Time-resolved fluorescence of oils and oil distillates in artificial seawater at low excitation wavelengths: Assessing the use of lifetimes to decouple oil and dissolved organic matter (DOM) fluorophores in natural waters.

It is challenging to decouple typical protein-like chromophoric dissolved organic matter (CDOM) fluorophores from oil-related fluorophores in natural waters using standard steady-state fluorescence techniques. In the present work, time-resolved florescence spectroscopy was explored as a means of differentiating between these two types of fluorophores. Fluorescence lifetimes of oil products were measured as a function of excitation and emission wavelength in artificial seawater.

The degradation of acetaldehyde in estuary waters in Southern California, USA.

Acetaldehyde plays an important role in oxidative cycles in the troposphere. Estimates of its air-water flux are important in global models. Biological degradation is believed to be the dominant loss process in water, but there have been few measurements, none in estuaries.

Optical properties of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) levels in constructed water treatment wetland systems in southern California, USA.

Many removal mechanisms in treatment wetlands involve absorption to organic matter. Optical properties and DOC levels of waters entering and exiting 4 treatment wetland systems in Orange County, Southern California, were measured to characterize the dissolved organic matter pool. Average DOC levels decreased between the inlets and outlets, except for Forge Street (FS), which increased.

Production of acetaldehyde from ethanol in coastal waters.

Interest in understanding the cycling of ethanol in the environment has grown as ethanol use as a gasoline additive has increased. The production of acetaldehyde from ethanol was measured in Southern California coastal seawater. The rate of increase of acetaldehyde was positively correlated with the rate constant for ethanol biodegradation and bacteria count and was consistent with two consecutive first-order reactions where acetaldehyde is first biologically produced from ethanol then consumed.

Optical properties of chromophoric dissolved organic matter (CDOM) in surface and pore waters adjacent to an oil well in a southern California salt marsh.

Chromophoric dissolved organic matter (CDOM) optical properties were measured in surface and pore waters as a function of depth and distance from an oil well in a southern California salt marsh. Higher fluorescence and absorbances in pore vs. surface waters suggest soil pore water is a reservoir of CDOM in the marsh.

Photoproduction of hydrogen peroxide in aqueous solution from model compounds for chromophoric dissolved organic matter (CDOM).

To explore whether quinone moieties are important in chromophoric dissolved organic matter (CDOM) photochemistry in natural waters, hydrogen peroxide (H2O2) production and associated optical property changes were measured in aqueous solutions irradiated with a Xenon lamp for CDOM model compounds (dihydroquinone, benzoquinone, anthraquinone, napthoquinone, ubiquinone, humic acid HA, fulvic acid FA). All compounds produced H2O2 with concentrations ranging from 15 to 500 μM. Production rates were higher for HA vs.

Photochemical degradation of phenanthrene as a function of natural water variables modeling freshwater to marine environments.

Photolysis rates of phenanthrene as a function of ionic strength (salinity), oxygen levels and humic acid concentrations were measured in aqueous solution over the range of conditions found in fresh to marine waters. Photolysis followed first order kinetics, with an estimated photodegradation half-life in sunlight in pure water of 10.3±0.

Diel cycles of hydrogen peroxide in marine bathing waters in Southern California, USA: in situ surf zone measurements.

Hydrogen peroxide is photochemically produced in natural waters. It has been implicated in the oxidative-induced mortality of fecal indicator bacteria (FIB), a microbial water quality measure. To assess levels and cycling of peroxide in beach waters monitored for FIB, diel studies were carried out in surf zone waters in July 2009 at Crystal Cove State Beach, Southern California, USA.

Hydrogen peroxide measurements in recreational marine bathing waters in Southern California, USA.

Hydrogen peroxide (H(2)O(2)) was measured in the surf zone at 13 bathing beaches in Southern California, USA. Summer dry season concentrations averaged 122 +/- 38 nM with beaches with tide pools having lower levels (50-90 nM). No significant differences were observed for ebb waters at a salt marsh outlet vs.

Photochemical production of hydrogen peroxide in size-fractionated Southern California coastal waters.

Hydrogen peroxide (H(2)O(2)) photochemical production was measured in bulk and size-fractionated surf zone and source waters (Orange County, California, USA). Post-irradiation (60 min; 300 W ozone-free xenon lamp), maximum H(2)O(2) concentrations were approximately 10000 nM (source) and approximately 1500 nM (surf zone). Average initial hydrogen peroxide production rates (HPPR) were higher in bulk source waters (11+/-7.

Hydrogen peroxide production in marine bathing waters: Implications for fecal indicator bacteria mortality.

Hydrogen peroxide concentrations [H(2)O(2)] have been measured over the last two decades in multiple studies in surface waters in coastal, estuarine and oceanic systems. Diurnal cycles consistent with a photochemical production process have frequently being observed, with [H(2)O(2)] increasing by two orders of magnitude over the course of the day, from low nM levels in the early morning to 10(2)nM in late afternoon. Production rates range from <10 for off-shore ocean waters to 20-60nMh(-1) for near-shore coastal and estuarine environments.

A study of fecal coliform sources at a coastal site using colored dissolved organic matter (CDOM) as a water source tracer.

Optical properties of colored dissolved organic matter (CDOM) were measured as a tracer of polluted waters in a Southern California surf-zone with consistently high levels of fecal indicator bacteria. Salinity, temperature, fecal coliform, absorbance (200-700nm) and fluorescence (lambda(excitation)=350nm; lambda(emission)=360-650nm) were measured in the creek and surf-zone during a dry and rain event. Fluorescence to absorption ratios for CDOM were used to distinguish water masses, with two distinct CDOM end-members identified as creek (flu/abs=8.

Comparison of the molecular mass and optical properties of colored dissolved organic material in two rivers and coastal waters by flow field-flow fractionation.

Colored dissolved organic material (CDOM) is an important sunlight absorbing substance affecting the optical properties of natural waters. However, little is known about its structural and optical properties mainly due to its complex matrix and the limitation of the techniques available. A comparison of two southwestern Florida rivers [the Caloosahatchee River (CR) and the Shark River (SR)] was done in terms of molecular mass (MM) and diffusion coefficients (D).