Iron‑sulfur geochemistry and acidity retention in hydrologically active macropores of boreal acid sulfate soils: Effects of mitigation suspensions of fine-grained calcite and peat

Storage and Distribution of Organic Carbon and Nutrients in Acidic Soils Developed on Sulfidic Sediments: The Roles of Reactive Iron and Macropores

“…Given the widespread occurrence and massive surface areas of the macropores in the oxidized zones of the AS soils on the experimental field and elsewhere in boreal AS soils, the Fe hydroxides and oxyhydroxysulfates on the macropores should trap large quantities of mobile Fe pools released by pyrite oxidation and pH-promoted weathering of Fe-bearing phyllosilicates during the formation and ripening of AS soils. It is well-documented that, in contrast to a large number of other metals, Fe is lost to only a limited extent, and can even accumulate in the oxidized zones of typical boreal AS soil profiles. ,,, As elaborated previously, the accumulation of Fe hydroxides and oxyhydroxysulfates on macropore surfaces was likely further contributed by continuous oxidation of dissolved Fe­(II) species, diffused locally from the interiors of columnar blocks and supplied via evaporation-driven capillary movement of soil porewater or moisture from underlying transition zones. The relevance of the latter process is further supported by abundant aqueous and organically complexed Fe­(II) in the transition zone samples (Table ).…”

“…It is well-documented that, in contrast to a large number of other metals, Fe is lost to only a limited extent, and can even accumulate in the oxidized zones of typical boreal AS soil profiles. 36 , 66 , 68 , 76 As elaborated previously, 40 the accumulation of Fe hydroxides and oxyhydroxysulfates on macropore surfaces was likely further contributed by continuous oxidation of dissolved Fe(II) species, diffused locally from the interiors of columnar blocks and supplied via evaporation-driven capillary movement of soil porewater or moisture from underlying transition zones. The relevance of the latter process is further supported by abundant aqueous and organically complexed Fe(II) in the transition zone samples ( Table 2 ).…”

“… 35 , 66 − 68 The results of previous studies with samples from one site in the same field revealed strong concomitant enrichments of both near-total as well as 1 and 4 M HCl-extractable fractions of Fe and S on macropore surfaces relative to the interiors of solid columnar blocks. 40 , 41 This should be a widespread feature for the whole experimental field given that the macropore surfaces sampled from all 11 sites across the field were significantly and concomitantly enriched with 1 M HCl-extractable Fe and S fractions relative to the interior counterparts ( Tables 1 and S1 ). As predicted by the LCF-EXAFS analysis, the 1 M HCl-extractable Fe and S fractions in the samples from the macropore surfaces and interiors were largely bound to ferrihydrite and schwertmannite ( Table 2 ).…”

“…The sulfidic sediments are typically rich in OC and nutrients, and consequently, the subsoil layers of AS soils host large pools of these compounds, , in contrast to other mineral soils, whose OC/nutrient stocks are largely stored within the top layers. One characteristic of AS soils is that the (sub)­oxic subsoil layers retain abundant reactive Fe as secondary Fe oxyhydroxides (e.g., ferrihydrite) and oxyhydroxysulfates (e.g., schwertmannite and jarosite), in particular on exposed surfaces of hydrologically active macropores. − Furthermore, the groundwater table in many of these soils is shallow and thus can vary substantially due to variations in local/regional climato-hydrological conditions. Consequently, the reactive Fe minerals are subject to alternating redox cycles and linked transformation/redistribution processes.…”

Groundwater and Anthropic Activities: A Qualitative Study on Treatment Techniques

“…Preliminarily characterized by (CONAMA [33]), where the waters were also classified into 5 different types according to their quality and degree of potability, with support in Law 9.433 of 1997 that establishes the criteria for use and consumption, criteria that were improved later by Resolution 153 of the Ministry of Environment (BRASIL [34]), which at this time already notes beyond the standards of potability, the need for controlled use, monitoring and decontamination of this resource and establishes deadlines for investigation, bodies responsible for this supervision and monitoring, only leaving open the methodologies to be used for such. It is worth noting that the type of soil, its coverage, the type of native vegetation (YU, et al [35]), its grain size and porosity, the form of use has fundamental importance in the characteristic and quality of groundwater, because the soil, a natural structure, complex and composed in its formation by phases: solid, liquid and gaseous (VILA, et al [36]). With a specific and varied granulometry, a chemical composition formed in the biogeochemical process where there are parts of the "Mother" rock of origin, but also has characteristics and materials coming from processes of decomposition of a diversity of sources such as fruit, dead animals (SANTHIYASRI, et al [37,38]), microorganisms, small animals that are responsible for assisting in the chemical and biological synthesis so necessary for its exploitation and use as a source of energy and food.…”