(2020) Consistent Controls on Trace Metal Micronutrient Speciation in Wetland Soils and Stream Sediments
Catalano J, Yan J, Flynn E, Sharma N, Giammar D, Schwartz G, Brooks S, Weisenhorn P, Kemner K, O'Loughlin E & Kaplan D
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12b: Room 4, Friday 26th June 05:30 - 05:33
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Hello Dr. Catalano, Thank you to your collaborators and you for sharing this amazing work and presentation. It was great to listen to you after several years. It was truly a surprise to see most trace metals that you investigated were predominantly present in the residual fraction, and that the speciation seemed similar, even though diverse environments were sampled. Does that indicate that most biogeochemical cycles end up circulating a very small fraction of the trace metal, without impacting the larger pool? I would be curious to know what would be the forms of these labile species. Were there differences in physicochemical parameters like pH and Eh that stood out, even though it would possibly be difficult to reliably measure redox potential. What would the wet chemical speciation indicate? If possible, I would also probe any potential colloids in the associated water in this system. Is the labile Ni truly dissolved? If suspended, could it be characterized by TEM-SAED and XPS after collecting these particles on filters? If so, one may get a sense of what these labile fractions might be? Also, it would be interesting to see if this speciation is time-dependent. For example, if you were to sample again these locations in different seasons of the year, will the labile pools change? Just some thoughts. Please disregard, if not feasible. Otherwise, I look forward to your response. Thanks, Abhas (from India)
Hi Dr. Catalano, Thanks for sharing, this was an excellent talk! I thought it was interesting that most of the trace metals were non-extractable and I was curious about the process used for the sequential extractions, if there was a reference or protocol you'd be willing to point me towards! Thanks, Kagan Meier
Hi Kagan! Many thanks for your question. We have submitted a manuscript on some earlier work that contains the relevant details. Our methods are adapted from: Dollar, N. L., Souch, C. J., Filippelli, G. M. & Mastalerz, M. Chemical fractionation of metals in wetland sediments: Indiana Dunes National Lakeshore. Environ. Sci. Technol. 35, 3608-3615 (2001). Our methods are also summarized in a data package that is online, again with our earlier study that was recently submitted. You can view the data package (scroll down far for the methods) at doi:10.15485/1630815.
Very nice talk Jeff! It would be very interesting to see additional XAS work on the sequential extracts although there are obvious potential issues related to artifacts of the sequential extractions. Mostly, I am curious to see if the speciation results remain the same after the extractions (given the high unextractable content, I would think yes). If that is the case, what is the speciation of the metals that are available for microbial uptake (for methanogenesis for instance). Nice work! -- AaronT.
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