title: Recent trends in chloride and sodium concentrations in the deep subalpine lakes (Northern Italy).
abstract: A growing concern exists about the effects of chloride (Cl) on freshwater systems. Increasing Cl concentrations have been observed in the last few decades in several rivers and lakes, mainly in northern countries. In Italy, present levels and temporal changes of sodium (Na) and Cl in water bodies have rarely been assessed. Based on long-term data for the lakes of the subalpine district in Italy (Maggiore, Lugano, Como, Iseo, Garda), we analyzed trends affecting Cl and Na concentrations during the last 25 years, with the aim of identifying temporal changes and assessing possible causes. An in-depth analysis is presented for Lake Maggiore. Positive temporal Na and Cl trends were evident in all studied lakes, with the trends increasing since early 2000s. Data for Lake Maggiore tributaries showed a clear seasonality (higher values in winter and early spring). The NaCl used as road de-icing agent, together with Cl discharge from wastewater treatment plants, were identified as the main causes for the observed trends. Chloride concentrations in the lakes are below the threshold limit for reduced water quality and below concentrations known to harm aquatic biota. However, considering the relevance of deep subalpine lakes, representing almost 80% of the total freshwater volume in Italy, these trends indicate an important chemical change, which warrants further analysis.
authors.affiliation: CNR Institute of Ecosystem Study, L.go Tonolli 52, 28922, Verbania Pallanza, Italy. m.rogora@ise.cnr.it.
authors.forename: Michela
authors.initials: M
authors.lastname: Rogora
authors.affiliation: CNR Institute of Ecosystem Study, L.go Tonolli 52, 28922, Verbania Pallanza, Italy.
authors.forename: Rosario
authors.initials: R
authors.lastname: Mosello
authors.affiliation: CNR Institute of Ecosystem Study, L.go Tonolli 52, 28922, Verbania Pallanza, Italy.
authors.forename: Lyudmila
authors.initials: L
authors.lastname: Kamburska
authors.affiliation: IASMA Research and Innovation Centre, Istituto Agrario di S. Michele all'Adige -Fondazione E. Mach, Via E. Mach 1, 38010, S. Michele all'Adige, Trento, Italy.
authors.forename: Nico
authors.initials: N
authors.lastname: Salmaso
authors.affiliation: IASMA Research and Innovation Centre, Istituto Agrario di S. Michele all'Adige -Fondazione E. Mach, Via E. Mach 1, 38010, S. Michele all'Adige, Trento, Italy.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Cerasino
authors.affiliation: Department of Earth and Environmental Sciences, University of Milan Bicocca, Piazza della Scienza 1, 20126, Milan, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Leoni
authors.affiliation: Department of Earth and Environmental Sciences, University of Milan Bicocca, Piazza della Scienza 1, 20126, Milan, Italy.
authors.forename: Letizia
authors.initials: L
authors.lastname: Garibaldi
authors.affiliation: Department of Earth and Environmental Sciences, University of Milan Bicocca, Piazza della Scienza 1, 20126, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Soler
authors.affiliation: University of Applied Sciences and Arts of Southern Switzerland (SUPSI), Via Trevano 72, 6952, Canobbio, Switzerland.
authors.forename: Fabio
authors.initials: F
authors.lastname: Lepori
authors.affiliation: University of Applied Sciences and Arts of Southern Switzerland (SUPSI), Via Trevano 72, 6952, Canobbio, Switzerland.
authors.forename: Luca
authors.initials: L
authors.lastname: Colombo
authors.affiliation: ARPA Lombardia, Dipartimento di Lecco, Via I Maggio, 21/b, 23848, Oggiono, Lecco, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Buzzi
mesh_terms: D002712:Chlorides / Q000032:analysis*; D004784:Environmental Monitoring; D007558:Italy; D060106:Lakes / Q000737:chemistry*; D045483:Rivers; D012964:Sodium / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D002712:Chlorides; D014874:Water Pollutants, Chemical; D012964:Sodium
keywords: Deep subalpine lakes; Long-term trends; NaCl; Water chemistry