DIFFERENCES IN SEQUESTRATION AND BIOAVAILABILITY OF ORGANIC-COMPOUNDSAGED 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 sequestr ation 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, hut the rate and extent of sequestration varied markedly among the soils. Sequestra tion was largely complete in some soils in 120 days, but it extended f or longer periods in others. The extent of sequestration of the two co mpounds in the 16 soils was not highly correlated. The declines in bio availability in the soils were not highly correlated with the decrease s in extractability or the amounts of unextracted compounds, although soils in which the declines in bioavailability were greatest showed th e greatest declines in extractability. Because of the marked differenc es among soils, generalizations about the rate and extent of sequestra tion in soils are not yet possible.