Comparative studies on the distribution of heavy metals in the oceans and coastal waters

Characterization of sargassum accumulated on Dominican beaches in 2021: Analysis of heavy, alkaline and alkaline-earth metals, proteins and fats

This paper presents the characterization of sargassum that reached the shores of eight Dominican beaches in 2021. The analysis of heavy, alkaline and alkaline-earth metals was performed by ICP-OES. Twelve heavy metals were studied, with the highest concentrations corresponding to Fe, As, and Zn. Regarding the alkaline and alkaline-earth metals, the highest concentrations were detected for Ca, K, Na and Mg. The high values of arsenic and alkali and alkaline-earth metal salts do not suggest using these algae in agriculture. It is recommended to carry out arsenic speciation studies to assess whether the form in which it is found is bioavailable for plants and animals. The heavy metal contamination index was determined, which ranged between 0.318 and 3.279. Finally, for the first time in the country, the organic fraction of sargassum was analyzed.

Copper Requirement and Acquisition by Marine Microalgae

Copper is a critical metal nutrient required by marine microalgae but may be toxic when supplied in excess. Maintaining an optimal intracellular Cu content is thus fundamentally necessary for microalgae and relies on cellular regulatory metabolisms and the process of Cu uptake that buffers the variation in environmental Cu availability. In this article the current progress in understanding the Cu requirements and acquisition mechanisms of marine microalgae is reviewed. Cu requirement by microalgae is primarily determined by the amount of Cu-dependent enzymes involved in cellular metabolisms and can be adjusted by Cu-sparing pathways. Decrease in metabolic Cu quotas caused a decline in the abundance of cuproenzymes and the dependent cellular metabolisms, and an induction of Cu acquisition pathways. Conventional models of Cu uptake describe the dependence of Cu uptake rate on free Cu²⁺ ions or kinetically labile species. A reductive, high-affinity Cu uptake system in marine microalgae is identified which enables cells to directly utilize organically complexed Cu, highlighting the importance of cell surface Cu reduction in the marine Cu cycle. This review provides new insights into Cu uptake models that may update the existing knowledge of Cu availability in the ocean.

First assessment of Atlantic open ocean Sargassum spp. metal and metalloid concentrations

Over the last decade, increasing proliferations of Atlantic Sargassum populations have led to massive beaching with disastrous environmental consequences. This study is a preliminary assessment of open ocean Sargassum spp. element concentration to assess their potential contribution on coastal ecosystems. Sargassum spp. samples from seven sites, collected along a transect from the center of the Atlantic Ocean to near the coast of Martinique (French West Indies), were analyzed to determine their potential metal and metalloid enrichment. Mean element concentrations from the Sargassum spp. samples were ranked in the following descending order: As > Fe > Mn > Al > Zn > V > Ni > Cu > Cr > Cd > Hg. Element concentrations are relatively low compared to previous results of beached Sargassum spp. except for As that need to be carefully considered before reusing Sargassum spp.

Pollution assessment and land use land cover influence on trace metal distribution in sediments from five aquatic systems in southern USA

Trace elements and heavy metals concentrate in aquatic sediments, potentially endangering benthic organisms. Comparing the concentration of metals in different aquatic bodies will help evaluate their accumulation and distribution characteristics within these systems. Metal pollution and enrichment indices in sediments from diverse aquatic systems in Southern USA, including agricultural ponds, man-made reservoir, river, swamp, and coastal environment were investigated. Following total digestion of the sediments, the concentrations of chromium (Cr), cobalt (Co), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), antimony (Sb), lead (Pb), and uranium (U) were measured using inductively coupled plasma-mass spectrometry (ICP-MS). Pb was found to be highly enriched in the sediment samples from all five environments. The samples from coastal and agricultural ponds showed highest degree of anthropogenic modification (enrichment factor >10), especially with Se, U, and Pb. Agricultural ponds, previously unknown as a metal hotspot, had the most deteriorated sediment quality as determined by high pollution load index (>1) and contamination factor (>6) for Cd and U. Principal component analysis comparing land use land cover distribution surrounding the aquatic systems to metal concentrations confirmed that agriculture-related land activities correlated well with majority of the metals. Overall, compared to agricultural ponds and coastal regions, sediments in river, swamp and man-made reservoir systems contained relatively fewer metal pollutants, the former two serving as collection points for metal-laden fertilizers and chemicals. The research provides key insights into simultaneously comparing metal accumulation in multiple water bodies and is useful to test and develop effective sediment quality guidelines.

Low mercury, cadmium and lead concentrations in tuna products from the eastern Pacific

Tuna species: Skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) are mainly processed into canned products (loins, solid pack, flakes) either in water or oil, and pre-cooked frozen loins. The National Institute of Fisheries of Ecuador (ISO/IEC 17025 certified), which is the official control laboratory, samples and analyses production batches of companies exporting to the European Union in order to ensure the quality control of Ecuadorean tuna product. From 2009 to 2016, 2572 samples have been analysed (by standard methods) for mercury, cadmium, and lead. The averages were 0.24 ± 0.14; 0.03 ± 0.03 and 0.05 ± 0.05 mg kg-1 (wet weight) respectively; which are well below the norms; i.e., total mercury: 1 mg kg-1; Lead: 0.3 mg kg-1 and Cadmium: 0.1 mg kg-1 according to the EU maximum limits. Over time mercury levels in the sample seemed to decrease but for cadmium and lead no clear pattern was observed. Additionally; samples of tuna can products taken at random from local vendor stores gave concentrations of: Mercury: 0.043 ± 0.004 mg kg-1; Cadmium: 0.012 ± 0.002 mg kg-1; Lead: below detection limit (0.01 mg kg-1). There were a few cases (15 out of 2572: 0.58%) of samples with readings near or just over-limit concentrations; of these, 12 corresponded to Cd, two to Pb and one to Hg. Some of them can be considered statistical outliers as well as cross contamination during analytical procedures. Raw tuna samples have given similar or lower concentrations. No significant statistical correlation was found between Hg, Cd and Pb values, this would suggest that the bioaccumulation of each metal is independent of each other. Literature reports that surface dissolved Hg, Cd, and Pb in the eastern Pacific are in the range of 2-18 ng kg-1. Assuming suggested bioaccumulation of 2-6 times, the end concentration in the tuna would be 0.012-0.042; 0.036-0.108 and 0.010-0.027 μg kg-1 of Hg, Cd, and Pb respectively, that would be one order (or more) below the safe consumption limit. Most, if not all the tuna processed in Ecuador is captured in the eastern Pacific and within its EEZ. Ecuadorian canned tuna complies with stringent standards for presence of these metals; therefore, it can be considered safe to be consumed from the point of view of these metal concentrations. However, further studies should assess metal concentrations exclusively from Ecuadorian tuna captured close to coastal and insular areas.

Modeling total maximum allocated loads for heavy metals in Jinzhou Bay, China

With the recent development of society and economy in the cities of Huludao and Jinzhou, Liaoning Province, China, environment and ecosystem problems have become increasingly serious in Jinzhou Bay, China, because of the increasing amount of heavy metal pollutants being discharged. To solve these problems, a water quality model of heavy metals coupled with a 3D hydrodynamic model is constructed to estimate the environmental capacity (EC) and total maximum allocated loads (TMALs) for Zn and Cd of three river catchments in Jinzhou Bay. According to the model, the ECs for Zn and Cd are approximately 17 and 8 tons per month, respectively, if the criterion obtained from HC5 values (fifth percentile of the SSD) is set as the control criterion (8.24 μg/L for Zn and 3.83 μg/L for Cd) in Jinzhou Bay, and the TMALs of the three river catchments are 4 and 1.7 tons per month.

Distribution of heavy metals in the dissolved and suspended phase of the sea-surface microlayer, seawater column and in sediments of Singapore's coastal environment

Concentrations of heavy metals were determined in the water column (including the sea-surface microlayer, subsurface, mid-depth and bottom water) and sediments from Singapore's coastal environment. The concentration ranges for As, Cd, Cr, Cu, Ni, Pb and Zn in the seawater dissolved phase (DP) were 0.34-2.04, 0.013-0.109, 0.07-0.35, 0.23-1.16, 0.28-0.78, 0.009-0.062 and 0.97-3.66 microg L(-1) respectively. The ranges for Cd, Cr, Cu, Ni, Pb and Zn in the suspended particulate matter (SPM) were 0.16-0.73, 6.72-53.93, 12.87-118.29, 4.34-60.71, 1.10-6.08 and 43.09-370.49 microg g(-1), respectively. Heavy metal concentrations in sediments ranged between 0.054-0.217, 37.48-50.52, 6.30-21.01, 13.27-26.59, 24.14-37.28 and 48.20-62.36 microg g(-1) for Cd, Cr, Cu, Ni, Pb and Zn, respectively. The lowest concentrations of metals in the DP and SPM were most frequently found in the subsurface water while the highest concentrations were mostly observed in the SML and bottom water. Overall, heavy metals in both the dissolved and particulate fractions have depth profiles that show a decreasing trend of concentrations from the subsurface to the bottom water, indicating that the prevalence of metals is linked to the marine biological cycle. In comparison to data from Greece, Malaysia and USA, the levels of metals in the DP are considered to be low in Singapore. Higher concentrations of particulate metals were reported for the Northern Adriatic Sea and the Rhine/Meuse estuary in the Netherlands compared to values reported in this study. The marine sediments in Singapore are not heavily contaminated when compared to metal levels in marine sediments from other countries such as Thailand, Japan, Korea, Spain and China.

Trace metals in Antarctic copepods from the Weddell Sea (Antarctica)

The concentrations of Cd, Co, Cu, Ni, Pb and Zn were determined in the Antarctic copepods Rhincalanus gigas (Brady, 1883), Calanus propinquus (Brady, 1883), Calanoides acutus (Giesbrecht, 1902), Metridia curticauda (Giesbrecht, 1889) and Metridia gerlachei (Giesbrecht, 1902). Samples were taken at seven different stations between 18.01.1999 and 19.02.1999. Metal concentrations in biological tissue were determined by graphite furnace atomic absorption spectroscopy (GFAAS) with Zeeman background correction and by flame AAS (air-acetylene) with deuterium background correction. We found high mean Cd concentrations in the Metridia species of about 10 microg Cd g(-1) and 3-6 microg Cd g(-1) in the other copepods. Co and Pb concentrations were low in all species investigated (<0.1 microg Co g(-1) and <1 microg Pb g(-1)). Zn concentrations were high in M. gerlachei and R. gigas (518 and 430 microg Zn g(-1)). In comparison to copepods from Arctic Seas (Fram Strait, Greenland Sea) and the North Sea, Cd and Cu concentrations appear higher in Antarctic copepods, while Ni and Pb concentrations are similar in both polar regions and Pb concentrations are higher in the North Sea. Variability between species and different regions are discussed.

Cadmium detoxification processes in the digestive gland of cephalopods in relation to accumulated cadmium concentrations

The high concentrations of cadmium recorded in the digestive gland of cephalopods from various temperate and subpolar waters suggest that these molluscs have developed efficient cadmium detoxification mechanisms. The subcellular distribution of cadmium in the digestive gland cells was investigated in seven cephalopod species from the Bay of Biscay (France) and the Faroe Islands. In most species, cadmium was mainly found in the cytosolic fraction of the digestive gland cells, reaching up to 86% of the total cadmium for the squid Loligo vulgaris from the Bay of Biscay. But species with the highest total level of cadmium showed a higher percentage of cadmium associated to insoluble compounds. The quantification of metallothioneins (MTs) by the polarographic method was performed in order to evaluate the involvement of these proteins in the detoxification of the high amounts of bioaccumulated cadmium. Metallothionein levels in cephalopods ranged form 742 +/- 270 to 3478 +/- 1572 microg/g wet weight. No relationship could be established between total cadmium, cytosolic cadmium and MT levels suggesting the occurrence of other Cd-binding ligands. Although these proteins have not been characterised, as cadmium in the digestive gland of cephalopods is mainly associated with soluble ligands, a high potential transfer to predators can be predicted.

The speciation of dissolved copper, cadmium and zinc in Manila Bay, Philippines

At present, there is a very limited information on the levels and distribution of dissolved metals in Manila Bay. In this study, the horizontal and vertical distribution of operationally defined species (labile, bound and total) of dissolved copper (Cu), cadmium (Cd) and zinc (Zn) were determined using differential pulse anodic and cathodic stripping voltammetry in water samples obtained from 18 stations in November 1998. In addition, the 24-h variability in the concentrations of these species at different depths in the water column was determined. These measurements were complemented by the determination of temperature, salinity, dissolved oxygen, chlorophyll a, particulate organic carbon and nutrients. Results showed that more than 50% of total dissolved copper and cadmium were labile while 50% of total dissolved zinc was organically bound. Vertical profiles showed that Cu, Cd and Zn concentrations were generally high at the surface. Zinc and cadmium were characterised by the presence of a mid-depth minimum while copper did not show any clear vertical trend. Dissolved Cu concentrations during the spatial and diurnal samplings ranged from 0.32 to 6.95 nM and 1.52 to 45.65 nM, respectively. For Cd, the concentrations in 18 stations ranged from 0.05 to 2.92 nM, and from 0.03 to 2.42 nM over a 24-h period. Zn concentrations ranged from 2.48 to 147.43 nM and 2.87 to 88.27 nM during the spatial and diurnal samplings, respectively. The large variation in the concentration of Cu, Cd and Zn in the bay was observed to be associated with the presence of a large vertical density gradient in the water column, which appeared to limit the exchange of materials between the surface and bottom waters. Elevated levels of these metals near point sources suggest anthropogenic inputs in the bay.

Heavy metals in fish from the Barents Sea (summer 1994)

To assess the significance of metals in biota of the Barents Sea, preliminary information is presented for the concentrations of Cd, Pb, Hg, Ni, Cu and Zn in liver and muscle tissues of 15 marine fish species collected in the summer of 1994. Lead and Ni concentrations are below limits of detection (< 0.3 and 1.0 mg kg-1 dry wt.) in all tissues, as is Cd in muscle (< 0.10 mg kg-1). Generally, most of our results are within the reported literature range for various Arctic marine systems, especially regarding some commercially important species like cod and redfish, indicating that metal levels are not elevated. However, the interspecific variability is substantial and some remarkably high Cd levels (2.4 and 8.1 mg kg-1 dry wt.) in livers of Anarhichas species (catfish) and Raja fyllae (round skate) point to the problem of a general 'cadmium-anomaly' in polar marine waters, previously inferred from reported results for various pelagic and benthic invertebrates.

The influence of inputs to the Firth of Forth on the concentrations of trace metals in coastal waters

The distribution of copper, lead and cadmium in dissolved and particulate phases has been investigated in the Firth of Forth, Scotland, an embayment of the North Sea. The effect of riverine and anthropogenic trace metal inputs on concentrations in the Firth of Forth and adjacent North Sea is examined. For the dissolved phase the effect of such inputs is confined to the immediate area of discharge. Concentrations in the outer Firth are indistinguishable from those in coastal waters of the North Sea, ca. Cu, 0.2 microgdm(-3) (3.1nm); Pb, 0.025 microgdm(-3) (0.12nm) and Cd, 0.020 microgdm(-3) (0.18nm). There is evidence that particulates enhanced in trace metals, relative to bottom sediments, are leaving the Forth and entering the North Sea. Predictions of the total metal concentrations in the waters of the inner Firth, based on riverine, industrial and sewage associated inputs, show reasonable agreement with observed values.