Characterizing the Redox Status in Three Different Forested Wetlands with Geochemical Data

Abstract

Biogeochemistry and regulation of redox processes in wetlands and especiallytheir source sink functions regarding sulfur, nitrogen, iron, and alkalinity are still poorly understood and become increasingly important in a world of global change. We investigated three forested wetlands within the Lehstenbach catchment (Fichtelgebirge, Northeastern Bavaria, Germany) differing in their degree of water saturation, vegetation, and availability of iron with stable sulfur analysis as well as geochemical analysis (iron, nitrate, sulfate, and oxygen contents in soil solutions and groundwater). Results indicated considerable nitrate, sulfate, and iron reduction rates bound to high spatial and temporal heterogeneity at all three sites. Sites differed significantly regarding their oxygen saturation and their dynamics of sulfur and iron reduction. The sequential reduction chain did not seem an applicable concept to describe redox dynamics at micro- (cm(2)) or mesoscale (m(2)) because of (1) high small-scale heterogeneity and (2) an absence of clear relationships between redox indicative parameters. The latter might be caused by redox processes occurring simultaneously at the investigated spatial and temporal scales. However, a tendency toward exclusive relationships between oxygen and iron, nitrate and iron, and delta34S with oxygen, nitrate, and sulfate indicated that the sequential reduction chain might be a suitable modeling concept for macroscale (km(2)) investigations with large sample numbers.

Electrodic voltages in the presence of dissolved sulfide: Implications for monitoring natural microbial activity

“…Our study of a natural wetland soil is significant because the microbial-driven biogeochemistry of redox processes in wetlands, particularly source-sink cycling of sulfur, remains poorly understood and increasingly relevant as a result of global climate change and modification of near-surface soil chemistry by human inputs ͑e.g., Alewell et al, 2006͒. For example, microbial sulfate reduction under anaerobic conditions is coupled to source-sink cycling of iron and heavy metal contaminants in wetland soils.…”

Colloid-associated export of arsenic in stream water during stormflow events

“…S9). Nevertheless, previous studies have demonstrated high levels of sulfate reducing activity in the wetlands of the catchment (Alewell et al, 2006;Knorr et al, 2009), and sulfhydryl groups could thus form through reaction between sulfide and organic matter (Einsiedl et al, 2008;Hoffmann et al, 2012). Sorption of arsenic to iron (oxy)hydroxide colloids is important in soil systems (La Force et al, 2000;Blodau et al, 2008;Dousova et al, 2012;Langner et al, 2012) and has been extensively studied in the laboratory (Dixit and Hering, 2003;Bauer and Blodau, 2009;Sharma et al, 2010).…”

Arsenic detoxification potential of aox genes in arsenite-oxidizing bacteria isolated from natural and constructed wetlands in the Republic of Korea

“…Within wetlands, microorganisms play an important role in transformations of heavy metals and metalloids via direct or indirect oxidation/reduction within the aquatic ecosystems (Alewell et al 2006;Dedysh et al 1998). In turn, the microbial transformations could lead the detoxification of pollutant elements such as arsenic, from anthropogenic sources D'Angelo and Reddy 1999;Mukhopadhyay et al 2002;White and Metcalf 2004).…”