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

Extreme hydrological regimes of a small urban river: impact on trace element partitioning, enrichment and fluxes

The input of trace elements from a small urban river (Las River, Toulon, France) located on the northern Mediterranean coast was studied during both base flow and flood events. A 2-year monitoring period of water flow and suspended particulate matter (SPM) showed a typical Mediterranean hydrological regime: a strong increase in water flow and SPM during short flood periods. During the flood event, an up to 2-fold increase in dissolved trace element (DTM) concentrations and particulate trace element content in SPM (PTM) was observed compared to the baseline discharge. The enrichment factor of elements in the SPM ranges from low or moderate for Co, Ni and Cr (1.0-4.7) to extremely high for Cd (157). However, the enrichment factors decrease from base flow to flood, indicating a dilution effect with a large yield of weathering particles with higher particle size. The most significant total trace element loading occurred during flood, ranging from 78% for As and Ni to 91% for Pb, while PTM loading during flood ranged from 35% for As to 77% for Pb. The specific dissolved fluxes during the flood are significantly higher for Pb, Cu and Zn than in the surrounding rivers, indicating specificity in the catchment (lithology). This study shows the importance of monitoring the transport of pollutants through small urban rivers and their potential impact on the coastal region, especially when they enter small and closed bays, as a receiving pool.

A modelling framework to assess multiple metals impacts on marine food webs: Relevance for assessing the ecological implications of deep-sea mining based on a systematic review

Industrial deep-sea mining will release plumes containing metals that may disperse over long distances; however, there is no general understanding of metal effects on marine ecosystems. Thus, we conducted a systematic review in search of models of metal effects on aquatic biota with the future perspective to support Environmental Risk Assessment (ERA) of deep-sea mining. According to results, the use of models to study metal effects is strongly biased towards freshwater species (83% freshwater versus 14% marine); Cu, Hg, Al, Ni, Pb, Cd and Zn are the best-studied metals, and most studies target few species rather than entire food webs. We argue that these limitations restrain ERA on marine ecosystems. To overcome this gap of knowledge, we suggest future research directions and propose a modelling framework to predict the effects of metals on marine food webs, which in our view is relevant for ERA of deep-sea mining.

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.

Spatial distribution and ecological risk assessment of heavy metals in surface sediments from the northern Bohai Strait, China

The epicontinental seas to the east of China have become highly anthropogenically impacted due to rapid economic development in recent decades, resulting in various environmental problems, including heavy metal pollution. The Bohai Strait, as a key junction connecting the material-energy exchange between the Bohai and Yellow Seas, is extremely critical in regional pollution prevention and control. To ascertain the spatial distribution and contamination levels of heavy metals in the surface sediments of the northern Bohai Strait, a systematic investigation was conducted. Geochemical analysis revealed that the concentrations (in ppm) of heavy metal elements in surface sediments vary in the range of 4.19-77.6 for As, 0.04-0.21 for Cd, 5.1-65.7 for Pb, 0.30-39.40 for Cu, 7.77-46.50 for Ni, 1.50-86.60 for Cr, 11.70-91.80 for Zn, and 0.005-0.038 for Hg. Ecological statistics indicate that the northern Bohai Strait suffers from prominent heavy metal pollution primarily induced by As, Cd, and Pb, accompanied by relatively weak pollution of Cu and Ni. Sediments collected from the submarine depressions and the southeast region exhibit higher heavy metal concentrations, and as a consequence, more serious ecological risk. Correlation analysis indicated that the accumulations of Hg, Cr, and Zn were associated with the deposition of organic matter. Preliminary provenance discrimination suggested that the pollutants were mainly derived from the eastern parts of the North Yellow Sea, rather than the Bohai region.

Heavy metals in lake surface sediments in protected areas in Poland: concentration, pollution, ecological risk, sources and spatial distribution

This paper presents the state and spatial distribution of surface sediment contamination of 77 lakes in Poland by Cr, Ni, Cd, Pb, Zn, and Cu. The analyzed lakes were located within a network of nature protection areas in the territory of the European Union (EU). Spatial distribution of the heavy metals (HMs), factors favoring the delivery/accumulation of HMs in surface sediments, and pollution sources were analyzed. The results indicate the contamination of lake sediments by HMs, but the potentially toxic effects of HMs are only found in single lakes. The spatial distribution of Cr indicates predominant impacts of point sources, while for Pb, Ni, and Zn, the impact of non-point sources. The analysis showed the presence of areas with very high values of particular HMs (hot spots) in the western part of Poland, while a group of 5 lakes with very low values of Ni, Pb, and Zn (cold spots) was identified in the central part of Poland. Principal component analysis showed that presence of wetlands is a factor limiting HMs inflow to lakes. Also, lower HMs concentrations were found in lake surface sediments located in catchments with a higher proportion of national parks and nature reserves. Higher HMs concentrations were found in lakes with a high proportion of Special Protection Areas designated under the EU Birds Directive. The positive matrix factorization analysis identified four sources of HMs. High values of HMs concentrations indicate their delivery from industrial, urbanized, and agricultural areas. However, these impacts overlap, which disturbs the characteristic quantitative profiles assigned to these pollution sources.

Distribution and assessment of heavy metal in sediments of Malacca Strait

In this study, we explored the heavy metal elements in 42 surface sediments from the Malacca Strait in terms of distribution, controlling factors, environmental quality, and primary sources. An analysis of grain size revealed finer sediments near the coast of Malaysia, which gradually thickened toward offshore. In addition, heavy metal elements were abundantly distributed near the coastal area of Malaysia, with a gradual decrease toward the sea; their content increased within waters close to the Perak estuary. Source analysis of heavy metals showed that Cr, Hg, Zn, Cd, and Cu were mostly derived from natural weathering, and their distribution was significantly influenced by sediment grain size. As and Pb were affected by human activities. The environmental quality assessment results showed that Cu, Cr, Cd, and Zn in our study regions were pollution-free. Pb elements showed low-to-moderate pollution, and Hg showed a certain degree of ecological risk due to its high toxicity coefficient. The content of As elements in surface sediments increased significantly when compared to the background value, with several evaluation methods indicating a high-risk index. According to these findings, the area near the mouth of the Perak River is the most polluted, followed by the surrounding coastal areas.

Evaluation of transcriptional biomarkers using a high-resolution regression approach: Concentration-dependence of selected transcripts in copper-exposed freshwater mussels (Anodonta anatina)

We tested concentration-dependence of selected gene transcripts (cat, gst, hsp70, hsp90, mt and sod) for evaluation as biomarkers of chemical stress. Contrary to the common approach of factorial designs and few exposure concentrations, we used regression across a high-resolution concentration series. Specifically, freshwater mussels (Anodonta anatina) were acutely (96 h) exposed to Cu (13 nominal concentrations, measuring 0.13-1 600 µg/L), and transcripts were measured by RT-qPCR. In digestive glands, cat, hsp90 and mt decreased with water Cu (p < 0.05), but response magnitudes saturated at < 2-fold decreases. In gills, gst, hsp70, hsp90 and mt increased with water Cu (p < 0.05). While hsp70, hsp90 and mt exceeded 2-fold increases within the exposure range, high Cu concentrations were required (38-160 µg/L). Although gill responses were generally more robust compared to digestive glands, overall small response magnitudes and moderate sensitivity may set limit for potential application as general biomarkers of chemical stress.

Diversity and functions of microbes in surface sediments under heavy metal pollution of western Chaohu Lake

Heavy metal pollution is a global concern. Targeting at the surface sediments in western Chaohu Lake and using metagenome sequencing, we probed into the mechanism of how microbes adapted to heavy metal-polluted sediments under natural conditions. It was found the heavy metal pollution intensity of the three typical sampling places ranked as estuary of Nanfeihe River (NFH) > Zhongmiao Town (HZ) > Hongshizui (HSZ). Totally 129 phyla, 2631 genera and 12 989 species were detected in the sediment samples, and HSZ, HZ and NFH had 35, 51 and 67 exclusive genera, respectively. The bacterial biomass and virus quantity from NFH accounted for 22·84 and 70·69% of total quantities, respectively, and the microbial community compositions in NFH were also different from those in HSZ and HZ. Metagenomics sequencing and functional gene annotation showed NFH contained many functional genes related to nucleic acid transport and metabolism, ribosome structures and biological origin, replication recombining and repair and inorganic ion transport and metabolism. Kyoto Encyclopedia of Genes and Genomes analysis suggested the sediments from NFH were rich in enzymes correlated with heavy metal transport and reduction. Our findings offer some scientific basis for Chaohu Lake control and microbe resource utilization.

Analysis of Spatial Distribution of Sediment Pollutants Accumulated in the Vicinity of a Small Hydropower Plant

Hydropower plants affect the distribution and composition of sediments. The main aim of this study was to analyze the spatial distribution of sediment pollution in the vicinity of a small hydropower plant. The grain composition of the sediments, the content of heavy metals (Cu, Ni, Cr, Zn, Pb, and Cd) and select physicochemical properties (pH, electrolytic conductivity) were tested at 14 points upstream and downstream of the hydropower plant on the Ślęza River in Poland, as well as at reference point. The interactions between the tested parameters were also verified. The results of the conducted analysis show that hydropower plants significantly affect the composition and properties of sediments. Large amounts of sediment are deposited on damming weirs, accumulating heavy metals and other substances. The differences in the concentrations of elements were significant, and Cu, Ni, Cr, Zn and Pb were 8.74, 9.53, 3.63, 8.26 and 6.33 times higher, respectively, than the median value at points upstream of the hydropower plant than downstream. It was shown that the tested parameters of the sediments interact with each other and are correlated; heavy metals showed a synergistic effect, while other parameters configurations showed an antagonistic effect. The higher content of heavy metals upstream of the hydropower plant resulted from the presence of finer sediment—classified as silt—in this section. Downstream of the hydropower plant, there were mainly sands, which showed a lower ability to absorb substances. This work contributes to improving the rational management of the worldwide issue of sediments within dams located in river valleys. Moreover, it is in line with the 2030 Sustainable Development Goals adopted by the United Nations, particularly in the fields of clean water and sanitation, clean and available energy, and responsible consumption and production.

Distribution and assessment of heavy metal contents in surface sediments of the western Sunda Shelf

The heavy metal contents (Cr, Cu, Zn, Cd, Pb, Hg, and As) of 88 surface sediment samples from the western Sunda Shelf were analyzed to determine their spatial distribution patterns and contamination status. The results demonstrated that high enrichment regions of heavy metals were focused in the Kelantan, Pahang, and Ambat river estuaries, and deep water regions of the study area. These high enrichment regions were mainly controlled by riverine inputs and their hydrodynamic conditions. The enrichment factor (EF), geoaccumulation index (I_geo), and potential ecological risk index (PERI) were used to assess heavy metal accumulation. The results indicated that the study area was not significantly contaminated overall at the time of the study; however, Cd, As, and Hg were at levels corresponding to moderate contamination at many stations located in the Pahang River estuary, Kelantan River estuary, and north-eastern region of the study area, primarily because of anthropogenic activities.

Carbon isotope fractionation in karst aquatic mosses

Radiocarbon activity (a¹⁴C) and ¹³C composition (δ¹³C) were measured in hygrophyte and mesophyte (land) mosses collected in the natural habitat of the Plitvice Lakes and along the Zrmanja and Krupa Rivers (typical continental and Mediterranean climates, respectively), Croatia. a¹⁴C and δ¹³C values of mosses, of atmospheric CO₂ and dissolved inorganic carbon (DIC) were compared with contemporary data and with data from 30 years ago at the Plitvice Lakes when ¹⁴C activity of atmospheric CO₂ was ∼30% higher. A positive correlation between a¹⁴C_moss and δ¹³C_moss was observed for all data reflecting the change of carbon isotopic composition in DIC along the water flows and in atmospheric CO₂ regardless of the climatic regions and historic period. Fraction of the atmospheric carbon in moss (ωatm.C) and carbon fractionation factor from aquatic CO₂ (DIC) to moss tissue (εmoss/g-aq) were calculated for each individual moss. Three species of mosses had ω_atm.C ∼ 0 % implying that they turn to anabiosis during dry periods. The relation εmoss/g-aqvs.ωatm.C differentiates true aquatic and amphiphyte mosses. The first had a statistically significant negative correlation between εmoss/g-aq and ωatm.C. The amphiphyte mosses had lower εmoss/g-aq with higher water flow rates.

Trace metals in deep-sea sediments collected from Kuril Basin (Sea of Okhotsk) and Kuril-Kamchatka Trench area

Heavy metal concentrations in deep-sea sediments collected from Kuril Basin (Sea of Okhotsk) and Kuril-Kamchatka Trench area were analyzed. For the Kuril Basin, a geochemical natural background of these elements was identified based on a dated core. The results showed enrichment by heavy metals due to natural factors in the study area. All heavy metals showed a low ecological risk; thus, the potential ecological risk of the study area was also low.

Baseline radioecological data for the soil and selected bioindicator organisms in the temperate forest of Plitvice Lakes National Park, Croatia

The aim of this study was to provide baseline radioecological data for the temperate forest ecosystem in Plitvice Lakes National Park. Emphasis was placed on the determination of naturally occurring radionuclides since there is an acknowledged lack of data for these radionuclides in non-accident conditions in wildlife, even for bioindicator organisms. Activity concentrations of ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th, ⁴⁰K, ¹³⁴Cs, and ¹³⁷Cs were measured by gamma spectrometry in soil and bioindicators: earthworms, conifer needles, mosses, and lichens. From the measured activity concentrations, concentration ratios were calculated to quantify the transfer of these radionuclides from soil to bioindicators. Our results show that soil activity concentrations are biased toward results from other studies conducted within the Dinaric mountain region. However, in moss and lichen samples, we measured higher activity concentrations of ²²⁶Ra and lower activity concentrations of ⁴⁰K and ¹³⁷Cs in comparison to similar studies. Also, we estimated lower concentration ratios for all radionuclides from soil to these organisms, except for ²¹⁰Pb, in comparison to generic values. The transfer of ²³⁸U was generally low for all of the bioindicator organisms. For conifer needles, a correlation was found between activity concentrations of ²²⁶Ra and ¹³⁷Cs in soil and related concentration ratios. Correlation was also found between the activity concentration of ⁴⁰K in soil and transfer of ⁴⁰K and ¹³⁷Cs to mosses and lichens. A comparison with literature data highlighted the lack of ²²⁶Ra related concentration ratios for conifer trees and especially for earthworms. Therefore, the results of this study could supplement the sparse data currently available on radionuclide background data in similar ecosystems and related soil-to-wildlife transfer of radionuclides. Dose rate assessments, performed by the ERICA Tool, estimated that 96% of the overall exposure of wildlife in the Park area is due to the background dose rates, while 0.06 μGy h^-1 on average can be attributed as an incremental dose rate from ¹³⁴Cs and ¹³⁷Cs.

Distribution and assessment of heavy metals in surface sediments from the Bohai Sea of China

In this study, we analyzed heavy metals in 404 surface sediment samples from the Bohai Sea to measure contamination status and distribution. We found Zn levels to be the highest, whereas Hg concentrations were the lowest of measured heavy metals. We found that the samples containing the most heavy metals were those collected from Fuzhou Bay, Jinzhou Bay, central Bohai Sea mud area, and the Yellow River Delta. Further analyses suggest that these heavy metals in surface sediments in the Jinzhou Bay and Fuzhou Bay pose a serious ecological risk, with substantial Cd and Hg accumulation in the Jinzhou Bay and Yellow River Delta regions being indicative of intense human activities.

Transcriptional and biochemical biomarker responses in a freshwater mussel (Anodonta anatina) under environmentally relevant Cu exposure

Molecular biomarkers, like gene transcripts or enzyme activities, are potentially powerful tools for early warning assessment of pollution. However, a thorough understanding of response and baseline variation is required to distinguish actual effects from pollution. Here, we assess the freshwater mussel Anodonta anatina as a biomarker model species for freshwater ecosystems, by testing responses of six transcriptional (cat, gst, hsp70, hsp90, mt, and sod) and two biochemical (AChE and GST) biomarkers to environmentally relevant Cu water concentrations. Mussels (n = 20), collected from a stream free from point source pollution, were exposed in the laboratory, for 96 h, to Cu treatments (< 0.2 μg/L, 0.77 ± 0.87 μg/L, and 6.3 ± 5.4 μg/L). Gills and digestive glands were extracted and analyzed for transcriptional and biochemical responses. Biological and statistical effect sizes from Cu treatments were in general small (mean log₂ fold-change ≤ 0.80 and Cohen's f ≤ 0.69, respectively), and no significant treatment effects were observed. In contrast, four out of eight biomarkers (cat, gst, hsp70, and GST) showed a significant sex:tissue interaction, and additionally one (sod) showed significant overall effects from sex. Specifically, three markers in gills (cat, mt, GST) and one in digestive gland (AChE) displayed significant sex differences, independent of treatment. Results suggest that sex or tissue effects might obscure low-magnitude biomarker responses and potential early warnings. Thus, variation in biomarker baselines and response patterns needs to be further addressed for the future use of A. anatina as a biomarker model species.

Distribution of Organochlorine Pesticide and Polychlorinated Biphenyl Residues in Lake Sediment Cores from the Plitvice Lakes National Park (Croatia)

The occurrence and distribution of 11 organochlorine pesticides (OCPs) and their degradation products as well as of 17 polychlorinated biphenyl congeners (PCBs) were investigated for the first time in sediments of three (Lake Prošće, Lake Kozjak, Lake Kaluđerovac) out of 16 cascading karst lakes within the protected area of the Plitvice Lakes National Park in central Croatia. The 15-cm-long sediment cores were divided for analysis into three 5-cm-long segments. The abundance and levels of sediment-associated OCPs and PCBs were evaluated with respect to sampling location and sediment depth, presumed age of deposition, and organic carbon content. The burden of sediments with OCPs and PCBs decreased downstream with the highest mass fractions measured in the uppermost Lake Prošće (total OCPs 2.72-5.86 μg kg^-1 d.m., total PCBs 0.37-1.78 µg kg^-1 d.m.) and the lowest in Lake Kaluđerovac (total OCPs 0.30-0.58 μg kg^-1 d.m., total PCBs 0.07-0.12 µg kg^-1 d.m.). The predominant organochlorine pollutants were DDT-type compounds (total DDX, w = 0.30-5.72 µg kg^-1 d.m.) with p,p'-DDE and p,p'-DDD accounting for up to 100% and 50%, respectively, of the total DDX. The findings indicated an old input of p,p'-DDT that largely converted to its degradation products. The OCP and PCB mass fractions in the Plitvice lake sediments were at trace levels characteristic for preserved pristine natural environments with no or limited anthropogenic impact wherein long-range atmospheric transport is considered as their main source.

Spatial and interspecies differences in concentrations of eight trace elements in wild freshwater fishes at different trophic levels from middle and eastern China

There have been numerous studies on concentrations of trace elements in aquatic ecosystems, but few have been conducted at a large spatial scale. This study collected 410 samples of five wild freshwater fishes at different trophic levels from middle and eastern China. Concentrations of eight trace elements, chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb) and cadmium (Cd) and stable isotope ratios (δ¹³C and δ¹⁵N) were determined in dorsal muscle of fishes. Spatially, concentrations of trace elements were least in fishes from the Hai River Basin, while those in fishes from the Taihu Lake Basin were greatest. The carnivorous topmouth culter and omnivorous common carp and crucian carp accumulated greater amounts of trace elements than did the planktivorous silver carp and bighead carp. Trophic biomagnification was for Cu, Fe and Zn, but not for Cr, Ni, As, Pb and Cd. Concentrations of As in 15 muscle samples (3.7%) from Taihu Lake Basin exceeded the guidelines (1.0 mg/kg, wet mass) provided by FAO/WHO (2014), while the total target hazard quotient (TTHQ) values were <1.0, indicating no obvious non-carcinogenic risks to humans that consume those fishes. However, people who consume larger amounts of fish products, or people who are vulnerable, such as pregnant women, children and people with poor health, might be at greater risk. Also, exposure to trace metals through other routes cannot be ignored. Accumulations of trace elements in Chinese freshwater fishes were affected by both geographical conditions and human activities.

Concentration, spatiotemporal distribution, and sources of mercury in Mt. Yulong, a remote site in southeastern Tibetan Plateau

The unique geographic location of Mt. Yulong in the Tibetan Plateau (TP) makes it a favorable site for mercury (Hg) study. Various snow samples, such as surface snow, snow pit, and snowmelt water were collected from Mt. Yulong in the southeastern TP. The average concentration of Hg was found to be 37 ± 26 ng L^-1 (mean ± SD), comparable to Hg concentration from other parts of TP in the same year, though it was comparatively higher than those from previous years, suggesting a possible increase of Hg concentration over the TP. The concentration of Hg was higher in the lower elevation of the glaciers possibly due to the surface melting concentration of particulates. Higher concentration of Hg was observed in the fresh snow, suggesting the possibility of long-range transportation. The average concentration of Hg from the snow pit was 1.49 ± 0.78 ng L^-1, and the concentration of Hg in the vertical profile of the snow pit co-varied with calcium ion (Ca²⁺) supporting the fact that the portion of Hg is from the crustal origin. In addition, the principal component analysis (PCA) confirmed that the source of Hg is from the crustal origin; however, the presence of anthropogenic source in the Mt. Yulong was also observed. In surface water around Mt. Yulong, the concentration of Hg_T was found in the order of Lashihai Lake > Reservoirs > Rivers > Swamps > Luguhu Lake. In lake water, the concentration of Hg_T showed an increasing trend with depth. Overall, the increased concentration of Hg in recent years from the TP can be of concern and may have an adverse impact on the downstream ecosystem, wildlife, and human health.

Benthos-drift relationships as proxies for the detection of the most suitable bioindicator taxa in flowing waters - a pilot-study within a Mediterranean karst river

Mediterranean karst aquifers are sensitive systems vulnerable to contamination, exhibiting high rates of diversity and endemicity. In the present pilot-study, we aimed to detect the most suitable bioindicators of contaminant accumulation and mobilization within a Mediterranean karst river (Krka River, Croatia), whose lowermost sections belong to a designated protection area (national park). To meet our goal, we sampled water, drift and benthos (macroinvertebrates and periphytic microfauna) at the two Krka River sites, located upstream and downstream from town Knin and its urban influences. We compared: 1) environmental conditions (water physico-chemical parameters, trace- and macro-element concentrations); 2) abundance and diversity of periphyton and macroinvertebrate taxa constituting benthos; and 3) macroinvertebrate benthos-drift relationships between the two sites. Despite higher values of all measured physico-chemical parameters, and most trace- and macro-element concentrations at the urban-influenced site, the concentrations of contamination indicators (i.e., COD, nutrients, metals) at both sites were generally low. This is likely a result of specific "self-purification ability" of the Krka River, mediated by relatively high contaminant retention potential of the underlying tufa (i.e., calcareous) and/or macrophyte substrates. Between-site differences in water quality further affected the spatial variation of macrozoobenthos, drift, and periphytic microfauna. We suggest that increased COD and orthophosphate concentration, and macrophyte presence at the urban-influenced site, supported higher densities and diversity of benthic organisms dominated by eurivalent (i.e., contamination-tolerant) taxa. The most numerous macroinvertebrate taxa in benthos were amphipod Gammarus balcanicus and the representatives of the endemic Dinaric karst taxa - gastropods Emmericia patula and Radomaniola curta germari, and another amphipod Echinogammarus acarinatus. Although we expected to observe significantly increased drift at the urban-influenced site due to the degraded environmental conditions, it was not observed. The observed benthos-drift patterns suggest that freshwater amphipods (i.e., gammarids), which were found most numerous in drift, could be considered as the most suitable bioindicators of a contaminant (i.e., metal) accumulation and mobilization within karst aquifers comparable to Krka River.

Assessment of multiple anthropogenic contaminants and their potential genotoxicity in the aquatic environment of Plitvice Lakes National Park, Croatia

In this study, the influence of anthropogenic pollution on the aquatic environment of Plitvice Lakes National Park (PLNP) was investigated during 2011-2012 using a combination of chemical and cytogenetic analyses. Four groups of major contaminants [(volatile organic compounds: benzene, toluene, ethylbenzene, and xylenes (BTEX); persistent organochlorine pollutants: organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs); major and trace elements; anthropogenic radionuclides (⁹⁰Sr, ¹³⁴Cs, and ¹³⁷Cs)] were determined in three aquatic compartments (water, sediment, fish). Mass fractions of inorganic constituents in different compartments reflected the geological background of the area, indicating their origin from predominantly natural sources. Levels of volatile and persistent organic compounds in water and fish, respectively, were very low, at levels typical for remote pristine areas. Analysis of anthropogenic radionuclides in water and sediment revealed elevated activity concentrations of ¹³⁷Cs in water, and measurable ¹³⁴Cs in the upper sediment layers from April 2011, possibly as a consequence of the Fukushima nuclear accident in March 2011. The potential genotoxicity of river and lake water and lake sediment was assessed under laboratory conditions using the alkaline comet assay on human peripheral blood lymphocytes, and measured levels of primary DNA damage were within acceptable boundaries. The results showed that despite the protected status of the park, anthropogenic impact exists in both its terrestrial and aquatic components. Although contaminant levels were low, further monitoring is recommended to make sure that they will not rise and cause potentially hazardous anthropogenic impacts.

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.

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

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

Risk analysis on heavy metal contamination in sediments of rivers flowing into Nansi Lake

In order to understand the risk of heavy metals in sediments of the rivers flowing into Nansi Lake, 36 surface sediments were sampled from six rivers and seven heavy metals (Cr, Cu, Ni, Zn, As, Pb, and Cd) were determined. Potential ecological risk index (RI) of the six rivers showed significant differences: Xinxue River, Jiehe River, and Guangfu River were at medium potential risk, whereas the risk of Chengguo River was the lowest. Jiehe River, Xuesha River, and Jiangji River were meeting the medium potential risk at river mouths. Geo-accumulation index (I _geo) of the seven heavy metals revealed that the contamination of Cu and Cd was more serious than most other metals in the studied areas, whereas Cr in most sites of our study was not polluted. Moreover, correlation cluster analysis demonstrated that the contamination of Cu, Ni, and Zn in six rivers was mainly caused by local emissions, whereas that of As, Pb, and Cd might come from the external inputs in different forms. Consequently, the contamination of Cu and Cd and the potential risk in Xinxue River, Jiehe River, and Guangfu River as well as the local emissions should be given more attention to safeguard the water quality of Nansi Lake and the East Route Project of South to North Water Transfer.

An alternative approach to studying the effects of ZnO nanoparticles in cultured human lymphocytes: combining electrochemistry and genotoxicity tests

Nanoparticle use has increased radically raising concern about possible adverse effects in humans. Zinc oxide nanoparticles (ZnO NPs) are among the most common nanomaterials in consumer and medical products. Several studies indicate problems with their safe use. The aim of our study was to see at which levels ZnO NPs start to produce adverse cytogenetic effects in human lymphocytes as an early attempt toward establishing safety limits for ZnO NP exposure in humans. We assessed the genotoxic effects of low ZnO NP concentrations (1.0, 2.5, 5, and 7.5 μg mL-1) in lymphocyte cultures over 14 days of exposure. We also tested whether low and high-density lymphocytes differed in their ability to accumulate ZnO NPs in these experimental conditions. Primary DNA damage (measured with the alkaline comet assay) increased with nanoparticle concentration in unseparated and high density lymphocytes. The same happened with the fragmentation of TP53 (measured with the comet-FISH). Nanoparticle accumulation was significant only with the two highest concentrations, regardless of lymphocyte density. High-density lymphocytes had significantly more intracellular Zn2+ than light-density ones. Our results suggest that exposure to ZnO NPs in concentrations above 5 μg mL-1 increases cytogenetic damage and intracellular Zn2+ levels in lymphocytes.

Occurrence and risk assessment of trace metals and metalloids in sediments and benthic invertebrates from Dianshan Lake, China

The present study measured concentrations of Cr, Ni, Cu, Zn, As, Cd, Sb, and Pb in surface sediments and two benthic invertebrate species (Anodonta woodiana and Bellamya aeruginosa) collected from Dianshan Lake, located in the Yangtze River Delta. The Dianshan Lake acts as one of the most important drinking water sources to Shanghai, the biggest city in China. Concentrations of trace metals and metalloids ranged from 0.04 mg/kg for Cd to 288.0 mg/kg for Zn. Substantial bioaccumulation in invertebrates was observed for Zn and Cu based on the biota-sediment accumulation factor (BSAF) measurements. The results revealed that concentrations of metals and metalloids in sediments from Dianshan Lake were at the lower end of the range of levels found in other regions of China. The assessment of three significantly inter-related evaluation indices, including the geo-accumulation Index (I_geo), potential ecological risk factor (Erⁱ), and mean probable effect concentration quotients (Q_m-PEC), suggested that sediment-associated trace elements exhibited no considerable ecological risks in the studied watershed. However, the target hazard quotient and hazard index analysis suggested that selected elements (particularly As) accumulation in edible tissues of benthic invertebrates could pose potential health risks to local populations, especially fishermen. Given that wild aquatic organisms (e.g., fish and bivalves) constitute the diet of local populations as popular food/protein choices, further investigations are needed to better elucidate human health risks from metal and metalloid exposure via edible freshwater organisms.

Distribution, speciation, environmental risk, and source identification of heavy metals in surface sediments from the karst aquatic environment of the Lijiang River, Southwest China

The distribution and speciation of several heavy metals, i.e., As, Cd, Cr, Cu, Hg, Pb, and Zn, in surface sediments from the karst aquatic environment of the Lijiang River, Southwest China, were studied comparatively. The mean contents of Cd, Cu, Hg, Pb, and Zn were 1.72, 38.07, 0.18, 51.54, and 142.16 mg/kg, respectively, which were about 1.5-6 times higher than their corresponding regional sediment background values. Metal speciation obtained by the optimized BCR protocol highlighted the bioavailable threats of Cd, Cu, and Zn, which were highly associated with the exchangeable fraction (the labile phase). Hierarchical cluster analysis indicated that in sediments, As and Cr were mainly derived from natural and industrial sources, whereas fertilizer application might lead to the elevated level of Cd. Besides, Cu, Hg, Pb, and Zn were related to traffic activities. The effects-based sediment quality guidelines (SQGs) showed that Hg, Pb, and Zn could pose occasional adverse effects on sediment-dwelling organisms. However, based on the potential ecological risk assessment (PER) and risk assessment code (RAC), Cd was the most outstanding pollutant and posed the highest ecological hazard and bioavailable risk among the selected metals. Moreover, the metal partitioning between water and sediments was quantified through the calculation of the pseudo-partitioning coefficient (K P), and result implied that the sediments in this karst aquatic environment cannot be used as stable repositories for the metal pollutants.

The impact of multiple anthropogenic contaminants on the terrestrial environment of the Plitvice Lakes National Park, Croatia

The anthropogenic impact on the terrestrial environment of the Plitvice Lakes National Park (PLNP) was investigated through the analysis of three groups of major contaminants (persistent organochlorine pollutants including 15 organochlorine pesticides (OCPs) and 17 polychlorinated biphenyls (PCBs), trace elements/heavy metals (6 major and 23 trace constituents), and anthropogenic radionuclides ((90)Sr, (134)Cs, and (137)Cs)) in three terrestrial compartments (soil, air, and bioindicators of air contamination) during 2011-2013. The correlation coefficients of element mass fractions with soil properties indicated that total Fe and Al minerals, soil organic matter (OM), and organic carbon (OC) content affected the mass fractions of most trace elements in the topsoils. The annual and spatial distributions of heavy metals in total deposited matter (TDM) indicated that the metals came from natural sources and long-range transfer of particulate matter. The PCB and OCP levels found in soil and conifer needles corresponded to global environmental pollution levels by persistent organic pollutants and represented the lower end of the mass fraction ranges reported in the relevant literature. Analyses of anthropogenic radionuclides in bioindicators (conifer needles, lichens, and mosses) showed low but measurable activity concentrations of (134)Cs (for the first time after the Chernobyl accident), which indicated origin from the March 2011 Fukushima Nuclear Power Plant accident. Our overall results indicated that human activity inside or near the PLNP had no significant impact either on contaminant spread by air or on their content in topsoils.

Heavy Metal Pollution, Fractionation, and Potential Ecological Risks in Sediments from Lake Chaohu (Eastern China) and the Surrounding Rivers

Heavy metal (Cr, Ni, Cu, Zn, Cd, and Pb) pollution, fractionation, and ecological risks in the sediments of Lake Chaohu (Eastern China), its eleven inflowing rivers and its only outflowing river were studied. An improved BCR (proposed by the European Community Bureau of Reference) sequential extraction procedure was applied to fractionate heavy metals within sediments, a geoaccumulation index was used to assess the extent of heavy metal pollution, and a risk assessment code was applied to evaluate potential ecological risks. Heavy metals in the Shuangqiao and Nanfei Rivers were generally higher than the other studied sites. Of the three Lake Chaohu sites, the highest concentrations were identified in western Chaohu. Heavy metal pollution and ecological risks in the lake’s only outflowing river were similar to those in the eastern region of the lake, to which the river is connected. Heavy metal concentrations occurred in the following order: Cd > Zn > Cu > Pb ≈ Ni ≈ Cr. Cr, Ni, and Cu made up the largest proportion of the residual fraction, while Cd was the most prominent metal in the exchangeable and carbonate-included fraction. Cd posed the greatest potential ecological risk; the heavy metals generally posed risks in the following order: Cd > Zn > Cu > Ni > Pb > Cr.

Historical trends (1998-2012) of nickel (Ni), copper (Cu) and chromium (Cr) concentrations in marine sediments at four locations in the Northern Adriatic Sea

Historical trends (1998-2012) nickel (Ni), copper (Cu) and chromium (Cr) concentrations in marine sediments were assessed at four locations in the Northern Adriatic Sea (Croatia) in the proximity of an oil refinery. Ecological risks were characterized by benchmarking the dataset against Sediment Quality Guidelines (SQG). A significant number of samples had Ni values above ERL with no exceedance of the ERL values for Cu and Cr. Weak positive historical trends were found for only for Cu. At all sites there were statistically significant correlations between Ni and Cr indicating a common origin of these heavy metals in the investigated marine sediments. There were statistically significant differences between the sites under the direct influence of the oil refinery compared to the control site indicating the possibility that the oil refinery is contributing to the concentration of these heavy metals in the marine sediments.

Distribution and enrichment of mercury in Tibetan lake waters and their relations with the natural environment

Mercury (Hg) in aquatic ecosystems is of great concern due to its toxicity, bioaccumulation, and magnification in the food web. The Tibetan Plateau (TP) is endowed with the highest and largest lakes on earth, whereas Hg distribution and behavior in lake waters are least known. In this study, surface water samples from 38 lakes over the TP were collected and determined for the total Hg (THg) concentrations. Results revealed a wide range of THg concentrations from <1 ng to 40.3 ng L(-1). THg in lake waters exhibited an increasing trend along the southeast to northwest transect over the TP. Strong positive correlations were observed between THg concentrations and salinity and salinity-related environmental variables, especially for total dissolved solids (TDS) and some of the major ions such as Na(+), K(+), and Cl(-), suggesting the enrichment of Hg in saline lakes. The large-scale geographical pattern of climatic and environmental factors shows a decreasing precipitation and an increasing evaporation northwards and westwards and thereby induces gradient-enhanced enrichment of soluble substances in lake waters, which are likely to complex more Hg in northwestern TP. Our study provides the first comprehensive baseline data set of Hg in Tibetan lake waters and highlights the concurrent high Hg and salinity, representing valuable references and fundamental rules in further understanding the behavior and fate of Hg in lakes over the TP and perhaps high-altitude regions beyond.

Bioconcentration and bioaccumulation of metal in freshwater Neotropical fish Geophagus brasiliensis

From the concentration in water and sediments, bioconcentration and bioaccumulation of copper (Cu), manganese (Mn), zinc (Zn), iron (Fe), cobalt (Co), cadmium (Cd), chrome (Cr), silver (Ag), lead (Pb), nickel (Ni), aluminum (Al), and arsenic (As) were determined in the gills, liver, and muscles of Geophagus brasiliensis in the Alagados Reservoir, Ponta Grossa, Paraná, Brazil. Metals were quantified through AAS, and a study was carried out on the existing relations between metal and body weight, size, and genre of this species. The level of metal in the water of the reservoir was lower than the maximum set forth in the legislation, except for that of Cd and Fe. In sediments, Cu, Cd, Cr, and Ni presented concentrations above the threshold effect level (TEL). Pb and Cr were above the limits for the G. brasiliensis. The tendency of metals present in the muscles of G. brasiliensis was Al > Cu > Zn > Fe > Co > Mn > Cr > Ag > Ni > Pb > Cd > As. In the gills, it was Al > Fe > Zn > Mn > Co > Ag > Cr > Ni > Cu > As > Pb > Cd, and the liver presented Al > Cu > Zn > Co > Fe > Mn > Pb > Ag > Ni > Cr > As > Cd. The bioconcentration and bioaccumulation of metal in the tissues follow the global tendency liver > gills > muscle. The statistical analysis did not point to significant differences in the metal concentration and body weight, size, and gender of the species in the three tissues under analysis.

Evidencing the natural and anthropogenic processes controlling trace metals dynamic in a highly stratified estuary: The Krka River estuary (Adriatic, Croatia)

Distributions of trace metals (TM), organic carbon, SPM and physico-chemical parameters were studied in the highly stratified Krka River estuary in winter/summer periods. The non-conservative behaviour of Zn, Cd, Pb and Cu in the brackish layer (plume), easily spotted due to very low inputs by the river, was mainly caused by their inputs from the pleasure boats, nautical marinas and harbour (e.g. release from antifouling paints). Contrarily, Ni and Co followed near-conservative behaviour. The extremely low SPM discharged by the river, resulted in a predominant dissolved fraction (>80%) of all TM, except Pb. Vertical scavenging, coupled with the long residence time, caused accumulation and progressive upstream increase of TM and SPM in the bottom seawater. Decrease of distribution coefficient (KD) in the brackish layer for winter period was ascribed to the change of SPM nature (terrestrial vs. biogenic), whereas a variable and increased biogenic component of SPM caused scattered KDs in summer.

Consideration of the bioavailability of metal/metalloid species in freshwaters: experiences regarding the implementation of biotic ligand model-based approaches in risk assessment frameworks

After the scientific development of biotic ligand models (BLMs) in recent decades, these models are now considered suitable for implementation in regulatory risk assessment of metals in freshwater bodies. The BLM approach has been described in many peer-reviewed publications, and the original complex BLMs have been applied in prospective risk assessment reports for metals and metal compounds. BLMs are now also recommended as suitable concepts for the site-specific evaluation of monitoring data in the context of the European Water Framework Directive. However, the use is hampered by the data requirements for the original BLMs (about 10 water parameters). Recently, several user-friendly BLM-based bioavailability software tools for assessing the aquatic toxicity of relevant metals (mainly copper, nickel, and zinc) became available. These tools only need a basic set of commonly determined water parameters as input (i.e., pH, hardness, dissolved organic matter, and dissolved metal concentration). Such tools seem appropriate to foster the implementation of routine site-specific water quality assessments. This work aims to review the existing bioavailability-based regulatory approaches and the application of available BLM-based bioavailability tools for this purpose. Advantages and possible drawbacks of these tools (e.g., feasibility, boundaries of validity) are discussed, and recommendations for further implementation are given.

Assessing element distribution and speciation in a stream at abandoned Pb-Zn mining site by combining classical, in-situ DGT and modelling approaches

The distribution and speciation of elements along a stream subjected to neutralised acid mine drainage (NAMD) effluent waters (Mátra Mountain, Hungary; Toka stream) were studied by a multi-methodological approach: dissolved and particulate fractions of elements were determined by HR-ICPMS, whereas speciation was carried out by DGT, supported by speciation modelling performed by Visual MINTEQ. Before the NAMD discharge, the Toka is considered as a pristine stream, with averages of dissolved concentrations of elements lower than world averages. A considerable increase of element concentrations caused by effluent water inflow is followed by a sharp or gradual concentration decrease. A large difference between total and dissolved concentrations was found for Fe, Al, Pb, Cu, Zn and As in effluent water and at the first downstream site, with high correlation factors between elements in particulate fraction, indicating their common behaviour, governed by the formation of ferri(hydr)oxides (co)precipitates. In-situ speciation by the DGT technique revealed that Zn, Cd, Ni, Co, Mn and U were predominantly present as a labile, potentially bioavailable fraction (>90%). The formation of strong complexes with dissolved organic matter (DOM) resulted in a relatively low DGT-labile concentration of Cu (42%), while low DGT-labile concentrations of Fe (5%) and Pb (12%) were presumably caused by their existence in colloidal (particulate) fraction which is not accessible to DGT. Except for Fe and Pb, a very good agreement between DGT-labile concentrations and those predicted by the applied speciation model was obtained, with an average correlation factor of 0.96. This study showed that the in-situ DGT technique in combination with model-predicted speciation and classical analysis of samples could provide a reasonable set of data for the assessment of the water quality status (WQS), as well as for the more general study of overall behaviour of the elements in natural waters subjected to high element loads.

Heavy metal contamination in the surface sediments of representative limnetic ecosystems in eastern China

A comprehensive analysis of heavy metal pollution was conducted in the representative limnetic ecosystems of eastern China, which are subject to rapid economic development and population growth. The results demonstrated that the average contents with standard deviations of Cd, Cr, Cu, Ni, Pb and Zn in the surface sediments were 0.925 ± 0.936, 142 ± 46.8, 54.7 ± 29.1, 60.5 ± 21.6, 61.9 ± 36.0 and 192 ± 120 mg/kg dry wt., respectively, and that higher values were mainly observed in the southern portion of the study area, especially in the basins of Southeast Coastal Rivers (SCRB) and the Zhu River (ZRB). The six heavy metals in the surface sediments all had anthropogenic origins. In addition, the limnetic ecosystems, especially in the southern portion of the study area were found to be polluted by heavy metals, especially Cd. Overall, two hotspots of heavy metal pollution in the limnetic ecosystems of eastern China were found, one that consisted of the heavy pollution regions, SCRB and ZRB, and another composed of Cd pollution. These results indicate that heavy metal contamination, especially Cd, should be taken into account during development of management strategies to protect the aquatic environment in the limnetic ecosystems of eastern China, especially in the two aforementioned basins.