Soil texture is one of the main factors controlling soil organic carbon (SOC) storage. Accurate soil-texture analysis is costly and time-consuming. Therefore, the clay content is frequently not determined within the scope of regional and plot-scale studies with high sample numbers. Yet it is well known that the clay content strongly affects soil water content. The objective of our study was to evaluate if the clay content can be estimated by a simple and fast measure like the water content of air-dried soil. The soil samples used for this study originated from four different European regions (Hainich-Dün, Germany; Schwäbische Alb, Germany; Hesse, France; Bugac, Hungary) and were collected from topsoils and subsoils in forests, grasslands, and croplands. Clay content, water content of air-dried soil, and SOC content were measured. Clay content was determined either by the Pipette method or by the Sedigraph method. The water content of air-dried soil samples ranged from 2.8 g kg–1 to 63.3 g kg–1 and the corresponding clay contents from 60.0 g kg–1 to 815.7 g kg–1. A significant linear relationship was found between clay content and water content. The scaled mean absolute error (SMAE) of the clay estimation from the water content of air-dried soil was 20% for the dataset using the Pipette method and 28% for the Sedigraph method. The estimation of the clay content was more accurate in fine-textured than in coarse-textured soils. In this study, organic-C content played a subordinate role next to the clay content in explaining the variance of the water content. The water retention of coarse-textured soils was more sensitive to the amount of organic C than that of fine-textured soils. The results indicate that in our study the water content of air-dried soil samples was a good quantitative proxy of clay contents, especially useful for fine-textured soils
Reactive iron (Fe) oxides and sheet silicatebound Fe in reservoir rocks may affect the subsurface storage of CO 2 through several processes by changing the capacity to buffer the acidification by CO 2 and the permeability of the reservoir rock: (1) the reduction of threevalent Fe in anoxic environments can lead to an increase in pH, (2) under sulphidic conditions, Fe may drive sulphur cycling and lead to the formation of pyrite, and (3) the leaching of Fe from sheet silicates may affect silicate diagenesis. In order to evaluate the importance of Fe-reduction on the CO 2 reservoir, we analysed the Fe geochemistry in drill-cores from the Triassic Stuttgart Formation (Schilfsandstein) recovered from the monitoring well at the CO 2 test injection site near Ketzin, Germany.The reservoir rock is a porous, poorly to moderately cohesive fluvial sandstone containing up to 2-4 wt% reactive Fe. Based on a sequential extraction, most Fe falls into the dithionite-extractable Fe-fraction and Fe bound to sheet silicates, whereby some Fe in the dithionite-extractable Fe-fraction may have been leached from illite and smectite. Illite and smectite were detected in core samples by X-ray diffraction and confirmed as the main Fe-containing mineral phases by X-ray absorption spectroscopy. Chlorite is also present, but likely does not contribute much to the high amount of Fe in the silicate-bound fraction. The organic carbon content of the reservoir rock is extremely low (\0.3 wt%), thus likely limiting microbial Fe-reduction or sulphate reduction despite relatively high concentrations of reactive Fe-mineral phases in the reservoir rock and sulphate in the reservoir fluid. Both processes could, however, be fuelled by organic matter that is mobilized by This article is part of a Topical Collection in Environmental Earth Sciences on ''Subsurface Energy storage'', guest-edited by
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.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.