Advanced Analytical Methods for the Direct Quantification and Characterization of Ambient Metal Species in Natural WatersEPA Grant Number: R826187
Title: Advanced Analytical Methods for the Direct Quantification and Characterization of Ambient Metal Species in Natural Waters
Investigators: Hering, Janet G.
Institution: California Institute of Technology
EPA Project Officer: Lasat, Mitch
Project Period: January 1, 1998 through June 30, 1999 (Extended to March 31, 2000)
Project Amount: $116,985
RFA: Exploratory Research - Environmental Chemistry (1997) RFA Text | Recipients Lists
Research Category: Water , Land and Waste Management , Air , Engineering and Environmental Chemistry
The project objective is to develop a method using electrospray mass spectrometry (ESMS) to determine metal speciation directly in model systems and natural waters. Method development will include: 1) validation of the ESMS method using model systems (i.e., well-defined mixtures of metals and complexing agents of known metal affinities), 2) systematic application of the ESMS method to examine trace metal complexation by natural organic matter (with isolated humic and fulvic substances and whole water samples) to generate data compatible with equilibrium speciation modeling (using codes such as MINEQL) and comparable with studies based on detection of free (or labile) metal species, 3) use of the ESMS method to investigate competitive effects (both kinetic and equilibrium effects) in multi-metal systems, and 4) determination of requirements (e.g., for pre-concentration or chromatographic separation) for the application of the ESMS characterization method to whole water samples.
The proposed project will take advantage of current advances in analytical instrumentation to develop methods for the direct quantification and characterization of ambient metal species. This approach will combine the sensitivity of mass spectrometry (MS) with the newly-developed electrospray (ES) interface for MS analysis of non-volatile species. Studies will be conducted with model metal-organic and colloidal metal species as well as with whole water samples. Studies will emphasize investigation of metal competition in multi-metal system and integration of metal complexation data with geochemical models of equilibrium speciation.
The fate and ecotoxicological effects of metal inputs to aquatic environment cannot be fully understood without careful consideration of the physicochemical forms in which the metals occur (i.e., metal speciation). Explicit consideration of metal speciation is not yet, however, incorporated into water quality criteria. An impediment to such incorporation is the lack of information on the dominant metal species in natural waters at ambient metal concentrations. The proposed project will address this research need by developing methods, based on advanced analytical techniques, for the direct quantification and characterization of ambient metal species.