<div dir="ltr"><div><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><img id="gmail-m_-8385520339006379166m_-8050262914676925568gmail-m_1802579404819878784908E2BA3-0C21-4BC6-8E88-6A783FDB4BCE" src="cid:35AD16B5-5C20-4F2C-BCD3-8BAC0F72CAFB@hsd1.ca.comcast.net." style="font-size: 14px;"><br></div></div></div></div></div></div></div></div></div><div dir="ltr"><div class="gmail_quote"><div dir="ltr"><div dir="ltr"><div class="gmail_quote"><div dir="ltr"><div dir="ltr"><div class="gmail_quote"><div style="word-wrap:break-word"><p class="MsoNormal" style="line-height:13.8px"><span style="line-height:16.1px;font-size:14px">Dear all,<u></u><u></u></span></p><p class="MsoNormal" style="line-height:13.8px"><span style="line-height:16.1px;font-size:14px">Please join us this Thursday (11/2) for our speaker, Stefanie Helmrich from UC Merced.<u></u><u></u></span></p><p class="MsoNormal" style="line-height:13.8px"><span style="line-height:16.1px;font-size:14px"><br></span></p><p class="MsoNormal" align="center" style="text-align:center;line-height:13.8px"><font size="4"><b><span style="line-height:16.1px"> </span></b><a name="_Hlk493244815" style=""><span style="line-height:107%">Simulating</span></a><b style=""><span style="line-height:107%"> </span></b><span style="line-height:107%">methylmercury production at the sediment-water
interface to improve the water quality in the San Francisco Bay-Delta</span></font></p>
<p class="MsoNormal" style="text-align:center"><b style="font-size:14px"> </b></p><p class="MsoNormal" align="center" style="text-align:center"><b style="font-size:14px">Stefanie Helmrich<u></u><u></u></b></p><p class="MsoNormal" align="center" style="text-align:center"><span style="font-size:14px">UC Merced</span><b style="font-size:14px"><br></b></p><p class="MsoNormal" align="center" style="text-align:center"><b style="font-size:14px"></b><span style="font-size:14px"> </span><b style="font-size:14px"><br></b></p><p class="MsoNormal">
</p><p class="MsoNormal" style="text-align:center"><b style="font-size:14px;text-indent:0in">Abstract</b><span style="font-size:14px;text-indent:0in;line-height:16.1px">: </span><br></p><p class="gmail-m_-8385520339006379166m_-8050262914676925568gmail-m_1802579404819878784Paragraph" style="text-align:center;text-indent:0in;line-height:13.8px">
</p><p class="gmail-Garamondfont"><span style="font-family:Calibri,sans-serif">Mercury (Hg) in the environment poses a
significant threat to human and ecological health, and is a major contaminant
of concern for water quality in California. Methylmercury (MeHg) is the most
toxic form of Hg and bioaccumulates in fish and higher organisms. The San
Francisco Bay-Delta received significant amounts of inorganic Hg from the
Sierra Nevada foothills due to historic gold mining and anoxic sediments in
wetlands in the Delta are hotspots for bacterially driven MeHg production. Environmental
conditions that influence the net methylation of Hg are known, but
quantification of water-column concentrations of MeHg is still difficult
because of the high cost of collecting data over detailed spatial and temporal
scales. However, quantification of MeHg concentrations is important to plan
mitigation and remediation measures. Computer simulations can provide a tool to
predict Hg and MeHg concentrations over a range of hydrologic conditions and
improve understanding of hydrogeochemical and biological processes controlling
Hg and MeHg transport and fate. As such, I am developing a mechanism-based
reactive-transport model to simulate the mercury cycle at the sediment-water
interface. As a first step, I am investigating how to utilize incubation
experiments with isotopically labeled tracers to parameterize (de)methylation
reactions in the model. A considerable number of incubation experiments have been carried out in the last two decades. However, the assumptions made in
calculating (de)methylation rate constant, and the conditions of the incubation
experiments differ between studies. I am assessing the suitability of the
reported rate constants for use in a generalized kinetic model and I will
assess the selected rate constants by comparing simulated MeHg concentrations
with those measured in incubation experiments. It is important to
note that the kinetic rates and the corresponding rate constants are empirical
in nature, however, the thermodynamic framework is not empirical. The model
development will yield new insights and the mechanistic model can be applied to
sites with the same environmental conditions to simulate MeHg concentrations at
the sediment-water interface.<span></span></span></p>
<p class="MsoNormal" style="text-align:center"><span style="font-size:10pt;font-family:Helvetica,sans-serif"><span> </span></span></p>
<p class="MsoNormal" style="text-align:center;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><span style="font-size:10pt;font-family:Helvetica,sans-serif"><b>Bio: </b></span></p><p class="MsoNormal" style="text-align:center;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial">
</p><p class="gmail-Garamondfont"><span style="font-family:Calibri,sans-serif">Stefanie is a second year Ph.D. student and
her research aim is to develop and scale up a biogeochemical reaction-transport
model for simulating the fate of mercury. Before Stefanie came to UC Merced,
she graduated with a Master of Science in Water Management from Technical
University of Dresden in Germany and she did an internship at the Lawrence
Berkeley National Lab. Her master thesis focused on two-dimensional
surface-runoff simulations coupled to a channel network model to predict
flooding in urban areas. As an intern at the Berkeley Lab Stefanie used
SJRWARMF to simulate the fate of mercury on the watershed scale. <span> </span></span><span style="font-size:14pt;line-height:107%"><span></span></span></p>
<div><span style="font-size:14px"> </span><br class="gmail-m_-8385520339006379166m_-8050262914676925568gmail-m_1802579404819878784webkit-block-placeholder"></div><p class="MsoNormal"><span style="font-size:14px">When: Nov 2</span><span style="font-size:11.6667px">nd</span><span style="font-size:14px">,</span><sup style="font-size:14px"> </sup><span style="font-size:14px">Thursday, 12pm – 1pm<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14px">Where: SE2-302 <u></u><u></u></span></p><div><span style="font-size:14px"> </span><br class="gmail-m_-8385520339006379166m_-8050262914676925568gmail-m_1802579404819878784webkit-block-placeholder"></div><p class="MsoNormal"><span style="font-size:14px">Coffee will be provided and please bring your own mugs.<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14px">We look forward to seeing you,<u></u><u></u></span></p><div><span style="font-size:14px"> </span><br class="gmail-m_-8385520339006379166m_-8050262914676925568gmail-m_1802579404819878784webkit-block-placeholder"></div><p class="MsoNormal"><span style="font-size:14px">Organizers for 2017-18: Nate Bogie and Lixia Jin<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14px">Faculty coordinator: Asmeret Asefaw Berhe<br></span></p></div><br></div></div></div></div></div></div></div></div></div>