Mónica B. Alvarez

Evaluation of sorption and desorption characteristics of cadmium, lead and zinc on Amberlite IRC-718 iminodiacetate chelating ion exchanger

A chelating type ion exchange resin (Amberlite IRC-718), containing iminodiacetate groups as active sites, has been characterized regarding the sorption and subsequent elution of Cd, Zn and Pb, aiming to metal preconcentration from solution samples of different origins. The methodology developed is based on off-line operation employing mini columns made of the sorbent. The eluted metals were determined by flame atomic absorption spectrometry. The effect of column conditioning, influent pH and flow rate during the sorption step, and the nature of the acid medium employed for desorption of the retained metals were investigated. Working (breakthrough) and total capacities were measured under dynamic operating conditions and the results compared with those obtained with Chelex-100, a resin extensively employed for analytical preconcentration. Structural information on the complexation of metals by the chelating groups was obtained by Fourier Transform infrared spectrometry. The analytical response of the Amberlite sorbent was assessed for the analysis of water samples and digestates of marine sediments.

Three-way multivariate analysis of metal fractionation results from sediment samples obtained by different sequential extraction procedures and ICP-OES

Three typical schemes for metal fractionation were applied to analyse coastal surface sediment samples from Bahía Blanca estuary, where an important industrial emplacement is located. Also, three certified reference materials for total metal concentrations were analysed. The studied metals were cadmium, chromium, copper, lead and zinc because of their hazardous potential and related abundance in the estuary. The concentration of metals was determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). A three-way multivariate analysis was performed in order to obtain a better visualization of the experimental data. The extracted information was used to evaluate the equivalence among the results obtained by the three sequential extraction schemes. The data were analysed by parallel factor analysis (PARAFAC). PARAFAC models with two factors describe appropriately the data sets (explained variance about 54% and core consistency of 100%). The multivariate decomposition showed that the three applied schemes are able to describe equally well the behaviour of the metals in the different sediment fractions.

Ionic liquid mediated extraction, assisted by ultrasound energy, of available/mobilizable metals from sediment samples.

A new extraction method for metals from sediment samples was developed. In this procedure, the chelating agent EDTA was combined with a minimal amount of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (Bmim[BF4]), assisted by ultrasound energy. The available analytes -Cd, Cr, Cu, Ni, Pb and Zn- were extracted under optimal conditions for a 12.5 ratio (extractant volume/sample mass) with 0.005molL-1 EDTA solution, 0.1molL-1 NaHCO3, 5.0mmolL-1 Bmim[BF4] and 7.0min of sonication time, using an ultrasonic bath (output power of 160W). The best extractions were obtained with 100W (power dissipated in the liquid). These conditions were obtained applying the univariate method. It is important to highlight that the conventional method (extraction with 0.05molL-1 EDTA solution only) consumes 6h to extract available metals from sediment samples selectively, and with the proposed procedure the extraction time is noticeable reduced to 7.0min. Extractable metal concentrations obtained were measured by flame atomic absorption spectrometry. The results showed good agreement with those obtained by the conventional method using a Students paired t-test.

Tracking polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in sediments and soils from the southwest of Buenos Aires Province, Argentina (South eastern part of the GRULAC region).

PCBs and PBDEs (7 and 10 congeners, respectively) were analyzed in four coastal surface sediments collected from the northern shore of Bahía Blanca estuary and in nine soils from different locations of Bahía Blanca city and the surrounding region (Southwest of Buenos Aires Province, Argentina). Sediment samples showed PCBs(Σ7) concentrations ranged from 0.61 to 17.6ngg-1 (dry weight=dw) and PBDEs(Σ10) from 0.16 to 2.02ngg-1 dw, whereas in soil samples ranged from 0.04 to 1.67ngg-1 dw for PCBs(Σ7) and 0.04 to 10.7ngg-1 dw for PBDEs(Σ10). The highest concentrations of both chemicals were detected in the urban and industrial/port areas showing a dominance of the higher chlorinated PCB congeners: in sediments for PCB-180 (56±33%) and PCB-153 (11±6%); and in soils for PCB-138 (23±3%), PCB-153 (22±2%) and PCB-180 (18±7%). In contrast, lower chlorinated PCB congeners were predominant at more distant sites; in sediments for congeners PCB-28 (33±4%) and PCB-52 (14.5±0.2%); and in soils PCB-28 (56±14%) and PCB-52 (33±19%). PBDE-209 (high brominated PBDE) showed the highest relative abundance in both sample types i.e., sediment (94±7%) and soil (80±12%). These findings can be considered lower or similar when compared with other sites of the world, and are likely associated with anthropogenic activities in their surrounding area, which has experienced a fast industrial growth in the last decade. This is the first investigation of PBDEs levels in the whole study area and of PCBs in soils from the Bahía Blanca city and surrounding region. This article provides new and useful information on POP levels in the South eastern part of the GRULAC region.

Rapid characterisation of agro-industrial effluents for environmental fate by UV–visible and infrared spectroscopy from fractions obtained by centrifugation

ABSTRACT Agro-industrial systems (e.g. dairy farms, feed lot, pig breeding and food processing plants) provide large quantity of organic wastes that could be recycled within the productive systems. However, the basic chemical characterisation is not enough to predict the effect that they may generate on the environment. In this study, a centrifugation process was applied at various speeds between 3000 and 15,000 rpm and carried out separately on two different livestock effluents (dairy farm and pig anaerobic digestate), in order to obtain supernatants and precipitates, which were studied separately. The more water soluble fractions, with lighter components and/or simpler structures, remained as liquid supernatants, while the more complex fractions, with higher molecular weight and/or water insoluble fractions, constituted the solid precipitates. An increase in the centrifugation rate did not produce the differential precipitation of dissimilar functional groups. Hence, 5000 rpm was the most adequate velocity since it generated clear supernatants without denaturation of the organic matter. A basic cost-effective chemical analysis, complemented with ultraviolet–visible and Fourier transform infrared spectroscopy, enables a set of properties to be established qualitatively and quickly for the multiple components of the organic matter for its later use as fertilisers or amendments. This rapid and economical technique allows for a characterisation prior to the reuse of the effluents, which is necessary to optimise their application and avoid environmental problems.

Organotin compounds in Brachidontes rodriguezii mussels from the Bahía Blanca Estuary, Argentina

Levels of tributyltin and its breakdown compounds, including the first record of monobutyltin (MBT) in history for Latin America, were determined in native mussels (Brachidontes rodriguezii) by means of CG-MS, after extraction/derivatization assisted by ultrasound. The samples were collected in 2013 in Bahía Blanca Estuary (Argentina) at 6 sites, which reflect different levels of maritime activities. Total butyltins (TBts = TBT+ DBT+ MBT) levels ranged from 19.64 to 180.57ng Sn g-1 dry weight. According to the Oslo-Paris commission, the results indicated that 73.9% of mussels could be under biological effects risks associated with TBT pollution. In accordance with the calculated bioaccumulation factors, approximately 56% of samples appeared to have accumulated TBT through the sediments. All sampling sites were shown to be impacted by organotin compounds (OTCs) showing variable levels through seasons, which could be related with the variation of the water temperature. Degradation index analyses suggested aged inputs of TBT possibly under a general degradation process at the area of study. In addition, the occurrence of DBT and MBT could not be uniquely attributed to the degradation pathway of the TBT; in fact, results outlined the possible contribution of some punctual and diffuse sources at the area such as proximity to plastic industries, industrial effluents, sewage outlets and domestic wastewaters.