Kirk Dean - Academia.edu (original) (raw)

Papers by Kirk Dean

Research paper thumbnail of Role of mobile colloids in the transport of chemical pollutants in groundwaters

Research paper thumbnail of TMDL DEVELOPMENT FOR WATER QUALITY IMPAIRMENTS OF ADAMS AND COW BAYOUS

Research paper thumbnail of Particle-Mediated Transport and Fate of a Hydrophobic Organic Contaminant in Southern Lake Michigan: The Role of Major Water Column Particle Species

Journal of Great Lakes Research, 1993

Research paper thumbnail of Techniques to assess cross-border air pollution and application to a US-Mexico border region

Science of The Total Environment, 2001

A year-long assessment of cross-border air pollution was conducted in the eastmost section of the... more A year-long assessment of cross-border air pollution was conducted in the eastmost section of the US-Mexico border region, known as the Lower Rio Grande Valley, in South Texas. Measurements were conducted on the US side and included fine particle mass (PM2.5) and elemental composition, volatile organic compounds (VOCs) and meteorology. Wind sector analyses of chemical tracers and diagnostic ratios, in addition to principal component analysis (PCA), were initially applied to assess cross-border and overall air shed influences. Linear-angular correlation statistics [Biometrika, 63, (1976), 403–405] and nonparametric multiple comparisons between wind sectors were computed with the particle element data using principal component scores from PCA to determine the direction of source classes. Findings suggest crustal particles and salts carried or stirred by sea breeze winds from a southerly and southeasterly direction from the Gulf of Mexico heavily influenced the elemental composition of the particulate samples. Pair-wise comparisons of wind directions for the principal component scores suggest possible oil combustion influences from utilities or boilers coming from the south and possible coal combustion influences from the north and northwest. The techniques discussed can provide a methodology to assess future ambient levels and cross-border influences in the Valley as conditions change.

Research paper thumbnail of Interaction of quicklime with polychlorobiphenyl-contaminated solids

Environmental Science & Technology, 1991

Research paper thumbnail of Particle-Mediated Transport and Fate of a Hydrophobic Organic Contaminant in Southern Lake Michigan: The Role of Major Water Column Particle Species

Journal of Great Lakes Research, 1993

Research paper thumbnail of Interaction of quicklime with polychlorobiphenyl-contaminated solids

Environmental Science & Technology, 1991

Research paper thumbnail of Use of Bacterial Source Tracking in Support of TMDL Implementation Plan at Middle Rio Grande Watershed

Proceedings of the Water Environment Federation, 2003

Research paper thumbnail of Site-Specific Water Quality Targets for Fish Contaminants: Application of Sediment, Water, and Tissue Targets based on Measured Partitioning Relationships

Proceedings of the Water Environment Federation, 2003

Research paper thumbnail of Development of a Dioxin TMDL for the Houston Ship Channel in Texas

Proceedings of the Water Environment Federation, 2006

Page 1. DEVELOPMENT OF A DIOXIN TMDL FOR THE HOUSTON SHIP CHANNEL IN TEXAS Hanadi S. Rifai†, Moni... more Page 1. DEVELOPMENT OF A DIOXIN TMDL FOR THE HOUSTON SHIP CHANNEL IN TEXAS Hanadi S. Rifai†, Monica P. Suarez, Randy Palachek, Kirk Dean, Paul Jensen, Michael Bloom and Larry Koenig †University of Houston 4800 Calhoun Rd. Houston, TX 77204-4003 ...

Research paper thumbnail of TOOLS TO ASSIST IDENTIFICATION AND QUANTIFICATION OF INDICATOR BACTERIAL SOURCES

Proceedings of the Water Environment Federation, 2005

Research paper thumbnail of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in Houston Ship Channel Tissue and Sediment

Environmental Engineering Science, 2005

ABSTRACT This review represents an assessment of the pollution status of polychlorinated dibenzo-... more ABSTRACT This review represents an assessment of the pollution status of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in China (the mainland, Hong Kong and Taiwan). During the past decades, seven PCDD/Fs pollution hotspots have been found: (a). Ya-er Lake, Hubei Province, with 'total PCDD/Fs' level reaching 177,427 pg g(-1) (dry weight) in lake sediments; (b). Chinese Schistosomiasis affected areas of Jiangxi Province with 33,660 pg g(-1) in soil; (c). e-waste recycling area of Yangtze River Delta, with 2726 pg g(-1) in paddy soil; (d). e-waste recycling area of Guiyu (eastern part of Guangdong Province), with 967,500 pg g(-1) in mixture of burnt residue and soil (the highest level among all hotspots); (e). Pearl River Delta with 2630 pg g(-1) in coastal sediment. (f). Kwun Tong, Victoria Harbour, Hong Kong with 10,999 pg g(-1) in coastal sediment; and (g). southern Taiwan with 606,000 pg g(-1) in soil near the vicinity of a pentachlorophenol manufacturing factory. The main sources of PCDD/Fs in China were formed from impurities during the production of polychlorophenol, hexachlorobenzene, polychlorinated biphenyls, organic chlorinated pesticide and triclosan. In addition, sources of PCDD/Fs included municipal waste incineration, mineral fuel usage, open burning of electronic waste and crop residues, industrial waste discharge and vehicle exhaust emission. Due to potential human health risks from long-term exposure to PCDD/Fs at these hotspots, body loadings of these contaminants should be monitored.

Research paper thumbnail of DEVELOPMENT OF A SEDIMENT-WATER MODEL FOR DIOXIN IN THE HOUSTON SHIP CHANNEL, TEXAS

Proceedings of the Water Environment Federation, 2007

Page 1. DEVELOPMENT OF A SEDIMENT-WATER MODEL FOR DIOXIN IN THE HOUSTON SHIP CHANNEL, TEXAS Monic... more Page 1. DEVELOPMENT OF A SEDIMENT-WATER MODEL FOR DIOXIN IN THE HOUSTON SHIP CHANNEL, TEXAS Monica P. Suarez†, Kirk Dean†, Jim Patek†, Randy Palachek†, Hanadi Rifai‡, Andrea Izquierdo‡ and Larry ...

Research paper thumbnail of Direct comparison of four bacterial source tracking methods and use of composite data sets

Journal of Applied Microbiology, 2007

Four bacterial source tracking (BST) methods, enterobacterial repetitive intergenic consensus pol... more Four bacterial source tracking (BST) methods, enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR), automated ribotyping using HindIII, Kirby-Bauer antibiotic resistance analysis (KB-ARA), and pulsed field gel electrophoresis (PFGE) were directly compared using the same collection of Escherichia coli isolates. The data sets from each BST method and from composite methods were compared for library accuracy and their ability to identify water isolates.

Research paper thumbnail of Distribution of polychlorinated dibenzo- p-dioxins and dibenzofurans in suspended sediments, dissolved phase and bottom sediment in the Houston Ship Channel

Chemosphere, 2006

Spatial distributions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in t... more Spatial distributions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in the water column and bottom sediments of the Houston Ship Channel in Texas were measured three times over a 1-year period. Total TEQ concentrations in water ranged from 0.01 to 0.25 pg/l for the dissolved phase and from 0.09 to 2.91 pg/l for the suspended phase, while TEQ concentrations in bottom sediments varied from 0.9 to 139.8 ng/kg dry wt. The dissolved concentrations were lower than their respective suspended concentrations, with average dissolved/suspended ratios between 0.11 and 0.59 for individual congeners. More than 89% of the total concentration of 2378-substituted PCDD/PCDFs was attributable to OCDD but 2378-TCDD was the major contributor to total TEQ for the three sampled media. Average logs of organic carbon-normalized suspended sediment-dissolved partitioning coefficients ðlog K obs oc Þ varied between 4.92 and 8.59 l/kg-oc; while in the bottom sediment-dissolved interface, log K obs oc values ranged from 5.48 to 8.48 l/kg-oc. Observed log K oc values varied within a factor of 0.64-1.26 from equilibrium log K oc values, suggesting fluxes of PCDD/PCDFs across the interfaces. It was found that in the HSC, on average, the tendency of a compound to move from the particulate phase to the dissolved phase decreases with increasing K ow .

Research paper thumbnail of Septic tank and agricultural non-point source pollution within a rural watershed

Toxicological & Environmental Chemistry, 1990

This investigation addresses the problem of Non‐Point Source (NPS) pollution in the rural Lake We... more This investigation addresses the problem of Non‐Point Source (NPS) pollution in the rural Lake Weatherford watershed in Parker County, Texas. This reservoir is the primary municipal water supply for the City of Weatherford, Texas. The principal method of ...

Research paper thumbnail of DEVELOPMENT OF FRESHWATER WATER-QUALITY CRITERIA FOR PERCHLORATE

Environmental Toxicology and Chemistry, 2004

The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for ro... more The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for rockets and missiles; in explosives, flares, fireworks, chemical processes, and automobile air-bag inflators; and for other assorted uses. With recent advances in analytical detection capability, perchlorate has been found in a variety of ground and surface waters throughout the United States. Because perchlorate has been associated with thyroid problems in humans and may have similar effects on wildlife, it is desirable to develop a water-quality criterion to assist in identifying concentrations of perchlorate in water likely to pose an ecological health risk. In the present study, we compiled all available data regarding the effects of perchlorate to aquatic organisms, and we performed additional toxicity and bioconcentration tests as required by the U.S. Environmental Protection Agency (U.S. EPA) for the development of water-quality criteria for aquatic life. A criterion maximum concentration of 20 mg/L and a criterion continuous concentration of 9.3 mg/L were calculated based on the test results. Although these are not formal Clean Water Act Section 304(a) criteria, which must be published by the U.S. EPA, these criteria may be useful in the determination of remedial action levels for contaminated sites, for National Pollutant Discharge Elimination System permit limits, and other water-quality management practices.

Research paper thumbnail of BIOACCUMULATION OF POLYCHLORINATED DIBENZODIOXINS AND DIBENZOFURANS IN CATFISH AND CRABS ALONG AN ESTUARINE SALINITY AND CONTAMINATION GRADIENT

Environmental Toxicology and Chemistry, 2009

Elevated but variable levels of polychlorinated dibenzodioxins and polychlorinated dibenzofurans ... more Elevated but variable levels of polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDD/Fs) were observed in hardhead sea catfish (HH) and blue crabs (BCs), as well as in water and sediment, of the Houston Ship Channel system, Texas, USA. It is hypothesized that the variation was caused by the spatial variability of PCDD/F contamination, together with the natural mobility of organisms in satisfying prey, temperature, salinity, and reproductive requirements. Structural equation modeling was applied to explore the congener-specific relationships between PCDD/F levels in HH and BC tissues and independent predictors such as PCDD/F contamination levels, environmental factors such as salinity and temperature, temporal-spatial factors such as site depth and season, and biological factors such as length, weight, and lipid content. Contamination levels in both sediment and water were statistically significant predictors of the levels of less chlorinated congeners in both HH and BCs, with the standardized regression weight for sediment concentration roughly twice that for the water concentration. This implies that sediments are the dominant route for PCDD/F exposure and remediation efforts should focus on legacy sediment contamination. Tissue lipid content was a significant predictor of tissue concentrations in HH but only to a lesser extent in BCs, perhaps due to their low lipid content. Site depth and seasonal factors also were significant predictors of tissue concentrations. For the highly chlorinated congeners, only a small fraction of the variance in tissue concentrations was explained by the independent predictors, possibly indicating that uptake and elimination kinetics, biotransformation processes, or both may be more important factors controlling the bioaccumulation of those congeners.

Research paper thumbnail of DEVELOPMENT OF FRESHWATER WATER-QUALITY CRITERIA FOR PERCHLORATE

Environmental Toxicology and Chemistry, 2004

The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for ro... more The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for rockets and missiles; in explosives, flares, fireworks, chemical processes, and automobile air-bag inflators; and for other assorted uses. With recent advances in analytical detection capability, perchlorate has been found in a variety of ground and surface waters throughout the United States. Because perchlorate has been associated with thyroid problems in humans and may have similar effects on wildlife, it is desirable to develop a water-quality criterion to assist in identifying concentrations of perchlorate in water likely to pose an ecological health risk. In the present study, we compiled all available data regarding the effects of perchlorate to aquatic organisms, and we performed additional toxicity and bioconcentration tests as required by the U.S. Environmental Protection Agency (U.S. EPA) for the development of water-quality criteria for aquatic life. A criterion maximum concentration of 20 mg/L and a criterion continuous concentration of 9.3 mg/L were calculated based on the test results. Although these are not formal Clean Water Act Section 304(a) criteria, which must be published by the U.S. EPA, these criteria may be useful in the determination of remedial action levels for contaminated sites, for National Pollutant Discharge Elimination System permit limits, and other water-quality management practices.

Research paper thumbnail of Polychlorinated Dibenzo- p -dioxins and Dibenzofurans in Houston Ship Channel Tissue and Sediment

Environmental Engineering Science, 2005

Page 1. ENVIRONMENTAL ENGINEERING SCIENCE Volume 22, Number 6, 2005 © Mary Ann Liebert, Inc. Poly... more Page 1. ENVIRONMENTAL ENGINEERING SCIENCE Volume 22, Number 6, 2005 © Mary Ann Liebert, Inc. Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in Houston Ship Channel Tissue and Sediment Monica P. Suarez ...

Research paper thumbnail of Role of mobile colloids in the transport of chemical pollutants in groundwaters

Research paper thumbnail of TMDL DEVELOPMENT FOR WATER QUALITY IMPAIRMENTS OF ADAMS AND COW BAYOUS

Research paper thumbnail of Particle-Mediated Transport and Fate of a Hydrophobic Organic Contaminant in Southern Lake Michigan: The Role of Major Water Column Particle Species

Journal of Great Lakes Research, 1993

Research paper thumbnail of Techniques to assess cross-border air pollution and application to a US-Mexico border region

Science of The Total Environment, 2001

A year-long assessment of cross-border air pollution was conducted in the eastmost section of the... more A year-long assessment of cross-border air pollution was conducted in the eastmost section of the US-Mexico border region, known as the Lower Rio Grande Valley, in South Texas. Measurements were conducted on the US side and included fine particle mass (PM2.5) and elemental composition, volatile organic compounds (VOCs) and meteorology. Wind sector analyses of chemical tracers and diagnostic ratios, in addition to principal component analysis (PCA), were initially applied to assess cross-border and overall air shed influences. Linear-angular correlation statistics [Biometrika, 63, (1976), 403–405] and nonparametric multiple comparisons between wind sectors were computed with the particle element data using principal component scores from PCA to determine the direction of source classes. Findings suggest crustal particles and salts carried or stirred by sea breeze winds from a southerly and southeasterly direction from the Gulf of Mexico heavily influenced the elemental composition of the particulate samples. Pair-wise comparisons of wind directions for the principal component scores suggest possible oil combustion influences from utilities or boilers coming from the south and possible coal combustion influences from the north and northwest. The techniques discussed can provide a methodology to assess future ambient levels and cross-border influences in the Valley as conditions change.

Research paper thumbnail of Interaction of quicklime with polychlorobiphenyl-contaminated solids

Environmental Science & Technology, 1991

Research paper thumbnail of Particle-Mediated Transport and Fate of a Hydrophobic Organic Contaminant in Southern Lake Michigan: The Role of Major Water Column Particle Species

Journal of Great Lakes Research, 1993

Research paper thumbnail of Interaction of quicklime with polychlorobiphenyl-contaminated solids

Environmental Science & Technology, 1991

Research paper thumbnail of Use of Bacterial Source Tracking in Support of TMDL Implementation Plan at Middle Rio Grande Watershed

Proceedings of the Water Environment Federation, 2003

Research paper thumbnail of Site-Specific Water Quality Targets for Fish Contaminants: Application of Sediment, Water, and Tissue Targets based on Measured Partitioning Relationships

Proceedings of the Water Environment Federation, 2003

Research paper thumbnail of Development of a Dioxin TMDL for the Houston Ship Channel in Texas

Proceedings of the Water Environment Federation, 2006

Page 1. DEVELOPMENT OF A DIOXIN TMDL FOR THE HOUSTON SHIP CHANNEL IN TEXAS Hanadi S. Rifai†, Moni... more Page 1. DEVELOPMENT OF A DIOXIN TMDL FOR THE HOUSTON SHIP CHANNEL IN TEXAS Hanadi S. Rifai†, Monica P. Suarez, Randy Palachek, Kirk Dean, Paul Jensen, Michael Bloom and Larry Koenig †University of Houston 4800 Calhoun Rd. Houston, TX 77204-4003 ...

Research paper thumbnail of TOOLS TO ASSIST IDENTIFICATION AND QUANTIFICATION OF INDICATOR BACTERIAL SOURCES

Proceedings of the Water Environment Federation, 2005

Research paper thumbnail of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in Houston Ship Channel Tissue and Sediment

Environmental Engineering Science, 2005

ABSTRACT This review represents an assessment of the pollution status of polychlorinated dibenzo-... more ABSTRACT This review represents an assessment of the pollution status of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in China (the mainland, Hong Kong and Taiwan). During the past decades, seven PCDD/Fs pollution hotspots have been found: (a). Ya-er Lake, Hubei Province, with 'total PCDD/Fs' level reaching 177,427 pg g(-1) (dry weight) in lake sediments; (b). Chinese Schistosomiasis affected areas of Jiangxi Province with 33,660 pg g(-1) in soil; (c). e-waste recycling area of Yangtze River Delta, with 2726 pg g(-1) in paddy soil; (d). e-waste recycling area of Guiyu (eastern part of Guangdong Province), with 967,500 pg g(-1) in mixture of burnt residue and soil (the highest level among all hotspots); (e). Pearl River Delta with 2630 pg g(-1) in coastal sediment. (f). Kwun Tong, Victoria Harbour, Hong Kong with 10,999 pg g(-1) in coastal sediment; and (g). southern Taiwan with 606,000 pg g(-1) in soil near the vicinity of a pentachlorophenol manufacturing factory. The main sources of PCDD/Fs in China were formed from impurities during the production of polychlorophenol, hexachlorobenzene, polychlorinated biphenyls, organic chlorinated pesticide and triclosan. In addition, sources of PCDD/Fs included municipal waste incineration, mineral fuel usage, open burning of electronic waste and crop residues, industrial waste discharge and vehicle exhaust emission. Due to potential human health risks from long-term exposure to PCDD/Fs at these hotspots, body loadings of these contaminants should be monitored.

Research paper thumbnail of DEVELOPMENT OF A SEDIMENT-WATER MODEL FOR DIOXIN IN THE HOUSTON SHIP CHANNEL, TEXAS

Proceedings of the Water Environment Federation, 2007

Page 1. DEVELOPMENT OF A SEDIMENT-WATER MODEL FOR DIOXIN IN THE HOUSTON SHIP CHANNEL, TEXAS Monic... more Page 1. DEVELOPMENT OF A SEDIMENT-WATER MODEL FOR DIOXIN IN THE HOUSTON SHIP CHANNEL, TEXAS Monica P. Suarez†, Kirk Dean†, Jim Patek†, Randy Palachek†, Hanadi Rifai‡, Andrea Izquierdo‡ and Larry ...

Research paper thumbnail of Direct comparison of four bacterial source tracking methods and use of composite data sets

Journal of Applied Microbiology, 2007

Four bacterial source tracking (BST) methods, enterobacterial repetitive intergenic consensus pol... more Four bacterial source tracking (BST) methods, enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR), automated ribotyping using HindIII, Kirby-Bauer antibiotic resistance analysis (KB-ARA), and pulsed field gel electrophoresis (PFGE) were directly compared using the same collection of Escherichia coli isolates. The data sets from each BST method and from composite methods were compared for library accuracy and their ability to identify water isolates.

Research paper thumbnail of Distribution of polychlorinated dibenzo- p-dioxins and dibenzofurans in suspended sediments, dissolved phase and bottom sediment in the Houston Ship Channel

Chemosphere, 2006

Spatial distributions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in t... more Spatial distributions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in the water column and bottom sediments of the Houston Ship Channel in Texas were measured three times over a 1-year period. Total TEQ concentrations in water ranged from 0.01 to 0.25 pg/l for the dissolved phase and from 0.09 to 2.91 pg/l for the suspended phase, while TEQ concentrations in bottom sediments varied from 0.9 to 139.8 ng/kg dry wt. The dissolved concentrations were lower than their respective suspended concentrations, with average dissolved/suspended ratios between 0.11 and 0.59 for individual congeners. More than 89% of the total concentration of 2378-substituted PCDD/PCDFs was attributable to OCDD but 2378-TCDD was the major contributor to total TEQ for the three sampled media. Average logs of organic carbon-normalized suspended sediment-dissolved partitioning coefficients ðlog K obs oc Þ varied between 4.92 and 8.59 l/kg-oc; while in the bottom sediment-dissolved interface, log K obs oc values ranged from 5.48 to 8.48 l/kg-oc. Observed log K oc values varied within a factor of 0.64-1.26 from equilibrium log K oc values, suggesting fluxes of PCDD/PCDFs across the interfaces. It was found that in the HSC, on average, the tendency of a compound to move from the particulate phase to the dissolved phase decreases with increasing K ow .

Research paper thumbnail of Septic tank and agricultural non-point source pollution within a rural watershed

Toxicological & Environmental Chemistry, 1990

This investigation addresses the problem of Non‐Point Source (NPS) pollution in the rural Lake We... more This investigation addresses the problem of Non‐Point Source (NPS) pollution in the rural Lake Weatherford watershed in Parker County, Texas. This reservoir is the primary municipal water supply for the City of Weatherford, Texas. The principal method of ...

Research paper thumbnail of DEVELOPMENT OF FRESHWATER WATER-QUALITY CRITERIA FOR PERCHLORATE

Environmental Toxicology and Chemistry, 2004

The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for ro... more The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for rockets and missiles; in explosives, flares, fireworks, chemical processes, and automobile air-bag inflators; and for other assorted uses. With recent advances in analytical detection capability, perchlorate has been found in a variety of ground and surface waters throughout the United States. Because perchlorate has been associated with thyroid problems in humans and may have similar effects on wildlife, it is desirable to develop a water-quality criterion to assist in identifying concentrations of perchlorate in water likely to pose an ecological health risk. In the present study, we compiled all available data regarding the effects of perchlorate to aquatic organisms, and we performed additional toxicity and bioconcentration tests as required by the U.S. Environmental Protection Agency (U.S. EPA) for the development of water-quality criteria for aquatic life. A criterion maximum concentration of 20 mg/L and a criterion continuous concentration of 9.3 mg/L were calculated based on the test results. Although these are not formal Clean Water Act Section 304(a) criteria, which must be published by the U.S. EPA, these criteria may be useful in the determination of remedial action levels for contaminated sites, for National Pollutant Discharge Elimination System permit limits, and other water-quality management practices.

Research paper thumbnail of BIOACCUMULATION OF POLYCHLORINATED DIBENZODIOXINS AND DIBENZOFURANS IN CATFISH AND CRABS ALONG AN ESTUARINE SALINITY AND CONTAMINATION GRADIENT

Environmental Toxicology and Chemistry, 2009

Elevated but variable levels of polychlorinated dibenzodioxins and polychlorinated dibenzofurans ... more Elevated but variable levels of polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDD/Fs) were observed in hardhead sea catfish (HH) and blue crabs (BCs), as well as in water and sediment, of the Houston Ship Channel system, Texas, USA. It is hypothesized that the variation was caused by the spatial variability of PCDD/F contamination, together with the natural mobility of organisms in satisfying prey, temperature, salinity, and reproductive requirements. Structural equation modeling was applied to explore the congener-specific relationships between PCDD/F levels in HH and BC tissues and independent predictors such as PCDD/F contamination levels, environmental factors such as salinity and temperature, temporal-spatial factors such as site depth and season, and biological factors such as length, weight, and lipid content. Contamination levels in both sediment and water were statistically significant predictors of the levels of less chlorinated congeners in both HH and BCs, with the standardized regression weight for sediment concentration roughly twice that for the water concentration. This implies that sediments are the dominant route for PCDD/F exposure and remediation efforts should focus on legacy sediment contamination. Tissue lipid content was a significant predictor of tissue concentrations in HH but only to a lesser extent in BCs, perhaps due to their low lipid content. Site depth and seasonal factors also were significant predictors of tissue concentrations. For the highly chlorinated congeners, only a small fraction of the variance in tissue concentrations was explained by the independent predictors, possibly indicating that uptake and elimination kinetics, biotransformation processes, or both may be more important factors controlling the bioaccumulation of those congeners.

Research paper thumbnail of DEVELOPMENT OF FRESHWATER WATER-QUALITY CRITERIA FOR PERCHLORATE

Environmental Toxicology and Chemistry, 2004

The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for ro... more The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for rockets and missiles; in explosives, flares, fireworks, chemical processes, and automobile air-bag inflators; and for other assorted uses. With recent advances in analytical detection capability, perchlorate has been found in a variety of ground and surface waters throughout the United States. Because perchlorate has been associated with thyroid problems in humans and may have similar effects on wildlife, it is desirable to develop a water-quality criterion to assist in identifying concentrations of perchlorate in water likely to pose an ecological health risk. In the present study, we compiled all available data regarding the effects of perchlorate to aquatic organisms, and we performed additional toxicity and bioconcentration tests as required by the U.S. Environmental Protection Agency (U.S. EPA) for the development of water-quality criteria for aquatic life. A criterion maximum concentration of 20 mg/L and a criterion continuous concentration of 9.3 mg/L were calculated based on the test results. Although these are not formal Clean Water Act Section 304(a) criteria, which must be published by the U.S. EPA, these criteria may be useful in the determination of remedial action levels for contaminated sites, for National Pollutant Discharge Elimination System permit limits, and other water-quality management practices.

Research paper thumbnail of Polychlorinated Dibenzo- p -dioxins and Dibenzofurans in Houston Ship Channel Tissue and Sediment

Environmental Engineering Science, 2005

Page 1. ENVIRONMENTAL ENGINEERING SCIENCE Volume 22, Number 6, 2005 © Mary Ann Liebert, Inc. Poly... more Page 1. ENVIRONMENTAL ENGINEERING SCIENCE Volume 22, Number 6, 2005 © Mary Ann Liebert, Inc. Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in Houston Ship Channel Tissue and Sediment Monica P. Suarez ...