TABLE 4-1 Characteristics of Tools for Measuring Bioavailability

Tool

Process Studieda

Costb

Statusc

Physical/chemical characterization of the solid phase

General characteristics

• Organic carbon content

• Particle/grain size

• pH

• CEC

• Humic and fulvic acid content

Chemical characteristics of the solid (except particle size which is a physical characteristic).

$

Standard protocols available

Specific structures

• Characterization of carbonaceous and other solid phases using NMR, petrography, EA, IR/FTIR

Molecular characteristics of solid substrate.

$$ to $$$

Currently research grade for contaminated site application

Specific forms of contaminant bound to solids

• XRD and SEM

• XAS

• μL2MS

• SIMS

• NMR

• EPR

• XPS

Association and dissociation processes, including the roles of surface morphology, oxidation state, and compound or element location.

XRD, SEM—$$

All others—$$$

XRD, SEM—Standard protocols available; all others are research grade

Extraction of soils and sediments for inorganic contaminants

Extracts that change the solid phase

• Conventional

• Sequential

• TCLP, SPLP

Dissociation from the solid phase. Sequential extracts attempt to differentiate between forms of elements associated with different components or phases of the particle.

$

Some extracts in use and in regulations and thus standardized, but sequential extracts at research stage or in development

Passive approaches

• Passive extracts

• Pore water measurements with ASV or ion-specific electrode

• Exchangeable resins

Passive extracts determine dissociation from the solid phase. ASV and electrodes measure pore water concentrations. Exchange resins measure dissociation from the solid phase and physical flux to aqueous phase.

$(but need ICP-MS for exchangeable resins)

Research grade, no standard protocols developed; exchangeable resins better developed for sediments



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