A method has been developed to measure the swelling properties of concentrated natural organic materials in various organic liquids, and has been applied to various peat, pollen, chitin and cellulose samples. The swelling of these macromolecular materials is the volumetric manifestation of bulk sorption, i.e., sorption by dissolution (or partitioning) of the sorbed liquids into the macromolecular solid phase. Direct evidence for the existence of the category of sorbed materials has been obtained for soil organic materials by the present research; swelling in liquids has long been known in coals and polymers. Bulk sorbed molecules are thought to be inaccessible to direct biological attack, and may represent a continuing source of low-level rebound contamination of groundwater at a polluted site. Equilibration of bulk-sorbed molecules with liquid phases surrounding the particles is kinetically slow (diffusion limited) relative to sorption and fluid movement, and this sluggishness is probably responsible for some nonequilibrium sorption phenomena seen in soil column flow experiments. Molecules with molar volumes greater than about 93 cc/mole appear to be strongly excluded from sorption inside the soil organic materials studied in the work. In contrast, cellulose excluded molecules with molar volumes greater than about 88 cc/mole. Extensive bibliographies included.

Cover title. "July 1991" "EPA/600/2-91/033" "EPA contract no 68-C8-0025" PB91-217406 Includes bibliographical references.