[Enviro-lunch] Enviro-lunch (11/5): oxidative weathering of ancient organic matter and formation of modern soils

[Kyungjin Min]

[image: image.png]

Hello all,

This week Dr. Todd Longbottom, a new postdoctoral fellow at UC Merced
(advisor: Dr. Asmeret Asefaw Berhe), is presenting his research on the
weathering and formation of soils. Please join us on Nov 5th between 12-1
pm.

Join Zoom Meeting Enviro-lunch

https://ucmerced.zoom.us/j/175736103

Meeting ID: 175 736 103
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+16699006833,,175736103# US (San Jose)
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*Title:*
Oxidative weathering of ancient organic matter and formation of modern soils



*Abstract: *
Ancient sedimentary organic matter (kerogen) represents the largest
terrestrial organic carbon (OC) reservoir on earth and is vulnerable to
remineralization upon exposure to earth’s atmosphere during the oxidative
weathering of sedimentary rocks on the continents. Due to the potential for
large carbon-cycle implications, the mechanisms and rates involved in
kerogen transformation by oxidative weathering are becoming increasingly
well-constrained in contemporary models of the global carbon cycle. Past
field studies have focused primarily on areas where high erosion rates
deliver large amounts of kerogen to earth’s surface, making the relative
importance of low-lying landscapes a key unknown in regional or global
scale estimates of kerogen recycling. The weathered residuum of
organic-rich sedimentary rocks serves as the parent material for many
soils. Therefore, some aspects of the chemical structure and biogeochemical
cycling of the soil organic matter are likely to be inherited from the
bedrock. We used a combination of solid-state 13C nuclear magnetic
resonance (NMR) spectroscopy, and carbon isotope techniques to describe
molecular and isotopic changes that occur throughout oxidative weathering
of marine kerogens, and the subsequent formation of modern soils, in two
outcropping Cretaceous mudstones of the Eagle Ford and Pepper Formations in
central, Texas. Increasing production of oxygenated functional groups was
coupled with reductions in characteristically abundant aliphatic components
of marine kerogens along the weathering profiles. Organic matter structural
parameters, derived from C–H dephasing NMR experiments, also provide the
basis for a novel weathering index that accounts for the degree of
post-sedimentary alteration of kerogen samples along the bedrock-soil
continuum. An uncertain future marked by climatic shifts in temperature
and/or precipitation and increased continental weathering and denudation
rates highlights the potential for enhanced vulnerability of kerogen, and
the need for molecular and isotopic tools for quantifying mechanisms and
rates involved in kerogen weathering.



*Bio: *
[image: image.png]



Dr. Longbottom is a biogeochemist focused on organic matter
characterization and cycling in soils and sedimentary rocks. His research
has investigated mechanisms of preservation of sedimentary organic matter,
as well as the diagenetic processes that represent important transformative
processes and rate modifiers in global biogeochemical cycles, specifically:
the dynamics of low-temperature “early” oxidation of sedimentary organic
matter, the post-depositional microbial oxidation of organic matter in
outcrop (soil formation), and the experimental thermal alteration of
organic matter (soils, biochar, and shales) through various pyrolysis
methods. He received his Bachelor’s in Environmental Geology from the
University of Dayton in 2010 and completed a Master’s in Geology at the
University of Cincinnati in 2012. He then completed a PhD in Geosciences
(Biogeochemistry and Organic Geochemistry) at Baylor University in 2017. He
is currently a postdoc in the Department of Life & Environmental Sciences
at the University of California, Merced investigating soil organic matter
dynamics under switchgrass agriculture and long-term effects of forest
restoration and management practices on soils and natural waters.




KJ, Manisha, and Anna

Organizers for Fall 2020: KJ Min, Manisha Dolui, Anna Jurusik
Faculty coordinator: Asmeret Asefaw Berhe

------
You can find the semester schedule below.

*date*

*speaker*

*topic*

  9/10

Shane Franklin

@ U of Delaware

Preferential flow plays an unknown role in the carbon cycle

9/17

Crystal Kolden

@ UC Merced

The cascading consequences of wildfire: understanding and mitigating
impacts to coupled human-natural systems

9/24

Allegra Mayer

@ UC Berkeley

Soil C sequestration potential in CA grasslands with compost amendments

10/1

Govind Dev Kumar

@ UGA

Salmonella's Trojan Horse Strategy to Evade Antimicrobial Stress

10/8

Charlotte Decock

@ Cal Poly, San Luis Obispo

Soil health and fertility assessment

10/15

Emma Hauser

@ U of Kansas

Integrated rooting system development and soil development structures
ecosystem nutrient dynamics

10/22

Cancelled

10/29

Mary Salcedo

@ Virginia Tech

Form and function of insect wing veins

11/5

Todd Longbottom

@ UC Merced

Oxidative weathering of ancient organic matter and formation of modern soils

11/12

Asmeret Asefaw Berhe @ UC Merced

Finding and securing grants for students & postdocs

11/19

Adeyemi Adebiyi

@ UC Merced

How much solar radiation does atmospheric mineral dust absorb?

11/26

Thanksgiving holiday



12/3

Yamina Pressler

@ Cal Poly, San Luis Obispo

Soil food webs and organic matter in fire-affected savanna ecosystems

12/10

AGU
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