Trends in groundwater chemistry across Sweden during 1980−2020

This dataset contains medians, linear trends and change points in groundwater chemistry across Sweden during 1980-2020. Water chemical parameters include measured pH, alkalinity, concentrations of base cations and acid anions, dissolved oxygen, dissolved silica, total organic carbon, groundwater temperature, groundwater level, as well as dissolved inorganic carbon and carbon dioxide calculated using carbonate equilibrium equations based on pH, alkalinity and temperature. The statistics are calculated from a total of 5745 sampling occasions for 55 groundwater wells or springs that are part of the National Groundwater Chemistry Monitoring program run by the Geological Survey of Sweden. Included is also background information on the sampling locations. The aim with this data compilation is to evaluate effects of environmental changes on groundwater carbon cycling. Given are medians and linear trends (Theil sen slopes, incl. p-value), change points in trends and numbers of observation of dissolved inorganic carbon, carbon dioxide, pH, alkalinity, total organic carbon, base cations (Ca, Mg, K, Na), acid anions (Cl, SO4, NO3), ammonium, dissolved silica, dissolved oxygen, groundwater temperature and groundwater level. Medians and linear trends are also given for transformations (Pivot coordinates) of the above listed water chemical variables that account for the compositional nature of the data (Templ et al. 2011). Additionally, site specific information is given, including site name / ID, geographic coordinates, bedrock type, aquifer type and well depth. Dissolved inorganic carbon and carbon dioxide is calculated using carbonate equilibrium equations based on alkalinity, pH and water temperature, using the R package "phreeqc" (Charlton and Parkhurst 2011). Trends are calculated for the periods 1980-2000, 2000-2020 and 1980-2020 using the R package "rkt" (Marchetto 2021). Break points are calculated using the R package "segmented" (Muggeo 2008). Pivot coordinates are calculated using the R package ‘robCompositions’ (Templ et al. 2011). The raw data is openly available at Swedish Geological Survey (SGU 2022a,b). The data was downloaded on 2021-10-03. References: Charlton, S. R. & Parkhurst, D. . Modules based on the geochemical model PHREEQC for use in scripting and programming languages: Computers & Geosciences, v. 37, p. 1653-1663. (2011) Marchetto, A. rkt: Mann-Kendall Test, Seasonal and Regional Kendall Tests. R package version 1.6. Available at: https://CRAN.R-project.org/package=rktOpens in a new tab. (2021). Muggeo, V. M. R. segmented: an R Package to Fit Regression Models with Broken-Line Relationships. R News, 8/1, 20-25. Available at: https://cran.r-project.org/doc/Rnews/Opens in a new tab. (2008). SGU. Data från miljöövervakning av grundvatten, öppna data (Groundwater environmental monitoring data, in Swedish). Available at: https://www.sgu.se/produkter/geologiska-data/oppna-data/grundvatten-oppna-data/miljoovervakning-av-grundvatten/Opens in a new tab. (2022a). SGU. Data om grundvattennivåer (Groundwater level data, in Swedish). Available at https://www.sgu.se/grundvatten/grundvattennivaer/ladda-ned-grundvattendata/Opens in a new tab. (2022b). Matthias Templ, Karel Hron, P. F. robCompositions: an R-package for robust statistical analysis of compositional data. v. 2.3.1. in Compositional Data Analysis. Theory and Applications (eds. Pawlowsky-Glahn, V. & Buccianti, A.) 341–355 (John Wiley & Sons, 2011).