram que a presença de resíduos de HCB no solo pode levar à contaminação do ar mas não de água subterrânea. / The environmental contamination by industrial wastes and pesticides can cause harmful effects to ecosystem besides direct human health damages. In Brasil, there are several areas contaminated with industrial wastes like the hexachlorobenzene (HCB), a chlorinated organic compound used in the past as fungicide but that has no longer been produced due to its high persistence in the environment and bioaccumulation potential. This study verified the possibility of HCB residues removal from contaminated soil besides the air and water contamination risk. It was verified: a) the effect of organic matter addition, pH change and flooding of the contaminated soil on the microbial community and HCB degradation; b) HCB volatilization and, c) HCB leaching. The initial soil contamination was determined by extraction of contaminated soil samples and analysis of the extract by Gaseous Chromatography (GC). Soil properties changes were promoted by organic material addition (sugar cane bagasse or earthworm humus), lime addition and flooding of the soil samples besides a combination of these treatments. Each soil sample, placed in glass flasks, was treated with radiolabelled HCB solution (14C-HCB). The 14C-HCB mineralization was analyzed by the entrapment of CO2 originated from the soil samples by potassium hydroxide solution and quantification of the 14CO2 by Liquid Scintillation Spectrometry (LSS). The 14C-HCB volatilization was analyzed by the entrapment of the volatiles compounds by a polyurethane lamina, extraction of this lamina and analysis of the extract by LSS, for 14C-volatile compounds quantification, and by GC, for volatile compounds (HCB and metabolites) quantification. The 14C-bound residues and the HCB metabolites of the soil samples were analyzed by the extraction of these samples and further analysis of the extracted soil by LSS and analysis of the extract by GC. Each soil sample was analyzed with regard to its microbial activity by microbial respiration measure and microbial density by the plate count technique. The mobility and leaching of the HCB were studied by water percolation through PVC tubes containing contaminated soil treated with sugar cane bagasse and/or lime and 14C-HCB placed over no contaminated soil; the tubes were cut in sections and the soil and the leached water were analyzed by LSS. All these studies lasted 270 days. The initial soil contamination determination indicated the presence of the HCB (3400 mg g-1 soil) and the metabolites 1,2,4,5 TCB (24 mg g-1 soil), 1,2,3,4 TCB (6 mg g-1 soil) and PCB (267 mg g-1 soil). The volatilization of the 14C-compounds occurred in all the samples, mainly in the flooded samples with organic matter addition (29% to 40% after 270 days). The flooding enhanced the volatilization due the low HCB water-solubility and, the presence of organic material can have favoured the formation of metabolites more volatile than the HCB due to reductive dechlorination that occurs under anaerobic conditions. But the reductive dechlorination occurrence was not proved as there was no formation or increase in metabolite concentration. There was a decrease in 14C-extractable compounds quantity through the time in all the samples but the HCB and metabolites concentrations keep constant independently of the treatment. The microbial activity and density were higher in the samples with sugar cane bagasse but it did not affected the HCB volatilization or degradation. The 14C-HCB mineralization and the 14C-bound residues formation did not occur. The mobility of the 14C-HCB was not observed too. Therefore, the organic material addition, the pH change and the soil flooding were not efficient to HCB removal from the contaminated soil. And, the occurrence of the volatilization of 14C-compounds and the absence of 14C-HCB leaching indicated that the presence of HCB residues in the soil can result in contamination of air but not the ground water.
10

"Alteração de características do solo para remoção de hexaclorobenzeno de área contaminada". / Changes in soil properties to hexachlorobenzene removal from contaminated area

Lia Emi Nakagawa 18 September 2003 (has links)
A contaminação ambiental provocada pelo despejo de resíduos industriais e pela aplicação de agrotóxicos pode resultar no desequilíbrio dos ecossistemas, além de causar danos diretos à saúde humana. No Brasil, existem várias áreas contaminadas com resíduos industriais, tais como o hexaclorobenzeno (HCB), um composto organoclorado usado no passado como fungicida, mas que atualmente tem seu uso proibido devido a sua alta persistência no ambiente e alta capacidade de bioacumulação. Este estudo verificou a possibilidade de remoção de resíduos de HCB do solo contaminado além da possibilidade de contaminação do ar e da água por este composto. Verificou-se: a) o efeito de adição de matéria orgânica, alteração de pH e alagamento da terra sobre a comunidade microbiana e a degradação do HCB; b) a volatilização do HCB e, c) a lixiviação deste composto. A contaminação inicial da terra foi determinada através de extração das amostras de terra contaminada e análise dos extratos por cromatografia gasosa (CG). Alterações das características da terra foram promovidas pela adição de matéria orgânica (bagaço de cana de açúcar ou vermicomposto), adição de Cal ou alagamento das amostras de terra contaminada, além de combinações destes tratamentos. Cada amostra de terra, colocada em frascos de vidro, recebeu uma solução de HCB radiomarcado (14C-HCB). A mineralização do 14C-HCB foi analisada através da captura do CO2 proveniente das amostras de terra por uma solução de hidróxido de potássio e quantificação do 14CO2 por Espectrometria de Cintilação Líquida (ECL). A volatilização do 14C-HCB foi analisada através da captura dos compostos voláteis por lâmina de poliuretano, extração desta lâmina e análise do extrato por ECL, para quantificação dos 14C-compostos voláteis, e por CG, para quantificação dos compostos voláteis (HCB e metabólitos). A formação de 14C-resíduos ligados e de metabólitos do HCB nas amostras de terra foi analisada através da extração destas amostras e posterior análise da terra extraída por ECL e do extrato por CG. Cada amostra de terra também foi analisada quanto à atividade microbiana, medida através da respiração dos microrganismos, e quanto a densidade microbiana, através da metodologia de contagem de unidades formadoras de colônias (UFC) de bactérias e fungos. A mobilidade e a lixiviação do HCB foram estudadas através de percolação de água em tubos de PVC contendo amostras de terra contaminada tratadas com bagaço de cana de açúcar e/ou cal e solução de 14C-HCB, dispostas sobre amostras de terra não contaminada; os tubos foram seccionados e a terra e a água lixiviada foram analisadas por ECL. O período dos estudos foi de 270 dias. A determinação da contaminação inicial da terra indicou a presença do HCB (3400 mg g-1 terra) e dos metabólitos 1,2,4,5 TCB (24 mg g-1 terra), 1,2,3,4 TCB (6 mg g-1 terra) e PCB (267 mg g-1 terra). A volatilização de 14C-compostos ocorreu em todas as amostras, principalmente nas amostras alagadas e com adição de matéria orgânica (29% a 40 %, após 270 dias). O alagamento favoreceu a volatilização provavelmente devido a baixa hidrossolubilidade do HCB e, a presença de matéria orgânica pode ter favorecido a formação de metabólitos mais voláteis através do estímulo à descloração redutiva, que ocorre sob condições de anaerobiose. Entretanto, a descloração redutiva não foi comprovada pois não houve formação nem aumento na concentração de metabólitos do HCB entre os compostos volatilizados. Houve uma diminuição na quantidade de 14C-compostos extraíveis no decorrer do tempo em todas as amostras, mas a concentração de HCB ou de seus metabólitos permaneceu constante independente do tratamento. A atividade e a densidade microbiana foram maiores nas amostras com bagaço de cana de açúcar mas não tiveram efeito sobre a volatilização ou a degradação do HCB. Não ocorreu mineralização ou mobilidade do 14C-HCB na terra contaminada e nem a formação de 14C-resíduos ligados. Portanto, a adição de matéria orgânica, a alteração de pH e o alagamento da terra não se mostraram eficientes para a remoção do HCB de terra contaminada. Além disso, a ocorrência de formação de 14C-compostos voláteis e a ausência de lixiviação do 14C-HCB indicaram que a presença de resíduos de HCB no solo pode levar à contaminação do ar mas não de água subterrânea. / The environmental contamination by industrial wastes and pesticides can cause harmful effects to ecosystem besides direct human health damages. In Brasil, there are several areas contaminated with industrial wastes like the hexachlorobenzene (HCB), a chlorinated organic compound used in the past as fungicide but that has no longer been produced due to its high persistence in the environment and bioaccumulation potential. This study verified the possibility of HCB residues removal from contaminated soil besides the air and water contamination risk. It was verified: a) the effect of organic matter addition, pH change and flooding of the contaminated soil on the microbial community and HCB degradation; b) HCB volatilization and, c) HCB leaching. The initial soil contamination was determined by extraction of contaminated soil samples and analysis of the extract by Gaseous Chromatography (GC). Soil properties changes were promoted by organic material addition (sugar cane bagasse or earthworm humus), lime addition and flooding of the soil samples besides a combination of these treatments. Each soil sample, placed in glass flasks, was treated with radiolabelled HCB solution (14C-HCB). The 14C-HCB mineralization was analyzed by the entrapment of CO2 originated from the soil samples by potassium hydroxide solution and quantification of the 14CO2 by Liquid Scintillation Spectrometry (LSS). The 14C-HCB volatilization was analyzed by the entrapment of the volatiles compounds by a polyurethane lamina, extraction of this lamina and analysis of the extract by LSS, for 14C-volatile compounds quantification, and by GC, for volatile compounds (HCB and metabolites) quantification. The 14C-bound residues and the HCB metabolites of the soil samples were analyzed by the extraction of these samples and further analysis of the extracted soil by LSS and analysis of the extract by GC. Each soil sample was analyzed with regard to its microbial activity by microbial respiration measure and microbial density by the plate count technique. The mobility and leaching of the HCB were studied by water percolation through PVC tubes containing contaminated soil treated with sugar cane bagasse and/or lime and 14C-HCB placed over no contaminated soil; the tubes were cut in sections and the soil and the leached water were analyzed by LSS. All these studies lasted 270 days. The initial soil contamination determination indicated the presence of the HCB (3400 mg g-1 soil) and the metabolites 1,2,4,5 TCB (24 mg g-1 soil), 1,2,3,4 TCB (6 mg g-1 soil) and PCB (267 mg g-1 soil). The volatilization of the 14C-compounds occurred in all the samples, mainly in the flooded samples with organic matter addition (29% to 40% after 270 days). The flooding enhanced the volatilization due the low HCB water-solubility and, the presence of organic material can have favoured the formation of metabolites more volatile than the HCB due to reductive dechlorination that occurs under anaerobic conditions. But the reductive dechlorination occurrence was not proved as there was no formation or increase in metabolite concentration. There was a decrease in 14C-extractable compounds quantity through the time in all the samples but the HCB and metabolites concentrations keep constant independently of the treatment. The microbial activity and density were higher in the samples with sugar cane bagasse but it did not affected the HCB volatilization or degradation. The 14C-HCB mineralization and the 14C-bound residues formation did not occur. The mobility of the 14C-HCB was not observed too. Therefore, the organic material addition, the pH change and the soil flooding were not efficient to HCB removal from the contaminated soil. And, the occurrence of the volatilization of 14C-compounds and the absence of 14C-HCB leaching indicated that the presence of HCB residues in the soil can result in contamination of air but not the ground water.

Page generated in 0.0337 seconds