Measurement of lead complexation by humic acids and humic acid analogues using competitive ligand exchange.

In soil and water, metal complexation by humic substances has been demonstrated to have great importance in determining the bioavailability of many trace metals including lead. The binding of lead by humic acids has important implications for lead toxicity, and remediation. In this study we demonstrate the use of 4-(2-pyridylazo)-resorcinol (PAR) as a competitive ligand for the purposed of determining sorption isotherms for Pb on humic acids and humic acid analogs.

Sampling for silver nanoparticles in aqueous media using a rotating disk electrode: evidence for selective sampling of silver nanoparticles in the presence of ionic silver.

Amendment of a carbon paste electrode consisting of graphite and Nujol®, with a variety of organic and inorganic materials, allows direct adsorption of silver nanoparticles (AgNPs) from aqueous solution in either open or close circuit modes. The adsorbed AgNPs are detected by stripping voltammetry. Detection limits of less than 1 ppb Ag are achievable with a rotating disk system.

Paradoxical anaerobism in desert pupfish.

In order to estimate metabolic demands of desert pupfish for conservation purposes, we measured oxygen consumption in fish acclimated to the ecologically relevant temperatures of 28 or 33°C. For these experiments, we used fish derived from a refuge population of Devils Hole pupfish (Cyprinodon diabolis). Measurement of routine oxygen consumption (V̇O2,routine) revealed some 33°C-acclimated fish (10% of 295 assayed fish) periodically exhibited periods of no measurable oxygen consumption despite available ambient oxygen tensions that were above the critical PO2.

High-performance liquid chromatography method for determination of hydrogen peroxide in aqueous solution and application to simulated Martian soil and related materials.

A new method for determination of hydrogen peroxide (H2O2) is described. H2O2 reacts with iodide in the presence of ammonium molybdate and vanillic acid resulting in the formation of iodovanillic acid which is quantified by reversed-phase high-performance liquid chromatography (HPLC) and detected by UV absorption at 280 nm. The method provides a detection limit of ~0.

On-line dechlorination-hydrogenation of chlorinated paraffin mixtures using GC and GC/MS.

Chlorinated paraffins (CPs) are straight chain hydrocarbons that are produced as complex mixtures and are used as flame retardants and paint additives. These mixtures are extremely difficult to characterize using conventional chromatographic methods, as conventional gas chromatography results in unresolved complex chromatograms that preclude the identification and quantification of individual congeners or any reasonable assessment of the average carbon chain length. Carbon chain length is an important parameter for assessing physical properties and the toxicity of these materials.

Analysis of iodide and iodate in Lake Mead, Nevada using a headspace derivatization gas chromatography-mass spectrometry.

We report here a derivatization headspace method for the analysis of inorganic iodine in water. Samples from Lake Mead, the Las Vegas Wash, and from Las Vegas tap water were examined. Lake Mead and the Las Vegas Wash contained a mixture of both iodide and iodate.

Characterization of the lignin signature in Lake Mead, NV, sediment: comparison of on-line flash chemopyrolysis (600 degrees C) and off-line chemolysis (250 degrees C).

The distribution of lignin in sediment is a useful tool for tracing the transport of land-derived organic matter in an aquatic environment. Tetramethylammonium hydroxide (TMAH) flash chemopyrolysis, or chemolysis followed by GC-MS analysis can be used for evaluating the origin of organic carbon in sediments. TMAH chemopyrolysis or chemolysis of organic matter produces a myriad of semi-volatile products.

Chemical and colloidal analyses of natural seep water collected from the exploratory studies facility inside Yucca Mountain, Nevada, USA.

Yucca Mountain is being considered as a geological repository for the USA's spent nuclear fuel and high-level nuclear waste. Numerous groundwater seeps appeared during March 2005 within the exploratory studies facility (ESF), a tunnel excavated in the mountain. Because of the relevance to radionuclide transport and unsaturated zone-modeling studies, we analyzed the seep samples for major anions and cations, rare earth elements, and colloids.

A high performance liquid chromatography method for determination of gas-phase hydrogen peroxide in ambient air using Fenton's chemistry.

A new method for determination of hydrogen peroxide in atmospheric samples is described. Cryogenically collected H2O2 is reacted with sodium salicylate in the presence of Fe(2+) to produce dihydroxybenzoate, which is separated from the reaction mixture by high performance liquid chromatography and detected by UV absorption. Measurements of atmospheric H2O2 were conducted in Las Vegas, NV from June 1999 to December 1999 to evaluate and characterize the method.