Indicator of Reduction in Soils (IRIS) films are visual sensors used to document weakly or moderately reducing conditions in soils based on the reduction and removal of brown manganese (Mn) oxide or orange iron (Fe) oxide paints, respectively, from underlying white polyvinyl chloride (PVC) films. Paint removal is largely assumed to result from anaerobic microbial reduction using metal oxides on the PVC films as electron acceptors. If true, IRIS films could indicate conditions favorable to other biogeochemical processes that occur at similar redox potentials to those facilitating paint removal. Our objective here was to assess the effects of selected abiotic soil properties on IRIS film paint removal to determine whether removal can accurately be attributed to biotic processes alone. Through field deployments and laboratory incubation experiments using IRIS films, we investigated relative sulfide concentration and dissolved organic matter as two abiotic factors potentially capable of removing paint from Mn IRIS films. Our results showed that abundance of reactive soluble sulfides cause rapid and extensive abiotic paint removal from Mn films, whereas ambient concentrations of dissolved organic matter in freshwater wetland porewater does not drive abiotic removal. Furthermore, we found that the visible formation of black iron monosulfides on Fe films can be used to detect sulfide concentrations that will remove paint from Mn films. This study suggests that whereas some abiotic soil properties (e.g., sulfide concentration) can cause paint removal, IRIS films may be a viable tool to approximate biotic process rates where abiotic paint removal can be ruled out.

中文翻译：

---

影响潮汐和淡水土壤中 IRIS 传感器解释的非生物土壤特性

土壤还原指标 (IRIS) 薄膜是视觉传感器，用于记录土壤中弱或中度还原条件，基于分别从下面的白色聚乙烯中还原和去除棕色氧化锰 (Mn) 或橙色氧化铁 (Fe) 涂料氯化物 (PVC) 薄膜。大部分假设去除油漆是由于使用 PVC 薄膜上的金属氧化物作为电子受体进行厌氧微生物还原。如果属实，IRIS 薄膜可能表明有利于其他生物地球化学过程的条件，这些过程发生在与促进油漆去除的氧化还原电位相似的氧化还原电位下。我们的目的是评估选定的非生物土壤特性对 IRIS 薄膜油漆去除的影响，以确定去除是否可以准确地归因于生物过程。通过使用 IRIS 薄膜的现场部署和实验室孵化实验，我们研究了相对硫化物浓度和溶解有机物作为可能能够从 Mn IRIS 薄膜中去除油漆的两个非生物因素。我们的结果表明，大量的活性可溶性硫化物导致从锰膜中快速和广泛地去除非生物涂料，而淡水湿地孔隙水中溶解有机物的环境浓度不会推动非生物去除。此外，我们发现 Fe 薄膜上黑色单硫化物的可见形成可用于检测将从 Mn 薄膜上去除油漆的硫化物浓度。这项研究表明，虽然一些非生物土壤特性（例如硫化物浓度）会导致油漆去除，