[Enviro-lunch] Tomorrow: Enviro-lunch (8/31): Jing Yan

[Nate Bogie]

Dear all,

Please support our community in Earth and environmental sciences by
attending our weekly events. This week's speaker in our Enviro-lunch brown
bag seminar series will be:



*Jing Yan *

Postdoctoral Researcher, Environmental Systems

*Quantification and characterization of mobile colloids: *

*their potential role in carbon cycling under varying redox conditions*



*Abstract*: Mobile colloids, 1-1000 nm particles, have attracted much
research attention because they have small size and large specific surface
area therefore the potential to facilitate the transport of contaminants in
the subsurface environment. Despite colloids’ potential importance, the
role of mobile colloids in carbon cycling under varying redox conditions is
largely unknown. This study, combining laboratory investigations and field
measurements, focused on (1) identification and understanding of the key
processes and pathways leading to colloid and colloidal organic carbon
(COC) release under dynamic redox conditions and (2) quantification of the
actual colloidal load and assessment of colloids’ role in organic carbon
retention and mobilization in representative environmental systems. To
achieve these goals, a series of experiments were conducted. Firstly, the
complex interplay of soil colloid release, organic matter content, and
redox conditions were investigated via batch experiments. The findings
clearly illustrate that carbon retention on colloids goes through different
pathways, and organic carbon associated with colloids serves as either
carbon source or sink depending on redox state. Secondly, an innovative
methodology was developed to quantify mobile colloids in < 0.1, 0.1-0.45
and 0.45-1.0 µm fractions using size-dependent correlations between
nephelometric turbidity and colloid mass concentration. Colloid size
strongly affected concentration-turbidity correlations, while colloid
composition played a less important role in shifting the correlations.
Lastly, the actual colloidal load and COC pool, especially those in < 0.45
μm fraction, were quantitatively examined in agricultural, forestry,
wetland and estuarine systems. The results reveal that amounts of colloids
and COC were substantial and COC accounted for 8-19% of organic carbon in <
0.45 µm fraction. In addition, compared to other investigated sites,
wetland was found to be a hotspot of both colloid and COC release and
mobilization.



When: Aug. 31st, Thursday, 12pm – 1pm

Where: SE2-302



Coffee will be provided and please bring your own mugs.

We look forward to seeing you,



Organizers for 2017-18: Nate Bogie and Lixia Jin

Faculty coordinator: Asmeret Asefaw Berhe

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http://lists.ucmerced.edu/mailman/listinfo/enviro-lunch
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