Speciation studies of copper in the Gulf of Elefsis: The role of the macroalgae Ulva rigida

The Gulf of Elefsis, situated in the vicinity of Athens, is a high productivity area regarding the biota. One of the most abundant algae existing there is Ulva rigida. Controlled laboratory simulation experiments, as well as field investigations indicated that copper is complexed to a high extent with organic substances released by U. rigida and other naturally occurring organic ligands. A significant part of these organic ligands exhibit surface active properties, i.e. the accumulation on different phase boundaries (e.g. seawater/atmosphere, seawater/living organisms, seawater/particulate suspended matter, seawater/sediments). The complexing capacity values of samples collected from different microenvironments within the Gulf of Elefsis, determined by the electrochemical method of differential pulse anodic stripping voltammetry (DPASV), vary between 0.04 and 0.43 μM Cu2+. At the same time, the complexing capacities of samples obtained from the laboratory tanks in which U. rigida has been placed in order to be decomposed under controlled conditions, show much higher complexing capacity values (up to 13 μM Cu2+), especially during the final stage of the experiment. The method of linear sweep voltammetry (LSV) was applied for the determination of the concentration of sulfur species (S0+S2-) present in nonaerated tanks containing U. rigida. The total concentration of sulfur species in tank No. 2 was 300 nM while in tank No. 3 it was 500 nM. As a result of the presence of sulfur species, a part of the complexing capacity of the substances released during algae biomass decomposition in these two tanks could be attributed to the formation of copper sulfides. Furthermore, the surfactant activity (amount of surface active substances (SAS) expressed in equivalents of the nonionic surfactant Triton-X-100) was determined by A.C. out of phase voltammetry. Higher amounts of SAS were detected in the tanks containing U. rigida (up to 0.70 mg/l eq. T-X-100), in comparison to samples originating from natural microenvironments which had values ranging between 0.10 and 0.17 mg/l eq. T-X-100. These results show that U. rigida, although definitely not the only or necessarily the major contributor to the organic ligand pool in the study area, contributes considerably to the production of ligands with high metal complexing capacity and/or high surfactant activity. © 2004 Elsevier B.V. All rights reserved

Trace metals pollution of waters and soils in Kardjali region, Bulgaria

Trace metals pollution of surface waters and their nearby soils in the metallurgically polluted Kardjali region, Bulgaria, were studied. Thermodynamic modeling including the dissolved organic carbon (DOC) was carried out for evaluating the distribution of metal species in waters and soil solutions. Zn was found to be the most widespread pollutant in the water samples, followed by Cu, Mn, and Cd. Geoaccumulation indices of trace metals for the tested soils were calculated, indicating that regarding Al, Fe, Co, Ni, and Cu all soils are “uncontaminated”. The most significant soil pollutant was found to be Cd, with all soils being either “extremely contaminated” by this metal or close to the limit, followed by Pb and Zn. The dynamics of trace metal chemical species distribution in surface waters and in the water-soluble soil fractions, as a result of possible spontaneous precipitations, was calculated by applying different thermodynamic models. Regarding Mn, Co, Ni, and Cd in waters and aqueous soil extracts and Zn in aqueous soil extracts, their free ion species prevailed, being more labile and hence toxic for the ecosystem. In the case of Al, Fe, Cu, Cd, and Pb in the waters and aqueous soil extracts and of Zn in waters, stable organic complexes with bidentate bonds, Me(OH)4 − or Me(OH)0 2 prevailed. © 2018, Springer International Publishing AG, part of Springer Nature

Cadmium and lead in organically produced foodstuffs from the Greek market

Determinations of cadmium and lead content in a wide variety of organically produced foodstuffs available in the Greek market were carried out in the present study. The mean values detected ranged from non detectable to 53.4 ng g-1 and 65.0 ng g-1 for cadmium and lead, respectively. The highest cadmium concentrations were observed in the food categories of cereals (21.7 ng g-1), followed by leafy vegetables (15.4 ng g-1), whereas for lead the highest concentrations were found in leafy vegetables (33.4 ng g-1), followed by pulses (21.4 ng g-1) and alcoholic beverages (20.0 ng g-1). The comparison of the two metals' content in certified organically grown foodstuffs to that of conventional ones from the Greek market demonstrates that cadmium and lead concentrations are higher in conventional foodstuffs in a percentage equal to 64% and 61% of the products compared, respectively. The results also show that "uncertified" organic products contained far larger concentrations of cadmium and lead than either the certified organic or conventional foodstuffs. These results demonstrate that although the majority of certified organic products may have lower metal content, organic agriculture as such does not necessarily reduce the cadmium and lead content of organically cultivated products, unless additional provisions are observed. © 2007 Elsevier Ltd. All rights reserved

Assessment of copper, cadmium and zinc remobilization in Mediterranean marine coastal sediments

The remobilization of copper, cadmium and zinc in sediments of three selected coastal microenvironments of the Aegean Sea (Eastern Mediterranean) is assessed. Various analytical methods and techniques were employed providing concentrations, profiles and forms of metals and organic matter in sediments and pore waters. At Loutropyrgos, a non-industrial site located, however, within an intensively industrialized enclosed gulf, an intense resupply of zinc in pore water from sediment was recorded, correlating with the highest value of weakly bound fraction of zinc determined at this area. The comparatively high zinc concentrations measured in the pore waters (394 nM), exceed considerably those in the overlying seawater (12.5 nM determined by DGT; 13.5 nM total), resulting in the formation of a strong concentration gradient at the sediment-water interface. Potential zinc flux at the sediment-water interface at Loutropyrgos (based on 0.4 mm DGT profile) was calculated equal to 0.8 mmol.m-2d-1. The half lives of trace metals at Loutropyrgos site, based on the aforementioned DGT profiles, amount to 0.1 y (Zn), 2.8 y (Cd), 4.5 y (Cu), 2.2 y (Mn) and 0.4 y (Fe) pointing out to the reactivity of these metals at the sediment-water interface.The concentration of dissolved organic carbon (DOC) in pore waters of the three selected sites (2.7-5.2 mg/L) was up to four times higher compared to that of the corresponding overlying seawater. Similarly, the concentrations of carbohydrates in pore waters (0.20-0.91 mg/L monosaccharides; 0.71-1.6 mg/L polysaccharides) are an order of magnitude higher than those of seawater, forming a concentration gradient at the sediment-water interface. Total carbohydrates contribute between 34 and 48% of the organic carbon of the pore waters, being significantly higher than those of seawater from the corresponding areas, which were in the range of 15-21%.The complexing capacity as for copper ions (CCu) determined in pore water ranges widely, from 0.03 μM at Kalamos to 3.76 μM at Molos, whereas the corresponding values for cadmium ions (CCd) were non detectable, except for Kalamos site, where the value for CCd was equal to 0.03 μM. A significant increase in the values of CCu, normalized as for DOC, was observed in pore waters in relation to those of overlying seawater. This indicates an 'enrichment' of pore waters in dissolved organic ligands for copper ions per unit of DOC. Up to 72% of DOC could be present as ligands capable to complex copper ions. © 2010 Elsevier Ltd

Partitioning and distribution of dissolved copper, cadmium and organic matter in Mediterranean marine coastal areas: The case of a mucilage event

Dissolved copper and cadmium partitioning and their interaction with organic matter were investigated in shallow coastal areas of the Aegean Sea (Eastern Mediterranean). The percentage of DGT-labile copper as for total dissolved copper ranged from 13 to 34% during summer and from 23 to 36% during winter, whereas the corresponding percentage for DGT-labile cadmium was higher in summer (38-68%), in comparison to winter (29-44%). The CCu was found to be 100-260 nM during summer while in winter the range was 42-430 nM. The corresponding CCd reached 27 and 45 nM, respectively. The mean TEP value in summer was high (208 μg/L xanthan equiv.), while in winter it reached 441 μg/L xanthan equiv., which indicates significant phytoplankton activity in winter, a feature occasionally observed in the stratified study areas after the breaking down of the thermocline/pycnocline, followed by consequent nutrient enrichment of the surface layers by nutrients accumulated in the sea bottom. A significant fraction of dissolved organic carbon (DOC) exhibited surface active properties and was determined as surface active substances (SAS) in mg/L eq. of nonionic surfactant Triton-X-100. Carbohydrates were also determined and they represented up to 33% of the DOC. © 2005 Elsevier Ltd. All rights reserved

Trace metals in the marine surface microlayer of coastal areas in the Aegean sea, Eastern Mediterranean

Concentrations of 10 trace metals were determined seasonally in the sea surface microlayer (SML) and sub-surface water (SSW) at coastal areas of the Aegean sea comprising different morphological characteristics and degrees of pollution. Metal concentrations varied broadly, specifically in the SML, being typical of coastal areas subject to intense anthropogenic pressures. The mean enrichment factors (EFs) for dissolved metals range from 1.7 (for V) to 3.6 (Zn), being lower than the corresponding calculated for suspended particulate metals ranging from 2.4 (Cd) to 17 (Cr). A statistically significant enrichment of the SML (greater than unity) was obtained for dissolved metals following the decreasing order Ζn, Cu, Mn, Pb, Fe, Co, Cr, Ni, however not for Cd and V, and in the suspended particulate matter for Cr, Cu, Pb, Ni, V, Zn, Cd, Mn, while not for Fe. Surface microlayer enrichment in metals is governed by complex physicochemical and biological processes, occurring in coastal areas, among which the continuous precipitation of atmospheric particles onto the sea surface and the processes of metals dissolution and partitioning. Correlations among the trace metals examined, the sites sampled and the factor of seasonality are also discussed. © 2021 Elsevier Lt

Bioaccumulation of metals (Cd, Cu, Zn) by the marine bivalves M. galloprovincialis, P. radiata, V. verrucosa and C. chione in Mediterranean coastal microenvironments: Association with metal bioavailability

The concentrations of Cd, Cu and Zn in both the whole soft tissue and separate organs (gills, mantle, muscle and digestive gland) of wild bivalves (Mytilus galloprovincialis, Pinctada radiata, Venus verrucosa and Callista chione) from three different coastal microenvironments of Greece were monitored from 2003 to 2004. In parallel, by employing appropriate analytical protocols for metal partitioning, the labile fraction of the metals was determined in the dissolved phase, suspended particulate matter and sediments. Differences in the metal levels were detected both among the study areas as well as among the bivalves examined. Significant bioaccumulation was demonstrated regarding Zn in M. galloprovincialis specimens from the highly industrialized Gulf of Elefsis and Cd in P. radiata and V. verrucosa from the Maliakos Gulf, which is influenced by extended agricultural activity occurring at the neighbouring area and a river outflow. Data of the metal levels in the various environmental phases were correlated with their concentrations in bivalves' tissues. The clear relationships obtained in many cases among the labile metal concentrations and the bioaccumulated concentrations in bivalves point out that the labile fraction of a metal is the most bioavailable. The lack of positive correlation for C. chione confirms the occurrence of effective mechanisms of internal regulation of metal concentrations. © 2012 Springer Science+Business Media B.V