Suspended sediments in river ecosystems: Photochemical sources ofdissolved organic carbon, dissolved organic nitrogen, and adsorptiveremoval of dissolved iron

摘要

We generated suspended sediment solutions using river sediments and river water atconcentrations similar to those observed during 1.5 year floods (Q1.5) and a dam removal(-325 mg L-1) on the Deep River, North Carolina. Suspended sediment solutions wereexposed to simulated solar radiation, equivalent to one clear, summer day at the study site(35°N). Concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon(DIC), total dissolved nitrogen (TDN), dissolved inorganic nitrogen (DIN), dissolvedorganic nitrogen (DON), soluble reactive phosphorus (SRP) and total dissolved iron (Fed)were measured before and after exposure. Total dissolved carbon (TDC) budgets for eachexperiment were produced using DOC and DIC data. Sediment suspensions in thepresence of simulated solar radiation were significant sources of dissolved C (119 ±11 jmol C L-1 d-1; + values indicate 1 standard error) and DON (1.7 ± 0.5 ,umol N L-1d—') but not DIN or SRP. Extrapolations through the Deep River water column suggestthat suspended sediments in the presence of light represent dissolved organic matterfluxes of 3.92 mmol C 111-2 d-1 and 40 tmol N T11-2 d-1. Additionally, sedimentsuspensions lowered river water Fed concentrations immediately (-24%) andprogressively (-40-90%) in both light and dark treatments. Our research suggestssuspended sediments in river ecosystems are potential sources of dissolved organic C anddissolved organic N while effectively removing Fed from the water column.