BIOAVAILABILITY OF POLYCYCLIC AROMATIC-HYDROCARBONS FROM A HISTORICALLY CONTAMINATED SEDIMENT CORE

To determine changes in bioavailability of selected polycyclic aromati c hydrocarbons (PAHs) with sediment aging, Lumbriculus variegatus were exposed for 4 weeks to sediment core sections taken from a contaminat ed lake. Core depths included surficial (0 to 4 cm), 4- to 8-, 12- to 16-, 28- to 32-, and 44- to 48-cm sections deposited from approximatel y 1899 to 1993, and were known to be historically contaminated with PA Hs. Bioaccumulation was maximal at the 12- to 16-cm depth (circa 1967) where sediment PAH concentrations were greatest. Accumulation was gen erally below detection limits in the 0- to 4-cm depths, even though se diment concentrations of some compounds were comparable to those at th e 12- to 16-cm depth where accumulation was great enough to generate a ccurate kinetics curves. Accumulation peaked at about 96 h, then decli ned over the remainder of the study for the lower-molecular-weight PAH s. For most higher-molecular-weight PAHs, accumulation peaked at about 2 weeks, then declined only slightly after 4 weeks. The differential bioavailability observed between surficial and at-depth core sections raises questions concerning the adequacy of results generated from tox icity and bioaccumulation tests routinely conducted with surficial sed iments.