Spatial monitoring of heavy metals in the inland waters of Serbia: a multispecies approach based on commercial fish

Assessment of trace and macroelement accumulation in cyprinid juveniles as bioindicators of aquatic pollution: effects of diets and habitat preferences

Juveniles of three cyprinids with various diets and habitat preferences were collected from the Szamos River (Hungary) during a period of pollution in November 2013: the herbivorous, benthic nase (Chondrostoma nasus), the benthivorous, benthic barbel (Barbus barbus), and the omnivorous, pelagic chub (Squalius cephalus). Our study aimed to assess the accumulation of these elements across species with varying diets and habitat preferences, as well as their potential role in biomonitoring efforts. The Ca, K, Mg, Na, Cd, Cr, Cu, Fe, Mn, Pb, Sr, and Zn concentration was analyzed in muscle, gills, and liver using MP-AES. The muscle and gill concentrations of Cr, Cu, Fe, and Zn increased with trophic level. At the same time, several differences were found among the trace element patterns related to habitat preferences. The trace elements, including Cd, Pb, and Zn, which exceeded threshold concentrations in the water, exhibited higher accumulations mainly in the muscle and gills of the pelagic chub. Furthermore, the elevated concentrations of trace elements in sediments (Cr, Cu, Mn) demonstrated higher accumulation in the benthic nase and barbel. Our findings show habitat preference as a key factor in juvenile bioindicator capability, advocating for the simultaneous use of pelagic and benthic juveniles to assess water and sediment pollution status.

The influence of climate changes on heavy metals accumulation in Alosa immaculata from the Danube River Basin

This research report provides a comprehensive overview of the historical trends in heavy metal concentrations in the Pontic shad (Alosa immaculata) populations from both the Danube River and the Black Sea, while also exploring the potential influence of global warming on metal accumulation. Through bibliometric modeling analysis, it reveals significant limitations in existing international research, particularly the lack of comprehensive data on the impact of hydroclimatic changes on heavy metal accumulation in Alosa immaculata. Recognizing the critical importance of studies on heavy metal bioaccumulation in Danube shad, this research underscores their significance in defining tolerance thresholds, quantifying the impact of toxic elements along the aquatic food chain, and enhancing the economic sustainability of ichthyofauna monitoring efforts. Furthermore, these studies contribute invaluable insights into the complex dynamics of aquatic ecosystems, offering essential decision-making support for optimizing commercial fishing management practices on the Danube and ensuring robust support systems for industrial fishing endeavors.

The common nase (Chondrostoma nasus) as an indicator of aquatic pollution and human health risk assessment associated with its consumption

Individuals of common nase were sampled from three waterbodies (Kačer river, Zaovine, and Medjuvršje reservoirs) with different characteristics, types, and levels of anthropogenic pressure. The aims of this study were to determine the concentrations of 26 elements in gills, liver, and muscle using inductively coupled plasma optical emission spectrometry (ICP-OES); determine the concentrations of 17 organochlorine pesticides (OCPs) in muscle tissue using gas chromatography with mass spectrometric detection (GC-MS); compare these findings with fish condition (CF); and conduct human health risk and benefit assessments due to consumption of fish meat using target hazard quotient, target carcinogenic risk factor, Se:Hg molar ratio, Na:K and Ca:Mg ratios, and contribution of elements to human diet. Results indicated that in addition to the fact that the type of ecosystem (lentic vs. lotic) plays an important role in the fate and kinetics of pollutants, the degree of anthropogenic pressure is one of the most important factors of environmental pollution - Zaovine and Medjuvršje reservoirs (both lentic ecosystems) had the lowest and the highest levels of pollution, respectively. CF did not reflect the differences in accumulation of all analyzed elements in nase tissues. None of the 17 analyzed OCPs were detected due to the absence of recent use. Fish muscle was the least affected by metal pollution at all studied localities and could be safely used for consumption. We recorded several benefits for human health when using the nase meat in human diet.

Bioaccumulation of potentially toxic elements in fish species of Serbia: a review

In the first review of potentially toxic elements (PTEs) in fish in water ecosystems in Serbia, 40 studies related to fish contamination with PTEs were identified and evaluated. Studies of concentrations of PTEs in fish tissues covered 28 ecosystems (108 localities). The main studied river ecosystems were the Danube and the Sava, and the Međuvršje reservoir was the most studied standing water ecosystem. Among the most studied fish species were catfish (Silurus glanis), followed by pikeperch (Sander lucioperca), bream (Abramis brama), carp (Cyprinus carpio), and barbel (Barbus barbus). There were 48 "hot spot" sampling sites where concentrations of Hg, Cd, Pb, As, Ni, Fe, and/or Cu exceeded the maximum permitted concentrations (MPCs) prescribed by legislation. Elevated concentrations of these elements were the most detected in fish species sampled in the Danube, Sava, and rivers belonging to the Velika Morava basin. Hg concentrations were the most common above MPC in muscle tissue of species sampled from the Danube and Sava rivers. On the other hand, we can single out the species Vimba bream (Vimba vimba), sampled in Danube River in Zemun near Belgrade, as the safest species for human consumption due to the largest number of elements in fish meat below detection limits. Finally, having in mind all the criteria prescribed by U.S. EPA (2000), we identify and recommend two predatory fish species pikeperch (S. lucioperca) and catfish (S. glanis), and bottom-feeding fish species barbel (B. barbus) as bioindicators of PTEs contamination in Serbian waters.

Potentially Toxic Elements in Water, Sediments and Fish from the Karstic River (Raša River, Croatia) Located in the Former Coal-Mining Area

The assessment of the environmental quality of a sensitive karst aquatic system under the centuries-long anthropogenic influence of the coal mining industry is important for both improving the quality of water resources and protecting aquatic wildlife and human health. In this study, we investigated the anthropogenic impact on the aquatic environment of the upper and middle course of the Raša River through the analysis of a suite of metal(loid)s in three aquatic compartments (water, sediment, fish) using inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of inorganic constituents in water were low, while the chemical composition of stream sediments mainly reflected the geological background of the area, indicating the origin of metal(loid)s from predominantly natural sources. Although comparison with PEC-Q values indicated that existing sediment quality conditions could pose a threat to benthic organisms with regard to Cr and Ni, the constant vertical profiles of these elements suggested their natural origin from the weathering of flysch. Element levels in the muscle of targeted fish species were in accordance with the values typical for low-contaminated freshwater systems, while levels of Cd, Pb and Hg were mostly below the European regulatory limits for toxic elements in foods, indicating that the low concentrations of most contaminants in muscles of fish from the Raša River do not present a risk to humans or other consumers. The obtained data indicated a generally low contamination status of the western part of the Raša River basin with regard to the analyzed inorganic elements.

Determination of heavy metals from Aloe vera by- product in golden mullet (Liza aurata); A consumer health risk assessment

Heavy metals have become subject of concern in the recent years because of its potency to cause cardiovascular diseases and other toxic health effects. Therefore, this research was assumed to investigate the level of toxicity in terms of heavy metals accumulation in the fish samples and its benefits and risk for human consumers health and also evaluate the partial replacement of plant sources by canarian Aloe vera diets as a pure product or like a by-product on toxicological effects on the golden mullet (Liza aurata) fillet and whole body. In this study risks arising from fish metal content has been measured using various parameters as Estimated Daily Intake (EDI), Maximum Safe Consumption (MSC_A), Target Hazard quotient (THQ), Hazard Index (HI) Carcinogenic risk of As (As- CR), the Value Selenium Health Benefit (Se HBV) and also the Nutritional Values has been evaluated. The results showed that all heavy metal levels in the fish tissue and diets were below the confirmed safe limits for consumption. In case of diets, it is obvious that with the exception of As, Hg, and Se, the presence of heavy or essential metals in both whole fish and raw fillet in golden grey mullet given experimental diets revealed that the whole fish had the highest concentration. Thus, it can be concluded that Aloe vera product and byproduct were in safety limits for fish and also for humans through food chain. Various risk and benefit assessment measures established by national and international authorities concluded that Liza aurata use was mostly safe.

Potentially toxic elements in invasive fish species Prussian carp (Carassius gibelio) from different freshwater ecosystems and human exposure assessment

Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sn, and Zn were detected in the muscle and gills of Prussian carp from three different freshwater ecosystems: isolated ponds and the South Morava River in Serbia, and Kopačko Lake in complex wetland ecosystem of the Kopački Rit Nature Reserve in Croatia. The main goals of the present research were to assess the concentrations of potentially toxic elements (PTEs) in the muscle and gills of Prussian carp (Carassius gibelio), to examine whether abiotic factors from three different freshwater ecosystems affect the accumulation of PTEs in fish tissues, and to estimate the human health risk resulting from fish consumption. There were only six concentrations of PTEs in the gill tissue (Cr, Hg, Mn, Pb, Sn, and Zn) that were not significantly different among the different freshwater ecosystems. In the muscles, the differences were much less visible. Kopačko Lake distinguished with the highest values of metal pollution index (MPI) for muscles (0.24) and isolated ponds with the highest values of MPI for gills (0.8). The redundancy analysis (RDA) showed that concentrations of Al, Mn, Zn, Cu, and Fe in the gill tissue were significantly correlated with the environmental variables. In contrast, the RDA based on element concentrations in the fish muscles indicated no significant relationship with the environment. Isolated ponds, with no inflow of freshwater, stand out as the most polluted, followed by Kopačko Lake with occasional floods. Flowing freshwater ecosystem South Morava River can be single out as at least polluted with PTEs. The target hazard quotients (THQ) and hazard index (HI) suggested there were no significant noncarcinogenic health risks. The target carcinogenic risk factor (TR) for As and Pb confirmed there were no cancer risks related to human fish consumption. Since the elevated concentrations of toxic Cd and As in Prussian carp were estimated, an early warning should be assumed, especially for fishing activities in these areas.

Bioaccumulation and human health risks of potentially toxic elements in fish species from the southeastern Carajás Mineral Province, Brazil

Anthropogenic activities may have increased the concentrations of potentially toxic elements (PTEs) in fish from the southeastern Carajás Mineral Province in Brazil, which has not yet been studied. The objectives were to determine the quality parameters of surface water and bottom sediments, and to assess the bioaccumulation and risks of Al, Fe, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Ti, V and Zn in fish species from the southeastern Carajás Mineral Province. Water, sediments and fish species (Colossoma macropomum, Curimata cyprinoides, Geophagus sp., Leporinus trifasciatus, and Serrasalmus eigenmanni) were collected in 14 areas in the municipalities of Parauapebas, Marabá and Canaã dos Carajás, contemplating the Gelado Stream and the Parauapebas, Tapirapé and Itacaiúnas Rivers. Water samples were subjected to physicochemical analysis using a multiparameter meter. Concentrations of PTEs in all samples were quantified by inductively coupled plasma-optical emission spectrometry. Enrichment factor (EF) and geoaccumulation index (Igeo) were calculated to study the sediment enrichment and contamination. Ecological and human health risk assessments were performed to determine the risks to the environment and population's health. EF and Igeo revealed that the sediments from the Parauapebas River and Gelado Stream are respectively enriched by Ba, Co, Cu, Cr, Mn, Pb, and Ba, Co, Cr, Ni, Pb and V. The concentrations of Fe (1.67 mg L^-1) and Mn (0.11 mg L^-1) in water and the concentrations of Cr (>0.1 mg kg^-1) and Pb (>2 mg kg^-1) in fish were above the Brazilian legislation thresholds. The ecological risk assessment revealed considerable risk from Ni and moderate risk from multiple PTEs in sediments from the Gelado Stream. Human health risks were detected for Pb in all fish species and for Mo in L.trifasciatus. These results indicate that techniques for monitoring and controlling contamination must be implemented by the environmental agencies.

Seasonal variations of macro-, micro-, and toxic elements in tissues of vimba bream (Vimba vimba) from the Danube River near Belgrade, Serbia

Vimba bream (Vimba vimba) individuals were collected from the Danube River near Belgrade, from May 2016 to May 2017. Samples of muscle and liver tissue were analyzed for concentrations of 25 elements (macro-, micro-, and toxic elements) using inductively coupled plasma optical emission spectrometry (ICP-OES). For both tissues, the highest concentrations of most elements were observed in late spring/early summer (months of May and June). Majority of statistically significant correlations between elements were positive in both tissues. Contributions of Ca, K, and Mg to human diet were in a similar range. The lowest contribution of all macroelements was observed for Na, while the contribution of Se was well above the recommended dietary allowance for this element. Levels of detected elements were well below MAC values prescribed by national and international regulations. The highest value of Hg liver/muscle index (>1) was observed in August, which could indicate a higher contamination of the sampling location in that month. Se:Hg molar ratio never drops below 1, which could indicate that Hg toxicity is prevented. THQ values showed little variation thought the year and were well below the threshold of 1, with the exception of THQ for Al in May (0.92). This element also strongly affects the hazard index.

Emerging and Persistent Pollutants in the Aquatic Ecosystems of the Lower Danube Basin and North West Black Sea Region—A Review

The tremendous impact of natural and anthropogenic organic and inorganic substances continuously released into the environment requires a better understanding of the chemical status of aquatic ecosystems. Water contamination monitoring studies were performed for different classes of substances in different regions of the world. Reliable analytical methods and exposure assessment are the basis of a better management of water resources. Our research comprised publications from 2010 regarding the Lower Danube and North West Black Sea region, considering regulated and unregulated persistent and emerging pollutants. The frequently reported ones were: pharmaceuticals (carbamazepine, diclofenac, sulfamethoxazole, and trimethoprim), pesticides (atrazine, carbendazim, and metolachlor), endocrine disruptors—bisphenol A and estrone, polycyclic aromatic hydrocarbons, organochlorinated pesticides, and heavy metals (Cd, Zn, Pb, Hg, Cu, Cr). Seasonal variations were reported for both organic and inorganic contaminants. Microbial pollution was also a subject of the present review.

Preliminary investigation of lower Danube pollution caused by potentially toxic metals

The current study aims to assess the pollution status of the European river-sea system lower Danube River-Danube Delta-North West Black Sea, through an integrated analysis of metal concentrations in water, sediments and fish community. The Danube flows through numerous industrial cities and receives a significant amount of pollutants due to the reception of urban and industrial emissaries, as well as agricultural land runoff. Samples of water, sediments and fish (10 species) were collected from 7 representative sites along Danube River, Danube Delta and Black Sea shore. For the analysed fish species, potentially toxic and essential elements (Pb, Cd, As, Cu, Fe, Zn, Mg, Ca, Na, K) from muscle and liver samples were measured and discussed. Measurement of elements and other environmental quality parameters were determined for water and sediments. The Black Sea area, represented by S6 and S7, received sediments from Danube with the lowest concentrations of Cd (0.05 ± 0.01 μg g^-1, respectively 0.01 ± 0.001 μg g^-1), Pb (3 ± 0.03 μg g^-1, respectively 2 ± 0.03 μg g^-1), As (2 ± 0.02 μg g^-1, respectively 1.4 ± 0.3 μg g^-1), Ni (8.9 ± 0.1 μg g^-1, respectively 5.2 ± 0.2 μg g^-1), Cr (8 ± 0.7 μg g^-1, respectively 5 ± 0.2 μg g^-1), Cu (3 ± 0.1 μg g^-1, respectively 2 ± 0.04 μg g^-1), Fe(6 ± 0.3 μg g^-1, respectively 3 ± 0.1 μg g^-1) and Zn (0.03 ± 0.003 μg g^-1, respectively 0.017 ± 0.001 μg g^-1). These results suggest that the Danube Delta system plays an important role in filtering the pollutants. Based on the biota and water analysis, there was no correlation observed between Cd, respectively Pb concentration in the environment and fish body (Person Coef. = -0.02 in muscle tissue and -0.01 in liver tissue, respectively Pearson Coeff. = -0.06 in muscle tissue and 0.1 in liver tissue). Cadmium remained an active element in the pollution of the Danube area (S1 and S2), with high concentration in the water matrix (0.14 ± 0.02 μg L^-1, respectively 0.05 ± 0.01 μg L^-1) and fish muscle (0.15 ± 0.03 μg g^-1f.w. in C. carpio - S2). This fact was confirmed by several other studies.

Sensitivity of Bleak (Alburnus alburnus) in Detection of the Wastewater Related Pressure in Large Lowland Rivers

This study deals with bleak (Alburnus alburnus) sensitivity in detecting of the wastewater related pressure in large lowland rivers. The major objective was to investigate if the response measured in bleak should be linked to a certain stretch of the river and characterised as "stretch specific", or it should be linked to the sampling site and characterised as "site specific". The response was evaluated via condition index, metal pollution index, DNA damage and cell viability using integrated biomarker response approach. The study was conducted at 3 sub-sites characterized by different pollution levels in a relatively short stretch (2 km) of the Sava River (Serbia). Results indicated that the response of the biomarkers in bleak can be interpreted as "site specific". Among the studied biomarkers, DNA damage assessed by comet assay and micronucleus test has shown high sensitivity in differentiation of the sites.

Impact of reservoir properties on elemental accumulation and histopathology of European perch (Perca fluviatilis)

This study was conducted on individuals of European perch from six reservoirs in Serbia with different properties, used for different purposes, and situated at different altitudes. Samples of muscle, gills, and liver, as well as water samples, were used for analysis of elemental accumulation. Histopathological (HP) analysis of gills and liver, and Fulton's condition factor (CF) were used as biomarkers. Analysis of Ag, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, and Zn was conducted by inductively-coupled plasma optical emission spectrometry (ICP-OES), and accordingly, metal pollution index and bioaccumulation factor (BAF) were calculated. Elemental accumulation varied considerably both among tissues and reservoirs. Reservoirs located on large low-altitude rivers were the most heavily polluted with metals (Međuvršje, on the Zapadna Morava River, and Lake Sava, on the Sava River). Of three tissues analyzed, the gills were most affected by pollution. The levels of Hg in muscle decreased with an increase in reservoir altitude. Specimens sampled from the highest altitude reservoir were the least affected by HP alterations; however, HP differences between the reservoirs were not statistically significant, and the severity of HP changes was generally low. No significant correlations between the elemental accumulation or HP indices with CF were observed.

Health risk assessment and levels of toxic metals in fishes (Oreochromis noliticus and Clarias anguillaris) from Ankobrah and Pra basins: Impact of illegal mining activities on food safety

Arsenic (As), mercury (Hg), Cadmium (Cd) and lead (Pb) are toxic heavy metals that naturally occur in the ecosystem. Their levels are on the rise due to anthropogenic activities posing threat to aquatic wildlife and humans. In Ghana, pollution of some water bodies has led to unsafe consumption of riverine fishes as well as a shortage of treated potable water principally because the cost of treating polluted water has become expensive across the country. This study aimed to assess the As, Hg, Pb and Cd concentrations in water and fishes from rivers Pra and Ankobrah where activities of artisanal gold mining were carried out resulting in gross pollution of the water bodies. An experimental study was performed to ascertain the levels of As, Hg, Pb and Cd in fish species of Nile tilapia (Oreochromis noliticus) and mudfish (Clarias anguillaris) and aquatic media (water) from the Pra and River Ankobrah basins using the Atomic Absorption Spectrophotometer (AAS) (Varian AA240FS). Both river water samples recorded ranges of 0- 0.0040, 0.0060- 0.0387, 0 - 0.0020, 0.006-0.0093 mg/l for Cadmium, Lead, Arsenic and Mercury respectively. For Cadmium and Arsenic, their levels were comparable (p > 0.05). However, detected values for Lead and Mercury were no comparable (p < 0.05). Toxic metals concentrations in the rivers decreased in the order of Hg > Pb > Cd > As. For the fish samples, values ranged 0-0.08, 0.04-0.42, 0-0.04, and 0.40- 0.60 mg/kg for Cadmium, Lead, Arsenic and Mercury respectively. Generally, appreciably high values were obtained for Mercury. Toxic metals concentrations in the rivers decreased in the order of Hg > Pb > Cd > As. Human health risk assessment from heavy metal exposure through fish consumption from the Rivers for both children and adults showed no significant non-carcinogenic adverse health risk to humans since all calculated values for Hazard Quotient (HQ) were <1. Nonetheless, Target Hazard Quotient (THQ) values calculated for children and adult exposure to Cadmium and Mercury were>1 which implied a likely cause of adverse effects during a person's lifetime.

Metal Accumulation in Muscle and Liver of the Common Nase (Chondrostoma nasus) and Vimba Bream (Vimbavimba) from the Danube River, Serbia: Bioindicative Aspects

Accumulation of 17 elements in muscle and liver of common nase and vimba bream, caught between February and May 2016 in the Danube River (1173 river kilometer), were assessed by ICP-OES. The principal component analysis grouped muscle and liver samples based on element concentrations (muscle grouped by higher Ba and Sr values, and liver grouped by higher Al, B, Cd, Cr, Cu, Fe, Mn, and Zn values), but no grouping between the two species was observed. Concentrations of Ba, Cu, Fe, and Zn were significantly higher in muscle, and concentrations of Ba, Cd, Cu, and Mn in liver of common nase, while vimba bream had significantly higher concentrations of Cr and Fe in liver. Common nase has a higher affinity for bioaccumulation of Cu, Fe, and Zn in muscle, while vimba bream has a higher affinity for Al, Cd, and Cr in muscle.

Geochemical Fractionation and Assessment of Probabilistic Ecological Risk of Potential Toxic Elements in Sediments Using Monte Carlo Simulations

The need for further research into potentially toxic elements in Serbian rivers led to an investigation of distributions, sources, and ecological risks in a sample base of sediments from 15 rivers. The analyses were carried out through both experimental and theoretical methods. Geochemical fractionation of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, As, V, and Zn in sediments was studied using a sequential extraction procedure. Both a Håkanson risk index (RI) and a Monte Carlo simulation (MCS) were used in order to estimate ecological risk, applying the probability distribution of RI values instead of single-point calculations. In order to both further the development of the used method and include additional processes, software for the simulations was developed instead of using proprietary solutions. Metal fractionation showed high percentage recoveries of Cd, Cr, Co, Cu, Fe, Ni, and V in residual fractions. The high content of Pb, Mn, and Zn in mobile fractions might cause serious environmental concerns. In some localities, Cu and Cd could be problematic elements, since their mobility was high. An environmental assessment based on the described criteria provided risk levels varying from low to median (mainly contributed by Cd and Cu).

Potentially toxic elements in muscle tissue of different fish species from the Sava River and risk assessment for consumers

Fish from the Sava River are consumed daily by the local people: therefore, concern has been raised about the health implications of eating contaminated fish. In the present study, potentially toxic elements (PTE), such as Zn, Cu, Cr, Ni, Cd, Pb, As, Hg, and methylmercury (MeHg), were determined in ichthyofauna that are commonly consumed. PTE were determined in the fish muscle tissue. Fish were sampled at 12 locations from the source of the Sava River to its confluence with the Danube River during two sampling campaigns, namely; in 2014 under high water conditions and in 2015 under normal water conditions. Due to the different water regimes, different fish species were collected for chemical analysis. We observed that the concentrations of elements analysed in the fish muscle tissue were generally very low, except for those of Hg. Moreover, more than 90% of Hg present in the fish was in its most toxic form, namely MeHg. Especially in fish from the 2015 sampling campaign, Hg and MeHg concentrations increased with fish size, trophic level, and in the downstream direction. In addition, for Pb and As, and to some extent for Cd and Cr, spatial differences were detected in both years. The highest concentrations of PTE were detected in fish from sites with intensive industrial and agricultural activities. The consumption of fish in general does not pose a health risk for the PTE studied, except for Hg/MeHg at selected contaminated sites.

Potentially toxic elements in water, sediments and fish of the Evrotas River under variable water discharges

Among different stressors like drought, hydro-morphological alterations, and pollution from agricultural activities, nutrients, organic compounds and discharges from wastewater treatment plants (WWTPs), potentially toxic elements (PTE) may also contribute to the overall pollution of the Evrotas River, Greece. Nevertheless, information on pollution of elements in water and sediments in this river is scarcely documented. There is also no information available on the impact of elemental pollution from the aquatic environmental compartments on biota. To fill these gaps, in this study, water, sediment and fish samples were collected from four sampling sites along the Evrotas River under variable flow regimes (July 2015, higher discharge; June 2016, low discharge and September 2016, minimum discharge). Total and dissolved element concentrations in water samples, total and acetic acid extractable contents in sediments, and element concentrations in fish samples were determined by inductively coupled plasma mass spectrometry and significant relationships between samples were established using correlation analysis. The concentrations of PTE (Ni, Cr, Cd, As, Pb, Zn and Cu) in water were generally low, while elevated Ni and Cr contents were found in sediments (up to 150 and 300 mg/kg, respectively), with total Cr concentration in water and sediment being positively correlated. The ecological risk posed by the simultaneous presence of PTE in sediments evaluated by calculating the Probable Effect Concentration Coefficient (PEC-Q), demonstrated that PEC-Qs, which were above the critical value of 0.34, derived mostly from Cr and Ni inputs. Since their mobile sediment fraction was extremely low, Cr and Ni origin is most probably geogenic. The analysis of elements in the target fish species, the Evrotas chub, showed low to moderate PTE concentrations, with Pb being positively correlated with total Pb concentration in water. Moderate Zn concentrations found in fish samples from the Evrotas are possibly derived from pesticides and fertilizers.

Potentially toxic elements in freshwater (Alburnus spp.) and marine (Sardina pilchardus) sardines from the Western Balkan Peninsula: An assessment of human health risk and management

The concentrations of 14 potentially toxic elements in freshwater and marine sardines from the Western Balkan Peninsula were determined. In Prespa Lake, a natural lake, the concentrations of toxic Pb and Cd were above the maximum permissible concentrations in freshwater sardines. The As concentrations were elevated in sardines from Boka Kotorska Bay. The Target Hazard Quotient (THQ) and Hazard index (HI) were above their defined limits in Boka Kotorska Bay and Skadar Lake, indicating a health risk for Montenegrin consumers. The results of this study set apart Zavoj, Vlasina and Međuvršje artificial reservoirs as potential ecosystems for developing commercial fishing and for the safe use of freshwater sardines for human consumption. Constant monitoring of Ohrid, Prespa and Dojran natural lakes, as well as Boka Kotorska Bay, may be implemented in the interest of public health.

The Effects of the RCS’s Application in the Value Added Tax Collecting Process on the Perception of SME Taxpayer in Korea’s Trade Activity: Transparency and Fairness in Trade

Value Added Tax (VAT) is the largest source of global tax revenue. However, it faces issues of tax avoidance, such as the black-market and missing trader intra-community fraud. Many studies have postulated that the introduction of the Reverse Charge System (RCS) will contribute to the enhancement of transparency and fairness in trade for small and medium enterprises (SMEs) that supply goods or provide services. This study analyzes SME taxpayers’ perception of transparency and fairness in trade resulting from the introduction of the RCS into the South Korean VAT system. In B2B transactions that handle gold, copper, and steel scrap, large companies often abuse their bargaining power over smaller firms by not paying VAT with their purchase or reducing the prices to equal VAT, leading to low trade transparency. When it comes to gold, copper and steel scrap trading, the imbalance in bargaining power results in one of the parties being unable to reap maximum benefits because of unfairness. SMEs with relatively weak bargaining power suffer from unfair trading practices such as price cutting and the imposition of VAT by their counterparts. Since the introduction of the RCS, however, SME taxpayers appear to believe that trade fairness has improved. This study’s findings reveal that SMEs are more likely to perceive improvement in trade transparency and fairness since the implementation of the RCS, indicating that the RCS has exerted a positive influence on SMEs. This study provides important policy implications for countries that intend to implement the RCS by offering empirical evidence of its benefits.

Mobility and natural attenuation of metals and arsenic in acidic waters of the drainage system of Timok River from Bor copper mines (Serbia) to Danube River

Bor, Krivelj, and Bela Rivers belong to the watershed of Timok River, which is a tributary of transboundary Danube River. These rivers receive metal-rich acidic wastewater from metallurgical facilities and acid mine drainage (AMD) from mine wastes around Bor copper mines. The aim of this study was to determine the mobility and natural attenuation of metals and arsenic in rivers from Bor copper mines to Danube River during the year 2015. The results showed that metallurgical facilities had the largest impact on Bor River by discharging about 400 t of Cu per year through highly acidic wastewater (pH = 2.6). The highest measured concentrations of Cu in river water and sediments were 40 mg L^-1 and 1.6%, respectively. Dissolution of calcite from limestone bedrock and a high concentration of bicarbonate ions in natural river water (about 250 mg L^-1) enhanced the neutralization of acidic river water and subsequent chemical precipitation of metals and arsenic. Decreases in the concentrations of Al, Fe, Cu, As, and Pb in river water were mainly due to precipitation on the river bed. On the other hand, dilution played an important role in the decreases in concentrations of Mn, Ni, Zn, and Cd. Chemically precipitated materials and flotation tailings containing Fe-rich minerals (fayalite, magnetite, and pyrite) were transported toward Danube River during the periods of high discharge. This study showed that processes of natural attenuation in catchments with limestone bedrock play an important role in reducing concentrations of metals and arsenic in AMD-bearing river water.

Evaluation of genotoxic potential in the Velika Morava River Basin in vitro and in situ

The Velika Morava River is the greatest national Serbian river and the significant tributary of the Danube River. The major problems in the Velika Morava River Basin (VMRB) represent untreated industrial and municipal wastewaters. In this study, the level of genotoxic potential at the sites along the VMRB was evaluated by parallel in vitro and in situ approach. Within in vitro testing, genotoxicity of native water samples collected from the sites in VMRB was evaluated by SOS/umuC test on Salmonella typhimurium TA1535/pSK1002 and by the comet assay on HepG2 cells. DNA damage in situ was assessed in bleak (Alburnus alburnus) erythrocytes by the comet (alkaline and Fpg-modified comet) and micronucleus assays. Additionally, the concentration of heavy metals in fish tissue was measured and this data, compiled with the data of the physico-chemical parameters measured in water, was used as a measure of the pollution pressure at the sites. Results showed that applied in vitro tests with native water samples are less sensitive in comparison with in situ tests and should be taken with precaution when making predictions on the status of the ecosystem. Within applied battery of in situ assays differential sensitivity of assays was observed where alkaline comet assay showed the highest potential in differentiation of the sites based on genotoxic potential. Integrated biomarker response showed that usage of the battery of bioassays provides better insight in a genotoxic effects in animals, and consequently, that the holistic approach is more suitable for this type of study.

Heavy metal contamination in the muscle of Aegean chub (Squalius fellowesii) and potential risk assessment

Especially after the industrial revolution, the amount of contaminants released in aquatic ecosystems has considerably increased. For this reason, the necessity to carry on research on the existence of contaminants, specifically heavy metals, has emerged. In this study, heavy metal concentrations in muscle tissues of Aegean chub, which was an endemic species of south western part of Turkey, gathered from Tersakan River were examined. Heavy metal concentrations of the samples were analyzed with ICP-MS. Estimated daily intakes (EDI), target hazard quotient (THQ), and carcinogenic risk (CR) of elements were calculated. The heavy metals detected in muscle tissues were Zn > Cu > Cr > Mn > Pb > Cd, consecutively. According to the results of the applied health risk assessment (EDI, THQ and CR) for heavy metal exposure from fish consumption in children and adults, it was determined that there was no any significant threat to human health.

Heavy metal pollution in immobile and mobile components of lentic ecosystems-a review

With growing population and urbanization, there is an increasing exploitation of natural resources, and this often results to environmental pollution. In this review, the levels of heavy metal in lentic compartments (water, sediment, fishes, and aquatic plants) over the past two decades (1997-2017) have been summarized to evaluate the current pollution status of this ecosystem. In all the compartments, the heavy metals dominated are zinc followed by iron. The major reason could be area mineralogy and lithogenic sources. Enormous quantity of metals like iron in estuarine sediment is a very natural incident due to the permanently reducing condition of organic substances. Contamination of cadmium, lead, and chromium was closely associated with anthropogenic origin. In addition, surrounding land use and atmospheric deposition could have been responsible for substantial pollution. The accumulation of heavy metals in fishes and aquatic plants is the result of time-dependent deposition in lentic ecosystems. Moreover, various potential risk assessment methods for heavy metals were discussed. This review concludes that natural phenomena dominate the accumulation of essential heavy metals in lentic ecosystems compared to anthropogenic sources. Amongst other recent reviews on heavy metals from other parts of the world, the present review is executed in such a way that it explains the presence of heavy metals not only in water environment, but also in the whole of the lentic system comprising sediment, fishes, and aquatic plants.

Heavy metals and minerals contents in pikeperch (Sander lucioperca), carp (Cyprinus carpio) and flathead grey mullet (Mugil cephalus) from Sidi Salem Reservoir (Tunisia): health risk assessment related to fish consumption

The aim of this study was to investigate heavy metals and selected minerals contents in filets of pikeperch (Sander lucioperca), carp (Cyprinus carpio) and flathead grey mullet (Mugil cephalus), the major fish species produced in Sidi-Salem reservoir; the largest Tunisian freshwater ecosystem. Concentrations of Ca, Mg, Fe, Zn, Cd, Pb and Hg were determined by inductively coupled plasma-optical emission spectrometry, while concentrations of Na and P were determined by flame photometry and spectrophotometry, respectively. Results concerning heavy metals are considered quantitatively reliable for Hg and Cd but must be taken with precautions concerning Pb levels as the LOD (limit of detection) of the analytical process was higher than acceptable limit. They showed greater accumulations of both Hg and Cd in filets of pikeperch than in filets of carp and mullet, but none of the values exceeded the normative maximum levels (0.500 and 0.050 mg kg^-1 w.w., respectively). Considering provisional intakes, target hazard quotient and hazard index, estimated for a fish portion per week, consumption of any of the species did not appear to be potentially hazardous for the health as they were far below threshold values. A fish portion would provide substantial amounts (>15% of daily requirements) in essential mineral nutrients (P, Mg and Fe) and thus should be considered an interesting contribution to a healthy diet. It is strongly advocated to authorities including freshwater fish in the official national annual control survey of contaminants in fishery products, which in addition to guaranteeing security of consumers, would also allow diversifying valorisation opportunities and thus increase the economic value of this fish production.

Heavy metal accumulation in organs of Oreochromis niloticus (Linnaeus, 1758) from industrial effluent-polluted aquatic ecosystem in Lagos, Nigeria

The concentrations of four heavy metals (Zn, Fe, Cu, and Pb) in water, sediment, and tissues (gill, muscle, brain, and intestine) of Oreochromis niloticus from a segment of the Lagos Lagoon complex were monitored for 10 months (July 2012-April 2013) spanning wet and dry seasons. Three sampling stations were selected: Ologe Lagoon, the nearest to the point where effluent is discharged from Agbara Industrial Estate, the Owo River is upstream before the point of discharge of industrial effluent, and Etegbin is downstream. In most cases, the highest concentrations of heavy metal in fish tissues were recorded in samples obtained from Ologe Lagoon. The ranges of concentrations of heavy metals in the tissues of the fish were 4.06 ± 2.45-49.94 ± 13.11, 81.27 ± 28.52-2044.64 ± 554.77, 10.90 ± 7.69-41.10 ± 11.24, and 0.12 ± 0.07-1.81 ± 3.12 mg/kg for Zn, Fe, Cu, and Pb, respectively. There were significant negative correlations (lowest; r = -0.24, p < 0.01, n = 30; highest; r = -0.58, p < 0.01, n = 30) between fish tissue metal concentrations and size of fish from Ologe Lagoon. Also, significant positive correlations (lowest; r = 0.48, p < 0.05, n = 30; highest; r = 0.93, p < 0.01, n = 30) between concentrations of Cu in sediment and tissues of O. niloticus were observed. The concentrations of the metals in the tissues of O. niloticus have exceeded the limits recommended by WHO. The maximum safe daily consumption (MSDC) value of Fe in Ologe Lagoon was lower than the recommended average daily intake of fish for humans. This indicated that O. niloticus from Ologe Lagoon may not be safe for human consumption. Therefore, there is a need for regular monitoring of heavy metal in these water bodies and enforcement of existing laws on the treatment of effluent before they are discharged into aquatic ecosystems.