International Journal of Environmental Research and Public Health
Safe drinking water remains a major global challenge, especially in rural areas where, according ... more Safe drinking water remains a major global challenge, especially in rural areas where, according to UNICEF, 80% of those without access to improved water systems reside. While water, sanitation, and hygiene (WASH)-related diseases and deaths are common outcomes of unsafe water, there is also an economic burden associated with unsafe water. These burdens are most prominent in rural areas in less-developed nations. Slow sand filters (SSFs), or biological sand filters (BSFs), are ideal water treatment solutions for these low-resource regions. SSFs are the oldest municipal drinking water treatment systems and improve water quality by removing suspended particles, dissolved organic chemicals, and other contaminants, effectively reducing turbidity and associated taste and odor problems. The removal of turbidity and dissolved organic compounds from the water enables the use of low-cost disinfection methods, such as chlorination. While the working principles of slow sand filtration have rem...
Polycyclic aromatic hydrocarbons (PAHs) are known to be toxic and some are even carcinogenic. A p... more Polycyclic aromatic hydrocarbons (PAHs) are known to be toxic and some are even carcinogenic. A prime source of PAHs is coal tar. Coal tar can be found in soils and sediments near former manufactured gas plants (MGPs) or coking facilities. This study involves characterizing the chemical composition and concentrations of PAHs within stream sediments at a former MGP site by Pleasant Run Creek in Indianapolis, Indiana. To characterize the stream sediments, sediment cores were removed from various locations along the stream and sampled with depth. Sample collection was conducted in partnership with the environmental engineering firm, August Mack Environmental. Samples were taken at 2 feet intervals from the surface (0.5 ft.) to a depth of 8 to 12 feet. Since the study is ongoing, samples continue to be processed in the lab to analyze concentrations of 17 PAHs by gas chromatography-mass spectrometry (GC/MS). A comparison between measured concentrations and published risk-based criteria w...
Environmental Science: Processes & Impacts, 2020
The in situ manufacture of cured-in-place-pipe (CIPP) plastic liners in damaged sewer pipes is an... more The in situ manufacture of cured-in-place-pipe (CIPP) plastic liners in damaged sewer pipes is an emerging mobile source of anthropogenic air pollution.
Anthropogenic water use and reuse represent major components of the water cycle. In the context o... more Anthropogenic water use and reuse represent major components of the water cycle. In the context of climate change, water reuse and recycling are considered necessary components for an integrated water management approach. Unplanned, or de facto, indirect water reuse occurs in most of the U.S. river systems, however, there is little real-time documentation of it. Despite the fact that there are national and state agencies that systematically collect data on water withdrawals and wastewater discharges, their databases are organized and managed in a way that makes it challenging to use them for water resource management analysis. The ability to combine reported water data to perform large scale analysis about water use and reuse is severely limited. In this paper, we apply a simple but effective methodology to complete a time series watershed-scale analysis of water use and unplanned indirect reuse for the Wabash River Watershed. Results document the occurrence of indirect water reuse, ranging from 3% to 134%, in a water-rich area of the U.S. The time series analysis shows that reported data effectively describe the water use trends through nine years, from 2009 to 2017, clearly reflecting both anthropogenic and natural events in the watershed, such as the retirement of thermoelectric power plants, and the occurrence of an extreme drought in 2012. We demonstrate the feasibility and significance of using available water datasets to perform large scale water use analysis, describe limitations encountered in the process, and highlight areas for improvement in water data management.
Ion exchange selectivity coefficients for a new cross-linked micellar nanoparticle are reported a... more Ion exchange selectivity coefficients for a new cross-linked micellar nanoparticle are reported and are used to predict specific ion recovery (e.g., phosphate) across dialysis membranes.
Cured-in-place-pipes (CIPP) are plastic liners chemically manufactured inside existing damaged se... more Cured-in-place-pipes (CIPP) are plastic liners chemically manufactured inside existing damaged sewer pipes. They are gaining popularity in North America, Africa, Asia, Europe, and Oceania. Volatile and semi-volatile organic compound (VOC/SVOC) emissions from storm sewer CIPP installations were investigated at a dedicated outdoor research site. Tedlar bag, sorbent tube, and photoionization detector (PID) air sampling was conducted for five steam-CIPP installations and was coupled with composite characterizations. New CIPPs contained up to 2.21 wt% volatile material and only 6-31% chemical mass extracted per CIPP was identified. Each 6.1 m [20 ft] liner contained an estimated 5-10 kg [11-22 lbs] of residual chemical. Extracted chemicals included hazardous air pollutants and suspected and known carcinogens that were not reported by others. These included monomers, monomer oxidation products, antioxidants, initiator degradation products, and a plasticizer. PID signals did not accurately represent styrene air concentration differing sometimes by 10s-to 1000s-fold. Multiple VOCs found in air samples likely affected PID responses. Styrene (> 86.4 ppm v) and methylene chloride (> 1.56 ppm v) air concentrations were likely greater onsite and phenol was also detected. Additional studies are needed to examine pollutant emissions so process monitoring can be improved, and environment impacts and associated human exposures can be minimized.
Storm water culverts are integral for U.S. public safety and welfare, and their mechanical failur... more Storm water culverts are integral for U.S. public safety and welfare, and their mechanical failure can cause roadways to collapse. To repair these buried assets, ultraviolet (UV) light cured-inplace-pipes (CIPP) are being installed. Chemical emission and residual material left behind from the installation process was investigated in New York and Virginia. Samples of an uncured resin tube and field-cured styrene-based resin CIPPs were collected and analyzed. Also collected were air and water samples before, during, and after installations. Chemicals were emitted into air because of the installation and curing processes. Particulates emitted into the air, water, and soil contained fiberglass, polymer, and contaminants, some of which are regulated by state-level water quality standards. The uncured resin tube contained more than 70 chemical compounds, and 19 were confirmed with analytical standards. Compounds included known and suspected carcinogens, endocrine disrupting compounds, hazardous air pollutants, and other compounds with little aquatic toxicity data available. Compounds (14 of 19 confirmed) were extracted from the newly installed CIPPs, and 11 were found in water samples. Aqueous styrene (2.31 mg/L), dibutyl phthalate (12.5 µg/L), and phenol (16.7 µg/L) levels exceeded the most stringent state water quality standards chosen in this study. Styrene was the only compound that was found to have exceed a 48 hr aquatic toxicity threshold. Newly installed CIPPs contained a significant amount volatile material (1.0-6.8 wt%). Recommendations provided can reduce chemical emission, as well as improve worksite and environmental protection practices. Recommended future research is also described. CAPSULE: Manufacture of plastic storm water culvert linings can cause environmental pollution and research must be conducted to develop evidence-based controls.
The association reactions involving counterions, Na + and Mg 2+ , and micelles composed of the an... more The association reactions involving counterions, Na + and Mg 2+ , and micelles composed of the anionic surfactant, dodecylsulfate (DS-), were investigated in ultrafiltration experiments. To access the data, an innovative model was developed that considered specific counterion binding within a Stern layer, with binding constant dependent upon the electrical potential as derived by the Poisson-Boltzmann equation and with calculation of the cmc as a function of counterion binding (or association). The experimental and model results both show that magnitude of counterion binding is greater for divalent species, Mg 2+ , than that for the monovalent species, Na 2+. However, high concentration of Na + compete for surface area diminishing the ability of the DSto bind either divalent species. At experimental conditions from 0 to 100 mM NaCl addition, the binding ratio (BR) varied only from 0.58 to 0.63. The optimum binding constants, K Mg and K Na , were determined to be 0.4 and 1.0 L mol-1 , respectively, for the model. The experimental data and model calculated results were generally in good agreement.
A five-stage consecutive irreversible model is derived to predict the photodegradation of hexachl... more A five-stage consecutive irreversible model is derived to predict the photodegradation of hexachlorobenzene (HCB) in a surfactant solution, which was proven to be a useful treatment process following the surfactant-aided soil washing or remediation. The photodegradation of HCB in surfactant micelles is dominated by photodechlorination, which sequentially removes chlorides one at a time. The minor pathways of photoisomerization and photochlorination were neglected in the kinetic model. The results show that the derived consecutive irreversible model can accurately predict the decay of HCB and the formation (and decay) of its less-chlorinated congeners. The initial rate approach was used to identify the proper range of decay rate of each chlorinated benzene; so the overall rate constants can be determined easier by trial. The decreased performance of a completely mixed flow reactor (CMFR) with continuous input is also quantified compared to a batch reactor.
Abstract Although induction of oxidative stress is widely accepted as one of the major cytotoxic ... more Abstract Although induction of oxidative stress is widely accepted as one of the major cytotoxic effects of carbon nanotubes (CNTs), there is no solid understanding of how biological redox reactions are affected and how reactive oxygen species (ROS) are generated by CNTs, especially when they are coated with various dispersing agents. In this study, we investigated electron transfer from biological reducing agents through nonfunctionalized single-walled carbon nanotubes (SWCNTs) to molecular oxygen, generating ROS in the process. Electron transfer rates in the colloidal SWCNT suspensions depended on the dispersant used to stabilize them, with six dispersants examined. Oxidation of both nicotinamide adenine dinucleotide (NADH) and dithiothreitol was catalyzed by SWCNTs coated with either cetyltrimethylammonium bromide (CTAB) or Suwannee River natural organic matter (SRNOM). SWCNTs coated with other types of surfactants showed only slight effect. In the presence of NADH or dithiothreitol, generation of ROS also was dispersant-dependent, with CTAB- and SRNOM-coated SWCNTs generating significant amounts of superoxide anion and hydrogen peroxide. In systems containing xanthine and xanthine oxidase, accumulated charge on the SWCNTs appeared to be transferred to superoxide anion, resulting in indirect disproportionation of superoxide anion, forming more hydrogen peroxide.
This study shows that O2˙− and H2O2 are produced through reduction of O2 upon solar light irradia... more This study shows that O2˙− and H2O2 are produced through reduction of O2 upon solar light irradiation of aqueous graphene oxide.
Environmental pollution (Barking, Essex : 1987), Jan 14, 2016
Recent studies indicate that while unfunctionalized carbon nanomaterials (CNMs) exhibit very low ... more Recent studies indicate that while unfunctionalized carbon nanomaterials (CNMs) exhibit very low decomposition rates in soils, even minor surface functionalization (e.g., as a result of photochemical weathering) may accelerate microbial decay. We present results from a C60 fullerene-soil incubation study designed to investigate the potential links between photochemical and microbial degradation of photo-irradiated C60. Irradiating aqueous (13)C-labeled C60 with solar-wavelength light resulted in a complex mixture of intermediate products with decreased aromaticity. Although addition of irradiated C60 to soil microcosms had little effect on net soil respiration, excess (13)C in the respired CO2 demonstrates that photo-irradiating C60 enhanced its degradation in soil, with ∼0.78% of 60 day photo-irradiated C60 mineralized. Community analysis by DGGE found that soil microbial community structure was altered and depended on the photo-treatment duration. These findings demonstrate how ab...
Indirect water reuse is ubiquitous with limited quantitative documentation of it. • Water data ar... more Indirect water reuse is ubiquitous with limited quantitative documentation of it. • Water data are uncoordinated; limiting analysis of water resources at watershed scales. • Water extraction, use, discharge, and reuse were computed at a large watershed scale. • At low flow, wastewater comprises most river flow with significant groundwater added. • Intentional wastewater reuse for consumptive purposes may have ecological impacts.
This paper reports on a study of the formation of an unidentified product(s) of the slow decompos... more This paper reports on a study of the formation of an unidentified product(s) of the slow decomposition of monochloramine in organic free aqueous solutions at pH values and Cl/N ratios of importance in the chloramination disinfection of drinking water. Chloramine and total oxidant ...
The advective flow of sediment pore water is an important parameter for understanding natural geo... more The advective flow of sediment pore water is an important parameter for understanding natural geochemical processes within lake, river, wetland, and marine sediments and also for properly designing permeable remedial sediment caps placed over contaminated sediments. Automated heat pulse seepage meters can be used to measure the vertical component of sediment pore water flow (i.e., vertical Darcy velocity); however, little information on meter calibration as a function of ambient water temperature exists in the literature. As a result, a method with associated equations for calibrating a heat pulse seepage meter as a function of ambient water temperature is fully described in this paper. Results of meter calibration over the temperature range 7.5 to 21.2 ° C indicate that errors in accuracy are significant if proper temperature-dependence calibration is not performed. The proposed calibration method allows for temperature corrections to be made automatically in the field at any ambie...
Low density polyethylene (LDPE) often is used as the sorbent material in passive sampling devices... more Low density polyethylene (LDPE) often is used as the sorbent material in passive sampling devices to estimate the average temporal chemical concentration in water bodies or sediment pore water. To calculate water phase chemical concentrations from LDPE concentrations accurately, it is necessary to know the LDPE-water partition coefficients (KPE-w) of the chemicals of interest. However, even moderately hydrophobic chemicals have large KPE-w values, making direct measurement experimentally difficult. In this study we evaluated a simple three phase system from which KPE-w can be determined easily and accurately. In the method, chemical equilibrium distribution between LDPE and a surfactant micelle pseudo-phase is measured, with the ratio of these concentrations equal to the LDPE-micelle partition coefficient (KPE-mic). By employing sufficient mass of polymer and surfactant (Brij 30), the mass of chemical in the water phase remains negligible, albeit in equilibrium. In parallel, the mic...
International Journal of Environmental Research and Public Health
Safe drinking water remains a major global challenge, especially in rural areas where, according ... more Safe drinking water remains a major global challenge, especially in rural areas where, according to UNICEF, 80% of those without access to improved water systems reside. While water, sanitation, and hygiene (WASH)-related diseases and deaths are common outcomes of unsafe water, there is also an economic burden associated with unsafe water. These burdens are most prominent in rural areas in less-developed nations. Slow sand filters (SSFs), or biological sand filters (BSFs), are ideal water treatment solutions for these low-resource regions. SSFs are the oldest municipal drinking water treatment systems and improve water quality by removing suspended particles, dissolved organic chemicals, and other contaminants, effectively reducing turbidity and associated taste and odor problems. The removal of turbidity and dissolved organic compounds from the water enables the use of low-cost disinfection methods, such as chlorination. While the working principles of slow sand filtration have rem...
Polycyclic aromatic hydrocarbons (PAHs) are known to be toxic and some are even carcinogenic. A p... more Polycyclic aromatic hydrocarbons (PAHs) are known to be toxic and some are even carcinogenic. A prime source of PAHs is coal tar. Coal tar can be found in soils and sediments near former manufactured gas plants (MGPs) or coking facilities. This study involves characterizing the chemical composition and concentrations of PAHs within stream sediments at a former MGP site by Pleasant Run Creek in Indianapolis, Indiana. To characterize the stream sediments, sediment cores were removed from various locations along the stream and sampled with depth. Sample collection was conducted in partnership with the environmental engineering firm, August Mack Environmental. Samples were taken at 2 feet intervals from the surface (0.5 ft.) to a depth of 8 to 12 feet. Since the study is ongoing, samples continue to be processed in the lab to analyze concentrations of 17 PAHs by gas chromatography-mass spectrometry (GC/MS). A comparison between measured concentrations and published risk-based criteria w...
Environmental Science: Processes & Impacts, 2020
The in situ manufacture of cured-in-place-pipe (CIPP) plastic liners in damaged sewer pipes is an... more The in situ manufacture of cured-in-place-pipe (CIPP) plastic liners in damaged sewer pipes is an emerging mobile source of anthropogenic air pollution.
Anthropogenic water use and reuse represent major components of the water cycle. In the context o... more Anthropogenic water use and reuse represent major components of the water cycle. In the context of climate change, water reuse and recycling are considered necessary components for an integrated water management approach. Unplanned, or de facto, indirect water reuse occurs in most of the U.S. river systems, however, there is little real-time documentation of it. Despite the fact that there are national and state agencies that systematically collect data on water withdrawals and wastewater discharges, their databases are organized and managed in a way that makes it challenging to use them for water resource management analysis. The ability to combine reported water data to perform large scale analysis about water use and reuse is severely limited. In this paper, we apply a simple but effective methodology to complete a time series watershed-scale analysis of water use and unplanned indirect reuse for the Wabash River Watershed. Results document the occurrence of indirect water reuse, ranging from 3% to 134%, in a water-rich area of the U.S. The time series analysis shows that reported data effectively describe the water use trends through nine years, from 2009 to 2017, clearly reflecting both anthropogenic and natural events in the watershed, such as the retirement of thermoelectric power plants, and the occurrence of an extreme drought in 2012. We demonstrate the feasibility and significance of using available water datasets to perform large scale water use analysis, describe limitations encountered in the process, and highlight areas for improvement in water data management.
Ion exchange selectivity coefficients for a new cross-linked micellar nanoparticle are reported a... more Ion exchange selectivity coefficients for a new cross-linked micellar nanoparticle are reported and are used to predict specific ion recovery (e.g., phosphate) across dialysis membranes.
Cured-in-place-pipes (CIPP) are plastic liners chemically manufactured inside existing damaged se... more Cured-in-place-pipes (CIPP) are plastic liners chemically manufactured inside existing damaged sewer pipes. They are gaining popularity in North America, Africa, Asia, Europe, and Oceania. Volatile and semi-volatile organic compound (VOC/SVOC) emissions from storm sewer CIPP installations were investigated at a dedicated outdoor research site. Tedlar bag, sorbent tube, and photoionization detector (PID) air sampling was conducted for five steam-CIPP installations and was coupled with composite characterizations. New CIPPs contained up to 2.21 wt% volatile material and only 6-31% chemical mass extracted per CIPP was identified. Each 6.1 m [20 ft] liner contained an estimated 5-10 kg [11-22 lbs] of residual chemical. Extracted chemicals included hazardous air pollutants and suspected and known carcinogens that were not reported by others. These included monomers, monomer oxidation products, antioxidants, initiator degradation products, and a plasticizer. PID signals did not accurately represent styrene air concentration differing sometimes by 10s-to 1000s-fold. Multiple VOCs found in air samples likely affected PID responses. Styrene (> 86.4 ppm v) and methylene chloride (> 1.56 ppm v) air concentrations were likely greater onsite and phenol was also detected. Additional studies are needed to examine pollutant emissions so process monitoring can be improved, and environment impacts and associated human exposures can be minimized.
Storm water culverts are integral for U.S. public safety and welfare, and their mechanical failur... more Storm water culverts are integral for U.S. public safety and welfare, and their mechanical failure can cause roadways to collapse. To repair these buried assets, ultraviolet (UV) light cured-inplace-pipes (CIPP) are being installed. Chemical emission and residual material left behind from the installation process was investigated in New York and Virginia. Samples of an uncured resin tube and field-cured styrene-based resin CIPPs were collected and analyzed. Also collected were air and water samples before, during, and after installations. Chemicals were emitted into air because of the installation and curing processes. Particulates emitted into the air, water, and soil contained fiberglass, polymer, and contaminants, some of which are regulated by state-level water quality standards. The uncured resin tube contained more than 70 chemical compounds, and 19 were confirmed with analytical standards. Compounds included known and suspected carcinogens, endocrine disrupting compounds, hazardous air pollutants, and other compounds with little aquatic toxicity data available. Compounds (14 of 19 confirmed) were extracted from the newly installed CIPPs, and 11 were found in water samples. Aqueous styrene (2.31 mg/L), dibutyl phthalate (12.5 µg/L), and phenol (16.7 µg/L) levels exceeded the most stringent state water quality standards chosen in this study. Styrene was the only compound that was found to have exceed a 48 hr aquatic toxicity threshold. Newly installed CIPPs contained a significant amount volatile material (1.0-6.8 wt%). Recommendations provided can reduce chemical emission, as well as improve worksite and environmental protection practices. Recommended future research is also described. CAPSULE: Manufacture of plastic storm water culvert linings can cause environmental pollution and research must be conducted to develop evidence-based controls.
The association reactions involving counterions, Na + and Mg 2+ , and micelles composed of the an... more The association reactions involving counterions, Na + and Mg 2+ , and micelles composed of the anionic surfactant, dodecylsulfate (DS-), were investigated in ultrafiltration experiments. To access the data, an innovative model was developed that considered specific counterion binding within a Stern layer, with binding constant dependent upon the electrical potential as derived by the Poisson-Boltzmann equation and with calculation of the cmc as a function of counterion binding (or association). The experimental and model results both show that magnitude of counterion binding is greater for divalent species, Mg 2+ , than that for the monovalent species, Na 2+. However, high concentration of Na + compete for surface area diminishing the ability of the DSto bind either divalent species. At experimental conditions from 0 to 100 mM NaCl addition, the binding ratio (BR) varied only from 0.58 to 0.63. The optimum binding constants, K Mg and K Na , were determined to be 0.4 and 1.0 L mol-1 , respectively, for the model. The experimental data and model calculated results were generally in good agreement.
A five-stage consecutive irreversible model is derived to predict the photodegradation of hexachl... more A five-stage consecutive irreversible model is derived to predict the photodegradation of hexachlorobenzene (HCB) in a surfactant solution, which was proven to be a useful treatment process following the surfactant-aided soil washing or remediation. The photodegradation of HCB in surfactant micelles is dominated by photodechlorination, which sequentially removes chlorides one at a time. The minor pathways of photoisomerization and photochlorination were neglected in the kinetic model. The results show that the derived consecutive irreversible model can accurately predict the decay of HCB and the formation (and decay) of its less-chlorinated congeners. The initial rate approach was used to identify the proper range of decay rate of each chlorinated benzene; so the overall rate constants can be determined easier by trial. The decreased performance of a completely mixed flow reactor (CMFR) with continuous input is also quantified compared to a batch reactor.
Abstract Although induction of oxidative stress is widely accepted as one of the major cytotoxic ... more Abstract Although induction of oxidative stress is widely accepted as one of the major cytotoxic effects of carbon nanotubes (CNTs), there is no solid understanding of how biological redox reactions are affected and how reactive oxygen species (ROS) are generated by CNTs, especially when they are coated with various dispersing agents. In this study, we investigated electron transfer from biological reducing agents through nonfunctionalized single-walled carbon nanotubes (SWCNTs) to molecular oxygen, generating ROS in the process. Electron transfer rates in the colloidal SWCNT suspensions depended on the dispersant used to stabilize them, with six dispersants examined. Oxidation of both nicotinamide adenine dinucleotide (NADH) and dithiothreitol was catalyzed by SWCNTs coated with either cetyltrimethylammonium bromide (CTAB) or Suwannee River natural organic matter (SRNOM). SWCNTs coated with other types of surfactants showed only slight effect. In the presence of NADH or dithiothreitol, generation of ROS also was dispersant-dependent, with CTAB- and SRNOM-coated SWCNTs generating significant amounts of superoxide anion and hydrogen peroxide. In systems containing xanthine and xanthine oxidase, accumulated charge on the SWCNTs appeared to be transferred to superoxide anion, resulting in indirect disproportionation of superoxide anion, forming more hydrogen peroxide.
This study shows that O2˙− and H2O2 are produced through reduction of O2 upon solar light irradia... more This study shows that O2˙− and H2O2 are produced through reduction of O2 upon solar light irradiation of aqueous graphene oxide.
Environmental pollution (Barking, Essex : 1987), Jan 14, 2016
Recent studies indicate that while unfunctionalized carbon nanomaterials (CNMs) exhibit very low ... more Recent studies indicate that while unfunctionalized carbon nanomaterials (CNMs) exhibit very low decomposition rates in soils, even minor surface functionalization (e.g., as a result of photochemical weathering) may accelerate microbial decay. We present results from a C60 fullerene-soil incubation study designed to investigate the potential links between photochemical and microbial degradation of photo-irradiated C60. Irradiating aqueous (13)C-labeled C60 with solar-wavelength light resulted in a complex mixture of intermediate products with decreased aromaticity. Although addition of irradiated C60 to soil microcosms had little effect on net soil respiration, excess (13)C in the respired CO2 demonstrates that photo-irradiating C60 enhanced its degradation in soil, with ∼0.78% of 60 day photo-irradiated C60 mineralized. Community analysis by DGGE found that soil microbial community structure was altered and depended on the photo-treatment duration. These findings demonstrate how ab...
Indirect water reuse is ubiquitous with limited quantitative documentation of it. • Water data ar... more Indirect water reuse is ubiquitous with limited quantitative documentation of it. • Water data are uncoordinated; limiting analysis of water resources at watershed scales. • Water extraction, use, discharge, and reuse were computed at a large watershed scale. • At low flow, wastewater comprises most river flow with significant groundwater added. • Intentional wastewater reuse for consumptive purposes may have ecological impacts.
This paper reports on a study of the formation of an unidentified product(s) of the slow decompos... more This paper reports on a study of the formation of an unidentified product(s) of the slow decomposition of monochloramine in organic free aqueous solutions at pH values and Cl/N ratios of importance in the chloramination disinfection of drinking water. Chloramine and total oxidant ...
The advective flow of sediment pore water is an important parameter for understanding natural geo... more The advective flow of sediment pore water is an important parameter for understanding natural geochemical processes within lake, river, wetland, and marine sediments and also for properly designing permeable remedial sediment caps placed over contaminated sediments. Automated heat pulse seepage meters can be used to measure the vertical component of sediment pore water flow (i.e., vertical Darcy velocity); however, little information on meter calibration as a function of ambient water temperature exists in the literature. As a result, a method with associated equations for calibrating a heat pulse seepage meter as a function of ambient water temperature is fully described in this paper. Results of meter calibration over the temperature range 7.5 to 21.2 ° C indicate that errors in accuracy are significant if proper temperature-dependence calibration is not performed. The proposed calibration method allows for temperature corrections to be made automatically in the field at any ambie...
Low density polyethylene (LDPE) often is used as the sorbent material in passive sampling devices... more Low density polyethylene (LDPE) often is used as the sorbent material in passive sampling devices to estimate the average temporal chemical concentration in water bodies or sediment pore water. To calculate water phase chemical concentrations from LDPE concentrations accurately, it is necessary to know the LDPE-water partition coefficients (KPE-w) of the chemicals of interest. However, even moderately hydrophobic chemicals have large KPE-w values, making direct measurement experimentally difficult. In this study we evaluated a simple three phase system from which KPE-w can be determined easily and accurately. In the method, chemical equilibrium distribution between LDPE and a surfactant micelle pseudo-phase is measured, with the ratio of these concentrations equal to the LDPE-micelle partition coefficient (KPE-mic). By employing sufficient mass of polymer and surfactant (Brij 30), the mass of chemical in the water phase remains negligible, albeit in equilibrium. In parallel, the mic...
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Papers by Chad Jafvert