The presence of plastic debris in the ocean is increasing and several effects in the marine environment have been reported. A great number of studies have demonstrated that microplastics (MPs) adsorb ...organic compounds concentrating them several orders of magnitude than the levels found in their surrounding environment, therefore they could be potential vectors of these contaminants to biota. However, a consensus on MPs as vectors of persistent organic pollutants (POPs) has not been reached since are opposing views among different researchers on this topic. However, all agree that more extensive studies are needed to clarify this relationship. This review reunites information reporting the factors that drive the sorption dynamics between MPs and POPs, which essentially corresponds to polymer properties and surrounding environmental variables. Furthermore, this review highlights several supporting and rebuttal arguments in the direction to clear up the real hazard enforced by the presence of MPs in marine environments.
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•Overview of literature on translocation and accumulation of POPs to marine organisms through MPs.•Comparison of contradictory results on MPs as vectors of persistent organic compounds (POPs).•Critical evaluation of the hazard associated with MPs and adsorbed POPs in marine environments.
During recent years, several eutrophication processes and subsequent environmental crises have occurred in Mar Menor, the largest hypersaline coastal lagoon in the Western Mediterranean Sea. In this ...study, the Landsat-8 and Sentinel-2 satellites are jointly used to examine the evolution of the main water quality descriptors during the latest ecological crisis in 2021, resulting in an important loss of benthic vegetation and unusual mortality events affecting different aquatic species. Several field campaigns were carried out in March, July, August, and November 2021 to measure water quality variables over 10 control points. The validation of satellite biogeochemical variables against on-site measurements indicates precise results of the water quality algorithms with median errors of 0.41 mg/m3 and 2.04 FNU for chlorophyll-a and turbidity, respectively. The satellite preprocessing scheme shows consistent performance for both satellites; therefore, using them in tandem can improve mapping strategies. The findings demonstrate the suitability of the methodology to capture the spatiotemporal distribution of turbidity and chlorophyll-a concentration at 10–30 m spatial resolution on a systematic basis and in a cost-effective way. The multitemporal products allow the identification of the main critical areas close to the mouth of the Albujon watercourse and the beginning of the eutrophication process with chlorophyll-a concentration above 3 mg/m3. These innovative tools can support decision makers in improving current monitoring strategies as early warning systems for timely assistance during these ecological disasters, thus preventing detrimental conditions in the lagoon.
Tobacco is a well-documented threat to human health. However, its environmental impact has only recently been considered. Metals can interact with cigarette butts (CBs) being transported in the ...marine environment and reaching organisms. To understand this mechanism, a series of metal(loid)s were analyzed in cigarette filters (virgin, artificially smoked, leached in seawater and aged in beach and harbour) as well as in artificially contaminated oyster tissues. Smoked filters showed higher levels of metals compared to the virgin ones showing enrichment factors up to 90, probably associated with tobacco metal content. Once the CBs are delivered to the environment, metals can be leached to seawater until reaching equilibrium, which may be dependent on initial metal levels in the water. Copper was the element with the highest percentage of desorption (91 ± 3%) while strontium showed the lowest percentage (40 ± 0%). CBs revealed a great capacity to accumulate metals from the environment when weathered in contaminated areas. A chemical impact derived from CBs contamination might exist as they serve as a carrier for metals in the marine environment. The release of metals from CBs or the ingestion of metal loaded CBs may pose a toxicological risk for marine organisms via accumulation in their tissues.
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•-Cigarette butts (CB) are enriched in metals after being smoked.•CB can release/adsorb metals depending on the contamination degree of the environment.•Metals adsorbed to CB can be released to seawater if transported to pristine waters.•No bioaccumulation was observed in oysters from smoked CB.•Beach or harbour aged CB have a potential risk of accumulation.
The levels of metals in the waters of the Mar Menor lagoon are higher in the southern than in the northern zone both in the dissolved (As: 1.78 μg L-1 north vs 1.86 μg L-1 south; Cd: 0.020 μg L-1 vs ...0.055 μg L-1; Pb: 0. 686 μg L-1 vs 2.714 μg L-1; Zn: 3.06 μg L-1 vs 10.2 μg L-1) as in the particulate fraction (As: 13.6 μg g-1 north vs 27.3 μg g-1 south; Cd: 0.510 μg g-1 vs 2.11 μg g-1; Pb: 146 μg g-1 vs 575 μg g-1; Zn: 266 μg g-1 vs 729 μg g-1). This difference is associated to the influence of historical and recent inputs from the Sierra Minera Cartagena -La Unión located south of the lagoon. Strong winds cause sediment resuspension in this shallow lagoon, increasing metal levels in the dissolved (twofold) and especially in the particulate fraction (threefold) because the resuspended sediments are rich in metals. Distribution among dissolved and particulate fraction is determined by the chemistry of each element and salinity. This increase causes the levels to reach limits very close to those established by the Water Framework Directive, especially in the case of lead, whose annual average level of 1.23 μg L-1 is very close to the 1.3 μg L-1 established in the Directive. Therefore, slight change in environmental variables could make Pb levels to exceed legal limits. Future work should focus on investigating how unique environmental events, enhanced by global change, affect metal cycles in highly anthropised coastal areas.
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•Hg adsorption/desorption modelled by pseudo-first and -second order models.•Faster Hg adsorption/desorption (by volume) observed for microalgae than for MP.•Hg bound to MP promoted ...Hg uptake but also facilitated Hg elimination in mussel.•Mussel accumulated less Hg when exposed via MP than via microalgae or waterborne.
The adsorption and desorption of Hg onto and from microplastics (MP) and microalgae (MA) were investigated, and fitted using pseudo-first-order and pseudo-second order kinetics models. Then, the potential role of MP as vector for the entrance and accumulation of Hg (MP-Hg) in comparison to natural pathways (via MA -MA-Hg-, and dissolved -WB-Hg-) was investigated in mussel. Mussels were exposed to a single dose of Hg (2375 ng ind−1) for 4 h. Although the clearance of MP-Hg was relevant (82 %), it was lower than that of MA (95 %) and MA-Hg (94 %). The amount of the Hg accumulated and eliminated was higher in mussels exposed to MP-Hg (1417 ng Hg) than in those exposed to MA-Hg (882 ng Hg) and WB-Hg (1074 ng Hg). However, Hg accumulation was similar in the three mussel groups (≈800 ng Hg). This was related to the fast elimination of Hg still attached to MP by MP-Hg mussels. Hg was mainly accumulated in digestive gland in MA-Hg and MP-Hg mussels, and in gills in WB-Hg mussels. Overall, the results indicated that MP facilitated the entrance of Hg in mussel but also promoted Hg elimination, which could limit the toxicological risk of Hg adsorbed onto MP.
The present study reports the levels and trends (1993–2013) of DDTs, PCBs and metals in mussels collected at two coastal sites influenced by the River Ebro discharges. Results showed that levels of ...PCBs, DDTs, Cd and Hg were related to water inputs from the river, while these did not seem to be the main source for the Pb, Zn, Cu and As levels observed. Significant relationships were observed between PCBs and DDTs levels and the river flowrate in the fast-flowing months, suggesting that overflow periods promoted the mobilization of contaminants from sediments, and their subsequent discharge and spreading across the sea. Results indicated that PCBs were effectively southwestern transported, probably in relation to their soluble behavior in stream waters, while DDTs were limitedly spread in seawater, likely due to their particulate behavior. Significant declining trends observed for some metals, PCBs and p,p’ DDE may reflect the reduction of pollutants inputs along the river basin. However, the results also showed significant relationships between the river's flowrate in the fast-flowing months and PCBs and DDTs levels, and significant decreases on the river flowrate in some fast-flowing months during the long-term series studies. Both facts suggested that the reduction on overflow periods influenced the decreasing pollutants trends observed in mussels. The present study advises that decreasing trends in contaminant levels in Mediterranean estuarine coastal areas may be related not only to successful remediation works/policies, but also to the fluctuations on the hydrological regime of the rivers, which are directly linked to current climatic trends.
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•Mussels act as integration bio-monitors of the river pollutants inputs to the sea.•Some metals, PCBs and p,p’ DDE declined (1993-2013) in the River Ebro coastal area.•In months of fast flows, contaminants were mobilized from river sediments to the sea.•Pollutants' decrease may be partially related to the decrease of the river flowrate.•Declines in river flowrate due to climatic change may influence sea pollutants trends.
A new analytical protocol for the challenging analysis of total dissolved iron at the low picomolar level in oceanic waters suitable for onboard analysis is presented. The method is based on the ...revision of the adsorptive properties of the iron/2,3-dihydroxynaphthalene (Fe/DHN) complexes on the hanging mercury drop electrode with catalytic enhancement by bromate ions. Although it was based on a previously proposed reagent combination, we show here that the addition of an acidification/alkalinization step is essential in order to cancel any organic complexation, and that an extra increment of the pH to 8.6–8.8 leads to the definition of a preconcentration-free procedure with the lowest detection limit described up to now. For total dissolved iron analysis, samples were acidified to pH 2.0 in the presence of 30 μM DHN and left to equilibrate overnight. A 10 mL sample was subsequently buffered to a pH of ∼8.7 in the presence of 20 mM bromate: a 60 s deposition at 0 V led to a sensitivity of 34 nA nM–1 min–1, a 4-fold improvement over previous methods, that translated in a limit of detection of 5 pM (2–20 fold improvement). Several tests proved that a nonreversible reaction in the time scale of the analysis, triggered by the acidification/alkalinization step, was behind the signal magnification. The new method was validated onboard via the analysis of reference material and via intercalibration against flow injection analysis-chemiluminescence on Southern Ocean surface samples.
The queen scallop Aequipecten opercularis accumulates high concentrations of lead (Pb) in its tissues, what has led to the interruption of this fishery in some extraction areas in Galicia (NW Spain). ...This study follows the dynamics of bioaccumulation of Pb and other metals in this species, the tissue distribution and the subcellular partitioning in selected organs, in order to understand the mechanisms that provoke the high Pb levels reached in its tissues and to increase our knowledge about metal bioaccumulation dynamics in this species. Scallops originating from a clean area were exposed in cages in two places in the Ría de Vigo (one shipyard and a less impacted location) and 10 individuals were collected every month over a three months period. Metal bioaccumulation and metal distribution in several organs, including gills, digestive gland, kidneys, muscle, gonad and remaining tissues, was studied. The results showed that scallops accumulated similar levels of Cd, Pb and Zn at both sites, while Cu and Ni showed an opposite pattern at the shipyard, with Cu concentrations increasing around 10 times and Ni decreasing during the 3 months of exposure. The preferential organs for metal accumulation were the kidneys for Pb and Zn, the digestive gland for Cd, both organs for Cu and Ni, and the muscle for As. Subcellular partitioning of kidney samples additionally showed an extraordinary ability to accumulate Pb and Zn at very high concentrations in kidney granules, a fraction that accounted for 30 to 60 % of Pb in soft-tissues. It is concluded that Pb bioaccumulation in kidney granules is the mechanism responsible for the high levels of Pb observed in this species.
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•Queen scallops present numerous small intracellular granules in their kidneys.•Kidney granules accumulate Pb and Zn at very high concentrations.•Pb in kidney granules represents up to 60 % of Pb body burden.•The digestive gland contains the majority of Cd in organic fractions.•Pb concentrations in queen scallops reach very high levels even in unpolluted places.
The speciation and bioavailability of copper (Cu) in the marine environment are affected by the presence of dissolved organic matter (DOM). Previous studies conducted at dissolved Cu concentrations ...>100 nM confirmed that Cu bioavailability depends on the concentration of labile Cu, as measured by anodic stripping voltammetry (ASV), which aligns with the expectations of the biotic ligand model (BLM). However, ambient Cu concentrations in coastal waters are generally lower, ranging between 1 and 80 nM, and the effect of DOM on the bioavailability of Cu to marine organisms has not been tested within that range of Cu concentrations. The present study aims to assess the impact of two types of DOM, a commercially available fulvic acid, and marine DOM extracted by ultrafiltration, on Cu bioavailability to phytoplankton using short-term
Cu internalisation by the marine dinoflagellate Prorocentrum micans. Results showed that Cu internalisation decreases with DOM additions as expected according to the BLM and in agreement with ASV measurements of labile Cu, at the highest tested Cu concentration (100 nM). On the contrary, at a lower Cu concentration (20 nM), organic complexes appear to be partially bioavailable, thereby challenging the general applicability of the BLM model at environmentally relevant concentrations in coastal areas.
The determination of trace elements using stripping voltammetry may be seriously affected by the presence of intensive matrix background or interfering peaks, leading to poorer detection limits ...and/or inaccurate quantitative results. In this work, we have tested the use of signal transformation (e.g., second derivative) in the analysis of platinum in seawater and sediment digests by means of catalytic adsorptive stripping voltammetry. In natural waters, the limit of detection of Pt is affected by a broad background wave due to the formazone complex used in the sample matrix for its determination, while in sediment digests, the Pt peak may be interfered with due to the presence of elevated concentrations of Zn, affecting the accuracy of the determination. Results applying second derivative signal transformation revealed a significant improvement (2–3-fold) of the detection limit in water due to the minimization of background effects, therefore allowing shorter accumulation times and faster determinations. In the presence of interfering peaks, the inaccuracy resulting from erroneous baseline selection in the original signal is eliminated when the second derivative is used. Signal processing should be considered as a useful tool for other voltammetric methodologies where more accurate or faster determinations are needed.
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