Students in SSC 601/801 are required to present a seminar during the Crop and Soil Science Seminar time.
For April 3, we have three presentations:

Ben Atkins (3:10-3:35 PM) – Characterizing the effect of pH and molecular structure on the reactions of catechol and hydroquinone with birnessite

Marissa Dellinger (3:35-4:00 PM) – Chronosequence of carbon accretion in Hyde County

Karina Lenko (4:00-4:25 PM) – A little less mud on the tires: How soil properties and prevention methods impact track-out

Benjamin Atkins
Graduate Research Assistant, M.S. Soil Science
Advisor: Dr. Hui Li
Characterizing the effect of pH and molecular structure on the reactions of catechol and hydroquinone with birnessite

ABSTRACT

The mechanisms underlying the formation and stability of soil organic matter (SOM) remain
largely unclear and are dependent on a host of environmental and chemical factors. Yet, as the
role of soils in carbon storage and cycling is increasingly recognized, it is this information that
will be crucial. The polyphenol theory is one commonly accepted pathway for the formation of
SOM, and has been shown to occur biotically or abiotically. Birnessite is a layered Mn-oxide
that is ubiquitous in soils and is capable of catalyzing polymerization reactions of polyphenols.
Previous research has not fully elucidated the effect of pH and molecular structure of the parent
materials on such reactions, nor have they characterized the degradation products formed. In an
effort to contribute to this understanding, we performed batch experiments at three
environmentally relevant pH conditions to examine the reaction of birnessite with the
polyphenols catechol and hydroquinone. Spectroscopic analyses were employed to glean
information on the formation of humic-like polymers and simple degradation products. These
analyses complemented measurements of dissolved Mn and organic carbon which provide
insight into the reaction progress under varying conditions. Catechol reduced and dissolved the
mineral to a much greater extent, and this dissolution was greater at low pH. Correspondingly,
more carbon was lost from the system during catechol reactions compared to hydroquinone,
suggesting more complete oxidation of catechol-C to inorganic forms (e.g. CO2). Spectral data
supports the concomitant formation of humic-like polymers and aliphatic degradation products
which vary according to pH and compound used. Overall, the results show a clear impact of pH
and molecular structure on the interaction of polyphenols with birnessite.

Marissa Dellinger
Graduate Research Assistant, M.S. Soil Science)
Advisor: Dr. Matt Ricker

Chronosequence of Carbon Accretion in Hyde County

ABSTRACT

Increased soil salinity due to rising sea levels has reduced the productivity of agricultural fields
along the Albemarle-Pamlico Sound. Fields have been abandoned in the past century as saltwater
intrusion progressed, first from areas closest to the sound and then those further inland. Some
former fields were reclaimed as forests, but inundation with brackish water creates an
unfavorable environment for most terrestrial plant species resulting in Marshes and Ghost
Forests that develop as salinization pushes further inland. This coupled with continuous
inundation from brackish water slows litter decomposition and allows organic matter to
accumulate on the soil surface. Elevation in coastal wetlands is a function of both mineral
sedimentation and organic matter accretion, however, in these newly forming marshes, organic
matter accretion drives that elevation. As accretion occurs these areas function as a buffer to
lessen the severity of storm surges, but rising sea levels could outpace and submerge them. To
determine if natural accretion on abandoned farm fields is keeping pace with sea level rise, we
sampled 18 sites (to 200 cm depth) across 3 transects along the Albemarle-Pamlico peninsula.
Each transect contained three distinct ecosystem types: tidal marsh, ghost forest, and forest, used
for biosequence comparisons. Soil samples were analyzed by horizon to determine physical and
chemical characteristics. Preliminary results showed that mean organic horizon formation over
mineral subsoil was significantly (p-value: 0.02) higher in marshes (16.2 cm) compared to ghost
forests (14.0 cm) and forests (8.1 cm) however most organic layers did not meet the depth
requirements to be classified as organic soils (40 cm, Histosols). Carbon-to-nitrogen ratios in
recently formed organic horizons averaged below 24:1, suggesting carbon depletion in all
ecosystems. Further data analysis is ongoing to quantify the total accretion and ability of these
abandoned fields to act as buffers against future sea level rise.

Karina Lenko
Graduate Research Assistant, M.S. Soil Science
Advisor: Dr. Josh Heitman

A little less mud on the tires: How soil properties and prevention methods impact track-out

ABSTRACT

In North Carolina, regulations are in place to prevent the tracking of mud from construction sites
onto public roadways. These regulations, set forth by the North Carolina Department of
Transportation, require construction projects to install a stone exit or an approved track-out control
mat to prevent track-out; however, they offer no site-specific guidance. Limited research has been
conducted on the effectiveness of track-out prevention methods and how soil properties such as
texture, water content, and mineralogy may impact their effectiveness. Three track-out prevention
methods were tested: a standard stone exit, a RubberForm Trackout Control Mat, and a FODS
Trackout Control Mat. Three soils were tested: a sandy loam, a silty clay, and a sandy clay loam
from the Triassic Basin. Lab testing was conducted to assess the Atterberg limits of the soils and
their stickiness over a range of water contents. Each soil’s two stickiest water contents were chosen
for field testing. Mud was applied to sections of tire, and they were then secured to a vehicle tire.

The muddy tire sections were weighed before and after making four contacts with a given track-
out prevention method to measure the percentage of mud removed. No single prevention method

performed best under all conditions. All prevention methods varied in their average mud removal
percentages from texture to texture and within the same texture under different water contents.
Results highlight the influence of soil properties on track-out prevention methods. Additionally,
these results emphasize the need for more site-specific regulations for track-out. Providing
contractors with more information regarding how soil properties impact track-out will better equip
them to make decisions regarding the degree of wheel cleaning required at a site, ultimately
enabling them to not only make more informed decisions but also to keep roads cleaner and safer
for North Carolina drivers.