<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1253">
<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>
</head>
<body dir="ltr">
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)">Hello All,</span>
<div style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)"><br>
</div>
<div style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)">Please join us today, 27th September for our Enviro-lunch seminar-series second guest speaker Marisa Nicole Repasch from 12 noon- 1 PM PST via ZOOM</div>
<span style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)"><a href="https://ucmerced.zoom.us/j/175736103" target="_blank" rel="noopener noreferrer" data-auth="NotApplicable" data-linkindex="0" style="margin:0px;font-size:14.6667px;font-family:Calibri, sans-serif;background-color:rgb(255, 255, 255)">https://ucmerced.zoom.us/j/175736103</a></span><br>
</div>
<div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Regards,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Manisha </div>
<div id="appendonsend"></div>
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Manisha Dolui<br>
<b>Sent:</b> Thursday, September 23, 2021 4:59 PM<br>
<b>To:</b> enviro-lunch@lists.ucmerced.edu <enviro-lunch@lists.ucmerced.edu>; Maeve McCormick <mmccormick6@ucmerced.edu><br>
<b>Cc:</b> Repasch, Marisa Nicole <repasch1@llnl.gov><br>
<b>Subject:</b> Enviro-lunch Monday 9/27/2021 by Marisa Nicole Repasch on "The fate of organic carbon during source-to-sink river transit: the importance of mineral associations and sediment residence time"</font>
<div> </div>
</div>
<div dir="ltr">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<img size="27896" style="max-width:100%" data-outlook-trace="F:2|T:2" src="cid:ff50effb-769f-44b7-892c-464c954ace33"><br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Hello All,</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Please join us this Monday 27th September for our Enviro-lunch seminar-series second guest speaker Marisa Nicole Repasch from 12 noon- 1 PM PST via ZOOM</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<a href="https://ucmerced.zoom.us/j/175736103" target="_blank" rel="noopener noreferrer" style="margin:0px; font-size:14.6667px; font-family:Calibri,sans-serif; background-color:rgb(255,255,255)">https://ucmerced.zoom.us/j/175736103</a><br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<img size="2222680" style="max-width:100%" data-outlook-trace="F:2|T:2" src="cid:0a49c339-581b-47f8-a5b8-80b3e0b878bb"><br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Helvetica,sans-serif">Title: </span><span style="font-family:Calibri,Helvetica,sans-serif"><b style="color:rgb(32,31,30); font-size:14.6667px; background-color:rgb(255,255,255)">The fate of organic carbon during source-to-sink
river transit: the importance of mineral associations and sediment residence time</b></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<b style="color:rgb(32,31,30); font-family:Calibri,sans-serif; font-size:14.6667px; background-color:rgb(255,255,255)">
<p style="margin-top: 0px; margin-bottom: 0px;font-weight:400; background-color:rgb(255,255,255); font-size:11pt; margin:0px">
<b><br>
</b></p>
<p style="margin-top: 0px; margin-bottom: 0px;font-weight:400; background-color:rgb(255,255,255); font-size:11pt; margin:0px">
<span style="font-family:Calibri,Helvetica,sans-serif"><b>Abstract:</b></span></p>
<p style="margin-top: 0px; margin-bottom: 0px;font-weight:400; background-color:rgb(255,255,255); font-size:11pt; text-indent:36pt; margin:0px">
<span style="font-family:Calibri,Helvetica,sans-serif">Rivers are primary conduits for organic carbon (OC) transfer from vegetation-rich uplands to long-term sinks, and thus are responsible for significant fluxes among different reservoirs of the carbon cycle.
The balance between OC oxidation and preservation in rivers determines whether fluvial transport leads to net release or drawdown of atmospheric CO2. Unfortunately, there are large uncertainties associated with river OC flux estimates, because we do not fully
understand the timescale of sediment and organic matter transit from source to sink or the mechanisms of organic matter preservation.</span></p>
<p style="margin-top: 0px; margin-bottom: 0px;font-weight:400; background-color:rgb(255,255,255); font-size:11pt; text-indent:36pt; margin:0px">
<span style="font-family:Calibri,Helvetica,sans-serif">In this talk, I address the uncertainties in transit time and OC preservation mechanisms in a detailed study of a unique river system in Argentina - the Rio Bermejo. This river exports sediment and organic
carbon from the central Andes and transports it nearly 1300 km downstream without tributaries. Using meteoric cosmogenic Beryllium-10 as a sediment tracer, I found that sediment resides in the river systems for ~8.5 kyr, accounting for multiple cycles of deposition
and re-mobilization. Over the ~1300 km transit distance, radiocarbon measurements suggest that the fraction of modern OC (F14C) decreases from 0.92 to 0.86, corresponding to ~500 yr of aging. We also observed enrichment of ä13C values along the channel. Compound-specific
F14C and ä13C measurements suggest there is an older organic matter pool that is preferentially preserved and ages during fluvial transit, while labile organic matter is turned over rapidly. Concentrations of oxyhydroxide metals correlate with F14C values,
suggesting that organo-mineral complexation is an important carbon stabilization mechanism. These data are supported by nanoSIMS images showing organic carbon associations with clay minerals. By combining radiocarbon data with geomorphic rates, I developed
a framework to estimate carbon turnover during fluvial transit, allowing us to compare carbon oxidation fluxes to river export fluxes for the first time. This framework will allow us to assess the carbon budgets of major rivers around the world.</span></p>
<p style="margin-top: 0px; margin-bottom: 0px;font-weight:400; background-color:rgb(255,255,255); font-size:11pt; margin:0px">
<span style="font-family:Calibri,Helvetica,sans-serif"> </span></p>
<p style="margin-top: 0px; margin-bottom: 0px;font-weight:400; background-color:rgb(255,255,255); font-size:11pt; margin:0px">
<span style="font-family:Calibri,Helvetica,sans-serif"><b>Bio:</b></span></p>
<p style="margin-top: 0px; margin-bottom: 0px;font-weight:400; background-color:rgb(255,255,255); font-size:11pt; text-indent:36pt; margin:0px">
<span class="x_markwdvyvdapp" style="margin:0px; font-family:Calibri,Helvetica,sans-serif">Marisa</span><span style="font-family:Calibri,Helvetica,sans-serif"> </span><span class="x_markwhvg2yt2b" style="margin:0px; font-family:Calibri,Helvetica,sans-serif">Repasch</span><span style="font-family:Calibri,Helvetica,sans-serif"> </span><span style="font-family:Calibri,Helvetica,sans-serif">is
a Postdoctoral Researcher at Lawrence Livermore National Lab, in the Center for Accelerator Mass Spectrometry. She recently completed her Ph.D. in Geochemistry at the University of Potsdam in Germany and performed most of her research at the German Research
Center for Geosciences (GFZ Potsdam). She received her B.S. in Earth and Environmental Science from Lehigh University and her M.S. in Earth and Planetary Sciences from the University of New Mexico. In her doctoral research, she combined cosmogenic nuclide
geochemistry, carbon isotopes, and geomorphology to understand the fate of organic matter transported through river systems. Her current research focuses on the impacts of landscape disturbance, like wildfires and permafrost thaw on the transfer of sediment
and carbon across the landscape. Outside of her academic career, she enjoys mountain biking and volunteering with local conservation and trail stewardship groups.</span></p>
<div style="font-weight:400; background-color:rgb(255,255,255); font-size:11pt; text-indent:36pt; margin:0px">
<br>
</div>
<div style="font-weight:400; background-color:rgb(255,255,255); font-size:11pt; text-indent:36pt; margin:0px">
<p class="x_x_MsoNormal" style="margin-top: 0px; margin-bottom: 0px;margin:0in; font-size:11pt; text-indent:0px; background-color:rgb(255,255,255)">
<span style="margin:0px; font-size:12pt; font-family:Calibri,Helvetica,sans-serif; color:black">We’ll see you there!</span></p>
<p class="x_x_MsoNormal" style="margin-top: 0px; margin-bottom: 0px;margin:0in; font-size:11pt; text-indent:0px; background-color:rgb(255,255,255)">
<span style="margin:0px; font-size:12pt; font-family:Calibri,Helvetica,sans-serif; color:black"> </span></p>
<p class="x_x_MsoNormal" style="margin-top: 0px; margin-bottom: 0px;margin:0in; font-size:11pt; text-indent:0px; background-color:rgb(255,255,255)">
<span style="margin:0px; font-size:12pt; font-family:Calibri,Helvetica,sans-serif; color:black">Regards,</span></p>
<p class="x_x_MsoNormal" style="margin-top: 0px; margin-bottom: 0px;margin:0in; font-size:11pt; text-indent:0px; background-color:rgb(255,255,255)">
<span style="margin:0px; font-size:12pt; font-family:Calibri,Helvetica,sans-serif; color:black">Toshi, KJ , Manisha and Jennifer (Student and Post-doc coordinators), and Dr. Asmeret Asefaw Berhe (Faculty coordinator)</span></p>
<br>
</div>
<div style="font-weight:400; background-color:rgb(255,255,255); font-size:11pt; text-indent:36pt; margin:0px">
<br>
</div>
<br>
</b></div>
</div>
</div>
</body>
</html>