Peat

Photo: Drainage ditch in 7m of peat with woody

peat at the top, near Palangkaraya, Central

Kalimantan, Indonesia in February, 1987. Photo

courtesy of Sandra Neuzil, USGS.

What is Peat?

Peat is a soft organic material consisting of partly decayed plant and, in some cases, deposited mineral matter. Peat mires cover nearly 3 percent of the earth’s surface (DNPI, 2010) and are a carbon sink (natural carbon sequestration) and a potential source of methane, carbon dioxide, and nitrous oxides (greenhouse gases), should they be drained, flooded, oxidized, or destroyed by fire. Many peat occurrences are undergoing rapid change or loss, so it is important to understand their contribution to the biosphere and hydrosphere, as well as their role in global carbon and climate cycles.

In peat, the floral composition, geochemistry, geometry, and relationships to sediments are influenced by depositional setting factors including climate, basin tectonics, sediment yield and dispersal patterns, and coastal dynamic processes (Coleman and Whelan, 1977; Schweinfurth, 2003; Cecil and Neuzil, 2009). Additionally, nutrient supply, acidity, bacterial activity, temperature and redox potential are significant factors (Thomas, 2002). ASTM originally defined peat (1969) as organic matter having less than 25 percent ash on a dry basis; for more than 25 percent ash yield, the proper term is peaty material. Definitions and analytical methods were examined and modernized (Jarrett, 1983) and are continuously reviewed and upgraded (ASTM, 2011a; 2011b).

Peat is generally classified into two end member hydrologic types: ombrogenous (owing origin to rainfall) and topogenous (owing origin to both surface and groundwater regimes). Modern definitions (Anderson, 1983; Gore, 1982; Jackson, 1997; Thomas, 2002 and Wust and others, 2003) of various types of peat environments include:

Bog – An ombrotrophic peat-forming ecosystem

Bog forest – Ombrotrophic forested vegetation, generally an upper story of coniferous trees with a ground layer of sphagnum moss

Fen – A topogenous rheotrophic ecosystem in which the dry season may lower the water table below the surface of the peat

Floating swamp – Develops around the fringes of lakes and estuaries and extends out into open water. In tropical areas, these can be thick and laterally extensive

Humus – Highly degraded peat; the humification process (transforming organic matter into humus) is active and yields a dark, spongy, organic matter of uniform appearance

Marsh – A topogenous wetland characterized by floating vegetation of various kinds (reeds, sedges, etc.), but controlled by rheotrophic (flowing) hydrology that rarely forms peat

Mire – General term for peat-forming ecosystems of all types

Peat swamp forest – A forest growing on peat that is formed from the partially decomposed forest plant matter, common in tropical Indonesia and Malaysia

Swamp – A rheotrophic ecosystem where the dry season water table is almost always above the surface of the sediment. This aquatic ecosystem is dominated by emergent vegetation (trees, shrubs)

References

A list of references [.docx] associated with the above overview of peat is available.

Sandy Neuzil
Lead Scientist

Charles Oman
Lead Scientist

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Provisional Peat Database

Disclaimer: The data you have secured from this USGS Database are provisional and subject to revision. The data are released on the condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.

Introduction to the Provisional Peat Database

Two EXCEL files contain provisional U.S. Geological Survey (USGS) data on peat and related plant/sediment/water chemistry. Samples are largely from the U.S., but samples were also collected in other countries. PEATDATA.xlsx covers mostly the United States and a few samples from six other countries. INDONESIA_PEATDATA.xlsx contains data only for Indonesia. The files present much of the information gathered in previous investigations by USGS researchers and laboratories on the occurrence and chemistry of peat. The intent of these provisional databases was to capture and preserve older USGS peat information in a common, digital format for easier use. Original descriptive terms by the sample collectors were retained and, as a result, their terms may not necessarily match modern definitions and usage.

You can view the distribution of data as maps by State or country, download the EXCEL files, and download a bibliography related to these samples. Please download the README file [.docx] for additional information on attribute definitions and Table 1 [.docx] for analytical methods.

Downloading the Data

Samples in the two provisional EXCEL databases include samples of peats, marls, water, peat substrate, and vegetation. PEATDATA.xlsx covers mostly the United States (U.S.) and a few samples from six other countries. INDONESIA_PEATDATA.xlsx contains peat, water, and sediment data only for Indonesia. Much of the older U.S. information is imprecisely located, with original sampling locations indicated by step and measures, but many locations have been estimated or semi-verified by consulting online topographic quadrangles for the existence of peatlands and local landmarks. Samples should be located within a mile or less of their actual locations (Sample Location Maps), except for locations that represent the corner of a topographic quadrangle that were unable to be refined and thus have an attribute noting the coordinates as being the southeast corner of a quadrangle (SECQ).

Sample attributes include location, thickness/depth if known, and other descriptive information; major-, minor-, and trace-element concentrations on an as-determined analytical basis; and ultimate and proximate analyses, forms of sulfur, gross calorific value on a dry analytical basis; moisture content; ash deformation temperatures and free-swelling index (see README file [.docx] for a complete list). The moisture values contained in PEATDATA.xlsx and INDONESIA_PEATDATA.xlsx do not reflect consistent conditions for sample collection or handling and thus are not particularly useful. Major-, minor-, and trace-element geochemistry are determined on peat ash (quite often from older semi-quantitative methods, such as six-step emission spectroscopy). Censored values are indicated in the database by less than (<) and greater than (>) symbols. A few elemental values are on a whole-sample (not ash) basis and these are indicated in the database.

The chemical fields within the database are shown in Table 1 [.docx] with their respective analytical methods, the sample analytical basis, and references in which the methods are described. ASTM currently has thirteen standard test methods or practices specifically for peat (ASTM, 2012), but the chemical analytical methods are generally the same as those used for coal, which are the ASTM methods cited in Table 1 [.docx].

Complete List of Provisional Peat Database Materials:

README [.docx]

PEATDATA.xlsx

INDONESIA_PEATDATA.xlsx

Sample Location Maps

Table 1 - Chemical Parameters and Analytical Methods [.docx]

Peat Bibliography

Peat publications with USGS researcher involvement or authorship, compiled largely from the sample collector names listed in the PEATDATA.xlsx database, are included in a bibliography [.docx]. Although not a comprehensive list of all peat citations, it is a fairly complete list of reports related to past work conducted by the Eastern Energy Resources and Eastern Minerals and Environmental Resources Science Centers at the USGS.

Acknowledgments

USGS researcher, Cornelia C. Cameron (1911-1994), in a New
Hampshire marsh in 1989. Photo courtesy of John Jackson.

References

ASTM, 2012, search by keyword = peat, Accessed 1/3/2012, http://www.astm.org/Standard/index.shtml

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USGS Links

Hydroecology of Flowing Waters

Minerals - Peat as a Commodity

National Wetlands Research Center

Patuxent Wildlife Research Center - Wetlands

South Florida Information Access

Terrestrial Wetland Global Change Research Network

USGS National Water Summary - Wetlands

External Links

Maine Geological Survey - Ecological Reserve System