Metals in sediments and mangrove oysters (Crassostrea rhizophorae) from the Caroni Swamp, Trinidad

Bioaccumulation of estuarine pollutants in leaf oysters (Isognomon ephippium) on the mid-north coast, New South Wales, Australia

Filter feeding bivalves are useful bioindicators for the detection of biologically available pollutants. We investigated trace metals, metalloids, and pesticides in leaf oyster (Isognomon ephippium) soft tissue and shells and compared them to sediment in five estuaries in northern New South Wales, Australia. Concentrations of Pb, Cr, Mn, Ni, Fe and Al were higher in sediments, whereas Zn, Cd, Ag, Hg, Se and As bioaccumulated in the soft tissue. The amount of Cu, Hg and Ni in the sediment from Tweed and Richmond River estuaries exceeded the Australian national sediment quality guideline values. Only one pesticide, atrazine, was detected in leaf oyster soft tissue. Combinations of six elements in the soft tissue were the best predictors of oyster condition index and shell size, whereas sediment contaminants showed weak relationships. Overall, the bioaccumulation of metals and metalloids increases with leaf oyster size and reduces leaf oyster condition, suggesting these large bivalves are useful bioindicators for pollution in estuarine environments.

Heavy metals accumulation in bivalve mollusks collected from coastal areas of southeast China

The distribution of six heavy metal and metalloids (As, Cd, Cr, Hg, Ni and Pb) was analyzed in 597 bivalve mollusks (8 species) collected from coastal areas of southeast China. Target hazard quotient, total hazard index, and target cancer risk were calculated to evaluate potential human health risks from bivalve consumption. The mean concentrations of As, Cd, Cr, Hg, Ni and Pb were 1.83, 0.581, 0.111, 0.0117, 0.268 and 0.137 mg kg^-1 wet weight in bivalves. The average estimated daily intakes for As, Cd, Cr, Hg, Ni and Pb were 1.156, 0.367, 0.07, 0.007, 0.167 and 0.087 μg kg^-1 body weight/day. Health risk assessment showed that there was no non-carcinogenic health risk to general residents to these metals from consumption of bivalves. Cd intake through mollusks posed a potential cancer risk. Accordingly, regular monitoring for heavy metals, especially Cd is recommended with respect to potential contaminant on marine ecosystems.

Occurrence and Health Risk Assessment of Heavy Metals in the Blue Land Crab (Cardisoma guanhumi) from a Tropical Mangrove Swamp

Coastal ecosystems in the Caribbean are vulnerable to pollution from land-based activities with possible impacts to human health. Ten heavy metals in the blue land crab, Cardisoma guanhumi, harvested from the Caroni Swamp, Trinidad, were investigated in the wet and dry seasons. Metal concentrations (µg g^-1 dry weight) in crab tissue were: As (0.15-6.46), Ba (0.69-19.64), Cd (< 0.001-3.36), Cr (0.63-3.64), Cu (26.64-120.31), Hg (0.09-1.83), Ni (1.21-9.33), Se (0.19-1.55), V (0.16-0.69) and Zn (121.06-494.3). There were seasonal differences in the concentration of some heavy metals and, Cu and Zn exceeded the local maximum permissible levels for fish and shellfish at several sites in either one or both seasons. Health risk assessment based on estimated daily intake, target hazard quotient and hazard index revealed that Cardisoma guanhumi harvested from the Caroni Swamp, does not pose a health risk to consumers.

Bioaccumulation of trace metals and speciation of copper and zinc in Pacific oysters (Crassostrea gigas) using XANES/EXAFS spectroscopies

Copper (Cu) and zinc (Zn) concentrations in oyster soft tissues can be particularly high due to contamination, leading to extremely green/blue colors. This raises key questions regarding the behavior and speciation of trace metals in oyster soft tissues. This study investigated trace metal concentration profiles of contaminated Pacific oyster (Crassostrea gigas) soft tissues collected from trace metal-contaminated coastal area of Xiangshan District using inductively coupled plasma optical emission spectrometry (ICP-OES), energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Moreover, Cu and Zn speciation in contaminated and non-contaminated oyster soft tissues were investigated by X-ray absorption near edge structure spectroscopy/extended X-ray absorption fine structure (XANES/EXAFS) spectroscopic methods. The contents of Cu (1,100-1,400 mg/kg) and Zn (500-700 mg/kg) dry weight were high in oyster soft tissue samples. The XANES/EXAFS results revealed that Cu and Zn existed primarily as copper (II) oxide (CuO) and zinc oxide (ZnO) in contaminated oysters. Furthermore, Cu and Zn formed clusters with Cu-O and Zn-O interatomic distances of 1.97 and 2.21 Å, (coordination numbers 1.0 and 5.6), respectively. In non-contaminated oysters, the less abundant Cu and Zn existed mainly as copper(I) sulfide (Cu₂S) and zinc sulfide (ZnS) forming clusters with Cu-S and Zn-S (thiolates) bond distances of 2.09 and 1.23 Å (coordination numbers of 4.6 and 2.4). These results provide further understanding on the chemical speciation of Cu and Zn in contaminated and non-contaminated oyster soft tissues as well as the bioaccumulation of trace metals in the oyster soft tissues.

Heavy metals bioconcentration in Crassostrea rhizophorae: A site-to-site transplant experiment at the Potengi estuary, Rio Grande do Norte, Brazil

In this study, we analyzed the bioconcentration of Cd, Cr, Cu, Pb, Ni, and Zn in the soft tissue of transplanted oysters in two sites in the Potengi estuary for six months. Native oysters collected before and after the transplantation experiment provided the background for statistical analyses. Cd, Cr, and Ni showed a strong inverse correlation with oyster weight in both sites. Transplantation upstream of the estuary presented increasing concentrations of Zn, Cu, and Pb and condition index (CI) and decreasing trends for Cd and Ni, whereas Cr oscillated significantly. In the downstream transplantation, Cu, Pb, and Zn and the CI tended to decrease, whereas for Ni, Cd, and Cr, the concentrations increased. Spatiotemporal principal component analysis correlated these results mainly with proximity to the polluting source, seasonality, and previous exposure to heavy metals. These results helped interpret the responses provided by these biomonitors to environmental changes, whether they are natural or anthropogenic.

Chemical contamination assessment in mangrove-lined Caribbean coastal systems using the oyster Crassostrea rhizophorae as biomonitor species

This paper aims to contribute to the use of mangrove cupped oyster, Crassostrea rhizophorae, as a biomonitor species for chemical contamination assessment in mangrove-lined Caribbean coastal systems. Sampling was carried out in eight localities (three in Nicaragua and five in Colombia) with different types and levels of contamination. Oysters were collected during the rainy and dry seasons of 2012-2013 and the tissue concentrations of metals, polycyclic aromatic hydrocarbons (PAHs), and persistent organic pollutants (POPs) were determined. Low tissue concentrations of metals (except Hg) and PAHs; moderate-to-high tissue concentrations of Hg, hexachlorocyclohexanes (HCHs), and dichlorodiphenyl-trichloroethanes (DDTs); detectable levels of chlorpyrifos, polychlorinated biphenyls (PCBs) (mainly CB28, CB118, CB138 and CB 153) and brominated diphenyl ethers 85 (BDE85); and negligible levels of musks were recorded in Nicaraguan oysters. A distinct profile of POPs was identified in Colombia, where the tissue concentrations of PCBs and synthetic musk fragrances were low to moderate, and Ag, As, Cd, Pb, and PAHs ranged from moderate to extremely high. Overall, the values recorded for HCHs, DDTs and PCBs in Nicaraguan mangrove cupped oysters greatly exceeded the reference values in tissues of C. rhizophorae from the Wider Caribbean Region, whereas only the levels of PCBs were occasionally surpassed in Colombia. Different contaminant profiles were distinguished between oysters from Nicaragua and Colombia in radar plots constructed using the main groups of contaminants (metals, PAHs, musks, PCBs, and organochlorine pesticides (OCPs)). Likewise, integrated pollution indices revealed differences in the levels of contaminants. Moreover, the profiles and levels in oyster tissues also varied with season. Thus, principal component analysis clearly discriminated Nicaraguan and Colombian localities and, especially in Colombia, seasonal trends in chemical contamination and differences amongst localities were evidenced. The geographical and environmental disparity of the studied scenarios may represent to a large extent the diversity of mangrove-lined Caribbean coastal systems and therefore the present results support the use of C. rhizophorae as suitable biomonitor species at Caribbean regional scale, where seasonal variability is a major factor controlling pollutant mobility and bioavailability.

Bioavailability of cadmium, copper, mercury, lead, and zinc in subtropical coastal lagoons from the southeast Gulf of California using mangrove oysters (Crassostrea corteziensis and Crassostrea palmula)

Cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn) were assessed in the edible tissues of Crassrotrea corteziensis oysters collected during the rainy and dry seasons in 27 sites from 8 coastal lagoons of the southeast Gulf of California. In addition, C. palmula oysters were sampled at 9 sites from the same mangrove roots where C. corteziensis oysters were collected. Metal analyses were performed by flame atomic absorption spectrophotometry (Cd, Cu, and Zn), graphite furnace (Pb), and cold vapor detection (Hg). The obtained mean levels were (µg g(-1) dry weight) as follows: Cd 6.05 ± 2.77, Cu 60.0 ± 33.4, Hg 0.38 ± 0.17, Pb 1.11 ± 0.63, and Zn 777 ± 528 µg g(-1). For all metals except Hg, the concentrations were greater during dry season than during rainy seasons. The high levels, particularly that for Cd, were related to upwelling along the eastern Gulf of California. High Hg levels in the rainy season were associated with the transport of materials from the watershed to the lagoon. Shrimp farming, agriculture, and other sources were considered as potential sources to explain the differences in metal bioavailability in the 8 lagoons. The mean concentrations of Cd (Santa María-La Reforma lagoon), Cu [San Ignacio-Navachiste-El Macapule (SINM), Urías (URI), and Altata-Ensenada del Pabellón lagoons], and zinc (Zn) (URI, Santa María-Ohuira-Topolobampo, El Colorado, and SINM lagoons) during the dry season were greater than the maximum permissible limits. C. palmula collected in 8 sites where they were present simultaneously with C. corteziensis had consistently greater metal levels than C. corteziensis, but correlation analyses showed a high and significant (P < 0.05) correlation between metal concentrations in both species. The correlation equations obtained are useful where the same species is not distributed and is necessary to compare results from distinct regions.

Carbohydrate-based activated carbon with high surface acidity and basicity for nickel removal from synthetic wastewater

The feasibility of preparing activated carbon from carbohydrates (glucose, sucrose and starch) with H₃PO₄ activation was evaluated by comparing its physicochemical properties and Ni(ii) adsorption ability with a reference Phragmites australis-based activated carbon.

Polycyclic aromatic hydrocarbons (PAHs) in Crassostrea rhizophorae and Cathorops spixii from the Caroni Swamp, Trinidad, West Indies

Dietary exposure to polycyclic aromatic hydrocarbons (PAHs) may pose serious threats to human health. However, within the Caribbean, quantitative assessments regarding the risks associated with dietary PAH exposure remain sparse. This study investigated PAH presence in edible biota from the Caroni Swamp and quantitatively assessed the potential health threat to human consumers. Mangrove oysters (Crassostrea rhizophorae) and Madamango sea catfish (Cathorops spixii) collected from seven sites in the Caroni Swamp were analysed for 16 priority PAHs. Total PAH levels ranged from 109 ± 18.4 to 362 ± 63.0 ng/g dry wt. in Crassostrea rhizophorae and 7.5 ± 0.9 to 43.5 ± 25.5 ng/g dry wt. in Cathorops spixii (average ± standard deviation). Benzo[a]pyrene levels in Crassostrea rhizophorae at all sites exceeded international guidelines from British Colombia (Canada) and the European Union (EU). Incremental lifetime cancer risk (ILCR) values based on the ingestion of Crassostrea rhizophorae ranged from 8.4 × 10(-6) to 1.6 × 10(-5) and slightly exceeded the commonly used 1 × 10(-6) acceptable level of risk. Information from this study is important in understanding the potential health risks posed by PAHs, it is critical towards the protection of public health, and it serves as a useful baseline for comparison with future work.