Comparison of selected non-exhaustive extraction techniques to assess PAH availability in dissimilar soils

Recently, it has become apparent that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms is inappropriate and that bioavailability of contaminants is a better measure of potential exposure. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness in determining bioavailability. In this study, phenanthrene extractability using hydroxypropyl-beta-cyclodextrin (HPCD) and desorption kinetics using butan-1-ol (BuOH) were determined in three dissimilar spiked soils. The soils were extracted after 1 d, 40 d and 80 d of soil-compound contact time. The amount of phenanthrene extracted by HPCD was compared to the rapidly desorbed fraction removed by BuOH. Further experiments using the same soils and extraction methods to assess the relative extractability of phenanthrene, pyrene and benzo(a)pyrene were conducted. Overall, the extraction methods used in this study had different extraction efficiencies. Results suggest that as compound hydrophobicity increased, BuOH became a more exhaustive extractant with respect to HPCD, especially for soils with high clay and organic matter content. These results are important as they highlight differences between two contrasting non-exhaustive extraction techniques both of which have been suggested to be appropriate in the assessment of bioavailability.     

Influence of diesel concentration on the fate of phenanthrene in soil

The aim of this study was to investigate the influence of diesel on the loss and bioavailability of soil-associated [14C]phenanthrene with time. In addition, the temporal development of phenanthrene catabolic activity and the impact of co-contaminant mixtures on the soil microflora were also assessed. With respect to compound fate, the results suggested that competitive effects between dissimilar co-contaminants did influence [14C]phenanthrene loss. Where diesel was present at a concentration of 0, 20, 200 and 2000 mg kg(-1), increased phenanthrene loss was observed with increasing diesel concentrations. In the 20,000 mg kg(-1) diesel treatment, however, a significantly higher amount of the initial [14C]activity remained after 225 days. Furthermore, initial degradation of phenanthrene in this treatment was retarded as a result of repressed phenanthrene catabolic activity. These results were complemented by a 4-fold increase in total culturable bacterial cell numbers in the 20,000 mg kg(-1) treatment when compared with the 2000 mg kg(-1) after 225 days of incubation time.     

DEMAND SIDE MANAGEMENT OF WATER IN ONTARIO MUNICIPALITIES: STATUS,PROGRESS, AND OPPORTUNITIES1

ABSTRACT: Demand side management is being used increasingly by Ontario municipalities as a way to improve the efficiency of water use, defer the costs associated with constructing new water treatment works, and minimize the environmental impacts associated with supplying water. A comprehensive survey of 153 Ontario municipalities was completed in mid‐1998. These ranged in size from small rural townships (with populations as low as 500 people) to the province's largest urban center, Metropolitan Toronto, with a population of approximately 2.5 million people. The questionnaire measured the use of six broad types of demand side measures, including water pricing and metering; municipal by‐laws (ordinances) that promote water conservation; operational and maintenance measures to reduce water losses and consumption; water‐saving plumbing fixtures and devices; public participation programs that encourage water conservation; and other measures, such as water audits. Additionally, the survey collected data on implementation barriers and opportunities. Since the last comprehensive Ontario survey, conducted in 1987 by Kreutzwiser and Fea‐gan (1989), there has been an increase in the use of basic tools such as metering and pricing, plumbing fixtures, and public participation programs. Additionally, new initiatives, such as water audits and computerized monitoring equipment, are being used. However, in many areas opportunities exist to make better use of demand side measures. Unfortunately, municipal capacity to do so often is constrained by (among other factors) limited finances, lack of political will, and public resistance. Demonstration of real cost savings to consumers, and the development of specific goals and objectives for demand side management programs, are two important steps needed to overcome these challenges.     

Applying a structured approach to industrial emission reduction

Deming's well known Plan‐Do‐Check‐Act cycle offers a systematic method for solving environmental problems. But the process is an iterative one: You may need to repeat some steps of the cycle several times before you achieve the desired goal. © 2000 John Wiley & Sons, Inc.     

Simultaneous measurements of dissolved CH<Subscript>4</Subscript> and H<Subscript>2</Subscript> in wetland soils

Biogeochemical processes in wetland soils are complex and are driven by a microbiological community that competes for resources and affects the soil chemistry. Depending on the availability of various electron acceptors, the high carbon input to wetland soils can make them important sources of methane production and emissions. There are two significant pathways for methanogenesis: acetoclastic and hydrogenotrophic methanogenesis. The hydrogenotrophic pathway is dependent on the availability of dissolved hydrogen gas (H₂), and there is significant competition for available H₂. This study presents simultaneous measurements of dissolved methane and H₂ over a 2-year period at three tidal marshes in the New Jersey Meadowlands. Methane reservoirs show a significant correlation with dissolved organic carbon, temperature, and methane emissions, whereas the H₂ concentrations measured with dialysis samplers do not show significant relationships with these field variables. Data presented in this study show that increased dissolved H₂ reservoirs in wetland soils correlate with decreased methane reservoirs, which is consistent with studies that have shown that elevated levels of H₂ inhibit methane production by inhibiting propionate fermentation, resulting in less acetate production and hence decreasing the contribution of acetoclastic methanogenesis to the overall production of methane.     

A Regional Survey of the Microbiological Water Quality along the Shoreline of the Southern California Bight

A regional survey of the microbiological water quality along the shoreline of the Southern California Bight (SCB), from Point Conception south to Ensenada, Mexico, was conducted during August, 1998, by 36 agencies under the coordination of the Southern California Coastal Water Research Project (SCCWRP). Microbiological water quality was assessed by calculating the percentage of shoreline-mile-days that exceeded bacterial indicator thresholds for total and fecal coliforms, total/fecal ratios, and enterococci. Sample sites were selected using a stratified random sampling approach, with the SCB recreational shoreline divided into six strata: high- and low-use sandy beaches, high- and low-use rocky shoreline, and perennial and ephemeral freshwater outlets. Samples were collected on a weekly basis at a total of 253 sites, beginning on August 2^nd, 1998 and continuing for five weeks. Samples were analyzed by 22 participating labs using their normal methods (multiple tube fermentation, membrane filtration, Colilert® and/or Enterolert®). All labs met testing criteria established through intercalibration exercises and quality control check samples distributed during the sampling period. Nearly 95% of the shoreline-mile days did not exceed daily and monthly bacterial indicator thresholds, demonstrating good bacteriological water quality along the SCB shoreline. Freshwater outlets, comprised mainly of storm drains, had the poorest water quality with 60% and 40% of the shoreline-miles exceeding monthly and daily thresholds, respectively. Freshwater outlets were also more likely to demonstrate exceedances by multiple indicators at a single site, and repeat exceedances at sites over the five-week period. Compared with the southern California beaches, Mexican beaches had nearly 5 times the number of exceedances for total and fecal coliforms, and nearly 8 times the number of exceedances for total/fecal ratios.     

On inferring population trends of mobile waterbirds from aerial transect surveys in variable environments

Environmental and Ecological Statistics - Monitoring waterbird populations in Australia is challenging for reasons of counting logistics, and because population aggregation and dispersion can shift...     

Treatment of poly- and perfluoroalkyl substances in groundwater using a carbon-based micro-adsorbent and ceramic membrane filtration

This article presents the results of an Environmental Security Technology Certification Program (ESTCP) demonstration conducted at Horsham Air Guard Station and the former Willow Grove Naval Reserve Station in Horsham, Pennsylvania. The ESTCP project information can be found here: https://www.serdp-estcp.org/projects/details/568c0487-f182-40c1-9d4d-9297f4bbedda/er19-5181-projcet-overview . The technology demonstrated, identified as the AquaPRS™ system, employs a carbon-based micro-adsorbent suspension to adsorb polyfluoroalkylated substance (PFAS), which is subsequently filtered using a ceramic membrane filter. A prototypical AquaPRS system was specifically designed and implemented to treat per- and PFAS-contaminated water resources at a fidelity level that could be replicated at other US Department of Defense sites. The objective of the project was to demonstrate and validate the application of the adsorption and separation treatment approach to reduce the total life-cycle cost of treating PFAS-impacted groundwater. The results of the demonstration showed that the AquaPRS technology provides an alternative to granular activated carbon (GAC) and ion exchange (IX) systems based on treatment efficacy and cost performance using lifecycle cost analyses. Pretreatment included cloth media filtration with a nominal 5 µm particulate rejection rating to remove sediment from the surface water treated during the Horsham evaluation. Prefiltration was not necessary for treating the Willow Grove groundwater due to the lower raw turbidities. The micro-adsorbent was added to the system to maintain a suspension between 1 and 50 g/L in the sorbent chamber at reaction times from 5 to 20 min. Treated effluent was separated from the sorbent slurry matrix using the ceramic membrane filter, with the slurry returned to the sorption reactor. The first study conducted at Horsham Air Guard Station demonstrated and validated the AquaPRS treatment approach using a mobile pilot system, while the second study (conducted at the former Naval Reserve Air Station at Willow Grove) provided further optimization of cost, performance, and scalability. At Horsham, 13 tests were conducted over 9 months using a dual-train pilot with each test evaluating two separate conditions. The first 10 tests were conducted with treatment systems in parallel and the remaining three were conducted in series. At Willow Grove, five tests were conducted over a 6-month period for a total of 10 individual test conditions. Three tests were performed in parallel with two operated in series. Tests conducted at Horsham evaluated the performance of the AquaPRS system at different hydraulic detention times (5–120 min), sorbent mass (10–430 g), sorbent densities (0.5–40 g/L), and flowrates (0.1–1 L/min). At Willow Grove, the range of these parameters was further narrowed with hydraulic detention times from 10 to 20 min, sorbent mass from 100 to 200 g, sorbent density from 10 to 25 g/L, and flowrate from 0.67 to 1 L/min. AquaPRS was validated by quantifying the specific adsorption rate (SAR) of various PFASs on the micro-adsorbent and comparing it to values derived for GAC and IX from the same water matrix. The costs of the three treatment systems were compared to estimate a payback period for the AquaPRS system compared to GAC and IX. At 10% breakthrough, the SAR of AquaPRS for the combined concentration of the United States Environmental Protection Agency's Third Unregulated Contaminant Monitoring Rule (UCMR3) PFASs was nearly 300 times higher compared to those treated with GAC. At 40 ng/L breakthrough for combined UCMR3 compounds, a single-stage AquaPRS system at Horsham achieved 146 µg PFAS/g sorbent SAR, while a dual-stage system at Willow Grove achieved 2128 µg PFAS/g sorbent. The AquaPRS system showed a breakeven period of 8 months compared to a similarly designed GAC system in the Horsham evaluation using the observed adsorption rates. In the Willow Grove test case, a 24–36-month breakeven period was determined for the AquaPRS technology when compared to the highest sorption rates observed among five previously tested IX resins. The AquaPRS benefits in comparison to GAC/IX include effective performance in the presence of co-contaminants, adaptability to changing conditions, limited downtime for sorbent replacement, resistance to biofouling, small footprint, and reduced disposal requirements. The lower waste production rates are due to the AquaPRS' ability to dewater the spent sorbent resulting in a waste generation of just 0.002% of the total volume of water treated. Based on the treatment efficacy and cost performance, the AquaPRS system is positioned as an alternative to GAC and IX systems.