Contaminants Of Concern Research Articles

Impact of ventilation and filtration strategies on energy consumption and exposures in retail stores

Different ventilation strategies can have an enormous impact on both exposures to contaminants of concern (COCs) and energy use in retail buildings. We applied a multi-contaminant model of an area-normalized retail store, and developed estimates for distributions of model inputs. We then used these distributions in a Monte Carlo simulation for six cities to compare the impacts of the ASHRAE 62.1–2013 ventilation rate procedure (VRP), demand controlled ventilation (DCV), and indoor air quality procedure (IAQP), with or without using a high particulate efficiency filter. Results showed that for cities where outdoor PM2.5 concentration is low, adopting the IAQP with low efficiency PM2.5 filter in grocery stores and the VRP with high PM2.5 efficiency in non-grocery stores yielded the greatest exposure benefits. For cities with high outdoor PM2.5 concentration, adopting the VRP with high PM2.5 efficiency for all store types yielded the greatest exposure benefits. However, these exposure benefits also caused an increase in energy consumption, and the magnitude depends on the city's climate, outdoor PM2.5 concentration and the retail store type. We propose a new pollutant exposure control ventilation (PECV) strategy, where ventilation rates are weighed against exposure to different COCs, and the ventilation rate that is most climatically advantageous is chosen.

A transition in the spatially integrated reaction rate of bimolecular reaction-diffusion systems

Numerical simulations of diffusion with bimolecular reaction demonstrate a transition in the spatially integrated reaction rate—increasing with time initially, and transitioning to a decrease with time. In previous work, this reaction-diffusion problem has been analyzed as a Stefan problem involving a distinct moving boundary (reaction front), leading to predictions that front motion scales as t, and correspondingly the spatially integrated reaction rate decreases as the square root of time 1/t. We present a general nondimensionalization of the problem and a perturbation analysis to show that there is an early time regime where the spatially integrated reaction rate scales as t rather than 1/t. The duration of this early time regime (where the spatially integrated reaction rate is kinetically rather than diffusion controlled) is shown to depend on the kinetic rate parameters, diffusion coefficients, and initial concentrations of the two species. Numerical simulation results confirm the theoretical estimates of the transition time. We present illustrative calculations in the context of in situ chemical oxidation for remediation of fractured rock systems where contaminants are largely dissolved in the rock matrix. We consider different contaminants of concern (COCs), including TCE, PCE, MTBE, and RDX. While the early time regime is very short lived for TCE, it can persist over months to years for MTBE and RDX, due to slow oxidation kinetics.

Phytoremedial Potential of Typha latifolia, Eichornia crassipes and Monochoria hastata found in Contaminated Water Bodies Across Ranchi City (India)

Phytoremediation is an emerging technology that uses green plants (living machines) for removal of contaminants of concern (COC). These plant species have the potential to remove the COC, thereby restoring the original condition of soil or water environment. The present study focuses on assessing the heavy metals (COC) present in the contaminated water bodies of Ranchi city, Jharkhand, India. Phytoremedial potential of three plant species: Typha latifolia, Eichornia crassipes and Monochoria hastata were assessed in the present study. Heterogenous accumulation of metals was found in the three plant species. It was observed that the ratio of heavy metal concentration was different in different parts, i.e., shoots and roots. Positive results were also obtained for translocation factor of all species with minimum of 0.10 and maximum of 1. It was found experimentally that M. hastata has the maximum BFC for root as 4.32 and shoot as 2.70 (for Manganese). For T. latifolia, BCF of maximum was observed for root (163.5) and respective shoot 86.46 (for Iron), followed by 7.3 and 5.8 for root and shoot (for Manganese) respectively. E. crassipes was found to possess a maximum BCF of 278.6 (for Manganese and 151 (for Iron) and shoot as 142 (for Manganese) and 36.13 (for Iron).

Performance of passive samplers for monitoring estuarine water column concentrations: 1. Contaminants of concern

Contaminants enter marine and estuarine environments and pose a risk to human and ecological health. Recently, passive sampling devices have been utilized to estimate dissolved concentrations of contaminants of concern (COCs), such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). In the present study, the performance of 3 common passive samplers was evaluated for sampling PAHs and PCBs at several stations in the temperate estuary Narragansett Bay, Rhode Island, USA. Sampler polymers included polyethylene (PE), polydimethylsiloxane (PDMS)-coated solid-phase microextraction (SPME) fibers, and polyoxymethylene (POM). Dissolved concentrations of each contaminant were calculated using measured sampler concentrations adjusted for equilibrium conditions with performance reference compounds (PRCs) and chemical-specific partition coefficients derived in the laboratory. Despite differences in PE and POM sampler concentrations, calculated total dissolved concentrations ranged from 14 ng/L to 93 ng/L and from 13 pg/L to 465 pg/L for PAHs and PCBs, respectively. Dissolved concentrations of PAHs were approximately 3 times greater based on POM compared to PE, while dissolved concentrations of PCBs based on PE were approximately 3 times greater than those based on POM. Concentrations in SPME were not reported due to the lack of detectable chemical in the amount of PDMS polymer deployed. Continued research is needed to improve and support PE and POM use for the routine monitoring of COCs. For example, a better understanding of the use of PRCs with POM is critically needed.

English

A pilot biochemical reactor (BCR) with a design flowrate of 3.8 l/m (1 gpm) has been operating at the Standard Mine Superfund Site for over four years, since August, 2007. The pilot system is entirely passive, using solar energy to power sampling equipment and pumping requirements. BCR treatment relies on biological and chemical reactions within an anaerobic reactor comprised of organic and inorganic materials including woodchips, straw, limestone and bacterial inoculum. The BCR pilot has been treating mining influenced wastewater (MIW) since construction was completed in the summer of 2007. Polishing and aeration of BCR effluent is accomplished in an aerobic polishing cell (APC) containing wetland plants in two of the three cells. The Standard Mine BCR is constructed at an elevation of 3,353 meters (11,000 ft ) above MSL with an average annual snowfall of 10.2 m (400 in ). Limited BCR treatment data from reactors operating under harsh alpine conditions was available before this system was constructed. Operation and monitoring of the BCR has been year round since 2007. Due to the inaccessibility of the site during winter months, an automated sampling system was designed incorporating Teledyne ISCO™ (ISCO) samplers, Hydrolab™ sondes, and a satellite transmission system reporting site operational parameters on a daily basis. In addition to automated sampling, grab samples were taken monthly throughout the 2010/2011 winter using backcountry skiing equipment to access the site. Contaminants of concern (COCs) in the MIW include Cd, Cu, Pb, Mn, and Zn. High metals removal has been observed in BCR effluent since the beginning of operation. In 2009, 2010, and 2011 the average percent removal efficiency for cadmium, Cu, Pb, and Zn exceeded 98%. The pilot study is notable for a long operating period and low analytical laboratory detection limits for metals. BCR treatment of cadmium, Cu, and Pb to less than 5 µg/L has been demonstrated indicating that BCR is capable of approaching or meeting stringent aquatic life water quality standards when operated under harsh high alpine conditions. Both metals and nutrient removal are discussed in relation to receiving stream water quality standards. BCR performance is discussed with additional discussion of performance of BCR effluent polishing by aerobic lagoon.

English

At the 2008 ASMR conference, data from the initial two months of operation of a U.S. EPA pilot biochemical reactor (BCR) was reported. The BCR was designed and constructed in August, 2007 to treat mining influenced water (MIW) emanating from an adit at a remote site in southern Colorado. The original objective of the study was to operate and monitor a BCR on a year-round basis in a harsh mountain environment. In the second year, a pilot chitin reactor was constructed for manganese removal. The treatment results from 13 months of BCR operation and 2 months of chitin reactor are presented. The treatment goal for the two pilot reactors was to determine compliance with the applicable surface water quality standards for the State of Colorado. Several attributes of the treatment and monitoring system were unique. It was constructed at an elevation of 11,000 feet a.m.s.l. (3,353 meters), was designed to operate year-round, and was totally passive, using solar energy for the monitoring system and pump power. Due to the site being inaccessible during winter months, this remote monitoring system was designed to collect samples and monitor field variables through the winter months. Field variables were measured and stored by Hydrolab™ sondes. Influent and effluent water quality samples were collected and stored in Teledyne™ ISCO™ 6712 samplers. For the first year of operation, the field variable data were transmitted via Stratolink™ satellite communicators. Due to operational issues, the Stratolink™ units were replaced with satellite phones in September 2008. The contaminants of concern (COCs) in the MIW are cadmium, copper, iron, lead, manganese, and zinc. BCR metal removal rates averaged approximately 98% over the first year of operation for cadmium, copper, lead, and zinc. Despite these high removal rates, the BCR effluent exceeded the applicable water quality standards for cadmium, lead, and zinc. Iron and manganese removal rates varied over the first year of BCR operation and were not sufficient to achieve the applicable water quality standards. The removal of manganese by the chitin reactor was inconsistent with an average percent removal rate of 23% over the first two months of operation. Since data are limited on biochemical and chitin reactors operating in elevated and harsh winter locations, the acquired data are unique for MIW remediation. Additional Keywords: ARD, MIW, biochemical reactor, BCR, sulfate reducing bioreactor, SRB, chitorem® BCR , chitin, satellite data transmission, heavy metals remediation, passive treatment, Green Remediation

English

UAbstract:U Water treatment is often required at active and inactive mine sites to remove heavy metals and other contaminants of concern (COCs) prior to discharging water. Traditional water treatment can be expensive and impractical at some sites due to excessive energy, manual labor, and operations and maintenance (O&M) requirements. Passive treatment has emerged as a way to treat such waters inexpensively by requiring minimal amounts of O&M and little to no external energy. One form of passive treatment technology that has been developed over the last twenty years is the biochemical reactor (BCR), also known as a sulfate reducing bioreactor (SRBR). As its name would suggest, a BCR treats water by way of biological and chemical reactions. A BCR uses a combination of organic substrate materials and microbial activity to remove heavy metals, remove other COCs, and stabilize pH in mining influenced water (MIW). Additionally, a BCR adds hardness, alkalinity, and organic matter to the MIW, all of which are beneficial to overall water quality and aquatic life.

A spatial risk assessment methodology to support the remediation of contaminated land

When soil and groundwater contaminations occur over large areas, remediation measures should be spatially prioritised on the basis of the risk posed to human health and in compliance with technological and budget constraints. Within this scope, the application of human health risk assessment algorithms in a spatially resolved environment raises a number of methodological and technical complexities. In this paper, a methodology is proposed and applied in a case study to support the entire formulation process of remediation plans, encompassing hazard assessment, exposure assessment, risk characterisation, uncertainty assessment and allocation of risk reduction measures. In the hazard assessment, it supports the selection of Contaminants of Concern (CoC) with regard to both their average concentrations and peak concentrations, i.e. hot spots. In the exposure assessment, it provides a zoning of the site based on the geostatistical mapping of contaminant. In the risk characterisation, it generates vector maps of Risk Factors on the basis of the risk posed by multiple substances and allows the interrogation of most relevant CoC and exposure pathways for each zone of the site. It also supports the Monte Carlo based probabilistic estimation of the Risk Factors and generates maps of the associated uncertainty. In the risk reduction phase, it supports the formulation of remediation plans based on the stepwise spatial allocation of remediation interventions and the on-time simulation of risk reduction performances. The application of this methodology is fully supported by an easy-to-use and customized Geographical Information System and does not require high expertise for interpretation. The proposed methodology is the core module of a Decision Support System (DSS) that was implemented in the DESYRE software aimed at supporting the risk-based remediation of megasites.

Research in Support of Remediation Activities at the Savannah River Site

The USDOE Savannah River Site (SRS), an 803‐km2 (310‐mile2) facility located south of Aiken, SC on the upper Atlantic Coastal Plain and bounded to the west by the Savannah River, was established in the 1950s for the production and refinement of nuclear materials. To fulfill this mission during the past 50 years SRS has operated five nuclear reactors, two large chemical separation areas, waste disposal facilities (landfills, waste ponds, waste tanks, and waste stabilization), and a large number of research and logistics support facilities. Contaminants of concern (COC) resulting from site operations include chlorinated solvents, radionuclides, metals, and metalloids, often found as complex mixtures that greatly complicate remediation efforts when compared with civilian industries. The objective of this article is to provide a description of the lithology and hydrostatigraphy of the SRS, as well as a brief history of site operations and research activities as a preface to the current special section of Vadose Zone Journal (VZJ) dedicated to SRS, focusing mainly on issues that are unique to the USDOE complex. Contributions to the special section reflect a diverse range of topics, from hydrologic tracer experiments conducted both within the vadose and saturated zones to studies specifically aimed at identifying geochemical processes controlling the migration and partitioning of specific contaminants (e.g., TCE, 137Cs, U, and Pu) in SRS subsurface environments. Addressing the diverse environmental challenges of the SRS provides a unique opportunity to conduct both fundamental and applied research across a range of experimental scales. Hence, the SRS has been a pioneering force in several areas of environmental research and remediation, often through active interdisciplinary collaboration with researchers from other USDOE facilities, academic and federal institutions, and commercial entities.

RISK ASSESSMENT OF GREAT HORNED OWLS (BUBO VIRGINIANUS) EXPOSED TO POLYCHLORINATED BIPHENYLS AND DDT ALONG THE KALAMAZOO RIVER, MICHIGAN, USA

The great horned owl (GHO; Bubo virginianus) was used in a multiple lines of evidence study of polychlorinated biphenyls (PCBs) and p,p'-dichlorodiphenyltrichloroethane (DDT) exposures at the Kalamazoo River Superfund Site (KRSS), Kalamazoo, Michigan, USA. The study examined risks from total PCBs, including 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQWorld Health Organization [WHO]-Avian Toxicity Equivalency Factor [TEF]), and total DDTs (sum of DDT, dichlorodiphenyldichloroethylene [DDE], and dichlorodiphenyldichloroethane [DDD]; sigmaDDT) by measuring concentrations in eggs and nestling blood plasma in two regions of the KRSS (upper, lower) and an upstream reference area (RA). An ecological risk assessment compared concentrations of the contaminants of concern (COCs) in eggs or plasma to toxicity reference values. Productivity and relative abundance measures for KRSS GHOs were compared with other GHO populations. Egg shell thickness was measured to assess effects of p,p'-DDE. The concentrations of PCBs in eggs were as great as 4.7 x 10(2) and 4.0 x 10(4) ng PCB/g, wet weight at the RA and combined KRSS sites, respectively. Egg TEQ(WHO-Avian) calculated from aryl hydrocarbon receptor-active PCB congeners and WHO TEFs ranged to 8.0 and 1.9 x 10(2) pg TEQ(WHO-Avian)/g, (wet wt) at the RA and combined KRSS, respectively. Egg sigmaDDT concentrations were as great as 4.2 x 10(2) and 5.0 x 10(3) ng sigmaDDT/g (wet wt) at the RA and combined KRSS, respectively. Hazard quotients (HQs) for the upper 95% confidence interval (UCI) (geometric mean) and least observable adverse effect concentration (LOAEC) for COCs in eggs were < or = 1.0 for all sites. Hazard quotient values based on the no observable adverse effect concentration (NOAEC) 95% UCI in eggs were < or = 1.0, except at the LKRSS (PCB HQ = 3.1; TEQ(WHO-Avian) HQ = 1.3). Productivity and relative abundance measures indicated no population level effects in the UKRSS.

Full‐Scale Removal of DNAPL Constituents Using Steam‐Enhanced Extraction and Electrical Resistance Heating

AbstractIn 2003, the United States Department of Energy completed a full‐scale non–aqueous phase liquid (NAPL) remediation of Area A of the Northeast Site at the Young‐Rainey STAR Center, Largo, Florida. Area A covered an area of 930 m2 (10,000 square feet) and extended to a depth of 10.7 m (35 feet), representing a total cleanup volume of 9930 m3 (12,960 cubic yards). The site was contaminated with ∼2500 kg (5500 lb) of NAPL constituents such as trichloroethylene, cis‐1,2‐dichloroethylene, methylene chloride, toluene, and petroleum hydrocarbons. The site consists of a fine‐grained sand aquifer underlain by a Hawthorn clay at 9 m (30 feet) depth. The upper 1.5 m (5 feet) of this clay formed part of the remediation volume, as dense non–aqueous phase liquid was present in this layer. The site was remediated using a combination of steam‐enhanced extraction and electrical resistance heating. Operations lasted 4.5 months. The site was heated to the target temperatures within 6 weeks, at which time the mass removal rate increased more than 1000‐fold. After the target volume had been heated to or near boiling temperatures, pressure cycles were used to increase the mass removal rates, until a final phase of diminishing returns was reached. Postoperational sampling of soil and ground water at randomly selected locations showed the concentrations of all contaminants of concern (COC) to be well below the remedial goals. The majority of the ground water samples were below maximum contaminant level (MCL) for all the COC. The estimate of volatile organic contaminant (VOC) mass removed from the site (1130 kg = 2500 lb) agreed well with the estimate of VOC present before operation (1170 kg = 2580 lb). The postoperational sampling showed that ∼0.5 kg (1 pound) of VOCs remained in the remedial volume, and showed remedial efficiencies of between 99.85% and 99.99% for the four chemicals of concern. Since the postoperational sampling shows all concentrations to be below or close to ground water MCLs, the thermal remedy may be satisfactory for site closure without a polishing phase.

Modeling Volatile Chemical Transport, Biodecay, and Emission to Indoor Air

AbstractA model is presented for estimating vapor concentrations in buildings because of volatilization from soil contaminated by non‐ aqueous phase liquids (NAPL) or from dissolved contaminants in ground water. The model considers source depletion, diffusive‐ dispersive transport of the contaminant of concern (COC) and of oxygen and oxygen‐limited COC biodecay. Diffusive‐advective transport through foundations and vapor losses caused by foundation cross‐flow are considered. Competitive oxygen use by various species is assumed to be proportional to the product of the average dissolved‐phase species concentration and a biopreference factor. Laboratory and field data indicate the biopreference factor to be proportional to the organic carbon partition coefficient for the fuel hydrocarbons studied. Predicted indoor air concentrations were sensitive to soil type and subbase permeability. Lower concentrations were predicted for buildings with shallow foundations caused by flushing of contaminants by cross‐flow. NAPL source depletion had a large impact on average exposure concentration. Barometric pumping had a minor effect on indoor air emissions for the conditions studied. Risk‐based soil cleanup levels were much lower when biodecay was considered because of the existence of a threshold source concentration below which no emissions occur. Computed cleanup levels at NAPL‐contaminated sites were strongly dependent on total petroleum hydrocarbon (TPH) content and COC soil concentration. The model was applied to two field sites with gasoline‐contaminated ground water. Confidence limits of predicted indoor air concentrations spanned approximately two orders of magnitude considering uncertainty in model parameters. Measured contaminant concentrations in indoor air were within model‐predicted confidence limits.

Ecological and human health risks at an outdoor firing range

AbstractThis is the first report in the refereed literature of a quantitative ecological and human health risk assessment at an outdoor recreational shooting range. Contaminants of concern (COC) included lead, other metals, and polycyclic aromatic hydrocarbons (PAH) associated with the clay targets on the shotgun range. Ecological receptors included raptors, deer, foxes, birds, and small mammals. The risk associated with potential incidental ingestion of lead shot by mammals was estimated for the first time. With the exception of lead, risks were minimal to all ecological receptors from all COC acting through all exposure pathways. Lead posed minimal risk to raptors, foxes, or deer. Lead in dietary items posed a small risk to individual birds. The only substantive risk was to individual small mammals and gritingesting birds from the incidental ingestion of lead shot within the shotfall zone at the trap and skeet range. Although effects associated with lead ingestion may occur at the level of individual organisms, ecological impacts are not expected at the population, community, or ecosystem level. This is because density‐dependent compensation mechanisms would likely offset any site‐related loss of a few individuals that might occur. Human receptors included shooters, range workers, and trespassers. Cancer risks to all receptors from all COC via all exposure pathways were less than 10−4, generally considered an acceptable upper bound excess lifetime cancer risk to an individual. The only noncarcinogenic risk of HQ &gt; 1 was associated with inhalation of copper by those engaged in the voluntary activity of shooting. Two approaches were taken to modeling blood lead in children associated with intermittent exposure. Under the most likely exposure scenario, the mean blood lead level of trespassing children was approx. 2 μg/dL, with less than 1% of children exceeding the 10‐μg/dL level of concern. Higher blood lead levels could be possible if children were to trespass in off‐limit areas of the shooting range.

Biological responses of the sea urchin, Arbacia punctulata, to lead contamination for an estuarine ecological risk assessment

An estuarine ecological risk assessment for thePortsmouth Naval Shipyard (PNS) Kittery, ME, wasconducted utilizing the U.S. EPA's Framework forEcological Risk Assessment (ERA). As part of theanalysis phase of the ERA, laboratory studies wereconducted to develop quantitative exposure-responserelationships for lead (Pb), a key contaminant ofconcern for PNS, in order to evaluate the role of Pbin the ecological stress observed near PNS, and toestimate the probability of ecological risk associatedwith Pb contamination at the site. Biological effectsof exposure to Pb via sediment or diet were evaluatedusing several life stages of the sea urchin, Arbacia punctulata. This strategy was employedbecause echinoderm species, including A.punctulata, are amenable to laboratory testing andhave been used frequently to assess the toxicity ofestuarine waters and sediments. In addition, lifestage-specific biological effects could be comparedand integrated into projections of population-levelresponses to Pb. Results indicated that adult seaurchins accumulated Pb in direct proportion toexposure medium Pb concentration, whether exposureoccurred via sediment or diet. High Pb concentrationsreduced survival and gamete production in females, buthad no effect on the viability of produced gametes. Aqueous Pb exposure concentrations that producedadverse effects on adult sea urchin survival andreproduction were also directly toxic to early lifestages. In addition to their utility for this ERA,these results have applicability for the prediction ofbiological effects or the retrospective analysis ofcausal relationships at other estuarine sites.