Geosyntec will deliver a number of presentations at the 37th Annual Meeting of the Society of Environmental Toxicology and Chemistry (SETAC) North America at the Rosen Shingle Creek in Orlando, Florida on November 6-10, 2016.
This year, Geosyntec continues our tradition of practice excellence by providing presentations on the cutting edge environmental science and technology including per- and polyfluoroalkyl substances, a class of emerging chemicals of concern, and the use of activated carbon as an emerging technology in sediment remediation.
SETAC Orlando is a 5-day event featuring a variety of training, networking and learning opportunities for professionals interested in emerging research, regulatory developments and the latest methodologies in environmental toxicology and chemistry. More than 2,500 scientists, assessors, regulators and managers from academia, business and government, representing 40 plus countries are expected to attend. The meeting provides a networking opportunity for specialists in the field, and is a chance for cross-collaboration within the profession.
SETAC is a not-for-profit, worldwide professional organization comprised of more than 6,000 individuals and institutions in l00 countries dedicated to the study, analysis and solution of environmental problems, the management and regulation of natural resources, research and development, and environmental education. Our mission is to support the development of principles and practices for protection, enhancement and management of sustainable environmental quality and ecosystem integrity.
Title: Measures of Chemical Availability for Enhancing Risk Assessments of PAHs in Soil
Presenter: Jason M. Conder (California)
A major uncertainty of many site-specific human health and mammalian risk assessments is the digestive bioavailability of Polycyclic Aromatic Hydrocarbons (PAHs) consumed via the incidental ingestion of contaminated soils. Relative to the bioavailability of PAHs used in spiked foods used in laboratory toxicity tests, soil-associated PAHs at contaminated sites are generally much less available. For example, laboratory tests that have measured in vivo exposures have noted that PAHs in soil contaminated with solid materials (e.g., soot) or weathered petroleum are many times less bioavailable compared to PAHs that have been freshly spiked with solvent or unweathered petroleum. This reduced bioavailability can be quantitatively accounted for in risk assessments using a Relative Bioavailability (RBA) value. However, laboratory feeding trials with live animals are expensive ($50,000 to $100,000 range or more) and require many weeks of experimental work. Fortunately, less expensive and more rapid chemical availability measures can be used to provide RBA information. This presentation provides an evaluation of two such tools: 1) Physiologically Based Extraction Tests (PBET) that extract PAHs from soil using a simulated digestive matrix; and 2) determination of freely-dissolved PAHs in soil via a commercially-available polyethylene passive sampling device. PBET and passive sampling results were evaluated for soils contaminated with solids-associated PAHs and compared to dose and RBA estimates for benzo(a)pyrene values generated from a laboratory experiment with rodents fed small amounts of the soils. Freely-dissolved PAHs data from the passive sampling measurements indicated that PAHs were approximately 10 to 100 times less available than PAHs spiked with unweathered petroleum and solvent, respectively, confirming the low availability of the solids-associated PAHs in the soils tested. Both chemical measures were positively correlated with benzo(a)pyrene bioavailability measurements obtained from the rodent feeding trial, indicating that empirical models may be able to be developed to relate chemical PAH availability measures to RBA estimates such that PBET and passive sampling data may be used to predict RBA values for use in risk assessments. PBET and passive sampling chemical measurements appear to be cost- and time-effective tools for predicting mammalian digestive PAH availability and improving the accuracy of site-specific PAH risk assessments.
Title: Visibly-detectable Dyes as Performance Reference Compounds in Passive Sampling Devices
Presenter: Jason M. Conder (California)
Dozens of research efforts in the previous 10+ years have demonstrated that measurements made using Passive Sampling Devices (PSDs) represent precise and accurate estimates of available organic compounds in aquatic sediment, surface water, and soil. To overcome the challenges of impractical PSD deployment times in environmental matrices, the PSD research community has adopted the use of Performance Reference Compounds (PRCs) which are loaded into PSDs prior to deployment and used to infer the fraction of steady state attained during the deployment. Traditional PRCs have included compounds with a similar hydrophobicity to the compounds of interest such as stable isotope‐labeled or deuterated forms of the compounds of interest or compounds that are not expected to be absorbed in significant amounts (e.g., rare Polychlorinated Biphenyl (PCB) congeners). Adding these PRCs to PSDs is expensive and requires complicated and time-consuming PRC measurement techniques (e.g., GC or HPLC methods). This presentation will highlight the application of a potentially more time- and cost-efficient suite of compounds for PRCs: visibly-detectable dye compounds. Compared to compounds traditionally used as PRCs, dyes are orders of magnitude less expensive, generally less toxic, can be added and extracted from PSDs in amounts easily measured via Ultraviolent/Visible (UV/VIS) spectroscopy or other visible/colorimetric means, and can be observed in the PSDs with the naked eye. Measurement of dyes in PSDs can be performed with an inexpensive benchtop UV/VIS spectrophotometer via a non-destructive technique in a matter of seconds for a fraction of the cost to measure traditional PRCs. This presentation will detail the approaches and benefits of using dyes as PRCs in a commercially-available PSD, as well as empirical evidence that demonstrates the proof of concept. Our experiments in static and mixed PSD deployments in the laboratory, as well as deployments in the field, indicate the kinetics of dye PRC desorption match those of target analytes (and traditional PRCs) such that dye PRCs can serve as replacements for traditional PRCs. Overall, the use of dye PRCs will allow a much more streamlined and efficient approach for PSD research and development and will also enable more cost-effective analytical chemistry techniques.
Title: Using a Commercially-available Passive Sampling Device To Monitor Hydrophobic Organic Contaminants in the Laboratory and the Field
Presenter: Jeff Roberts (Ontario)
Passive sampling devices (PSDs) present many advantages over conventional aqueous samples for quantifying hydrophobic organic compound (HOCs) concentrations in pore water (sediment and soil), surface water and storm water in terms of cost and data usability. They provide data to estimate contaminant bioavailability and toxicity to environmental receptors that is more representative than conventional grab samples, as it quantifies contaminants only in the dissolved form. In the field, PSDs enable collection of representative- and depth-discrete data without the need to collect large volume aqueous samples. Similarly, in laboratory treatability studies to evaluate remedial options for contaminated sediments or soils, passive samplers help to decrease the volume and number of samples required. Passive samplers deployed in these studies provide the ability to compare different treatment technologies in a relatively short time frame, test multiple conditions concurrently, and enable the flexibility to allow changes to a remediation strategy that would be impractical at field-scale.
This presentation will highlight the benefits of using PSDs in both laboratory treatability studies and field applications as well as discuss the practical lessons learned from applying passive sampling techniques, drawing from several case studies using a commercially-available PSD. In one study, PCB availability of a sediment amended with activated carbon, zero valent iron, siderite and sulfur was measured with PSDs. The results were used to determine the most effective commercial amendment for decreasing PCB concentrations in pore water, with PSDs demonstrating that the selected remedy achieved a >95% reduction in PCB availability. In another study, PSDs were used to characterize PCB concentrations in sediment pore water amended with different amounts of activated carbon and the results were used to determine the optimal dose of carbon for the field application, with PSDs demonstrating that the optimal activated carbon application rate resulted in a 98% reduction in PCB availability. At this same site, PSDs were deployed in the field to provide baseline PCB availability data prior to activated carbon amendment, and the PSDs will be used for post amendment monitoring to document remedial success. It is clear that currently-available passive sampling approaches are ready for widespread application and can provide high-quality data to aid environmental decision makers.
Title: Predicting Passive Sampler Equilibration Times for PAHs in an Amended Sand Cap
Presenter: Jeff Roberts (Ontario)
PAHs in sediment pore water can be sequestered before upwelling water reaches the sediment-water interface using amended sand caps with amendments such as activated carbon and biochar. Passive samplers offer a method to monitor remedy effectiveness. A key condition for using passive samplers to directly estimate hydrophobic organic compounds (HOCs) pore water concentrations is that the concentrations of the HOCs being sampled are in equilibrium between the sampler and the pore water. The time to achieve equilibrium between the passive sampler and the surrounding pore water is dependent on both the hydrophobicity of the HOC and the surrounding chemical environment. The loss of performance reference compounds (PRCs) during deployment of a passive sampler allows for the estimation of the degree of equilibrium achieved or confirmation of the achievement of equilibrium. If the passive sampler is found not to be at equilibrium with the surrounding pore water, then the PRC data can provide an estimation of passive sampler uptake rates for calculation of the equilibrium pore water HOC concentrations.
This presentation will show theoretical and empirical data demonstrating the difference in estimated equilibration times for various PAH compounds in different amended sediment cap environments. The equilibration times measured ranged from ~20 days in a powdered activated carbon (PAC) amended cap environment to ~200+ days in a sand only cap with no flowing water. Equilibration times were determined using deuterated PAH and hydrophobic dye PRCs. The results of the research can be used to determine if PRCs are required in passive sampling programs depending on the cap conditions (e.g. PAC or no PAC), HOCs of interested being measured and estimated sample deployment time.
Title: Avian Exposures to Seven Perfluorinated Alkyl Substances in Aquatic Habitats Impacted by Aqueous Film Forming Foam Releases
Presenter: Emily J. Stinson (Colorado)
Information on the adverse effects of perfluorinated and polyfluorinated alkyl substances (PFAS) in animals is primarily limited to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). While detectable levels of PFOS and PFOA in environmental media are known to be present at many sites as a result of Aqueous Film Forming Foam (AFFF) releases, less is known about other prominent PFAS chemicals. Since birds may have relatively high exposure potential due to consumption of fish, invertebrates, and sediment in aquatic habitats affected by AFFF releases, avian exposures were evaluated for seven PFAS chemicals (PFOS, PFOA, perfluorodecanoic acid (PFDA), perfluorononanoic acid (PFNA), perfluorodecane sulfonate (PFDS), perfluorohexanoic acid (PFHxA), and perfluorohexane sulfonate (PFHxS)) using measurements from four AFFF sites. Exposure modeling was conducted for four avian receptors representing various avian feeding guilds including: lesser scaup (Aythya affinis), spotted sandpiper (Actitis macularia), Great blue heron (Ardea herodias), and osprey (Pandion haliaetus). On average, 80% of PFAS exposures were from PFOS for all receptors at almost all sites (with the exception of Site A). For the spotted sandpiper and the lesser scaup, PFHxS comprised over 10% of the total daily intake (TDI). The sediment pathway was the dominant exposure route, however surface water route greatly contributed to the great blue heron and osprey PFAS TDI (45% and 59% respectively). These results suggest the need for ecological modeling at sites potentially affected by AFFF releases to include multiple representative species and expand the current focus on PFOS and PFOA to other bioaccumulative PFAS chemicals. This evaluation enhances risk management and risk communication by identifying additional PFAS chemicals (e.g., PFHxS) that have the potential to influence ecological risk-based decision making at AFFF sites.
Title: Evaluation of Site-specific Human Health Risks and Calculation of Risk-based Threshold Concentrations of PFOS and PFOA Using Bioaccumulation Modeled Fish Tissue Concentrations
Presenter: Jennifer A. Arblaster (California)
The United States Environmental Protection Agency recently finalized toxicity reference doses (RfD) and drinking water quality criteria for the perfluoroalkyl and polyfluoroalkyl substances (PFASs) perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Along with drinking water and indoor dust, diet items including fish and shellfish may be a significant contribution to human intake of PFASs. To evaluate the potential risks to human health from consumption of fish tissue by recreational fishermen, a Fish Tissue Criteria (FTC) was derived from the RfD for the sum of the PFOS and PFOA. A RSC of 20% and 100% were both assumed for evaluation of human health risks from sites with historical PFAS contamination. The FTC for the sum of PFOS and PFOA ranged from 15 ng/g to 73 ng/g, wet weight for a 20% and 100% RSC, respectively. The FTC was compared to empirical concentrations of PFASs in fish from four sites with historic PFAS contamination, and concentrations in fish exceeded the FTCs at 75% of sites using an RSC of 100% and all four sites when using an RSC of 20%. PFOS represented 99% of the sum of the PFOS and PFOA exposure in fish where measured concentrations of both were available. Additionally, a food web model was used to calculate risk-based concentrations of PFOA and PFOS in sediment and water that would be associated with the FTC. The model showed good agreement between modeled and empirical concentrations in fish (when available for a site) with a mean model bias of 0.9 for PFOS and 2.9 for PFOA. Assuming a 20% RSC, absence of model-predicted risk is expected if concentrations of PFOS sediment and surface water are both less than 0.75 ng/g, dw (assuming 1% OC) for sediment and 12.4 ng/L respectively. Assuming a 100% RSC, absence of model-predicted risk is expected if concentrations of PFOS sediment and surface water are both less than 3.7 ng/g, dw and 62 ng/L, respectively.
Title: A Comparison of Passive Sampling and Bioaccumulation Measurements in the Evaluation of Bioavailable Concentrations of Pesticides Impacted Sediments
Presenter: Melissa Grover (California)
Bioavailability of contaminants in sediment is an important consideration in the determination of potential risk of adverse effects from exposure to benthic invertebrate. Numerous tools are used to assess bioavailability, including measurement of contaminants in tissue via bioaccumulation testing and sediment porewater with passive sampling. These tools and different methods of applications vary in cost effectiveness, efficiency, and ability to incorporate field conditions.
The performance a thin-layer habitat enhancement sand cap (target depth 6 inches) to reduce bioavailable concentrations of organochlorine pesticides (e.g., 4,4’-dichlorodiphenyldichloroethane [4,4’-DDD] and 4,4’-dichlorodiphenyldichloroethylene [4,4’-DDE]) in sediment was evaluated at Site 99 Quantico Embayment in the Quantico Marine Corps Base, Quantico, Virginia, USA. The thin-layer cap placement is expected to reduce concentrations of total DDX in sediment more rapidly than natural recovery processes alone. Prior to and following installation of the cap, monitoring at the site included three tools to assess bioavailability. Concentrations of pesticides in tissue were obtained via two-week deployment of in situ bioaccumulation testing with Sediment Ecotoxicity Assessment (SEA) Rings using two species, Lumbriculus variegatus (oligocheaete worm) and Corbicula fluminea (Asian clam). Secondly, a two-week deployment of in situ solid phase microextraction (SPME) passive sampling was used to measure porewater from 0 to 24 inches below the sediment-water interface. Lastly, ex situ SPME was also used to measure porewater at multiple depth intervals within and below the cap.
Strong correlation between concentrations of total DDX in worm tissue and surface sediment porewater as measured by both in situ and ex situ passive sampling approaches was observed. However, weak correlation of total DDX concentrations in clam tissue and surface sediment porewater as measured by both in situ and ex situ passive sampling approaches was observed, likely due to the filter feeding clam being exposed to overlying water rather than sediment porewater (moderate correlation between worm and clam tissue was observed).
For more information regarding the event, visit: https://orlando.setac.org/