1,720,988 research outputs found
Holocene mountain forest changes in central Mediterranean: Soil charcoal data from the Sila Massif (Calabria, southern Italy)
No full textSoil charcoal analysis was performed on soil profiles excavated in the area of Cecita Lake on the Sila Massif (Calabria, southern Italy). Charcoals identification, combined with a good number of radiocarbon dating and the pedological analysis of the soils, allowed drawing a detailed history of the Holocene vegetation changes in the area. Five periods characterised by high concentration of radiocarbon dates – mirroring increased fire activity – are documented at ca. 10400-9000 BP, 8200-7200 BP, 5100-3700 BP, 3300-2400 BP and 600 BP to the present. Furthermore, a severe environmental change took place between the Middle Bronze Age and the Final Bronze Age/Iron Age (ca. 3600 to 3000 BP), when the mixed deciduous oak-silver fir woodland, which dominated the landscape until the Early Bronze Age, declined and was substituted by a Calabrian pine forest or by an open landscape. Available climate, pollen and historical/archaeological data are taken into account to investigate the possible causes of the detected environmental change and of the periods of increased fire activity. If climate seems to play a role in the fire regime during the first part of the Holocene, human action seems to be the triggering factor in the environmental change and the fire regime during the Late Holocene
Effects of source rocks, soil features and climate on natural gamma radioactivity in the Crati valley (Calabria, Southern Italy)
No full textradioactivityin terms of spatial and temporal variability, was aimed to characterize the background levels ofnatural radionuclides in soil and rock in the urban and peri-urban soil of a southern Italy area; to quantify their variations due to radionuclide bearing minerals and soil properties, taking into account nature andextent of seasonality influence. Its main novelty is taking into account the effect of climate in controlling natural gamma radioactivity as well as analysing soil radioactivity in terms of soil properties and pedogenetic processes.In different bedrocks and soils, activities of natural radionuclides (238U, 232Th 4 K) and total radioactivitywere measured at 181 locations by means of scintillation gamma-ray spectrometry. In addition, selected rocks samples were collected and analysed, using a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS) and an X-Ray Powder Diffraction (XRPD), to assess the mainsources of radionuclides. The natural-gamma background is intimately related to differing petrologicfeatures of crystalline source rocks and to peculiar pedogenetic features and processes. The radioactivitysurvey was conducted during two different seasons with marked changes in the main climatic characteristics,namely dry summer and moist winter, to evaluate possible effects of seasonal climatic variations and soil properties on radioactivity measurements. Seasonal variations of radionuclides activities show their peak values in summer. The activities of 238U, 232Th and 4 K exhibit a positive correlation with the air temperature and are negatively correlated with precipitations
Modelling seasonal variations of natural radioactivity in soils: a case study in southern Italy
No full textThe activity of natural radionuclides in soil has become an environmental concern for local public and national authorities because of the harmful effects of radiation exposure on human health. In this context, modelling and mapping the activity of natural radionuclides in soil is an important research topic. The study was aimed to model, in a spatial sense, the soil radioactivity in an urban and peri-urban soils area in southern Italy to analyse the seasonal influence on soil radioactivity. Measures of gamma radiation naturally emitted through the decay of radioactive isotopes (potassium, uranium and thorium) were analysed using a geostatistical approach to map the spatial distribution of soil radioactivity. The activity of three radionuclides was measured at 181 locations using a high-resolution γ-ray spectrometry. To take into account the influence of season, the measurements were carried out in summer and in winter. Activity data were analysed by using a geostatistical approach and zones of relatively high or low radioactivity were delineated. Among the main processes which influence natural radioactivity such as geology, geochemical, pedological, and ecological processes, results of this study showed a prominent control of radio-emission measurements by seasonal changes. Low natural radioactivity levels were measured in December associated with winter weather and moist soil conditions (due to high rainfall and low temperature), and higher activity values in July, when the soil was dry and no precipitations occurred
Studying the relationship between water-induced soil erosion and soil organic matter using Vis–NIR spectroscopy and geomorphological analysis: A case study in southern Italy
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Time spans of soil formation and late Pleistocene-Holocene climate changes in the Somma-Vesuvius volcano area, southern Italy
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