Comment Cite This: Environ. Sci. Technol. XXXX, XXX, XXX−XXX
pubs.acs.org/est
A Tribute to George R. Aiken
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bially-derived” DOM, have observed properties and reactivity that are starkly different from DOM derived from environments influenced by plants and terrestrial soils. Thus, George helped introduce the concept that “composition matters” when it comes to studying the chemistry of DOM, and amassed a collection of XAD-8 isolates that spans the Poles (from the Yukon River in taiga Alaska to the Dry Valleys of Antarctica) and everywhere in between. The availability of these isolates has allowed scientists and engineers to think about DOM in terms of a biogeochemical continuum, from terrestrial to aquatic environments. George believed in the power of collaboration to solve complex environmental problems. George’s work influenced many areas of inquiry, including the cycling of mercury, DOM’s role in drinking water treatment, and the development of advanced analytical methods for the characterization of DOM. The combination of his curiosity coupled with his generosity with respect to both time and sharing his DOM isolates, helped forge the careers of numerous scientists, including the editors of this special virtual issue. It was George’s great ability to bring in different points of views and tease out relationships between DOM composition and its reactivity that made collaborations with him so satisfying. Further, George was an excellent mentor to graduate students and he selflessly gave his time to explain difficult concepts and/or interpret data. This issue is dedicated to the memory of George.
n late 2016, George R. Aiken passed away. George was arguably one of the most influential scientists in environmental chemistry and biogeochemistry. During a career spanning over four decades, George was a leader in the study of dissolved organic matter (DOM). His work profoundly changed the way we view DOM and its importance in many environmental and biogeochemical processes. At the start of George’s career, DOM was simply known as “gelbstoff”, which translates to English from German as “yellow matter”, and was thought to be derived from soil humus. From the early 1970s onward, George was part of a core group of scientists at the U.S. Geological Survey (USGS) National Research Program, who were attempting to unravel the composition of DOM. This group of scientists included such important figures as Ron Malcolm, Jerry Leenheer, and Michael Thurman. George joined the USGS in the mid 1970s, where he worked with Ron Malcolm to develop approaches to isolate different DOM components by chromatography. His paper “Comparison of XAD Macroporous Resins for the Concentration of Fulvic Acid from Aqueous Solution”, which was published in Analytical Chemistry in 1979, set the stage for standardizing the isolation of fulvic and humic acids from bulk DOM using the acrylic ester resin XAD-8. This methodology, published in a highly cited paper by Thurman and Malcolm (1981: Preparative isolation of aquatic humic substances, Environmental Science & Technology, 15, 463−466; DOI: 10.1021/ es00086a012.), ultimately became the standard isolation approach in numerous studies examining the influence of DOM on biogeochemical processes, and influenced how scientists viewed DOM. After a brief stay at Dartmouth College, George returned to the USGS lab in Colorado, to continue working with his colleagues (including our co-editor Diane McKnight) on the characterization of the various components of DOM. In order to provide the research community-at-large with DOM reference materials, the USGS team chose the Suwannee River as the site for the initial isolation of fulvic acids. One important feature of this site near the Okefenokee wetland was that the DOM composition was temporally stable. George spent many months engaged in both field and laboratory efforts to obtain these reference materials, which were described in the USGS, report “Humic Substances in the Suwannee River, Georgia”. Also underway at that time was the famous “green book” Humic Substances In Soil, Sediment And Water: Geochemistry, Isolation and Characterization, which George edited with Diane McKnight, Robert Wershaw, and Pat MacCarthy. The green book became an important reference for anyone conducting DOM research for the next 20 years. During this time, George became interested in the composition of DOM from diverse environments. In particular, the desert oases of continental Antarctica are nearly devoid of higher plants that are important DOM precursors present nearly everywhere else. George and Diane McKnight were among the pioneers that introduced our community to DOM derived strictly from microbial phototrophs, for example, algae and bacteria. Over the decades, scientists using this “micro© XXXX American Chemical Society
Yu-Ping Chin*,† Diane McKnight‡,§ Fernando L. Rosario-Ortiz‡ †
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Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware 19716, United States ‡ Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, Colorado 80503, United States § INSTAAR, University of Colorado, Boulder, Colorado 80309, United States
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Yu-Ping Chin: 0000-0003-1427-9156 Fernando L. Rosario-Ortiz: 0000-0002-3311-9089 Notes
Views expressed in this editorial are those of the authors and not necessarily the views of the ACS. The authors declare no competing financial interest.
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DOI: 10.1021/acs.est.8b01002 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
