Acclimation of microbial communities exposed to p-nitrophenol (PNP) was measured in laboratory test systems and in a freshwater pond. Laboratory tests were conducted in shake flasks with water, shake flasks with water and sediment, eco-cores, and two sizes of microcosm. The sediment and water samples used in the laboratory experiments were obtained from the pond. After a 6-day acclimation period, PNP was biodegraded rapidly in the pond. When the pond was treated with PNP a second tine, biodegradation began immediately. The acclimation periods in laboratory test systems that contained sediment werg similar to that in the pond.

A method was developed to allow the use of volatile and nonpolar substrates in 14C most-probable-number tests. Naphthalene or hexadecane was sorbed to filter paper disks and submerged in minimal medium. The procedure reduced the volatilization of the substrates while allowing them to remain available for microbial degradation.

The distribution of KeponeO (chlordecone) in a sediment bed after various periods of continuous toxicant input to the overlying water column was determined in a laboratory system. Most of the Kepone was found to accumulate in the top 0.6 to 1.5 cm of sediment. A mathematical model was developed to predict Kepone concentrations with depth over time in the sediment. An equilibrium partition coefficient was determined from batch sorption tests and a molecular diffusion coefficient for Kepone was estimated from an empirical relationship between diffusivity and molecular weight. A computed Kepone distribution based on diffusion rates that decreased with depth and with incubation time gave the best fit to the observed data. We attribute the apparently faster rates in the upper sediment to mixing between interstitial and overlying water. Our results illustrate the value of models in conjunction with laboratory studies in defining the interactions of pollutants with sediment beds.

The influence of lugworms (Arenicola cristata Stimpson) and seagrass (Thalussia testudinum Koenig) on Keponem (chlordecone) distribution in sediment/water systems was examined. Radiolabeled Kepone was introduced into continuous-flow sediment/water systems, and the dissolved and sorbed concentrations of Kepone were quantified. Lugworm activity decreased the Kepone concentration in the water and increased its concentration in the sediment. The presence of seagrasses did not appreciably affect the concentration of Kepone in the water. Bioturbation appeared to be the prime factor in the transport of Kepone from water to sediment.