Effects of hydrologic conditions on biogeochemical processes and organic pollutant degradation in salt marsh sedimentsThis article is part of a larger document. View the larger document here.
This work addressed the influence of tidal vs. static hydrologic conditions on biogeochemical processes and the transformation of pollutant organic chemicals (eight representative N-, O-, and S-heterocycles (NOSHs) from coal chemicals, crude oils, and pyrogenic mixtures) in salt marsh sediments. The goals were to: (1) determine the effects of static (flooded, drained) vs. dynamic (tidal) hydrology on redox potential (Eh) dynamics, trace gas evolution, and pollutant transformation; (2) deploy hydrodynamic microcosms for this purpose that were reproducible, well controlled, and adequately monitored; and, (3) develop analytical approaches for target pollutant chemicals that allowed for detection of small but significant concentration differences between time points and treatments, i.e., isotopic dilution. NOSH-amended sediments were exposed to three hydrologic conditions: static drained (oxidized redox potentials), static flooded (reduced redox potentials), and diurnal-tidal (alternating redox potential). The rate of NOSH transformation and the number of NOSHs degraded decreased in the following order: drained = tidal flooded. This indicated that sediments and associated biota exposed to tidal pulsing removed more NOSH compounds faster and to lower levels than flooded, highly reducing sediments.