Dr. Dirk Baron
CSUB Department of Geological Sciences
Toxic Trace-Elements in Natural and Contaminated Environments
One of the important long-term environmental issues that our society faces is the management of toxic trace metals and other harmful inorganic constituents in the environment. Elevated levels of these substances are often the result of human activities but can also be naturally occurring. My main research interests are to elucidate the processes that control the mobility and fate of harmful inorganic constituents such as heavy metals in aquatic and soil environments. These processes include the formation of metal-containing solid phases, the formation of aqueous metal complexes, the adsorption of metals to soils and sediments and to aquatic particles, and reduction and oxidation reactions.
Understanding these processes is crucial for the evaluation of human health risks and ecosystem effects of inorganic contaminants and for the development of rational and cost-effective remediation strategies for contaminated sites. The scope of these research efforts ranges from spectroscopic investigations at the molecular level to bench scale experiments with natural materials and model systems to field investigations and numerical modeling.
Two specific areas of research in this field are described below:
Sources and distribution of arsenic in sediments in the southern San Joaquin Valley
the groundwater in the southern San Joaquin Valley is generally of high
quality, there are isolated pockets where the concentration of the toxic
element arsenic exceeds the drinking water standard. In this study we
examine water and sediments from two nearby wells, one with low arsenic, the
other with elevated arsenic concentrations.
Iron-chromate precipitates in chromium-contaminated soils
Chromium-containing precipitates can affect the mobility of toxic Cr(VI) in the subsurface, control its concentration in groundwater, limit its bioavailability, and impede remediation of chromium contaminated sites. These precipitates can be pure phases such as KFe3(CrO4)2(OH)6, the chromate-analog of the common sulfate mineral jarosite, or solid-solutions where chromate partially substitutes for another ion such as sulfate (e.g. Ba(SxCr1-xO4)). In my research, we are measuring the thermodynamic properties of these solids. These thermodynamic properties are the basis for determining the conditions under which these solids form and remain stable, as well as the chromium concentrations in water equilibrated with them. In addition to the practical applications, the thermodynamics of inorganic solid solutions is also one of the remaining theoretical frontiers in inorganic geochemistry. (e.g. Baron and Palmer, 2002; Drouet et al., 2003; Drouet et al., 2004).
Central California Climate History
recently acquired 45 m of core from the
This work has been funded by the National Science Foundation.
Trace-Element Chemistry of Geologic Materials
Trace-element geochemistry of tephra, chert, and obsidian
Geologic materials such as obsidian, volcanic ash, and chert from different sources can be distinguished based on their trace-element composition. We use ICP/MS and Laser Ablation ICP/MS to analyze various geological materials for stratigraphic and archaeological studies. (e.g. Baron et al., 2008; Draucker et al., 2007; Remus et al., 2010; Remus et al., 2012)
Baron D., Negrini R.M, Golob E.M.*, Miller D., Sarna-Wojcicki
A, Fleck R., Hacker B., Erendi A. (2008)
Geochemical correlation and 40Ar/39Ar dating of the Kern River Ash and related tephra: Implications for the
stratigraphy of petroleum-bearing formations in the San Joaquin Valley, California.
Quaternary International. 176, 246-260.
and Palmer C.D. (2002) Solid solution/aqueous solution interactions between jarosite
and its chromate analog. Geochimica et Cosmochimica Acta, 66, 2841-2853.
Baron D., Palmer C.D. and
Stanley J.T. (1996) Identification of two Fe-chromate precipitates in
a Cr(VI)-contaminated soil. Environmental Science & Technology, 30, 964-968.
Draucker A., Baron D., Yohe R., and
Horton R. (2007) Geochemical characterization of obsidian subsources
the Coso Range, California, USA. 2007 Goldschmidt Conference, Cologne, Germany, August 19-24, 2007.
Drouet C., Pass K.L., Baron D., Draucker
S., and Navrotsky A. (2004) On the thermochemistry of
between jarosite, natrojarosite, and alunite. Geochimica et Cosmochimica Acta, 58, 2197-2205.
Drouet C., Navrotsky A., and Baron
D. (2003) On the thermochemistry of solid solutions
between jarosite and its
chromate analog. American Mineralogist, 88, 1949-1954.
Negrini R., Rhodes D, Stephenson R., Noriega-Carlos G., Grant
L., Baron D, Wigand P, and Rich F.(2007)
Evidence of a long-lived Pleistocence lake, Carrizo Plain, California. Annual Meeting of the Geological Society of
America, Denver, CO, October 28-31, 2007, GSA Abstracts with Programs Vol. 39, No.6.
Negrini R., Baron D., Gillespie J., Horton R., Draucker A.*, Durham N.*, Huff J.*, Philley P.*, Register C.*, Parker J.,
and Haslebacher T. (2008) A middle-Pleistocene lacustrine delta in the Kern River depositional system:
structural control, regional stratigraphic context, and impact on groundwater quality.
Pacific Section of the American Association of Petroleum Geologists Publication MP48, 95-111D.
Remus J.J., Harmon R.S., Hark R.R., Potter I.K., Bristol S.K. Baron D., Haverstock G.*, and East L.J. (2012)
Advanced signal processing analysis of laser-induced breakdown spectroscopy data for the discrimination
of obsidian sources. Applied Optics, 51, B1-B9.
Remus J.J., Gottfried J.L., Harmon R.S., Draucker A.*, Baron D. and Yohe R. (2010) Archaeological applications of LIBS:
An example from the Coso Volcanic Field, CA using advanced statistical signal processing analysis.
Applied Optics 49, C120-C131.