Browse

You are looking at 91 - 100 of 793 items

Abstract

Lead is a frequent, potentially toxic pollutant of the urban environment. Its risk assessment in airborne particulate matter requires data both on its speciation and potential sources. In this paper we present results of a detailed mineralogical (XRD and TEM) and geochemical (selective chemical extractions and lead isotope ratio analyses) study of total suspended particulate (TSP) matter samplesfrom Budapest, Hungary, to fulfill these requirements.

Total lead concentrations showed significant enrichment in the studied TSP samples as compared to its geochemical background value. It could be associated with several host phases. The potentially mobile fraction of lead, which could also be harmful to humans, can be as high as 16% of the total lead. This is represented by Pb sorbed on the surface of clay minerals and in the form of carbonates (and sulfates). On the other hand, between 20 and 30% of total lead of TSP material is hosted by magnetite, a highly resistant mineral. However, its rapid oxidation during combustion processes to hematite and/or weathering in the acidifying urban environment to ferrihydrite, may result in the enhanced mobilization of lead.

The lead isotope composition of the TSP samples suggests the mixing of several sources for this metal, with slight variation among the sampling sites. Despite the phasing out of leaded gasoline, its contribution to the Pb content of the TSP was observed. Our data also supported that the presence of lead of gasoline origin decreases in the airborne TSP during the last decade in Budapest. Another important source for lead is found to be coal combustion linked to domestic and industrial heating. Lead isotope ratio data suggest additional source(s) for this metal, at least in certain localities, but further investigations are necessary to specify them.

Full access

Abstract

The muscle tissues of the Litopenaeus vannamei shrimp grown in ponds through organic and traditional (intensive) management show that δ13C values were similar amongst the shrimp. Shrimp grown in the traditional pond were enriched in 13C by 7‰ relative to the carbon isotope ratios of their feed. The differences in the carbon isotope ratios of shrimp and feed in the traditional pond shows that the feed is not the main carbon source for shrimp grown in the traditional intensive management. Using mass balance we calculate that feed in traditional culture contributes at most 13% of the shrimp's carbon biomass.

Full access

Abstract

Stable C isotope studies of the soil organic matter (SOM) have delineated areas with histories of vegetation change from C3 forest to C4 maize (Zea mays L.) agriculture and back to the contemporary C3 forest. The objectives of this study were to: (1) determine if land around El Kinel, Guatemala possessed a vegetative history of shifts from C3 forest to C4 maize agriculture in the past, (2) determine if 10 years of contemporary maize production is sufficient time to deposit an isotopic signature of C4 plants in the root zone (top 40 cm), and (3) to examine the extractable phosphorus concentrations and δ13C in soils of important archaeological features that included a midden, a burial, and two ancient reservoirs (aguadas). The lack of a shift in δ13C greater than 3.5‰ in the top 40 cm of the contemporary maize field suggested that continual maize cultivation of more than ten years is required to create an isotopic signature for maize agriculture. Carbon isotopic evidence was found in soil profiles to confirm that long-term agriculture was practiced by ancient Maya farmers at El Kinel. The man-made aguadas did not show isotopic shifts greater than 2.3‰ in any part of the profile, indicating they were used for other purposes not associated with C4 plant growth. The relatively low P (<30 mg kg−1) was found in soil at the same depth but at a distance of 30 cm from an ancient burial. The high P concentration (127 mg kg−1) found within millimeters of the bones implied that the P enrichment came from the remains but P remained fixed in the soil and did not migrate.

Full access

Abstract

Environmental historical analyses, including sedimentological, pedological, palynological, archeobotanical and phytolith analyses were carried out on samples derived from the Kadicsfalva/Cãdiseni archeological site. Our aim was to provide paleoenvironmental data to the archeological results in order to reconstruct the former milieu of the Gothic population, and to provide information regarding their environment management. At the end of the Pleistocene loess and alluvial loess developed from the eolian dust that accumulated on the wet surfaces of the Pleistocene sediments. The site provided favorable conditions to host a settlement and supports its long-term colonization owning to the riverside terrace surface location. The comparative analysis of the recent and the Gothic soil horizon proved that the recent soil horizon is over-utilized; its productivity can be maintained only by intensive fertilization and almost every one of its parameters is below the element and nutrient composition of the Gothic soil horizon.

Full access

Abstract

Ferromagnetic grains in airborne dust are important indicators of vehicle traffic, some industrial sources and combustion/heating. Settled dust consists mainly of diamagnetic material; therefore accessory ferromagnetic grains are readily indicated by magnetic measurements. In this paper settled dust samples collected on a monthly basis in the years 2008–2011 were studied. Non-destructive magnetic measurements were followed by geochemical and mineralogical analyses. In selected samples we identified airborne anthropogenic materials (e.g. silicate and magnetite spherules), minerals from the natural environment and organic material. Seasonally appearing materials (e.g. soot in winter, plant fragments and pollen in summer) increased the mass of the settled dust, but not the magnetic susceptibility. Thus, we realized that the generally interpreted mass susceptibility in environmental magnetic studies would not always appropriately characterize the magnetic pollution. In the interpretation we gave preference to total susceptibility because of its direct connection to the pollution, except in comparison with metal concentrations.

Trends in magnetic pollution were eventually analyzed for 19 sampling sites. Irrespective of the degree and source of the pollution the monthly variation curves of magnetic susceptibility exhibit a general maximum (March-April), followed by gradual decrease. A corresponding peak is observed in the amounts of dust. Both can be explained by re-suspension of dust settled in winter. The additional maxima in the mass of the dust (June and August, respectively) are probably due to contribution from vegetation and/or an artifact from algaecide. For three key sampling sites comparison was made between the concentrations of 12 metals and the respective mass susceptibilities and good linear correlation was found for Fe, Mn and Zn for all, for Cr, Cu, Pb, V, Ba, Sr and Zr for two sampling sites. Cd, which is enriched in all samples, does not correlate with the magnetic susceptibility.

Full access

Abstract

There is little data on the mineralogy of carbonate pedofeatures in the calcareous soils in Hungary which belong to the European prairie ecodivision. The aim of the present study is to enrich these data.

The mineralogical composition of the carbonate pedofeatures from characteristic profiles of the calcareous soils in Hungary was studied by X-ray diffractometry, thermal analysis, SEM combined with microanalysis, and stable isotope determination.

Regarding carbonate minerals only aragonite, calcite (+ magnesian calcite) and dolomite (+proto-dolomite) were identified in carbonate grains, skeletons and pedofeatures.

The values relating, respectively, to stable isotope compositions (C13, O18) of carbonates in chernozems and in salt-affected soils were in the same range as those for recent soils (latter data reported earlier). There were no considerable differences between the values for the carbonate nodules and tubules from the same horizons, nor were there significant variations between the values of the same pedofeatures from different horizons (BC-C) of the same profile. Thus it can be assumed that there were no considerable changes in conditions of formation.

Tendencies were recognized in the changes of (i) carbonate mineral associations, (ii) the MgCO3 content of calcites, (iii) the corrected decomposition temperatures, and (iv) the activation energies of carbonate thermal decompositions among the various substance-regimes of soils.

Differences were found in substance-regimes types of soils rather than in soil types.

Full access

Abstract

Stable carbon and oxygen isotope compositions of living Unio shells and oxygen isotope compositions of water samples were determined in order to demonstrate how the shells' compositions can reflect environmental conditions. With this information in hand, fossil shell fragments from a sedimentary section at Tiszapüspöki covering the period of about 3.5 to 10 ky BP were analyzed for their stable isotope as well as trace element compositions. Beside the determination of sedimentary facies effects on the geochemical compositions, the combined evaluation of isotopic and trace element records allowed us to detect past environmental changes at a millennial scale. The data indicate that the period of 6 to 8 ky BP was characterized by humid summers that — on the basis of comparison with an Alpine speleothem record — was associated with a generally warmer climate and increased winter precipitation in the Alps.

Full access

Abstract

In this paper we present sedimentological and geochemical data for a section of fluvial deposits from SE Hungary covering the period from about 20 to 5 ky BP. Major and trace element geochemistry of bulk sediments as well as stable C and O isotope compositions of the carbonate content indicate significant changes in depositional facies and/or sediment provenance as well as climate conditions. Variations in bulk sediment Sr, TiO2 and P2O5 concentrations were correlated with major climate change events following the Late Glacial Maximum that support the age model established on the basis of AMS 14C age data. Bulk sediment Sr concentrations and stable C and O isotope compositions of bulk sediment carbonate were determined by changes in denudation of carbonate rocks in the recharge area. The Sr and C-O isotope patterns show correlations with global temperature changes during the Pleistocene-Holocene transition. However, TiO2 and P2O5 contents show correspondence with humidity changes, suggesting variations in chemical weathering. In addition to the sedimentological effects, C and O isotope compositions of Unio crassus shell fragments show strong changes at the Pleistocene-Holocene transition, indicating that the bivalve shells can reflect climate conditions. On the other hand, shorter climate change events were difficult to track in the isotope records due to the competing fractionation processes. The combined evaluation of chemical and isotopic compositions revealed that beside the globally important Younger Dryas and Bølling/Allerød periods, the Ságvár-Lascaux interstadial was of local importance, in accordance with earlier studies.

Full access

In the present study the crustal structures of Nile Delta, including Greater Cairo province, and its surroundings, were evaluated using 3D forward gravity and magnetic modeling. The interpretation is also based on the seismic reflection results, well logs data and previous density models. The present results allow to improve the understanding of both the crustal thicknesses and density distributions between the sedimentary cover and the upper mantle in the study area.The high Bouguer anomalies near the Mediterranean coast are mainly caused by deep-seated structures. The crust beneath the Mediterranean coastal region is typically continental, with a thickness of 24 km beneath Rositta and Damitta branches, which increases toward the south. The Greater Cairo province has been modeled with maximum crustal thickness of ca. 34 km. The negative gravity anomalies with minimum values are due to the effect of sedimentary cover and/or basement relief geometry.The main results of this work suggest that the study area could be divided into three different distinctive tectonic zones according to their Moho depth and crustal structures. The southern zone (unstable shelf zone) which covers the Greater Cairo province is characterized by maximum crustal modeled thickness. It also represents the most seismically active tectonic zone in the study area. On the contrary the middle and northern zones show a thinned crustal layer and a correspondingly thicker sedimentary cover.Furthermore, the magnetic anomalies along the Greater Cairo, as deduced from the 3D magnetic modeling, are mainly caused by the upper crustal structures. In particular, the high magnetic anomalies of the southern part of the studied area are interpreted as related to variation in the basement relief near the surface, resulting from block faulting and/or compressional folds.In the northern region near the Mediterranean coastal area the highest magnetic susceptibility anomaly values is affected by the shallow smooth relief of the lower crustal layer. Finally, limited, shallow-seated basaltic intrusions were modeled beneath the western side of Nile Delta. The existence of these basaltic intrusions suggests that the study area was influenced by the opening of the Red Sea and/or Gulf of Suez during the Oligocene time.

Full access

In connection with the EURISGIC WP2 project the authors present those procedures which have been used to construct a map in cells on the electrical resistivity distribution in Europe at least till to the asthenosphere. The data are based on the deep magnetotelluric soundings published in the international literature. This map is the basis of the calculation of the induction risk endangering the electric network and communication systems.

Full access