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METHODS FOR THE DETERMINATION OF TOTAL ORGANIC CARBON (TOC) IN SOILS AND SEDIMENTS
Schumacher, B A. METHODS FOR THE DETERMINATION OF TOTAL ORGANIC CARBON (TOC) IN SOILS AND SEDIMENTS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-02/069 (NTIS PB2003-100822), 2002.
The overall objective of this task is to provide the Agency with improved state-of-the-science guidance, strategies, and techniques to more accurately and effectively collect environmental samples. Under this umbrella objective, research is being conducted to: (a) reduce/minimize the loss of VOCs during sample collection, handling, and preservation, (b) collect undisturbed surface sediments so that the effects of recent depositional events (e.g., flooding or dredging) can clearly be delineated as to their influence on the contamination concentrations present downstream (or where the sediments are deposited), and (c) to determine an effective method to effectively and efficiently separate asbestos in soils from the rest of the soil matrix while maintaining the integrity (i.e, no fiber size reduction) of the asbestos fibers.
Organic matter in soils and sediments is widely distributed over the earth's surface occurring in almost all terrestrial and aquatic environments (Schnitzer, 1978). Soils and sediments contain a large variety of organic materials ranging from simple sugars and carbohydrates to the more complex proteins, fats, waxes, and organic acids. Important characteristics of the organic matter include their ability to: form water-soluble and water- insoluble complexes with metal ions and hydrous oxides; interact with clay minerals and bind particles together; sorb and desorb both naturally-occurring and anthropogenically-introduced organic compounds; absorb and release plant nutrients; and hold water in the soil environment. As a result of these characteristics, the determination of total organic carbon (a measure of one of the chemical components of organic matter that is often used as an indicator of its presence in a soil or sediment) is an essential part of any site characterization since its presence or absence can markedly influence how chemicals will react in the soil or sediment. Soil and sediment total organic carbon (TOC) determinations are typically requested with contaminant analyses as part
of an ecological risk assessment data package. TOC contents may be used qualitatively to assess the nature of the sampling location (e.g., was it a depositional area) or may be used to normalize portions of the analytical chemistry data set (e.g., equilibrium partitioning).
The purpose of this document, as defined by the Ecological Risk Assessment Forum, is to answer the question of "What is the most appropriate method for soil and/or sediment TOC analyses and what factors should be considered when selecting the method?"