Aqueous Cd Concentrations Research Articles

Cadmium bioaccumulation and distribution in the freshwater bivalve Anodonta woodiana exposed to environmentally relevant Cd levels

Anodonta woodiana is a globally distributed freshwater bivalve, which is a unique bioindicator in the “Freshwater Mussel Watch” project. Numerous countries have used A. woodiana for biomonitoring the aqueous cadmium (Cd) contamination. However, the bioaccumulation and distribution characteristics of environmentally relevant Cd concentrations in the bivalve were unknown. In this study, A. woodiana was exposed to aqueous Cd concentrations (1.1, 2.6, and 5.5 μg/L) for 30 days. The concentrations of Cd in the whole soft tissues were linearly and positively correlated with the aqueous Cd concentrations and exposure time (P < 0.05). Analysis of the organic bioaccumulation and distribution showed that Cd concentrations and proportions in the gills and mantle were linearly and positively correlated with aqueous Cd concentrations and with the Cd concentrations in the whole soft tissues (P < 0.05). Analyses of the subcellular fractions showed that Cd concentrations and proportions in the metal-rich granule (MRG) were linearly and positively correlated with aqueous Cd concentrations and with the Cd concentrations in the whole soft tissues (P < 0.05). This suggests that the gills and mantle could be the main target organs for Cd bioaccumulation, and that the MRG could be the major site for Cd bioaccumulation and distribution. These results improve our understanding of the bioaccumulation and distribution mechanisms of Cd in bivalves.

Interplay between dietary lipids and cadmium exposure in rainbow trout liver: Influence on fatty acid metabolism, metal accumulation and stress response

The present study aimed at investigating interactive effects between dietary lipids and both short- and long-term exposures to a low, environmentally realistic, cadmium (Cd) concentration. Juvenile rainbow trout were fed four isolipidic diets (31.7 g/kg) enriched in either linoleic acid (LA, 18:2n-6), alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3) or docosahexaenoic acid (DHA, 22:6n-3). From the 4th week of this 10-week experiment, the lipid level of the diet was increased (120.0 g/kg) and half of the fish fed each diet were aqueously exposed to Cd (0.3 μg/L) while the other half were not exposed to Cd (control). Fish were sampled and their liver was harvested for fatty acid profile, hepatic Cd and calcium concentrations, total glutathione level and gene expression assessment, either (i) after 4 weeks of feeding and 24 h of Cd contamination (day 29) (short-term Cd exposure) or (ii) after 10 weeks of feeding and 6 weeks of Cd contamination (day 70) (long-term Cd exposure). We found that both dietary lipids and Cd exposure influenced fatty acid homeostasis and metabolism. The hepatic fatty acid profile mostly reflected that of the diet (e.g. n-3/n-6 ratio) with some differences, including selective retention of specific long chain polyunsaturated fatty acids (LC-PUFAs) like DHA and active biotransformation of dietary LA and ALA into LC-PUFAs. Cd effects on hepatic fatty acid profiles were influenced by the duration of the exposure and the nutritional status of the fish. The effects of diet and Cd exposure on the fatty acid profiles were only sparsely explained by variation of the expression pattern of genes involved in fatty acid metabolism. The biological responses to Cd were also influenced by dietary lipids. Fish fed the ALA-enriched diet seemed to be the least affected by the Cd exposure, as they showed a higher detoxifying ability against Cd with an early upregulation of protective metallothionein a (MTa) and apoptosis regulator BCL2-Like1 (BCLx) genes, an increased long-term phospholipid synthesis and turnover and fatty acid bioconversion efficiency, as well as a lower long-term accumulation of Cd in their liver. In contrast, fish fed the EPA-enriched diet seemed to be the most sensitive to a long-term Cd exposure, with an impaired growth performance and a decreased antioxidant capacity (lower glutathione level). Our results highlight that low, environmentally realistic aqueous concentrations of Cd can affect biological response in fish and that these effects are influenced by the dietary fatty acid composition.

Modelling the potential mobility of Cd, Cu, Ni, Pb and Zn in Mollic Fluvisols.

European floodplain soils are frequently contaminated with potentially toxic inorganic substances. We used a multi-surface model to estimate the aqueous concentrations of Cd, Cu, Ni, Pb and Zn in three Mollic Fluvisols from the Central Elbe River (Germany). The model considered complexation in solution and interactions with soil organic matter (SOM), a clay mineral and hydrous Al, Fe and Mn oxides. The amounts of reactive metals were derived from extraction with 0.43M HNO3. Modelling was carried out as a function of pH (soil pH±1.4) because it varies in floodplain soils owing to redox processes that consume or release protons. The fraction of reactive metals, which were dissolved according to the modelling, was predominantly <1%. Depending on soil properties, especially pH and contents of SOM and minerals of the clay fraction, the modelled concentrations partially exceeded the trigger values for the soil-groundwater pathway of the German soil legislation. This differentiation by soil properties was given for Ni, Pb and Zn. On the other hand, Cd was more mobile, i.e., the trigger values were mostly exceeded. Copper represented the opposite, as the modelling did not predict exceeding the trigger values in any horizon. Except for Pb and partially Zn (where oxides were more important), SOM was the most important adsorbent for metals. However, given the special composition and dynamics of SOM in mollic horizons, we suggest further quantitative and qualitative investigations on SOM and on its interaction with metals to improve the prediction of contaminant dynamics.

Release of elements to natural water from sediments of Lake Roosevelt, Washington, USA

Reservoir sediments from Lake Roosevelt (WA, USA) that were contaminated with smelter waste discharged into the Columbia River (BC, Canada) were examined using three measures of elemental release reflecting varying degrees of physical mixing and time scales. Aqueous concentrations of Cd, Cu, Pb, and Zn in the interstitial water of reservoir sediments, in the gently stirred overlying waters of incubated sediment cores, and in supernatants of aggressively tumbled slurries of reservoir sediments generally were higher than the concentrations from a reference site. When compared to chronic water-quality criteria, all three measures of release suggest that slag-contaminated sediments near the U.S.-Canadian border are potentially toxic as a result of Cu release and Pb release in two of the three measures. All three measures of Cd release suggest potential toxicity for one site farther down the reservoir, probably contaminated as a result of transport and adsorption of Cd from smelter liquid waste. Releases of Zn and As did not appear to be potentially toxic. Carbonate geochemistry indirectly affects the potential toxicity by increasing water hardness.

Simultaneous Application of Dissolution/Precipitation and Surface Complexation/Surface Precipitation Modeling to Contaminant Leaching

This paper discusses the modeling of anion and cation leaching from complex matrixes such as weathered steel slag. The novelty of the method is its simultaneous application of the theoretical models for solubility, competitive sorption, and surface precipitation phenomena to a complex system. Selective chemical extractions, pH dependent leaching experiments, and geochemical modeling were used to investigate the thermodynamic equilibrium of 12 ions (As, Ca, Cr, Ba, SO4, Mg, Cd, Cu, Mo, Pb, V, and Zn) with aqueous complexes, soluble solids, and sorptive surfaces in the presence of 12 background analytes (Al, Cl, Co, Fe, K, Mn, Na, Ni, Hg, NO3, CO3, and Ba). Modeling results show that surface complexation and surface precipitation reactions limit the aqueous concentrations of Cd, Zn, and Pb in an environment where Ca, Mg, Si, and CO3 dissolve from soluble solids and compete for sorption sites. The leaching of SO4, Cr, As, Si, Ca, and Mg appears to be controlled by corresponding soluble solids.

Accumulation of heavy metals in food web components across a gradient of lakes

Recent studies have emphasized the need for understanding the accumulation and fate of metal contaminants at different trophic levels and across a broad spectrum of lake types. To address both issues, metal concentrations (Hg, Zn, Cd, As, and Pb) were measured in the water, two size fractions of zooplankton, and fish from 20 lakes in contaminated to pristine watersheds in the northeastern United States. Our goals were to examine links between watershed characteristics and aqueous metal levels in lakes and relationships between aqueous concentrations, metal burdens in different plankton groups and in fish. Two pairs of metals, (1) Hg and Zn and (2) As and Pb, exhibited strong similarities both in the factors that predict their concentrations in water and in the patterns of accumulation in particular trophic levels. Aqueous concentrations of Hg and Zn were highest in cool water lakes, whereas As and Pb were highest in more eutrophic lakes in agricultural areas. Aqueous Cd concentrations were closely correlated with the land‐use variables, percentage of agricultural land, and road densities. Similarly, Hg and Zn both biomagnified from small plankton (45–202 µm) to macrozooplankton (&gt;202 mm) and from macrozooplankton to fish. In contrast, bioaccumulation of both As and Pb diminished with increasing trophic level. Although aqueous metal and zooplankton metal levels were not significant predictors of As and Pb levels in fish, metal levels in zooplankton were predictive of Hg and Zn in fish, suggesting that sources of bioaccumulation differ for different metals. Our findings demonstrate the importance of investigating upper and lower trophic levels separately, to fully understand metal transfer pathways in aquatic food webs.

Cadmium Solubility in Aerobic Soils

Cadmium solubility in calcareous soils is assumed to be controlled by precipitation of Cd carbonate minerals. The Cd carbonate (octavite) solubility product (K so ) was determined in a pure CdCO3 solution, suspensions of soils amended with Cd, and two limed, wetted, and dried agricultural soils amended with Cd to determine if dissolved Cd was controlled by CdCO3 precipitation in the soils. Calculation of solution ion activities was done accounting for the ionic strength and formation of Cd complexes in solution. The K so for octavite was 1.64 x 10 -13 (standard error of the mean was 0.08 x 10 -13 ) at 25°C and zero ionic strength. Suspensions of soil amended with 2 to 1000 mg Cd kg -1 in a 10 -3 M CaCl 2 solution showed more than 10 times supersaturation of the solution relative to the determined CdCO3 solubility product. Soils amended with 2 to 500 mg Cd kg -1 that were periodically watered and allowed to dry out showed more than five times supersaturation. Long-term aging (15 mo) had little effect on supersaturation in both experiments. It is likely that precipitation inhibitors such as dissolved organic C were the reasons for the apparent lack of CdCO3 precipitation. The experiments showed that under environmentally relevant conditions carbonates are not likely to govern aqueous Cd concentrations in calcareous agricultural soils.

Fish bioturbation of cadmium-contaminated sediments: Factors affecting Cd availability toDaphnia magna

Benthic fish bioturbation of contaminated sediments is thought to enhance exposure and, potentially, bioaccumulation into planktonic organisms. Exposures were conducted with cadmium-spiked sediment, 1.0 mg/kg nominal concentrations, and koi carp (Cyprinus carpio). Daphnia magna were placed in aquaria with and without fish for 6 d and Cd bioaccumulation was measured every 48 h. Koi carp bioturbation increased mean total suspended solids (TSS) in two trials from 0.001 mg/L to 44.4 mg/L and 19.2 mg/L to 762.4 mg/L. Mean aqueous Cd concentrations increased from 1.4 μg/L to 2.8 μg/L, and from 1.6 μg/L to 13.2 μg/L. Cadmium binding capacity increased from 28.9 μg/L to 169.8 μg/L in with-fish treatments when compared to controls. However, Daphnia magna body burdens did not increase. Mean Cd residues of daphnids exposed with fish, 9.2 μg/g, were not statistically different from without-fish exposures, 8.0 μg/g. Body burdens slightly decreased in the first trial after the with-fish treatment, 9.4 μg/g to 8.3 μg/g. Fish size was partially correlated with TSS and aqueous Cd concentrations and TSS positively correlated with binding capacity. Because increased TSS in the with-fish treatment resulted in increased binding capacity, it is probable that cadmium bioavailability decreased. Although koi carp were capable of remobilizing Cd from sediment, Cd bioaccumulation into Daphnia magna was not significant.

Use of transplanted mosses and autochthonous liverworts to monitor trace metals in acidic and non-acidic headwater streams (Vosges mountains, France): Sci. Total. Environ., 1995, 175/3 (235–244). Summ. in Engl.

Abstract Thirteen headwater streams situated in the Vosges Mountains (northeastern France) have been studied for trace metal contamination (Al, Mn, Pb, Cd) in relation to acidification. Assessment of metal concentrations has been performed using water analyses and metal content in transplanted aquatic bryophytes. The streams studied ranged from acidic to circumneutral. Aluminium, Mn and Pb concentrations in water increased significantly with decreasing pH, whereas no relationship was observed between aqueous Cd concentrations and pH. The relation between metal contents in the moss and in the water varied markedly between metals. Aluminium and Pb levels in mosses reflect well the increasing concentrations of metals in water related to the pH whereas Mn in mosses does not. The metal content of the autochthonous liverworts was different from those of the transplanted mosses which implies different conclusion about the contamination level of the water. Adaptation to different pH conditions leading to physiological and structural specificities could explain the different ability of these two species to accumulate metals in acid surroundings.

Use of transplanted mosses and autochthonous liverworts to monitor trace metals in acidic and non-acidic headwater streams (Vosges mountains, France)

Thirteen headwater streams situated in the Vosges Mountains (northeastern France) have been studied for trace metal contamination (Al, Mn, Pb, Cd) in relation to acidification. Assessment of metal concentrations has been performed using water analyses and metal content in transplanted aquatic bryophytes. The streams studied ranged from acidic to circumneutral. Aluminium, Mn and Pb concentrations in water increased significantly with decreasing pH, whereas no relationship was observed between aqueous Cd concentrations and pH. The relation between metal contents in the moss and in the water varied markedly between metals. Aluminium and Pb levels in mosses reflect well the increasing concentrations of metals in water related to the pH whereas Mn in mosses does not. The metal content of the autochthonous liverworts was different from those of the transplanted mosses which implies different conclusion about the contamination level of the water. Adaptation to different pH conditions leading to physiological and structural specificities could explain the different ability of these two species to accumulate metals in acid surroundings.

Control of cadmium levels inHolopedium gibberum(crustacea, cladocera) in canadian shield lakes

Cadmium concentrations (Cd-h) of Holopedium gibberum (Crustacea, Cladocera) collected from 26 Canadian Shield lakes with positive alkalinity ranged from 0.9 to 31 μg/g. Levels were positively correlated with aqueous Cd concentrations (Cd-aq) and negatively correlated with clutch size. Animals collected from acidified lakes did not have elevated Cd-h concentrations despite elevated Cd-aq levels. In three intensive study lakes, the presence of eggs lowered Cd-h concentrations and Cd-h levels frequently increased with increases in body size. In two of these lakes, many H. gibberum occupied waters rich in particulate iron just above the anoxic interface. Cd-h levels fell when animals were experimentally confined to this layer, presumably because much of the Cd-aq was adsorbed by the particulate iron and was unavailable for uptake. We suggest that the behavior of animals, specifically their movement to light-scattering layers just above the anoxic interface, influences the accumulation of Cd by H. gibberum in Canadian Shield lakes.