Heavy metal transport and evolution of atmospheric aerosols in the Antarctic region.

Suspended particulate matter (SPM) measurements and backward air mass trajectory analysis using the HYSPLIT model were performed to better understand the main sources and transport pathways of heavy metals in atmospheric aerosols reaching the Antarctic region. Field campaigns were carried out during the austral summer 2016-2017 at the "Gabriel de Castilla" Spanish Antarctic Research Station, located on Deception Island. Aerosols were deposited in an air filter through a low-volume sampler and chemically analysed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The study of air masses and high enrichment factor values of several elements (Hf, Zr, As, Cu, Sn, Zn, Pb) together with their correlations (Hf/Zr, V/As, Ti/Mn and Cu/Sn) suggests a potentially significant role of three main sources in this area: remote maritime traffic, local petrol combustion (generators and/or tourist cruises), and remote/local crust. Additionally, the investigation of atmospheric flow patterns through backward trajectory analysis revealed that Hf/Zr correlation was related to a remote crustal origin, V/As to anthropogenic local pollution, Ti/Mn to terrestrial inputs on the island and Cu/Sn to remote anthropogenic sources. Overall, the present study demonstrates the existence of anthropogenic pollution at this remote site from distant as well as local sources following the Antarctic circumpolar wind pattern.

Quantification of particulate matter, tracking the origin and relationship between elements for the environmental monitoring of the Antarctic region.

The present work reports on the analysis of atmospheric aerosols in the Antarctic region, Deception Island, collected during austral summer 2016-2017 by field measurements carried from Gabriel de Castilla Spanish Research Station. A low-volume sampler was used to capture the aerosols depositing them onto the air filters. A chemical analysis of the samples using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) provided the total carbon (TC), organic carbon (OC), elemental Carbon (EC) and elements such as Al, Ca, Fe, K, Mg, Na, P, S, Cu, Pb, Sr, Ti, Zn and Cr. The average mass concentration of particulate matter (PM10) originated by natural and anthropogenic activities was calculated as 10 ±â€¯4 µg/m3, although values such as 28.2 µg/m3 were also obtained which is very high even when compared to other places in the coast of the Antarctic region. In addition, high enrichment factors have been found for elements such as Pb, Cr, Cu and Zn showing a remote anthropogenic contribution to particulate matter in this region. Correlations were found between Na, Mg, Ca, Al, Ti and S, where Na/Mg displayed the influence of marine environments, S correspond to volcanic activities, Ca to penguin colonies and influence of sea whereas Al/Ti indicated the crustal origin. Polar contour graphical maps were obtained from meteorological data using chemometrics methods, which allowed reproducing wind maps revealing the distribution of the aerosols and possible emission sources of different elements in the area. Given that this island has not been previously studied for atmospheric contamination, this work provides an interesting insight about the site-specific characteristics of particulate matter.

Qualitative and quantitative analysis of milk for the detection of adulteration by Laser Induced Breakdown Spectroscopy (LIBS).

The present work focuses on the development of a fast and cost effective method based on Laser Induced Breakdown Spectroscopy (LIBS) to the quality control, traceability and detection of adulteration in milk. Two adulteration cases have been studied; a qualitative analysis for the discrimination between different milk blends and quantification of melamine in adulterated toddler milk powder. Principal Component Analysis (PCA) and neural networks (NN) have been used to analyze LIBS spectra obtaining a correct classification rate of 98% with a 100% of robustness. For the quantification of melamine, two methodologies have been developed; univariate analysis using CN emission band and multivariate calibration NN model obtaining correlation coefficient (R2) values of 0.982 and 0.999 respectively. The results of the use of LIBS technique coupled with chemometric analysis are discussed in terms of its potential use in the food industry to perform the quality control of this dairy product.

Classification of red wine based on its protected designation of origin (PDO) using Laser-induced Breakdown Spectroscopy (LIBS).

This work reports on a simple and fast classification procedure for the quality control of red wines with protected designation of origin (PDO) by means of Laser Induced Breakdown Spectroscopy (LIBS) technique combined with Neural Networks (NN) in order to increase the quality assurance and authenticity issues. A total of thirty-eight red wine samples from different PDO were analyzed to detect fake wines and to avoid unfair competition in the market. LIBS is well known for not requiring sample preparation, however, in order to increase its analytical performance a new sample preparation treatment by previous liquid-to-solid transformation of the wine using a dry collagen gel has been developed. The use of collagen pellets allowed achieving successful classification results, avoiding the limitations and difficulties of working with aqueous samples. The performance of the NN model was assessed by three validation procedures taking into account their sensitivity (internal validation), generalization ability and robustness (independent external validation). The results of the use of a spectroscopic technique coupled with a chemometric analysis (LIBS-NN) are discussed in terms of its potential use in the food industry, providing a methodology able to perform the quality control of alcoholic beverages.

New classification scheme for ozone monitoring stations based on frequency distribution of hourly data.

According to European Union (EU) legislation, ozone (O3) monitoring sites can be classified regarding their location (rural background, rural, suburban, urban) or based on the presence of emission sources (background, traffic, industrial). There have been attempts to improve these classifications aiming to reduce their ambiguity and subjectivity, but although scientifically sound, they lack the simplicity needed for operational purposes. We present a simple methodology for classifying O3 stations based on the characteristics of frequency distribution curves which are indicative of the actual impact of combustion sources emitting NO that consumes O3 via titration. Four classes are identified using 1998-2012 hourly data from 72 stations widely distributed in mainland Spain and the Balearic Islands. Types 1 and 2 present unimodal bell-shaped distribution with very low amount of data near zero reflecting a limited influence of combustion sources while Type 4 has a primary mode close to zero, showing the impact of combustion sources, and a minor mode for higher concentrations. Type 3 stations present bimodal distributions with the main mode in the higher levels. We propose a quantitative metric based on the Gini index with the objective of reproducing this classification and finding empirical ranges potentially useful for future classifications. The analysis of the correspondence with the EUROAIRNET classes for the 72 stations reveals that the proposed scheme is only dependent on the impact of combustion sources and not on climatic or orographic aspects. It is demonstrated that this classification is robust since in 87% of the occasions the classification obtained for individual years coincide with the global classification obtained for the 1998-2012 period. Finally, case studies showing the applicability of the new classification scheme for assessing the impact on O3 of a station relocation and performing a critical evaluation of an air quality monitoring network are also presented.

Industrial sources of primary and secondary organic aerosols in two urban environments in Spain.

In urban areas, primary and secondary organic aerosols are typically considered to originate from vehicular traffic emissions. However, industrial emissions within or in the vicinity of urban areas may also be significant contributors to carbonaceous aerosol concentrations. This hypothesis was tested and validated in two urban areas in Spain. The observed unusual dominance of organic carbon (OC) over elemental carbon (EC), the analysis of the variability of OC, EC and OC/EC and their correlation with transport patterns suggested the presence of OC sources associated with industrial activities. A methodology based on chemical speciation of particulate matter (PM) followed by the application of receptor modelling techniques allowed for the identification of the specific industrial sources of OC, which were linked to primary OC emissions from a grain drying plant (cereal) and to secondary OC formation from paper production activities (paper mills), as well as from urban sources and biogenic emissions. This work presents an integrated approach to identifying and characterizing of industrial sources of carbonaceous aerosols in urban areas, aiming to improve the scarce body of literature currently available on this topic.

Discrimination of organic solid materials by LIBS using methods of correlation and normalized coordinates.

The methods of linear and rank correlation and normalized coordinates (MNC) have been applied to the identification of organic solid materials with a very similar chemical composition by laser-induced breakdown spectroscopy (LIBS). The present study evaluated these three statistical methods using an Echelle spectrometer coupled with an intensified charge-coupled device (ICCD). Moreover, three instrumental parameters (laser pulse energy, delay time and integration time) were evaluated in terms of their influence on the signal-to-noise ratio of carbon and hydrogen emission lines. The probability of a right identification can be estimated by means the described methods in this paper. Methods of correlation provide better identification and discrimination than normalized coordinates at a 95% confidence level.

Micro-determination of iron in pharmaceutical preparations by image scanning and computational quantification.

Iron has been quantified in pharmaceutical preparations by developing red spots pursuant to interaction of Fe(II) ions in the sample with 1, 10-phenanthroline on TLC plate. Soon after, TLC was scanned on a flatbed scanner and the image was transferred to the computer. Color intensity of the spot was computationally quantified with the help of native software developed for this purpose. The conditions were optimized and the results were compared with a reference method.

Screening of antimony in PVC by solid sampling-graphite furnace atomic absorption spectrometry.

The development of two-stage control systems is of great interest when a large number of samples are analysed in order to check that they fulfil certain requirements. If the first stage is carried out using an inexpensive method with a high throughput which makes it possible to filter out the majority of the samples that fulfil the requirements, the procedure is not only less time-consuming but also more economical. Direct determination of metals in solid samples by graphite furnace atomic absorption spectrometry (GFAAS) appears, in principle, to be a suitable analytical technique for screening purposes since it provides sufficiently reliable results in a reasonably short time. In this paper it is applied with satisfactory results to antimony content control in a PVC sample.

Erbium determination in preforms of optical fibres by inductively coupled plasma-atomic emission spectrometry.

Erbium which is used in the composition of heavy metal fluoride optical fibres was determined in preforms of these materials by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The new analytical procedure developed comprises: solid sample dissolution, via an alkaline fusion with sodium carbonate, and acid leaching with dilute hydrochloric acid, and measurements of emission intensities of 337.276 nm. This method has a detection limit of 31 ng/ml and a reproducibility of 0.90% r.s.d.

Determination of chloride at picogram levels by molecular fluorescence in a graphite furnace.

Chloride was determined at nanogram levels by adding excess of indium to the sample introduced into a graphite furnace and measuring the laser induced molecular fluorescence of indium chloride. The diatomic molecules of indium chloride were excited by a pulsed dye laser at 267 nm and fluorescence was measured at 359 nm. The effects of various parameters including amount of indium added, furnace thermal conditions and presence of concomitants were also studied. A linear calibration in the range of 0.025-1.25 ng and a detection limit of 17 pg of chloride were obtained under optimum conditions. The analytical usefulness of the method was checked by determining the chloride content in National Institute of Standards and Technology, Standard Reference Materials 1571a and 1571b Orchard Leaves.

Bromide determination at nanogram levels by laser-excited molecular fluorescence spectroscopy in a graphite furnace.

Bromide was determined at nanogram levels by introducing the sample with excess aluminum into a graphite furnace and measuring the laser-excited molecular fluorescence of aluminum bromide. Experimental parameters including excitation and fluorescence wavelengths, thermal conditions and aluminum concentration were optimized. Effects of concomitant ions and of barium hydroxide concentration, as a matrix modifier, have also been checked. The analytical reliability of the described procedure was checked by determining the bromide content in a standard reference material.