We studied the fluorescence properties of fulvic acids isolated from streams and rivers receiving predominantly terrestrial sources of organic material and from lakes with microbial sources of organic material. Microbially derived fulvic acids have fluorophores with a more sharply defined emission peak occurring at lower wavelengths than fluorophores in terrestrially derived fulvic acids. We show that the ratio of the emission intensity at a wavelength of 450 nm to that at 500 nm, obtained with an excitation of 370 nm, can serve as a simple index to distinguish sources of isolated aquatic fulvic acids. In our study, this index has a value of ;1.9 for microbially derived fulvic acids and a value of ;1.4 for terrestrially derived fulvic acids. Fulvic acids isolated from four large rivers in the United States have fluorescence index values of 1.4‐1.5, consistent with predominantly terrestrial sources. For fulvic acid samples isolated from a river, lakes, and groundwaters in a forested watershed, the fluorescence index varied in a manner suggesting different sources for the seepage and streamfed lakes. Furthermore, we identified these distinctive fluorophores in filtered whole water samples from lakes in a desert oasis in Antarctica and in filtered whole water samples collected during snowmelt from a Rocky Mountain stream. The fluorescence index measurement in filtered whole water samples in field studies may augment the interpretation of dissolved organic carbon sources for understanding carbon cycling in aquatic ecosystems.

https://aslopubs.onlinelibrary.wiley.com/doi/epdf/10.4319/lo.2001.46.1.0038

Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity

The science of the total environment

Tracing dissolved organic matter in aquatic environments using a new approach to fluorescence spectroscopy

Mercury is one of the most hazardous contaminants that may be present in the aquatic environment, but its ecological and toxicological effects are strongly dependent on the chemical species present. Species distribution and transformation processes in natural aquatic systems are controlled by various physical, chemical, and biological factors. Depending on the prevailing environmental conditions, inorganic mercury species may be converted to many times more toxic methylated forms such as methylmercury, a potent neurotoxin that is readily accumulated by aquatic biota. Despite a considerable amount of literature on the subject, the behavior of mercury and many of the transformation and distribution mechanisms operating in the natural aquatic environment are still poorly understood. This review examines the current state of knowledge on the physicochemical behavior of mercury in the aquatic environment, and in particular the environmental factors influencing its transformation into highly toxic methylated forms.

Mercury in the Aquatic Environment: A Review of Factors Affecting Methylation

Reference LPI-ARTICLE-1999-017View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

/pdf/metal-oxide-surfaces-and-their-interactions-with-aqueous-22jt31pax0.pdf

Metal Oxide Surfaces and Their Interactions with Aqueous Solutions and Microbial Organisms.

Fulvic acid binding sites (1.3−70 μM) and EDTA (0.0017−0.18 μM) accounted for organically bound Cu in seven stream samples measured by potentiometric titration. Cu was 84−99% organically bound in filtrates with 200 nM total Cu. Binding of Cu by EDTA was limited by competition from other trace metals. Water hardness was inversely related to properties of dissolved organic carbon (DOC) that enhance fulvic acid binding:  DOC concentration, percentage of DOC that is fulvic acid, and binding sites per fulvic acid carbon. Dissolved trace metals, stabilized by organic binding, occurred at increased concentration in soft water as compared to hard water.

Copper speciation and binding by organic matter in copper-contaminated streamwater

Riparian wetlands contaminated with Hg from an industrial point source were found to be important sites of production and release of methyl mercury (MeHg) in a 40-km reach of the Sudbury River in e...

Distribution, hydrologic transport, and cycling of total mercury and methyl mercury in a contaminated river-reservoir-wetland system (Sudbury River, eastern Massachusetts).

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/pdf/residential-street-dirt-accumulation-rates-and-chemical-1c9k5g3dae.pdf

Residential Street-Dirt Accumulation Rates and Chemical Composition, and Removal Efficiencies by Mechanical- and Vacuum-Type Sweepers, New Bedford, Massachusetts, 2003-04

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A Synopsis of Technical Issues of Concern for Monitoring Trace Elements in Highway and Urban Runoff

/pdf/potential-effects-of-structural-controls-and-street-sweeping-26ba41ze1q.pdf

Robert F. Breault

Papers

Copper speciation and binding by organic matter in copper-contaminated streamwater

Distribution, hydrologic transport, and cycling of total mercury and methyl mercury in a contaminated river-reservoir-wetland system (Sudbury River, eastern Massachusetts).

Residential Street-Dirt Accumulation Rates and Chemical Composition, and Removal Efficiencies by Mechanical- and Vacuum-Type Sweepers, New Bedford, Massachusetts, 2003-04

A Synopsis of Technical Issues of Concern for Monitoring Trace Elements in Highway and Urban Runoff

Potential effects of structural controls and street sweeping on stormwater loads to the lower Charles River, Massachusetts