Studio geochimico ambientale e identificazione del grado di inquinamento da metalli pesanti nei suoli dell’area Domizio - Flegreo
Grezzi, Giuseppe (2008) Studio geochimico ambientale e identificazione del grado di inquinamento da metalli pesanti nei suoli dell’area Domizio - Flegreo. [Tesi di dottorato] (Inedito)
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The Littoral Domizio – Flegreo located along the north coastal zone of the Campania region (Italy) extends for about 855 Km2. We have analyzed soils for their content of heavy metals in order to study the relative impact of natural and anthropogenic sources. We collected 179 soil surface samples (5-15 cm depth) and produced maps showing the distribution of heavy metals in the soils. The soils point to the influence of two volcanic areas (Campi Flegrei, and M. Roccamonfina): the highest contents of Fe, U, Th, V, Ba, Ti, Al, Tl and Ga are mainly found in these two areas. In some cases, the contents exceed the maximum allowable values as stated by Italian law Dlgs 152/2006.The high values of such heavy metals are potentially dangerous for human health. Pb and As, for example, have very high concentrations: 15% of the 179 sites exceed the maximum allowed for residential areas (Pb=100 mg/Kg). The area between Castelvolturno and Mondragone has Pb contents between 100-328 mg/Kg; similar contents are found in samples from Sessa Aurunca and Qualiano. Anthropogenic sources related to automobile traffic and human activities (industrial lead) are likely the main causes for the Pb concentrations higher than 100 mg/Kg. The maximum content of As in soils for non-residential areas is 50 mg/Kg, and this limit is exceeded in the Francolise agricultural area (65 mg/Kg), suggesting that anthropogenic sources may have influenced the soils in areas used for vineyards. Also, near Francolise, Villa Literno, Giugliano, Quarto, and Bacoli, the values of As are higher than the residential limit (20 mg/Kg). Lead isotope compositions of soils known to contain anomalously high values of heavy metals were measured in order to determine the sources of the lead and, by inference, sources of arsenic. We have also collected groundwater samples from the same area. Acid-leach compositions of the soils represent lead that is adsorbed to mineral surfaces (anthropogenic component?), whereas residue compositions may reflect bedrock. Labile lead (acid-leach fractions) from the soils shows a range in compositions of about 207Pb/206Pb=0.8275 to 0.8486, 208Pb/206Pb=2.0488 to 2.0873; values vary and decrease with depth. The range in lead isotope ratios in the soil profiles is generally consistent with multiple sources that include anthropogenic lead. Surface samples from Giugliano (urban area) have Pb isotopic values closer to the composition of fuel and industrial lead used in Italy. Surface samples from Mondragone and Cancello Arnone (sub-rural area) have the lowest Pb isotopic ratios and suggest that the geogenic or natural component characterizes the lead isotopic trend in these areas and argue against a major contribution of Pb from human activities.
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