NSRRC Activity Report 2023

Environmental and Earth Sciences 071 I n recent years, the world has been grappling with a severe food crisis that is largely influenced by factors such as geopolitical dynamics and climate change. Extreme weather conditions such as high temperatures, floods, and droughts experienced globally have led to a year-on-year increase in food prices. Concurrently, regional wars instigated by geopolitical tensions have further aggravated the problem of food supply. As a result, striking a balance between boosting food production (food security) and ensuring food safety has emerged as a critical challenge. In a bid to address this issue, researchers have employed advanced synchrotron radiation technology at the NSRRC to study the mechanisms of specially designed phosphor fertilizers and to investigate how rice absorbs toxic substances from the soil. The significant findings from these studies will contribute to future efforts aimed at enhancing food production and safety, thereby helping to address the global food crisis. Regarding food production, since the Green Revolution, the intensive use of chemical fertilizers has resulted in a significant increase in the consumption of mined phosphorus (P), but only a small proportion of P is effectively used by plants. Concerns about the inefficiency of P uptake and the potential depletion of P ores have led the European Union to classify P rock as a critical resource. Therefore, enhancing the efficiency of P fertilizers in agriculture is of paramount importance. Yu-Ting Liu from National Chung Hsing University, in collaboration with Liang-Ching Hsu from the NSRRC, utilized TPS 44A quick- scanning X-ray absorption spectroscopy (QSXAS), TPS 19A high-resolution powder X-ray diffraction, and TLS 16A1 X-ray absorption near-edge structure (XANES) spectroscopy beamlines to investigate the release mechanism of P from specially designed fertilizer into the soil. 1 Layered double hydroxides (LDHs) are emerging as slow-release P fertilizers. They control the release of phosphate by intercalating within their layers. To address potential P scarcity, the present authors modified Mg–Fe LDHs by incorporating chitosan (CTS) and carboxymethyl cellulose (CMC) to design slow-release P fertilizers. Figure 1 shows the mechanism of P release among various LDHs analyzed using synchrotron QSXAS and XANES techniques. Pristine LDHs had a high phosphate sorption capacity that was slightly lower in hybrids; however, the results show that the 0.5LDH-CTS variant (0.5 M metal precursors hybridized with CTS) released phosphates over 650 hours, outperforming other LDHs. Extended X-ray Fig. 1 : (a) X-ray diffraction patterns of Mg–Fe LDH and that hybridized with CMC and CTS, (b,c) magnitude of Fourier transformed k3 χ(k) data of Fe K-edge extended X-ray absorption fine structure spectroscopy for Mg–Fe LDH and that hybridized with CMC and CTS collected at 0 h and 2688 h during the PO 4 release kinetics; and (d)–(f) results of P K-edge XANES linear combination fitting analysis for Mg–Fe LDH and hybrids of LDH with CMC and CTS collected at specific times during the PO 4 release kinetics. [Reproduced from Ref. 1] Food Security and Food Safety Food production and safety can be effectively improved through control of the soil environment.