Sediment and Porewater Geochemistry Analysis

BW, pore water [wet sediment was centrifuged at 2,200 × g for 15 min and the water filtered through a 0.7- μM Target2™ GMF Syringe Filter (Thermo Scientific™)], and SED was analyzed. pH (pHenomenal, VWR pH electrode, VWR™) was measured for BW and pore water samples. Total Fe, ${\text{PO}}_4^{3-}$ , and ${\text{SO}}_4^{2-}$ concentrations for pore water and BW were measured based on spectrophotometric methods (Broman et al., 2018 (link)). Additionally, ${\text{NO}}_3^{-}$ and ${\text{NO}}_2^{-}$ concentrations for pore water were measured using Hach–Lange cuvette tests LCK339 and LCK341, respectively. Organic matter content (% wt) was measured using the loss on the ignition method as described in Broman et al. (2017b (link)) except that the sample was dried before loss on ignition analysis for 6 days at 40°C instead of 3 days at 80°C.