Assessing Reducing Conditions in Soils along a Topohydrosequence.

Accurate assessment of reducing conditions in soil is important for understanding fundamental biogeochemical processes, as well as in supporting regulatory decisions pertaining to hydric soils. A number of methods have been developed to measure reduction in soils. However, most of the commonly used approaches have complex methodology which require specialized equipment requiring significant care and maintenance, and do not yield results that are easily used or understood by soil consultants or the general public.  The use of IRIS tubes represent a relatively new technology for measuring reduction in soils. IRIS tubes are sections of PVC tubing coated with iron oxide paint that are placed in the soil for a given period of time. The iron oxide paint is exposed to the natural soil environment and under reducing conditions, the iron oxide paint is solubilized and stripped from the tube. However, IRIS tubes are currently only useful as a qualitative tool due to limited data comparing IRIS tube paint removal to more established quantitative methods of measuring soil reduction. The objective of this study was to determine the relationship between the performance of IRIS tubes and other methods of documenting reduction in soils. Four points were identified along each of two topohydrosequences on the coastal plain of Maryland. At each point, reducing conditions were assessed by measuring Eh with platinum electrodes, documenting the reaction of alpha alpha dipyridyl dye, and the performance of IRIS tubes. The results from each of these methods will be compared in order to determine how best to interpret the data collected using these approaches.