Copper, zinc, manganese, iron, lead, cadmium, mercury and arsenic in fish from Lake Tanganyika, Burundi

Melatonin as an Ameliorative Agent Against Cadmium- and Lead-Induced Toxicity in Fish: an Overview

Diverse anthropogenic activities and lack of knowledge on its consequences have promoted serious heavy metal contaminations in different aquatic systems throughout the globe. The non-biodegradable nature of most of these toxic heavy metals has increased the concern on their possible bioaccumulation in aquatic organisms as well as in other vertebrates. Among these aquatic species, fish are most sensitive to such contaminated water that not only decreases their chance of survivability in the nature but also increases the probability of biomagnifications of these heavy metals in higher order food chain. After entering the fish body, heavy metals induce detrimental changes in different vital organs by impairing multiple physiological and biochemical pathways that are essential for the species. Such alterations may include tissue damage, induction of oxidative stress, immune-suppression, endocrine disorders, uncontrolled cell proliferation, DNA damage, and even apoptosis. Although uncountable reports have explored the toxic effects of different heavy metals in diverse fish species, but surprisingly, only a few attempts have been made to ameliorate such toxic effects. Since, oxidative stress seems to be the underlying common factor in such heavy metal-induced toxicity, therefore, a potent and endogenous antioxidant with no side effect may be an appropriate therapeutic solution. Apart from summarizing the toxic effects of two important toxicants, i.e., cadmium and lead in fish, the novelty of the present treatise lies in its arguments in favor of using melatonin, an endogenous free radical scavenger and indirect antioxidant, in ameliorating the toxic effects of heavy metals in any fish species.

Mass-Balance Modeling of Metal Loading Rates in the Great Lakes

Major elements and nutrients are key water quality monitoring targets in the Great Lakes, but large-scale and long-term data for (trace) metals remains comparatively scarce. Consequently, the sources and processes controlling metal loading rates and potential accumulation in the lakes are not as well constrained. Here, we present a comprehensive assessment of select metal loads in the Great Lakes basin, aggregating tributary and connecting channel loads as well as estimates for atmospheric input and sedimentation. In total, 26,845 hydrometric and water quality datapoints from major environmental surveillance programs were compiled into mass-balance calculations and dynamic simulations for 1980-2020. Conservative element (Na, Cl) loads were used to calibrate the black-box approach, and mass-balance for these elements could be achieved at ≥90% and long-term trends accurately reproduced. In contrast, biogeochemically reactive (trace) metals Cu, Ni, Zn and Pb displayed highly variable source-sink behavior across the Great Lakes. Our results show that i) atmospheric inputs, tributary loads, and sedimentation all affect the concentrations and temporal trends of the studied metals but differently in the upper versus lower lakes, ii) smaller tributaries can be disproportionately important to lake-wide metal budgets, and iii) current loading rates may yield increasing lake-wide average Cl concentrations (e.g., up to 2.3 mg/L in Lake Superior) but decreasing metal concentrations (e.g., down to <0.25 μg/L Cu in Lake Ontario) by 2100. This work provides important quantitative baselines for metal loads in the Great Lakes and may help optimize surveillance and management strategies for the preservation of Great Lakes water quality.

Bioaccumulation of mercury and other trace elements in bottom-dwelling omnivorous fishes: The case of Diplodus sargus (L.) (Osteichthyes: Sparidae)

The presence of toxic elements in fish represents a hazard for human health, especially in Mediterranean countries and other regions with high per-capita fish consumption. The present research, carried out along the northern Catalan coast (NW Mediterranean), aimed to determine the levels of trace metals and arsenic in the muscle of white seabream Diplodus sargus (L.), a common demersal species of growing interest for fisheries and aquaculture. Average mercury concentrations widely exceeded the limits imposed by EU despite the low contamination levels previously reported for the study area, stressing the potential risk associated to the consumption of medium-sized, non-predatory fishes. The other analyzed elements fell within the recommended limits. Preliminary results about the feeding habits of D. sargus are reported, in order to determine feeding habitat and items of the analyzed specimens.

Total and cytosolic concentrations of twenty metals/metalloids in the liver of brown trout Salmo trutta (Linnaeus, 1758) from the karstic Croatian river Krka

Total and cytosolic concentrations of twenty metals/metalloids in the liver of brown trout Salmo trutta (Linnaeus, 1758) were studied in the period from April 2015 to May 2016 at two sampling sites on Croatian river Krka, to establish if river water contamination with metals/metalloids downstream of Knin town has influenced metal bioaccumulation in S. trutta liver. Differences were observed between two sites, with higher concentrations of several elements (Ag, As, Ca, Co, Na, Se, Sr, V) found downstream of Knin town, whereas few others (Cd, Cs, Mo, Tl) were, unexpectedly, increased at the Krka River spring. However, total metal/metalloid concentrations in the liver of S. trutta from both sites of the Krka River were still mainly below previously reported levels for pristine freshwaters worldwide. The analysis of seasonal changes of metal/metalloid concentrations in S. trutta liver and their association with fish sex and size mostly indicated their independence of fish physiology, making them good indicators of water contamination and exposure level. Metal/metalloid concentrations in the metabolically available hepatic cytosolic fractions reported in this study are the first data of that kind for S. trutta liver, and the majority of analyzed elements were present in the cytosol in the quantity higher than 50% of their total concentrations, thus indicating their possible availability for toxic effects. However, the special attention should be directed to As, Cd, Cs, and Tl, which under the conditions of increased exposure tended to accumulate more within the cytosol. Although metal/metalloid concentrations in S. trutta liver were still rather low, monitoring of the Krka River water quality and of the health status of its biota is essential due to a trend of higher metal/metalloid bioaccumulation downstream of Knin town, especially taking into consideration the proximity of National Park Krka and the need for its conservation.

Acclimation capacity of the three-spined stickleback (Gasterosteus aculeatus, L.) to a sudden biological stress following a polymetallic exposure

To get closer to the environmental reality, ecotoxicological studies should no longer consider the evaluation of a single pollutant, but rather combination of stress and their interaction. The aim of this study was to determine if responses of a fish to a sudden biological stress could be modified by a prior exposure to a chemical stress (a polymetallic contamination). For this purpose, in situ experiment was conducted in three ponds in the Haute-Vienne department (France). One pond was chosen for its high uranium concentration due to uranium mine tailings, and the two other ponds, which were not submitted to these tailings. Three-spined sticklebacks (Gasterosteus aculeatus) were caged in these ponds for 14 days. After this period, fish were submitted to a biological stress, exerted by lipopolysaccharides injection after anesthesia, and were sacrificed 4 days after these injections for multi-biomarkers analyses (leucocyte viability, phagocytic capacity and reactive oxygen species production, antioxidant peptide and enzymes, lipid peroxidation and DNA damage). The pond which received uranium mine tailings had higher metallic concentrations. Without biological stress, sticklebacks caged in this pond presented an oxidative stress, with increasing of reactive oxygen species levels, modification of some parts of the antioxidant system, and lipid peroxidation. Caging in the two most metal-contaminated ponds resulted in an increase of susceptibility of sticklebacks to the biological stress, preventing their phagocytic responses to lipopolysaccharides and modifying their glutathione contents and glutathione-S-transferase activity.

Mercury Accumulation, Structural Damages, and Antioxidant and Immune Status Changes in the Gilthead Seabream (Sparus aurata L.) Exposed to Methylmercury

In aquatic systems, mercury (Hg) is an environmental contaminant that causes acute and chronic damage to multiple organs. In fish, practically all of the organic Hg found is in the form of methylmercury (MeHg), which has been associated with animal and human health problems. This study evaluates the impact of waterborne-exposure to sublethal concentrations of MeHg (10 μg L(-1)) in gilthead seabream (Sparus aurata). Hg was seen to accumulate in liver and muscle, and histopathological damage to skin and liver was detected. Fish exposed to MeHg showed a decreased biological antioxidant potential and increased levels of the reactive oxygen molecules compared with the values found in control fish (nonexposed). Increased liver antioxidant enzyme activities (superoxide dismutase and catalase) were detected in 2 day-exposed fish with respect to the values of control fish. However, fish exposed to MeHg for 10 days showed liver antioxidant enzyme levels similar to those of the control fish but had increased hepato-somatic index and histopathological alterations in liver and skin. Serum complement levels were higher in fish exposed to MeHg for 30 days than in control fish. Moreover, head-kidney leukocyte activities increased, although only phagocytosis and peroxidase activities showed a significant increase after 10 and 30 days, respectively. The data show that 30 days of exposure to waterborne MeHg provokes more significant changes in fish than a short-term exposure of 2 or 10 days.

Bioaccumulation of mercury, cadmium, zinc, chromium, and lead in muscle, liver, and spleen tissues of a large commercially valuable catfish species from Brazil

The increasing amounts of heavy metals entering aquatic environments can result in high accumulation levels of these contaminants in fish and their consumers, which pose a serious risk to ecosystems and human health. We investigated the concentrations of mercury (Hg), cadmium (Cd), zinc (Zn), chromium (Cr), and lead (Pb) in muscle, liver, and spleen tissues of Pseudoplatystoma corruscans specimens collected from two sites on the Paraopeba River, Brazil. The level of heavy metals concentrations in the tissues was often higher in viscera (i.e. liver and spleen) than in muscle, and thus, the viscera should not be considered for human consumption. Correlations between metal concentrations and fish size were not significant. Although the levels of muscle bioaccumulation of Hg, Cd, Zn, Cr, and Pb, generally do not exceed the safe levels for human consumption, the constant presence of heavy metals in concentrations near those limits considered safe for human consumption, is a reason for concern, and populations who constantly consume fish from polluted rivers should be warned. Our findings also indicate that in a river network where certain areas are connected to other areas with high rates of environmental pollutants, people should be cautious about the regular consumption of fish, even when the fish consumed are caught in stretches of the basin where contamination levels are considered low, since many of the freshwater fish with high commercial value, such as the catfish surubim, are migratory.

Heavy metal contents in water, sediment and fish in a karst aquatic ecosystem of the Plitvice Lakes National Park (Croatia)

An evaluation of the quality status of the pristine karst, tufa depositing aquatic environment of the Plitvice Lakes National Park based on the analysis of heavy (ecotoxic) metals was examined for the first time. Analyses of trace metals in water, sediment and fish (Salmo trutta, Oncorhynchus mykiss, Squalius cephalus) samples were conducted either by stripping voltammetry (Zn, Cd, Pb and Cu) or cold vapour atomic absorption spectrometry (Hg). The concentration of dissolved trace metals in water was very low revealing a pristine aquatic environment (averages were, in ng/L: 258 (Zn), 10.9 (Cd), 11.7 (Pb), 115 (Cu) and 1.22 (Hg)). Slightly enhanced concentrations of Cd (up to 50 ng/L) and Zn (up to 900 ng/L) were found in two main water springs and are considered as of natural origin. Observed downstream decrease in concentration of Cd, Zn and Cu in both water and sediments is a consequence of the self-purification process governed by the formation and settling of authigenic calcite. Anthropogenic pressure was spotted only in the Kozjak Lake: Hg concentrations in sediments were found to be up to four times higher than the baseline value, while at two locations, Pb concentrations exceeded even a probable effect concentration. The increase of Hg and Pb was not reflected on their levels in the fish tissues; however, significant correlations were found between Cd level in fish tissues (liver and muscle) and in the water/sediment compartments, while only partial correlations were estimated for Zn and Cu. A high discrepancy between values of potentially bioavailable metal fraction estimated by different modelling programs/models raised the question about the usefulness of these data as a parameter in understanding/relating the metal uptake and their levels in aquatic organism. The aquatic environment of the Plitvice Lakes National Park is characterized, in general, as a clean ecosystem.

Assessment of heavy metals/metalloid (As, Pb, Cd, Ni, Zn, Cr, Cu, Mn) concentrations in edible fish species tissue in the Pearl River Delta (PRD), China

The major aim of this study was to investigate heavy metal content of edible fish in the PRD. Eleven species of fish (consisting of 711 individuals) [catfish (Clarias fuscus), tilapia (Oreochromis mossambicus), grass carp (Ctenopharyngodon idellus), bighead carp (Aristichthys nobilis), mandarin fish (Siniperca kneri), snakehead (Channa asiatiea), black bass (Micropterus salmoides), mangrove snapper (Lutjanus griseus), star snapper (Lutjanu stellatus), snubnose pompano (Trachinotus blochii) and orange-spotted grouper (Epinephelus coioides)] were collected for the analyses of heavy metals. Overall concentrations (mg/kg, ww) in the fish muscles were: As (0.03-1.53), Pb (0.03-8.62), Cd (0.02-0.06), Ni (0.44-9.75), Zn (15.7-29.5), Cr (0.22-0.65), Cu (0.79-2.26), Mn (0.82-6.91). Significant level of Pb were found in tilapia at all locations. It is recommended that heavy metal concentrations in different fish species must be determined on a regular basis in the future so as to reduce human health risks from acute and chronic food intoxication.

Assessment of trace elements in animal tissues from Turkey

In this study, trace element contents of animal tissues were determined by atomic absorption spectrometry after microwave digestion method. The accuracy of the method was confirmed by analysis of standard reference material (NIST SRM 1577b Bovine Liver). Trace element contents in animal tissue samples were found in the range of 98.3-18.2 μg/g (Fe), 2.89-0.26 μg/g (Mn), 23.9-4.54 μg/g (Zn), 0.08-0.01 μg/g (Pb), 32.9-1.66 μg/g (Cu), and 0.32-0.01 μg/g (Cd). The results were compared with literature values. The results obtained for toxic and trace elements in analyzed animal tissue samples were acceptable to human consumption at nutritional and toxic levels.

Low levels of cadmium exposure induce DNA damage and oxidative stress in the liver of Oujiang colored common carp Cyprinus carpio var. color

Cadmium (Cd) compounds are widely distributed toxic environmental and industrial pollutants, and they may bring danger to growth and development of aquatic organisms. In China, the Oujiang color common carp, Cyprinus carpio var. color, is a very important fish, from an economic point of view, and is well used for fish culture in paddy fields. The purpose of this study was to show the low concentrations of cadmium-induced oxidative stress response and DNA damage in the livers of Cyprinus carpio var. color. Superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH) in liver were measured after exposure to Cd levels (0.41, 0.52, 0.69, 1.03 and 2.06 mg/L, respectively) for 7 days and compared with the control groups. DNA damage, including indicators of damage percentage, DNA tail length (TL) and DNA tail moment (TM) were also analyzed by comet assays. Results showed that MDA and GSH levels in all treatment groups increased significantly relative to the controls (P < 0.01). Treatment with Cd at concentration of 0.41 mg/L increased SOD activity, while treatment with Cd at concentrations >0.41 mg/L inhibited SOD activities. DNA damage percentage, TL and TM also significantly increased when the Cd level was >0.41 mg/L. Positive correlations were also found between DNA damage levels and MDA levels (r = 0.74 for DNA damage percentage, r = 0.83 for TL, r = 0.84 for TM; P < 0.01 for all) as well as between GSH and MDA levels (r = 0.77, P < 0.01). These results strongly suggested that Cd-induced DNA damage in the livers of Cyprinus carpio var. color was due to lipid peroxidation and oxidative stress.

Metals (Hg, Pb, Cu, and Zn) bioaccumulation in sediment, fish, and human scalp hair: a case study from the city of mersin along the southern coast of Turkey

This study investigates mercury, lead, copper, and zinc concentrations in six most frequently consumed fish species (120 samples), sediments (20 samples) taken from Karaduvar Fishing Area where fish species live, and Mersin Port as a contrary region, and human scalp hair for people regularly consuming these fish species (50 samples) and non-fish-eaters (15 samples) in Mersin, Turkey. On taking living environment into account, the fish groups include pelagic species of Liza saliens, Liza aurata, and demersal species of Merluccius merluccius, Mullus barbatus, Upeneus moluccensis, and Solea solea. Total Hg (THg) was found to accumulate in muscle tissues at the lowest concentration (0.01 microg/g) in L. saliens and at the highest (2.66 microg/g) in S. solea. Pb was only detected at high concentrations of 1.86 microg/g in M. barbatus and of 2.16 microg/g in M. merluccius. Cu and Zn concentrations were below the detection limit within all fish species. In the sediment samples, Pb and Cu concentrations were persistently below their effect range-median (ERM) value, whereas this limiting value only maintained for 15% of THg concentrations. On the other hand, the effect range-low (ERL) of sediment exceeded at Pb in 15% of samples and Cu in 25% of samples. Zn remained below the detection limit for sediment samples. The metal concentrations at scalp hairs of regular consumers of these fish groups and non-fish eaters vary from the range 0.40-3.28 to 0.14-1.02 microg/g for THg, 11.16-107.84 to 8.00-22.38 microg/g for Pb, and 151.67-645.35 to 144.92-343.50 microg/g for Zn. An important finding of the present study is the significant adverse impact of sedimentary heavy metal bioaccumulation to human through the consumption of demersal fishes in the city of Mersin along the southern coast of Turkey.

Determination of trace metals in different fish species and sediments from the River Yeşilirmak in Tokat, Turkey

In the presented study, five different fish species and sediment samples were collected from polluted areas, control samples from unpolluted areas in Yeşilirmak River during 2008-2009. The samples were analyzed using flame and/or graphite furnace atomic absorption spectrometry after various digestion methods. The relative standard deviations (RSD) were found below 10%. The accuracy of the methods was confirmed by certified reference materials. The maximum iron, zinc, copper, lead, manganese, nickel and cadmium concentrations were found to be as 116 (Fe), 63.5 (Zn), 2.5 (Cu), 0.56 (Pb), 9.4 (Mn), 10.2 (Ni) and 0.75 (Cd) microg/g in fish samples. The maximum metal concentration in sediment was 3566 microg/g for Fe, 463 microg/g for Mn, 45.5 microg/g for Zn, 38.7 microg/g for Cu, 17.3 microg/g for Pb, 79.2 microg/g for Ni and 0.55 microg/g for Cd, respectively. Some species is accumulated trace metals at high ratio.

Comparison of arsenic and antimony contents in tissues and organs of brown trout caught from the river Presa polluted by ancient mining practices and from the river Bravona in Corsica (France): a survey study

The present study evaluates the concentrations of arsenic (As) and antimony (Sb) in the intestine, liver, muscle, gonads, gills, and kidney of Salmo trutta subsp. from the Presa River in Corsica (France; n = 10), which crosses an abandoned arsenic mine, and from the Bravona River (reference site; n = 10). Both metalloids were analyzed by means of ICP-MS. The relationships between fish size (length and weight) and metalloid concentrations in their tissues were investigated by linear regression analysis. In all fish samples concentrations of As and Sb (expressed as micrograms per gram fresh weight) were highest in the kidney. Lowest Sb concentrations were found in the muscle, whereas lowest As concentrations were found in the gonads of S. trutta. Two organotropisms were revealed: one for As-kidney (21.4656) > intestine (3.9535) > gills (3.0404) > liver (1.1743) > muscle (0.9976) > gonads (0.8081); and the other for Sb-kidney (0.70067) > gills (0.6181) > intestine (0.2576) > gonads (0.1673) > liver (0.9625) > muscle (0.0753). Results of linear regression analysis in most cases showed a significant negative correlation between metalloid concentration and fish size. Highly significant (p < 0.05) negative correlations were found between fish length and As concentration in the gonads, as well as between fish length and Sb concentrations in the gills. Arsenic concentrations in female fish were significantly higher than those in males in the kidney, gonads, gills, and liver. The same results were found for Sb, except in the liver, where the tendency was reversed.

Arsenic accumulation in a freshwater fish living in a contaminated river of Corsica, France

The impact of arsenic (As) discharge related to a past mining activity in the Bravona River and its tributary, the Presa River, was investigated in an edible fish, the brown trout (Salmo trutta). Fish was sampled in four stations along a contamination gradient. Arsenic was measured in five organs type (operculum, gills, liver, muscle, and axial skeleton). Almost 70 years after the suspension of the mining activity, As levels in water remain high. The results indicated a strong As contamination in fish collected downstream from the mine. The operculum, liver, and gills showed the highest As concentrations whereas levels in muscle were lower. A strong positive correlation between As concentrations in water and in tissues was observed. Bioaccumulation occurred preferentially in the gills, operculum, and liver. Since As levels in tissues of S. trutta followed the pollution gradient, this species appears useful as biomonitor for metalloid accumulation.

Selenium and mercury in native and introduced fish species of patagonian lakes, Argentina

A survey of mercury (Hg) and selenium (Se) contents was performed in fish collected from lakes located in two National Parks of the northern patagonian Andean range. Two native species, catfish (Diplomystes viedmensis) and creole perch (Percichthys trucha), and three introduced species, brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvelinus fontinalis), were caught from lakes Nahuel Huapi, Moreno, Traful, Espejo Chico, and Guillelmo belonging to Nahuel Huapi National Park and from lakes Futalaufquen and Rivadavia, Los Alerces National Park. In lake Moreno, fish diet items were analyzed and rainbow trout grown in a farm. Hg and Se were measured in muscle and liver tissues by instrumental neutron activation analysis. The average concentrations in muscle of Hg for all species, ages, and lakes are between 0.4 to 1.0 microg g(-1) dry weight (DW) with a few fish, mainly native, exceeding the United States Environmental Protection Agency health advisory for freshwater fish limited consumption, and from 0.8 to 1.5 microg g(-1) DW for Se. Average concentrations in liver of Hg in all species range from 0.4 to 0.9 microg g(-1) DW. Brown trout, the top predator in these lakes, showed the lowest average Hg burden in both tissues. Se concentrations in the liver of brown and rainbow trout, up to 279 microg g(-1) DW, are higher than those expected for nearly pristine lakes, exceeding 20 microg g(-1) DW, the threshold concentration associated with Se toxicity. These species show lower Hg contents in muscle, suggesting a possible detoxification of Hg by a Se-rich diet. Creole perch and velvet catfish livers have lower Se concentrations, with a narrower span of values (2.3 to 8.5 microg g(-1) and 3.3 to 5.5 microg g(-1) DW respectively).

Environmental assessment of mercury contamination from the Rwamagasa artisanal gold mining centre, Geita District, Tanzania

This study presents the results of an environmental assessment of mercury (Hg) contamination in the Rwamagasa artisanal gold mining area, northwest Tanzania, and the potential downstream dispersion along the River Malagarasi to Lake Tanganyika. At the time of sampling, generally low concentrations of Hg (<0.05 mg/kg) occurred in most cultivated soils although higher Hg (0.05-9.2 mg/kg) was recorded in urban soils and vegetable plot soils where these are impacted by Hg-contaminated water and sediment derived from mineral processing activities. Hg in vegetable and grain samples is mostly below the detection limit of 0.004 mg/kg Hg, apart from 0.007 and 0.092 mg/kg Hg in two yam samples and 0.011 to 0.013 mg/kg Hg in three rice samples. The standardized (i.e., standardized to 10 cm length) Hg concentrations in Clarias spp. increase from about 0.01 mg Hg/kg for the River Malagarasi delta to 0.07, 0.2, and 1.6 mg/kg, respectively, for the Rwamagasa 'background', moderately and most contaminated sites. For piscivorous (Lates, Brycinus, and Hydrocynus spp.), insectivorous (Barbus spp.), and planktivorous (Haplochromis spp.) fish species, the 10-cm standardized Hg concentrations increase from about 0.006 mg/kg for the River Malagarasi-Lake Tanganyika area to 0.5 and 3.5 mg/kg, respectively, for the Rwamagasa moderately and most contaminated sites. The low concentrations of Hg in fish from the Malagarasi River delta and Lake Tanganyika indicate that Hg contamination from the Rwamagasa area does not have a readily discernible impact on the biota of Lake Tanganyika. Many of the fish samples from Rwamagasa exceed guidelines for human consumption (0.5 mg/kg) as well as the WHO recommended limit for vulnerable groups (0.2 mg/kg). Tissue total Hg (THg) of all fish collected from the River Malagarasi-Lake Tanganyika subarea is well below these guidelines. Potential human exposure through consumption of 300 g/day of rice grown on Hg-contaminated soils is 5.5 microg/week. Consumption of 250 g Nile perch (Lates spp.), 500 g tilapia (Oreochromis spp.), and 250 g of catfish (Clarias spp.) each week would result in an intake of 65 microg Hg/week for people consuming only fish from the Mara and Mwanza regions of Lake Victoria and 116 microg Hg/week for people in the Rwamagasa area consuming tilapia and Nile perch from Lake Victoria and catfish from mining-impacted streams. This is lower than the Provisional Tolerable Weekly Intake (PTWI) of 300 microg for Hg in the diet set by the WHO and the FAO. Inadvertent ingestion of soil containing 9 mg Hg/kg at a rate of 80 mg/day would give an additional estimated weekly intake of 5 microg THg, whereas the persistent and purposeful consumption of soil (geophagia) at a rate of 26 g soil/day would produce an additional chemical exposure of 230 microg Hg/day.

Silver contamination on abiotic and biotic compartments of Nahuel Huapi National Park lakes, Patagonia, Argentina

The Ag contents of abiotic and biotic compartments of different lakes of Nahuel Huapi National Park, Patagonia, Argentina were analyzed. The water bodies studied were lakes Nahuel Huapi, Moreno, Escondido, Espejo Chico and Traful, the latter chosen as a reference lake. The Ag concentration profiles of short sediment cores, dated by (210)Pb and (137)Cs techniques, were analyzed, as well as suspended load collected from three sites of lake Nahuel Huapi. The biota studied were the native mussel Diplodon chilensis (digestive gland and total soft tissues pooled samples) and five species of fish, two native and three introduced (liver and muscle pooled samples). Ag contents were determined by Instrumental Neutron Activation Analysis (INAA). The upper layers of the sediment cores sampled in lake Nahuel Huapi were enriched in Ag contents compared to deep layers in accumulation periods corresponding to the second half of the 20th century, but this enrichment was neither observed in the reference lake Traful, nor in lakes Espejo Chico and Escondido. Ag was enriched over background level (0.1 microg g(-1)) also in suspended load collected in lake Nahuel Huapi. Ag fluxes to sediments were computed for suspended load and enriched sediment core layers. Highest Ag fluxes, from 350 to 470 microg m(-2) year(-1), were measured in Nahuel Huapi near the site where the liquid effluents of the Bariloche city sewage treatment plant are released to the lake. The spatial distribution of the other Ag fluxes suggests that this is the main source of Ag to lake Nahuel Huapi and lateral transport occurs within the water body. Ag concentrations on biota samples were consistent with these conclusions. Mussels collected in lake Nahuel Huapi showed higher Ag concentrations than in the other lakes, especially when compared to lake Traful. Ag contents in mussels were strongly associated with sediment intake, but enriched probably due to sediment grain size sorting during the intake processes. Evidence of food chain biomagnification of Ag in fish liver was observed. Ag contents in fish liver were higher at lake Nahuel Huapi even considering the high intra-specific variability, with highest values ranging from 10 to 29 microg g(-1) dry weight for brown trout and rainbow trout.

Copper and zinc in four freshwater fish species from Lake Pamvotis (Greece)

Lake ecosystems are vulnerable to heavy-metal pollution. Fish samples are considered as one of the most indicative factors, in freshwater systems, for the estimation of trace metals pollution potential. Lake Pamvotis (NW Greece) is a typical Mediterranean ecosystem of great importance in regard to biodiversity and to aesthetic value. The fish species found most commonly in the lake are Cyprinus carpio, Silurus aristotelis, Rutilus ylikiensis, and Carassius gibelio. The aim of the present study is to evaluate the level of contamination of two essential heavy metals (copper and zinc) appearing at high concentrations in lake water in the above four fish species. Metal concentrations were measured by atomic absorption spectroscopy in three different tissues (muscle, liver, gonads) in order to assess the fish contamination. A two-factor analysis of variance, based on the procedure of general linear models, was employed in which fish species (four levels) and fish tissue (three levels) were examined for potential influence on Cu and Zn concentrations. Differences between level means per factor were treated using Tukey's multiple comparisons of means. The study showed that C. carpio and R. ylikiensis presented the highest metal content. Tissues analysis revealed that liver and gonads accumulated the highest levels of Cu and Zn. Metal concentration in the edible part of the examined fish (muscle) were in the safety-permissible levels for human consumption.

A review of mercury in Lake Victoria, East Africa: implications for human and ecosystem health

Lake Victoria, East Africa, has been the site of many recent studies measuring mercury (Hg) concentrations in water, fish, sediment, soil, and humans. Most of these studies were motivated by concerns about Hg contamination from processing of gold ore on the southern shores. Total Hg (THg) concentrations in fish were usually below permissible World Health Organization (WHO) concentrations and international marketing limits and do not threaten the lucrative export industry. Nile perch 3-10 kg and most >10 kg had THg concentrations above the WHO threshold concentrations for at-risk groups (200 ng/g). Elevated THg concentrations in large Nile perch are not of major concern because Nile perch are rarely consumed by the people living on Lake Victoria and very large Nile perch are becoming increasingly rare in catches. Water THg concentrations were below Canadian drinking water guidelines but were elevated relative to those in the northern Great Lakes. Sediment and soil THg concentrations were within inter-national guidelines and are comparable to those in northern latitudes but are lower than those in the Amazon basin. Biomass burning and soil erosion are estimated to be the major sources of THg for the lake and probably constitute a larger source of THg than gold mining in Tanzania.THg concentrations in urine and hair from human volunteers indicate that while gold miners and frequent skin-bleaching cream users are at risk of inorganic mercury poisoning, the rest of the population, including fishermen, is not. Human exposure assessments demonstrated that fish consumption and soil geophagy constitute major sources of THg for humans, but the total estimated daily intake of THg was below the Health Canada tolerable daily intake (TDI) limits. The use of beauty creams containing high inorganic Hg concentrations, however, caused the estimated THg exposure to exceed the TDI. The high THg content in the hair of regular cream users supports this assessment. The nutritional benefits of fish and soil geophagy outweigh the risk of THg poisoning. Still, due to the importance of those natural items as a THg source to humans, as well as the changing nature of Lake Victoria, regular monitoring and risk assessments need to be carried out in the Lake Victoria catchment.

Heavy metals in the vicinity of a chlor-alkali factory in the Upper Negro River ecosystem, Northern Patagonia, Argentina

A study on heavy metal contents was performed in sediments and biota of the Upper Negro River (Alto Valle) aquatic system, Northern Patagonia, Argentina. The irrigation system of the Neuquén and Negro Rivers runs alongside these rivers for 150 km, supporting intensive agricultural and economical activities, mainly related to fruit production. A mercury cell chlor-alkali factory operated between 1951 and 1995. Close attention was given to the surroundings of the plant, located next to the Main Irrigation Channel, and to the PII drainage channel which received the plant's effluents between 1951 and 1979. From 1979 until its closure, the effluents were pumped above a ravine to a series of evaporation and decantation pools. Mercury and other heavy metals and metalloids (Ag, As, Ba, Co, Cr, Cs, Ni, Sb, Se, U and Zn) contents were measured for bottom sediments of the river and irrigation and drainage channels, for two widespread species of macrophytes (Potamogeton pectinatus and Myriophyllum brasiliensi), and for liver and muscle of native fish Odontesthes microlepidotus. River bed sediments show no evidence of heavy metal accumulation, however, biota might indicate that contaminants are entering the rivers. Mercury was the only element accumulated in the Main Irrigation channel sediments, the highest contents occurring in the surroundings of the nowadays shut-down chlor-alkali plant, returning to background values approximately 40 km downstream the plant. At the plant site, sediments from the center of the channel showed a decrease in Hg content in the upper 10 cm layer, ranging from 0.8 to 3.4 microg g(-1), and from 2.8 to 13.7 microg g(-1) in the next 10 cm lower layer. Conversely, the PII drainage channel sediments showed accumulation of Hg (2-4 microg g(-1)), distributed uniformly at different depths and along the channel, until its mouth at Negro river. Mercury contents of macrophytes downstream the chlor-alkali plant are higher than the baseline for the area, and macrophytes and fish liver from the PII drainage channel present the highest content in this element. The drainage channel system showed different degrees of impact, those channels flowing through densely populated areas being the most affected.

Trace metal concentrations in water, sediments and fish tissue from Lake Tanganyika

Trace metal (Cu, Pb, Fe, Mn, Zn, Cd) concentrations were determined in water, sediments, various fin fish species and a bivalve (Mutela spekei) from Lake Tanganyika using an atomic absorption spectrophotometer. Integrated water samples to depths of 10 m were collected using a pre-rinsed flexible plastic pipe. Sediment samples were collected using a ponar mud sampler. Fish samples were obtained using a variety of fishing techniques. No differences in trace metal concentrations were observed in both inshore and offshore waters. Levels in inshore sediments were much higher than for the offshore ones. Sediment input through run-off may have been the cause for the differences. However, the levels were much lower than those reported for Lake Malawi sediments. The concentrations in the fish tissue were within ranges reported elsewhere for Lake Tanganyika fish species. The centrapomid Lates stappersii and the clupeids Limnothrissa miodon and Stolothrissa tanganicae are the most important commercial species in the lake followed by Lates marie. Lead and cadmium are of concern to human health. The mean concentrations of the two metals in the commercial fish species were as follows: L. stappersii (5.03 microg Pb/g, 0.28 microg Cd/g); L. marie (4.96 microg Pb/g, 0.25 microg Cd/g); L. miodon (4.64 microg Pb, 0.38 microg Cd); and S. tanganicae (4.96 microg Pb/g, 0.39 microg Cd/g). Levels of lead and iron in the bivalve species were exceptionally very high, being 11.08 and 6.54 mg/g, respectively.

Selenium and mercury concentrations in some fish species of the Madeira River, Amazon Basin, Brazil

Samples of 7 species of piscivorous, omnivorous, and herbivorous fish caught at 12 different sites on the Madeira River, Amazon Basin, were analyzed for selenium and mercury. Selenium was determined by anodic stripping voltammetry and mercury by cold vapor atomic absorption spectrophotometry. The means for selenium concentrations ranged from 0.49 to 3.11 nmol/g and for mercury from 0.41 to 6.66 nmol/g depending on the fish species. The molar ratios of Hg:Se increased according to the fish trophic level. Piscivorous species had the highest mean ratio (4.0) and herbivorous species the lowest (0.9). There was a positive and statistically significant correlation between selenium and mercury concentrations for the herbivorous species (r = 0.716; p = 0.0088) not seen for omnivororus and piscivorous species (r = -0.2032; p = 0.3407). These findings are significant for the fish-eating population of the Madeira River because the ingestion of mercury would always be in excess of selenium.

Toxic and essential elements in fish from Nordic waters, with the results seen from the perspective of analytical quality assurance

Fish from fresh, brackish and marine waters were analysed for their levels of Pb, Cd, Cr, Ni, Co, Zn, Cu, Mn, As and Se in muscle tissue. Various quality control procedures were implemented during the survey and the results were compared with those from several other surveys, most of which were carried out during the 1990s. It was noted that several elements varied widely both within and between studies. A systematic examination of a large number of surveys and ranking of their quality level indicated that a lack of quality control procedures often results in high or varying results. This may have serious consequences when results are used as a basis for for example, legislation or intake recommendations.