Current ecotoxicity testing needs among selected U.S. federal agencies.

U.S. regulatory and research agencies use ecotoxicity test data to assess the hazards associated with substances that may be released into the environment, including but not limited to industrial chemicals, pharmaceuticals, pesticides, food additives, and color additives.

Biodegradation of pyrene in sand, silt and clay fractions of sediment.

Microbial degradation is the dominant pathway for natural attenuation of PAHs in environmental compartments such as sediments, which in turn depends on the bioavailability of PAHs. The bioavailability of PAHs has seldom been studied at the sediment particle size scale. We evaluated biodegradation of pyrene by Mycobacterium vanbaalenii PYR-1 as a function of sediment particle sizes, and investigated the relationship between the rate of degradation on sand, silt and clay particles with their individual desorption kinetics measured with the Tenax extraction method.

Bioavailability of sorbed phenanthrene and permethrin in sediments to Chironomus tentans.

The availability of sorbed hydrophobic organic contaminants (HOCs) to benthic organisms is important for characterizing sediment toxicity. While many studies show a correlation between the rapid desorption HOC pool and bioavailability to benthic organisms, bioavailability of the slow or very slow desorption fraction is still poorly understood. In this study, Chironomus tentans were exposed to phenanthrene (PHE) or permethrin (PM) to derive biota-sediment accumulation factors (BSAFs) in a sediment that was sequentially desorbed with Tenax extraction or amended with a charcoal to modify the distribution of PHE and PM among the rapid (f(rapid)), slow (f(slow)) and very slow (f(vslow)) desorption pools.

Effect of activated carbon on microbial bioavailability of phenanthrene in soils.

Bioavailability is a governing factor that controls the rate of biological degradation of hydrophobic organic contaminants in soil. Among the solid phases that can adsorb hydrophobic organic contaminants in soil, black carbon (BC) exerts a particularly significant effect on phase distribution. However, knowledge on the effect of BC on the microbial availability of polycyclic aromatic hydrocarbons in soil is still limited.

Microbial availability of different forms of phenanthrene in soils.

Microbial degradation is the most important removal process for hydrophobic organic compounds (HOCs) in soil or sediment, and chemical availability is often a governing factor. However, the availability of HOCs in the sorbed forms is still a topic of debate. In this study, we applied rigorous kinetics analysis to the relationship between the freely dissolved concentration (Cfree) of phenanthrene (PHE) measured by polydimethylsiloxane (PDMS) fibers and its degradation by a PAH degrading bacterium PYR-1 under a range of soil conditions.

Effects of black carbon on pyrethroid availability in sediment.

Pyrethroids are widely used synthetic insecticides with the characteristics of high hydrophobicity and broad-spectrum aquatic toxicity. Many studies indicate that black carbon (BC) plays an important role in the bioavailability of hydrophobic compounds such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls in soils and sediments. However, the effect of BC on bioavailability of other compounds such as pyrethroids in sediments is less known.

Relationships between desorption intervals and availability of sediment-associated hydrophobic contaminants.

Availability is an important factor regulating the fate and toxic effects of hydrophobic organic compounds (HOCs) in soil and sediment. Many methods have been proposed for measuring HOC availability, but ambiguity exists in the selection of methods or method conditions. In this study, using pyrethroid insecticides as model HOCs, we measured their desorption kinetics from black carbon (BC)-amended sediments and used comprehensive statistical analysis to understand the dependence of the derived parameters on desorption intervals.

Measuring pyrethroids in sediment pore water using matrix-solid phase microextraction.

Pyrethroids are hydrophobic insecticides commonly used in both agricultural and urban environments. Their high toxicity to aquatic organisms, including benthic invertebrates, and detection in the sediment at many locations in California, U.S.

Using disposable polydimethylsiloxane fibers to assess the bioavailability of permethrin in sediment.

Pyrethroid insecticides are widely used in both agricultural and urban environments. Pyrethroids have been frequently detected in California, USA, stream bed sediments. Pyrethroids are strongly hydrophobic so their bioavailability is determined by their sorption to sediment.

Effect of suspended solids on bioavailability of pyrethroid insecticides.

Runoff and surface-water effluents commonly contain suspended solids. Adsorption to suspended particles and the associated dissolved organic matter (DOM) may significantly decrease the freely dissolved concentration of a hydrophobic compound and, hence, its availability to aquatic organisms. In the present study, we evaluated phase distribution and bioaccumulation of two synthetic pyrethroids, bifenthrin and permethrin, in water samples containing suspended solids from different source sediments.