Surface waters, suspended solids, and sediments from the Nievole River Valley sub-basin (Tuscany, Central Italy): a preliminary environmental evaluation

The Padule di Fucecchio (Tuscany, Central Italy) is located in the lower reaches of the Nievole River Valley. It represents a protected swampy zone that plays an important role in the migratory routes of several bird species. The study area is positioned within the complex riverine network composed by the Nievole, Pescia di Collodi and Pescia di Pescia rivers, including many artificial channels that crosscut the western part of the basin, and collects effluents from many small cities and industrial districts. The Padule di Fucecchio waters are fed by the Usciana River, which is an artificial channel built in 1934 and represents the only emissary of the swampy area that, after 25 km, flows into the right bank of the Arno River. All the sub-basins are complex ecosystems characterized by many relevant anthropic activities and small-medium enterprises, such as paper mill industries, flora-nursery farms and one of the most productive Italian tanning districts, making this zone one of the most polluted district of the Arno River Basin. The main aim of the PhD project is to define the anthropogenic and natural contributions that affect the surface waters, suspended solids load, and sediments of the Nievole River Valley, Padule di Fucecchio and Usciana River using major, minor, and trace elements, Pb-Nd-Sr isotope data. We present some preliminary results on the evaluation of the water and suspended solids load quality in the Nievole River Valley. Water samples, suspended solids, and sediments samples were collected along the main course and tributaries distributed in an area of about 320 km2. Temperature, pH and electrical conductivity were measured in the field with a multi-probe portable probe. Alkalinity was determined by volumetric titration while N-species were measured by molecular spectrophotometry. Major and trace elements were determined by Ion Chromatography (IC) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), respectively, while radiogenic isotopic ratios in the water and suspended particulate samples were analyzed by Thermal Ionization Mass Spectrometry (TIMS). Water chemistry showed a relatively wide variability since Ca2+(Mg2+)- HCO3- to Na+-Cl-(SO42-) geochemical facies were recognized. The N-bearing species were characterized by concentrations up to 36 (NO3-), 2.4 (NO2-) and 11.5 (NH4+) mg/L, while those of Mn, Fe, and Cs were up to 595, 432, and 36.7 μg/L, respectively. As far as the metal content in the suspended solid load, Cr and Zn revealed the highest concentrations (up to 429 and 409 mg/kg, respectively). Nickel, V, Pb, Cs, and As showed values up to 120, 149, 83, 46, and 25 mg/kg, respectively. According to Legislative decree 152/2006, the heavy metal concentrations for the suspended solids data approach or are higher than those for the Italian soils intended for green public areas suggesting that a strong anthropogenic pressure is acting on the Nievole River Valley