From ceginfo@u.washington.edu Fri Aug 8 10:38:42 2003 Received: from mxu1.u.washington.edu (mxu1.u.washington.edu [140.142.32.132]) by lists.u.washington.edu (8.12.9+UW03.06/8.12.9+UW03.06) with ESMTP id h78Hcg2x061896 for ; Fri, 8 Aug 2003 10:38:42 -0700 Received: from mxout3.cac.washington.edu (mxout3.cac.washington.edu [140.142.32.166]) by mxu1.u.washington.edu (8.12.9+UW03.06/8.12.9+UW03.06) with ESMTP id h78HcfdM004134 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO) for ; Fri, 8 Aug 2003 10:38:41 -0700 Received: from homer35.u.washington.edu (homer35.u.washington.edu [140.142.16.13]) by mxout3.cac.washington.edu (8.12.9+UW03.06/8.12.9+UW03.06) with ESMTP id h78HcegG001468 for ; Fri, 8 Aug 2003 10:38:40 -0700 Received: from localhost (ceginfo@localhost) by homer35.u.washington.edu (8.12.9+UW03.06/8.12.9+UW03.06) with ESMTP id h78HceD0116514 for ; Fri, 8 Aug 2003 10:38:40 -0700 Date: Fri, 8 Aug 2003 10:38:40 -0700 (PDT) From: Civil and Environmental Engineering To: cegrads@u.washington.edu Subject: Special Guest Seminar--August 14 at 2:00 (fwd) Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Uwash-Spam: Gauge=IIIIIII, Probability=7%, Report='__HAS_MSGID, __SANE_MSGID, SUBJECT_MONTH_2, SUBJECT_MONTH, SUPERLONG_LINE, SPAM_PHRASE_00_01' Special Guest Seminar "Using a Suite of Analytical Tools to Assess Metal Speciation and Bioavailability of Metals in Aquatic Systems" Amy L. Dahl, Ph.D. Candidate Northwestern University Dept. of Civil and Environmental Engineering Thursday, August 14, at 2:00 pm in More 225 Organized by Professor David Stahl and Heidi Gough Dept. of Civil and Environmental Engineering Abstract: In order to better understand the relationship between metal speciation and microorganisms in the environment we utilize a variety of sophisticated analytical techniques, including X-ray absorption spectroscopy (XAS), electrochemistry and whole-cell biosensors. I will present the results of three different experiments probing these relationships. The first is a proof-of-concept experiment seeking to validate indirect sequential extraction methods with XAS, a direct speciation method. XAS confirms that sequential extraction of artificially amended samples generally adheres to the scheme outlined by Tessier. However, the analysis of natural samples by XAS and sequential extractions do not agree, specifically regarding the sulfide phase. Furthermore, we show that zinc phosphates are extracted by more than one step, thus confusing interpretation of sequential extraction results when phosphates are present. In the second experiment, anaerobes isolated from Lake DePue sediments were exposed to varying concentrations of zinc in a minimally complexing growth medium. Various microbial and chemical parameters were monitored to correlate toxicity with metal speciation. Our results show that microbes isolated from metal contaminated sediments, as well as E. coli, have minimum inhibitory concentrations lower than those previously reported (mM vs. mM range). In order to more accurately utilize voltammetry as a measurement of bioavailability, we compared the response of a whole-cell biosensor sensitive to mercury between 20-200 nM to square-wave voltammetry in the presence of different ligands. Results show that EDTA significantly suppresses the voltammetric response but only slightly reduces the response of the biosensor and only at high EDTA concentrations. Additional experiments expose our biosensor to mercury solids with solubilities lower than the detection level of the biosensor. Surprisingly, HgO completely inhibits growth of the biosensor. While the biosensor is able to grow in the presence of HgS, light is produced, indicating that mercury is transported inside the cell. Pam Hjelm, Secretary University of Washington Dept. of Civil and Environmental Engineering Box 352700 Seattle, WA 98195-2700 Phone: 206-543-2549 Fax: 206-685-9185 .