The determination of dissolved manganese and cadmium in sea water at low nmol 1−1 concentrations by chelation and extraction followed by electrothermal atomic absorption spectrometry

Long-term variation of dissolved metals and metalloid in the waters of an Atlantic mesotidal estuary (Sado Estuary, Portugal)

Estuaries have long been preferred sites of human settlement due to the benefits regarding proximity to fresh water and the ocean. As such, these environments have been subject to increasing anthropogenic pressures, resulting in issues of pollution and contamination. However, since the second half of the 20th century an environmental concern has reflected in the development of legislation, monitoring programmes and measures to diminish and control those impacts. The study presented herein integrates metals and metalloid concentrations from surface water samples obtained in a long-term monitoring programme (1986-2020) conducted in the Sado Estuary. The results obtained show a decrease and stabilisation of the concentrations of elements (between 81 % for Pb and 11 % for As in the average concentrations, between 83 % for Pb and 11 % for Cd in the median concentrations, and an increase of 1 % in the As median values). Nevertheless, high concentrations were still observed in the stations closest to the industrial area and the main freshwater to confluence with the estuary. Despite the efforts in improving the environmental quality of the Sado Estuary, possible effects in native species such as cuttlefishes and oysters are still a possibility, particularly in the stations where higher concentrations were registered, as well as close to nurseries as a result of trace metal transport through currents and tides.

Green oysters occurring in an industrial harbor in Central Taiwan

Green oysters were found within the Mailiao industrial harbor (MIH) located in Central Taiwan. The metal concentrations in seawater (dissolved and particulate phases), sediment and oyster samples collected within the MIH were analyzed to examine the green oysters. The dissolved and particulate metal concentrations ranged within 0.008-1.47μgl^-1 and 0.97-799.2mgkg^-1, respectively. The Cu concentration in seawater was dominated in the dissolved phase. In contrast, Cr, Pb and Zn in seawater were chiefly present in the particulate phase. The metal concentrations in sediment and oyster samples ranged within 0.02-148.4mgkg^-1 and 0.18-1238mgkg^-1 (dry W.), respectively. No anomalous values were found in the analyzed samples, except the Cu content in the oyster samples ranged within 274-1238mgkg^-1. The relatively high bioconcentration factor of Cu in oyster and the longer exposure time induced the green oysters occurred within the MIH.

Water column characterisation on the Azores platform and at the sea mounts south of the archipelago

This study provides data concerning the hydrography and water chemistry of the Atlantic region between 29-38° N and 27-31° W, and establishes background values for dissolved Cu, Cd, Pb and As. Three water masses were identified: the Eastern North Atlantic Central Water (ENACW), the Mediterranean Water (MW) and the North Atlantic Deep Water (NADW). The ENACW exhibits a clear meridional gradient of temperature and salinity, with comparatively high values at the southern sites and lower values on the Azores platform. The ENACW, which includes the euphotic zone, also had comparatively high concentrations of oxygen and lower concentrations of nutrients and metals. The Cu, Cd and Pb results suggest that new background concentrations for OSPAR Region V (the Wider Atlantic) should be established as follows: 0.15-13 nM for Cu, 0.05-1.4 nM for Cd and 0.03-5 nM for Pb. The background concentrations of As for OSPAR Region V should be 7-28 nM.

Evaluation of the potential impact of polluted sediments using Manila clam Ruditapes philippinarum: bioaccumulation and biomarker responses

An assessment was made to monitor the short-term impact of heavily polluted sediments that may move out from the brackish man-made Lake Shihwa outside of the sea dike due to operations of a tidal power plant. Here, we exposed the Manila clam Ruditapes philippinarum collected from the western coast of Korea to natural sediment under lab condition for 96 h. Sediments were collected from Lake Shihwa and outside of the sea dike representing polluted and reference conditions, respectively. The results of chemical analysis revealed that the concentrations of nonylphenol and heavy metals in water and sediment from the inner region of Lake Shihwa were significantly higher than those of reference sediments. After 48 and 96 h of exposure, 30 specimens of clams were sampled from each experimental condition, and concentrations of nonylphenol and metals were measured in clams, water, and sediments. Several biomarkers, including concentrations of metallothionein-like proteins, and activities of the antioxidant enzymes glutathione S-transferase and catalase were determined in clams to characterize the effects of polluted sediments to clams. After 96 h of exposure, R. philippinarum assimilated nonylphenol up to 71 times compared to initial concentrations. However, there was no apparent uptake of heavy metals into the clams. Additionally, antioxidant enzymes exhibited higher activities in clams exposed to the polluted sediment. The results of the present study with physiological responses in R. philippinarum suggest that sediment transportation caused by the operation of a tidal power plant in Lake Shihwa will have striking effects on benthic organisms in the adjacent coastal area.

Diverse styles of submarine venting on the ultraslow spreading Mid-Cayman Rise

Thirty years after the first discovery of high-temperature submarine venting, the vast majority of the global mid-ocean ridge remains unexplored for hydrothermal activity. Of particular interest are the world's ultraslow spreading ridges that were the last to be demonstrated to host high-temperature venting but may host systems particularly relevant to prebiotic chemistry and the origins of life. Here we report evidence for previously unknown, diverse, and very deep hydrothermal vents along the approximately 110 km long, ultraslow spreading Mid-Cayman Rise (MCR). Our data indicate that the MCR hosts at least three discrete hydrothermal sites, each representing a different type of water-rock interaction, including both mafic and ultramafic systems and, at approximately 5,000 m, the deepest known hydrothermal vent. Although submarine hydrothermal circulation, in which seawater percolates through and reacts with host lithologies, occurs on all mid-ocean ridges, the diversity of vent types identified here and their relative geographic isolation make the MCR unique in the oceans. These new sites offer prospects for an expanded range of vent-fluid compositions, varieties of abiotic organic chemical synthesis and extremophile microorganisms, and unparalleled faunal biodiversity--all in close proximity.

Trace metals in seawater and copepods in the ocean outfall area off the northern Taiwan coast

The distribution, partitioning and concentrations of trace metals (Cd, Cr, Cu, Fe, Mn, Pb and Zn) in seawater, including dissolved and particulate phases, and in copepods in the ocean outfall area off the northern coast of Taiwan were investigated. Normalization of metal concentrations to the background metal concentration to yield relative enrichment factors (EF), which were used to evaluate the contamination of dissolved and particulate trace metals in seawater around the ocean outfall. The EF results indicated that the outfall area was significantly contaminated by dissolved Fe and Zn, and by particulate Fe, Cr, Cu, Pb and Zn. In addition, most trace metals were chiefly in the particulate phase. The average percentage of total metal concentrations (dissolved plus particulate phases) bound by suspended particulate matter followed the sequence Al(95%) = Mn(95%) > Pb(88%) > Cu(86%) > Fe(72%) > Zn(32%) > Cr(17.5%) > Cd(3.4%). Therefore, metal contamination is better evaluated in solid phase than in the dissolved phase. The concentration ranges of trace metals in the copepods, Temora turbinata, Oncaea venusta and Euchaeta rimana, near the outfall were: Cd, 0.23-1.81 microg g(-1); Cr, 16.5-195 microg g(-1); Cu, 14-160 microg g(-1); Fe, 256-7255 microg g(-1); Mn, 5.5-80.8 microg g(-1); Pb, 2.6-56.2 microg g(-1); Zn, 132-3891 microg g(-1); and Al, 0.21-1.13%. Aluminum, and probably Fe, seemed to be the major elements in copepods. The concentrations of trace metals in copepods, especially Temora turbinata, near the outfall were generally higher than those obtained in the background station. The mean increase in bioconcentration factor of metals in copepods ranged from 4 to 7 and followed the sequence Al(6.4) > Cu(6.2) > Fe(6.0) > Zn(5.7) > Pb(5.6) > Cr(5.5) > Cd(5.1) > Mn(4.7). Therefore, marine copepods in the waters of northern Taiwan can accumulate trace metals over background concentrations and act as contamination indicators.

Interactions between Cd, Cu, and Zn influence particulate phytochelatin concentrations in marine phytoplankton: laboratory results and preliminary field data

The effect of metal interactions on phytochelatin production by marine phytoplankton has received little attention but yet is critical to understanding the biochemical production of this potentially important metal-binding ligand in the field. Cd, Cu, and Zn additions were made singly and in combination to three species of laboratory cultures and to a natural algal assemblage from pristine coastal seawater. In the laboratory cultures intracellular phytochelatin varied with metal exposure and demonstrated metal- and concentration-dependent synergisms and antagonisms. Most notably, the addition of all three metals together greatly suppressed phytochelatin production in all cultures. Particulate phytochelatin was also measured at two field sites. In the field, phytochelatin production is related to ambient Cd, Cu, and Zn levels, and the deviations from the dose-response relationship are potentially explained by metal interactions similar to those observed in the laboratory cultures. Though particulate glutathione concentrations were very low in some field samples, it did not appear to limit phytochelatin production. Particulate phytochelatin concentrations in samples from both field sites were very similar to those measured in the laboratory cultures when exposed to all three metals together, and thus phytochelatin levels in the field may be regulated by the interaction of Cd, Cu, and Zn.