Isotope biogeochemical in a temperate coastal peatland after flooding by brackish water

The biogeochemical impact of brackish water rewetting was investigated using stable isotopes, DIC, major ions and nutrient concentration of a coastal peatland in southern Germany (Drammendorf).Soils and pore water samples were collected before and after brackish water intrusion from a lagoon (Kubitzer Bodden).Pore waters were extracted before soil and pore water analyses.Pore water samples were measured for water and dissolved inorganic carbon (DIC) stable isotopes, physical parameters, major ions and nutrients concentrations.Soil samples were analyzed for acid-extractable metals and nutrients, CNS contents, acid-volatile sulfides and chromium-reducible sulfides concentrations.Results showed the vertical signatures of recent brackish water intrusion and previous freshwater rewetting using water stable isotopes, Mg and Na concentrations.The intrusion influenced organic and inorganic compounds, DIC releases and authigenic minerals formation and dissolution.The soil TOC decrease indicates the persistence of organic matter decomposition and diagenesis.ẟ¹³C-DIC indicated DIC from organic matter/methane oxidation, carbonate dissolution and seawater-derived DIC. P and Ca increases indicate nutrient release and mineral dissolution. Additional sulfate concentrations influenced diagenesis and led to the formation of authigenic minerals.AVS/CRS ratio indicates pyrite formation below and upper soil surface volatile sulfides enrichment.The study shows the influence of peatland rewetting with possible future sea level rise perspective.