Trophic transfer of metals in a seagrass food web: Bioaccumulation of essential and non-essential metals

Trace metal distribution in seagrass-vegetated sediments of an urbanized estuary in Queensland, Australia

Seagrasses increase sediment complexity by trapping particulates and influencing biogeochemical cycles via root oxygen loss and organic matter exudation. However, their impact on trace metal sequestration is poorly studied. We found significantly higher trace metal concentrations in seagrass sediments compared to adjacent bare sediments, correlating with total organic carbon, iron, and fine sediments. Sequential extractions showed that most trace metals were dominated by recalcitrant fractions (oxidizable and residual fractions), representing phases such as organic matter, iron sulfides, and crystalline iron oxides. Depth-dependent trends in trace metal partitioning were evident. For example, arsenic in the oxidizable fraction only weakly correlated with Fe in surface sediments (rsp = 0.55) but correlated strongly in deeper sediments (rsp = 0.87), consistent with iron sulfides being a dominant host-phase. Overall, these results suggest that the unique geochemical conditions facilitated by seagrasses play an important role in sequestering trace metals in urban estuarine sediments.

Metal concentrations in fish, crabs, and bivalve molluscs from marine waters adjacent to a multi-metals smelter and refinery

Metal concentrations were determined in tissues of finfish, crabs, and bivalve molluscs collected from marine waters near Port Pirie, South Australia, the site of a long-standing multi-metals smelter and refinery. A general trend of tissue metal concentrations in order of highest to lowest was observed in bivalves > crabs > finfish. A lead concentration of 158 ± 6.6 mg/kg (wet wt.) was observed in blue mussels (Mytilus galloprovincialis) sampled close to the smelter. Lead concentrations correlated positively with proximity to the smelter in all biota analysed. Similar relationships were observed for cadmium, copper, zinc and selenium in all biota except razorfish (Pinna bicolor; Bivalvia: Pinnidae), which showed no correlation with proximity to the smelter for these metals. Inorganic arsenic concentrations were below the limit of reporting in the majority of the analysed samples, however inorganic arsenic concentrations in blue swimmer crabs (Portunus armatus) and blue mussels correlated with proximity to the smelter. Mercury concentrations in the biota analysed were generally low and showed variable relationships with proximity to the smelter, with no significant correlation observed in finfish and razorfish, a significant positive correlation in blue mussels, and a significant negative correlation in blue swimmer crabs. This is the first major study of metal concentrations in recreationally-targeted marine species near Port Pirie species for more than two decades. Comparison with data from previous studies conducted shows little change in tissue metal concentrations in marine biota near Port Pirie over the past 40 years.

Trace metal pollution gradients in a tropical seagrass ecosystem

Trace metals are one of the most serious pollutants in tropical seagrass meadows given their persistence and toxicity. Whereas quantity is frequently measured, there is no information on the spatial extent of metal pollution in these systems. Here, we use an island in Indonesia (Barang Lompo) as a model system to study the impact radius of two major and eight trace metals in sediment and seagrass leaves. We provide evidence for exponential decay in both the metal pollution index and concentrations of most metals with increasing distance from the island (k = -0.01 to -0.08 m-1). Consequently, there is an impact radius of approximately 100 m around the island. The comparative analysis of both seagrass species further revealed interspecific differences in metal loads. This study highlights the importance of assessing the spatial extent of metal pollution in addition to its quantity.

Trophic Transfer of Cd, Cu, Pb, Zn, P and Se in Dutch Storage Water Reservoirs

Heavy metals are naturally omnipresent in aquatic systems. Excess amounts of heavy metals can accumulate in organisms of pollution impacted systems and transfer across a food web. Analysing the food web structure and metal contents of the organisms can help unravel the pathways of biomagnification or biodilution and gain insight in trophic linkages. We measured heavy metals and other elements in mussel bank detritus and organisms of the Biesbosch reservoirs (the Netherlands) and linked those to stable isotopic signatures. The heavy metal contents (cadmium, copper, lead, and zinc) were often lowest in benthivorous, omnivorous and piscivorous species (mainly fish); whereas, phosphorus contents were lower in the autotrophs. Mussel bank detritus contained the highest amounts of heavy metals. The heavy metals were negatively correlated with δ15N values. For selenium no clear trend was observed. Furthermore, there was a negative correlation between fish length and some heavy metals. Based on all 20 analysed elemental contents, similarities between species became apparent, related to niche or habitat. This study confirms that elemental contents of species can differ between feeding guilds and/or species, which can be attributed to metabolic and physiological processes. The organisms in higher trophic levels have adaptations preventing metal accumulation, resulting in lower contents. Within the fish species biodilution occurs, as most metal contents were lowest in bigger fish. Overall, the metals did not seem to biomagnify, but biodilute in the food web. Metal analyses combined with isotopic signatures could thus provide insights in metal transfer and possible trophic linkages within a system.

Trophic transfer of heavy metals through aquatic food web in the largest mangrove reserve of China

Understanding the mechanism of trophic transfer of heavy metal through the aquatic food web is critical to ecological exposure risk assessments in mangrove ecosystems. Zhanjiang Mangrove National Nature Reserve (ZMNNR) is the largest and biologically richest mangrove reserve in China, but has been exposed to heavy metal pollutants caused by the progressive industrialization and urbanization. We collected a variety of aquatic consumers, and primary producers, as well as sediments from the ZMNNR and analyzed them for heavy metal (Cd, Cr, Cu, Ni, Pb and Zn) concentrations, and for both δ13C and δ15N values to establish the trophic levels. The trophic magnification factors (TMF) of Cd, Cu and Zn are 0.19 (p < 0.01), 0.07 (p < 0.01) and 0.33 (p < 0.05), respectively, indicating significant biodilution in a simplified food web composed of bivalves, crustaceans and fish. There are also potential tendencies of biodilution for Cr, Ni and Pb. Comparison of heavy metals in representative fish and shrimp in the ZMNNR with those in worldwide mangroves indicate a low risk level for aquatic consumers in our ecosystem. Quantitative source tracking is conducted based on principal component analysis and cluster analysis, which indicate that Cr, Ni and Pb are mainly originated from natural geological processes, Cu and Zn from shrimp farming and agriculture activities, and Cd from the deposition of aerosol released by regional metal smelting industry.

Evaluation of metal exposure through the composition of essential and toxic micro-minerals in freshwater turtles (Phrynops geoffroanus) from a Brazilian river

This study aimed to evaluate metal exposure through the concentration of essential and toxic micro-minerals in biological samples of Phrynops geoffroanus from an anthropized river. The work was carried out in four areas with different flow characteristics and uses of the river, where individuals of both sexes were captured during the dry and rainy seasons. The elements Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn were quantified in samples of serum (168), muscle (62), liver (61), and kidney (61) by inductively coupled plasma optical emission spectrometry. The concentration of the elements varied according to the sample type, being higher in the liver and the kidney. In the serum, many elements were below the limit of quantification, but it was possible to determine Al, Cu, Fe, Mn, Pb, and Zn. The liver showed high levels of Cu, Fe, Pb, and Zn, and muscle for Fe, Ni, Pb, and Zn, with most of the elements accumulated in the kidney (Al, Cd, Co, Cr, Mn, Mo, and Ni) relative to other tissues. There was no significant difference between the sexes in the accumulation of elements. Between seasons, Cu was higher in serum and Mn in muscle and liver in the dry period, while in the kidney, almost all the elements were higher in the rainy period. The concentrations of the elements in the samples indicated a high degree of environmental contamination, representing risk in the use of the river and consumption of food from local fisheries.

Temporal distribution patterns of metals in water, sediment, and components of the trophic structure in a tropical coastal lagoon of the Gulf of Mexico

Trophic transfer and bioaccumulation of trace metals have a profound impact on the structure and function of coastal areas; however, the metal accumulation patterns in detritus-based food webs and the influence of climatic variability have not been thoroughly investigated. The Tampamachoco Lagoon (Gulf of Mexico) is a coastal system impacted by emissions from a thermoelectric plant. We evaluated the spatial-temporal distribution patterns of Al, Cd, Hg, Cr, Cu, and Pb in water, sediments, and in organisms categorized by trophic levels (TLs), trophic guilds, and habitat preferences. The sediments had the highest concentrations of metals with no significant differences between seasons. The indices of geo-accumulation and potential ecological risk classified sediments as "moderately contaminated", evidencing a threat to human health through consumption of detritivores and filter-feeders. The lowest TLs (filter-feeders and detritivorous) reached the maximum Metal Pollution Index in the rainy season. According to discriminant analyses of metals and species, omnivorous and zoobentivorous organisms were associated with Hg during the rainy and dry seasons; while Al, Cd, and Cu were related to low TLs, and seston was associated with Pb. Food web magnification factor analysis showed that: (a) Pb, Cu, and Cr were biodiluted as trophic levels increased; (b) Cd and Hg showed temporal biomagnification trends; (c) Al, Pb, Cu, and Cd showed significant biodilution from the lowest TL to intermediate TLs; and (d) Hg was transferred from the lowest to intermediate TLs with clear biomagnification effects.

The potential of saltmarsh halophytes for phytoremediation of metals and persistent organic pollutants: An Australian perspective

Persistent organic and inorganic pollutants are among the most concerning pollutants in Australian estuaries due to their persistent, ubiquitous, and potentially toxic nature. Traditional methods of soil remediation often fall short of practical implementation due to high monetary investment, environmental disturbance, and potential for re-contamination. Phytoremediation is gaining traction as an alternative, or synergistic mechanism of contaminated soil remediation. Phytoremediation utilises plants and associated rhizospheric microorganisms to stabilise, degrade, transform, or remove xenobiotics from contaminated mediums. Due to their apparent cross-tolerance to salt, metals, and organic contaminants, halophytes have shown promise as phytoremediation species. This review examines the potential of 93 species of Australian saltmarsh halophytes for xenobiotic phytoremediation. Considerations for the practical application of phytoremediation in Australia are discussed, including mechanisms of enhancement, and methods of harvesting and disposal. Knowledge gaps for the implementation of phytoremediation in Australian saline environments are identified, and areas for future research are suggested.

Insights into bioaccumulation and bioconcentration of potentially toxic elements in marine sponges from the Northwestern Mediterranean coast of Morocco

The present research aimed to investigate the concentrations and patterns of six potentially toxic elements (PTEs) in three common sponge species collected along the Moroccan Mediterranean coast, as well as their levels in ambient seawater and sediments. Distinct inter-species variability in PTEs bioaccumulation was observed among the three species, suggesting that sponges have distinct selectivity for assimilating PTEs from the surrounding environment. C. crambe had a higher enrichment capacity for Cu, As, Cr and Ni, while P. ficiformis and C. reniformis exhibited the highest concentration of Cd and Pb, respectively. Interestingly, a similar spatial distribution patterns of PTEs was observed in the three media, with high values occurring in Tangier and Al-Hoceima locations. Overall, our results confirm that sponges reliably reflect the bioavailability of PTEs in their immediate environment, especially C. crambe, whose PTE tissue contents were highly and positively correlated with the contents of all PTEs in the sediments.

Trace metal contents in the mussel Mytilus galloprovincialis from Atlantic coastal areas in northwestern Morocco: Levels of contamination and assessment of potential risks to human health

The bioaccumulation of trace metals Cd, Cr, Cu and Zn in soft tissues of the mussel Mytilus galloprovincialis was studied seasonally along the Atlantic coast of northwestern Morocco. Average concentrations (μg g^-1 dry weight) decreased in the following order: Zn (141.61 ± 78.06) > Cr (22.57 ± 15.47) > Cu (18.95 ± 20.01) > Cd (16.33 ± 19.01), with higher amounts during wet seasons. The "Metal Pollution Index" and "Individual Multimetal Bioaccumulation Index" suggested a higher mussel contamination in industrialized areas. Moreover, Cd and Cr concentrations were above the permissible guidelines' limits. The related risks to human health associated with mussel consumption were also assessed. The "Target Hazard Quotient" for Cd and Cr revealed a threat to children when mussels originated from polluted stations, while the "Hazard Index" indicated a hazard to them in all stations. Regarding the "Maximum Safe Consumption", children should not consume mussels, even in low quantities. This study represents the first datum in Morocco to assess such a risk to human health.

Stable isotopes analysis and heavy metal contamination in the rocky shore intertidal food web on the east coast of South Africa

Using a short food web, i.e. from prey (macro-algae) to predator (limpet), this study investigated the concentrations and biomagnification of heavy metals from macro-algae (Ralfsia verrucosa, Ulva lactuca and Gelidium pristoides) to limpet (Scutellastra cochlear, S. longicosta, S. granularis and Cellana capensis) species. Samples were collected from four sites (Mbhashe; Mthatha; Hluleka; Silaka Mouth) in four seasons (winter 2019; spring 2019; summer 2020; spring 2020). In the laboratory samples were digested with the normal protocols, subsequently analysed for heavy metals using inductively coupled plasma optical emission spectrometry (ICP-OES), while δ¹⁵N and δ¹³C isotopes were analysed with Isotope Ratio Mass Spectrometer (IRMS). There were significant differences of heavy metals concentration between species of macro-algae and limpet, and metal concentration was species-specific. Spatio-temporal differences of (δ¹³C) isotope was evident, indicating a wide source of energy. Using (δ¹⁵N) as a proxy for biomagnification (BMF) of metals, As did not show any sign of biomagnification (BMF<1) among all seasons and sites. Though mercury and Ni had BMF >1, negative regression slope showed biodilution of these metals to the next trophic level. The toxic Cd, Pb, and essential metals Zn and Cu indicated possible biomagnification (BMF >1) between sites and seasons respectively. This study showed that the selected limpet species are notable accumulators of heavy metals and these contaminants have the potential to biomagnify in the next trophic level suggesting that they are possibly unfit for human consumption in these study sites.

Current understanding and research needs for ecological risk assessments of naturally occurring radioactive materials (NORM) in subsea oil and gas pipelines

Thousands of offshore oil and gas facilities are coming to the end of their life in jurisdictions worldwide and will require decommissioning. In-situ decommissioning, where the subsea components of that infrastructure are left in the marine environment following the end of its productive life, has been proposed as an option that delivers net benefits, including from: ecological benefits from the establishment of artificial reefs, economic benefits from associated fisheries, reduced costs and improved human safety outcomes for operators. However, potential negative impacts, such as the ecological risk of residual contaminants, are not well understood. Naturally occurring radioactive materials (NORM) are a class of contaminants found in some oil and gas infrastructure (e.g. pipelines) and includes radionuclides of uranium, thorium, radium, radon, lead, and polonium. NORM are ubiquitous in oil and gas reservoirs around the world and may form contamination products including scales and sludges in subsea infrastructure due to their chemistries and the physical processes of oil and gas extraction. The risk that NORM from these sources pose to marine ecosystems is not yet understood meaning that decisions made about decommissioning may not deliver the best outcomes for environments. In this review, we consider the life of NORM-contamination products in oil and gas systems, their expected exposure pathways in the marine environment, and possible ecological impacts following release. These are accompanied by the key research priorities that need to better describe risk associated with decommissioning options.

Benthic-pelagic mixing of trace elements in estuarine food webs

Trace element accumulation pathways are important in many ecological and toxicological studies on aquatic organisms, yet these pathways are often poorly understood. To study the influence of diet and environment on the trace element composition of species within estuarine food webs, we performed a community level assessment of 28 trace elements (including major and minor elements) in common fish and prawn taxa across four estuaries, and in fish, prawn, and other invertebrate taxa within a single estuary. Despite sediment substrates from the four estuaries having distinctly different geochemical compositions, food web samples showed no separation by estuary, but clear separation by taxa. Grouping of taxa by trace elements was related to feeding ecology, with pelagic taxa separated from benthic taxa, and mixed feeding by generalist taxa. Arsenic and selenium were more concentrated in benthic fish, while aluminium, barium, copper, iron, manganese, vanadium, and zinc were more concentrated in pelagic fish. Trophic level did not appear to influence trace element composition. Previous laboratory studies have shown that food sources influence trace element concentrations in marine taxa and this study confirms that this also occurs in natural food webs. These results improve our understanding of the dominant importance of diet and physiology in controlling the trace element composition of species within estuarine food webs.

The concentration and biomagnification of trace metals and metalloids across four trophic levels in a marine food web

To be able to assess progress towards "Good Environmental Status" adopted across European Member States, and by the United Kingdom through its 3-stage Marine Strategy, contaminant concentrations and their biological effects need to be assessed in environmental samples by comparison to assessment criteria. This study examines the variability of concentrations (inter- and intra- species variation) of three priority heavy metals (Hg, Cd and Pb) and six additional trace metals and metalloids (As, Ni, Se, Zn, Cu and Cr) in twenty-three species across four trophic levels from different locations around Scotland. Trophic magnification factors (TMFs) were calculated using two methods for metals/metalloids possessing a significant trophic relationship (Hg, Cd, Cu, Ni and Zn) to refine and improve the application of TMFs to assess and predict biomagnification risk of metals/metalloids to biota in the environment. It was concluded that a reasonable balance in sample numbers of lower- versus higher-trophic level organisms is highly recommended when calculating TMFs and appropriate species selection is vital to ensure TMFs accurately represent the selected ecosystem.

Can Sediments Contaminated by Mining be a Source of Mercury in the Coastal Environment Due to Dredging? Evidence from Thermo-Desorption and Chemical Speciation

The sediments in the Gulf of Trieste (northern Adriatic Sea, Italy) are contaminated by mercury (Hg) due to historic mining which took place in Idrija (Slovenia). Despite many studies having been done regarding Hg, no information is available on the potential impact of dredging required along the main channel approaching the Port of Monfalcone. Sixteen surface sediment samples were collected along the channel to determine both total Hg concentration and chemical species using the thermo-desorption (TD) technique. Six samples were also chosen to apply a selective sequential extraction (SSE). The TD technique showed the maximum Hg release approximately at 260 and 335°C, corresponding to metacinnabar (β-HgS) and cinnabar (α-HgS), respectively. The SSE demonstrated that Hg was mainly associated with poorly soluble or insoluble compounds (98.7%). A resuspension event over a limited period of time can be considered of negligible impact to the water column due to the scarce Hg mobility from sediments.

Trophic transfer of heavy metals through aquatic food web in a seagrass ecosystem of Swan Lagoon, China

The Swan Lagoon is a national nature reserve and an important spawning ground in China. In this study, we evaluated the concentration of heavy metals (Cd, Cr, Cu, Pb, and Zn) in different aquatic organisms (aquatic plants, crustaceans, mollusks, and fish), in order to examine their trophic transfer in food web. The results showed that the concentrations of Cd, Cu, Pb, and Zn were considerably higher in mollusks, whereas Cr concentrations were significantly higher in aquatic plants than in mollusks, crustaceans, and fish (p < 0.01). Heavy metals exhibit different patterns of trophic transfer in food web. Cd, Cr, Cu, and Pb tended to be efficiently biodiluted with increasing trophic levels in food web (trophic magnification factor, TMF < 1; p < 0.05). The concentration of Zn increased with increasing trophic level; however, it exhibited a TMF of only 1.03, and was not significantly correlated with δ¹⁵N (p > 0.05), indicating neither biomagnification or biodilution in the food web.

Significance of conducting polyaniline based composites for the removal of dyes and heavy metals from aqueous solution and wastewaters - A review

Dyes and heavy metals pollution have become a major environmental concern worldwide. Various methods, such as advanced oxidation, biodegradation, precipitation, flocculation, ultra filtration, ion-exchange, electro-chemical degradation and coagulation, have been proposed for the removal of dyes and heavy metals from contaminated wastewater. Of these methods, adsorption and detoxification are considered as the most promising and economically viable. Polyaniline-based composites, a material prepared by combining polyaniline with one or more similar or disimilar materials, have been reported as good adsorbents to remove and detoxify different groups of pollutants due to their unique physical and chemical properties. In the last decade, several studies have reported the effective adsorption (∼95%) of dyes and heavy metals onto polyaniline based composites. Furthermore, some polyaniline -composites reduced the adsorbed heavy metals into less toxic state. This review compiles the application of different polyaniline composites for adsorption and/or detoxifcation of dyes and heavy metals and documents composite preparation methods, morphology and properties of the composites, and mechanism of dyes and heavy metals adsorption. Based on the avilabile literature, this review suggests that more studies are warranted to understand the influence of various conditions and experimental variables on dyes and heavy metals removal from wastewater and/or aqueous solution.

Seasonal variations on trace element bioaccumulation and trophic transfer along a freshwater food chain in Argentina

Río Tercero Reservoir (RTR) is the largest artificial reservoir in the province of Córdoba (Argentina). Water, sediment, plankton, shrimp (Palaemonetes argentinus), and fish (Odontesthes bonariensis) were collected during the wet season (WS) and dry season (DS) from this reservoir. Concentrations of Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, P, Pb, Se, U, and Zn were determined to investigate their respective bioaccumulation pattern and trophic transfer in the food chain. Results showed that their concentrations in water were rather low except Pb, which exceed the limits considered as hazardous for aquatic life. The enrichment factor (EF) in sediments showed that most of the element were derived from anthropogenic sources. Furthermore, the bioaccumulation factor (BAF) determined that the elements undergo bioaccumulation, especially in organisms such as plankton. The invertebrates were characterized by the highest BAF for Cu, P, and Zn in both seasons; Ag, As, and Hg during WS; and Se during DS. Fish muscle registered the highest BAF for Hg (DS) and Se (WS). A significant decrease in Al, As, Cd, Cr, Cu (DS) Fe, Mn, Ni, Pb, Se, U, and Zn (DS) concentrations through the trophic chain was observed, indicating biodilution. Some notable exceptions were found as Cu (WS), Hg (DS), and P (both season) that showed biomagnification. Further studies are needed to establish differential behavior with different species and pollutant, particularly when the potential transfer is to edible organisms.

Influence of variable salinity and low light on copper accumulation in the potential seagrass bioindicator, Zostera muelleri

Utilising a potential coastal trace element bioindicator requires understanding its accumulation patterns under varying environmental scenarios. The present study aimed to understand, from two experiments, the influence and effect of low light (15.3 μmol photons m^-2 s^-1) and variable salinity (normal 36 and reduced 29) on Zostera muelleri accumulating variable Cu concentrations (control, low 5 μg L^-1 and high 50 μg L^-1) in order to determine its capability as a potential trace element bioindicator. Initial (24 h) leaf Cu concentration was in proportion to exposure Cu concentrations, irrespective of manipulated environmental conditions, suggesting passive accumulation. Final below-ground Cu concentrations, during the low light experiment, significantly increased over time, suggesting active Cu accumulation. Zostera muelleri leaves could act as a Cu bioindicator at times of reduced light and salinity while further interpretation is required of below-ground Cu concentrations. It is recommended that Z. muelleri could be utilised as a Cu bioindicator.

Coastal bays and coral cays: Multi-element study of Chelonia mydas forage in the Great Barrier Reef (2015-2017)

There is increasing interest in understanding potential impacts of complex pollutant profiles to long-lived species such as the green sea turtle (Chelonia mydas), a threatened megaherbivore resident in north Australia. Dietary ingestion may be a key exposure route for metals in these animals and marine plants can accumulate metals at higher concentrations than the surrounding environment. We investigated concentrations of 19 metals and metalloids in C. mydas forage samples collected from a group of offshore coral cays and two coastal bays over a period of 2-3 years. Although no samples exceeded sediment quality guidelines, coastal forage Co, Fe, and V concentrations were up to 2-fold higher, and offshore forage Sr concentrations were ~3-fold higher, than global seagrass means. Principal Component Analysis differentiated coastal bay from coral cay forage according to patterns consistent with underlying terrigenous-type or marine carbonate-type sediment geochemistry, such that coastal bay forage was higher in Fe, Co, Mn, Cu, and Mo (and others) but forage from coral cays was higher in Sr and U. Forage from the two coastal bays was differentiated according to temporal variation in metal profiles, which may be associated with a more episodic sediment disturbance regime in one of the bays. For all study locations, some forage metal concentrations were higher than previously reported in the global literature. Our results suggest that forage metal profiles may be influenced by the presence of some metals in insoluble forms or bound to ultra-fine sediment particles adhered to forage surfaces. Metal concentrations in Great Barrier Reef forage may be present at levels higher than expected from the global seagrass literature and appear strongly influenced by underlying sediment geochemistry.

Assessing environmental contamination from metal emission and relevant regulations in major areas of coal mining and electricity generation in Australia

The Hunter and Latrobe Valleys have two of the richest coal deposits in Australia. They also host the largest coal-fired power stations in the country. We reconstructed metal deposition records in lake sediments in the Hunter and Latrobe Valleys to determine if metal deposition in freshwater lakes have increased in the region. The current regulatory arrangement applied to metal emissions from coal-fired power stations in Australia are presented, discussing their capacity to address future increases in metal deposition from these sources. Sediment records of spheroidal carbonaceous particles (SCPs), a component of fly-ash, were also used as an additional line of evidence to identify the contribution of industrial activities related to electricity generation to metal deposition in regions surrounding open-cut coal mines and coal-fired power stations. Sediment metal concentrations and SCP counts in the sedimentary records, from the Hunter and Latrobe Valleys, both indicated that open-cut coal mining and the subsequent combustion of coal in power stations has most likely resulted in an increase in atmospheric deposition of metals in the local region. In particular, the metalloids As and Se showed the greatest enrichment compared to before coal mining commenced. Although the introduction of bag filters at Liddell Power Station and the decommissioning of Hazelwood Power Station appear to have resulted in a decrease of metal deposition in nearby lakes, overall metal deposition in the environment is still increasing. The challenge for the years to come will be to develop better regulation policies and tools that will contribute to reduce metal emissions in these major electricity production centres in Australia.

Speciation and source apportionment of polycyclic aromatic compounds (PACs) in sediments of the largest salt water lake of Australia

Great ecological and human health risks may arise from the presence of polycyclic aromatic hydrocarbons (PAHs) in aquatic environments and particularly in sediments, where they often partition. In spite of the apparent risk, knowledge about PAHs and their polar derivatives in sediments is limited. We, therefore, carried out an assessment of the concentrations of parent PAHs and their derivatives (polar PAHs) in sediments of Lake Macquarie: the largest saltwater lake in the southern hemisphere. A total of 31 sediment samples along the pollution prone western shoreline of the estuary were analysed. Multiple source apportionment methods were used to investigate PAH sources contributing to parent and polar PAH concentrations in the estuarine sediments. Concentration levels were highest for high molecular weight (HMW) PAHs compared to low molecular weight (LMW) PAHs. The highest PAH concentrations were recorded for oxygenated PAHs (oxy-PAHs) compared to parent and other polar PAHs. Polycyclic aromatic hydrocarbon diagnostic ratios and compositional analysis showed that PAHs in Lake Macquarie were predominantly pyrogenic exhibiting strong positive correlation (R² = 0.972) with total PAH concentrations. Principal Component Analysis (PCA) identified three groupings of PAHs with oxy-PAHs and NPAHs dominating (40.2%). Carbazole, a heterocyclic PAH, was also a prominent contributor to sediment PAH concentrations. Atmospheric deposition, coal combustion and vehicular emissions were implicated as the major contributors to sediment pollution.

Cycling and total risks of multiple As fractions in the Beijing-Tianjin-Hebei area on the agricultural plain, China

The high toxicity of As can cause serious health risks for humans; therefore, understanding the behavior of As in weakly alkaline soil conditions relevant to agricultural plains is important. To investigate the mobility and total risks of multiple fractions of As, 230 pairs of soil (including soil cores) and, wheat grain, and corresponding groundwater samples and 38 atmospheric deposition samples were collected from agricultural soil in the Beijing-Tianjin-Hebei region, China, which is a typical wheat-growing area. Seven fractions of As, namely, water-soluble (As1), exchangeable (As2), carbonate-bound (As3), humic acid-bound (As4), Fe-Mn oxide-bound (As5), organic matter-bound (As6), and residual (As7) As, were analyzed using a sequential extraction procedure to better understand and confirm the relationship among these different forms. Correlation and principal components analyses showed a significant relationship among As1-As5, and As in atmospheric deposits and As in groundwater and soil samples showed a positive relationship. As found in wheat, therefore, mainly originated from the soil and atmospheric deposits, and indirectly from the groundwater. As in the soil samples was mainly controlled by Mn and Fe₂O₃ based on the vertical distribution of soil cores and correlation analysis. The health risk assessments showed that As in the multiple fractions did not form a potential non-cancer risk for children and adults. However, residents could still face the risk of developing cancer by ingesting wheat and drinking the groundwater. The findings of this study have important implications for understanding the hydrological/geochemical behavior of As and the soil and water quality in a wide range of environmental settings. Additionally, our findings provided arguments for decreasing the concentrations of As in the wheat production system and to remind residents to decrease ingestion of their staple food (wheat) and drink less of the local groundwater.

Bioaccumulation and health risk assessment of heavy metals to bivalve species in Daya Bay (South China Sea): Consumption advisory

Bivalves are one of the key components of the biogeochemical cycle in the marine system, and respond to heavy metal (HM) sensitively as filter feeders. To determine relationship of HMs in edible bivalve and seawater and HM effects on human health when digesting bivalves, HMs were analyzed in bivalves and seawater. The results showed that the mean HM concentrations in bivalves decreased in the order of Zn > Cu > Cr > Pb > As > Cd > Hg. Generally, all the bioconcentration factor values of bivalves were higher than 100, suggesting that bivalves have a high bioaccumulation ability. Nonmetric multidimensional scaling analysis indicated that all bivalves have a high bioaccumulation capacity for Cu and Zn. It was found that there are health risks associated with consuming bivalves, and children are more vulnerable than adults. Finally, the maximum allowable consumption rates of non-carcinogenic and carcinogenic risk were determined. These results provide the underlying insights needed to guide the consumption of seafood.

15N Stable Isotope Labeling PSTs in Alexandrium minutum for Application of PSTs as Biomarker

The dinoflagellate Alexandrium minutum (A. minutum) which can produce paralytic shellfish toxins (PSTs) is often used as a model to study the migration, biotransformation, accumulation, and removal of PSTs. However, the mechanism is still unclear. To provide a new tool for related studies, we tried to label PSTs metabolically with ¹⁵N stable isotope to obtain ¹⁵N-PSTs instead of original ¹⁴N, which could be treated as biomarker on PSTs metabolism. We then cultured the A. minutum AGY-H46 which produces toxins GTX1-4 in f/2 medium of different ¹⁵N/P concentrations. The ¹⁵N-PSTs’ toxicity and toxin profile were detected. Meanwhile, the ¹⁵N labeling abundance and ¹⁵N atom number of ¹⁵N-PSTs were identified. The ¹⁴N of PSTs produced by A. minutum can be successfully replaced by ¹⁵N, and the f/2 medium of standard ¹⁵N/P concentration was the best choice in terms of the species’ growth, PST profile, ¹⁵N labeling result and experiment cost. After many (>15) generations, the ¹⁵N abundance in PSTs extract reached 82.36%, and the ¹⁵N atom number introduced into GTX1-4 might be 4–6. This paper innovatively provided the initial evidence that ¹⁵N isotope application of labeling PSTs in A. minutum is feasible. The ¹⁵N-PSTs as biomarker can be applied and provide further information on PSTs metabolism.

How significant is atmospheric metal contamination from mining activity adjacent to the Tasmanian Wilderness World Heritage Area? A spatial analysis of metal concentrations using air trajectories models

This study investigated metal contamination from historical mining in lakes in the Tasmanian Wilderness World Heritage Area (TWWHA) and surrounding region. The largest increase in sedimentation and metal contamination occurred ca. 1930 when open-cut mining commenced and new mining technology was introduced into the region. The geochemical signal of lake sediments changed from reflecting the underlying geology and lithology to that reflecting mining activities. The HYSPLIT air particle trajectory model explains metal distribution in the lakes, with those in the northwest region closest to the mines having the highest metal contamination. Lake metal concentrations since mining activities commenced are in the order: Owen Tarn > Basin Lake > Perched Lake > Lake Dove > Lake Dobson > Lake Cygnus, with Perched Lake and Lakes Dove, Dobson and Cygnus in the TWWHA. Metal contamination affected centres up to 130 km down-wind of mining sites. Enrichment factors (EF) for Pb, Cu, As and Cd are >1 for all lakes, with Owen Tarn and Basin Lake having very high EFs for Cu and Pb (98 and 91, respectively). Pb, Cu, As and Cd concentrations are above the Australia/New Zealand lower sediment guidelines, with Pb, Cu and As above the high guidelines in Owen Tarn and Basin Lake. This study demonstrated the legacy of metal contamination in the TWWHA by mining activities and the consequences of a lack of execution of environmental regulations by past governments in Tasmania.

Baseline assessment of heavy metals content and trophic position of the invasive blue swimming crab Portunus segnis (Forskål, 1775) in the Gulf of Gabès (Tunisia)

This study provides a baseline assessment of cadmium, copper, iron, manganese, lead, and zinc concentrations in muscles, gills, and exoskeleton of the Lessepsian blue swimming crab Portunus segnis captured in the Gulf of Gabès (Southern Mediterranean Sea, Tunisia) in November 2015. Furthermore, the species' trophic position is estimated using CN stable isotope analysis. The exoskeleton showed the lowest metal contents; in soft tissues, the essential Cu, Fe, and Zn and the non-essential Cd, Mn, and Pb showed the highest and lowest concentrations, respectively. The crab was characterized by a trophic position of 3.32, confirming its carnivorous trophic habits. Compared with literature data on invertebrate and fish species from the same area, Cd and Pb resulted remarkably low in the crab's soft tissues, while a food web-scale dilution effect was indicated. The need of a comprehensive assessment of the ecological impact of Portunus segnis in invaded Mediterranean waters is discussed.