Marcos A. E. Chaparro

Review of magnetism and heavy metal pollution studies of various environments in Argentina

In recent years, the number of studies of pollution and magnetic proxies for environmental pollution in developed countries, especially European and North American countries, has gradually increased from the 80’s to date. Despite this trend that shows a positive interest in taking care of the environment and researching into the environmental impact of several human activities, pollution studies in Latin American countries have been reducing in number. Moreover, studies of magnetic proxies for pollution are scarce; in particular, studies of this nature has been carried out in Argentina over the past few years by Chaparro and coworkers. Studies of magnetic enhancement in soils due to the burning mechanism are discussed and the results of burnt soils affected by fires of different nature and natural soils are compared, taking into account their magnetic carriers. Nevertheless, this article deals mainly with the first studies of magnetic proxies for pollution conducted in a province in Argentina. Soils, lagoon and stream sediments from three areas were studied. These areas comprise La Plata, Chascomús, and Tandil districts. The influence of pollution was investigated in Tandil and La Plata, revealing magnetic enhancement and the presence of pollutants only in Tandil soils. On the other hand, stream and lagoon sediments were studied in La Plata and Chascomús. Magnetic carriers and the contents of some heavy metals were identified and investigated in both areas separately. Magnetic parameters show distinctive points and wide areas affected by pollution. Furthermore, this magnetic inference is supported by high contents of heavy metals, especially lead and zinc. Finally, a new statistical study of multiple correlation analysis concerning data from La Plata and Chascomús areas was tried in order to investigate the existence of a linear relation between sets of several magnetic parameters and several chemical variables.

Magnetic screening and heavy metal pollution studies in soils from Marambio Station, Antarctica

Abstract Magnetic screening as a cost-effective and non-time-consuming approach has been successfully carried out in Marambio soils and seems to be a suitable method for contamination assessment in Antarctic areas. Ferromagnetic minerals are found in most samples, and magnetite-like carriers are especially dominant in samples collected near pollution sources. Lead and zinc are the main trace elements that have adversely impacted on some areas in this station, both are end products from different pollution sources derived from fuel combustion and residues, solid waste, paints, etc. The correlation results between magnetic and chemical variables show moderate relationships varying from 0.409 to 0.663; this fact supports the use of magnetic parameters, such as magnetic susceptibility and bivariate ratios, for pollution monitoring. The magnetic properties, heavy metal contents, and related maps of these soils can be considered as a reference in the area for future temporal and/or spatial work.

Biomonitors of urban air pollution: Magnetic studies and SEM observations of corticolous foliose and microfoliose lichens and their suitability for magnetic monitoring

This study explored the suitability of available lichen species as air pollution biomonitors and assessed their potential for magnetic monitoring in cities. Several lichens on tree bark were collected in urban and industrial sites from Tandil city, as well as control sites. The results showed that magnetite-like minerals were the main magnetic carriers in all sites and samples. However, the concentration varied between clean and polluted sites. In addition, magnetic-grain size-distribution showed clear differences between sites. Observations by scanning electron microscopy showed different particles in a variety of shapes and grain sizes; moreover, the presence of iron oxides and several toxic elements was detected by energy dispersive spectroscopy analysis. Although eleven lichen species were identified that appeared suitable for use as air-pollution monitors, three of them, Parmotrema pilosum, Punctelia hipoleucites and Dirinaria picta, occurred more frequently in the area, thus constituting appropriate species for future monitoring in the study area.

An interval fuzzy model for magnetic monitoring: estimation of a pollution index

In this contribution, a methodology is reported in order to build an interval fuzzy model for the pollution index PLI (a composite index using relevant heavy metal concentration) with magnetic parameters as input variables. In general, modelling based on fuzzy set theory is designed to mimic how the human brain tends to classify imprecise information or data. The “interval fuzzy model” reported here, based on fuzzy logic and arithmetic of fuzzy numbers, calculates an “estimation interval” and seems to be an adequate mathematical tool for this nonlinear problem. For this model, fuzzy c-means clustering is used to partition data, hence the membership functions and rules are built. In addition, interval arithmetic is used to obtain the fuzzy intervals. The studied sets are different examples of pollution by different anthropogenic sources, in two different study areas: (a) soil samples collected in Antarctica and (b) road-deposited sediments collected in Argentina. The datasets comprise magnetic and chemical variables, and for both cases, relevant variables were selected: magnetic concentration-dependent variables, magnetic features-dependent variables and one chemical variable. The model output gives an estimation interval; its width depends on the data density, for the measured values. The results show not only satisfactory agreement between the estimation interval and data, but also provide valued information from the rules analysis that allows understanding the magnetic behaviour of the studied variables under different conditions.

AN ALTERNATIVE EXPERIMENTAL METHOD TO DISCRIMINATE MAGNETIC PHASES USING IRM ACQUISITION CURVES AND MAGNETIC DEMAGNETISATION BY ALTERNATING FIELD

Separation of different magnetic phases in natural samples composed by a mix of several magnetic minerals become necessary in rock magnetism in order to identify and describe the main magnetic carriers. However, this task may be difficult to carry out successfully. The goal of the proposed method in this paper is to determine and discriminate experimentally magnetic (soft and hard) phases in synthetic and natural samples. The present method uses two different magnetic techniques, isothermal remanent magnetisation acquisition and magnetic demagnetisation alternately. After the entire process of induced remanent magnetisation and demagnetisation is performed, three residual isothermal remanent magnetisation curves are obtained. This discrimination is achieved by using as filters (sorter) different peak values for alternating demagnetising fields. Well-known pure and mixed synthetic iron oxides (magnetite and hematite) were firstly studied to investigate and corroborate the reliability of our experimental method, obtaining successful results. Subsequently, natural samples containing soft and hard minerals (magnetite, hematite, goethite, etc.) from stream-sediments, soils and a mine were also studied. Comparisons with other purely numerical methods were carried out, yielding a good agreement among them. Our method is more time-consuming than others, but separation of individual magnetic curves is achieved by an experimental procedure, which is more realistic. It is also possible to apply this method to backfield isothermal remanent magnetisation measurements obtaining valuable information of HCR and S-ratio for each phase.

Magnetic, chemical and radionuclide studies of river sediments and their variation with different physiographic regions of Bharathapuzha River, southwestern India

Bharathapuzha River is the second longest river in southwest India, where three physiographic regions show a distinctive spatial variation and their bed sediments can be considered environmental hosts for end-products generated by human activities and natural radionuclide components. Thus, the study of this river sediments in SW India is important not only because they are recorders of adverse human impacts (e.g., intense agricultural activities and urban pollution), but also because of their potential health hazards due to their common use as construction materials. Magnetic (e.g., magnetic susceptibility, anhysteretic remanent magnetisation and isothermal remanent magnetisation), radionuclide (226Ra, 232Th and 40K) and chemical (trace and major elements) measurements were carried out in bed sediment samples along 33 sites from the uppermost catchment downstream. Magnetic measurements show the dominance of ferrimagnetic minerals; their concentration ranges widely along the river and between regions, showing up to 7-fold higher values for concentration-dependent magnetic parameters, e.g., mean values of saturation of isothermal remanent magnetisation acquisition are 67.9 and 9.4 × 10-3 Am2 kg-1 for highland and lowland regions, respectively. Multivariate statistical analyses show the existence of relationships between magnetic, radioactivity and chemical variables. In particular, magnetic concentrationdependent parameters are significantly correlated with radioactivity variables 40K and 226Ra (with concentrations about 20% higher than the worldwide mean values), as well as with some elements: Fe, Ca and P. Such analyses also show differences between physiographic regions where samples from the highland (and lowland) region are well grouped showing higher (lower) magnetic concentrations and lower (higher) coercivity minerals. The spatial variation of magnetic parameters along the river can be related to the influence of both natural sources and human activities, i.e. urbanisation and intense agricultural activities. In this sense, environmental magnetism data provide very useful tools to investigate adverse human activities occurring in the riverine environment.

Evaluation of natural radioactivity and its associated health hazard indices of a south Indian river

The activity concentration of the natural radionuclides (226)Ra, (232)Th and (40)K was measured for sediment samples collected from thirty-three different locations along the Bharathapuzha river basin by using high-resolution gamma-ray spectrometry. The concentrations of the natural radionuclides were found to vary from location to location, and their mean values are 19.6, 82.87 and 19.44% higher than the worldwide mean values of (226)Ra, (232)Th and (40)K, respectively. The value of (232)Th was found to be higher than that of (226)Ra in 82% of the samples collected for this study. The calculated values of indoor gamma dose rate (DIN) ranged between 89.55 and 194.24 nGy h(-1), and the overall mean value is 63.2% higher than the recommended safe and criterion limit by UNSCEAR. The internal and external hazard indices (H(in) and H(ex)), the representative gamma index and alpha index (I(gamma) and I(alpha)), the annual gonad dose equivalent (AGDE) and the excess lifetime cancer risk (ELCR) were also calculated and compared with the international recommended values. Multivariate statistical analyses were also carried out to determine the relation between the natural radionuclides and various radiological parameters.

A high-resolution palaeoclimate record for the last 4800 years from lake la Brava, SE pampas plains, Argentina

Resumen Los cambios climaticos son reflejados en las variaciones de diferentes parametros. Las secuencias sedimentarias de lagos son buena fuente de esta informacion debido a que proveen grabaciones continuas y detalladas de cambios paleoclimaticos.Para determinar los cambios en el clima al SE de la llanura Pampeana, se presentan estudios de magnetismo de rocas realizados en un testigo colectado del fondo de la Laguna La Brava (Argentina). Tambien se midieron contenidos totales de sulfuro, carbon organico e inorganico (TS, TOC y TIC), elementos alcalinos, metales pesados y livianos, y cambios en las comunidades de vegetacion. Se realizaron cinco determinaciones de edades radiocarbonicas y se calcularon las edades calibradas. La tasa promedio de acumulacion de sedimento es 1.3 mm/ano y la secuencia representa los ultimos 4800 anos en edades calibradas (cal. BP).El objetivo principal fue reconstruir el balance M. A. Irurzun * C. S. G. GogorzaA. M. SinitoM. A. E. ChaparroInstituto de Fisica Arroyo SecoUniversidad Nacional del Centro de la Provincia de Buenos AiresPinto 399, 7000 Tandil, Argentina

Magnetic assessment and pollution status of beach sediments from Kerala coast (southwestern India)

Natural and anthropogenic activities along the coastal region of densely populated Kerala may introduce hazardous components into the coastal environment. The present study aimed to investigate the sources and impacts of hazardous components in beach sediments by environmental magnetism methods as additional tools. Magnetic parameters (such as mass-specific magnetic susceptibility χ=-1.2-154.4×10-8m3kg-1) and ratios that describe the magnetic properties of minerals such as Fe-oxides, indicate variable concentration of mixtures of magnetite and hematite (magnetite/hematite). The direct significant relationships between the variables indicate that higher concentration magnetic parameters are associated with higher radionuclides and metal contents. Magnetic properties and multivariate statistical analyses evidence the presence of contrasting groups defined only using a reduced number of magnetic variables. One of these groups, the central area of the Kerala coastline, showed the highest magnetic concentrations of mixtures of magnetite/hematite and higher values (up to 6.7) of pollution load index because of extensive anthropogenic activities.

Sedimentary analysis and magnetic properties of Lake Anónima, Vega Island

Abstract During the summer Lake Anónima experiences important changes in salinity and lake level fluctuations. Physicochemical data and field observations indicate that evaporative processes are dominant and that the water inflow is mainly provided by snow meltwater and streams. A multiproxy analysis of data from lake bottom sediments suggests that the main surface stream located south-west of the lake controls the clastic input and the spatial variation of sediment composition. Through an integrated analysis (magnetic, X-ray diffraction and Fourier transform infrared spectroscopy studies) magnetite and greigite minerals were identified in these lake sediments. Such ferrimagnetic minerals have ultra-fine grain sizes (<0.1 μm). Magnetic parameters and non-magnetic variables analysed by multivariate statistics reveal significant differences between silt facies (e.g. mass-specific susceptibility χ=109.6×10-8 m3 kg-1, remanent coercivity Hcr=49.2 mT and total organic carbon (TOC)=1.11%) and sand facies (e.g. χ=82.1×10-8 m3 kg-1, Hcr=44.7 mT and TOC=0.70%), and four recent depositional sub-environments were identified and characterized in Lake Anónima. This multiparameter analysis contributes to the understanding of present-day lacustrine dynamic and sedimentary processes. Lake Anónima may provide a useful analogue for the interpretation of other lacustrine basins in the Antarctic region.