Iron
(Fe) oxides in soils are strong sorbents for environmentally
important compounds like soil organic matter (SOM) or phosphate, while
sorption under field conditions is still poorly understood. We installed
polyvinyl chloride plastic bars which have been coated either with
synthetic Fe or manganese (Mn) oxides for 30 days in a redoximorphic
soil. A previous study revealed the formation of newly formed (“natural”)
Fe oxides along the Mn oxide coatings. This enables us to differentiate
between sorption occurring onto the surfaces of synthetic versus natural
Fe oxides. After removal of the bars, they were analyzed by nanoscale
secondary ion mass spectrometry (NanoSIMS) to study the distribution
of Fe (56Fe16O–), SOM (12C14N–), and phosphorus (31P16O2
–) at the microscale.
Image analysis of individual Fe oxide particles revealed a close association
of Fe, SOM, and P resulting in coverage values up to 71%. Furthermore,
ion ratios between sorbent (56Fe16O–) and sorbate (12C14N– and 31P16O2
–) were smaller
along the natural oxides when compared with those for synthetic Fe
oxides. We conclude that both natural and synthetic Fe oxides rapidly
sequester SOM and P (i.e., within 30 days) but that newly, natural
formed Fe oxides sorbe more SOM and P than synthetic Fe oxides.
Soils are highly heterogeneous entities in which organic and inorganic as well as living and non-living building blocks interact to form biogeochemical interfaces. While processes at these interfaces occur at the micrometer or submicrometer scale, they are thought to influence the behavior of soils at the global scale, e.g. soils as carbon sinks. Analytical methodologies with a high resolution are, therefore, required in order to investigate these processes with the final goal to understand biogeochemical-interface formation mechanistically. In the present study, sorption experiments of water-extractable organic matter on model minerals, such as boehmite and illite, were performed. Adsorption of organic matter on the minerals was quantified by conventional bulk-scale methods and compared with data from nanoSIMS measurements. From the data obtained, scaling factors have been developed which permit the quantification of organic matter in the secondary ion images provided by nanoSIMS.
NanoSIMS measurements confirmed the capacity to produce images, which indicated the uniform increase in Al-concentrations in goethite. Using a combination of statistical analysis with information from complementary spectroscopic techniques (XRD, FTIR and Mössbauer spectroscopy) we were further able to reveal spots with lower Al/Fe ratios as hematite.
This editorial was written by early career scientists in soil science and gives an overview of the articles published in the special issue “Soil Science Challenges—An Interdisciplinary Overview of Current and Future Topics” on the occasion of the 100th anniversary of Journal of Plant Nutrition and Soil Science. A broad range of articles addressing soil carbon dynamics from the microscale to landscape scale, multi‐dimensional modeling, improved land management practices, nutrient cycles, soil hydrology, plastic in soils, and interdisciplinarity of soil science is covered in this issue.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.