Chemistry at ESF

ESF's Department of Chemistry is uniquely organized around the interdisciplinary areas of biochemistry and natural products chemistry, environmental chemistry, and polymer chemistry. The department's 71,000-square-foot Edwin C. Jahn Laboratory is a state-of-the-art facility, fully equipped for modern chemical research and teaching.

Chemistry students gain a strong foundation in the traditional areas of analytical, inorganic, organic, and physical chemistry, but also in the integration of these areas into specialties aligned with the needs of the 21st century. All Chemistry majors participate in research, gaining familiarity with the actual practice of chemistry.

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Featured Chemistry Paper

Classical interpretation of aquatic fluorescence signals gets muddy?

Leanne C. Powers, Laura L. Lapham, Sairah Y. Malkin, Andrew Heyes, Philippe Schmitt-Kopplin, and Michael Gonsior. Molecular and optical characterization reveals the preservation and sulfurization of chemically diverse porewater dissolved organic matter in oligohaline and brackish Chesapeake Bay sediments. Organic Geochemistry. 2021. (https://www.sciencedirect.com/science/article/abs/pii/S0146638021001455)

Figure A) Map of Chesapeake Bay with sampling sites marked. B) DOM mass spectrometry results: Circled regions correspond to H/C versus O/C ratios of molecular ions found in sediment pore waters of the upper Bay (lower circle, gold star) and mid Bay (upper circle, red hexagon) where blue ions (bubbles) contain carbon, hydrogen and oxygen (CHO), orange contain CHO + nitrogen (CHNO) and green contain CHO + sulfur (CHOS). C) 3D fluorescence spectra of upper Bay sediment pore water (bottom) and mid Bay sediment pore water (top).

Dissolved organic matter (DOM) occurs in every river, lake, and ocean, and is a critical component in the global carbon cycle. However, DOM remains poorly understood and poorly described, so that modeling its sources and transformations in the environment is still a challenge. 3D fluorescence spectroscopy (or excitation-emission matrix spectroscopy) emerged decades ago as a simple and useful tool to characterize DOM, and various fluorescence signals are assigned to specific chemical properties. When DOM from humus (a major component of soil) absorbs light of wavelengths 250-275 nm, it mostly fluoresces near 450 nm. This "humic-like" fluorescence is very different from the behavior of most compounds. For this reason, humic-like fluorescence is usually assumed to arise from DOM that originated on land, even if the DOM was collected from water.

In this work, Dr. Powers and colleagues found that this interpretation does not always hold. They collected porewater samples from sediment cores from two sites: the upper- and mid-Chesapeake Bay (Panel A). Mass spectrometry (Panel B) shows that DOM from these two sites have very different chemical composition (H/C and O/C ratios), confirming previous work that the upper part of the Bay contains DOM from land-based sources, whereas the mid-Bay contains DOM from aquatic algae and microbes. However, DOM from both sources produce "humic-like" fluorescence (Panel C). This work supports the growing idea that DOM from algae can have fluorescence features similar to land-based materials. This may require scientists to re-evaluate previous results that relied on humic-like fluorescence to assign a terrestrial origin to DOM. Because accurate estimates of DOM sources are needed to model the global carbon cycle now and into the future, the use of fluorescence spectroscopy in this regard will require careful interpretation and supporting data.