University of Massachusetts |
UMass College of Natural Sciences |
UMass Geosciences
|
Steven Petsch Associate Professor of
Geosciences 265 Morrill Science Center Dept. of Geosciences UMass Amherst phone: (413) 545-4413 email:
spetsch<at>geo.umass.edu |
Life on our planet is constrained within bounds set by the transport
and transformations of the elements. Carbon cycling in particular plays a
central role in Biogeochemistry on a range of scales in time and space.
My research addresses what happens after deposition of organic matter in
sediment, and as it turns out, what happens is É a lot! Processes such as
diagenesis, chemical decomposition and the existence of metabolically active
microorganisms at the deepest and most extreme extent of our exploration lead
us to wonder why and how organic matter is preserved for millions of years in
rocks.
To address this, my research test the limits of what it means to
be refractory, labile or biologically available, by exploring the degradation,
dissolution and utilization of ancient organic matter in soils, aquatic systems
and the deep subsurface.
Research Interests:
á
transport and transformation of organic matter within and
between sedimentary and earth surface environments
á delivery of rock-derived
fossil organic matter to earth surface reservoirs such as soils, rivers and sediment
á long-term fate of
rock-derived fossil organic matter in the geologic carbon cycle
á microbe-rock-water
interactions in subsurface environments
á anaerobic biodegradation
of shale and coal organic matter associated with methanogenesis
á interactions between
chemical, physical, microbiological and human processes in sedimentary and
earth surface environments
á global biogeochemical
cycles of carbon, sulfur, oxygen
á analytical techniques for
characterization of natural organic matter in geologic materials
Courses taught:
á
GeoSci 285
Environmental Geology. This course uses
case-studies and real-world data to explore 3 fundamental environmental
challenges that are being addressed through Geosciences research: Water, Energy and Climate Change. (Fall
2011 syllabus)
á GeoSci 307 Geologic Writing. This course is required
for all Geology and Earth Systems majors.
In this course we discuss professional communication (resumes, cover
letters, email), scientific writing (referencing, scientific papers),
experiment design, hypothesis testing and data analysis. (Spring
2012 syllabus)
á GeoSci 517 Sedimentary Geochemistry. In this course we
review the fundamentals of carbonate chemistry, redox biogeochemistry,
diagenetic models of sedimentary reactive transports, global geochemical
cycles, and the chemical composition of marine sediments. (Fall 2010 syllabus)
á GeoSci 615 Organic Geochemistry.
This course explores the
chemistry of naturally-occurring forms of organic matter on the Earth,
including structure and nomenclature, analytical methods, biosynthesis, isotope
systematics, and applications in carbon cycling and paleoenvironmental
reconstruction. (Fall 2011 syllabus).
á NatSci 190H Global Challenges – Scientific Solutions.
This is the first-year
course in the iConS program (Integrated Concentration in Science), open through
competitive application to all majors in the College of Natural Science. This sources uses team-based,
inquiry-based learning to explore case studies of compelling societal
challenges and approaches towards their scientific solution. For more information, visit the iConS
program website www.cns.umass.edu/icons-program. (Spring 2011 syllabus).
Publications:
* denotes student
author/co-authored publications and presentations
Brantley,
S.L., Megonigal, J.P., Scatena, F.N., Balogh-Brunstad, Z., Barnes, R.T., Bruns,
M.A., van Cappellen, P., Dontsova, K., Hartnett, H., Hartshorn, T., Heimsath,
A., Herndon, E., Jin, E., Keller, C.K., Leake, J.R., McDowell, W.H., Meinzer,
F.C., Mozdzer, T., Petsch, S., Pett-Ridge, J., Pregitzer, K.S., Raymond, P.,
Riebe, C.S., Shumaker, K., Sutton-Grier, A., Walter, R., Yoo, K.. Thirteen
hypotheses to test how biology and weathering interact within the Critical Zone
(2011). Geobiology
9,140-165.
Allison,
M.A., Dellapenna, T.M., Gordon, E.S., Mitra, S., Petsch, S.T. (2010) Impact of Hurricane
Katrina (2005) on shelf organic carbon burial and deltaic evolution. Geophysical Research Letters 37, doi:
10.1029/2010GL044547.
Caraco, N.,
Bauer, J.E., Cole, J.J., Petsch, S.T., Raymond, P. (2010) Millenial-aged organic carbon
subsidies to a modern river food web. Ecology 91, 2385-2393. doi:
10.1890/09-0330.1
McIntosh,
J., Martini, A., Petsch, S., and Huang, R. (2008) Biogeochemistry of the Forest City
Basin coalbed methane play. International
Journal of Coal Geology, 76, 111-118. invited submission.
Formolo, M., Martini, A., and Petsch, S. (2008) Biodegradation of
sedimentary organic matter in the Powder River and San Juan Basins: The impact
of thermal maturity. International Journal of Coal Geology, 76, 89-97. invited submission.
Schillawski, S.J. and Petsch, S. (2008) Release of
biodegradable dissolved organic matter from ancient sedimentary rocks. Global
Biogeochemical Cycles, 184, 137-144.
Formolo, M.F., Salacup, J., Petsch, S.T., Martini, A.M., and
NŸsslein, K. (2008) A new model linking atmospheric methane sources to
Pleistocene glaciation via methanogenesis in sedimentary basins. Geology 36, p. 139-142.
Longworth, B.E., Petsch, S.T., Raymond, P.A., and Bauer, J. E.
(2007) Linking lithology and land use to sources of dissolved and particulate
organic matter in headwaters of a temperate, passive-margin river system. Geochimica et Cosmochimica Acta. 71,
4233-4250.
Waldron, P., Petsch, S.T., Martini, A.M., and NŸsslein, K.
(2007) Salinity constraints on subsurface archaeal diversity and methanogenesis
in sedimentary rock rich in organic matter. Applied and Environmental Microbiology 73, 4171-4179.
Go–i, M.A., Alleau, Y., Corbett, R., Walsh, J.P,
Mallinson, D., Allison, M.A., Gordon, E., Petsch, S.T., Dellapenna, T.S. (2007) The effects of Hurricanes Katrina and
Rita on the seabed of the Louisiana Shelf. SEPM The Sedimentary Record 5, 5-9.
Bolton, E.W., Berner, R.A., Petsch, S.T., and Wildman, R.A.
(2006) The weathering of
sedimentary organic matter as a control on atmospheric O2: II.
Theoretical Modeling. American Journal
of Science
306, 575-615.
Petsch, S.T.,
Edwards, K.J., and Eglinton, T.I. (2005)
Microbial transformations of organic matter in black shales and
implications for global biogeochemical cycles. Palaeogeography, Palaeoclimatology, Palaeoecology (special issue:
Geobiology) 219, 157-170. invited submission.
Raymond, P.A., Bauer, J.E., Caraco, N.F., Cole, J.J.,
Longworth, B.E., and Petsch, S.T. (2004)
Controls on the variability of organic matter and dissolved inorganic
carbon age in northeast U.S. rivers. Marine Chemistry (special issue honoring John
Hedges)
92, 353-366. . invited submission.
Wildman, R.A., Berner, R.A., Petsch, S.T., Bolton, E.W., Eckert,
J.O., Mok, U. and Evans, J.B. (2004)
The weathering of sedimentary organic matter as a control on
atmo-spheric O2: I. Analysis of a black shale. American Journal of Science 304,
234-249. [4]
Petsch, S.T.,
Edwards, K.J., and Eglinton, T.I. (2003) Abundance, distribution and d13C
analysis of microbial phospholipid-derived fatty acids in a black shale
weathering profile.
Organic
Geochemistry 34, 731-743.
Jaffe, L.A., Peucker-Ehrenbrink, B., and Petsch, S.T.
(2002) Effects of weathering of organic-rich sedimentary rocks on the mobility
of rhenium, platinum-group elements and organic carbon. Earth and Planetary Science Letters. 198,
339-353.
Petsch, S.T.,
Eglinton, T.I., and Edwards, K.J. (2001) 14C-dead living biomass:
evidence for microbial assimilation of ancient organic carbon during shale
weathering. Science,
292,
1127-1131.
Petsch, S.T.,
Smernik, R.J., Eglinton, T.I., and Oades, J.M. (2001) A solid state 13C
NMR study of kerogen degradation during black shale weathering. Geochimica et
Cosmochimica Acta, 65, 1867-1882.
Berner, R.A., Petsch, S.T., Beerling, D.J., Popp, B.N.,
Lane, R.S., Laws, E.A., Westley, M.B., Cassar, N. Woodward, F.I., and Quick,
W.P. (2000) Isotope fractionation and atmospheric oxygen: implications for
Phanerozoic O2 Evolution. Science, 287, 1630-1633.
Petsch, S.T.,
Berner, R.A., and Eglinton, T.I. (2000) A field study of the chemical
weathering of ancient sedimentary organic matter. Organic Geochemistry, 31, 475-487.
Petsch, S.T.
(1999) Comment on ÒCarbon isotope ratios of Phanerozoic marine cements:
re-evaluating global carbon and sulfur systemsÓ. Geochimica et Cosmochimica Acta, 63,
307-310.
Berner, R.A. and Petsch, S.T. (1998) The sulfur cycle and
atmospheric oxygen. Science, 282, 1426-1427.
Petsch, S.T.
and Berner, R.A. (1998) Coupling the geochemical cycles of C, P, Fe and S: the
effect on atmospheric O2 and the isotopic records of carbon and
sulfur. American
Journal of Science, 298, 246-262.
Fisler, D. K., Mackwell, S. J., and Petsch, S. T.
(1997) Grain boundary diffusion in enstatite. Physics and Chemistry of Minerals, 24,
264-273.
UMass
Biogeochemistry Laboratory
UMass
Stable Isotope Geochemistry Laboratory
photos from the field É
At a natural gas field in Kansas hosted in Pennsylvanian shales
and coals, sampling production water.
Dissolved gas and water chemistry reveal that this methane is largely
microbial in origin, and culture-dependent and –independent molecular
tools confirm the activity of Bacteria and Archaea in these rocks at great
depth in the subsurface.
Big scale and small scale view of our field site in eastern
Kentucky, where the Devonian New Albany Shale is exposed in a spectacular road
cut. My work at this site has
documented the chemical changes in shale organic matter that accompany rock
weathering (visible as transition from gray-black shale to light brown regolith
in upper left corner of photo on left).
On cm-scale, cores of unweathered rock are surrounded by lighter colored
weathered shale, in which the organic matter has been lost and degraded, and
new Fe- and S-bearing minerals are precipitating on the face of the outcrop.
A small stream near the base of the outcrop shown above reveals
copious amounts of thick, globular iron oxides. These are host to communities of iron-oxidizing bacteria
that help to break down the shale.
This watershed of small stream (left) in eastern upstate NY is
underlain by Ordovician and Devonian shales. Waters collected from this stream and its headwaters (on left,
being sampled by former graduate student Brett Longworth) contain particulate
and dissolved organic matter with very low amounts of radiocarbon. This tells us that organic matter from
the watershedÕs rocks is contributed to the modern aquatic carbon cycle. Radiocarbon analysis of benthic
invertebrates and zooplankton from here and downstream in the Hudson River also
show a depletion in radiocarbon, telling us that ancient rock-derived carbon is
being incorporated into the foodwebs of this ecosystem.