Redox-induced mobilization of phosphorus in groundwater affected arable soil profiles
Graphical abstract
Introduction
Phosphorus (P) is an essential nutrient for plant growth. However, the high mobilization of P in soil may increase its loss to the surface and groundwater. The aquatic environmental pollution caused by P has raised the interest in this element because it is considered to be the main element responsible for the eutrophication process (Abdulkareem et al., 2018; Barcellos et al., 2019).
Redox-induced mobilization of nutrients and pollutants in groundwater affected arable soils has large agro-environmental implications, because the redox processes affect the bioavailability of P and also affect its loss to ground and surface water (Sosa, 2018; Chen et al., 2019). Mobilization, bioavailability, and potential loss of P in soils could be affected by redox potential (EH) and pH changes via regulating P biogeochemical processes in soils (Gasparatos et al., 2019; Zhao et al., 2019; Baumann et al., 2020a). For example, the interactions between P and soil constituents (e.g., Fe–Mn-(oxhydr)oxides, calcium carbonates, organic matter) are affected by the dynamics of EH and pH (Gu et al., 2019; Bai et al., 2020).
In soils, P can be bound to soil organic matter (SOM), Fe, Al, and Mn -(oxhydr)oxides, and/or calcium compounds (Shaheen et al., 2007; Baumann et al., 2020b). These fractions can be influenced by soil properties and the changes of soil EH and pH (Yang et al., 2019). Therefore, these soil components are important factors in driving P mobilization in soils (Cui et al., 2019). The mobilization of P under anaerobic conditions has been studied in peat soils (Meissner et al., 2008). However, the impact of systematic changes of EH and the EH–dependent changes of governing factors such as pH, dissolved organic (DOC) and inorganic (DIC) carbon, and the Fe- and Mn- (oxhydr)oxides on the mobilization of P in groundwater affected arable soils is not known yet.
Worldwide, arable land is covering around 1.5 billion hectares (Hens and Quynh, 2016). Approximately 40% of this arable land is naturally acidic, which may have developed with intensive agriculture, particularly when rainfall exceeds evapotranspiration (Kamprath and Smyth, 2005). Further, around 80 million hectares are affected by water logging (Hens and Quynh, 2016). In arable soils, particularly in Northern Germany, the closure of drainage systems and high precipitation may cause an increase in the water table (Svoboda et al., 2015; Zimmer et al., 2016), which can lead to reductive conditions. Arable soils on a single slope (catena) display different characteristics depending on slope position. For example, the toe slope position soil may have longer periods of water saturation due to rising groundwater level than the upper slope soils. Also, the subsoil might be more affected by water saturation than the topsoil. These in situ environmental conditions do not only affect soil properties but may also affect the mobilization of P in arable soils. Particularly under intensive applications of P fertilizers and/or manure the risk of P loss in these soils under changing environmental conditions may be increased. Consequently, in this study we investigated soil samples from the top- and subsoil of a toe-, middle-, and upper-slope arable soil profile to study P mobilization under different redox conditions.
We hypothesize that redox changes from reducing to oxidizing conditions and vice versa in groundwater affect arable soils as a result of water table fluctuations governing the release of P and its mobilization, through the direct impact of EH and/or the associated changes of soil pH, Fe–Mn oxides and DOC/DIC. We also hypothesize that if soil conditions become reducing, the P bound to the Fe and Mn-(oxhydr)oxides might be released due to the dissolution of these oxides. Also, we assume that redox-induced changes in soil organic and inorganic carbon affect P solubility and that the decomposition of SOM under reducing/oxidizing cycles leads to the release of P into soil solution. Moreover, we hypothesize that the slope position affects the water table level and thus affects the redox-induced mobilization of P in a soil catena differently. Therefore, our aim was to study the impact of rising groundwater level and the associated changes in EH, pH, Fe–Mn–Al-(oxhydr)oxides, DOC and DIC concentrations on P mobilization in the top- and sub-soil horizons of toe-, mid-, and upper-slope arable soil profiles.
Section snippets
Soil sampling and characterization
In a field at Dummerstorf, near Rostock, Germany, soil samples were collected from three soil profiles excavated by drilling along a slight slope at different positions (toe-, mid-, and upper-slope) i.e. different distances to groundwater (Baumann et al., 2020b). At each soil profile, four soil replicates were sampled from three horizons at different depths (Appendix A; Table S1). Soil classification, basic soil properties, and total element content as well as content of poorly crystalline
EH/pH dynamics
The EH of all soil samples ranged from −280 mV to +485 mV (Fig. 1). The toe slope soil samples showed a wider range of EH (−280 to +471 mV) than the mid slope (−272 to +442 mV) and the upper slope topsoil (UST) samples (−230 to +485 mV) (Fig. 1; Table 1). The EH range differed between the soil horizons; the toe slope subsoil (TSS) sample reached a lower EH value (−280 mV) than the toe-slope topsoil (TST) sample (−232 mV), while both the mid slope top- (MST) and sub-soil (MSS) sample showed
Conclusions
The release of P in groundwater affected arable soils might increase under high precipitation and surface irrigation if drainage is restricted, which may increase the ground water level and cause reductive conditions. Reducing acidic conditions increased P mobilization up to 30 folds and thus may cause increased leaching if the groundwater level increases in the soils under study. Therefore, mitigating the potential loss of P under reducing acidic conditions using low cost and environmentally
Credit author statement
Sabry M. Shaheen: Performing the experiment, Writing – original draft. Jianxu Wang: Performing the experiment, Software and visualization. Karen Baumann: Editing and proof reading. Shan-Li Wang: Editing and proof reading. Peter Leinweber: Review, editing, and proof reading. Jörg Rinklebe: Concept, Supervision, review, editing, and foundation
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
We thank the German Federal Ministry of Education and Research (BMBF) who funded the InnoSoilPhos-project (http://www.innosoilphos.de/default.aspx), in the frame of the BonaRes-program (No. 521 031B0509A). Also, we thank the team of Laboratory of Soil- and Groundwater-Management at Wuppertal University for the technical support.
References (38)
- et al.
Dissolution of phosphorus into pore-water flowing through an organic soil
Geoderma 197–
(2013) - et al.
Dynamics of phosphorus fractions in surface soils of different flooding wetlands before and after flow-sediment regulation in the Yellow River Estuary, China
J. Hydrol.
(2020) - et al.
Phosphorus enriched effluents increase eutrophication risks for mangrove systems in northeastern Brazil
Mar. Pollut. Bull.
(2019) - et al.
Differences in main processes to transform phosphorus influenced by ammonium nitrogen in flooded intensive agricultural and steppe soils
Chemosphere
(2019) - et al.
Distribution and release of phosphorus fractions associated with soil aggregate structure in restored wetlands
Chemosphere
(2019) - et al.
Controlled variation of redox conditions in a floodplain soil: impact on metal mobilization and biomethylation of arsenic and antimony
Geoderma
(2011) - et al.
Fe-Mn concretions and nodules formation in redoximorphic soils and their role on soil phosphorus dynamics: current knowledge and gaps
Catena
(2019) - et al.
Respective roles of Fe-oxyhydroxide dissolution, pH changes and sediment inputs in dissolved phosphorus release from wetland soils under anoxic conditions
Geoderma
(2019) - et al.
Redox-induced mobilization of Ag, Sb, Sn, and Tl in the dissolved, colloidal and solid phase of a biochar-treated and un-treated mining soil
Environ. Int.
(2020) - et al.
Release of As, Ba, Cd, Cu, Pb, and Sr under pre-definite redox conditions in different rice paddy soils originating from the U.S.A. and Asia
Geoderma
(2016)
Inorganic phosphorus forms in some Entisol and Aridisol of Egypt
Geoderma
Flooding effects on soil microbial communities
Appl. Soil Ecol.
Preliminary investigation of phosphorus adsorption onto two types of iron oxide-organic matter complexes
J. Environ. Sci.
Effect of organic matter on phosphorus adsorption and desorption in a black soil from Northeast China
Soil Tillage Res.
Advancement in soil microcosm apparatus for biogeochemical research
Ecol. Eng.
Redox-dependent phosphorus burial and regeneration in an offshore sulfidic sediment core in North Yellow Sea, China
Mar. Pollut. Bull.
Loss of soil phosphorus by tile drains during storm events
Agric. Water Manag.
Long-term hydrologic impact assessment of non-point source pollution measured through land use/land cover (LULC) changes in a tropical complex catchment
Earth System and Environment
Phosphorus cycling and spring barley crop response to varying redox potential
Vadose Zone J.
Cited by (17)
Effects of freeze-thaw cycling on the engineering properties of vegetation concrete
2023, Journal of Environmental ManagementNutrient potentiate the responses of plankton community structure and metabolites to cadmium: A microcosm study
2022, Journal of Hazardous MaterialsStepwise redox changes alter the speciation and mobilization of phosphorus in hydromorphic soils
2022, ChemosphereCitation Excerpt :This equipment enables the simulation of various anoxic/oxic directions that may occur in the soils when the groundwater level changes. This happens by adjusting the EH automatically using addition of nitrogen gas to lower EH or synthetic air/oxygen to increase EH (Yu and Rinklebe, 2011; Frohne et al., 2011; Rinklebe et al., 2016, 2020; Shaheen et al., 2014b, 2021). Briefly, glass vessels were used in triplicate for the TS and MS and in duplicate for the US.