Peter F. Landrum

Acute mortality of anthracene-contaminated fish exposed to sunlight

Abstract Acute mortality of bluegill sunfish (Lepomis macrochirus) dosed with anthracene at 12.7 μg/l and exposed to natural sunlight conditions was observed during a study of anthracene fate in outdoor channel microcosms. No mortality was observed under control conditions (natural sunlight and no anthracene). Fish survived when held in the shade downstream of sunlit contaminated water, arguing against mortality due to toxic anthracene photoproducts in the water. Fish held 48 h in anthracene contaminated water (≈ 12 μg/l), in a shaded channel, died when placed in clean water and exposed to sunlight. After 144 h depuration in darkness, fish anthracene concentrations had decreased to pre-exposure concentrations and no mortality was observed when fish were subsequently exposed to sunlight. This observed photo-induced toxic response in anthracene contaminated fish may represent a significant environmental hazard of polycyclic aromatic hydrocarbons in aquatic environments.

Toxicokinetics of organic xenobiotics in the amphipod, Pontoporeia hoyi: role of physiological and environmental variables

Abstract The accumulation and elimination kinetics of selected polycyclic aromatic hydrocarbons and polychlorinated biphenyl congeners were were determined for the amphipod, Pontoporeia hoyi, the major benthic invertebrate in the Great Lakes. Rates measured during the course of several field seasons, along with environmental and physiological variables, indicated that for compounds less water soluble than anthracene, the uptake rate constant (Ku) is inversely proportional to the mass of the organisms and directly proportional to experimental temperature. The role of temperature was again limited to the more water insoluble compounds. The depuration rate constant (Kd) was inversely proportional to the octanol-water partition coefficient, the mass of the organism, and the lipid content of the organisms. Kd was directly proportional to temperature, although the effect of temperature was again insignificant for the very water soluble biphenyl. The magnitude of the thermal effect was lower during the summer and early fall when the lipid content of the organisms was high. Both the uptake and elimination kinetics are dependent on a variety of physiological and environmental factors. The kinetic parameters must be normalized for the various factors before comparisons of kinetics in P. hoyi between collections at different times during the year and different sampling sites can be made.

The Role of the Zebra Mussel, Dreissena polymorpha, In Contaminant Cycling: II. Zebra Mussel Contaminant Accumulation from Algae and Suspended Particles, and Transfer to the Benthic Invertebrate, Gammarus fasciatus

To determine the contribution of ingested material to zebra mussel contaminant accumulation, contaminant assimilation efficiencies (fraction of the total contaminant exposure that is accumulated into tissue, AE) from spiked algae and suspended sediment particles were measured for benzo(a)pyrene, the insecticide DDT, and selected polychlorinated biphenyl (PCB) congeners. Contaminant transfer from zebra mussel feces to the benthic invertebrate, Gammarus fasciatus, was determined by measuring AE from PCB contaminated mussel feces to gammarids. Further, mussel contaminant AE values coupled with physiological and environmental parameters were used in a steady-state model to examine the relative importance of the algal, suspended sediment, and water-borne exposure routes for a representative organochlorine compound, hexachlorobiphenyl (HCBP). The relative accumulation via the fecal and water exposure routes were modeled for gammarids. Mussel AE values for contaminant accumulation were greater from algae than from suspended sediments. Model estimates indicated that when contaminant concentrations in the water were near detection limits, dietary exposure was the primary route of contaminant accumulation (61.5% of the total contaminant concentration). Water was the most important route of contaminant exposure (89.5% of the total contaminant concentration) when contaminant concentrations in water were 10 times greater than the compound detection limit. Suspended sediment was the major dietary source of contaminants at all water concentrations. % AE for zebra mussel feces to gammarid transfer were high—79.0 and 89.4% for hexachlorobiphenyl and tetrachlorobiphenyl respectively—but not statistically different. Model estimates indicated that the dietary route of exposure was the primary source of PCB exposure for gammarids and indicated a potential for PCB biomagnification in the mussel-based detrital food chain. Results suggest that zebra mussels have the potential to change contaminant cycling in the Great Lakes by rerouting dissolved and paniculate bound contaminants through zebra mussel food chains with possible biomagnification in upper trophic levels.

The Role of the Zebra Mussel, Dreissena polymorpha, in Contaminant Cycling: I. The Effect of Body Size and Lipid Content on the Bioconcentration of PCBs and PAHs

The zebra mussel, Dreissena polymorpha, a recent invader to the Great Lakes, may influence contaminant cycling by bioconcentrating high levels of hydrophobic contaminants in its tissue. To better understand zebra mussel bioconcentration and ultimately, contaminant cycling, we measured bioconcentration factors (BCFs) and kinetic parameters for accumulation of polychlorinated biphenyl and poly cyclic aromatic hydrocarbon congeners for two size classes of mussels and for a pre-spawning (high lipid) and post-spawning (low lipid) mussel population. High lipid, pre-spawning mussels had greater BCFs and faster uptake kinetics for the highly hydrophobic compounds, i.e, hexachlorobiphenyl and benzo(a)pyrene, than the low lipid, post-spawning mussels. BCFs and uptake kinetics determined for the less hydrophobic compounds, i.e., tetrachlorobiphenyl and pyrene, were not measurably influenced by differences in lipid content. Small mussels (15 mm shell length) had higher BCFs and faster uptake kinetics for all compounds compared to larger (21 mm shell length) mussels. Contaminant elimination was not affected by size or differences in lipid levels. For both lipid levels and size classes of mussels, the BCFs were positively correlated with compound log octanohwater partition coefficient. Hence, the lipid affinity of a compound can be a good indicator of mussel contaminant accumulation. Potentially large contaminant concentration in zebra mussels may alter contaminant cycling in the Great Lakes by increasing contaminant transfer to mussel predators. Selective predation on small, pre-spawning (high lipid) mussels may present a greater hazard to predators than predation on larger, post-spawning (low lipid) mussels.

Uptake, depuration, and biotransformation of anthracene and benzo[a]pyrene in bluegill sunfish

Bluegills (Lepomis macrochirus Raf.) were exposed to [14C]anthracene or [14C]benzo[a]pyrene (B[a]P) in water. Rates of uptake and biotransformation within the fish were followed by 14C counting and thin-layer and liquid chromatography. The initial uptake-rate coefficient for anthracene (KU = 36 hr-1) was found to be independent of exposure concentration. The presence of dissolved humics did not affect anthracene uptake but did reduce the B[a]P uptake rate significantly. Biotransformation of the anthracene was constant at 0.22 nmol/g/hr, with approximately 92% of the residue unmetabolized at 4 hr. Uptake of B[a]P was linear (KU = 49 hr-1), although biotransformation increased from 0.044 to 0.088 nmol/g/hr between 1 and 2 hr of exposure. Only 11% of the B[a]P 14C activity at 4 hr represented the parent compound. Although 6% of the anthracene was found in liver and gall bladder, 25% of the B[a]P was distributed in the two organs. Depuration rates were first order and yielded half-lives of 17 hr for anthracene and 67 hr for B[a]P. The estimated bioconcentration factors (BCF) for anthracene and B[a]P in whole fish (KU/KD) were 900 and 4900, respectively, for total 14C activity, but only 675 and 490 for parent material. These BCFs were considerably lower than those predicted from the octanol-water partition coefficients because of biotransformation.

Three-phase partitioning of hydrophobic organic compounds in Great Lakes waters

Abstract Great Lakes waters were freshly collected, innoculated with radiolabelled hydrophobic organic compounds and, after equilibration, separated into particle bound, dissolved organic matter bound and freely dissolved phases. In these ambient suspended matter (0.2–5 ppm) and dissolved organic carbon (1–6 ppm) media, the freely dissolved phase generally dominates and the amounts associated with dissolved organic matter rarely exceeds 5% for most compounds. Solubility controls the constituent distribution between particle bound and freely dissolved but plays a much smaller role in mediating the binding to dissolved organic matter. Differences observed in the binding to dissolved and particulate organic matter support the need to consider the distribution of constituents among three phases. Although the concentration and composition of the substrate changes significantly, there is no apparent seasonal effect on the distribution of compounds among the three phases in the Great Lakes.

Bioaccumulation and critical body residue of PAHs in the amphipod, Diporeia spp.: additional evidence to support toxicity additivity for PAH mixtures

Polycyclic aromatic hydrocarbons (PAHs) are considered to act additively when exposed as congener mixtures. Additive internal concentrations at the site of toxic action is the basis for recent efforts to establish a sum PAH guideline for sediment-associated PAH toxicity. This study determined the toxicity of several PAH congeners on a body residue basis in Diporeia spp. These values were compared to the previously established LR(50) value for a PAH mixture based on the molar sum of PAH congeners and demonstrated similar LR(50) values for individual PAH. These results support the contention that the PAH act at the same molar concentration whether present as individual compounds or in mixture. Aqueous exposures were conducted for 28 d, and the water was exchanged daily to maintain the exposure concentration. The concentration in the exposures declined by an average of 22% between water exchanges across all compounds, and ranged from 11% to 32%. The toxicokinetics were determined using both time-weighted-average (TWA) and time-variable water concentrations and were not statistically different between the two source functions. Toxicity was determined for both mortality and immobility (failure to swim on prodding) and on both a TWA water concentration and a body residue basis. The LC(50) values ranged from 1757 microg l(-1) for naphthalene after 10 d exposure to 79.1 microg l(-1) for pyrene after 28 d exposure, and the EC(50) ranged from 1587 microg l(-1) for naphthalene after 10 d exposure to 38.2 microg l(-1) for pyrene after 28 d exposure. The LR(50) values for all congeners at all lengths of exposure were essentially constant and averaged 7.5+/-2.6 micromol g(-1), while the ER(50) for immobility averaged 2.6+/-0.6 micromol g(-1). The bioconcentration factor declined with increasing exposure concentration and was driven primarily by a lower uptake rate with increasing dose, while the elimination remained essentially constant for each compound.

Influence of polyethyleneimine graftings of multi-walled carbon nanotubes on their accumulation and elimination by and toxicity to Daphnia magna.

Modifications of carbon nanotubes (CNTs) for different applications may change their physicochemical properties such as surface charge. Assessments of the extent to which such modifications influence CNT ecotoxicity, accumulation, and elimination behaviors are needed to understand potential environmental risks these variously modified nanoparticles may pose. We have modified carbon-14 labeled multi-walled carbon nanotubes (MWNTs) with polyethyleneimine (PEI) surface coatings to increase their aqueous stability and to give them positive, negative, or neutral surface charges. Uptake and elimination behaviors of Daphnia magna exposed to PEI-coated and acid-modified MWNTs at concentrations of approximately 25 and 250 μg/L were quantified. PEI surface coatings did not appear to substantially impact nanotube accumulation or elimination rates. Although the PEI-modified nanotubes exhibited enhanced stability in aqueous solutions, they appeared to aggregate in the guts of D. magna in a manner similar to acid-treated nanotubes. The MWNTs were almost entirely eliminated by Daphnia fed algae during a 48 h elimination experiment, whereas elimination without feeding was typically minimal. Finally, PEI coatings increased MWNT toxicities, though this trend corresponded to the size of the PEI coatings, not their surface charges.

Distribution of organic carbon and organic xenobiotics among different particle-size fractions in sediments

The distributions of benzo[a]pyrene, hexachlorobiphenyl, and total organic carbon in a Lake Michigan sediment and a Florissant soil sample were determined and related to the known bioavailability of the compounds. The distribution of organic compounds among small particles (<63 μm diameter) was different from the distribution of the total organic carbon. However, the organic matter remained the major sorbent for these compounds. Changing the fractionation conditions, by performing the fractionation in distilled water instead of natural lake water, altered the distributions for both organic carbon and xenobiotics among the particles. Further, the contaminant distribution relative to organic carbon content differed between particle-size fractions and between contaminants of different compound classes, e.g., PAHs and PCBs. The differential distribution of the contaminants in the particle-size fractions likely contributed to the observed differences in bioavailability of organic contaminants for benthic organisms and may be exacerbated by selective feeding.

The sorption of PAH onto dissolved organic matter in Lake Michigan waters

Abstract The polynuclear aromatic hydrocarbons are hydrophobic organic contaminants (HOC) that associate with dissolved organic matter (DOM) in natural water systems. The DOM-HOC complex is sufficiently stable to allow measurement of an association constant, K B . For individual HOC in different natural waters, K B ranges over two orders of magnitude. Our results show that the K B is more dependent on the source of the DOM than the water solubility of the HOC but that for a specific water sample, correlation of K B with solubility does exist.