Characterizing Pore Water Chemistry

Chemistry analyses were conducted on pore waters and the sediment itself. Pore waters were sampled by centrifuging the 15 mL sediment tubes at 2200 × g for 15 min and the supernatant transferred into a new 15 mL acid washed centrifuge tube (Thermo Scientific™). The pore water was filtered through a 0.7 µm Target2™ GMF Syringe Filter (Thermo Scientific™) and pH was measured with a pH electrode (pHenomenal, VWR™). Sulfate, dissolved inorganic phosphate, total iron, nitrate + nitrite (in combination), and organic matter were measured as previously described^{14 (link)} except for organic matter samples that were dried for a total of six days at 40 °C instead of 3 days at 80 °C.