Dependency of polychlorinated biphenyl and polycyclic aromatic hydrocarbon bioaccumulation in Mya arenaria on both water column and sediment bed chemical activities

The bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) by the filter-feeding soft-shell clam Mya arenaria was evaluated at three sites near Boston (MA, USA) by assessing the chemical activities of those hydrophobic organic compounds (HOCs) in the sediment bed, water column, and organisms. Polyethylene samplers were deployed to measure the activities of HOCs in the water column. Sediment activities were assessed by normalizing concentrations with sediment-water sorption coefficient values, including adsorption to black carbon in addition to absorption by organic carbon. Likewise, both lipids and proteins were considered in biota-water partition coefficients used to estimate chemical activities in the animals. Chemical activities of PAHs in M. arenaria were substantially less than those of the corresponding bed sediments in which they lived. In contrast, chemical activities of PCBs in M. arenaria often were greater than or equal to activities in the corresponding bed sediments. Activities of PAHs, such those of pyrene, in the water column were undersaturated relative to the sediment. However, some PCBs, such as congener 52, had higher activities in the water column than in the sediment. Tissue activities of pyrene generally were in between the sediment and water column activities, whereas activity of PCB congener 52 was nearest to water column activities. These results suggest that attempts to estimate bioaccumulation by benthic organisms should include interactions with both the bed sediment and the water column.     

Impact of polychlorinated biphenyl and polycyclic aromatic hydrocarbon sequestration in sediment on bioaccumulation in aquatic food webs

It is not clear whether sequestration or aging of organic chemicals like polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) limits accumulation in higher levels of aquatic food chains. Therefore, the effect of aging on accumulation was studied in 1(-m3) model ecosystems that mimicked fish-dominated, macrophyte-dominated, and fish- and macrophyte-dominated shallow lakes. Also treatments without fish and macrophytes were included. General characteristics, biomasses, total (Soxhlet-extractable), and labile (6-h Tenax-extractable) PCB and PAH concentrations in sediment and biota were monitored over time. Accumulation data for PCB 28, PCB 149, and fluoranthene (native to the sediment taken from the field) were compared to those for spiked analogues PCB 29, PCB 155, and fluoranthene-d10. Labile fractions for spiked compounds were higher than for their native analogues and decreased over time, suggesting sequestration in the sediment. In the majority of cases, 6-h Tenax-extractable concentrations correlated better with concentrations in biota than Soxhlet-extractable concentrations. Ecosystem structure affected food web accumulation, but replicate variability was too high to detect clear treatment effects. Differences in accumulation between spiked compounds and their native analogues indicated an effect of aging for invertebrates, macrophytes, and benthivorous fish. Thus, aging may translate directly into reduced uptake at higher trophic levels.     

Determination of polychlorinated biphenyl and polycyclic aromatic hydrocarbon elimination rates in adult green and leopard frogs

The purpose of the present study was to quantify elimination kinetics of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in adult green frogs (Rana clamitans) and leopard frogs (Rana pipiens). Three experiments were conducted: PCB elimination rate constants were determined for both frog species, and PAH elimination rate constants were determined for leopard frogs only. In green frogs, significant PCB elimination rate constants ranged from 0.013 to 0.04 d(-1) (time for frogs to achieve 90% steady state with water [t90] = 57.8-178.2 d). In leopard frogs, significant PCB elimination rate constants ranged from 0.004 to 0.047 d(-1) (t90 = 48.8-657.9 d). Polycyclic aromatic hydrocarbon elimination in leopard frogs was faster than PCB elimination in either frog species: Significant PAH rate constants ranged from 0.069 to 0.188 d(-1) (t90 = 12.2-33.5 d). In both species, and for both PCBs and PAHs, a significant inverse relationship was found between the chemical elimination rate constant and Kow. These results show that adult anurans have relatively low elimination rates of PCBs but exhibit a small capacity for metabolic biotransformation of PAHs that is comparable to that of invertebrates but lower than that of fish. These findings suggest that adult amphibians have the potential to be used as biomonitors for persistent organic chemicals.     

Formation and fate of bound residues of [14C]benzene and [14C]chlorobenzenes in soil and plants

Outdoor experiments with [14C]hexachlorobenzene, [14C]pentachlorobenzene, [14C]1,2,4-trichlorobenzene, and [14C]benzene in soil-crop systems indicate that the formation rate of bound residues in soil and plants, expressed as bound residues in percentage of total residue in the sample, decreases with increasing number of chlorine in the molecule and, thus, with increasing chemical stability. The time course of formation and fate of bound residues in soil and plants is characterized by a very slow decrease of residue levels in soil, indicating that biodegradation of bound residues hardly exceeds their reformation from the parent compound during one vegetation period, and by a decrease of residue levels in plants. The portion of bound residues as compared to the total residue increases with time, indicating that bound residues are more persistent than the parent compounds and their soluble metabolites; benzene is an exception. Cress plants, in general, contain less bound residues than do barley plants. Again, benzene is an exception. In deeper soil layers, soil-bound residues occur also. The ratio between bound and extractable residues does not differ to a larger extent between the soil layers.     

Peroxisome proliferation and antioxidant enzymes in transplanted mussels of four basque estuaries with different levels of polycyclic aromatic hydrocarbon and polychlorinated biphenyl pollution

We aimed to determine the effects of changes in polycyclic aromatic hydrocarbon (PAH) and polychlorinated biphenyl (PCB) bioavailability on peroxisome proliferation and antioxidant enzymes to assess their potential use as pollution biomarkers. For this, mussels (Mytilus galloprovincialis) were sampled in Txatxarramendi and transplanted to Arriluze, Muskiz, and Plentzia (northern Spain), and vice versa. Arriluze was the most heavily polluted site, followed by Plentzia, Txatxarramendi, and Muskiz. Animals transplanted from a polluted station to a cleaner station lost contaminant load in three to six weeks, and when transplanted to a more polluted station, they accumulated PAHs and PCBs accordingly. Peroxisomal acyl-A oxidase (AOX) activity was the highest in animals from Arriluze, and animals transplanted to Arriluze showed increased AOX activity, reaching the levels of native mussels. Mussels from Txatxarramendi showed the lowest peroxisomal volume density (Vvp). Among mussels from Txatxarramendi, only those transplanted to Plentzia showed increased Vvp, whereas animals from Arriluze and Muskiz transplanted to Txatxarramendi after 2 d and six weeks, respectively, had decreased Vvp. Two days after transplant, superoxide dismutase and glutathione peroxidase activities were significantly lower in mussels from Arriluze and Muskiz, respectively, than in those from Txatxarramendi and than in animals transplanted to Txatxarramendi from these stations. In conclusion, transplant experiments with mussels are useful to assess the effects of pollution. Peroxisome proliferation, measured as induction of AOX or increased Vvp, shows great potential as a biomarker of pollution to be included in pollution monitoring programs. In the present work, we have demonstrated that peroxisome proliferation is a reversible phenomenon in mussels.     

Distribution of [14C]canthaxanthin and [14C]lycopene in rats and monkeys

The absorption and distribution of [14C]-canthaxanthin and [14C]lycopene were studied in rats and in rhesus monkeys following the oral administration of [14C]canthaxanthin or [14C]lycopene in olive oil supplemented with 1 mg alpha-tocopherol/mL. For canthaxanthin and lycopene, peak accumulation of radioactivity in plasma occurred between 4 and 8 h in rats and between 8 and 48 h in monkeys. In rats, the liver contained the largest amount of both kinds of radioactive pigments. In monkeys, with the exception of one stomach sample, liver was also the major depot organ for both canthaxanthin and lycopene. The other organs tested accumulated various amounts of pigment. No labeled metabolic products of either canthaxanthin or lycopene were found.     

Spatial covariation of microbial community composition and polycyclic aromatic hydrocarbon concentration in a creosote-polluted soil

Little is known about the spatial connection between soil microbial community composition and polycyclic aromatic hydrocarbon (PAH) concentration. A spatially explicit survey at a creosote-contaminated site demonstrated that microbial biomass (total concentration of phospholipid fatty acids [PLFAs]) and microbial community composition (PLFA fingerprints) were spatially autocorrelated, mostly within a distance of 25 m, and covaried with PAH concentrations. The concentration of PLFAs indicative of gram-negative bacteria (16:1omega7c, 16:1omega7t, 18:1omega7, cy17:0, and cy19:0) increased in the PAH hot spots, whereas PLFAs representing fungi and gram-positive bacteria (including actinomycetes) were negatively correlated to PAH concentrations. Most PLFAs were spatially autocorrelated, with distances varying between 4 and 25 m. Those PLFAs that increased in PAH-contaminated soil had autocorrelation ranges between 4 and 16 m, whereas the fungal indicator PLFA 18:2omega6,9 had the largest autocorrelation range (25 m). Bacterial strains isolated using a spray-plate technique and with the same PLFA composition as that in contaminated soil samples were capable of degrading phenanthrene, fluoranthene, and pyrene, indicating that the main PAH degraders could be isolated.     

Effect of volatile hydrocarbon fractions on mobility and earthworm uptake of polycyclic aromatic hydrocarbons from soils and soil/lampblack mixtures

Studies were conducted to examine the mobility and bioavailability to earthworms (Eisenia fetida) of priority pollutant polycyclic aromatic hydrocarbons (PAH) in a suite of 11 soils and soil/lampblack mixtures obtained from former manufactured-gas plant sites. Contaminant mobility was assessed using XAD4 resins encapsulated in dialysis tubing, which were exposed to slurried soils for 15 d. These experiments showed that mobility of PAH in the different soils strongly correlated to the levels of volatile hydrocarbons (namely, gasoline- and diesel-range organics [GRO and DRO]) that existed in the soils as co-contaminants. Actual PAH bioavailability (as measured by earthworm PAH concentrations) also appeared to depend on GRO + DRO levels, although this was most evident at high levels of these contaminants. These findings are discussed in view of the effects of dieselrange organics on oil viscosity, assuming that the hydrocarbon contaminants in these soils exist in the form of distinct adsorbed oil phases. This study, therefore, extends correlations between carrier-oil viscosity and dissolved solute bioavailability, previously observed in a number of other in vitro and whole-organism tests (and in bacterial mutagenicity studies in soil), to multicellular organisms inhabiting contaminated-soil systems.     

Fate of [14C]monolinuron in potatoes and soil under outdoor conditions

[phenyl-14C]Monolinuron was applied (2.5 and 1.9 kg/ha) to the soil surface of an outdoor lysimeter in two successive years: then, potatoes were grown. Total recovery of 14C in soil, plants, and leached water was about 55% (of 14C applied) after the first growing period and about 43% after the second growing period. Radioactivity in soil contained 77.1% (based on total 14C recovered in soil) bound residues, 15% monolinuron, and the following conversion products: N-(4-hydroxyphenyl)-N'-methoxy-N'-methylurea, N-(4-chlorophenyl)-N'-methylurea. N-(4-chlorophenyl)methylcarbamate, N-(4-chlorophenyl)-N-methyl-methylcarbamate, and 4-chloroformanilide. The leachate contained 0.8% (based on total 14C recovered in leachate) N-(4-hydroxyphenyl)-N'-methoxy-N'-methylurea. Potato plants contained 0.106 mg/kg radioactive residues in peeled tubers after one growing period and 15.94 mg/kg in the tops; after two growing periods, peeled tubers contained 0.091 mg/kg and tops contained 18.87 mg/kg radioactive residues. These residues consisted of bound 14C (57.9% of total 14C recovered in plants), N-(4-hydroxyphenyl)-N'-methoxy-N'-methylurea, N-(4-chlorophenyl)-N'-methylurea, N-(4-chlorophenyl)methylcarbamate, N-(4-chlorophenyl)-N-methyl-methylcarbamate, and 4,4'-dichlorozobenzene.     

Physicochemical characterization of coke-plant soil for the assessment of polycyclic aromatic hydrocarbon availability and the feasibility of phytoremediation

Coke oven site soil was characterized to assess the particle association and availability of polycyclic aromatic hydrocarbons (PAHs). We identified various carbonaceous materials including coal, coke, pitch, and tar decanter sludge. Most of the PAHs were associated with the polymeric matrix of tar sludge or hard pitch as discrete particles, coatings on soil mineral particles, or complex aggregates. The PAH availability from these particles was very low due to hindered diffusive release from solid tar or pitch with apparent diffusivities of 6 x 10(-15) for phenanthrene, 3 x 10(-15) for pyrene, and 1 x 10(-15) cm2/s for benzo[a]pyrene. Significant concentrations of PAHs were observed in the interior of solid tar aggregates with up to 40,000 mg/kg total PAHs. The release of PAHs from the interior of such particles requires diffusion over a substantial distance, and semipermeable membrane device tests confirmed a very limited availability of PAHs. These findings explain the results from three years of phytoremediation of the site soil, for which no significant changes in the total PAH concentrations were observed in the test plot samples. The observed low bioavailability of PAHs probably inhibited PAH phytoremediation, as diffusion-limited mass transfer would limit the release of PAHs to the aqueous phase.     

Free amino acid patterns and the distribution of 14C from [U-14C]-L-Leucine, [U-14C]-L-Lysine, and [U-14C]-L-Alanine in the tissues of young adult rats.

In studies designed to evaluate the role of the liver and muscle in modifying the plasma amino acid response, three levels of dietary amino acids, 3.6%, 4.8% and 6.0% were fed to three groups of young adult male rats for 2 weeks. After fasting, either [U-14C]-L-leucine, [U-14C]-L-lysine or [U-14C]-L-alanine was administered intragastrically with a portion of diet. After a 4.5 hour fast, rats were killed. Distribution of radioactivity was evaluated in trichloroacetic acid (TCA) supernatants and lipid-extracted precipitates of plasma, liver and gastrocnemius muscle, and in expired CO2. Free amino acids were measured and specific activities of amino acids were determined. Rats fed 6.0% or 4.8% amino acids lost less weight than those fed 3.6%. A high percentage of radioactivity from 14C-leucine and 14C-lysine was recovered in the lipid-extracted precipitate. TCA supernatants from rats fed 14C-leucine contained low levels of radioactivity. A large percentage (60%) of the radioactivity from 14C-alanine was expired in 14CO2. The percentages of alanine found in TCA precipitates were very low. Significant increases in concentration associated with increments in dietary amino acids occurred in plasma free isoleucine, leucine, valine and tyrosine; liver free histidine; and muscle free leucine and threonine. Concentrations of many amino acids were depressed in the muscle of rats fed 4.8% amino acids whereas they increased in response to 6.0%. Protein and free amino acid specific activities indicated no change in rates of protein synthesis. Data from this type of experiment may assist in interpreting the role of the liver and muscle in modifying the plasma amino acid response to dietary amino acids.     

Percutaneous absorption of [7.10-14C]benzo[a]pyrene and [7,12-14C]dimethylbenz[a]anthracene in mice

The percutaneous penetration, tissue distribution, and excretion of 14C-labeled benzo[a]pyrene (BaP) and dimethylbenz[a]anthracene (DMBA) were studied in mice. Both BaP and DMBA rapidly penetrated the skin and were excreted more in the feces than in the urine. The proportion of BaP or DMBA absorbed was less with increasing applied dose due to apparent saturation of the uptake process. Uptake from the dorsal skin of the nose was similar to uptake from the dorsal nuchal skin.     

Effect of sediment particle size on polycyclic aromatic hydrocarbon biodegradation: importance of the sediment-water interface

Mechanisms for the effects of sediment on the biodegradation of organic compounds in the aquatic environment are not clear. In this research, effects of sediment characteristics on biodegradation kinetics of chrysene and benzo[a]pyrene were studied by inoculating polycyclic aromatic hydrocarbon (PAH)-degrading bacteria. Because water and PAHs can pass a polytetrafluoroethylene membrane yet bacteria and sediment cannot, a membrane experiment was performed to compare the biodegradation rates of PAHs in water and at the sediment-water interface, providing direct evidence that the PAH biodegradation rate is enhanced by the presence of sediment. Biodegradation of PAHs in water-sediment systems was fitted to zero-order kinetics; the order of biodegradation rate in water-sediment systems with different sediment was fine silt > clay > coarse silt. Biodegradation of PAHs in water-sediment systems occurred mainly at the sediment-water interface. According to membrane experiment results, when the biodegradation kinetics was fit to a zero-order equation, the maximum specific growth rates of bacteria (1/d) at the sediment-water interface were approximately three- to fourfold those in the water phase. Furthermore, the associated mechanisms regarding the effect of sediment characteristics were analyzed by investigating the process of bacterial growth and the distribution of bacteria and PAHs between water and sediment phases.