Combinatorial parameter space as an empirical tool for predicting water chemistry: Fe(II) oxidation across a watershed.

Fe(II) oxidation kinetics in surface waters are a complex function of the concentration of several dissolved species that vary geographically and temporally across watersheds. This work reports an empirical, combinatorial investigation of Fe(II) oxidation that simultaneously evaluated these variations across the pH, Fe(II), PO₄³⁻, Cl⁻, Br(-), CO₃²⁻, and natural organic matter (NOM) axes. The work assayed the effects of independent and dependent variables through application of a novel experimental design that varied Fe(II), PO₄³⁻, Cl⁻, Br⁻, and CO₃²⁻ along the pH axis.

Short-term Fe cycling during Fe(II) oxidation: exploring joint oxidation and precipitation with a combinatorial system.

The net oxidation of Fe(II)aq by dioxygen initiates a suite of reactions including the oxidation of multiple Fe(II) complexes, generation of secondary oxidants, Fe(III) reduction, and precipitation of insoluble products. This work reports application of a multifactorial strategy to describe the oxidation of Fe(II) under conditions that correspond to those found where Fe(II)-rich groundwaters mix rapidly with overlying oxygenated waters. Response surfaces were constructed describing the relationship of the net oxidation process with mixtures of the common ligands chloride (Cl-), bromide (Br-), total carbonate (CO3(2-)), Fe(II), and Suwannee River natural organic matter (SRNOM) at pH 8.

Multivariate examination of Fe(II)/Fe(III) cycling and consequent hydroxyl radical generation.

The introduction of Fe(II)(aq) into aerated solutions resulted in net Fe(II) oxidation with concomitant, rapid Fe(II)/Fe(IIII) cycling and concurrent generation of reactive oxygen species. The effect of mixtures of naturally occurring solutes on Fe(II)/Fe(III) cycling and the concurrent oxidation of dissolved organics is reported. The experimental strategy was based on a multivariate, microscale, high-throughput approach for evaluating the effect of covarying concentrations of bromide, iodide, Suwannee River natural organic matter (SRNOM), chloride, and total carbonate species.

Transfer of gold nanoparticles from the water column to the estuarine food web.

Within the next five years the manufacture of large quantities of nanomaterials may lead to unintended contamination of terrestrial and aquatic ecosystems. The unique physical, chemical and electronic properties of nanomaterials allow new modes of interaction with environmental systems that can have unexpected impacts. Here, we show that gold nanorods can readily pass from the water column to the marine food web in three laboratory-constructed estuarine mesocosms containing sea water, sediment, sea grass, microbes, biofilms, snails, clams, shrimp and fish.

Use of multiparametric techniques to quantify the effects of naturally occurring ligands on the kinetics of Fe(II) oxidation.

A multifactorial experimental design was employed to quantify and rank the effects of a series of ligands on the rate of Fe(II) (18 microM) oxidation in a system containing chloride, sulfate, carbonate/bicarbonate, fluoride, and natural organic matter (NOM) at pH 8.34 +/- 0.13.

Method for the determination of sub-ppm concentrations of perfluoroalkylsulfonate anions in water.

The determination of sub-ppm concentrations of aqueous perfluoroalkylsulfonate (PFSt) anions, including perfluorooctylsulfonate (PFOS), has been accomplished with a relatively simple mass spectrometric procedure that does not require extraction of the analytes into an organic solvent or a chromatographic separation prior to injection into the negative-ion electrospray ionization mass spectrometer. Sample pretreatment was minimized and consisted of dilution of the aqueous samples of groundwater, surface water, tap water, and distilled water with acetonitrile, addition of dodecylsulfate (DDS) as an internal standard, and, in some cases, addition of known amounts of perfluorobutylsulfonate (PFBS) or PFOS for standard-addition experiments. The linear-response range for PFOS is 25.