Differences in sequestration and bioavailability of organic compounds aged in dissimilar soils

Phenanthrene and atrazine were aged for 200 days in sterilized samples of 16 soils that differed greatly in physical and chemical properties. At regular intervals during the aging period, the extent of sequestration was determined by measurement of biodegradation of the compounds by bacteria and the amounts extracted by a mild extraction procedure. Both compounds became sequestered in each of the soils, but the rate and extent of sequestration varied markedly among the soils. Sequestration was largely complete in some soils in 120 days, but it extended for longer periods in others. The extent of sequestration of the two compounds in the 16 soils was not highly correlated. The declines in bioavailability in the soils were not highly correlated with the decreases in extractability or the amounts of unextracted compounds, although soils in which the declines in bioavailability were greatest showed the greatest declines in extractability. Because of the marked differences among soils, generalizations about the rate and extent of sequestration in soils are not yet possible.