Methane and Nitrous Oxide in the Guadalquivir estuary (SW Spain) over 2016‐2017

This data set includes measurements of water samples collected from 5 sites during 8 surveys carried out between March 2016 and March 2017 in the Guadalquivir river estuary. Geographic coordinates of sampling positions and a Google Earth .kml file are provided. During samplings, in situ water conductivity (converted to salinity), temperature and pH were measured using a multi‐probe (YSI‐6920V2, YSI Incorporated, Yellow Springs, Ohio, USA) and water samples were collected for laboratory analysis of dissolved methane and nitrous oxide by static‐head space equilibration gas chromatography (GC) using an Agilent 7890 GC equipped with an Electron Capture Detector (ECD) for N2O and Flame Ionization Detector (FID) for CH4, according to de la Paz et al. (2015). Samples were also taken for analysis of phosphate, nitrate, nitrite and ammonia (with a Skalar Sanˆ++215 Continuous Flow Analyzer and using the standard colorimetric techniques described in Hansen and Koroleff 1999), dissolved oxygen and total alkalinity (using a Metrohm 794 Titroprocessor following the methods described by Mintrop et al. (2000) and Winkler) and dissolved organic carbon and total dissolved nitrogen that through catalytic oxidation at high temperature (720 °C) and chemiluminescence (using a Shimadzu Total Organic Carbon analyzer Model TOC‐VCPH/CPN, according to Álvarez‐Salgado and Miller 1998). Dissolved carbon dioxide partial pressure was calculated from pH and total alkalinity using co2sys.xls (Pierrot et al., 2000) with the dissociation constants for carbon and sulphate of Cai and Wang (1998) and Dickson (1990), respectively. Calculations of the equilibrium concentrations of methane and nitrous oxide in the water phase was done using the annual averaged atmospheric mixing ratios CH4 (xCH4atm) and N2O (xN2Oatm) provided by the World Data Center for Greenhouse Gases (http://ds.data.jma.go.jp/gmd/wdcgg/). Such mean values during the sampling period were calculated as 1866 ppb and 328 ppb for xCH4atm and xN2Oatm respectively. Daily measurements of rainfall (mm), air temperature (ºC), relative humidity and wind speed (m s‐1) were provided by ameteorological station located in Lebrija (36º 58’ 35’‘N, 06º 07’ 34”W) managed by the Junta de Andalucia (www.juntadeandalucia.es/agriculturaypesca/ifapa/ria/servlet/FrontController). The data are provided as [space] delimitated plain text files and Google Earth .kml and .kmz files within a compressed folder that also includes a single README file (in PDF format) containing a detailed description of the data structure.