Assessing the cause of impacts on benthic organisms near Rouyn-Noranda, Quebec

Sediments from lakes near Rouyn-Noranda, Quebec, contain elevated concentrations of several metals, including Cd, Cu, Pb and Zn. Amphipods, fingernail clams, mayflies and tanytarsid midges were absent, and sediment toxicity was observed in chronic tests with Hyalella in sediments from Lac Dufault, the lake closest to Rouyn-Noranda. Bioaccumulation by Hyalella demonstrated elevated bioavailability of Cd, Co, Cr, Pb and Tl, but only Cd was accumulated to levels close to the toxic threshold. Copper, which is regulated by Hyalella, was not elevated in these amphipods, but it was elevated in overlying water in the toxicity tests. Toxic effects in Lac Dufault sediments are probably caused primarily by Cd, at least in amphipods, with a possible minor contribution from Cu. An integrated assessment, including sediment chemistry, benthic community composition, sediment toxicity, metal bioaccumulation in benthos, and comparison of bioaccumulation and/or overlying water concentrations with threshold effect concentrations, provides the best indication of effects and their cause.     

Relative contribution of food and water to 27 metals and metalloids accumulated by caged Hyalella azteca in two rivers affected by metal mining

Hyalella were caged at three sites in each of the two rivers for 17 days. Food added to the cages consisted of plant and detrital material collected from the same, or other, sites. Concentrations of some metals in Hyalella (e.g., Cd and Cu), but not others (e.g., Se), appeared to reach steady-state within 5 days in one of the rivers. Metal accumulation was minimal by day 5 in the other river, possibly due to the very low temperatures in this river for the first part of the exposure period. Both analysis of variance and analysis of covariance, using site as a categorical variable and metal in food as either a categorical or continuous variable, indicated that Cd, Cu and Se were the only metals for which concentration in food had a significant effect on concentration in Hyalella. Nevertheless, water was still a major source for these metals as well. Other metals which varied by over fivefold in food but for which concentration in food had no effect on concentration in Hyalella included Ag, As, Bi, Sb, U and Zn. Concentrations of the remaining metals varied less than fourfold in food, making it difficult to determine if these were accumulated from food.     

Toxicity and bioaccumulation of thallium in Hyalella azteca, with comparison to other metals and prediction of environmental impact

Thallium (Tl) is an extremely toxic but little studied metal. For Hyalella azteca exposed in Lake Ontario water, a 25% reduction in survival (the LC25) occurred at about 48 nmol litre(-1) after 4 weeks. Body concentrations of Tl, which were proportional to water concentrations, averaged 290 nmol g(-1) dry mass at the LC25. Growth was reduced at slightly lower concentrations. Concentrations affecting reproduction were variable at < 50% of the LC25. On a water-concentration basis Tl was more toxic than Ni, Cu or Zn, but less toxic than Cd or Hg to Hyalella; toxicity to Pb was similar. On a body-concentration basis, the toxicities of Tl, Cd, Hg and Pb were all similar. Unlike Cd, Tl toxicity and uptake was affected by K concentrations in the water, and not by Ca, Mg, Na or other ions. Toxicity was proportional to uptake, and body concentrations were better predictors of toxicity than water concentrations in media with varying K concentrations. Preliminary measurements of Tl and Cd uptake by Hyalella from Hamilton Harbour and Lake Ontario sediments suggested that total bioavailable metal concentrations were greater in deep-water sediments from Lake Ontario than in sediments from the harbour. The ratio of bioavailable metal to the toxic threshold was slightly higher for Cd than for Tl, but well below 1 for both metals.     

Metal bioavailability and toxicity through a sediment core.

Sediment cores from Richard Lake near Sudbury, Ontario, were sectioned and analyzed for total metal content, plus metal bioavailability and toxicity to Hyalella azteca (after equilibration with oxygenated overlying water). Strong and similar sediment profiles were observed for Cd, Co, Cu and Ni in the sediment. However, these differed from metal bioavailability profiles (bioaccumulation by Hyalella and metals in overlying water). Bioavailability profiles for Cu also differed from those for Cd, Co or Ni. The deepest sediment layers, deposited prior to industrial development, were non-toxic. Sediment toxicity was attributed to Ni dissolution into overlying water. Moreover, differential bioavailability of Ni in surface and deeper sediment layers was observed. This can affect the interpretation of toxicity data for sediments collected by different methods (e.g. core vs. grab samples). Based on Pb-210 dating and trends in Ni in the core, chronic toxicity of surface sediments from Richard Lake might approach non-toxic levels in about 15 years.     

Chronic toxicity of ammonia to the amphipod Hyalella azteca; Importance of ammonium ion and water hardness

Ammonia toxicity resulted in the continuous mortality of Hyalella azteca for up to 10 weeks with similar mortality rates for adults and young. Growth was not reduced at concentrations below those causing chronic mortality (1 mM total ammonia in Lake Ontario water), but reproduction was reduced at concentrations as low as 0.32 mM. Chronic mortality was a function of total ammonia (or ammonium ion), and not un-ionized ammonia, when the pH was adjusted by addition of acid. However, a 1 in 10 dilution of Lake Ontario water in distilled water resulted in a 10-fold reduction in the 4 week LC50. In contrast to common practice, ammonia toxicity to Hyalella is best defined on a total ammonia basis, but variations in hardness and other ions must be taken into account.     

Lac Dufault sediment core trace metal distribution, bioavailability and toxicity to Hyalella azteca

To determine changes in metal distribution, bioavailability and toxicity with sediment depth, two 20-cm-long replicate cores were collected from a lake historically subjected to the influence of metal mining and smelting activity. The vertical distribution of Pb, Cd and Cu in sediment was similar for all three metals, with the surface layers showing enrichment and the deeper (pre-industrial) layers showing lower concentrations. Toxicity of each sediment core section was determined in laboratory tests with the freshwater amphipod Hyalella azteca. Bioavailable metal in each sediment slice was estimated from metal concentrations in overlying water in these toxicity tests and, for Cd, also from metal bioaccumulation. The profile for Cd in tissue was comparable to Cd in sediment and overlying water, but relative Cd bioavailability from sediment increased with sediment depth. Survival increased with increasing sediment depth, suggesting that surface sediments were probably less or non-toxic before industrialization.     

Chronic toxicity of arsenic, cobalt, chromium and manganese to Hyalella azteca in relation to exposure and bioaccumulation

Chronic toxicity of As, Co, Cr and Mn to Hyalella azteca can be described using a saturation-based mortality model relative to total-body or water metal concentration. LBC25s (total-body metal concentrations resulting in 25% mortality in 4 weeks) were 125, 103, 152 and 57,900 nmol g-1 dry weight for As, Co, Cr and Mn respectively. LC50s (metal concentrations in water resulting in 25% mortality in 4 weeks) were 5600, 183, 731, and 197,000 nmol L-1, respectively. A hormesis growth response to As exposure was observed. Growth was a more variable endpoint than mortality for all four toxicants; however, confidence limits based on growth and mortality all overlapped, except Cr which had no effect on growth. Mn toxicity was greater in glass test containers compared to plastic. Bioaccumulation of As, Co, Cr, and Mn was strongly correlated with, and is useful for predicting, chronic mortality.     

Metal partitioning and uptake in central Ontario forests

Evaluation of the potential environmental risk posed by metals depends to a great extent on modeling the fate and mobility of metals with soil-solution partitioning coefficients (Kd). However, the effect of biological cycling on metal partitioning is rarely considered in standard risk assessments. We determined soil-solution partitioning coefficients for 5 metals (Cd, Zn, Pb, Co and Ni) at 46 forested sites that border the Precambrian Shield in central Ontario, where soil pHaq varied from 3.9 to 8.1. Foliage from the dominant tree species and forest floor samples were also collected from each site to compare their metal levels with Kd predictions. Analogous to other studies, log Kd values for all metals were predicted by empirical linear regression with soil pH (r2=0.66-0.72), demonstrating that metal partitioning between soil and soil solution can be reliably predicted for relatively unpolluted forest mineral soils by soil pH. In contrast, whereas the so-called bioavailable water-soluble metal fraction could be predicted from soil pH, metal concentrations in foliage and the forest floor at each site were not consistently related to pH. Risk assessment of metals should take into account the role of biota in metal cycling and partitioning in forests, particularly if metal bio-accumulation and chronic toxicity in the food chain, rather than metal mobility in soils, are of primary concern.     

Metal bioavailability and toxicity to fish in low-alkalinity lakes: A critical review

Fish in low-alkalinity lakes having pH of 6.0-6.5 or less often have higher body or tissue burdens of mercury, cadmium, and lead than do fish in nearby lakes with higher pH. The greater bioaccumulation of these metals in such waters seems to result partly from the greater aqueous abundances of biologically available forms (CH(3) Hg(+), Cd(2+), and Pb(2+)) at low pH. In addition, the low concentrations of aqueous calcium in low-alkalinity lakes increase the permeability of biological membranes to these metals, which in fish may cause greater uptake from both water and food. Fish exposed to aqueous inorganic aluminum in the laboratory and field accumulate the metal in and on the epithelial cells of the gills; however, there is little accumulation of aluminum in the blood or internal organs. In low-pH water, both sublethal and lethal toxicity of aluminum has been clearly demonstrated in both laboratory and field studies at environmental concentrations. In contrast, recently measured aqueous concentrations of total mercury, methylmercury, cadmium, and lead in low-alkalinity lakes are much lower than the aqueous concentrations known to cause acute or chronic toxicity in fish, although the vast majority of toxicological research has involved waters with much higher ionic strength than that in low-alkalinity lakes. Additional work with fish is needed to better assess (1) the toxicity of aqueous metals in low-alkalinity waters, and (2) the toxicological significance of dietary methylmercury and cadmium.     

Heavy metal in sediments of Ziya River in northern China: distribution,potential risks,and source apportionment

The concentration partitioning between the sediment particle and the interstitial water phase plays an important role in controlling the toxicity of heavy metals in aquatic systems. The aim of this study was to assess the sediment quality in a polluted area of the Ziya River, Northern China. The contamination potential and bioavailability of six metals were determined from the concentrations of total metals and the bioavailable fractions. The results showed that the concentrations of Cr, Cu, Ni, Zn, and Pb exceeded the probable effect concentration at several sites. The high geoaccumulation indices showed that the sediments were seriously contaminated by Cd. The ratio of acid-volatile sulfide (AVS) to simultaneously extracted metal (SEM) was higher than 1, which indicated that the availability of metals in sediments was low. The risk assessment of interstitial waters confirmed that there was little chance of release of metals associated with acid-volatile sulfide into the water column. Values of the interstitial water criteria toxicity unit indicated that none of the concentrations of the studied metals exceeded the corresponding water quality thresholds of the US Environmental Protection Agency. Positive matrix factorization showed that the major sources of metals were related to anthropogenic activities. Further, if assessments are based on total heavy metal concentrations, the toxicity of heavy metals in sediment may be overestimated.     

Quantification of bioavailable nickel in sediments and toxic thresholds to Hyalella azteca

Bioaccumulation and chronic toxicity of nickel (Ni) to Hyalella azteca in Ni-spiked sediments was strongly affected by the source of sediment used. The total range in LC50s on a sediment concentration basis ranged over 20 fold. Differences in Ni toxicity generally matched differences in Ni bioaccumulation, and toxicity expressed on a body concentration basis varied less than three fold. Body concentrations, therefore, provide a much more reliable prediction of Ni toxicity in sediments than do concentrations in the sediment. Ni in overlying water was also a reliable predictor of Ni toxicity, but only in tests conducted in Imhoff settling cones with large (67:1) water to sediment ratios. Overlying water LC50s for tests in beakers varied 18 fold. Sediment and body concentrations of Ni tolerated by Hyalella were slightly higher in cones than in beakers. Reproduction was not affected significantly by Ni at concentrations below the LC50 and 10-week EC50s for survival and biomass production (including survival, growth and reproduction) were only marginally lower than 4-week EC50s (survival and growth only).     

Metal stoichiometry in predicting Cd and Cu toxicity to a freshwater green alga Chlamydomonas reinhardtii

In this study, we quantified the accumulation and toxicity of cadmium and copper in a freshwater green alga, Chlamydomonas reinhardtii, under different phosphate conditions. The accumulated Cd and Cu concentrations increased significantly with increasing ambient P concentrations and free metal ion concentrations. The metal:P ratio remained independent of the ambient P concentration. For the three pulse-amplitude-modulated parameters, the median inhibition concentrations were 1.5-1.6x and 2.0x higher, but the medium inhibition cellular quota was 2.2x and 1.2x lower for cells maintained at 0.1 microM P than for cells maintained at 10 microM P for Cd and Cu, respectively. Furthermore, the difference in metal toxicity decreased (for Cd) or disappeared (for Cu) when the toxicity was expressed by the metal:P ratio in the cells, indicating that the stoichiometry of metals and P can be better used to predict the toxicity of metals. It is necessary to consider the stoichiometry of metals in predicting metal toxicity in phytoplankton.     

Kenneth Mellanby Review Award. Trace metal concentrations in aquatic invertebrates: why and so what?

All aquatic invertebrates take up and accumulate trace metals whether essential or not, and subsequent body concentrations of trace metals show enormous variability across metals and invertebrate taxa. Accumulated metal concentrations are interpreted in terms of different trace metal accumulation patterns, dividing accumulated metals into two components--metabolically available metal and stored detoxified metal. Crustaceans are used as examples of different accumulation patterns that will have a general applicability to all aquatic invertebrates. Toxicity is related to a threshold concentration of metabolically available metal and not to total accumulated metal concentration. The significance of accumulated metal concentrations is discussed in terms of the biological significance, including the attempted recognition of a high or low concentration, and of the applied use of aquatic invertebrates in biomonitoring programmes assessing geographical and temporal variation in trace metal bioavailabilities in aquatic systems.     

Chemical extractions and predicted free ion activities fail to estimate metal transfer from soil to field land snails

This study investigates the relevance of several soil chemical extractions (calcium chloride, acetic acid, citric acid and a four-step sequential procedure) and predicted free metal ion activities in the soil solution to characterise the transfer of trace metals (Cd, Pb, and Zn) from soil to snail soft tissues over a large smelter-impacted area (Metaleurop Nord, Nord-Pas-de-Calais, France). The study was first performed on six snail species together and then specifically on Cepaea sp. and Oxychilus draparnaudi. When the six species were considered together, the accumulation of metals depended mostly on the species. When significant, total or extractable metal concentrations, or the predicted free ion activities, accounted for less than 7% of the variation of the metal concentrations in the snail tissues. Species-specific analyses showed that extractable concentrations explained approximately 25% of the variation of the metal concentrations in O. draparnaudi, and up to 8% in Cepaea snails. When using total soil concentrations and soil properties as explanatory variables, the models were generally slightly better, explaining up to 42% of the variance. The soil extraction procedures and predicted free ion activities used in this study did not accurately estimate the metal transfer from soil to snails and could not be used in risk assessment.     

Partitioning and bioaccumulation of cadmium in artificial sediment systems: application of a stable isotope tracer technique

The utility of stable isotope tracers for investigating the relationship between cadmium (Cd) partitioning in artificial sediment-water systems and Cd accumulation in a benthic detritivore (Asellus racovitzai, Isopoda) was explored. In the laboratory, Cd isotopes were applied to synthetic sediment and isotope concentrations were measured in sediment, overlying water and exposed asellids over a 10-day period. Isotope ratios measured in sediment and water were compared to ratios measured in asellids to determine whether Cd partitioning could predict metal bioaccumulation. Two different parameters which might affect Cd partitioning between the sediment and overlying water compartments were investigated: the chemical form in which Cd was added to systems, and the organic matter content of the sediment. To test the effect of chemical form on Cd partitioning, three isotopes of cadmium were individually applied to formulated sediment in varying combinations of 113Cd(NO3)2, 112Cd-humic acid (HA) 114CdSO4. The results demonstrated that chemical form did not influence partitioning, as the Cd isotope that was applied to sediment in the nitrate form exhibited similar partitioning between sediment and overlying water as the isotope that was applied in the sulfate or HA form. However, Cd isotope concentrations in overlying water were strongly related to the pattern of isotope accumulation in asellids suggesting that overlying water concentrations determined Cd bioaccumulation. In contrast, when the organic matter content of sediment was increased through the addition of Sphagnum peat moss, total Cd concentrations in overlying water and tissue were low, and there was no relationship between Cd-isotope concentrations in tissue and water. These results indicate that Cd accumulation occurred primarily from water, and factors that increase metal partitioning to sediment, such as increased sediment organic matter content, decrease Cd accumulation in asellids. The stable isotope tracer method described herein appears to be a useful technique for investigating the relationship between metal partitioning and bioaccumulation in simple sediment systems, but could also be extended to more complex systems, and used with different metals that have multiple stable isotopes.     

The acanthocephalan Paratenuisentis ambiguus as a sensitive indicator of the precious metals Pt and Rh from automobile catalytic converters

Recent studies revealed that intestinal acanthocephalans of fish can accumulate heavy metals to concentrations orders of magnitude higher than those in the host tissues or the aquatic environment. This significant heavy metal accumulation by acanthocephalans, even surpassing that of established free living accumulation bioindicators, encouraged us to study the bioavailability of the platinum-group-metals (PGM) Pt and Rh for parasites. These precious metals are used in catalytic converters of cars for exhaust gas purification in Europe since the early 1980s. In addition to the beneficial effect in reducing the emission of CHx, CO and NOx of cars there is an increasing emission of these metals. However, it still remains unclear if these elements become accumulated in the biosphere and whether they affect the health of organisms. The present study reveals that in European eels (Anguilla anguilla) naturally infected with the eoacanthocephalan parasite Paratenuisentis ambiguus and experimentally exposed to ground catalytic converter material, the parasites take up and accumulate the catalytic active metals Pt and Rh whereas in the examined host tissues we found no metal uptake. Compared with the PGM concentrations in the water the worms contained 1600 times higher Rh and 50 times higher Pt concentrations. Thus, the parasites can be used as sentinel organisms reflecting even very low levels of precious metals.     

The relation between Acid Volatile Sulfides (AVS) and metal accumulation in aquatic invertebrates: Implications of feeding behavior and ecology

The present study evaluates the relationship between Acid Volatile Sulfides (AVS) and metal accumulation in invertebrates with different feeding behavior and ecological preferences. Natural sediments, pore water and surface water, together with benthic and epibenthic invertebrates were sampled at 28 Flemish lowland rivers. Different metals as well as metal binding sediment characteristics including AVS were measured and multiple regression was used to study their relationship with accumulated metals in the invertebrates taxa.Bioaccumulation in the benthic taxa was primarily influenced by total metal concentrations in the sediment. Regarding the epibenthic taxa metal accumulation was mostly explained by the more bioavailable metal fractions in both the sediment and the water. AVS concentrations were generally better correlated with metal accumulation in the epibenthic invertebrates, rather than with the benthic taxa. Our results indicated that the relation between AVS and metal accumulation in aquatic invertebrates is highly dependent on feeding behavior and ecology.     

The chronic toxicity of aluminium, cadmium, mercury, and lead in birds: a review

The toxicity of chronic dietary metal exposure in birds is reviewed. It is concluded that significant physiological and biochemical responses to such exposure conditions occur at dietary metal concentrations insufficient to cause signs of overt toxicity. Particularly important are reproductive effects which include decreased egg production, decreased hatchability, and increased hatchling mortality. Young, growing birds are typically more sensitive to the toxic effects of chronic metal exposure than adults, and altricial species are often more sensitive than precocial species. Factors which modify the absorption and toxicity of heavy metals, such as Se for the case of Hg, and Ca for the case of Pb and Cd, are discussed. Monitoring strategies for assessing environmental metal exposure in birds are evaluated.     

Metal accumulation by stream bryophytes, related to chemical speciation

Metal accumulation by aquatic bryophytes was investigated using data for headwater streams of differing chemistry. The Windermere Humic Aqueous Model (WHAM) was applied to calculate chemical speciation, including competitive proton and metal interactions with external binding sites on the plants. The speciation modelling approach gives smaller deviations between observed and predicted bryophyte contents of Cu, Zn, Cd and Pb than regressions based on total filtered metal concentrations. If all four metals, and Ni, are considered together, the WHAM predictions are superior at the 1% level. Optimised constants for bryophyte binding by the trace metals are similar to those for humic substances and simple carboxylate ligands. Bryophyte contents of Na, Mg and Ca are approximately explained by binding at external sites, while most of the K is intracellular. Oxide phases account for some of the Al, and most of the Mn, Fe and Co.     

Resuspension of contaminated field and formulated reference sediments Part I: Evaluation of metal release under controlled laboratory conditions

In aquatic systems where metal contaminated sediments are present, the potential exists for metals to be released to the water column when sediment resuspension occurs. The release and partitioning behavior of sediment-bound heavy metals is not well understood during resuspension events. In this study, the release of Cd, Cu, Hg, Ni, Pb and Zn from sediments during resuspension was evaluated using reference sediments with known physical and chemical properties. Sediment treatments with varying quantities of acid volatile sulfide (AVS), total organic carbon (TOC), and different grain size distributions were resuspended under controlled conditions to evaluate their respective effects on dissolved metal concentrations. AVS had the greatest effect on limiting release of dissolved metals, followed by grain size and TOC. Predictions of dissolved concentrations of Cd, Ni, Pb and Zn were developed based on the formulated sediment Σ_metal/AVS ratios with Σ_metal being the total sediment metal concentration. Predicted values were compared to measured dissolved metal concentrations in contaminated field sediments resuspended under identical operating conditions. Metal concentrations released from the field sediments were low overall, in most cases lower than predicted values, reflecting the importance of other binding phases. Overall, results indicate that for sulfidic sediments, low levels of the study metals are released to the dissolved phase during short-term resuspension.