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Old Forge, PA, United States

Li M.,Rice University | Conlon P.,Environmental Standards Inc. | Fiorenza S.,British Petroleum | Vitale R.J.,Environmental Standards Inc. | Alvarez P.J.J.,Rice University
Ground Water Monitoring and Remediation | Year: 2011

An innovative micro-extraction of aqueous samples coupled with gas chromatography/mass spectrometry in selected ion-monitoring mode (GC/MS-SIM) was developed to selectively analyze for 1,4-dioxane with low part-per-billion detection sensitivity. Recoveries of 1,4-dioxane ranged from 93% to 117% for both spiked laboratory reagent water and natural groundwater matrices, the later having elevated organic carbon content (8.34 ± 0.31 mg/L as total organic carbon). We observed that freezing the aqueous sample along with the extraction solvent enhanced the extraction efficiency, minimized physical interferences, and improved sensitivity resulting in a limit of detection for 1,4-dioxane to approximately 1.6 μg/L. This method substantially reduces the labor, time, reagents and cost, and uses instruments that are commonly found in analytical laboratories. This method requires a relatively small sample volume (200 μL), and can be considered a green analytical method as it minimizes the use of toxic solvents and the associated laboratory wastes. © 2011, The Author(s). Ground Water Monitoring & Remediation © 2011, National Ground Water Association. Source

Markwiese J.T.,Environmental Standards Inc. | Rogers W.J.,Tennessee Valley Authority | Carriker N.E.,Tennessee Valley Authority | Thal D.I.,Environmental Standards Inc. | And 5 more authors.
Environmental Monitoring and Assessment | Year: 2014

The weathering of coal combustion products (CCPs) in a lotic environment was assessed following the Tennessee Valley Authority (Kingston, TN) fly ash release of 2008 into surrounding rivers. Sampled materials included stockpiled ash and sediment collected from 180 to 880 days following the release. Total recoverable concentrations of heavy metals and metalloids in sediment were measured, and percent ash was estimated visually or quantified by particle counts. Arsenic and selenium in sediment were positively correlated with percent ash. For samples collected 180 days after the release, total concentrations of trace elements downstream of the release were greater than reference levels but less than concentrations measured in stockpiled ash. Total concentrations of trace elements remained elevated in ash-laden sediment after almost 2.5 years. A sequential extraction procedure (SEP) was used to speciate selected fractions of arsenic, copper, lead, nickel, and selenium in decreasing order of bioavailability. Concentrations of trace elements in sequentially extracted fractions were one to two orders of magnitude lower than total recoverable trace elements. The bulk of sequentially extractable trace elements was associated with iron-manganese oxides, the least bioavailable fraction of those measured. By 780 days, trace element concentrations in the SEP fractions approached reference concentrations in the more bioavailable water soluble, ion exchangeable, and carbonate-bound fractions. For each trace element, the percentage composition of the bioavailable fractions relative to the total concentration was calculated. These SEP indices were summed and shown to significantly decrease over time. These results document the natural attenuation of leachable trace elements in CCPs in river sediment as a result of the loss of bioavailable trace elements over time. © 2014 Springer International Publishing. Source

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