Seasonal and multi-decadal zinc isotope variations in blue mussels from two sites with contrasting zinc contamination levels

Zinc (Zn) isotope compositions in soft mussel tissues help identify internal biological processes and track coastal Zn sources in coastal environments, thus aiding in managing marine metal pollution. This study investigated the seasonal and multi-decadal Zn isotope compositions of blue mussels (genus Mytilus) from two French coastal sites with contrasting Zn environmental contamination. Concurrently, we characterized the isotope ratios of sediments and plankton samples at each site to understand the associations between organisms and abiotic compartments. Our primary objective was to determine whether these isotope compositions trace long-term anthropogenic emission patterns or if they reflect short-term biological processes. The multi-decadal isotope profiles of mussels in the Loire Estuary and Toulon Bay showed no isotope variations, implying the enduring stability of the relative contributions of natural and anthropogenic Zn sources over time. At seasonal scales, Zn isotope ratios were also constant; hence, isotope effects related to spawning and body growth were not discernible. The multi-compartmental analysis between the sites revealed that Toulon Bay exhibits a remarkably lower Zn isotope ratio across all studied matrices, suggesting the upward transfer of anthropogenic Zn in the food web. In contrast, the Zn isotope variability observed for sediments and organisms from the Loire Estuary fell within the natural baseline of this element. In both sites, adsorptive geogenic material carrying significant amounts of Zn masks the biological isotope signature of plankton, making it difficult to determine whether the Zn isotope ratio in mussels solely reflects the planktonic diet or if it is further modified by biological homeostasis. In summary, Zn isotope ratios in mussels offer promising avenues for delineating source-specific isotope signatures, contingent upon a comprehensive understanding of the isotope fractionation processes associated with the trophic transfer of this element through the plankton.

Vanishing lead in the Loire River estuary: An example of successful environmental regulation

The behavior, and history of lead (Pb) contamination in the ecosystem of the Loire estuary was examined using elemental concentrations and Pb isotope data in water, sediment, bivalves, shrimps, and fish. In the estuary and in the surrounding coastal area, Pb concentrations in water and sediment decreased compared to concentrations determined in the 1980s, with concentrations ranging from 15.8 to 65.7 mg kg-1 in the surface sediment, 0.04-0.26 nM in the water column, and 48.0-77.9 mg kg-1 in suspended particles. Pb biomonitoring using blue mussels collected by the French Mussel Watch Program over the last 40 years showed a concentration decrease from 3.8 to 0.8 mg kg-1. A similar trend is observed in an estuarine sediment core. Changes in accompanying Pb isotope compositions strongly suggest a binary mixing process between Pb derived from terrigenous material and anthropogenic sources. Thus, environmental regulations restricting the release of lead into the environment contribute to a decrease in estuarine levels of this pollutant, which occurs on a decadal time scale.

The French Mussel Watch: More than two decades of chemical contamination survey in Mediterranean coastal waters

Active biomonitoring of chemical contamination (e.g., Cd, Hg, Pb, DDT, PCB, PAH) in French Mediterranean coastal waters has been performed for more than two decades. This study aimed at presenting the current contamination in 2021 and the temporal evolution of concentrations from 2000. Based on a relative spatial comparison, low concentrations were measured in 2021 at most sites (>83 %). Also, several stations with moderate to high levels were highlighted in the vicinity of major urban industrial centers (e.g., Marseille, Toulon) and near river mouths (e.g., Rhône, Var). Over the last 20 years, no major trend was revealed, mostly, especially for the relative high-level sites. This likely constant contamination over time, plus slight increases of metallic elements at a few sites, still raise questions on the efforts that remain to be made. The decreasing trends of organic compounds, in particular PAH, provide evidence of the efficiency of some management actions.

Contamination of planktonic food webs in the Mediterranean Sea: Setting the frame for the MERITE-HIPPOCAMPE oceanographic cruise (spring 2019)

This paper looks at experiential feedback and the technical and scientific challenges tied to the MERITE-HIPPOCAMPE cruise that took place in the Mediterranean Sea in spring 2019. This cruise proposes an innovative approach to investigate the accumulation and transfer of inorganic and organic contaminants within the planktonic food webs. We present detailed information on how the cruise worked, including 1) the cruise track and sampling stations, 2) the overall strategy, based mainly on the collection of plankton, suspended particles and water at the deep chlorophyll maximum, and the separation of these particles and planktonic organisms into various size fractions, as well as the collection of atmospheric deposition, 3) the operations performed and material used at each station, and 4) the sequence of operations and main parameters analysed. The paper also provides the main environmental conditions that were prevailing during the campaign. Lastly, we present the types of articles produced based on work completed by the cruise that are part of this special issue.

Identification and Quantification of Microplastics in the Marine Environment Using the Laser Direct Infrared (LDIR) Technique

Here, we evaluate for the first time the performances of the newly developed laser direct infrared (LDIR) technique and propose an optimization of the initial protocol for marine microplastics (MPs) analysis. Our results show that an 8 μm porosity polycarbonate filter placed on a Kevley slide enables preconcentration and efficient quantification of MPs, as well as polymer and size determination of reference plastic pellets of polypropylene (PP), polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET), with recoveries ranging from 80-100% and negligible blank values for particle sizes ranging from 200 to 500 μm. A spiked experiment using seawater, sediment, mussels, and fish stomach samples showed that the method responded linearly with significant slopes (R² ranging from 0.93-1.0; p < 0.001, p < 0.01). Overall, 11 polymer types were identified with limited handling and an analysis time of ca. 3 h for most samples and 6 h for complex samples. Application of this technique to Mediterranean marine samples (seawater, sediment, fish stomachs and mussels) indicated MP concentrations and size distribution consistent with the literature. A high predominance of PVC (sediment, fish stomachs) and PE and PP (seawater, mussels) was observed in the analyzed samples.

Differences in Copper Isotope Fractionation Between Mussels (Regulators) and Oysters (Hyperaccumulators): Insights from a Ten-Year Biomonitoring Study

Copper (Cu) isotope compositions in bivalve mollusks used in marine-monitoring networks is a promising tool to monitor anthropogenic Cu contamination in coastal and marine ecosystems. To test this new biomonitoring tool, we investigated Cu isotope variations of two bivalves-the oyster Crassostrea gigas and the mussel Mytilus edulis-over 10 years (2009-2018) in a French coastal site contaminated by diffuse Cu anthropogenic sources. Each species displayed temporal concentration profiles consistent with their bioaccumulation mechanisms, that is, the Cu-regulating mussels with almost constant Cu concentrations and the Cu-hyperaccumulating oysters with variable concentrations that track Cu bioavailability trends at the sampling site. The temporal isotope profiles were analogous for both bivalve species, and an overall shift toward positive δ⁶⁵Cu values with the increase of Cu bioavailabilities was associated with anthropogenic Cu inputs. Interestingly, mussels showed wider amplitudes in the isotope variations than oysters, suggesting that each species incorporates Cu isotopes in their tissues at different rates, depending on their bioaccumulation mechanisms and physiological features. This study is the first to demonstrate the potential of Cu isotopes in bivalves to infer Cu bioavailability changes related to anthropogenic inputs of this metal into the marine environment.

Patterns of trace metal bioaccumulation and trophic transfer in a phytoplankton-zooplankton-small pelagic fish marine food web

Trace metal contamination in the European sardine and anchovy food web was investigated in the Gulf of Lions, NW Mediterranean Sea, including seawater and size fractions of plankton. The results highlighted: i) higher and more variable concentrations in the smaller plankton size classes for all metals except cadmium; ii) higher concentrations in anchovy versus sardine for all elements except lead; iii) different patterns of metal bioaccumulation through the food web: cobalt, nickel, copper, silver, lead and zinc displayed continuously decreasing concentrations (with the exception of increased zinc in fish only), while mercury concentrations dropped considerably in larger plankton size classes and rose significantly in fish. Lastly, cadmium concentrations were found to be highest in intermediate plankton size classes, with very low levels in fish. The need to efficiently characterize the biological composition of plankton in order to fully identify its role in the mobilization and transfer of metals was highlighted.

Modified 3D-printed device for mercury determination in waters

3D printing technology is increasingly used in flow analysis, to develop low cost and tailor-made devices. The possibility of grafting specific molecules onto 3D printed parts offers new perspectives for the development of flow systems. In this study, a MPFS system including a dicarboxylate 1,5-diphenyl-3-thiocarbazone grafted 3D-printed device has been developed for mercury determination. For this purpose, the surface of 3D-printed cuboids was first modified with amine functional groups and then grafted with dicarboxylate 1,5-diphenyl-3-thiocarbazone. This new grafted device resulted in selective mercury preconcentration with extraction and elution yields higher than 90% even at high sampling flow rates. The detection can then be carried out in two ways: a direct detection of mercury extracted onto 3D-printed grafted cuboids by atomic absorption spectrophotometry after amalgam on gold or a detection of mercury in solution after elution with l-cysteine by spectrophotometry or cold vapour atomic absorption spectrometry.

Assessment of the metal contamination evolution in the Loire estuary using Cu and Zn stable isotopes and geochemical data in sediments

In this work, a multi-elemental approach combining Cu and Zn stable isotopes is used to assess the metal contamination evolution in the Loire estuary bulk sediments. Elemental geochemical data indicate an increase of metal concentrations from the beginning of the industrial period peaking in the 1990s, followed by an attenuation of metal contamination inputs to the estuary. Zinc isotope compositions suggest a binary mixing process between Zn derived from terrigenous material and multi-urban anthropogenic sources. Copper isotope systematics indicate a single natural dominant source represented by weathered silicate particles from soils and rocks. This work demonstrates the applicability of Zn isotopes to identify anthropogenic Zn sources in coastal systems, even under a low to moderate degree of contamination. Further studies are required to constrain Cu sources and to elucidate possible effects of grain-size and mineralogy in the Cu isotope composition of sediment in the Loire estuary.

Platinum in sediments and mussels from the northwestern Mediterranean coast: Temporal and spatial aspects

Platinum (Pt) is considered a Technology Critical Element (TCE) and an emerging metallic contaminant with increasing release into the environment. Gaps in knowledge and understanding of environmental levels, fate and effects of Pt still exist, especially in the marine environment. This work presents Pt concentrations in the northwestern Mediterranean coast including: (i) temporal variability from sediment cores and farmed mussels in the Toulon Bay (historically affected by intense human activities) and (ii) spatial distribution from recent wild mussels collected along ∼ 700 km coastline with contrasting ecosystems (including natural reserves), quantified using voltammetry and inductively coupled plasma-mass spectrometry. The historical (>100 years) record of Pt in sediments from the Toulon Bay suggests the existence of non-negligible Pt sources older than those related to vehicle emission devices, such as petrol industry and coal-fired activities. A strong Pt increase in more recent sediments (from ∼12 to 16 ng g^-1) and mussels (8-fold increase from ∼0.12 to 0.80 ng g^-1) covering the past 25 years reflect the overall evolution of Pt demand in Europe (∼20-fold increase for vehicle catalysts in 20 years). Spatial biomonitoring of Pt in mussels along the northwestern Mediterranean coast is assumed to reflect inter-site differences of Pt exposure (0.09-0.66 ng g^-1) despite seasonal effect on tissue development. This study highlights the need for thorough and regular monitoring of Pt levels in sediments and biota from urbanized coastal areas in order to better assess the environmental impact of this TCE, including potential risks for marine organisms.

Trace metal concentrations in the muscle of seven marine species: Comparison between the Gulf of Lions (North-West Mediterranean Sea) and the Bay of Biscay (North-East Atlantic Ocean)

Concentrations of 6 trace metals (Ag, Cd, Cu, Ni, Pb, Zn) in the muscle of 2 sharks (Galeus melastomus and Scyliorhinus canicula), 4 teleosts (Helicolenus dactylopterus, Lepidorhombus boscii, Micromesistius poutassou and Phycis blennoides) and 1 crustacean (Nephrops norvegicus) were compared between the Bay of Biscay (Atlantic Ocean) and the Gulf of Lions (Mediterranean Sea). Although average concentrations and the trace element pollution index were generally higher in the Gulf of Lions, significant differences between the two ecosystems were only found for Zn for Helicolenus dactylopterus, and for Ag and Cu for the crustacean N. norvegicus. Moreover, some relationships between trophic level or size and metal concentrations were found for these two species. The absence of clear pattern may result from the blurring effect of contamination and excretion that may act differentially for all species and all elements.

Oligotrophy as a major driver of mercury bioaccumulation in medium-to high-trophic level consumers: A marine ecosystem-comparative study

Mercury (Hg) is a global contaminant of environmental concern. Numerous factors influencing its bioaccumulation in marine organisms have already been described at both individual and species levels (e.g., size or age, habitat, trophic level). However, few studies have compared the trophic characteristics of ecosystems to explain underlying mechanisms of differences in Hg bioaccumulation and biomagnification among food webs and systems. The present study aimed at investigating the potential primary role of the trophic status of systems on Hg bioaccumulation and biomagnification in temperate marine food webs, as shown by their medium-to high-trophic level consumers. It used data from samples collected at the shelf-edge (i.e. offshore organisms) in two contrasted ecosystems: the Bay of Biscay in the North-East Atlantic Ocean and the Gulf of Lion in the North-West Mediterranean Sea. Seven species including crustaceans, sharks and teleost fish, previously analysed for their total mercury (T-Hg) concentrations and their stable carbon and nitrogen isotope compositions, were considered for a meta-analysis. In addition, methylated mercury forms (or methyl-mercury, Me-Hg) were analysed. Mediterranean organisms presented systematically lower sizes than Atlantic ones, and lower δ¹³C and δ¹⁵N values, the latter values especially highlighting the more oligotrophic character of Mediterranean waters. Mediterranean individuals also showed significantly higher T-Hg and Me-Hg concentrations. Conversely, Me-Hg/T-Hg ratios were higher than 85% for all species, and quite similar between systems. Finally, the biomagnification power of Hg was different between systems when considering T-Hg, but not when considering Me-Hg, and was not different between the Hg forms within a given system. Overall, the different parameters showed the crucial role of the low primary productivity and its effects rippling through the compared ecosystems in the higher Hg bioaccumulation seen in organisms from oligotrophic Mediterranean waters.

Carbon and nitrogen elemental and isotopic ratios of filter-feeding bivalves along the French coasts: An assessment of specific, geographic, seasonal and multi-decadal variations

Primary consumers play a key role in coastal ecosystems by transferring organic matter from primary producers to predators. Among them, suspension-feeders, like bivalve molluscs are widely used in trophic web studies. The main goal of this study was to investigate variations of C and N elemental and isotopic ratios in common bivalves (M. edulis, M. galloprovincialis, and C. gigas) at large spatial (i.e. among three coastal regions) and different temporal (i.e. from seasonal to multi-decadal) scales in France, in order to identify potential general or specific patterns and speculate on their drivers. The observed spatial variability was related to the trophic status of the coastal regions (oligotrophic Mediterranean Sea versus meso- to eutrophic English Channel and Atlantic ocean), but not to ecosystem typology (estuaries, versus lagoons versus bays versus littoral systems). Furthermore, it highlighted local specificities in terms of the origin of the POM assimilated by bivalves (e.g., mainly continental POM vs. marine phytoplankton vs. microphytobenthic algae). Likewise, seasonal variability was related both to the reproduction cycle for C/N ratios of Mytilus spp. and to changes in trophic resources for δ¹³C of species located close to river mouth. Multi-decadal evolution exhibited shifts and trends for part of the 30-year series with decreases in δ¹³C and δ¹⁵N. Specifically, shifts appeared in the early 2000's, likely linking bivalve isotopic ratios to a cascade of processes affected by local drivers.

Growth, condition and metal concentration in juveniles of two Diplodus species in ports

High abundances of juvenile fish in certain ports suggest they might provide alternative nursery habitats for several species. To further investigate this possibility, post-settlement growth, metal uptake and body condition were estimated in 127 juveniles of two seabream species, collected in 2014-15, inside and outside the highly polluted ports of the Bay of Toulon. This showed that differences in local pollution levels (here in Hg, Cu, Pb and Zn) are not consistently mirrored within fish flesh. Muscle metal concentrations, below sanitary thresholds for both species, were higher in ports for Cu, Pb and V only. Otherwise, fish muscle composition principally differed by species or by year. Juvenile growth and condition were equivalent at all sites. Higher prey abundance in certain ports might therefore compensate the deleterious effects of pollution, resulting in similar sizes and body conditions for departing juvenile fish than in nearby natural habitats.

Chemical contaminants (trace metals, persistent organic pollutants) in albacore tuna from western Indian and south-eastern Atlantic Oceans: Trophic influence and potential as tracers of populations

Albacore tuna (Thunnus alalunga) is a highly commercial fish species harvested in the world's Oceans. Identifying the potential links between populations is one of the key tools that can improve the current management across fisheries areas. In addition to characterising populations' contamination state, chemical compounds can help refine foraging areas, individual flows and populations' structure, especially when combined with other intrinsic biogeochemical (trophic) markers such as carbon and nitrogen stable isotopes. This study investigated the bioaccumulation of seven selected trace metals - chromium, nickel, copper (Cu), zinc (Zn), cadmium (Cd), mercury (Hg) and lead - in the muscle of 443 albacore tunas, collected over two seasons and/or years in the western Indian Ocean (WIO: Reunion Island and Seychelles) and in the south-eastern Atlantic Ocean (SEAO: South Africa). The main factor that explained metal concentration variability was the geographic origin of fish, rather than the size and the sex of individuals, or the season/year of sampling. The elements Cu, Zn, Cd and Hg indicated a segregation of the geographic groups most clearly. For similar sized-individuals, tunas from SEAO had significantly higher concentrations in Cu, Zn and Cd, but lower Hg concentrations than those from WIO. Information inferred from the analysis of trophic markers (δ¹³C, δ¹⁵N) and selected persistent organic pollutants, as well as information on stomach contents, corroborated the geographical differences obtained by trace metals. It also highlighted the influence of trophic ecology on metal bioaccumulation. Finally, this study evidenced the potential of metals and chemical contaminants in general as tracers, by segregating groups of individuals using different food webs or habitats, to better understand spatial connectivity at the population scale. Limited flows of individuals between the SEAO and the WIO are suggested. Albacore as predatory fish also provided some information on environmental and food web chemical contamination in the different study areas.

3D-printed flow system for determination of lead in natural waters

The development of 3D printing in recent years opens up a vast array of possibilities in the field of flow analysis. In the present study, a new 3D-printed flow system has been developed for the selective spectrophotometric determination of lead in natural waters. This system was composed of three 3D-printed units (sample treatment, mixing coil and detection) that might have been assembled without any tubing to form a complete flow system. Lead was determined in a two-step procedure. A preconcentration of lead was first carried out on TrisKem Pb Resin located in a 3D-printed column reservoir closed by a tapped screw. This resin showed a high extraction selectivity for lead over many tested potential interfering metals. In a second step, lead was eluted by ammonium oxalate in presence of 4-(2-pyridylazo)-resorcinol (PAR), and spectrophotometrically detected at 520nm. The optimized flow system has exhibited a linear response from 3 to 120µgL^-1. Detection limit, coefficient of variation and sampling rate were evaluated at 2.7µgL^-1, 5.4% (n=6) and 4 sampleh^-1, respectively. This flow system stands out by its fully 3D design, portability and simplicity for low cost analysis of lead in natural waters.

Integrated monitoring of chemicals and their effects on four sentinel species, Limanda limanda, Platichthys flesus, Nucella lapillus and Mytilus sp., in Seine Bay: A key step towards applying biological effects to monitoring

The International workshop on Integrated Assessment of CONtaminants impacts on the North sea (ICON) provided a framework to validate the application of chemical and biological assessment thresholds (BACs and EACs) in the Seine Bay in France. Bioassays (oyster larval anomalies, Corophium arenarium toxicity assay and DR Calux) for sediment and biomarkers: ethoxyresorufin-O-deethylase (EROD) activity, acetylcholinesterase (AChE) activity, lysosomal membrane stability (LMS), DNA strand breaks using the Comet assay, DNA adducts, micronucleus (MN), PAH metabolites, imposex, intersex and fish external pathologies were analysed in four marine sentinel species (Platichthys flesus, Limanda limanda, Mytilus sp. and Nucella lapilus). Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and heavy metals were analysed in biota and sediment. Results for sediment and four species in 2008-2009 made it possible to quantify the impact of contaminants using thresholds (Environmental Assessment Criteria/EAC₂₀₀₈: 70% and EAC₂₀₀₉: 60%) and effects (EAC₂₀₀₈: 50% and EAC₂₀₀₉: 40%) in the Seine estuary. The Seine estuary is ranked among Europe's most highly polluted sites.

Spatial and temporal distribution of mercury and methylmercury in bivalves from the French coastline

Marine mercury (Hg) concentrations have been monitored in the French coastline for the last half a century using bivalves. The analyses presented in this study concerned 192 samples of bivalves (mussels: Mytilus edulis and Mytilus galloprovincialis and oysters: Crassostrea gigas and Isognomon alatus) from 77 sampling stations along the French coast and in the French Antilles sea. The goals of this study were to assess MeHg levels in various common bivalves from French coastline, and to identify possible geographic, taxonomic or temporal variations of concentrations. We show that the evolution of methylmercury (MeHg) concentrations covary with total mercury (HgT) concentrations. Moreover, in most of the study sites, HgT concentrations have not decreased since 1987, despite regulations to decrease or ban mercury used for anthropic activities.

Evidencing the Impact of Coastal Contaminated Sediments on Mussels Through Pb Stable Isotopes Composition

Heavily contaminated sediments are a serious concern for ecosystem quality, especially in coastal areas, where vulnerability is high due to intense anthropogenic pressure. Surface sediments (54 stations), 50 cm interface cores (five specific stations), river particles, coal and bulk Pb plate from past French Navy activities, seawater and mussels were collected in Toulon Bay (NW Mediterranean Sea). Lead content and Pb stable isotope composition have evidenced the direct impact of sediment pollution stock on both the water column quality and the living organisms, through the specific Pb isotopic signature in these considered compartments. The history of pollution events including past and present contaminant dispersion in Toulon Bay were also demonstrated by historical records of Pb content and Pb isotope ratios in sediment profiles. The sediment resuspension events, as simulated by batch experiments, could be a major factor contributing to the high Pb mobility in the considered ecosystem. A survey of Pb concentrations in surface seawater at 40 stations has revealed poor seawater quality, affecting both the dissolved fraction and suspended particles and points to marina/harbors as additional diffuse sources of dissolved Pb.

Multivariate optimization of solid-phase extraction applied to iron determination in finished waters

In this work, Amberlite XAD-4 resin functionalized with salicylic acid was synthetized, characterized and applied as a new packing material for an on-line system to iron determination in aqueous samples. The detection method is based on the sorption of Fe(III) ions in a minicolumn containing the synthesized resin, followed by a desorption step using an acid solution and measurement of iron by vis-spectrophotometry (CAS method). The optimization of the solid-phase extraction system was performed using factorial design and Doehlert matrix considering six variables: sample percolation rate (0.5-9 ml min(-1)), sample metal concentration (20-200 microg l(-1)), flow-through sample volume (0-5 ml) (all three directly linked to the extraction step), elution flow-rate (0.5-9 ml min(-1)), concentration and volume of eluent (HCl 0.1-0.5M) (all three directly linked to the elution step). The aim of this study was to obtain a set of operating ranges for the six variables tested in order to obtain--by means of a mathematical function allowing maximisation of each response (desirability function)--at least 90% of iron recovery rates. Using the experimental conditions defined in the optimization, the method allowed iron determination with achieved detection limit of 2.3 microgl(-1) and precision (assessed as the relative standard deviation) of 9.3-2.8% for iron solutions of 10.0-150 microgl(-1). Real samples (coming from a water treatment unit) were used successfully when evaluating potentialities of the developed SPE procedure coupled to a spectrophotometric determination.

On-line solid-phase extraction and multisyringe flow injection analysis of Al(III) and Fe(III) in drinking water

A new analytical method was developed for on-line monitoring of residual coagulants (aluminium and iron salts) in potable water. The determination was based on a sequential procedure coupling an extraction/enrichment step of the analytes onto a modified resin and a spectrophotometric measurement of a surfactant-sensitized binary complex formed between eluted analytes and Chrome Azurol S. The optimization of the solid phase extraction was performed using factorial design and a Doehlert matrix considering six variables: sample percolation rate, sample metal concentration, flow-through sample volume (all three directly linked to the extraction step), elution flow rate, concentration and volume of eluent (all three directly linked to the elution step). A specific reagent was elaborated for sensitive and specific spectrophotometric determination of Al(III) and Fe(III), by optimizing surfactant and ligand concentrations and buffer composition. The whole procedure was automated by a multisyringe flow injection analysis (MSFIA) system. Detection limits of 4.9 and 5.6 microg L(-1) were obtained for Al(III) and Fe(III) determination , respectively, and the linear calibration graph up to 300 microg L(-1) (both for Al(III) and Fe(III)) was well adapted to the monitoring of drinking water quality. The system was successfully applied to the on-site determination of Al(III) and Fe(III) at the outlet of two water treatment units during two periods of the year (winter and summer conditions).

An experimental design to optimize the flow extraction parameters for the selective removal of Fe(III) and Al(III) in aqueous samples using salicylic acid grafted on Amberlite XAD-4 and final determination by GF-AAS

In this paper, a multivariable approach has been applied for the selective removing of Fe(III) and Al(III), in the range 0-200 microg l(-1), in water samples onto a modified organic support (salicylic acid grafted on XAD-4). An empirical mathematical model was designed which establishes the relationship between the variation of the responses (extraction yields), and the variation of three factors (sample volume, sample percolation flow rate and amount of metallic ions present in the sample). To estimate the coefficients of the developed model, an uniform shell Doehlert design has been applied; these experiments consisted in GF-AAS determination of aluminium and iron amounts in eluates after percolation of samples through modified support. Results show a similar behaviour of the resin towards aluminium and iron with a preponderant effect of the percolation flow rate value; however this one is crucial for aluminium extraction and should be maintained below to 0.55 ml min(-1) to reach a 95% Al3+ extraction yield (versus 2.25 ml min(-1) for Fe3+). The optima determined by this experimental design approach have been further applied to the selective extraction of aluminium and iron from multielement synthetic samples and from real samples at the outlet of potable water treatment units.

Fluorimetric determination of aluminium in water by sequential injection through column extraction

A fluorimetric procedure for the determination of aluminium with matrix removal in drinking water is proposed. The system is based both on the solid phase extraction of aluminium on a new chelating resin (XAD-4 modified by grafting salicylic acid) and the fluorimetric detection of a complex formed between 8-hydroxyquinoline-5-sulfonic acid (HQS) and Al(III), after elution of the resin by hydrochloric acid. The sorption and elution of aluminium were studied in both competitive and noncompetitive conditions, varying pH, flow-rates, volume and concentration of reagents, as well as time contact. The optimised procedure allows determination of Al3+ at the sub-ppb level (LOD: 0.2 microg L(-1) for 1 ml of sample) within a working range of 0.2-500 microg L(-1). The analytical procedure was successfully employed for the determination of aluminium in drinking water during and after flocculation/coagulation treatment processes.