5:15 PM - 6:30 PM
[HTT16-P14] The incubation method using 18O-water and phosphate oxygen isotope for quantitative evaluation of bioavailable phosphate in soil.
Keywords:Phosphorus dynamics, Soil incubation, Bayesian mixing model
Phosphorus (P) is one of the main limiting factor for primary production and has a significant impact on biogeochemical processes and food production in ecosystems. The amount of bioavailable P in soils is about 1% of total phosphorus, and most of it exists in organic form or tightly bound to clay minerals (Pierzynski et al., 2005). Bioavailable P is formed by physicochemical processes such as adsorption/desorption and precipitation/dissolution, and biological processes such as absorption/release and mineralization of organic P by organisms. To understand bioavailable P dynamics, it is necessary to clarify the fluxes to bioavailable P pool through each processe and factors affecting the processes.
Recently, phosphate oxygen isotope ratio (δ18OPO4) has been used as a promising tool to elucidate the P cycling (Paytan and McLaughlin, 2012). Because the P–O bonds in dissolved inorganic phosphate (DIP) do not easily hydrolyze at typical earth’s surface temperatures and pressures, DIP movement through physicochemical processes maintain the δ18OPO4 values in a reactant pool. In contrast, biological processes mediated by enzymes that cleave the P–O bonds cause large isotopic fractionation. For example, inorganic pyrophosphatase (PPase) associated with absorption/release and phosphatases associated with organic P mineralization can alter the δ18OPO4 signatures. These isotopic fractionations are controlled by water oxygen isotope ratio and temperature. Equations have been proposed to estimate the fractionation (Paytan and McLaughlin, 2012). These facts indicate it is possible to control the δ18OPO4 value of DIP generated by each process by controlling the water oxygen isotope ratio and temperature.
The purpose of this study is to propose a soil incubation experiment using incubation water with two different water oxygen isotope ratios (e.g., +30‰ and -5‰) to quantitatively evaluate the flux of each process to the available P pool. The incubation experiment can simulate a two-isotope system like δ15N-NO3 and δ18O-NO3, and the fluxes of each process can be quantified by Bayesian mixing model. The poster will present the detailed theoretical background, hypothesis, and preliminary results of the study.
Reference
Paytan, A. and McLaughlin, K. (2012) ‘Tracing the Sources and Biogeochemical Cycling of Phosphorus in Aquatic Systems Using Isotopes of Oxygen in Phosphate’, in Baskaran, M. (ed.) Handbook of Environmental Isotope Geochemistry. Berlin, Heidelberg: Springer Berlin Heidelberg, pp. 419–436. doi: 10.1007/978-3-642-10637-8.
Pierzynski, G. M., McDowell, R. W. and Thomas Sims, J. (2005) ‘Chemistry, Cycling, and Potential Movement of Inorganic Phosphorus in Soils’, in, pp. 51–86. doi: 10.2134/agronmonogr46.c3.
Recently, phosphate oxygen isotope ratio (δ18OPO4) has been used as a promising tool to elucidate the P cycling (Paytan and McLaughlin, 2012). Because the P–O bonds in dissolved inorganic phosphate (DIP) do not easily hydrolyze at typical earth’s surface temperatures and pressures, DIP movement through physicochemical processes maintain the δ18OPO4 values in a reactant pool. In contrast, biological processes mediated by enzymes that cleave the P–O bonds cause large isotopic fractionation. For example, inorganic pyrophosphatase (PPase) associated with absorption/release and phosphatases associated with organic P mineralization can alter the δ18OPO4 signatures. These isotopic fractionations are controlled by water oxygen isotope ratio and temperature. Equations have been proposed to estimate the fractionation (Paytan and McLaughlin, 2012). These facts indicate it is possible to control the δ18OPO4 value of DIP generated by each process by controlling the water oxygen isotope ratio and temperature.
The purpose of this study is to propose a soil incubation experiment using incubation water with two different water oxygen isotope ratios (e.g., +30‰ and -5‰) to quantitatively evaluate the flux of each process to the available P pool. The incubation experiment can simulate a two-isotope system like δ15N-NO3 and δ18O-NO3, and the fluxes of each process can be quantified by Bayesian mixing model. The poster will present the detailed theoretical background, hypothesis, and preliminary results of the study.
Reference
Paytan, A. and McLaughlin, K. (2012) ‘Tracing the Sources and Biogeochemical Cycling of Phosphorus in Aquatic Systems Using Isotopes of Oxygen in Phosphate’, in Baskaran, M. (ed.) Handbook of Environmental Isotope Geochemistry. Berlin, Heidelberg: Springer Berlin Heidelberg, pp. 419–436. doi: 10.1007/978-3-642-10637-8.
Pierzynski, G. M., McDowell, R. W. and Thomas Sims, J. (2005) ‘Chemistry, Cycling, and Potential Movement of Inorganic Phosphorus in Soils’, in, pp. 51–86. doi: 10.2134/agronmonogr46.c3.