Camera illustration of Indicator of Reduction in Soils (IRIS) reduction dynamics

LeFevre, Olivia Victoria; Knappenberger, Thorsten; Shaw, Joey N.; Olshansky, Yaniv

doi:10.1002/ael2.20051

Cited by 2 publications

(1 citation statement)

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“…This is an important concept to disentangle, particularly regarding the future use of IRIS devices in fulfillment of the HSTS protocol and future soil biogeochemical studies. To do so, future studies may consider deploying rhizosphere cameras in situ to capture iron and manganese reduction (IRIS paint removal) at high temporal resolutions across a range of biogeochemical conditions (LeFevre et al., 2021). A study of this nature would help to disentangle the exact timing associated with direct Fe‐oxide paint removal (via Fe‐reduction exclusively) versus the precipitation of FeS followed by the removal of FeS (i.e., a change from an orange color to white color versus a change from black color to white color on IRIS devices), which would help to inform future research and management decisions reliant on biogeochemical soil conditions.…”

Section: Resultsmentioning

confidence: 99%

Rapid formation of iron monosulfide on Indicator of Reduction in Soil devices in S‐rich hydric soils

Duball

Andersen

Beaudette

et al. 2023

Soil Science Soc of Amer J

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Indicator of Reduction in Soil (IRIS) devices are used to identify anaerobic conditions in soils for hydric soil and wetland identification purposes. IRIS devices quantify anaerobic conditions via the visualization of iron (Fe) reduction (e.g., orange Fe 3+ paint reduces to soluble Fe 2+ , leaving behind the bare, white polyvinyl chloride device). Under stronger reducing conditions, sulfate (SO 4 2− ) reduction can occur, and sulfides (S 2− and/or H 2 S) can react with the Fe 3+ paint, resulting in the precipitation of black-colored, reduced iron monosulfide (FeS). While these processes are well known, the rate of FeS formation remains relatively understudied and current IRIS methods may not capture these data accurately. This study investigated FeS formation on IRIS films to identify deployment times that capture the minimum and maximum precipitation of FeS. To determine the timing and magnitude of FeS-precipitation on IRIS films, five replicate films were deployed in a wet, S-rich soil, across 11 periods ranging from 2 min to 30 days. Results show that FeS precipitated on IRIS films in just 2 min, and the highest average amount of FeS (82%) precipitated in 1 day. After 1 day, the percentage of FeS decreased and a white color change became more apparent on IRIS films. Our results suggest that the recommended 30-day deployment period is too long for accurately measuring FeS-precipitation on IRIS devices deployed in wet, alkaline soils. These considerations should be incorporated into standard IRIS protocols used to quantify anaerobic conditions and other biogeochemical conditions (e.g., pore-water sulfide levels) in S-rich soils. INTRODUCTIONWetlands provide valuable ecosystem services including water filtration, increased biodiversity, flood abatement, and provision of habitat for rare, endangered, and migratory species, among others. Wetland areas are typically identified based on a three-parameter approach requiring positive evidence of wetland hydrology,

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Section: Resultsmentioning

confidence: 99%