Metal concentration in water, sediment and four fish species from Lake Titicaca reveals a large-scale environmental concern

Mercury distribution, bioaccumulation, and biomagnification in riparian ecosystems from a neotropical savanna floodplain, Araguaia River, central Brazil

Litterfall is the main source of dry deposition of mercury (Hg) into the soil in forest ecosystems. The accumulation of Hg in soil and litter suggests the possibility of transfer to terrestrial invertebrates through environmental exposure or ingestion of plant tissues. We quantified total mercury (THg) concentrations in two soil layers (organic: 0-0.2 m; mineral: 0.8-1 m), litter, fresh leaves, and terrestrial invertebrates of the Araguaia River floodplain, aiming to evaluate the THg distribution among terrestrial compartments, bioaccumulation in invertebrates, and the factors influencing THg concentrations in soil and invertebrates. The mean THg concentrations were significantly different between the compartments evaluated, being higher in organic soil compared to mineral soil, and higher in litter compared to mineral soil and fresh leaves. Soil organic matter content was positively related to THg concentration in this compartment. The order Araneae showed significantly higher Hg concentrations among the most abundant invertebrate taxa. The higher Hg concentrations in Araneae were positively influenced by the concentrations determined in litter and individuals of the order Hymenoptera, confirming the process of biomagnification in the terrestrial trophic chain. In contrast, the THg concentrations in Coleoptera, Orthoptera and Hymenoptera were not significantly related to the concentrations determined in the soil, litter and fresh leaves. Our results showed the importance of organic matter for the immobilization of THg in the soil and indicated the process of biomagnification in the terrestrial food web, providing insights for future studies on the environmental distribution of Hg in floodplains.

Efficient Immobilization of heavy metals using newly synthesized magnetic nanoparticles and some bacteria in a multi-metal contaminated soil

Simultaneous application of modified Fe3O4 with biological treatments in remediating multi-metal polluted soils, has rarely been investigated. Thus, a pioneering approach towards sustainable environmental remediation strategies is crucial. In this study, we aimed to improve the efficiency of Fe3O4 as adsorbents for heavy metals (HMs) by applying protective coatings. We synthesized core-shell magnetite nanoparticles coated with modified nanocellulose, nanohydrochar, and nanobiochar, and investigated their effectiveness in conjunction with bacteria (Pseudomonas putida and Bacillus megaterium) for remediating a multi-metal contamination soil. The results showed that the coatings significantly enhanced the immobilization of heavy metals in the soil, even at low doses (0.5%). The coating of nanocellulose had the highest efficiency in stabilizing metals due to the greater variety of surface functional groups and higher specific surface area (63.86 m2 g-1) than the other two coatings. Interestingly, uncoated Fe3O4 had lower performance (113.6 m2 g-1) due to their susceptibility to deformation and oxidation. The use of bacteria as a biological treatment led to an increase in the stabilization of metals in soil. In fact, Pseudomonas putida and Bacillus megaterium increased immobilization of HMs in soil successfully because of extracellular polymeric substances and intensive negative charges. Analysis of metal concentrations in plants revealed that Ni and Zn accumulated in the roots, while Pb and Cd were transferred from the roots to the shoots. Treatment Fe3O4 coated with modified nanocellulose at rates of 0.5 and 1% along with Pseudomonas putida showed the highest effect in stabilizing metals. Application of coated Fe3O4 for in-situ immobilization of HMs in contamination soils is recommendable due to their high metal stabilization efficiency and suitability to apply in large quantities.

Local and landscape factors influencing mercury distribution in water, bottom sediment, and biota from lakes of the Araguaia River floodplain, Central Brazil

Mercury (Hg) is a chemical element widely present in the Earth's crust. However, its high toxicity and ability to accumulate in organisms and biomagnify through food chains characterize it as a global pollutant of primary control. We assessed total mercury concentrations ([THg]) in abiotic and biotic compartments from 98 floodplain lakes associated with the Araguaia River and six tributaries (Midwest Brazil). [THg] quantification in water was performed by cold vapor atomic fluorescence spectroscopy. [THg] in bottom sediment was assessed using cold vapor generation atomic absorption spectrophotometry, while [THg] in macrophyte, periphyton, and plankton were quantified by thermal decomposition atomic absorption spectrometry. Hotspots of [THg] in water, bottom sediment, and macrophytes were determined in areas impacted by pasture and urban areas. In contrast, hotspots of [THg] in periphyton and forest fires were determined in preserved areas downstream. [THg] in plankton did not show a clear spatial distribution pattern. The mean bioaccumulation factor order was plankton (2.3 ± 1.8) > periphyton (1.3 ± 0.9) > macrophytes (0.7 ± 0.4) (KW = 55.09, p < 0.0001). Higher [THg] in water and bottom sediment were associated with high pH (R2adj = 0.118, p = 0.004) and organic matter (R2adj = 0.244, p < 0.0001). [THg] in macrophytes were positively influenced by [THg] in water (R2adj = 0.063, p = 0.024) and sediment (R2adj = 0.105, p = 0.007). [THg] in periphyton are positively related to forest fires (R2adj = 0.156, p = 0.009) and [THg] in macrophytes (R2adj = 0.061, p = 0.03) and negatively related to lake depth (R2adj = 0.045, p = 0.02). The transfer of Hg from water and sediment to the biota is limited. However, the progressive increase of the bioaccumulation factor between macrophyte, periphyton, and plankton may indicate Hg biomagnification along the food chain of the Araguaia River floodplain.

Ecological risk of mercury in bottom sediments and spatial correlation with land use in Neotropical savanna floodplain lakes, Araguaia River, Central Brazil

The Araguaia River floodplain is an important biogeographic boundary between the two largest South American biomes: the Cerrado (Brazilian Savanna) and the Amazon rainforest. The large-scale degradation due to land use conversion experienced in the Araguaia River watershed represents a potential source of mercury (Hg) transport to aquatic ecosystems. However, more information is needed about the dynamics of Hg distribution in savanna floodplains, including the Araguaia River floodplain. We analyzed total mercury (THg) concentrations in the bottom sediments of 30 lakes connected to the Araguaia River and four tributaries, aiming to evaluate the environment's integrity based on the geoaccumulation index (Igeo) and the ecological risk index (ERI). The principal component analysis was applied to examine associations between Hg concentrations, environmental conditions, and land use intensity among lakes associated with different river systems. We used indicator cokriging to identify areas with a greater probability of Hg pollution and ecological risk associated with land use intensity. The land use data showed the predominance of areas used for pasture in the Araguaia River basin. THg concentrations in the sediments varied between 22.6 and 81.9 ng g-1 (mean: 46.5 ± 17.7 ng g-1). Sediments showed no significant pollution (Igeo: 1.35 - 0.50; Classes 1 and 2) and low to considerable ecological risks (ERI: 23.5-85.1; Classes 1 to 3). THg in bottom sediments was associated with land use, water turbidity and electrical conductivity, and sediment organic matter. The indicator cokriging indicates a moderate to strong spatial dependence between land use intensity and Hg, confirming the contribution of anthropic sources to the increment of ecological risk but also the influence of extrinsic factors (such as environmental conditions, geology, and hydrology). Integrating sediment assessment and land use indices with geostatistical methods proved a valuable tool for identifying priority areas for Hg accumulation at a regional scale.

Earlier biomarkers in fish evidencing stress responses to metal and organic pollution along the Doce River Basin

The Doce River Basin (DRB) represents a well-described watershed in terms of contamination by metals, especially after a major environmental disaster of a mining tailing dam failure. Despite the massive mortality of the ichthyofauna, very few studies addressed the risks to the health of wild fish exposed to complex mixtures of pollutants from multiple sources. The present study proposed to investigate earlier responses of fish for assessing the impacts of multiple sources of pollution, considering: different niches of fish and target organs; and the influence of seasonality, associated with their probable sources of pollution. To achieve that, fish were collected along the DRB, and biomarkers responses were assessed in target organs and correlated with the levels of inorganic and organic contaminants. As one of the most prominent responses, fishes from the Upper DRB showed the highest expression of the metallothionein and oxidative stress parameters which were related to the higher levels of metals in this region due to the proximity of mining activities. On the other hand, higher levels of DNA damage and increased AChE activity from fish sampled in the Mid and Lower DRB were more associated with organic contaminants, from other sources of pollution than mining residues. The integrated biomarker responses also revealed seasonal variations, with higher values in fishes from the dry season, and pelagic fish showing greater variation within the seasons. The multivariate analysis integrating suitable biomarkers with chemical data represented an adequate strategy for assessing the ecological risks in the DRB, allowing the identification of distinct spatio-temporal impacts from multiple sources of contaminants. The continued exposure of the ichthyofauna representing future risks reinforces the need for ecological restoration and the protection of the fauna from the Doce River.

Health risk assessment of trace elements in the Tonle Sap Great Lake and the Tonle Sap River in Cambodia during the rainy season

To investigate the potential health risk of trace elements in the Tonle Sap Great Lake system, lake (n = 37) and river (n = 14) water samples were collected and analyzed for 19 trace elements (Ag, Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Se, Tl, U and Zn) using inductively coupled plasma mass spectrometry. As a result, Cd was not detected in any river and lake water samples. Al, Fe and Mn in lake water exceeded the regulation limits of Cambodia, USEPA and WHO. Health risk assessment using the USEPA model indicated that male and female Cambodian residents are at minimal risk of non-carcinogenic effects from single and mixed trace elements through lake and river water consumption. Nevertheless, As, Tl, Co, Ba, Mn and Cr might pose high potential health risks to consumers which requires more attention. Therefore, regular monitoring and further studies are required to investigate the pollution trends and toxic behavior of these trace elements in the Tonle Sap Great Lake system.

Heavy metals (HMs) pollution in the aquatic environment: Role of probiotics and gut microbiota in HMs remediation

The presence of heavy metals (HMs) in aquatic ecosystems is a universal concern due to their tendency to accumulate in aquatic organisms. HMs accumulation has been found to cause toxic effects in aquatic organisms. The common HMs-induced toxicities are growth inhibition, reduced survival, oxidative stress, tissue damage, respiratory problems, and gut microbial dysbiosis. The application of dietary probiotics has been evolving as a potential approach to bind and remove HMs from the gut, which is called "Gut remediation". The toxic effects of HMs in fish, mice, and humans with the potential of probiotics in removing HMs have been discussed previously. However, the toxic effects of HMs and protective strategies of probiotics on the organisms of each trophic level have not been comprehensively reviewed yet. Thus, this review summarizes the toxic effects caused by HMs in the organisms (at each trophic level) of the aquatic food chain, with a special reference to gut microbiota. The potential of bacterial probiotics in toxicity alleviation and their protective strategies to prevent toxicities caused by HMs in them are also explained. The dietary probiotics are capable of removing HMs (50-90%) primarily from the gut of the organisms. Specifically, probiotics have been reported to reduce the absorption of HMs in the intestinal tract via the enhancement of intestinal HM sequestration, detoxification of HMs, changing the expression of metal transporter proteins, and maintaining the gut barrier function. The probiotic is recommended as a novel strategy to minimize aquaculture HMs toxicity and safe human health.

Monitoring pond water quality to improve the production of Labeo rohita (Hamilton, 1822) in Bannu Fish Hatchery of Bannu district, Khyber Pakhtunkhwa province; An Implications for artificial fish culture

Abstract The water quality parameters of a fish pond are essential to be managing properly under control for successful operations of fish culture. Improper management of pond water quality during the juvenile stages can create stressful conditions to produce various harmful diseases, which may decrease the fish quality and results in low profits. The present study was aimed to monitored important water quality parameters of nursery ponds of Labeo rohita culturing in Bannu fish hatchery. The study duration was 75 days extends from 10th June to 24th August 2019 for the successful culture of this specie which can play a significant role in breeding season. Furthermore, the concentration of some heavy metals like copper (Cu), nickel (Ni), manganese (Mn), iron (Fe), cadmium (Cd), and zinc (Zn) in pond water and fry stages of this species was also determined. The data obtained from all water quality parameters were analyzed expressed as range, mean and standard deviation using MS Excel 2013. The obtained results of 75 days study revealed that the water pH & temperature, electric conductivity, total dissolved solids (TDS), and total dissolved oxygen (DO) of pond water samples were found within a tolerable limit except salinity and dissolved ammonia concentration were not permissible for fish growth. The average concentration of heavy metals in pond water exhibited descending order Fe>Ni>Mn>Zn>Cd>Ni, which was found in acceptable ranges. Whereas, the average values of heavy metals in fry stages were in the order of Zn>Fe>Ni>Cu>Cd>Mn, and found within the recommended values of WHO/FAO. Thus, it was concluded from this study that good water quality is a precondition, maintaining balanced levels of water quality parameters is fundamental for both the health and growth of fish culture which is quite necessary for assuring increased fish productivity. It is recommended to monitor and assess water quality parameters on a routine basis for promoting healthy fish culture.

Essential and non-essential metals in three lowland rivers of temperate South America (Argentina): Distribution and accumulation

BACKGROUND

Geographic distribution of essential metals on earth is largely uneven. Therefore, regional specific approaches to assess metal contents in freshwater ecosystems are mandatory. Cd, Cu, Cr, Pb, Ni, Mn and Zn concentrations were measured in water, sediments and fish tocharacterize the partitioning of these essential and non-essential metals in three river ecosystems of the Pampean Plain==.

METHODS

Water, sediment and eight fish species were collected at three rivers from the Pampean Plain. After sample-specific pretreatments, Cd, Cr, Cu, Mn, Ni, Pb and Zn concentrations in water, sediment and muscle were determined in triplicate by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). Contamination (Hakanson´s index) and bioconcentration factors were calculated to assess the degree of contamination and the relationship between the matrices, while the target hazard quotient was estimated to explore the risk to human health from fish consumption.

RESULTS

Water metal concentration was below detection limit in all sampled rivers. Sediments were mostly enriched by Mn (186-474 mg kg^-1) followed by Zn (36.8-40.3 mg kg^-1), whereas in fish, the situation was the opposite, suggesting different biogeochemical pathways and uneven bioaccumulation of these elements. The largest concentrations for all explored metals were invariably recorded in fish from the Sauce Grande River, although only Cd, Cu and Ni in sediments were highest at this site. Indeed, the bioconcentration factor showed that Cd and Zn are actively accumulated by almost all species in all sampled rivers. The Targeted Hazard Quotient based on the muscle metal concentration tissue of the edible fish species (Odontesthes bonariensis) was less than 1.

CONCLUSION

None metal seemed to pose a significant risk for humans. In some sites biota-sediment concentration factors of Cd and Zn and muscle Cd, Cr, Ni, Zn and Pb levels were highest in the silurid Pimelodella laticeps, suggesting that it may be used as a sentinel species for biomonitoring programs in Neotropical fish assemblages.

Analysis of Pyrolysis Characteristics of Oily Sludge in Different Regions and Environmental Risk Assessment of Heavy Metals in Pyrolysis Residue

As a resource treatment method, pyrolysis realizes the recovery of oil and immobilization of heavy metals in oily sludge (OS). The results showed that the composition of OS had little effect on the trend of the whole pyrolysis process, but it had different effects on the mass loss and maximum weight loss rate at each pyrolysis stage. SEM-EDS results showed that the pyrolysis residue had a porous internal structure, which was similar to that of activated carbon. The elements S, Ca, O, Fe, Al, and Si were embedded in the carbon skeleton. After OS pyrolysis, the oil content of the solid residue was far less than 2%, which met the pollution control requirements for comprehensive utilization specified in China's oil and gas industry standard. At the same time, the ratio of exchangeable fraction decreased and the ratio of residual fraction increased after OS pyrolysis. The potential ecological hazard coefficient (E _r) of Cd in OS2, OS2-500, and OS2-600 was greater than 40, which were strong and medium hazards. The E _r values of OS2-700 and other metals were far lower than 40, which were low hazards. With the increase of pyrolysis temperature, the comprehensive ecological hazard index (RI) of heavy metals in the residue gradually decreased and the RI value of OS2-700 decreased to 28.01. Therefore, the pyrolysis residue had an internal porous structure and controllable environmental risk. It could be used as an adsorption material for heavy metals to realize the comprehensive utilization of OS.

Assessment of toxic metal contamination, distribution and risk in the sediments from lagoons used for fish farming in the central region of Peru

Toxic metal contamination, distribution and risk were evaluated in the sediments of three lagoons used for fish farming in the central region of Peru. The distribution of toxic metals in the sediment was in the following descending order of Zn > V > Ni > Cu > Pb > As > Cr > Co > Cd > Sb. Contamination factor (Cf) and geoaccumulation index (I_geo) values for Co, Cr, Cu, Ni, Pb, Sb, V and Zn indicated low contamination and for Cd moderate contamination. The pollution load index (PLI) ranged from 0.3856 to 0.5622; indicating no appreciable contamination and the modified degree of contamination (mCd) corroborated this result. The potential ecological risk (R_i) in the Tranca Grande and Pomacocha lagoons revealed a low potential ecological risk and in Tipicocha a moderate potential ecological risk. HI values < 1 indicated that non-carcinogenic adverse effects were negligible. In adults, the Total carcinogenic risk (TCR) values for As, Cd, Cr, Ni and Pb were less than 1.00E-04, indicating no significant carcinogenic risk. In children, TCR values showed similar behavior with the exception of As. Therefore, considering that fish production for domestic consumption and export is carried out in these lagoons, it is important to continue monitoring toxic metals to protect the health of these ecosystems and human health.

Distribution and Bioaccumulation of Essential and Toxic Metals in Tissues of Thaila (Catla catla) from a Natural Lake, Pakistan and Its Possible Health Impact on Consumers

Although fish are often recommended as a component of a healthy diet, the environmental accumulation of heavy metals in many fish species has been of considerable concern for those weighing the nutritional health benefits against adverse toxic outcome of excess intake of toxic metals. This study aimed to determine the concentration of essential and toxic metals in the tissues of Catla catla in Mangla Lake and to assess the possible risk to the consumers. Fifty samples of Catla catla were collected from Mangla Lake, Mirpur, Azad Jammu and Kashmir, Pakistan and analyzed for eighteen metals including essential and trace metals. The measured range concentrations (µg/g, wet weight) in muscle tissues, in decreasing order, were: K (955–1632), Ca (550–2081), Na (449–896), Mg (129–312), Zn (61.2–215), Fe (11.6–26.8), Sr (2.60–9.27), Pb (1.72–7.81), Se (1.55–3.55), Co (0.12–4.08), Mn (1.04–4.33), Ni (0.69–3.06), Cu (0.88–2.78), Cr (0.45–1.88), As (0.67–1.58), Cd (0.28–0.56), Hg (0.17–0.57) and Li (0.12–0.38). The metal concentrations found in this study were comparatively higher than those reported in literature. A majority of the metals exhibited higher accumulation in gills compared with those in scales and muscles. Mean levels of Pb, As, Co, Mn, Cd, Cr and Zn in Catla catla muscle were found to be exceeding the international permissible limits for the safe human consumption. The condition factor (K), as an indicator of fish health status, indicated that Catla catla of Mangla Lake are in good health condition. The metal pollution index (MPI) of gills (27.9), scales (12.5) and muscle (7.57) indicated low contamination. Moreover, human health risk was evaluated using estimated weekly intake (EWI) and daily intake (EDI), target hazard quotient (THQ), hazard index (HI) and target cancer risk (TCR). Estimated weekly and daily intake values for As, Cd, Cr, Hg, Ni and Pb were higher than provisional permissible tolerable weekly intake and permissible tolerable daily intake while THQ for As, Cd, Cr, Hg, Pb, Se and Zn was higher than 1. The THQ for As, Hg and Pb was several folds higher than 1, indicative of lifetime non-carcinogenic health risks to the consumers. The hazard index indicated cumulative risk, which greatly increased with increasing fish consumption. Target cancer risk indicated that the people eating the Catla catla from Mangla Lake were exposed to As, Cd, Cr, Ni and Pb with a significant lifetime carcinogenic risk. In summary, consumption of Catla catla from this lake was found to be associated with an increased lifetime risk to the general health of the consumers.

An integrated biomarker approach: Non-monotonic responses to cadmium exposure in the suckermouth catfish Hypostomus plecostomus

Environmental risk assessment in aquatic ecosystems typically uses biomarkers to detect interactions between potential hazards and biological systems. Next to knowing environmental contaminant levels in tissues and the environment, it is important to link to potentially deleterious effects at higher levels of biological organization such as biochemistry, physiology, and overall health status. In this laboratory study we assessed the toxicity of waterborne cadmium (Cd) over an exposure range of 0 - 100 µg l^-1 for nine days to the loricariid suckermouth catfish Hypostomus plecostomus. We evaluated the integrated response of the fish at the biochemical to physiological level by means of a suite of tissue biomarkers of exposure and effects, including Cd concentrations in gills, liver metallothioneins (MT) and cholinesterase activity (ChE) in brain, before and after the inhibition of the alkaloid eserine, as well as whole-fish resting oxygen consumption rates and ingestion rate. Tissue biomarkers (MT and ChE) showed a non-monotonic relationship, with maximum/minimum responses at intermediate doses. i.e. 10 and 50 µg l^-1, whereas biomarker responses of fish exposed at 100 µg l^-1 more closely resembled biomarker responses seen at lower concentrations (< 10 µg l^-1). Conversely, the oxygen consumption rate peaked at 100 µg l^-1, suggesting a higher metabolic cost for higher metal exposure, with no significant correlation with fish body condition and food intake. Integrated Biomarker Response (IBR) values peaked at the intermediate exposure concentration of 50 µg l^-1 Cd. The non-monotonic dose-response of the biochemical biomarkers of exposure, together with the higher metabolic rates of fish exposed to 50 - 100 µg l^-1 of Cd and the non-significant effects on the more relevant physiological and histological variables suggests that H. plecostomus is capable of biochemically and physiologically regulating moderately high Cd concentrations, thus representing a suitable indicator organism to monitor metal pollution by Cd.

Microbial diversity in intensively farmed lake sediment contaminated by heavy metals and identification of microbial taxa bioindicators of environmental quality

The cumulative effects of anthropogenic stress on freshwater ecosystems are becoming increasingly evident and worrisome. In lake sediments contaminated by heavy metals, the composition and structure of microbial communities can change and affect nutrient transformation and biogeochemical cycling of sediments. In this study, bacterial and archaeal communities of lake sediments under fish pressure contaminated with heavy metals were investigated by the Illumina MiSeq platform. Despite the similar content of most of the heavy metals in the lagoon sediments, we found that their microbial communities were different in diversity and composition. This difference would be determined by the resilience or tolerance of the microbial communities to the heavy metal enrichment gradient. Thirty-two different phyla and 66 different microbial classes were identified in sediment from the three lagoons studied. The highest percentages of contribution in the differentiation of microbial communities were presented by the classes Alphaproteobacteria (19.08%), Cyanophyceae (14.96%), Betaproteobacteria (9.01%) y Actinobacteria (7.55%). The bacteria that predominated in sediments with high levels of Cd and As were Deltaproteobacteria, Actinobacteria, Coriobacteriia, Nitrososphaeria and Acidobacteria (Pomacocha), Alphaproteobacteria, Chitinophagia, Nitrospira and Clostridia (Tipicocha) and Betaproteobacteria (Tranca Grande). Finally, the results allow us to expand the current knowledge of microbial diversity in lake sediments contaminated with heavy metals and to identify bioindicators taxa of environmental quality that can be used in the monitoring and control of heavy metal contamination.

Local and downstream cumulative effects of traditional meadow management on stream-water quality and multiple riparian taxa

Water quality and riparian communities are among the most affected stream components by agriculture. However, little is known about the effects of riparian management for both aquatic and terrestrial taxa at different spatial scales. Here, we surveyed aquatic (diatoms) and terrestrial taxa (bryophytes, vascular plants, litter-dwelling snails, and ground and volant arthropods), to compare the abundance and richness of riparian taxa and chemical quality between reference and exposed sites in two stream reaches each of c. 3.5 km in northwestern Spain. Impacts in exposed sites were mainly due to traditional farming practices (TFPs), which included traditional meadow management, weirs built for now-unused water mills and sporadic timber harvesting. Therefore, we measured ten covariates and predictors related to the intensification of TFPs at local and within-stream scales and explored associations with riparian and water-quality measures to study the potential effects of TFPs in more detail. Reference and exposed sites did not differ significantly in water properties (diatom-biotic indices, conductivity, total organic carbon and nitrates), but exposed sites had less concentrations of soil metals Cd, Cu, Ni and Zn and less cover and richness of riparian trees, as inferred by the index QBR. Exposed sites had more volant insect decomposers and reference sites a greater abundance or richness of snails, ground predators and decomposers. Bryophyte richness was greater in reference sites. Our inferences may inform the joint cumulative downstream effects of weirs, meadow uses and riparian alterations but were generally consistent with most riparian taxa benefiting from having larger forested areas. Given the contrasting responses among taxa, we argue that land snails, terrestrial flies, and centipedes may be valuable additions to current riparian assessments mostly based on plants, beetles and spiders as indicator taxa. Our study also suggests caution when inferring farming impacts on streams from the surface area of pastoral land.

Spatial distribution, partitioning, ecological risk and source apportionment of potential toxic elements in water and sediments of the Hoor Al-Azim wetland and their bioaccumulation in selected commercial fish species

The potentially toxic elements (PTEs) concentrations in water and sediments were measured in the Hoor Al-Azim wetland to evaluate the spatial distribution, pollution rate, fate, partitioning, and ecological risk and also to recognize the PTEs sources in sediments using MLR-APCs (multiple linear regression-absolute principal component scores) receptor model. The human health risk was investigated based on the seven fish species consumed in the study area. Based on the results, water and sediment contamination was observed at some stations in the southern part of the wetland where agricultural water drains. Also, the sediments of oil well drilling disposal site was polluted by PTEs. Based on the MLR-APCs model, 80.8% of Mo and 81.5% of Se originated from agricultural source. Total target hazard quotients (TTHQ) values suggested that the children could experience adverse health effects due to consumption of Coptodon zillii, Aspius vorax, Carassius auratus and Carasobarbus luteus.

A Quantitative Assessment and Biomagnification of Mercury and Its Associated Health Risks from Fish Consumption in Freshwater Lakes of Azad Kashmir, Pakistan

Issues regarding biomagnification of mercury (Hg) due to its persistence, bioaccumulation, and toxicity in freshwater lakes have gained much attention in the last two decades especially in remote regions of the world where anthropogenic inputs are considered as negligible. In this study, spatial distribution of total mercury (THg), interspecific accumulation patterns, trophic transfer, and associated health risks in fish of freshwater lakes (357-3107 masl) in Azad Kashmir, Pakistan, were investigated. THg concentrations in the regions were 0.20 ± 0.08 μg g^-1 in glacial, 0.54 ± 0.21 μg g^-1 in rural, and 1.35 ± 0.46 μg g^-1 in urban region. Omnivorous, herbivorous, and carnivorous fish showed THg concentrations of 0.94, 0.85, and 0.49 μg g^-1. Regional, lake, trophic level, and specie-specific differences of THg accumulation were found significant in the study. Among growth parameters, length and age varied significantly among species, trophic levels, and lakes, whereas weight showed significant variation among lakes as well. Condition factor (K) showed significant differences within species, lakes, and trophic levels. Biomagnification was observed in all lakes with the trophic magnification slopes (TMS) ranging from 0.03 to 0.20 with an average of 0.094 ± 0.07. Isotopic values of nitrogen (δ¹⁵N) and condition factor were found to dominate THg accumulation trends; however, no significant health risks were found in the study.

Ecological Risk Due to Heavy Metal Contamination in Sediment and Water of Natural Wetlands with Tourist Influence in the Central Region of Peru

In this study, the quality of sediment and surface water in two natural wetlands, Paca and Tragadero, in the central region of Peru was evaluated using pollution indices, including the geoaccumulation index, pollutant load index, modified pollution degree, potential ecological risk index, and site rank index, for four heavy metals. Principal component analysis was used to identify potential metal contaminant sources. The determination of Fe, Zn, Pb, and As was performed by flame atomic absorption spectrophotometry. The average concentrations of metals in the sediments of both lagoons decreased in the order Fe > Zn > Pb > As. The analysis of the contamination indices determined that As and Pb are the elements that contribute the most to environmental degradation in both wetlands. There is a strong correlation between the values of potential ecological risk and the modified degree of contamination, revealing that the Paca wetland has a moderate degree of contamination and potential ecological risk, while Tragadero presents a high degree of contamination and considerable potential ecological risk. The application of the site rank index showed that more than 50% of the sampling sites have between high and severe contamination. The principal component analysis presented 79.2% of the total variance. Finally, the results of this study are essential in order to carry out preventive actions for environmental protection in these lake ecosystems of great importance for many activities, such as bird watching.

Trace metal contamination and species-specific bioaccumulation in the Zhoushan Fishery, northwestern East China Sea

Metal contamination in fishery water may pose a serious threat to aquatic products and human health. In this study, the contents of seven trace metals were assessed in water, sediment, and ten commercially important species (seven fish and three crustaceans) with different trophic guilds, habitat preferences, and motility, collected from the Zhoushan Fishery, northwest East China Sea. In general, the results showed that the concentrations of trace metals in water and sediment were lower than the safety thresholds set by the National Seawater Quality Standard of China and the sediment quality guidelines, except for Cu, As, and Cr in sediment. The high metal concentrations were spatially distributed in the west of the Zhoushan Fishery, which is probably due to the chemical pollution generated from many large international ports and chemical industries in Hangzhou Bay. The metal concentrations in the species were lower than the legislation thresholds established by the Commission Regulation and China National Standard, except for Cd in two crustacean species. However, a health risk assessment indicated that the consumption of the analyzed seafood is safe. However, there is a potential risk to local consumers who prefer crustaceans. From a species-specific bioaccumulation point of view, species in high trophic guilds, benthivores, species with low motility, or those living near the sediment have been found to be most likely to accumulate metals. Our findings could contribute to the understanding of the accumulation tendencies of metals in species of different trophic guilds with varying habitat preferences and motility and provide valuable data to environmental and seafood safety managers.

Heavy Metal Tolerance Genes Associated With Contaminated Sediments From an E-Waste Recycling River in Southern China

Heavy metal pollution that results from electronic waste (e-waste) recycling activities has severe ecological environmental toxicity impacts on recycling areas. The distribution of heavy metals and the impact on the bacteria in these areas have received much attention. However, the diversity and composition of the microbial communities and the characteristics of heavy metal resistance genes (HMRGs) in the river sediments after long-term e-waste contamination still remain unclear. In this study, eight river sediment samples along a river in a recycling area were studied for the heavy metal concentration and the microbial community composition. The microbial community consisted of 13 phyla including Firmicutes (ranging from 10.45 to 36.63%), Proteobacteria (11.76 to 32.59%), Actinobacteria (14.81 to 27.45%), and unclassified bacteria. The abundance of Firmicutes increased along with the level of contaminants, while Actinobacteria decreased. A canonical correspondence analysis (CCA) showed that the concentration of mercury was significantly correlated with the microbial community and species distribution, which agreed with an analysis of the potential ecological risk index. Moreover, manually curated HMRGs were established, and the HMRG analysis results according to Illumina high-throughput sequencing showed that the abundance of HMRGs was positively related to the level of contamination, demonstrating a variety of resistance mechanisms to adapt, accommodate, and live under heavy metal-contaminated conditions. These findings increase the understanding of the changes in microbial communities in e-waste recycling areas and extend our knowledge of the HMRGs involved in the recovery of the ecological environment.

A critical review on energy recovery and non-hazardous disposal of oily sludge from petroleum industry by pyrolysis

This review systematically reports the pyrolysis of oily sludge (OS) from petroleum industry in regards to its dual features of the energy recovery potential and the environmental risks. The petroleum hydrocarbons are the nonbiodegradable fractions in OS that possess hazardous properties, i.e. ignitability and toxicity. Besides, complicated hazardous elements (i.e. N, S and Cl) and heavy metals inherently existing in OS further aggravate the environmental risks. However, the high oil content and heating value of OS contribute to its huge energy resource potential. Considering the energy demand and the environmental pressure, the ultimate purposes of the OS management are to enhance the oil recovery efficiency to minimize the oil content as well as to stabilize the hazardous elements and heavy metals into the solid residue. Among various OS management technologies, pyrolysis is the most suitable approach to reach both targets. In this review paper, the pyrolysis principle, the kinetics and the product distribution in three-phases are discussed firstly. Then the effects of operating parameters of the pyrolysis process on the quality and the application potential of the three-phase products, as well as the hazardous element distribution are discussed. To further solve the dominant concerns, such as the oil content in the solid residue, the pyrolytic oil quality and the migration of hazardous elements and heavy metals, the potentials of the catalytic pyrolysis and the co-pyrolysis with additives are also summarized. Also, the typical pyrolysis reactors are then presented. From the perspective of the energy efficiency and the non-hazardous disposal, the integrated technology combining the pyrolysis and the combustion for the OS management is recommended. Finally, the remaining challenges of OS pyrolysis encountered in the research and the industrial application are discussed and the related outlooks are itemized.

Long-term impact of accidental pollution on the distribution and risks of metals and metalloids in the sediment of the Longjiang River, China

In January 2012, a serious accident polluted the Longjiang River with high concentrations of cadmium (Cd) and other concomitant metals and metalloids in the water. After emergency treatment (i.e., the addition of coagulants), these metals and metalloids were transferred from the water into the sediment through precipitation of the flocculent materials produced. In this study, the long-term distribution of six metals and metalloids in the sediment of the Longjiang River was investigated and their ecological risks were assessed. Approximately 1 year after the accident (i.e., late 2012), the average Cd content in the sediment of the affected sites decreased to 25.6 ± 19.5 mg/kg, which was 8 times higher than that of 3.16 ± 3.18 mg/kg in the upstream reference sites. In 2016 and 2017, the average Cd content in the sediment of the affected sites further decreased to 4.91 ± 2.23 and 6.27 ± 4.27 mg/kg, respectively. Compared with late 2012, the amounts of Zn, Pb, and Cu obviously decreased in 2016 and 2017, whereas there were no obvious differences in the As and Hg amounts during 3 years considered. Among metals and metalloids, the average contribution of Cd to the potential ecological risk index (RI) was 90%, 69%, and 70% in the affected areas in 2012, 2016, and 2017, respectively, suggesting that Cd was the most important factor affecting the ecological risk of metals in the Longjiang River. It should be noted that the average contribution of Hg to RI in the affected areas increased from 8% in 2012 to 25% and 23% in 2016 and 2017, respectively. The sequence of contribution of six elements was Cd > Hg > As>Pb > Cu ≈ Zn. A high ecological risk of metals and metalloids was found in the sediments of two reservoirs, probably owing to the barrier effect of the dam. This study will be useful for the environmental management of rivers affected by accidental pollution of metals and metalloids.

Mercury Exposure and Toxicological Consequences in Fish and Fish-Eating Wildlife from Anthropogenic Activity in Latin America

Despite the risk of significant adverse toxicological effects of Hg to humans and wildlife, Hg use in anthropogenic activities, and artisanal small-scale gold mining (ASGM) in particular, is widespread throughout Latin America. However, there are few research and monitoring studies of Hg toxicity in fish and fish-eating wildlife in Latin America compared to North America. In the present paper, we reviewed the literature from published articles and reports and summarized and assessed data on Hg in fish from 10 391 individuals and 192 species sampled across Latin America. We compared fish Hg levels with toxicity reference values (TRVs) for fish and dietary TRVs for fish-eating wildlife. We determined that fish, piscivorous birds, and other wildlife are at risk of Hg toxicity. We observed a large disparity in data quantity between North and Latin America, and identified regions requiring further investigation. In particular, future biomonitoring and research should focus on exposure of wildlife to Hg in Peru, Chile, Uruguay, the eastern and northern regions of Brazil, Venezuela, Ecuador, and Colombia. We also discuss Hg risk assessment methodological issues and recommend that future evaluations of Hg risk to wildlife must collect key physiological variables, including age, body size, and ideally Hg-to-Se molar ratios. Integr Environ Assess Manag 2021;17:13-26. © 2020 Environment and Climate Change Canada. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Effects of Contamination by Heavy Metals and Metalloids on Chromosomes, Serum Biochemistry and Histopathology of the Bonylip Barb Fish Near Sepon Gold-Copper Mine, Lao PDR

The objectives of the present study were to determine the concentrations of heavy metals and metalloids in water, sediment and Osteochilus vittatus fish, and to assess chromosome aberrations, serum biochemical changes and histopathological alterations in O. vittatus from the Nam Kok river near the Sepon gold-copper mine, Lao People’s Democratic Republic compared with the reference area. The results showed that Fe, Mn and Ni in water, As and Cd in sediment as well as As, Cd, Cr, Mn and Ni in O. vittatus muscle samples near the gold-copper mine exceeded standard values. Furthermore, the chromosome assessment in O. vittatus revealed seven types of chromosome aberrations, and the highest total number of chromosome aberrations was a centromere gap. The total number of chromosome aberrations, cell number with chromosome aberrations and percentage of chromosome aberrations in O. vittatus as well as serum liver enzymes between the studied areas were significantly different (p < 0.05). The liver histopathological alterations of the fish near the gold-copper mine revealed atypical cellular structures as nuclear membrane degeneration, rough endoplasmic reticulum disintegration and abnormal cytoplasmic mitochondria. The results of this study suggested that heavy metal and metalloid contaminations from the Sepon gold-copper mine area negatively affect O. vittatus fish in terms of chromosomal defects, serum biochemical changes and liver histopathological appearances.

Human Risk from Exposure to Heavy Metals and Arsenic in Water from Rivers with Mining Influence in the Central Andes of Peru

Water pollution by heavy metals is one of the leading environmental concerns as a result of intense anthropogenic pressure on the aquatic environment. This constitutes a significant limitation to the human right of access to drinking water. In this context, the risk to humans from exposure to heavy metals and arsenic in water from rivers subject to mining influence in the Central Andes of Peru was assessed. Water samples were collected from seven rivers at 63 sampling sites, and concentrations of Cu, Fe, Pb, Zn, and As were determined using flame atomic absorption spectrophotometry. Cluster analysis was used to group 21 sampling sites into four groups with similar chemical characteristics, and principal component analysis was used to simplify the complex relationship between the toxic elements by generating two main components with a total percentage of variation of 86%. Fe, Zn, and As had higher percentages of contribution in the Mantaro, Cunas, and Chia rivers. The hazard quotient was highest for children and adults. The hazard index for ingestion of all the studied heavy metals and As was higher than the threshold value (HIing > 1). HIing in 43% of the rivers indicated that the adult population is at risk of non-carcinogenic effects, and HIing in 14% of the rivers revealed a very high health risk. The risk of cancer by ingestion for children varied from medium to high risk and for adults from low to high risk.

Evaluation of the water quality in a conservation unit in Central-West Brazil: Metals concentrations and genotoxicity in situ

This study assessed the quality of vegetation cover in the Parque Estadual das Várzeas do Rio Ivinhema (PEVRI, Upper Paraná River basin, MS, Brazil), the concentration of metals (Cd, Pb, Cr, Cu, Fe, Zn and Ni) in water and muscle and hepatic tissues of five fish species collected in the PEVRI - Hemiodus orthonops, Leporinus friderici, Prochilodus lineatus, Pterodoras granulosus and Pimelodus maculatus - in addition to non-carcinogenic risk assessment and genotoxicity potential in these species. Regarding vegetation index, we found that only 26.25% of the PEVRI area is occupied by denser vegetation. In the sites analyzed, Cd, Cu, Fe and Ni showed high concentrations in water, above the reference values established by the legislation. In the muscle and hepatic tissues of the fish species analyzed, Cd and Pb values exceeded the reference limits. The genotoxic alterations identified in erythrocytes of the fish species studied were nuclear invagination, nuclear budding, picnosis, binucleated cell and lobulate nucleus. For the non-carcinogenic risk assessment in fish, Cd and Pb presented values greater than 1, indicating risk in the consumption of these fish. In the bioaccumulation factor, Cd and Pb were greater than 100 in all fish species analyzed, except for Pb in L. friderici. The results indicated that the water resources of the PEVRI are being affected by some type of contaminant, probably due to anthropic activities carried out around the park or carried from the upper portions of the basin through the drainage system.

De novo assembly and annotation of the transcriptome of Astyanax lacustris liver unveil candidate genes to monitor response to environmental stress

Astyanax lacustris is a freshwater characid fish species that inhabits small streams, lakes and rivers in South America. These fish are abundant in the wild and highly adaptable in captive, being considered a good model for ecotoxicological studies. Nevertheless, there are only shortcoming gene sequence information available in public databases, which hinder their use in more comprehensive investigations that employ sensitivity molecular biology techniques to assess gene expression profile for biomarker identification. In this study, we report the first de novo transcriptome of A. lacustris liver with the aim of improving gene sequence data available for this fish species. Illumina sequencing generated 79,102,610 raw reads, which were filtered in 62,041,259 high-quality transcripts. De novo assembly resulted in 93,888 unigenes and 120,674 isoforms of an average length of 909.12 and 1046.50 bp, respectively. 60,495 isoforms (50.13%) were functionally annotated against seven databases, retrieving homology queries for about 46% of all isoforms. Therefore, in this study we provide information of relevant genes associated to environmental stress and contamination of A. lacustris, enabling future ecotoxicological researches and other molecular studies using this fish species as model.

The combined effect of Cr(III) and NaCl determines changes in metal uptake, nutrient content, and gene expression in quinoa (Chenopodium quinoa Willd.)

Many areas of the world are affected simultaneously by salinity and heavy metal pollution. Halophytes are considered as useful candidates in remediation of such soils due to their ability to withstand both osmotic stress and ion toxicity deriving from high salt concentrations. Quinoa (Chenopodium quinoa Willd) is a halophyte with a high resistance to abiotic stresses (drought, salinity, frost), but its capacity to cope with heavy metals has not yet been fully investigated. In this pot experiment, we investigated phytoextraction capacity, effects on nutrient levels (P and Fe), and changes in gene expression in response to application of Cr(III) in quinoa plants grown on saline or non-saline soil. Plants were exposed for three weeks to 500 mg kg^-1 soil of Cr(NO₃)₃·9H₂O either in the presence or absence of 150 mM NaCl. Results show that plants were able tolerate this soil concentration of Cr(III); the metal was mainly accumulated in roots where it reached the highest concentration (ca. 2.6 mg g^-1 DW) in the presence of NaCl. On saline soil, foliar Na concentration was significantly reduced by Cr(III). Phosphorus translocation to leaves was reduced in the presence of Cr(III), while Fe accumulation was enhanced by treatment with NaCl alone. A real-time RT-qPCR analysis was conducted on genes encoding for sulfate, iron, and phosphate transporters, a phytochelatin, a metallothionein, glutathione synthetase, a dehydrin, Hsp70, and enzymes responsible for the biosynthesis of proline (P5CS), glycine betaine (BADH), tocopherols (TAT), and phenolic compounds (PAL). Cr(III), and especially Cr(III)+NaCl, affected transcript levels of most of the investigated genes, indicating that tolerance to Cr is associated with changes in phosphorus and sulfur allocation, and activation of stress-protective molecules. Moderately saline conditions, in most cases, enhanced this response, suggesting that the halophytism of quinoa could contribute to prime the plants to respond to chromium stress.

Interactive effects of diclofenac and copper on bioconcentration and multiple biomarkers in crucian carp (Carassius auratus)

Diclofenac (DCF), a non-steroidal anti-inflammatory drug, is widespread in aquatic environments and coexists with heavy metals to form combined pollution. However, the interactive effects of DCF and heavy metals on aquatic organisms remain unknown. This study aimed to investigate the interactive effects of DCF and copper (Cu) on the bioconcentration, oxidative stress status and detoxification-related gene expression in crucian carp (Carassius auratus). Fish were exposed to Cu (100 μg L^-1) and DCF (1, 10, 100 and 1000 μg L^-1) alone or in combination for 7 days. Results obtained showed that the treatment of Cu combined with high levels of DCF (100 and 1000 μg L^-1) significantly decreased tissue concentrations of DCF and Cu compared to the correspondingly individual exposure. Concerning oxidative stress status, as reflected by the activities of antioxidant enzymes and malondialdehyde content, low exposure concentrations of DCF (1 and 10 μg L^-1) seemed to mitigate the oxidative stress induced by Cu, whereas the co-exposure of Cu with the highest level of DCF (1000 μg L^-1) led to stronger oxidative damage in fish liver than Cu exposure alone. With regarding to detoxification-related genes, in most cases, the expressions of cyp 1a, cyp 3a, gstα, gstπ, pxr and P-gp in crucian carp were significantly altered upon exposure to the compounds in combination compared to exposure to the compounds individually. Collectively, these findings indicate the capacity of each of these pollutants to alter bioconcentration potential, pro-oxidative effects and detoxification-related gene responses of the other when both co-occur at specific concentrations.

The Variability of Lake Water Chemistry in the Bory Tucholskie National Park (Northern Poland)

The paper presents the results of chemical analysis of lake waters in Bory Tucholskie National Park (BTNP). The BTNP area is unique due to its location within a single catchment and high variability in geological structure. Moreover, the lakes have different morphometric parameters, represent different hydrological types, trophic types and thermal regimes. Another unique feature is the existence of five lobelia lakes. This name comes from the Latin name of the taxon – Lobelia dortmanna L. which has been included in the Polish Red Data Book of Plants. The chemical analysis included 55 parameters, within macro elements (MEs), trace elements (TEs) and rare earth elements (REEs). Low concentrations of MEs, TEs and REEs confirm the absence of anthropogenic pressure. High variation of ME, TE and REE contents between individual lakes is due to different geological structure. The cluster analysis enabled lakes to be divided into six groups taking into account all analyzed water quality parameters. The lobelia lakes were characterized by the lowest concentrations of MEs and REEs, which mainly result from the small catchment area and their mainly endorheic character. The highest variability of MEs, TEs and REEs occurred in endorheic lakes, where the geological structure was dominant. The lowest variability of MEs, TEs and REEs occurred in the lakes connected by the Struga Siedmiu Jezior stream. The analysis of MEs, TEs and REEs in relation to the environmental factors and trophic, hydrologic and thermal typology allowed a better understanding of their spatial distribution in the BTNP lakes. The obtained results indicate that the values of the studied elements were generally close to the average values noted in surface waters according to the Geochemical Atlas of Europe.

Bacterial community rather than metals shaping metal resistance genes in water, sediment and biofilm in lakes from arid northwestern China

Lakes in arid northwestern China are valuable freshwater resources that drive socioeconomic development. Environmental pollution can significantly influence the composition of microbial communities and the distribution of functional genes in lakes. This study investigated heavy metal pollution to identify possible correlations with metal resistance genes (MRGs) and bacterial community composition in water, sediment and biofilm samples from Bosten Lake and Ebi Lake in northwestern China. High levels of zinc were detected in all samples. However, the metals detected in the sediment samples of both lakes were determined to be at low risk levels according to an ecological index. The mercury resistance gene subtype merP had the greatest average abundance (4.61 × 10^-3 copies per 16S rRNA) among all the samples, followed by merA and merC. The high abundance of merA in the pelagic zone rather than in benthic sediment suggests that the pelagic microbial community was important in mercury reduction. Proteobacteria were the main phylum found in the microbial communities in all samples. However, microbial communities in most of the water, sediment and biofilm samples had different compositions, indicating that the habitat niche plays an important role in shaping the bacterial communities in lakes. The microbial community, rather than the heavy metals, was the main driver of MRG distribution. The abundances of some bacterial genera involved in the decomposition of organic matter and the terrestrial nitrogen cycle were negatively correlated with heavy metals. This result suggests that metal pollution can adversely affect the biogeochemical processes that occur in lakes.

Bioaccumulation and health risk assessment of trace metals in fish from freshwater polyculture ponds in Chengdu, China

The freshwater polyculture pond culturing occupied an important position in the aquaculture industry. Accumulation of trace metals was investigated in water, sediments, and fish (Carassius auratus, Cyprinus carpio, Ctenopharyngodon idellus) from typical polyculture ponds in Chengdu, China. The results showed most of the pond water in Chengdu were safe for fish cultivation. The Cd and Cr concentrations in sediment samples from sites S3, S4, and S9 which were near the industrial park and road with a high traffic volume were higher than those of the other sites. Cu, Cr, Fe, Zn, Mn, Ni, and Pb in sediments were unpolluted, while Cd was unpolluted to moderately polluted due to anthropogenic activities. Cu, Cd, and Pb in fish pond sediment of Chengdu had higher potential mobility under normal environmental circumstances. The trace metal concentrations in liver of three fish species were all higher than those in muscle tissues. The order of bioaccumulation factor (BAF) values for trace metals was Cr > Cu > Pb > Zn > Cd > Ni > 20. The concentrations of Cu, Cd, Pb, Zn, and Cr in the muscle of three fish species were all below the local and international maximum permissible levels. The target hazard quotient (THQ) and hazard index (HI) of trace metals in aquaculture fish ponds in Chengdu were lower than 1, which indicated that the consumption of grass, crucian, and common carp cultivated in the aquaculture ponds of Chengdu pose no health risk to the residents.

Effects of water impoundment and water-level manipulation on the bioaccumulation pattern, trophic transfer and health risk of heavy metals in the food web of Three Gorges Reservoir (China)

The Three Gorges Reservoir (TGR) of China, the largest hydropower project over the world, has attracted much attention to the water impoundment and water-level manipulation. In this study, we evaluated potential effects of water impoundment and seasonal water-level manipulation on the bioaccumulation, trophic transfer and health risk of HMs (Cu, Fe, Zn, Hg, Cd and Pb) in food web components (seston, aquatic invertebrate and fish) in TGR. Our results show that, after the impoundment for eight years (2003-2010), all of the six metal concentrations in aquatic biota fell within the criteria of safety quality guidelines. The concentrations of Cu, Fe, Zn and Hg in fish and aquatic invertebrates were higher than those before impoundment, whereas Cd and Pb were lower than those before impoundment. Nonetheless, Hg, Cd and Pb in aquatic consumers underwent an increasing trend during the entire impoundment, implying potential reservoir effect in the future. Only the concentrations of Hg, Cd and Pb in aquatic consumers exhibited a declining trend towards the dam, showing consistent with the background level at the three reaches. Seasonal variations in HM concentrations of fish and aquatic invertebrates were ascribed to the water-level manipulation associated with reservoir management. Our findings show that Hg or Cd biomagnified through aquatic food web during different hydrological periods, whereas Pb, Cu, Fe and Zn exhibited weak biomagnification power. Overall, Hg, Cd and Pb showed a higher risk than that of Cu, Fe and Zn.

Metal Contamination in Seven Tributaries of the Ganga River and Assessment of Human Health Risk from Fish Consumption

We investigated the distribution of Zn, Cu, Ni, Pb, Cr, and Cd in water, sediment, and two dietary fish (an omnivore, Labeo rohita and a benthic carnivore, Clarias batrachus) and potential health risk to human consumers during summer low flow (2017-2018) at 28 sites across 7 tributary confluences of the Ganga River. We selected Devprayag, an upper reach site, as a reference for data comparison. We found significant spatial variations in the distribution of study metals and the concentrations remained higher in tributaries, confluences, and downstream cities. The pollution load index showed all sites except Devprayag in the polluted category. Ecological risk analysis indicated 1 site with very high risk, 7 with considerable risk, and 10 with moderate-risk category. The Zn did appear the most, and Cd the least accumulated metal in the fish. The metal accumulation was higher in C. batrachus. The levels of Cd, Cr, and Pb in the study fishes were higher compared with the international standards. The health risk analysis indicated safe levels for individual metals except for Cd where the target hazard quotient (THQ) did exceed 1 for C. batrachus at the Ramganga and Varuna confluences. When all metals were considered, the THQ was > 1 (> 2 for C. batrachus), indicating the full possibility of adverse health effects to human consumers. Our study highlights the importance of tributaries in creating a mosaic of metal-rich habitats in the Ganga River and food chain associated with a health risk to human consumers.

Health Risks Associated with Heavy Metals in Imported Fish in a Coastal City in Colombia

Colombia is a fish exporter and consumer country because of its geographical location. Since 2012, imported fish have become a more economical option than domestic species due to free trade agreements. Concentrations of Pb, Cd, and Zn were evaluated in three imported and highly commercialized fish species in a city on the Caribbean coast of Colombia: Prochilodus lineatus, Prochilodus reticulatus, and Pangasianodon hypophthalmus, plus one brand of canned tuna and one brand of sardines. The canned species showed the highest values for Pb, Cd, and Zn; canned tuna (oil-packed) contained 0.189 ± 0.047 mg/kg Pb and 238.93 ± 76.43 mg/kg Zn, while canned sardines contained 0.111 ± 0.099 mg/kg Cd, suggesting a relationship between the canning process and the metal concentrations. The estimated daily intake (EDI) and hazard quotient (HQ) suggested that there is no risk for consumer health in the short term, but the presence of these heavy metals certainly should be a concern in the long term because of the bioaccumulation phenomenon due to the high intake of these fish species in this coastal and tourist community. It is recommended that continuous monitoring of heavy metal concentrations take place to protect communities in a local and global context.

Co-pyrolysis of metal contaminated oily waste for oil recovery and heavy metal immobilization

The treatment of metal-contaminated oily waste was investigated by using an approach of co-pyrolysis with hog fuel in a fixed bed reactor. Both oil recovery and heavy metal immobilization were evaluated. Three experimental factors, including pyrolysis temperature, reaction time, and hog fuel addition in the feedstock, were examined to find their effects on the treatment performance. Metal immobilization in the solid char obtained from co-pyrolysis was examined from its speciation characteristics. A higher pyrolysis temperature led to a decreased oil recovery but more non-bioavailable metal species in the char residue. This is also evident from the calculated risk index (RI) for eco-toxicity assessment, with RI of 34.6 and 117.1 at 600 °C and 400 °C, respectively. The addition of hog fuel into oily waste for co-pyrolysis also led to increased metal immobilization but a decreased overall oil recovery. A low temperature co-pyrolysis (400 °C) by adding 20% of hog fuel was found as the most effective oily waste disposal strategy with satisfactory oil recovery and an acceptable risk index of 54.1.

Impacts of suspended sediment and metal pollution from mining activities on riverine fish population-a review

Mining activities are responsible for the elevated input levels of suspended sediment and hazardous metals into the riverine ecosystem. These have been shown to threaten the riverine fish populations and can even lead to localized population extinction. To date, research on the effects of mining activities on fish has been focused within metal contamination and bioaccumulation and its threat to human consumption, neglecting the effects of suspended sediment. This paper reviews the effects of suspended sediment and metal pollution on riverine ecosystem and fish population by examining the possibilities of genetic changes and population extinction. In addition, possible assessments and studies of the riverine fish population are discussed to cope with the risks from mining activities and fish population declines.

Mining waste as a cause of increased bioaccumulation of highly toxic metals in liver and gills of Vardar chub (Squalius vardarensis Karaman, 1928)

Freshwater contamination with mining waste can result with high concentrations of toxic metals in the water and in fish organs. In North-Eastern Macedonia, several rivers (e.g., Zletovska, Kriva) are exposed to acid mine drainage from active Pb/Zn mines. Previous studies confirmed high concentrations of dissolved metals in their water. This study was performed in liver and gills of Vardar chub (Squalius vardarensis Karaman, 1928) from three Macedonian rivers (Bregalnica, Kriva and Zletovska) in spring and autumn 2012. The aim was to establish if increased exposure to certain metals have resulted with their increased bioaccumulation. The concentrations of 19 elements were measured in cytosolic tissue fractions, to obtain information on metabolically available metal species. The following ranges of cytosolic concentrations of highly toxic elements were measured in the Vardar chub liver (in μg/L): Cd, 1.18-184; Cs, 0.25-25.4; Tl, 0.02-5.80; Pb, 0.70-61.1. Their ranges measured in the gills (in μg/L) were the following: Cd, 0.24-59.2; Cs, 0.39-24.4; Tl, 0.01-1.00; Pb, 0.65-87.2. Although the water of the mining impacted Zletovska River was highly contaminated with several essential metals, especially with Mn and Zn, the majority of essential elements (Na, K, Ca, Mg, Co, Cu, Fe, Mn, Mo, and Zn) did not reflect the exposure level. In contrast, seven nonessential elements reflected the level of exposure in the water. Significantly increased hepatic and gill concentrations of Cs, Rb, Sr, and Tl were detected in Vardar chub from the Zletovska River compared to the other two rivers, of Cd and Pb in the Zletovska and Kriva River compared to Bregalnica, and of V in the Bregalnica River compared to Zletovska and Kriva rivers. Observed significant metal bioaccumulation, in particular of highly toxic elements, as a consequence of exposure to water contaminated with mining waste points to necessity of intensified supervision of mining impacted rivers.

Local regulation of immune genes in rainbow trout (Oncorhynchus mykiss) naturally infected with Flavobacterium psychrophilum

Flavobacterium psychrophilum is the etiological agent of bacterial cold water disease (BCWD), also referred to as rainbow trout fry syndrome (RTFS), a disease with great economic impact in salmonid aquaculture. Despite this, to date, not many studies have analyzed in depth how the immune system is regulated during the course of the disease. In the current study, we have studied the transcription of several immune genes related to T and B cell activity in the skin of rainbow trout (Oncorhynchus mykiss) naturally infected with F. psychrophilum in a farm located in Lake Titicaca (Peru). The levels of expression of these genes were tested and compared to those obtained in asymptomatic and apparently healthy rainbow trout. In the case of symptomatic fish, skin samples containing characteristic ulcerative lesions were taken, as well as skin samples with no lesions. Our results pointed to a significant local up-regulation of IgD, CD4, CD8, perforin and IFNγ within the ulcerative lesions. On the other hand, no differences between the levels of expression of these genes were visible in the spleen. To confirm these results, the distribution of IgD⁺ and CD3⁺ cells was studied through immunohistochemical techniques in the ulcerative lesions. Our results demonstrate a strong local response to F. psychrophilum in rainbow trout in which IgD and T cells seem to play a major role.

Environmental health in southwestern Atlantic coral reefs: Geochemical, water quality and ecological indicators

Climate change, pollution and increased runoff are some of the main drivers of coral reefs degradation worldwide. However, the occurrence of runoff and marine pollution, as well as its ecological effects in South Atlantic coral reefs are still poorly understood. The aim of the present work is to characterize the terrigenous influence and contamination impact on the environmental health of five reefs located along a gradient of distance from a river source, using geochemical, water quality, and ecological indicators. Stable isotopes and sterols were used as geochemical indicators of sewage and terrigenous organic matter. Dissolved metal concentrations (Cu, Zn, Cd, and Pb) were used as indicators of water quality. Population density, bleaching and chlorophyll α content of the symbiont-bearing foraminifer Amphistegina gibbosa, were used as indicators of ecological effects. Sampling was performed four times during the year to assess temporal variability. Sediment and water quality indicators showed that reefs close to the river discharge experience nutrient enrichment and sewage contamination, and metals concentrations above international environmental quality guidelines. Higher levels of contamination were strongly related to the higher frequency of bleaching and lower density in A. gibbosa populations. The integrated evaluation of stable isotopes, sterols and metals provided a consistent diagnostic about sewage influence on the studied reefs. Additionally, the observed bioindicator responses evidenced relevant ecological effects. The water quality, geochemical and ecological indicators employed in the present study were effective as biomonitoring tools to be applied in reefs worldwide.

Distribution pattern and pollution status by analysis of selected heavy metal amounts in coastal sediments from the southern Caspian Sea

Amounts of heavy metal elements (Zn, Cd, Pb, Cu, Ni, Co, Mn, and Fe) in surficial sediments at four regions (coastline, estuaries, rivers discharging into the sea, and Gorgan Bay) along the southern coastline of the Caspian Sea were investigated in summer 2015. Collected data was applied to appraise the sediment contamination degree and the origin of pollutants based on the Geo-accumulation Index. Pollution status was assessed via the Enrichment Factor (EF) and the Potential Ecological Risk Index (PERI, the Hakanson index). Heavy metal contents in sediments in mg g^-1 dw varied from 3000 to 39,500 for Fe, 166.66 to 2000 for Mn, 11 to 4198 for Zn, not detected (ND) to 822.83 for Pb, ND to 40.66 for Cd, 6.16 to 37.16 for Cu, 11.66 to 69 for Ni, and 6.33 to 33.00 for Co. Higher amounts of Cd, Pb, Cu, Mn, and Fe were determined in rivers discharging sediments into the sea. In Gorgan Bay, Zn, Ni, and Co were highest. Greater potential ecological risk levels were detected along the coastline as well as rivers discharging into the sea. Among heavy metals considered, Zn and Cd had the highest enrichment factors. The Geo-accumulation Index proved that the investigated region could be classified as Zn- and Cd-polluted area.

Distribution of Cu fraction in sediments using Suaeda heteroptera - Nereis succinea combination: A greenhouse study

A knowledge of the total amount of heavy metals is not enough to assess the environmental impact of polluted soils. Therefore, the determination of Cu fractions in sediment is important to evaluate its behavior in the environment and its mobilization capacity. The distribution of Cu (II) fractions in the sediment was studied in a laboratory simulation experiment. The results indicated that the distribution of Cu fractions was related to the concentration of Cu in sediments. In the Suaeda heteroptera group, the content of exchangeable and carbonate-bound were reducing, while the Fe-Mn oxide- and organic matter-bound were basically raising. In the Nereis succinea group, the content of Fe-Mn oxide- and organic matter-bound were from raising to reducing, and the residual was basically reducing with the increasing Cu concentrations. Generally speaking, the existence of N. succinea could enhance the uptake of Cu in the coastal sediment planted with S. heteroptera. When S. heteroptera and N. succinea in combination, effect of S. heteroptera and N. succinea on Cu fractions in sediments was significantly higher than the two working singly.

Assessment of exposure to metals, As and Se in water and sediment of a freshwater reservoir and their bioaccumulation in fish species of different feeding and habitat preferences

The concentrations of metals (Ag, Al, Ba, B, Be, Bi, Cd, Co, Cr, Cu, Fe, Ga, Hg, Li, Mn, Mo, Ni, Pb, Rb, Sr, Tl, U, V, Zn), As and Se were analyzed in water and sediments from three sites of Río Tercero Reservoir (Córdoba, Argentina) during the wet and the dry season. The dynamics of metals in six fish species (Hoplias malabaricus, Oligosarcus jenynsii, Rhamdia quelen, Bryconamericus iheringii, Astyanax fasciatus and Odontesthes bonariensis) from the reservoir were investigated to discover the possible differential influence of habitat and diet on metal accumulation in the fish. In the abiotic matrix, the highest heavy metal concentrations were observed in sediment. The concentrations of Al, Cu and Pb in water exceeded the limits considered as hazardous for aquatic life. Potential ecological risk analysis of metal concentrations in sediment indicated a low ecological risk in Río Tercero Reservoir in all sampling periods. The enrichment factor indicated that Cu, Pb, Zn and Hg come from anthropogenic sources. Among five different organs, the highest metal levels were found in gills and intestine. Rhamdia quelen and Oligosarcus jenynsii were the species with the highest values of metal accumulation in the whole body. Our study showed that the accumulation pattern of these multi-elements in the different fish species did not respond to diet or habitat, but seemed to be related to the detoxification mechanisms and the metabolism of each organism.

Water-quality impacts in semi-arid regions: can natural 'green filters' mitigate adverse effects on fish assemblages?

The effective aridity in riparian areas is increasing from climate change and from human water consumption, which exacerbates the impacts of effluents from wastewater-treatment plants and from catchment run-off in rivers. The potential of natural riparian areas to act as 'green filters' has long been recognized, but the possible ecological benefits of natural riparian areas over large-scale environmental gradients on fish have not been explored in detail. Using an extensive data-set from northeastern Spain (99,700 km², 15 catchments, 530 sites), ours is the first study to ask whether natural riparian vegetation can mitigate the effects of pollution on fish in rivers experiencing water scarcity. We used multimodel inference to explore the additive and interactive effects of riparian vegetation with nutrient pollution and water conductivity, which are among the world's worst river stressors, on multiple fish guilds, including widely distributed species and highly invasive alien fish species. Most models (54%) supported the additive effects of water-quality factors on fish, after having accounted for the influence of geography and hydrological alterations. Although many fewer models (7%) included riparian vegetation as an important predictor, riparian vegetation modulated the forms of the associations between fish and pollution. The relationship of nutrient pollution with native and alien fish richness changed from negative to positive with greater riparian structure or species richness. However, we found the opposite effect for the mean body size of sedentary fish, and only positive additive effects of riparian richness for the probability of occurrence of pelagic fish. Ammonium and nitrite concentrations adversely affected fish in these rivers up to 10 years after the enforcement of the implementation of the Water Framework Directive by the European Union. High conductivity also much affects fish, having negatives associations with migratory, pelagic, invertivorous and native fish, and positive associations with sedentary, benthic, omnivorous and alien fish. Therefore, the current status of natural riparian areas is unlikely to fully mitigate water-quality impacts on fish. The conservation of freshwater resources in semi-arid regions, such as north-eastern Spain, requires improved waste-water treatments and better agriculture practices.

Metal concentrations and risk assessment in water, sediment and economic fish species with various habitat preferences and trophic guilds from Lake Caizi, Southeast China

Despite the potential emissions of heavy metal pollution in Lake Caizi due to extensive agriculture, urban growth and fishing activities, the risk posed by metal concentrations to aquatic environments and human populations has not yet been studied. In this study we compared the concentrations of Hg, As, Pb, Cd, Cr, Cu and Zn in water, sediment, and economic fish species with different habitat preferences and trophic guilds across important fishery areas in Lake Caizi, located on the northern shore of the Yangtze River, Southeast China. The concentrations of Cr in water were found approximately 6 times higher than the safety thresholds established by international legislation. Cr, Zn, As and Cd concentrations in sediments surpassed the background values for Yangtze River basin in Anhui Province. However, all the studied fish species in Lake Caizi had metal concentrations lower than legislation thresholds established by China and international organizations. Heavy metal concentrations were found to be significantly higher in demersal (inhabiting near the sediments) and piscivorous (possessing higher trophic level) fishes than in pelagic/benthopelagic (inhabiting the upper and lower water column) and herbivorous/planktivorous (possessing lower trophic level) fishes. Our finding demonstrated that the metal concentrations in fishes are simultaneously influenced by the habitat and bio-accumulation through the food chain. According to target hazard quotient (THQ) calculations for heavy metal contents in the muscles of fish species, all the determined heavy metals gave THQ values lower than 1, suggesting the inexistence of health risks from the intake of fishes from Lake Caizi.

Metal detoxification in the marine teleost fish Sparus aurata L. and Dicentrarchus labrax L

Transcription of ATP-binding cassette (ABC) transporters has been evaluated in cell lines and primary cultures from gilthead seabream and European sea bass teleost fish exposed to methylmercury (MeHg), arsenic, cadmium or lead. The mRNA expression levels showed abcb1, abcc2 and abcc5 constitutive gene expression in all seabream tissues analyzed; however, we were unable to detect any constitutive transcription of abcb1 in many of the sea bass tissues. Furthermore, ABC mRNA expression levels were all affected by metal exposure, especially in the case of fish cell lines and erythrocytes, and greatly depended on cell type and fish species. Thus, while ABC transcription was up-regulated in the seabream cell line it was down-regulated in the sea bass cell line, while the opposite occurred in the primary cultures. All these data point to the importance of ABC transporters in metal detoxification and in the differential regulation in seabream and sea bass cells.

Heavy metals and arsenic content in water along the southern Caspian coasts in Iran

Due to the importance of pollution monitoring in marine ecosystems and lack of a coherent and systematic investigation of heavy metal ions along the southern shores of the Caspian Sea, in the present study, the amount of these metals and As ions in coastal waters along its 780-km-long coast in Iran have been studied. Heavy metals (cobalt, nickel, copper, zinc, cadmium, mercury, lead) and a poisonous metalloid (arsenic) were selected in 59 sampling stations and determined using differential pulse polarography method. The multivariate statistical tools were applied to describe and interpret the experimental data. The overall mean concentrations of studied metals (in microgram per liter; μg L^-1) in the samples were found in the order Zn (10.9) > Ni (7.4) > Cu (5.5) > Pb (1.9) > Hg (1.4) > As (1.3) > Co (1.1) > Cd (0.2). The results when compared with reported international standards confirmed that the sampled waters do contain some of these elements above the suggested maximum permissible limits. Hg and Cu were detected in 54.2 and 72.9% of the samples, almost all above the permissible limits. Ni, Zn, Pb, and Co were detected in 100, 96.6, 93.2, and 88.1%, respectively, while 8.5, 22.0, 3.4, and 1.7% were above the permissible limits. Cd and As were present in 61 and 93% of the samples, and their concentrations were higher than the rate presented by Russian System of Management Chemicals (RSMC). In addition, spatial distribution of heavy metal concentrations showed that Gorgan Bay is an ecosystem serving as a filter, trapping natural and anthropogenic materials that are brought from industrial, commercial, and urbanized areas. The multivariate data analysis reveals that Caspian Sea is contaminated by both anthropogenic as well as pedo-geochemical sources.

The Chronic Exposure to Discharges of Sabal Drain Induces Oxidative Stress and Histopathological Alterations in Oreochromis niloticus

To study whether the effluents of Sabal drain could affect the health status of Oreochromis niloticus; site2 (south part of main canal), site3 (at the canal outlet), site4 (north part of main canal) and site1 (reference site) were selected. Compared to the reference fish, activities of superoxide dismutase and glutathione peroxidase in addition to glutathione reduced and thiobarbituric acid reactive substances concentrations of the gills showed significant (p < 0.05) increase with different levels in all studied sites. Whereas, catalase activities revealed significant (p < 0.05) decrease in all studied sites with maximum decrease in site3. The recorded histopathological lesions were correlated with the distance from discharge point. Gills, liver and kidney of site3 had the worst histopathological conditions based on the frequency of alterations appearance and size of the affected areas. While, the regressive alterations that recorded in site2 and site4 suggest the onset of adaptive histological mechanisms.