Carolina Mendiguchía

Distribution of heavy metals in marine sediments of Tetouan coast (North of Morocco): natural and anthropogenic sources

The heavy metal concentrations (Al, Fe, Ti, Mn, Zn, Cd, Co, Cr, Ni, Pb and Cu) in sediment samples collected from the Moroccan Mediterranean coast were studied. The heavy metal concentrations obtained were similar or relatively low when compared with other Mediterranean zones. To assess their distribution and distinguish between their natural and anthropogenic sources, the enrichment factor (EF) index was applied. Consequently, minor enrichment by Cd, Cu, Fe, Mn and Pb was observed. The effects on aquatic organisms were established using sediment quality guidelines (SQGs). As a result, Cu concentrations were above the interim sediment quality guidelines (ISQG), Ni and Pb presented concentrations above the effects range low (ERL) while Cr was above the probable effect level (PEL) in some sampling points. In addition, a principal component analysis was performed showing that the distribution of metals in the study area seems to be influenced by both natural and anthropogenic sources. Nevertheless, the analysis of mineralogical composition has allowed the identification of a natural source as the most probable origin of some elements, such as Ni and Mn, related mainly to the geological background. In contrast, Fe, Cr, Co and Pb could be related to both natural and anthropogenic activities in the area while Cd and Cu seem to have an anthropic origin.

Screening of dissolved heavy metals (Cu, Zn, Mn, Al, Cd, Ni, Pb) in seawater by a liquid-membrane-ICP-MS approach.

A bulk liquid membrane system has been developed and applied to the simultaneous separation and preconcentration of up to seven heavy metals (copper, zinc, lead, cadmium, aluminium, manganese, and nickel) in seawater. Copper was selected to optimize transport conditions and then, under these conditions, the simultaneous extraction of other heavy metals was studied. The system achieved preconcentration yields ranging between 44.11% (Cd) and 77.77% (Cu) after nine hours of operation, the effectiveness of metal transport being Cu > Zn > Pb > Mn > Ni > Al > Cd. The system was applied to the preconcentration of four real seawater samples before their quantification by inductively coupled plasma–mass spectrometry (ICP–MS). Compared with the analytical procedures commonly used for trace metal determination in oceanography, the results obtained demonstrated that the new system may be used as a very clean (sample contamination-free), simple, and one-step alternative for semiquantitative, and even quantitative, simultaneous determination of heavy metals in seawater.

Separation of heavy metals in seawater by liquid membranes: Preconcentration of copper

A bulk liquid membrane system has been used to preconcentrate and separate the copper ions present in a seawater sample prior to its analysis by flame atomic absorption spectroscopy. The liquid membrane comprised an organic solution containing di-(2-ethylhexyl) phosphoric acid (DEHPA) in kerosene. The preconcentration system was optimized by studying the influence of the acidity of the sample and the receiving solution, the DEHPA concentration in the organic membrane, and the stirring rate. Under optimum conditions, the preconcentration yield for real samples was 87.0%. The average relative error of the determination was 3.6%, while relative standard deviation averaged 7.8%. The reliability of the new method was confirmed by analyzing several real samples of seawater, analyzed previously by a well-established technique.

Revisiting methods for the determination of bioavailable metals in coastal sediments

A simple methodology for the determination of bioavailability of fourteen metals in coastal sediments has been developed by simulating the conditions of digestive process of marine fishes. With this aim, a representative sediment composite sample was treated with hydrochloric acid solutions at different pH values, temperatures and contact times, in the presence and absence of Pepsin and Trypsin. The addition of Pepsin and Trypsin did not affect the extraction of most elements. As a result of the present study, the digestion with a hydrochloric acid solution at pH 1, 40°C and 12h is proposed. Adjustments of the temperature and time reaction could be made according to the specific ecosystem under study. The amount of metal extracted by other methods based on acetic acid was lower than that extracted by HCl treatment proposed.

Analysis of Heavy Metals in Sediments from Northern Moroccan Coast Using Simple and Low-Cost Methodology

A new simple and low-cost digestion method for sediment samples was studied and optimized. It was based on the acid digestions of samples into low-pressure PTFE bombs and heating in a simple convection-based oven, as an alternative to available standard methods based on high-pressure bombs and microwave ovens. Although there is no doubt about the benefits of microwave-based methodologies, there is still a problem related with the high cost of the equipment required, making difficult its practical application in some developing countries. The proposed methodology was optimized by using three certified reference materials (CRMs): marine sediment (GBW07313), estuarine sediment (SRM1646a) and river sediment (CRM320), which were digested separately by the two studied methods. Metal concentrations in the digested extracts were analyzed and compared. Average metals recoveries obtained with the new method ranged from 61 % (Al) to 100 % (Cd, Co, Pb), and, in general, significant differences between the two methodologies were not observed. The new digestion method was applied to the simultaneous determination of up to ten heavy metals in marine sediments from the Northern Moroccan coastline, in the Mediterranean province of Tetouan and Chefchaouen. The results obtained ranged from 1.26-3.32 % for Al, 16.2-20.7 mg/kg for Co, 49.7-72.7 mg/kg for Cr, 20.2-32.3 mg/kg for Cu, 2.98-3.92 % for Fe, 184-394 for Mn, 34.5-44.3 mg/kg for Ni, 36.0-49.7 mg/kg for Pb, 0.46-0.55 % for Ti, and 67.5-83.6 mg/kg for Zn. A statistical data analysis was performed in order to determine the sources of heavy metals in this area. Relatively high concentrations of Cr, Ni and Pb were measured in all the sampling sites, although their anthropogenic origin could not be established. In addition, Cu and organic matter were enriched in sediments close to agricultural areas.

A Liquid Membrane-Based Green Method for the Separation and Determination of Lead in Saline Waters

ABSTRACT In this work, the authors proposed a new liquid membrane-based method for the determination of lead in saline waters. In this case, the new method is based on lead quantification by inductively coupled plasma-mass spectrometry (ICP-MS) after a preconcentration step by means of a bulk liquid membrane (BLM) system. With no sample manipulation, the system transports and preconcentrates the analyte ions in the sample into the acidic receiving solution, by means of an organic membrane containing di-(2-ethylhexyl)-phosphoric acid (DEHPA) acting as a chemical carrier. The chemical variables controlling Pb2+ permeation through the membrane were studied by use of a modified simplex approach. The most appropriate preconcentration rates were found at sample pH 4.7, maintained with a 0.08-M acetate buffer solution, a 0.07-M DEHPA concentration, and a 0.23-M HNO3 receiving solution. Under these conditions, an extraction yield of 93.8 ± 0.1% and a preconcentration factor of 4.2 were obtained, thus allowing lead selective separation and accurate determination in real samples at environmental concentration levels. The system was tested with several real samples from the Gulf of Cádiz containing lead at the low ppb levels.

Quantification of Free and Bound Fractions of Nickel in Natural Waters by Solvent Extraction with 1,2-Cyclohexanedione Bis-Benzoyl-Hydrazone

Abstract An hydrazone derivative, 1,2-cyclohexanedione bis-benzoyl-hydrazone (1,2-CHBBH), has been used as a selective reagent for an advanced environmental application consisting of separating the different species of nickel in natural waters by solvent extraction. The effects of pH and reagent concentration on the extraction process were studied, as well as the influence of both organic (humic acids) and inorganic ligands (Cl−). Under natural conditions, organic and inorganic nickel species presented different extraction behaviors, and the variations in extraction yields could be correlated with the concentrations of organic complexes in the samples, allowing the separation of labile and non-labile nickel species in both fresh and marine waters.

Assessment of sediment pollution by metals. A case study from Cienfuegos Bay, Cuba.

Sediments were grouped in three zones of the bay: two in the northern basin with higher metal contamination; and another in the southern basin, where lithogenic metals were predominant. Sediment pollution classification made using Index of geoaccumulation and Enrichment factor was consistent, indicating higher accumulation of Cd and Pb in the northern basin. The negative influence of activities linked to petrol was predicted by V/Ni and V/(Ni+V) ratios. Cd and Pb did not represent a potential risk; while Cu and Ni could be risky for biota in most sediment, according to Screening Quick Reference Tables (SQuiRTs). Comparison of bioavailable fraction of metals with references in SQuiRTs corroborated the low potential damage on the biota due to As, Cd, Pb, Cr, Zn; and a higher potential damage due to Cu; while an attenuation of the risk due to Ni predicted by SQuiRTs could be expected.

Solvent extraction with organophosphorus extractants in environmental samples: determination of cadmium(II) in natural water

AbstractIn this work, Cd(II) extraction in natural waters by organophosphorus extractants as organic phase, as well as its back-extraction in an acidic media, has been studied. Cadmium extraction behavior at natural waters’ pH conditions (values in the range 7–8) was studied with two different extractants and co-ions, obtaining the highest extraction efficiency when using 0.1M Cyanex 272 in kerosene as organic phase and 0.1 M NO3− as co-ion. Once they were selected, the effect on the extraction efficiency of sample pH, buffer concentration, extraction time, Cyanex 272 concentration as well as back-extractant concentration, was studied. The presence of the main inorganic and organic ligands in the sample was also studied, observing that extraction efficiency was affected most significantly when chlorides were present, with a decrease of about 14%, proving negligible for the others. Under the selected conditions, spiked real samples were successfully analyzed.

Solvent Extraction-Mediated Fractionation of Copper in Waters at Natural pH Conditions

A new solvent extraction system using a hydrazone derivative such as 1,2-cyclohexanedione bis-benzoylhydrazone (1,2-CHBBH) has been studied to separate and quantify the different fractions of copper present in natural waters. The influence of different variables on the extraction has been studied, such as the type of organic solvent, the reagent concentrations in the extraction and back-extraction solutions, the sample pH, and the extraction time. Under selected conditions, the influence of both organic and inorganic ligands present in natural waters on the efficiency of the extraction process has been also investigated. Thus, the effect of the major anion species present in this kind of sample (Cl−, , , Br−) as well as the effect of humic substances have been analyzed. Differences in the extraction efficiency were observed when organic ligands were presented in the samples. These differences allow the selective separation and quantification of the non-labile copper fraction in natural waters.