TransSAPs - How the spatio-temporal transformation of superabsorbent polymers (SAPs) alters soil processes

• Applicant: Dr. Christian Buchmann
• Subject Area: Soil Sciences ; Plant Cultivation, Plant Nutrition, Agricultural Technology ; Preparatory and Physical Chemistry of Polymers
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 497769016

The present project aims to investigate how and to what extent agricultural soil amendments in the form of superabsorbent polymers (SAPs) can be converted into plastic-like solid residues (SAP-SR), modulating fundamental, physicochemical soil properties. Since the primary application goals of SAPs are to optimize water-holding capacity, hydraulic conductivity, and mechanical soil stability, we aim to investigate and understand how the aging or potential transformation of SAPs to SAP-SR permanently alters these properties and processes. This would allow us to understand and clarify whether the original purpose of SAPs and their typically cited benefits are maintained, permanently reduced, or even reversed to the negative despite their aging or conversion. To answer these questions, targeted experiments will be conducted on the degradation and transformation potential of various commonly used synthetic SAPs under different incubation conditions and in different soils. Simultaneously, the associated changes in fundamental physicochemical soil properties will be recorded and linked to relevant degradation and transformation processes of the SAPs. The necessary knowledge and appropriate techniques will be obtained from previous and currently ongoing projects dealing with the contribution of synthetic and biopolymers on soil properties and functions. Within the project, we will apply already established methods such as one (1D), two (2D) dimensional and field gradient (PFG) 1H NMR relaxometry, rheometry, differential scanning calorimetry (DSC), pyrolysis GC-MS (Pyr-GC-MS) and various imaging techniques (electron microscopy (ESEM) and X-ray microtomography (μCT)). Once it has been clarified how and under which conditions SAP-SR structures are formed and which of their original physicochemical properties are fundamentally altered, the associated effects on plant growth and rhizosphere dynamics will be qualitatively and quantitatively assessed in controlled greenhouse experiments. The results of the project will thus allow conclusions to be drawn about the long-term behavior, fate, and efficacy of SAPs based on altered soil processes and soil physicochemical properties.

• DFG Programme: Research Grants
• Co-Investigator: Professorin Dr. Gabriele Schaumann