title: Using EMMA and MIX analysis to assess mixing ratios and to identify hydrochemical reactions in groundwater.
abstract: This study presents a methodology using an end-member mixing analysis (EMMA) and MIX to compute mixing ratios and to identify hydrochemical reactions in groundwater. The methodology consists of (1) identifying the potential sources of recharge, (2) characterising recharge sources and mixed water samples using hydrogeochemistry, (3) selecting chemical species to be used in the analysis and (4) calculating mixing ratios and identification of hydrochemical reactions in groundwater. This approach has been applied in the Besòs River Delta area, where we have collected 51 groundwater samples and a long data register of the hydrogeochemistry of the Besòs River created by the Catalan Water Agency is also available. The EMMA performed in the Besòs River suggests that 3 end-members are required to explain its temporal variability, accounting for the species chloride, sulphate, sodium, bicarbonate, calcium, magnesium, potassium, ammonium, total nitrogen, and electrical conductivity. One river end-member is from the wet periods (W1), and two are from dry periods (D1 and D2). These end-members have been used to compute mixing ratios in groundwater samples because the Besòs River is considered the main recharge source for the aquifer. Overall, dry season end-members dominated over the wet season end-member, in a proportion of 4:1. Moreover, when departures from the mixing line exist, geochemical processes might be identified. Redox processes, carbonate dissolution/precipitation and ion exchange processes may occur in Besòs Delta aquifer.
authors.affiliation: GHS, Dept Geotechnical Engineering and Geosciences, Universitat Politecnica de Catalunya, UPC-Barcelona Tech, Jordi Girona 1-3, 08034 Barcelona, Spain; Geological Institute of Catalonia, Balmes 209-211, 08006 Barcelona, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Tubau
authors.affiliation: GHS, Institute of Environmental Assessment & Water Research (IDAEA), CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain. Electronic address: enric.vazquez@idaea.cisc.es.
authors.forename: Enric
authors.initials: E
authors.lastname: Vàzquez-Suñé
authors.affiliation: GHS, Dept Geotechnical Engineering and Geosciences, Universitat Politecnica de Catalunya, UPC-Barcelona Tech, Jordi Girona 1-3, 08034 Barcelona, Spain; GHS, Institute of Environmental Assessment & Water Research (IDAEA), CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Jurado
authors.affiliation: GHS, Institute of Environmental Assessment & Water Research (IDAEA), CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Carrera
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D060587:Groundwater / Q000737:chemistry*; D057446:Hydrodynamics; D008956:Models, Chemical; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D014874:Water Pollutants, Chemical
keywords: EMMA; MIX; Mixing analysis; Urban groundwater