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Metals, Soils, Pollution and Plasma Spectrochemistry

My research in analytical chemistry involves the identification (What are they?) and quantification (…then how much?) of chemical species. In addition, I do investigations of fate and transport properties of trace metals in soils, aquatic environments (see Figure. 1), and biological materials. My students and I use spectroscopic methods including inductively coupled plasma -mass spectrometry (ICP-MS) and atomic emission spectroscopy (ICP-AES) (see Figure. 2) for these investigations. Plasma spectrochemistry is the hub of my research, and that radiates to an intriguing array of interdisciplinary research questions that involve analysis of environmental and biological materials such as humic substances and children's teeth.

Division III students in our research group often present their work in national and international scientific forums, and some have published their work in peer reviewed journals and edited books.

Metal Complexation Properties of Humic Substances

Understanding and analyzing the chemical and physical properties of humic substances is vitally important in planning the clean-up of contaminated sites and in developing effective soil remediation programs (Figure 3). Humic substances are dark brown organic macromolecules found in aquatic and soil environments. They are important carbon reservoirs and thermal buffers in subsurface soils so they play vital roles in determining how well agricultural soils retain nutrients and how long contaminated soils, sediments, and water retain toxic trace metals.

For the past five years we have been characterizing physical properties such as diffusion coefficient, molecular weights, sizes and trace metal complexing properties of humic substances using flow field-flow fractionation (flow FFF) and high performance liquid chromatography (HPLC) methods. In addition we have investigated the chemical functionality of humic substances and how these substances affect the metal (i.e., Al, Cu, Cd, Mn, Pb, Zn, Fe) complexation properties of soils, composts, and sediments.

Trace Metal Distribution in Children's Teeth

Enamel growth layers of teeth can provide information about one's past nutritional status and exposure to trace metals. Such information can be an important health indicator in children. In collaboration with Biological anthropologist, geologist, and a team of Hampshire students, (Figure 2) we are examining distribution of trace metals (Zn, Fe, Pb, Ca, and Sr) in the enamel of deciduous teeth of children from Solis Valley, Mexico. This work is supported by NSF collaborative research in undergraduate institutions (CRUI) grant.

Laser ablation is used to "scoop" micro samples of enamel material from the teeth, and presence of trace elements is determined by the ICP-MS

The investigation of the distribution of trace metals in particular growth layers on the teeth enamel indicates whether these substances were deposited before or after birth (pre- and post-natal). In addition we investigate lead in glazed ceramics and measure lead isotope ratios in teeth using ICP-MS to determine source origins of lead pollution.

Sample Preparation Methods for Plasma Spectrochemical Trace Metal Analysis

Proper collection and preparation of samples is critical to accurate analysis of trace metals in environmental and biological material, but it is also the Achilles heel or weakest link. It is necessary to develop accurate and efficient sample digestion methods. Novel sample preparation methods have been developed in our lab for ICP-AES and MS analysis of environmental and biological samples such as syrups and breast milk.