Saline-alkali soil remediation enhanced the hydroxyl radical production as well as the soluble Fe(II) content generated via the dissimilatory microbial iron reduction

Global change has intensified soil salinization worldwide. Various amendments have been used to mitigate this issue. Hydroxyl radicals (·OH), which can be formed by the reaction of dissimilatory microbial iron reduction (DMIR)-derived Fe(II) with H2O2, play a key role in soil geochemical processes; however, the effect of soil amendments on ·OH generation within saline-alkali soils remains poorly understood. To address this gap, we analyzed data from saline-alkali soil remediation projects in Northeast China and explored the underlying mechanisms. This study selected the commonly used chemical amendments, desulfurized gypsum and the organic amendment, Polyaspartic acid calcium (PASP-Ca) for soil experiments. Our results demonstrated that, compared with the control treatment, the ·OH content in saline-alkali soil increased by 69.71% and 194.20% after the application of desulfurization gypsum and PASP-Ca, respectively. compared with the traditional amendment desulfurization gypsum, PASP-Ca not only exhibits superior improvement effects but also significantly promotes the generation of ·OH . This increase in ·OH was strongly associated with improved soil nutrient conditions, a rise in both ferric-reducing bacteria (FeRB) abundance and DMIR-derived soluble Fe(II), and a decrease in soil pH after the application of the amendments. Our research also found that the soluble Fe(II) derived from complexed iron (Fep), which correlated positively with soil nutrients and FeRB abundance, and negatively with soil pH. The findings of this study are expected to be validated and generalized through additional experiments involving various types of saline-alkali soil amendments thereby offering new insights into the understanding of soil geochemical cycles during the remediation of saline-alkali soils.