The Alps and the Apennines both convey water and sediments to the Po river that is the most important fluvial system of the Italian Peninsula, characterized by a length of 650 Km, an hydrological basin of 74000 km2 and an average discharge of 47 Km3/yr. Major and trace elements, stable isotope composition of water and radiogenic strontium isotopes were used to characterize the sources and fluxes of solutes. Compared with the local meteoric isotopic signature, stable isotopes (delta18O between -10.8 and -9.2; deltaD between -70.0 and -65.4) reveal that most of the recharge occurs in the north-western part of the basin, i.e. conveyed mainly from the highlands. Although subordinate, carbonatic lithologies are preferentially involved in the weathering processes inducing the typical Ca-HCO3 hydrochemical facies and a specific strontium isotopic signature (87Sr/86Sr 0.7090-0.7092) that is intermediate between that of Mesozoic carbonates (0.707-0.708) and felsic igneous and metamorphic rocks (> 0.701). The data also provide insights on the erosion and denudation rates of the orogens bordering the basin. The observed TDS (average and median of 39 measurements are 268 and 292 mg/l, respectively) suggest that a solute flux in the order of 13*105 t/yr is transferred from the Po River toward the Adriatic Sea. A total erosion of 68*106 t/yr is estimated within the Po River drainage basin, assuming that solute represent a fraction (of ca 20%) of the weathering products. This estimation conforms to other recent investigations.
The river Po: geochemical fluxes and related insights on weathering processes and erosion rates
BIANCHINI, Gianluca;MARCHINA, Chiara;
2013
Abstract
The Alps and the Apennines both convey water and sediments to the Po river that is the most important fluvial system of the Italian Peninsula, characterized by a length of 650 Km, an hydrological basin of 74000 km2 and an average discharge of 47 Km3/yr. Major and trace elements, stable isotope composition of water and radiogenic strontium isotopes were used to characterize the sources and fluxes of solutes. Compared with the local meteoric isotopic signature, stable isotopes (delta18O between -10.8 and -9.2; deltaD between -70.0 and -65.4) reveal that most of the recharge occurs in the north-western part of the basin, i.e. conveyed mainly from the highlands. Although subordinate, carbonatic lithologies are preferentially involved in the weathering processes inducing the typical Ca-HCO3 hydrochemical facies and a specific strontium isotopic signature (87Sr/86Sr 0.7090-0.7092) that is intermediate between that of Mesozoic carbonates (0.707-0.708) and felsic igneous and metamorphic rocks (> 0.701). The data also provide insights on the erosion and denudation rates of the orogens bordering the basin. The observed TDS (average and median of 39 measurements are 268 and 292 mg/l, respectively) suggest that a solute flux in the order of 13*105 t/yr is transferred from the Po River toward the Adriatic Sea. A total erosion of 68*106 t/yr is estimated within the Po River drainage basin, assuming that solute represent a fraction (of ca 20%) of the weathering products. This estimation conforms to other recent investigations.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
