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Dr. Laodong Guo Associate Professor 228-688-1176 (Voice) |
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Current Research
Projects from NSF
1) Composition and Fluxes of Organic
Carbon Species from the Yukon River Basin (NSF-EAR#0403596)
Funded by National Science
Foundation (NSF) Integrated Carbon Cycle Research Program (2004-2007, Principal Investigator).
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This project seeks to understand the biogeochemical processes governing the composition, reactivity, transformation and flux of organic carbon species, including dissolved, colloidal and particulate organic carbon from the Yukon River Basin. Being heavily influenced by ice, snow and permafrost dynamics, the Yukon River Basin, a pristine river basin, is sensitive to environmental and climate change. With up to 50% of the world's soil organic carbon stored in the northern region, the role of arctic/subarctic rivers in the remobilization of organic carbon and thus marine and global carbon cycles is far more important than previously recognized. Due to the Yukon River's remoteness and the extreme weather conditions, the composition and reactivity of organic carbon species entering the ocean via the Yukon remain largely unknown and the riverine carbon export flux is poorly quantified. Observations will include phase partitioning of organic carbon between dissolved, colloidal and particulate phases, and concentrations, optical properties, molecular and isotopic (d13C, d15N and d14C) composition and reactivity of size fractionated organic carbon. Field and laboratory experiments will also be carried out to examine the extent to which organic carbon fractionates during ice formation and how the fractionation drives carbon partitioning and transformation. This project will be among the first to combine both molecular-level and basin-scale observations to understand temporal and spatial variations in composition and flux of organic carbon species in a large but pristine and less anthropogenically influenced river basin. The proposed research will provide valuable data for comparative studies between drainage basins, and provide inputs for and contribute effectively to the integrated carbon cycle program and model development, and the understanding of the environmental impacts from a changing climate. To learn more about global carbon cycle, click here. See also IARC research highlights. |
2) Collaborative
Research: Th(IV) and Pa(IV, V) binding to exopolymeric acid and polysaccharides
in marine environments (NSF-OCE#0350758)
Funded by the National
Science Foundation (NSF) Chemical
Oceanography Program (2004-2008).
Abstract: Th(IV) and Pa(IV,V) isotopes are important proxies in
oceanographic investigations, such as, for tracing particle dynamics and
particulate organic matter (POC) fluxes out of the euphotic zone through the
use of 234Th/POC ratios, and for studying boundary scavenging,
paleoproductivity and ocean circulation through the use of 231Pa/230Th ratios.
Even though almost routine, these approaches rely on often poorly constrained,
empirically determined and variable isotope ratios or ratios to POC. Previously
conducted laboratory and field investigations suggest that Th(IV) removal could
be controlled through binding by exopolymeric acid polysaccharide (APS) rich
biomolecules, potentially produced by both phytoplankton and bacteria. However,
we believe that Pa(V) present in ocean water must first be reduced to Pa(IV) by
organic biomolecules before efficient binding to solid phases can occur, and
that the most efficient binding would occur to APS-rich biomolecules produced
by phytoplankton species such as diatoms, prymnesiophytes and cyanobacteria. In
this study, the team of scientists at Texas A&M Research Foundation and the
University of Alaska Fairbanks Campus will investigate the possible
fractionation mechanisms between Pa(IV,V) and Th(IV) in the ocean. It is
essential to understand such a mechanism, since the Pa/Th ratio is frequently
used as a proxy in oceanographic applications. The proposed interdisciplinary
experimental approaches will require instrumental approaches for
characterization studies, in combination with controlled laboratory and field
experimentation. Laboratory studies consist of uptake experiments to a number
of substrates, including purified APS harvested from phytoplankton and
bacterial cultures to be used in Th(IV) and Pa(IV,V) binding assessments. The
most important analytical task will be to better characterize, both chemically,
in terms of molecular composition, and physically, in terms of surface
activity, the newly discovered strongly Th(IV) complexing APS of ~13 kDa
molecular weight, found in particulate and colloidal material collected from
the Gulf of Mexico, Atlantic and Pacific Ocean and the South China Sea. The
field program in this study will include collection and extraction of diverse
types of organic matter for use in laboratory studies, as well as the
determination of temporal and spatial variations of radiochemical and
biochemical parameters.
3) Flux and transformation
of organic carbon across the eroding coastline of northern Alaska (NSF-OPP #0436179).
Funded by the National Science Foundation (NSF) Arctic
System Science/Office of Polar Program
(2005-2008),
through collaboration with Drs. Chien-Lu
Ping and
Yuri Shur at UAF and Torre Jorgenson at ABR
Inc., Fairbanks (meet these
PIs). Our project is part of SNACS (Study of the
Northern Alaska Coastal System) Program, a contribution to the study of
environmental arctic change (SEARCH).
This proposed research addresses
scientific questions through four main components designed to: (1) characterize
the abundance, composition, and age of soil OC and the abundance and structure
of ground ice in relation to geomorphic environments, (2) estimate the total OC
flux along the entire Alaskan Beaufort Sea coast and develop empirical models
based on terrain and oceanographic factors to assess the vulnerability of the
coasts to increased erosion resulting from a longer fetch due to sea-ice
retreat, (3) to determine the biogeochemical transformation and bioavailability
of OC associated with various dissolved and particulate forms as they cross the
land/sea interface through field study and controlled laboratory
experimentation; and (4) integrate our results to the pan-arctic scale through
international collaboration with the Arctic Coastal Dynamics program. The study
will involve extensive sampling at 50 random locations along the entire coast
to develop precise estimates of OC abundance and flux with explicit confidence
limits. Intensive sampling at three key sites that represent the dominant
coastline types will be conducted to evaluate the transformation of the eroded
OC. Three additional secondary sites will be established to broaden the
monitoring to other coastline types and to involve local communities in the
assessment of coastal changes.
Broader Impacts: This project will provide information
critical to understanding of biogeochemical consequences of environmental
changes in the northern
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Export of old terrigenous organic matter across the arctic land/ocean interface: Evidence from estuarine sedimentary organic carbon 14C ages along the Siberian Arctic coast (from Guo et al., 2004, Global Biogeochemical Cycles, 18(1), GB1036, pdf file). |
Increasing coastal erotion under a changing climate in the North What are the impacts and biogeochemical consequencies of climate and environmental change in the north? |
1) Interactions of Th(IV) with organic compound classes of marine
organic matter (1999-2003)
A NSF Supported project (NSF-OCE #9906823): Th-234 has been widely used as a tracer to quantify the
fluxes of organic carbon export from the euphotic zone to the deep ocean in
many global research projects, such as Joint
Global Ocean Flux Study (JGOFS). Particulate organic carbon
(POC) fluxes are calculated as the product of the 234Th export flux times the
POC/234Th ratio. However, POC/234Th ratio in suspended and sinking particles
are not constant. It varies with different particle sizes, water depths, and
study areas. Understanding factors controlling the POC/234Th ratio in the ocean
is of paramount importance in global carbon cycle study and thus the climate
changes in the time scale of human concern.
The major objectives of the
proposed work are: 1) To collect colloidal, suspended and sinking particles
from marine environments for laboratory studies and to quantify the
relationships between the abundance of polysaccharide enriched marine
aggregates and Th(IV) deficiency (See photos of R/V Gyre 2000
and 2001Cruises); 2) To
conduct controlled laboratory experiments to investigate the interactions of Th
(IV) with individual organic compound classes of marine organic matter to
elucidate whether complexing of Th is a non-selective physicochemical process
(less likely) or organic ligand dependent (most likely); 3) To characterize the
bulk chemical, surface chemical, and isotopic composition of marine organic
matter to determine their acid-base and ligand properties and the nature of
organic or inorganic functional groups that Th (IV) tracks; 4) To construct an
improved scavenging model which relies on information on Th(IV) sorption to
strong surface active and non-surface active ligand groups in particulate and
colloidal organic matter. Experimental and model results will be used to
recommend improvements in the use of POC/234Thp ratios for POC flux
determinations.
2) Role of natural organic matter in
governing the bioavailability of potentially toxic metals to estuarine bivalves (2001-2004)
Supported by NOAA-Sea Grant: Bivalves have been extensively used as bio-indicator
organisms in environmental assessment and monitoring programs to assess the
bioavailable contaminant concentrations in coastal environments (e.g., NOAA's
NS&T program). Natural dissolved organic matter (DOM) is ubiquitous and is
a potentially nutritious food source for bivalves. However, the presence of DOM
may significantly alter the bioavailability and biogeochemical cycling pathways
of many trace metals in marine environments. The role of natural DOM in
governing the bioavailability of potentially toxic metals to bivalves is not
well understood and has rarely been tested. To better use bivalves as pollution
indicator organisms, a thorough understanding of metal uptake pathways and
mechanisms as a function of the quality and quantity of DOM is sorely needed.
The primary objectives of this research is to determine how DOM affects the
bioavailability of metals to bivalves, including oysters (Crasostrea
virginica) and mussels (Ischadium recurvum), and whether DOM can be
directly used as a food source by these bivalves using radiotracers and
molecular probes in controlled laboratory experiments. Our research will
provide crucial information applicable to environmental assessment and
monitoring.
This is a research project supported by the NOAA-Sea Grant between
2001-2004, collaborating with Professor Peter Santschi
and Professor Sammy Ray in the
Laboratory for Oceanographic and Environmental Research (LOER) at the Texas A&M University at Galveston. My previous SeaGrant
supported project, namely "Bioavailability
of colloid-associated metals to estuarine bivalves" was completed during
1998-2001.
Ssee our publications in Environmental Science and
Technology (Guo et al. 2001, pdf)
and Marine
Environmental Research (Guo et al., 2002, pdf).
3) Nature and fluxes of
nutrients and organic matter from Yukon River Basin
Principal investigator, Supported by Japan Frontier Research System for Global
Change/IARC: The Yukon River is one
of the largest rivers draining into the Arctic with an annual discharge of more
than 200 billion m3 of freshwater and ~60 million tons of suspended sediment,
and contributes ~8% of the total freshwater input to the Arctic Ocean.
Recent evidence shows that the polar region and the northern ecosystem are
quite sensitive to global and regional climate and environmental changes.
Therefore, environmental and climate changes in the northern arctic and thus
increasing freshwater flow and organic matter inputs from the Yukon River Basin
will have profound impacts on the ecosystem and biogeochemical cycles in the
Bering Sea and Arctic Ocean. However, due to its remoteness and the
extreme weather conditions, the
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4) Radiocarbon and molecular characterization
of organic compound classes of dissolved organic matter in the ocean
Dissolved organic carbon (DOC) is the largest
organic C pool in the ocean and plays an important role in the global carbon
cycling. However, understanding the cycling of DOC in the ocean remains a major
challenge to oceanographers despite recent advances in marine organic carbon
cycling. To further explore the detailed biogeochemical pathways of different
organic components and to better understand the complex cycling of DOC in the
ocean, measurements of isotopic composition in different organic compound
classes are sorely needed, as are the chemical and molecular characterization
of different size or molecular weight fractionated DOC components.
The major objectives of the proposed research are: 1) To collect large
quantities of high molecular weight (HMW) dissolved organic matter from
seawater for chemical and isotopic characterizations, using cross-flow
ultrafiltration techniques; 2) To characterize elemental composition, major
organic compound classes and individual organic molecules using elemental
analysis, pyrolysis-GC/MS and liquid extraction techniques; 3) To determine
radiocarbon (14C) and stable carbon (d13C) and nitrogen (d15N) isotope
signatures of major organic compound classes, amino acids,
carbohydrates, total lipids, and acid-insoluble fractions in isolated HMW DOC
fractions; 4) To elucidate how chemical composition and isotope signatures of
the compound classes reflect their production and decomposition processes in
the ocean and to better understand the biogeochemical pathways and turnover
times of each compound class, whose geochemical behavior could be significantly
different from that of the total DOC pool.
This is a collaborative proposal declined by the National
Science Foundation (NSF) - Ocean
Science Division.
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Research collaborators
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Name |
Department |
Affiliation |
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Oceanography and Marine Sciences |
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Laboratory for Isotope Geology |
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Department of Oceanography |
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Department of Oceanography |
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Pacific Oceanological Institute |
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Dr. Xiaoling Ding |
Environmental Sciences |
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Soil
Sciences |
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Dr. Chin-Chang Hung |
Oceanography |
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Dr. Robie Macdonald |
Marine Environmental Quality |
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Water Chemistry, GEES |
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Major Equipment
Stable isotope mass spectrometer
system (Finnigan MAT 252);
Total organic carbon and nitrogen
analyzer (Shimadzu TOC-V) with capability
of measuring DOC and TN;
Canberra
gamma counting system, with ultrahigh purity Ge well detector and multichannel
analyzer;
CDS Model 1000 Pyrolyzer with a
Model 1500 GC interface;
Yvon FluoraMax-3 Spectroflurometer;
Aglient 8453
Spectrophotometer;
Finnigan MAT Delta Plus GC
Combustion III Unit with Carlo Erba Elemental Analyzer, VG Series II Dual Inlet
Mass Spectrometer;
Cross-flow ultrafiltration
systems (e.g., Millipore Proflux
M-30 and Amicon DC-10 systems);
A field flow fractionation system
(SF 1000 SPLITT) (Postnova Analytics)
Ultra-pure water system,
ultracentrifuge, freeze dryer, clean benches, auto balances, etc.
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This page Copyright © 2001-2006 Laodong
Guo.
Last updated Jan 10,
13:08:32 AKST 2006