“…The accumulation of schwertmannite and jarosite on the macropore surfaces of the reference columns in terms of amounts (and to some extent also in terms of concentrations) led to a significant build-up of the S NAS fraction (approximately 8-9 g/kg, Fig. 2b), compared to the interiors whose S NAS concentrations were overall comparable with those reported for bulk acid sulfate soils in the tropical regions (Sukitprapanon et al, 2015;Yuan et al, 2015;Huang et al, 2016). The dissolution and hydrolysis of these iron oxyhydroxysulfates could not only result in a successive decrease in S NAS , but also slow release of acidity and thus inhibit the recovery of soil pH.…”