Manuel P. Mánuel-Vez

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.

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.

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.

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.

Multicomponent analysis by flow injection using a partial least-squares calibration method. Simultaneous spectrophotometric determination of iron, cobalt and nickel at sub-ppm levels

A partial least-squares multivariate calibration method for the analysis of binary and ternary mixtures of Fe, Co and Ni, based on their reaction with 2,2′-dipyridyl ketone picolinoylhydrazone in a flow injection manifold was developed. The parameters controlling the behaviour of the system were investigated. For individual determinations, molar absorptivities of 6.64 × 103(Fe, 367 nm), 3.89 × 103(Co, 410 nm) and 5.17 × 103 l mol–1 cm–1(Ni, 385 nm), were obtained, the limits of detection being 1.062, 1.489 and 0.685 µmol l–1, for Fe, Co and Ni, respectively. The optimized method was applied to the analysis of two samples with complex matrices (a washing solution used in an automotive factory and a waste acidic mine effluent).

High-throughput automatic flow method for determination of trace concentrations of aluminum in dialysis concentrate solutions using salicylaldehyde picolinoylhydrazone as a turn-on fluorescent probe.

A simple and expedient flow-based assembly capitalizing on programmable flow is herein proposed for reliable determination of trace level concentrations of aluminum as a potential contaminant in dialysis concentrate solutions without any prior sample clean-up/preconcentration procedure. Using salicylaldehyde picolinoylhydrazone in weakly acidic media as a turn-on fluorescent probe, the manifold is devised to handle three samples concurrently in stopped-flow reaction mode for simultaneous improvement of the analytical sensitivity and sample throughput. Analytical parameters influencing the sensitivity and repeatability of the assays, namely, probe concentration, reaction temperature and reaction time were investigated using a multivariate optimization protocol composed of a full factorial screening design followed by a Doehlert matrix model. The analysis of the Pareto chart and surface response revealed that the reaction time and amount of fluorescent probe were critical parameters for reliable assays of aluminum at the low ng mL(-1) level. Under the optimized chemical and physical variables, a detection limit of 1.1ngmL(-1) Al(III) at the 3s(blank) level, relative standard deviations better than 1.0%, a dynamic linear range of 5.0-80 ng mL(-1) and a sample throughput up to 25 h(-1) were obtained with no need for either sample preconcentration or the use of organized supramolecular systems. Demonstrated with the analysis of hemodialysis and peritoneal concentrate solutions, and dialysis waters, the flow-through method copes with the requirements of regulatory bodies (e.g., European Pharmacopeia) for quality control of aluminum in high salinity containing dialysis concentrates.

Spectrofluorimetric determination of titanium with 2-acetylpyridine picolinoylhydrazone and application to agricultural soil extracts

Abstract The synthesis, solubility, electronic, fluorescence, infrared and mass spectra, ionization constants and analytical applications of 2-acetylpyridine picolinoylhydrazone are described. This compound forms a fluorescent system (blue) with titanium(IV) [λ(ex) 366 nm, λ(em) 445 nm] in an acidic medium. A procedure based on the direct or standard additions methods has been proposed for the determination of Ti(IV) concentrations down to 100 ng l−1. The effect of 70 ions on the proposed method was evaluated and different masking reactions were tested. The method has been used satisfactorily for the determination of titanium at the μg l−1 level in acetate extracts of agricultural soils.

A SIMPLE PROCEDURE TO IMPROVE THE ANALYTICAL PERFORMANCE OF FLOW INJECTION SYSTEMS

ABSTRACT The optimisation of flow injection analysis (FIA) manifolds is usually performed with the univariate procedure, although in many cases they do not allow to find optimum conditions due to the interaction errors caused by the interdependence between variables. However, many authors prefer the univariate methodology instead of the more correct multivariate methods, probably due to the higher theoretical difficulty of the latter. In this work we demonstrate that by applying a very simple multivariate procedure, the results obtained are better than those obtained by using the univariate optimisation. To illustrate this, the conditions for a FIA manifold used for the determination of phosphates (P-PO4 3−) in natural water has been studied by using two different procedures: the classical univariate method and a second one based on experimental design. Experimental design procedures take into account the interactions between the variables optimised, which are ignored by univariate procedures. The classical univariate procedure found experimental conditions that produced less precise and accurate results (RSD=13.6%; ϵ r=11.1%) than those obtained when the performance of FIA system was studied with the simpler method based on 2n experimental design (RSD=4.2%; ϵ r=6.3%). Sensitivity was also improved and lower limits of detection were obtained with experimental design (river water: 5.6 µg L−1;seawater: 5.9 µg L−1) than with the univariate methodology (river water: 87.1 µg L−1; seawater: 88.9 µg L−1). Besides, the use of experimental design allowed reducing both waste production and cost of analysis.