Manuel García-Vargas

Bioavailability of heavy metals monitoring water, sediments and fish species from a polluted estuary.

Concentrations of heavy metals (Cu, Zn, Cd, Pb and As) were measured in water, sediment and two fish species, Sparus aurata and Solea senegalensis, from the estuary of Tinto and Odiel rivers in Huelva (Spain), one of the most metallic polluted estuaries in Europe. As a forward step to understand metal bioavailability and assess the potential impact on aquatic biota, a study of heavy metal speciation of sediments and water were achieved. High levels of total and dissolved Zn and Cu were found in water and high pollution of Zn, Pb, As and Cu were found in sediments. Availability of metals was established as following ranking: Cd>Zn>Cu>Pb in both water and sediment. In addition, the effect of this pollution was studied by evaluation of metal bioaccumulations and correlations obtained between metal levels in fractions of water and sediment and metal levels in fish tissues. High Cu and Zn levels were observed in liver tissue of both species, in according with higher total content and more available metals in water and sediment. Correlations among metal content in tissues and different fractions of metal in water for S. aurata and sediment for S. senegalensis were found.

A trace metal clean reagent to remove surface-bound iron from marine phytoplankton

Many recent studies have investigated Fe biogeochemical cycling, chemical speciation, and limitation of phytoplankton growth in the ocean. In current models of marine iron biogeochemistry, however, two critical parameters remain uncertain. These are the partitioning of particulate iron into scavenged and interior pools, and the iron quotas (Fe/C ratios) of natural plankton communities. These values have not been measured in natural samples, because the only reagent that is available to remove surface adsorbed Fe from cells and other particles (Ti(III) citrate/EDTA [Limnol Oceanogr 34 (1989) 1113]) contains substantial levels of contaminating Fe, and is therefore useful only for Fe radiotracer experiments. We developed a new reagent that differentiates between intra- and surface adsorbed Fe pools in marine phytoplankton as effectively as the Ti wash, but that is also trace metal clean, chemically stable, and harmless to cells. This reagent uses oxalate as a reductant to remove surface adsorbed Fe from phytoplankton cells and other particles. A simple cleaning protocol reduces Fe concentrations in the oxalate solution to levels suitable for trace metal clean field measurements. The oxalate reagent was used to measure scavenged and interior Fe pools in suspended particles collected at four stations in the Southern Ocean. Sixteen percent to eighty-six percent of the total Fe associated with these samples was found to be surface-adsorbed. The oxalate reagent provides a new tool to accurately measure the physical partitioning of Fe in marine particles and could be used along with appropriate corrections for lithogenic Fe to estimate the intracellular Fe quotas of natural plankton communities.

Environmental impacts of intensive aquaculture in marine waters

The effects of marine aquaculture on the environment were evaluated by studying the water quality of San Pedro river, a canal located within the Bay of Cadiz (SW of Spain). Marine aquaculture, both extensive and intensive, is one of the most important activities carried out in this area. Several facilities are located on this river, the most important being devoted to the intensive culture of Gilthead Seabream (Sparus aurata). The characterization of the water consisted of the evaluation of the variation of several parameters along the river and during different seasons. These parameters were pH, temperature, salinity, dissolved oxygen, suspended solids and nutrients (ammonium, nitrite, nitrate and phosphate). With a water quality criteria based on local laws, a significant but not dangerous pollution was observed in the area, with ammonium and suspended solids being the most significant pollutants.

Assessment of the metal pollution, potential toxicity and speciation of sediment from Algeciras Bay (South of Spain) using chemometric tools.

A study to determine total and mobile heavy metals concentrations in sediments from Algeciras Bay was performed and pollution hotspots were identified. The effects on aquatic organisms were established using sediment quality guidelines (SQGs). Ni and Cr exceeded the effect range medium and low levels, respectively, around industrial area. Potential toxicity of metals was determined by diethylenetriaminepenta-acetic acid (DTPA) extractions and low alert levels of Co, Cu, Zn, Cd, Ni and Pb were exceeded at most sampling sites. Three pollution indicators were used showing significant values for As, Ni, Cr, Pb and Cd. Sediment speciation using the sequential extraction BCR procedure was carried out, being Cd, Zn, Pb and As the most available metals. Principal component, cluster and ANOVA analyses were performed in order to assess the sources of metals and the influence of seasonality and anthropogenic activities on the sediment quality. Two principal component analysis (PCA) factors were obtained identifying the sampling sites affected by anthropogenic activities; Ni-Cr and Zn-Cu-V clusters were also obtained associated with stainless steel and petrochemical industrial activities. ANOVA showed the outstanding sites because of total metal concentration and significant differences among sampling sites by the acid extractable and reducible fractions for all metals except for Ba and V.

Environmental implications of intensive marine aquaculture in earthen ponds.

Abstract In recent decades, the importance of marine aquaculture has grown substantially in most countries. Following a period of uncontrolled activities, the concern for the environmental implications of intensive mariculture has increased notably, and environmental impact is often taken into account when aquaculture activities are established. Among the most important pollutant effects of aquaculture are the outputs of dissolved nutrients, suspended solids and organic matter. In the present study, we have determined the loadings of dissolved nutrients (ammonium, nitrite, nitrate and phosphate), total suspended solids (TSS) and organic matter (particulate organic matter (POM) and biochemical oxygen demand (BOD 5 )) in the effluent of a marine fish farm devoted to the intensive culture of gilthead seabream ( Sparus aurata ) in earthen ponds. Samples of seawater were taken monthly during a two-year period (April 1997–March 1999) in the two inflows and the outflow of the fish farm. The environmental impact of marine aquaculture was established by estimating the total amount of each compound discharged into the receiving waters as a direct consequence of the culture activities. Thus, 9104.57 kg TSS, 843.20 kg POM, 235.40 kg BOD, 36.41 kg N–NH 4 + , 4.95 kg N–NO 2 − , 6.73 kg N–NO 3 − and 2.57 kg P–PO 4 3− , dissolved in the seawater, were estimated to be discharged to the environment for each tonne of fish cultured.

Pyridine-2-carbaldehyde 2-hydroxybenzoylhydrazone as a selective reagent for the extraction and spectrophotometric determination of iron(II)

Pyridine-2-carbaldehyde 2-hydroxybenzoylhydrazone reacts with iron(II) to produce a green 2:1 complex (λmax. = 620 nm, Iµ= 3.64 × 103 l mol–1 cm–1 in aqueous ethanolic solution, and λmax. = 640 nm, Iµ= 3.67 × 103 l mol–1 cm–1 in chloroform). The green complex, extracted into chloroform, has been used for the spectrophotometric determination of trace amounts of iron. The method has a high selectivity and has been applied to the determination of iron in different samples, such as industrial waste water, non-ferrous materials and minerals.

Reverse flow-injection manifold for spectrofluorimetric determination of aluminum in drinking water.

A simple reverse flow-injection (rFIA) manifold for the direct determination of aluminum in drinking water is proposed. This rapid and sensitive method is based on the formation of an Al(3+) complex with salicylaldehyde picolinoylhydrazone (SAPH), which shows a maximum blue-green fluorescence (lambda(ex)=384 nm, lambda(em)= 468 nm) at pH 5.4. Operative conditions both for batch and rFIA procedures were investigated including reagent concentration, buffer solutions, injection loop, reacting coil and wavelengths used for the fluorimetric detection. The tolerance limits of foreign ions have been also evaluated, before and after the addition of masking agents. The reverse flow-injection procedure allows determination of Al(3+) at ppb level (LOD: 1.9 mug l(-1)) within a working range of 5-30 mug l(-1). The proposed method was successfully employed for the determination of Al(3+) in several commercial drinking, soft drinking (as certified reference material), and tap water samples.

Ligands with the “ONNN” Group as Chelating and Preconcentrating Substances of Heavy Metal Ions: Aroylhydrazone Derivatives from Di-2-Pyridyl Ketone

The synthesis of the electronic and infrared spectra of di-2-pyridyl ketone salicyloylhydrazone (DPKSH) and di-2-pyridyl ketone benzoylhy-drazone (DPKBH) is reported. Ultraviolet absorption spectra have been applied for determining the dissociation constants: DPKSH, pK1 = 3.5 and pK2 = 6.85; DPKBH, pK1 = 2.75 and pK2 = 10.6. These pK a values are interpreted as a function of the ortho-position of the OH group. Chelating properties of both tridentate ligands have been investigated. DPKSH forms a larger number of metal chelates in acidic media than does DPKBH. Also, it is concluded that DPKSH is a more suitable compound than DPKBH to preconcentrate and to determine heavy metal ion traces as it is inferred from the data obtained by flame AAS.

Fluorimetric determination traces of aluminium in soil extracts

Salicylaldehyde picolinoylhydrazone (SAPH) form a fluorescent complex with aluminium (lambda(ex) = 384 nm, lambda(em) = 468 nm) in acidic medium (stoichiometry 1:3, Al:SAPH). Two procedures based on the direct or standard additions methods has been proposed for the determination of concentrations down to 1-2 mug/dm(3) of Al(III). The effects of 72 ions in the method has been evaluated and different masking agent reactions have been tested. The method has been used satisfactorily for the determination of aluminium at a level of mug/dm(3) in acetate extracts of several agricultural soils. The method has been compared favourably with ICP spectroscopy emission.

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-Cu2+ 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 × 106 M−1. A modified Stern–Volmer relationship was employed to obtain a linear calibration plot, obtaining a dynamic working range up to 157.4 μM. The detection limit of this system was found to be 5.6 μM and the relative standard deviation for five measurements of 78.7 μM concentration was 5.2%. This fluorescent chemosensor also showed a high selectivity for copper ions over other metal ions, such as Al3+, Ca2+, Cd2+, Fe2+, K+, Mg2+, Na+, Pb2+, or Zn2+. 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.