Primary Contaminant Of Concern Research Articles

Improved assessment and performance monitoring of a biowall at a chlorinated solvent site using high-resolution passive sampling

This study contrasts the use of high-resolution passive sampling and traditional groundwater monitoring wells (GWMW) to characterize a chlorinated solvent site and assess the effectiveness of a biowall (mulch, compost and sand) that was installed to remediate trichloroethene (TCE), the primary contaminant of concern. High-resolution passive profilers (HRPPs) were direct driven hydraulically upgradient, within, and hydraulically downgradient of the biowall and in close proximity to existing GWMWs. Compared with hydraulically upgradient locations, the biowall was highly reducing, there were higher densities of bacteria/genes capable of reductive dechlorination, and TCE was being reductively transformed, but not completely, as cis-1,2-dichloroethene (cis-DCE) was detected within and hydraulically downgradient of the biowall. However, based on the high-resolution data, there were a number of important findings which were not discoverable using data from GWMWs alone. Data from the HRPPs indicate that the biowall was completely transforming TCE to ethene (C2H4) except within a high velocity interval, where the concentrations were reduced, but breakthrough of cis-DCE was apparent. Hydraulically upgradient of the biowall, concentrations of TCE increased with depth where a very low permeability zone exists that will likely remain as a long-term source. In addition, although low concentrations of cis-DCE were present downgradient of the biowall, surfacing into a downgradient stream was not detected. This study demonstrates the advantages of high-resolution passive sampling of aquifers to assess the performance of remediation techniques compared to traditional methods such as GWMWs.

Profiling microbial community structures and functions in bioremediation strategies for treating 1,4-dioxane-contaminated groundwater

Microbial community compositions and functional profiles were analyzed in microcosms established using aquifer materials from a former automobile factory site, where 1,4-dioxane was identified as the primary contaminant of concern. Propane or oxygen biostimulation resulted in limited 1,4-dioxane degradation, which was markedly enhanced with the addition of nutrients, resulting in abundant Mycobacterium and Methyloversatilis taxa and high expressions of propane monooxygenase gene, prmA. In bioaugmented treatments, Pseudonocardia dioxanivorans CB1190 or Rhodococcus ruber ENV425 strains dominated immediately after augmentation and degraded 1,4-dioxane rapidly which was consistent with increased representation of xenobiotic and lipid metabolism-related functions. Although the bioaugmented microbes decreased due to insufficient growth substrates and microbial competition, they did continue to degrade 1,4-dioxane, presumably by indigenous propanotrophic and heterotrophic bacteria, inducing similar community structures across bioaugmentation conditions. In various treatments, functional redundancy acted as buffer capacity to ensure a stable microbiome, drove the restoration of the structure and microbial functions to original levels, and induced the decoupling between basic metabolic functions and taxonomy. The results of this study provided valuable information for design and decision-making for ex-situ bioreactors and in-situ bioremediation applications. A metagenomics-based understanding of the treatment process will enable efficient and accurate adjustments when encountering unexpected issues in bioremediation.

Occurrence and source identification of perfluoroalkyl acids (PFAAs) in the Metedeconk River Watershed, New Jersey.

The Brick Township Municipal Utilities Authority (BTMUA), which relies on the Metedeconk River as its primary source of water supply, initiated a perfluoroalkyl acid (PFAA) source trackdown study in collaboration with the New Jersey Department of Environmental Protection (NJDEP) after discovering that the concentration of one PFAA, perfluorooctanoic acid (PFOA), was elevated at their raw surface water intake. Water samples were collected over eight sampling events between September 2011 and July 2014. Samples included surface water, groundwater, stormwater, sanitary sewer water, and commercial/industrial process water. Each sample was analyzed for ten PFAAs. Results from a set of samples collected from the 80km2 South Branch Metedeconk River watershed directed the focus of this study to a 7.5-km2 area of interest. Within this area, a high concentration of PFAA contamination was documented in a localized zone. Subsequent groundwater sampling led to the identification of a plume of groundwater contamination emanating from an industrial/business park. The suspected source of PFAA detected in the river and drinking water intake was identified to a small industrial facility that used materials containing PFOA. Groundwater PFOA concentrations as high as 70,000ng/L were found in samples taken within 200m of the parcel and surface water concentrations as high as 130ng/L were observed in the river. While various PFAAs were detected in the samples, particularly in groundwater samples, PFOA was identified as the primary contaminant of concern with respect to the river and the BTMUA water supply.

Effectiveness of a sediment time critical removal action-PCB reduction in fish tissue, surface water, and sediment via wet excavation.

Documenting successful remediation of polychlorinated biphenyl (PCB)-contaminated sediments is limited; potentially due to inadequate monitoring methods, complexities associated with the environment, and selected remedial techniques. At some sites, absence of appropriate baseline and postremoval monitoring limits proper evaluation of remedial efficacy. Accurate interpretation of interactions between media, space, time, species, lipid content, and remedial technique requires robust study design and data. This article presents baseline and postremoval data documenting reduced PCB concentrations in fish tissue, surface water, and sediment in response to the US Environmental Protection Agency (USEPA) time-critical removal action (TCRA) that was conducted at the former Bryant Mill Pond (BMP) on Portage Creek in Kalamazoo, Michigan. The BMP is part of an operable unit (OU) within the Allied Paper, Inc./Portage Creek/Kalamazoo River Superfund Site. PCBs discharged to the creek as a byproduct of carbonless copy paper recycling are the primary contaminant of concern. Paper waste residuals commonly appear as gray to light gray clays in river sediments and floodplain soils. The cleanup criterion was 10 mg/kg, with a residual PCB concentration goal of 1 mg/kg. Because the PCB-containing waste is (generally) associated with readily visible light gray clay, excavation of all visibly contaminated current or formerly impounded sediment served as a surrogate for the cleanup criteria and goal. Sediment was wet excavated and backfilled after diversion of the creek. After confirmation that PCB concentrations met cleanup criteria, the stream was diverted to the excavated side, and excavation and backfilling were completed. Overall, 146000 cubic yards of material including PCB-contaminated sediments were removed from the BMP. The long-term monitoring (LTM) program implemented by the Michigan Department of Environmental Quality (MDEQ), and historic data from a variety of sources (federal, state, and local agencies and responsible parties) provided data demonstrating TCRA effectiveness. Before TCRA, surface sediment PCB concentration in instream and formerly inundated sediment combined was 83 mg/kg (with a maximum of 700 mg/kg). Instream sediments that are more representative of fish exposures had a pre-TCRA surface weighted average concentration (SWAC) of 27 mg/kg. The post-TCRA SWAC for instream and floodplain sediments combined was 0.26 mg/kg. Average surface water concentrations at the downstream end of the BMP were reduced from 0.11 µg/L pre-TCRA to 0.0025 µg/L post-TCRA. Tissue samples for adult carp fillets decreased from 4 mg/kg pre-TCRA to 0.26 mg/kg post-TCRA; whole body white suckers from 3 mg/kg pre-TCRA to 0.1 mg/kg post-TCRA; whole body channel catfish from 39 mg/kg-L pre-TCRA to 2.6 mg/kg-L post-TCRA. Concentrations of PCBs in 2 species of resident fish (carp and white suckers), caged channel catfish, surface water, and sediment were reduced by over 1 order of magnitude within 1 year of completion, substantively accelerating natural recovery processes. A slight increase in PCB concentration was observed in both whole body suckers and adult carp fillets in the second monitoring period post-TCRA; however, these concentrations are still near an order of magnitude less than pre-TCRA concentrations and appear to be currently stable or on a slight downward trend.

The unbearable fuzziness of being sustainable: an integrated, fuzzy logic-based aquifer health index

We introduce a groundwater sustainability index offering a novel combination of features. It is holistic in the sense that it incorporates both water quantity and water quality indicators. The former employs the signal-to-noise ratio of long-term trends estimated via robust regression; the latter uses concentration of the primary contaminant of concern. A fuzzy inference system integrates these unlike metrics. The system also explicitly encodes expert knowledge and stakeholder values, and directly acknowledges subjectivity in environmental condition “grading,” through the use of linguistic rules and fuzzy sets, respectively. The fuzzy rule base is constructed such that poor environmental conditions captured by one measure are not hidden by good performance in another. A standard Mamdani (max–min) inference engine is used with centroid defuzzification. The outcome is an intuitively accessible index ranging from 0 to 100. The method is demonstrated using examples from the Abbotsford-Sumas aquifer, an important and managerially challenging transboundary (Canada–US) water resource.Editor D. Koutsoyiannis; Associate editor E. RozosCitation Fleming, S.W., Wong, C., and Graham, G., 2014. The unbearable fuzziness of being sustainable: an integrated, fuzzy logic-based aquifer health index. Hydrological Sciences Journal, 59 (6), 1154–1166. http://dx.doi.org/10.1080/02626667.2014.907496

Characterizing long-term contaminant mass discharge and the relationship between reductions in discharge and reductions in mass for DNAPL source areas.

The objective of this study was to characterize the temporal behavior of contaminant mass discharge, and the relationship between reductions in contaminant mass discharge and reductions in contaminant mass, for a very heterogeneous, highly contaminated source-zone field site. Trichloroethene is the primary contaminant of concern, and several lines of evidence indicate the presence of organic liquid in the subsurface. The site is undergoing groundwater extraction for source control, and contaminant mass discharge has been monitored since system startup. The results show a significant reduction in contaminant mass discharge with time, decreasing from approximately 1 to 0.15 kg/d over five years. Two methods were used to estimate the mass of contaminant present in the source area at the initiation of the remediation project. One was based on a comparison of two sets of core data, collected 3.5 years apart, which suggests that a significant (~80%) reduction in aggregate sediment-phase TCE concentrations occurred between sampling events. The second method was based on fitting the temporal contaminant mass discharge data with a simple exponential source-depletion function. Relatively similar estimates, 784 and 993 kg, respectively, were obtained with the two methods. These data were used to characterize the relationship between reductions in contaminant mass discharge (CMDR) and reductions in contaminant mass (MR). The observed curvilinear relationship exhibits a reduction in contaminant mass discharge essentially immediately upon the initiation of mass reduction. This behavior is consistent with a system wherein significant quantities of mass are present in hydraulically poorly accessible domains for which mass removal is influenced by rate-limited mass transfer. The results obtained from the present study are compared to those obtained from other field studies to evaluate the impact of system properties and conditions on mass-discharge and mass-removal behavior. The results indicate that factors such as domain scale, hydraulic-gradient status (induced or natural), and flushing-solution composition had insignificant impact on the CMDR-MR profiles and thus on underlying mass-removal behavior. Conversely, source-zone age, through its impact on contaminant distribution and accessibility, was implicated as a critical factor influencing the nature of the CMDR-MR relationship.

Selenium:mercury molar ratios in fish from the Savannah River: implications for risk management

The risk to humans from contaminants in fish is dealt with by issuing consumption advisories, which are devised from consumption patterns, contaminant levels, and toxicity of those contaminants. The primary contaminant of concern in fish is mercury, and recently it has been suggested that the protective effects of selenium on mercury toxicity should be considered in risk management. The relationships between mercury, fish species and fish size, and selenium:mercury (Se:Hg) molar ratios were examined for freshwater fish from the Savannah River. The data indicated: (1) significant variation in Se:Hg molar ratios among and within species, (2) mean selenium molar ratios for the 11 species were negatively correlated with mean mercury levels and mean fish length, (3) greater variation in individual variances within species than the variation in mean ratios among species, (4) some species with high mean ratios had individuals with ratios below 1, and (5) even the species with the highest mean ratios had some individuals close to a molar ratio of one. These data suggest that the great variability of the Se:Hg molar ratios within a species results in the ratios being unpredictable. That is, knowing the mean Se:Hg molar ratio for a given species does not predict the ratios of individuals, or thus the protectiveness of selenium on mercury toxicity.

Impact of In Situ Chemical Oxidation on Contaminant Mass Discharge: Linking Source-Zone and Plume-Scale Characterizations of Remediation Performance

A large-scale permanganate-based in situ chemical oxidation (ISCO) effort has been conducted over the past ten years at a federal Superfund site in Tucson, AZ, for which trichloroethene (TCE) is the primary contaminant of concern. Remediation performance was assessed by examining the impact of treatment on contaminant mass discharge, an approach that has been used for only a very few prior ISCO projects. Contaminant mass discharge tests were conducted before and after permanganate injection to measure the impact at the source-zone scale. The results indicate that ISCO caused a significant reduction in mass discharge (approximately 75%). The standard approach of characterizing discharge at the source-zone scale was supplemented with additional characterization at the plume scale, which was evaluated by examining the change in contaminant mass discharge associated with the pump-and-treat system. The integrated contaminant mass discharge decreased by approximately 70%, consistent with the source-zone-scale measurements. The integrated mass discharge rebounded from 0.1 to 0.2 kg/d within one year after cessation of permanganate injections, after which it has been stable for several years. Collection of the integrated contaminant mass discharge data throughout the ISCO treatment period provided a high-resolution, real-time analysis of the site-wide impact of ISCO, thereby linking source-zone remediation to impacts on overall risk. The results indicate that ISCO was successful in reducing contaminant mass discharge at this site, which comprises a highly heterogeneous subsurface environment. Analysis of TCE sediment concentration data for core material collected before and after ISCO supports the hypothesis that the remaining mass discharge is associated in part with poorly accessible contaminant mass residing within lower-permeability zones.

Seven‐year performance evaluation of a permeable reactive barrier

AbstractIn June and July 2001, the Massachusetts Department of Environmental Protection (MassDEP) installed a permeable reactive barrier (PRB) to treat a groundwater plume of chlorinated solvents migrating from an electronics manufacturer in Needham, Massachusetts, toward the Town of Wellesley's Rosemary Valley wellfield. The primary contaminant of concern at the site is trichloroethene (TCE), which at the time had a maximum average concentration of approximately 300 micrograms per liter directly upgradient of the PRB. The PRB is composed of a mix of granular zero‐valent iron (ZVI) filings and sand with a pure‐iron thickness design along its length between 0.5 and 1.7 feet. The PRB was designed to intercept the entire overburden plume; a previous study had indicated that the contaminant flux in the bedrock was negligible. Groundwater samples have been collected from monitoring wells upgradient and downgradient of the PRB on a quarterly basis since installation of the PRB. Inorganic parameters, such as oxidation/reduction potential, dissolved oxygen, and pH, are also measured to determine stabilization during the sampling process. Review of the analytical data indicates that the PRB is significantly reducing TCE concentrations along its length. However, in two discrete locations, TCE concentrations show little decrease in the downgradient monitoring wells, particularly in the deep overburden. Data available for review include the organic and inorganic analytical data, slug test results from nearby bedrock and overburden wells, and upgradient and downgradient groundwater‐level information. These data aid in refining the conceptual site model for the PRB, evaluating its performance, and provide clues as to the reasons for the PRB's underperformance in certain locations. © 2008 Wiley Periodicals, Inc.

Promoting the Biological Oxidation of Reduced Sulphur Compounds by pH Adjustment in a High Temperature Membrane Bioreactor Treating Kraft Pulp Mill Foul Condensate

Abstract Over 99% of the reduced sulphur compounds (RSC) contained in a synthetic foul evaporator condensate were removed during treatment using a high temperature membrane bioreactor (MBR). At a neutral pH, the removal of the RSC was entirely due to stripping by the aeration system. It was possible to reduce the amount of RSC that was stripped to the atmosphere by promoting the biological oxidation of RSC through pH adjustment. A pH of less than approximately 4.5 was required to establish biological oxidation of RSC in the MBR. However, even at a pH of 3, which has been reported by others to be the optimal pH for the growth of thermophilic sulphur-oxidizing microorganisms, biological oxidation accounted for only approximately 50% of the RSC removed during treatment. The removal of the remaining 50% of the RSC removed during treatment was still due to stripping by the aeration system. The results further suggested that the long-term stability of a high temperature MBR operated at a low pH is questionable. In addition, the biological oxidation of methanol, which is considered to be the primary contaminant of concern contained in evaporator condensate, was significantly inhibited at a pH of less than approximately 4.5. Consequently, the simultaneous biological removal of methanol and RSC from foul evaporator condensate using a high temperature MBR was concluded to be impractical.

Sampling sediment on a complex site : Nocera, J J; Matthews, G P; Simmons, T M Civ Engng, N YV63, N3, March 1993, P54–56

This article discusses how cadmium, lead, cobalt and nickel are the culprits at the former Marathon Battery Superfund site in Cold Spring, N.Y., spread throughout 80 acres that range from upland and marshes to coves and open water of the Hudson River. Remediation will involve dredging and excavation of contaminated sediments, fixation, and off-site disposal in a permitted landfill. Design of the remediation required reliable data that were obtained by extensive field sampling plus laboratory and research programs. For 27 years, Marathon had discharged process wastewater directly into a nearby marsh and through an outfall pipe near Cold Spring Pier, contaminating the area through precipitation of metals and settling of metal hydroxides. The area, about 50 mi north of New York City, was designated as a Superfund site by EPA, which delegated project administration to the Kansas City (Mo.) District of the Army Corps of Engineers. Early remedial investigations/feasibility studies identified cadmium as the primary contaminant of concern. When the Corps contracted Malcolm Pirnie, Inc. of White Plains, N.Y. to complete the remedial design, new studies were required to more precisely identify the limits of remediation. Malcolm Pirnie engineers looked at site features and, with the Corps, experimented with samplingmore » methods and tools in upland, marsh and open-water ware as to determine appropriate methods for each area.« less