Showing papers on "Bioaccumulation published in 1997"

Food as the Dominant Pathway of Methylmercury Uptake by Fish

Abstract: A field experiment was conducted to determine the degree to which fish accumulated methylmercury (MeHg) via their food or via passive uptake from water through the gills. Finescale dace (Phoxinus neogaeus) were held in 2000 L enclosed pens floating in an undisturbed, oligotrophic lake in northwestern Ontario. Fish were exposed to water containing either low (0.10–0.40 ng L-1), intermediate (0.45–1.30 ng L-1), or high (0.80–2.1 ng L-1) concentrations of MeHg. Zooplankton with either low (0.16–0.18 µg g-1 d.w.) or high (0.28–0.76 µg g-1 d.w.) concentrations of MeHg were added daily to each pen. Fish fed zooplankton with high concentrations of MeHg had significantly higher concentrations of mercury in muscle after 32 days than fish fed zooplankton with low concentrations of MeHg (ANCOVA, P<0.0001). Fish feeding on zooplankton with low concentrations of MeHg had the same amount of Hg in their tissues as fish at the start of the experiment. Uptake from water was at most 15%. This is the first experiment to confirm that food is the dominant pathway of MeHg bioaccumulation in fish at natural levels of MeHg.

Fugacity-Based Model of PCB Bioaccumulation in Complex Aquatic Food Webs

Abstract: A fugacity-based model is developed to simulate the phenomena of bioconcentration and biomagnification of organic contaminants in complex food webs in aquatic systems comprising contaminated water and sediment. The food web consists of N classes of organisms, which may feed on all organisms including their own class, and in which each organism may experience chemical uptake from benthic or pelagic food organisms and water with clearance by respiration, egestion, and metabolism. The expressions reduce to a single equation involving an N × N matrix of food preference parameters that is readily solved to give concentrations and fluxes throughout the food web. The model is applied illustratively to bioaccumulation of PCB congeners in Lake Ontario yielding results generally within a factor of 3 of measured values. This approach quantifies the roles of exchange with water, food uptake, and food web structure as determinants of bioaccumulation in aquatic systems and has the potential to be extended to treat broa...

Mercury concentrations in prey fish indicate enhanced bioaccumulation in mesopelagic environments

Abstract: The detection of high concentrations of methylmercury in the sub-thermocline low oxy- gen seawater indicates a potential for enhanced bioaccumulation of mercury in such environments not yet explored. Here we present mercury concentrations in 8 fish species of lo w trophic level in relation to their vertical distribution. Fish specie s were selected to cover a wide range of vertical distributions, from epipelagic ( 300 m) environments in the sub-tropical mid-North Atlantic. Mean mercury concentrations in the study species ranged fro m 57 to 377 ppb dry wt and were significantly and positively correlated with median daytime depth. Concentration s increased by 4-fold from epipelagic to mesopelagic species with no further increases with depth among mesopelagic spe- cies down to about 1200 m. Such enhanced mercury bioaccumulation in the marine mesopelagic com- partment seems to be determined proximately by levels in food and ultimately by water chemistry that controls mercury speciation and uptake at the base of the food chain. We conclude that this is the best explanation for high and yet poorly understood mercury concentration s found in deep-sea predators.

Equilibrium partitioning of heavy metals in dutch field soils. II. Prediction of metal accumulation in earthworms

Abstract: To evaluate the adequacy of the equilibrium partitioning concept in predicting metal bioaccumulation, a soil invertebrate species was exposed in 20 Dutch field soils with moderate metal contamination. Earthworms (Eisenia andrei) were kept in the soils for 3 weeks under laboratory conditions. Bioconcentration factors (BCFs) for six metals (Zn, Cu, Pb, Cd, Cr, Ni) and for As were calculated as the ratio of body- and solid-phase metal concentrations. Multivariate statistical analyses suggested that the BCFs for As, Cd, Cu, and Zn are governed by the same soil characteristics that determine equilibrium partition coefficients between the soil solid phase and the pore water. This suggests that uptake of metals is either direct from the pore water or indirect through an uptake route closely related to pore water. Regression equations were derived for predicting BCF values as a function of easily determinable soil characteristics. By means of internal validation it was shown that the equations obtained can be used for predictive purposes within the range of soil properties encountered in the dataset. Due to a lack of data, external validation was possible only in a qualitative sense.

Relative importance of water and food as cadmium sources to an aquatic insect (Chaoborus punctipennis) : Implications for predicting Cd bioaccumulation in nature

Abstract: The relative importance of water and food as Cd sources to the predatory insect Chaoborus punctipennis was established using a three-link planktonic food chain composed of larvae of the insect, its crustacean prey (Ceriodaphnia dubia), and the prey's algal food (Selenastrum capricornutum). To ensure that our laboratory results were reliable and could be extrapolated to field conditions, we introduced Cd at the bottom of the food chain; we used Cd concentrations to which animals might be exposed in nature; we measured Cd loss from the food to the water compartment; and we controlled the availability and concentrations of Cd in water and food. There was no significant difference between the Cd concentrations in larvae exposed to the metal in their food alone versus those exposed to Cd in both food and water, indicating that Cd bioaccumulation from water was negligible. These results suggest that, although Cd concentrations in the predator can be correlated with those in lake water, direct uptake from water ...

The Environmental Geochemistry and Bioaccessibility of Mercury in Soils and Sediments: A Review

Abstract: There have been many studies of mercury geochemistry in the environment and its bioconcentration/bioaccumulation through the aquatic food chain However, there is a dearth of information regarding the bioaccessibility of mercury in human receptors exposed primarily by soil ingestion This paper reviews the current state of knowledge of mercury bioaccessibility and speciation in soils, and the utility of speciation methods to estimate mercury bioaccessibility We conclude that additional research is necessary to determine: (1) whether analytical measurements can adequately determine the bioaccessibility of mercury in sediments and soils; (2) the accuracy of in vitro analyses in assessing mercury bioaccessibility; (3) the ability of mercury to cross tissue membranes of the mouth, esophagus, stomach, and the small and large intestines; (4) the speciation and distribution of mercury in biological fluids; and (5) mercury bioavailability using an in vivo animal model relevant to human gastrointestinal tract conditions

Bioaccumulation and metallothionein response in the asiatic clam (Corbicula fluminea) after experimental exposure to cadmium and inorganic mercury

Abstract: The involvement of metallothioneins (MTs) in cadmium (Cd) and inorganic mercury (Hg[II])bioaccumulation by the freshwater bivalve Corbicula fluminea was experimentally investigated after 0, 15, 30, and 45 d of exposure from the water column source. Three levels of contamination were studied for each metal: 0, 5, and 35 μg Cd/L and 0, 1.45, and 5 μg Hg/L, with two replicates per condition. Forty eight experimental units (EUs) were conducted simultaneously. The mollusks were fed twice a week by additions of phytoplanktonic algae. Quantification of MTs was done by Hg-saturation assay, using cold Hg(II). A partial purification of these proteins was conducted by gel-filtration chromatography, followed by Cd determinations in the different eluted fractions. Results at the whole organism (soft tissues) and organ or tissue group (gills, mantle, foot, visceral mass) levels show high metal concentrations, with a fourfold greater accumulation of inorganic Hg than Cd after 30 d exposure at the same concentration of 5 μg/L. Gills and visceral mass were the principal storage compartments. A significant increase in MT concentrations was revealed in these two organs after exposure to Cd: ratios between the MT concentrations in contaminated and control mollusks were 2.4 and 2.8, respectively, for 5 and 35 μg Cd/L. Cd burdens in the cytosol and in ≤18-kDa protein fractions, similar to purified mammal MTs, correspond to 30 and 14% of the total Cd accumulated in the whole organisms. No significant increase in MT biosynthesis was observed after exposure to inorganic Hg, despite the high metal concentrations in the organs.

Potential for phytoextraction of137 Cs from a contaminated soil

Abstract: Potential for phytoremediation of a soil contaminated with radiocesium was investigated in three phases: (1) hydroponic screening for plant species capable of accumulating elevated levels of cesium in shoots, (2) investigation of several amendments for their potential to increase the bioavailability of 137Cs in the contaminated soil, and (3) bioaccumulation of radiocesium in shoots of plants grown in137 Cs-contaminated soil

Modeling the influence of body size on trace element accumulation in the mussel Mytilus edulis

Abstract: We measured assimilation efficiencies (AEs) from ingested algal food, uptake rates from the dissolved phase, and efflux rate constants of 4 trace elements (Cd, Co. Se and Zn) in 3 size classes (1.5, 2.5, and 5.0 cm) of the mussel Mytilus edulis. AEs of Se and Zn remained constant among the 3 body sizes. AEs of Cd decreased with increasing body size, whereas AEs of CO increased with body size The rate constant of metal uptake from the dissolved phase decreased with increasing body size, but the calculated metal absorption efficiencies remained relatively constant or increased slightly in larger mussels. Efflux rate constants were comparable among the 3 body sizes, except for Cd whlch was lost about 2 times faster in the smaller mussels than in the largest mussels. A bioenergetic-based lunetic model was used to calculate the allometric coefficient (b) of metal accumulation with mussel body size; predicted b values were comparable to field measurements However, b increased exponent~ally with the growth rate constant, indicating that no single b value 1s likely to be observed in nature for a specific metal. The growth rate constant is needed for the model to predict metal concentration and allometry of metal accumulation in mussels, especially for smaller mussels. The relative importance of trace element uptake from the dissolved phase versus particulate ingestion in the overall metal uptake in mussels was relatively independent of mussel body size, primarily because the influx rates from the dissolved phase and from food were conlparably related to body size.

Comparison of contaminant accumulation in three species of marine invertebrates with different feeding habits

Abstract: In order to assess the importance of the mode of feeding for the bioaccumulation of contaminants from sediments, three marine benthic invertebrates, with different feeding habits, were exposed to contaminated sediments in outdoor mesocosms. Residue analyses were carried out for several polychlorinated biphenyls and polycyclic aromatic hydrocarbons after exposure periods of 60 to 140 days. It was shown that sediment ingestion is a major uptake route for the sediment-feeding lugworm, Arenicola marina, and for the facultative deposit-feeding baltic tellin, Macoma balthica. Residues in the filter-feeding mussel, Mytilus edulis, appeared to be independent of contaminant concentrations in the sediment. The difference between deposit and filter-feeding bivalves was confirmed in experiments involving the baltic tellin, with differences in the food availability in the overlying water. A simple linear regression model was used to describe contaminant concentrations in sediment-feeding invertebrates as a function of concentrations in sediment. A correction for the accumulation from water was made by subtracting the concentrations in filter feeders. It was concluded that chemical equilibrium partitioning alone is not sufficient for the assessment of the risks of contaminated sediments to sediment-feeding invertebrates, but that feeding habits should also be considered.

Bioaccumulation of polychlorinated dibenzo-p-dioxins in sediment by oligochaetes: Influence of exposure pathway and contact time

Abstract: Oligochaetes (Lumbriculus variegatus) were exposed simultaneously to radiolabeled [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and [14C]octachlorodibenzo-p-dioxin (OCDD) in sediment for 28 d, in order to study accumulation processes of hydrophobic substances. Elimination was studied for a further 20 d. The uptake and elimination rate constants and the bioaccumulation factors (BAFs) were determined for TCDD and OCDD in the presence and absence of sediment (overlying water). Steady-state concentrations in oligochaetes were achieved for TCDD but not for OCDD over the 28-d exposure. Biota-sediment accumulation factors (BSAFs) after a 28-d exposure were 1.6 ± 0.27 for TCDD and 0.07 ± 0.02 for OCDD. Steady-state log BAF values (lipid based) for TCDD and OCDD in oligochaetes in the overlying water were 5.9 and 5.5 L/kg, respectively. The effect of incubation time between sediment and contaminants was investigated by repeating the accumulation study after a contact period of 21 months. BSAFs of sediment-sorbed TCDD and OCDD were 1.5 to 2-fold lower for the long contact time sediment. Based on comparison of predicted accumulation from pore water and observed accumulation by sediment-exposed oligochaetes, it was concluded that 1.4-fold greater accumulation occurred due to assimilation of TCDD and OCDD from ingested sediment. This additional accumulation in the presence of sediment, not accounted for by uptake only from pore waters, was consistent with literature data for other hydrophobic organochlorines.

Toxicity and bioaccumulation of a mixture of heavy metals in Chironomus tentans (Diptera: Chironomidae) in synthetic sediment

Abstract: This research investigated toxicity and bioaccumulation of a mixture of Cd, Cu, Pb, and Zn in Chironomus tentans in synthetic sediment, and compared predicted to measured steady-state bioaccumulation factors (BAFs). In a toxicity test, C. tentans were exposed to various dilutions of a base concentration (1.0 X) of a mixture of the four metals (5 {micro}g/g Cd. 10 {micro}g/g Cu. 70 {micro}g/g Pb, and 300 {micro}g/g Zn) in synthetic sediment. Mortality ranged from 17 to 100%. To measure bioaccumulation of the metals, C. tentans were exposed to 0.35 X the base concentration for a period of up to 14 d in two uptake tests. Bioaccumulation of all four metals increased over the 14-d uptake phases. Concentrations of metals in chironomids were significantly correlated with exposure time in the uptake phases. Only concentrations of copper approached background levels after 7 d depuration. Uptake rate coefficients and elimination rate constants were determined for each metal. Bioaccumulation factors were highest for Cd and lowest for Pb. With the exception of Pb, steady-state BAFs were within a factor of about two of those calculated using the first-order kinetic model. The high BAFs calculated may indicate greater bioavailability in synthetic sediment. Studies comparing toxicity andmore » bioaccumulation of natural and synthetic sediments are necessary before the use of synthetic sediments is widely adopted.« less

Chromium, copper, iron and manganese bioaccumulation in some organs and tissues of Oreochromis mossambicus from the lower Olifants River, inside the Kruger National Park

Abstract: The bioaccumulation of chromium, copper, iron and manganese by Oreochromis mossambicus was investigated at two localities (Mamba and Balule) in the lower Olifants River, inside the boundaries of the Kruger National Park. The Cr, Cu, Fe and Mn concentrations, recorded in the tissues of O. mossambicus at Mamba and Balule, did not differ much from each other. However, it was generally found that the highest accumulation of metals by the fish occurred at Mamba, except for iron, where the opposite occurred. The metals investigated during this study mainly accumulated in the liver and gills, followed by the skin, and lastly the muscle.

The bioaccumulation of polynuclear aromatic hydrocarbons by benthic invertebrates in an intertidal marsh

Abstract: Biota-sediment accumulation factors (BSAF; concentration in organism lipid/concentration in sediment on an organic carbon basis) of polyaromatic hydrocarbons varied with season and along an intertidal gradient in a coastal marsh in San Francisco Bay. The BSAFs were lowest during the local rainy season. During the dry season, BSAFs were lowest in the high intertidal zone closest to shore. Significant differences among species groups were also observed; BSAFs were lowest in polychaetes and highest in the asian clam (Potamocorbula amurensis), varying over almost three orders of magnitude (0.0069-5.4 g sediment organic C/g lipid). The BSAFs decreased with increasing percent fines in the sediments and with PAH concentrations on an organic carbon basis. We suggest that a determining variable is the content of highly aromatic soot particles, which increases during periods of surface runoff and which is expected in the dry season to be highest in the high intertidal zone where these finer particles preferentially accumulate. Correlations of BSAFs with the ratio of the logarithm of the activity coefficients in porewaters to those in sediments were generally stronger than with log Kow, indicating a limitation of octanol as a surrogate for sediment organic carbon or organism lipid. These observations qualify but also strengthen the concept of equilibrium partitioning as the determining factor in bioaccumulation by benthic organisms of nonpolar organic compounds from sediments; the assumption that “organic carbon” can be considered in generic terms without allowance for aromaticity and probably other factors as well, must, however, be reconsidered.

Effects of Heavy Metals on Prey Abundance, Feeding Habits, and Metal Uptake of Brown Trout in the Arkansas River, Colorado

Abstract: We examined the effects of heavy metals on prey abundance, feeding habits, and metal bioaccumulation of brown trout (Salmo trutta) at two sites in the Arkansas River, a Colorado stream polluted by mining discharges. We hypothesized that altered prey communities and exposure to metals would affect brown trout feeding habits, bioaccumulation, and condition. Prey communities at the upstream reference station (AR1) were dominated by metal-sensitive mayflies (Ephemeroptera) and black flies (Diptera: Simuliidae), whereas those at the downstream polluted station (AR5) were dominated by metal-tolerant chironomids (Diptera: Chironomidae) and caddisfiies (Trichoptera). Differences in prey community composition were reflected in the feeding habits of brown trout, which consumed greater numbers of chironomids and caddisflies at station AR5. Concentrations of heavy metals (Cd, Cu, and Zn) in water, dominant prey taxa, and brown trout stomach contents were greater at station AR5. Metal levels were also signifi...

Toxicity and bioaccumulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin in long-term tests with the freshwater benthic invertebrates Chironomus tentans and Lumbriculus variegatus

Abstract: Two species of freshwater benthic invertebrates, Chironomus tentans and Lumbriculus variegatus, were exposed to three dietary concentrations of 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD), and toxicity and bioaccumulation were determined. No toxic effects were observed in full life cycle tests with either species at tissue residue concentrations up to 9,533 ng TCDD/g lipid. The observed lack of sensitivity of the two species to TCDD was consistent with a presumed absence of the aryl hydrocarbon receptor in aquatic invertebrates. Predictions of lipid-normalized tissue concentrations were made based on lipid-normalized TCDD concentrations in the food and were within 15% of targeted concentrations in both species. Depuration studies indicated that TCDD elimination followed first-order kinetics, with elimination rate constants of 0.0014 to 0.0022 h−1 for L. variegatus and 0.0070 to 0.0099 h−1 for C. tentans. Half-lives ranged from 315 to 495 h in L. variegatus and from 70 to 99 h in C. tentans. The ability of invertebrates to accumulate relatively high concentrations of TCDD in the absence of toxic effects may be relevant to the transfer of contaminants through aquatic food webs to potentially sensitive vertebrate species.