ABSTRACT
After an environmental practitioner devises a sediment collection plan, determines the sediment collection location, collects sediments, properly packages the collected samples, and labels the sample package contents, the samples are carefully transported to an examination and testing laboratory. Such a laboratory is typically tasked with determining certain physicochemical characteristics of the sediments, in conjunction with toxicity testing or chemical analysis or inorganic or organic contaminants. This characterization should include measurement of certain parameters known to mediate the availability of contaminants in sediment (ASTM, 2000f). Bulk chemical concentrations alone should not be used to evaluate bioavailability (USEPA, 1998). The following parameters are generally measured:
• pH (porewater) • Ammonia (porewater) • Total organic carbon • Particle size distribution (e.g., percent sand, silt, and clay) • Percent water content • Salinity and hardness of porewater • Conductivity of porewater
Depending on the experimental design or study objectives, more extensive characterization may be necessary. Several additional characteristics that may assist in study implementation, data interpretation, or quality assurance/quality control (QA/ QC) (e.g., assessing sediment integrity, artifact production, optimal extraction, test procedures) include the following:
• Sediment biochemical oxygen demand (BOD) • Sediment chemical oxygen demand (COD) • Sediment oxygen demand (SOD) • Cation exchange capacity (CEC) • Redox (Eh) or oxidation-reduction potential (ORP) • Total inorganic carbon
• Total volatile solids • Acid-volatile sulfides (AVSs) • Simultaneously extracted metals (SEMs) • Metals • Synthetic organic compounds (pesticides, PCBs, PAHs, TCDD-dioxin) • Oil and grease • Petroleum hydrocarbons • Dissolved organic carbon (DOC) in the porewater
Note that many of the measurements of many sediment physicochemical characteristics use analytical techniques originally developed for soils and waters, and the literature should be consulted for details regarding the recommended methodology (Guy, 1969; Page et al., 1982; Plumb, 1981). The following sections provide the rationale for making each type of sediment physicochemical measurement, as well as a brief description of the measurement techniques for specific procedures.
