Ecological Status of Algeciras Bay, in a Highly Anthropised Area in South-West Europe, through Metal Assessment-Part I: Abiotic Samples.

The ecological status of Algeciras Bay (South-west Europe), highly influenced by anthropogenic activities, was assessed by monitoring Zn, Cd, Pb, and Cu in water and sediment samples. Total contents and metal fractions with different availabilities and their spatial-seasonal distribution were determined. The trend in water and sediment contents were Zn > Pb ≈ Cu > Cd, without significant seasonal variations. Sites 3 and 4, closest to industrial activities, had the highest metal concentrations, mainly in sediments. Cd showed low partition coefficient in water, indicating higher bioavailability. Total metal content in sediments exceeded the threshold effect level for Cu and were close to Pb. The BCR procedure revealed the highest availabilities for Cd and Pb, due to its higher content in exchangeable and reducible fractions. Higher Pb levels (21.4 ± 5.1 mg/kg) were found in sediments of this bay compared with other ecosystems. Pollution indexes for sediment quality revealed that site 3 was the most polluted (CF = 7.12 and Igeo = 2.25). For an integrative study of the ecological status of this significant bay, these results have been complemented with the metal evaluation in benthic and benthopelagic fish tissues in Ecological status of Algeciras Bay, in a highly anthropised area in south-west Europe, through metal assessment-Part II: Biotic samples.

Ecological Status of Algeciras Bay, in a Highly Anthropised Area in South-West Europe, through Metal Assessment-Part II: Biotic Samples.

Biotic samples from Algeciras Bay (South-west Europe) were studied to assess its ecological status, complementing the previous abiotic monitoring of trace metals in water and sediments. This bay is a densely populated area with intense port traffic and is highly industrialised with metal inputs. To study the impact of this, Zn, Cd, Pb, and Cu contents were determined in tissues of benthic (Solea senegalensis) and benthopelagic species (Scorpaena porcus, Trigloporus lastoviza, and Diplodus sargus sargus). Notable levels of Zn and Cu were found in the liver and gills of all fish species. Compared to international muscle guidelines, Pb sometimes exceeded the most restrictive values, outstanding S. porcus with 27% of samples above the permissible value. Metal pollution indexes revealed that the liver and gills of benthic species were more affected by metal pollution than benthopelagic species, especially in most industrialised sites. Particularly, S. senegalensis presented a higher accumulation factor from sediment of Cd and Cu in the liver (30.1 and 345.1), probably due to the close interaction as benthic species. Among the species studied, S. senegalensis and D. sargus sargus proved to be the best representative and useful bioindicators of metal-polluted environments as this bay. The results were consistent with the findings from the abiotic samples.

Induction of Oxidative Stress by Waterborne Copper and Arsenic in Larvae of European Seabass (Dicentrarchus labrax L.): A Comparison with Their Effects as Nanoparticles.

The aim of this work was to compare the potential induction of oxidative stress and the antioxidant enzymatic response after a short-term waterborne exposure to copper (Cu) and arsenic (As) with that of the nanoparticles (NPs) of these elements (Cu-NPs and As-NPs) in fish larvae of the species Dicentrarchus labrax. Larvae were grouped in several tanks and exposed to different concentrations of contaminants (0 to 10 mg/L) for 24 or 96 h under laboratory conditions. Copper and arsenic concentrations were analysed in larval tissues using ICP-MS. A set of oxidative stress biomarkers, including the levels of hydroperoxides (HPs), and superoxide dismutase (SOD) and catalase (CAT) activities were assessed. The trace element concentrations (mg/kg d.w.) in larvae ranged as follows: 3.28-6.67 (Cu at 24 h) and 2.76-3.42 (Cu at 96 h); 3.03-8.31 (Cu-NPs at 24 h) and 2.50-4.86 (Cu-NPs at 96 h); 1.92-3.45 (As at 24 h) and 2.22-4.71 (As at 96 h); and 2.19-8.56 (As-NPs at 24 h) and 1.75-9.90 (As-NPs at 96 h). In Cu tests, the oxidative damage (ROOH levels) was induced from 0.1 mg/L at both exposure times, while for Cu-NPs, this damage was not observed until 1 mg/L, which was paralleled by concomitant increases in SOD activity. The CAT activity was also increased but at lower metal concentrations (0.01 mg/L and 0.1 mg/L for both chemical forms). No oxidative damage was observed for As or As-NPs after 24 h, but it was observed for As after 96 h of treatment with 0.01 mg/L. A decrease in SOD activity was observed for As after 24 h, but it turned out to be increased after 96 h. However, As-NPs did not alter SOD activity. The CAT activity was stimulated only at 96 h by As and at 24 h by As-NPs. Therefore, the two chemical forms of Cu exhibited a higher bioaccumulation and toxicity potential as compared to those of As. Importantly, the association of both Cu and As in NPs reduced the respective trace metal bioaccumulation, resulting also in a reduction in the toxic effects (mortality and biochemical). Furthermore, the assessment of oxidative stress-related biomarkers in seabass larvae appears to be a useful tool for biomonitoring environmental-occurring trace elements.

A Novel Polymer Inclusion Membrane-Based Green Optical Sensor for Selective Determination of Iron: Design, Characterization, and Analytical Applications.

The design, characterization, and analytical application of a green optical sensor for the selective determination of Fe(II) ions is proposed. The sensor is based on the immobilization of the chromogenic reagent picolinaldehyde salicyloylhydrazone (SHPA) within a polymer inclusion membrane. To reduce solvent usage, the reagent was synthesized using a green mechanochemical procedure. The components for sensor preparation were optimized with a sequential simplex method and the optimal composition was found to be 0.59 g cellulose triacetate (base polymer), 0.04 g SHPA (chemosensor reagent), 4.9 mL dibutyl phthalate (plasticizer), and 38 mL dichloromethane (solvent). The conditions of iron analysis were also optimized resulting in pH 6 for aqueous solution, 90 min exposure time and 10 min short-term stability. The optical sensor showed a linear range from the limit of detection (0.48 µmol L-1) to 54 µmol L-1 Fe(II). The precision of the method was found to be 1.44% and 1.19% for 17.9 and 45 µmol L-1 Fe(II), respectively. The characteristics of the sensor allowed the design of a Fe(II)/Fe(III) speciation scheme. The methodology was successfully applied to the determination of iron in food preservatives, food additives, and dietary supplement. Additionally, the Fe speciation scheme was successfully applied to an agricultural fertilizer.

Sensing Cd(II) Using a Disposable Optical Sensor Based on a Schiff Base Immobilisation on a Polymer-Inclusion Membrane. Applications in Water and Art Paint Samples.

A disposable colour-changeable optical sensor based on an interesting polymer inclusion-membrane (PIM) was designed to determine Cd(II) ions in aqueous medium. The Schiff base 2-acetylpyridine benzoylhydrazone (2-APBH) immobilised on the polymer membrane was used as a sensing molecule. The amounts of the PIM components were optimised by a 32 fractional factorial design with two central points and two blocks. The best optical sensor composition consisted of 2.5 g of poly(vinylchloride) (PVC) as a base polymer, 3 mL of tributyl phosphate (TBP) as a plasticiser, and 0.02 g of 2-APBH as a reagent. The sensor showed a good linear response in the range from 0.02 mg L-1 (limit of detection) to 1 mg L-1 of Cd(II) under the following experimental conditions: pH 9.5 (adjusted using ammonium chloride buffer solution at 0.337 mol L-1), 60 min of exposure time plus 2 min of sonication (pulses at 2 s intervals), and 10 min of short-term stability. The relative standard deviation of the method was determined to be 4.04% for 0.4 mg L-1 of Cd(II). The optical sensor was successfully applied to the determination of Cd(II) in natural-water and art-paint samples.

Water quality in the tropical Andes hotspot: The Yacuambi river (southeastern Ecuador).

Yacuambi river waters (southeast Ecuador, Amazonian region) were assessed to evaluate the potential risk to populations, who use it for drinking and irrigation, and ecosystems, which are part of Tropical Andes hotspot and considered some of the most biodiverse in the world. The water quality index was calculated and some quality parameters were checked to comply with Ecuadorian and North American standards for human consumption, preservation of aquatic life and irrigation. Four samplings were carried out in six stations covering the entire length of the Yacuambi river. Several parameters were analyzed: pH, conductivity, dissolved oxygen, temperature, color, phosphates, nitrite, nitrate, biochemical oxygen demand, chemical oxygen demand, total solids, turbidity, metals (Ba, Cd, Cr, Pb, As and Hg), pesticides and fecal coliforms. The water quality in the Yacuambi river was good and medium according to the classification of the Water Quality Index. However, it was unsuitable for human consumption, preservation of aquatic life and irrigation according to Ecuadorian and North American standards. Arsenic, color and fecal coliforms exceeded the limits for human consumption in all samples tested. Thresholds of preservation of aquatic life were exceeded in all samples in the case of Pb and in some samples for As, pH, nitrite and nitrate. Arsenic and fecal coliforms made Yacuambi river waters unsuitable for irrigation.

Determination of ultra-trace amounts of silver in water by differential pulse anodic stripping voltammetry using a new modified carbon paste electrode.

A highly sensitive and selective new procedure for the determination of silver in aqueous media was developed using a modified carbon paste electrode (MCPE) by differential pulse anodic stripping voltammetry (DPASV). The modified electrode was based on the incorporation of 2-hydroxybenzaldehyde benzoylhydrazone (2-HBBH) in the carbon paste electrode. Silver ions were preconcentrated on the modified electrode at open-circuit by complexation with the ligand and reduced to zero valent at a potential of 0V, and followed by the reoxidation of adsorbed ions onto the electrode by scanning the potential in a positive direction. The oxidation peak of Ag(I) was observed at 0.2V (versus Ag/AgCl). The analysis of Ag(I) was carried out in a cell containing the sample solution (20mL) buffered by 0.1molL(-1) K2HPO4/NaOH at pH 5.5 in aqueous solution and nitric acid (pH 1) in real water samples. The optimum conditions for the analysis of silver include a reduction potential of 0V and a pulse amplitude of 100mV, among others. The optimum carbon paste composition was found to be 14.1% (w/w) 2-HBBH, 56.2% (w/w) graphite powder and 29.7% (w/w) paraffin oil. Differential pulse anodic stripping voltammetric response was used as the analytical signal. Under the selected conditions, the voltammetric signal was proportional to the Ag(I) concentration in the range of 0.001-100µgL(-1) with favorable limits of detection and quantification of 1.1ngL(-1) and 3.7ngL(-1) after 3min of accumulation time, respectively. By increasing the accumulation time to 10min, detection and quantification limits can be further improved up to 0.1ngL(-1) and 0.34ngL(-1), respectively. In addition, the results showed a highly reproducible procedure showing a relative standard deviation of 1.5% for 12 replicate measurements. Many coexisting metal ions were investigated and very few interferences were found on the determination of Ag(I). The proposed method was validated using certified reference estuarine waters (SLEW-3) with a relative error of -1.3% and applied to the determination of silver ions in three river water samples collected from Guadalquivir river (relative errors of +3.4%, +1.5% and -0.7%). Moreover, the method was successfully applied to the speciation analysis of total silver, free silver ions and silver nanoparticles in aqueous solutions. The results were in good agreement with those obtained by inductively coupled plasma mass spectrometry (ICP-MS).

EROD activity and cytochrome P4501A induction in liver and gills of Senegal sole Solea senegalensis from a polluted Huelva estuary (SW Spain).

EROD activity and induction cytochrome P4501A in liver and gills of Senegal sole, Solea senegalensis, from a heavy metal and PAH polluted estuary, was studied. Liver and gill CYP1A catalytic activity was assessed at the enzyme activity level-measured as 7-ethoxyresorufin-O-deethylase and cellular localization of CYP1A in the liver was studied using immunohistochemistry. Liver EROD was correlated with phenanthrene-type metabolites in liver and copper concentrations in water. Strong CYP1A occurrence was observed in acinar pancreatic cells, pancreatic duct epithelium and vascular system endothelium and negative/rare induction were observed in hepatocytes and sinusoidal endothelium. In gills, EROD activity showed a significant correlation with different fractions of heavy metals in sediment but no correlation was observed between EROD activity and PAHs. Strongly positive CYP1A associated staining of the vascular system endothelia and primary filament cells and a moderate staining of pillar cells in gills were observed. The results substantiated the utility of EROD activity and CYP1A induction measurement as biomarkers for use by aquatic toxicologists and indicate that catalytic assays and immunohistochemical assays appear to be sensitive to different kinds of pollutants being the use of both methods recommended for monitoring programs.

Colorimetric solid-phase extraction method for Cu(II) ion determination using 2-hydroxybenzaldehyde benzoylhydrazone as sensing reagent.

A new sensor based on the use of 2-hydroxybenzaldehyde benzoylhydrazone as a colorimetric reagent immobilized onto styrenedivinylbenzene disks has been carried out for the determination of Cu(II) ions within several minutes. The sensor is designed on a rapid and easy two-step procedure: (1) the extraction of Cu(II) ions onto a disk loaded with the copper-selective colorimetric reagent and (2) the determination of the complexed analyte directly on the surface of the disk using diffuse reflectance measurements at 400 nm. The color of the disk changed from white to green in the presence of Cu(II) ions. The work herein details the optimization of the sensing system employing a fractional factorial design 3(3-1) considering three variables (pH, immobilization time, and amount of ligand immobilized onto the disk). The Pareto chart and response surfaces in a spherical domain indicated that the optimum conditions for the sensing of copper ions were pH = 7, with a ligand immobilization time of 10 min and 6.25 mg of reagent loaded onto the disk. Under the optimum conditions, the analytical parameters of the proposed method were determined. The calibration graph was linear over the range of 0 to 2.5 mg L(-1) of Cu(II) with a detection limit of 0.21 mg L(-1). The relative standard deviation for six measurements of 1 mg L(-1) of Cu(II) was found to be 4.87%. The interference from inorganic salts and other metals was found not to be of major concern when monitoring copper ions in water samples. The simplicity and rapidity of this technique make it convenient and amenable for on-site and routine analysis.

Biomarkers responses in muscle of Senegal sole (Solea senegalensis) from a heavy metals and PAHs polluted estuary.

The biochemical responses in muscle, such as the enzymatic activities of acetylcholinesterase, lactate dehydrogenase and isocitrate dehydrogenase, were studied in sole (Solea senegalensis) collected in Huelva estuary (SW Spain), in the vicinity of a petrochemical and mining industry. The sampling sites showed different type and degree of pollution. The results demonstrated significant differences in muscle activities of AChE and IDH in Odiel and Tinto Rivers compared to control fish. LDH activity did not show any difference between sampling sites. Significant correlations were established between some biomarkers and heavy metals: AChE was correlated with Pb, Cd and Cu concentrations in water; IDH activity was correlated with Cd and Cu concentrations in water and As, Pb and Cd concentrations in sediments; LDH activity was correlated with As and Zn concentration in water and Cd concentration in sediment. Only one correlation was established between the biomarkers analysed and the concentrations of PAHs: benzo(b)fluoranthene concentration in sediment and IDH.

Selective chemosensor for copper ions based on fluorescence quenching of a Schiff-base fluorophore.

A Schiff base-based fluorescent chemosensor has been studied for divalent copper detection. The formation of 2-hydroxybenzaldehyde benzoylhydrazone-Cu(2+) complex induced a fluorescence quenching of this compound in a medium of water/ethanol (53% v/v) and 0.05 M phosphate buffer (pH 7.0). The continuous variations and mole-ratio plots of absorbance suggested a complex formation with a 1:1 metal-ligand stoichiometry. The conditional stability constant for the complex was evaluated to be 6 x 10(6) M(-1). A modified Stern-Volmer relationship was employed to obtain a linear calibration plot, obtaining a dynamic working range up to 157.4 microM. The detection limit of this system was found to be 5.6 microM and the relative standard deviation for five measurements of 78.7 microM concentration was 5.2%. This fluorescent chemosensor also showed a high selectivity for copper ions over other metal ions, such as Al(3+), Ca(2+), Cd(2+), Fe(2+), K(+), Mg(2+), Na(+), Pb(2+), or Zn(2+). The results of this investigation show a simple, rapid, low-cost, and selective method that can operate in neutral solutions and is useful for biological and environmental applications.

Factorial designs applied to the development of a capillary electrophoresis method for the analysis of zinc, sodium, calcium and magnesium in water samples.

The aim of this work was to study the influence of several both chemical and instrumental variables for the development of a new capillary electrophoresis (CE) method for the determination of zinc, sodium, calcium and magnesium in water samples by using 1,10-phenanthroline as complexing agent and UV photometric detection at 214 nm. Due to the number of parameters involved and their interactions, factorial experimental designs at two levels have been applied to investigate the influence of several experimental variables (concentration of complexing agent, concentration of a visualisation agent, pH, sample introduction, applied voltage and capillary length) in sets of several capillary electrophoretic responses. The method was applied to the simultaneous determination of Na(I), Ca(II), Mg(II) and Zn(II) in drinking water with satisfactory results and a detection limit of 32 ng ml(-1) for Zn(II) was obtained.