Role of water flow in modeling methane emissions from flooded paddy soils |
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| Affiliation: | 1. LBMS (EA 4325) - Brest Mechanics and Systems Laboratory, 29200 Brest, FRANCE;2. SNCF - National Society of French Railways, 93210 La Plaine Saint-Denis, FRANCE;1. Laboratory of Infrared Materials and Devices, The Advanced Technology Research Institute, Ningbo University, Ningbo 315211, China;2. College of Information Science and Engineering, Ningbo University, Ningbo 315211, China;1. Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil;2. Integrar, Capivari do Sul, Rio Grande do Sul, Brazil;3. Federal University of Pelotas, Pelotas, Rio Grande do Sul, Brazil;4. Rio-Grandense Rice Institute, Cachoeirinha, Rio Grande do Sul, Brazil;1. Universidade de Lisboa, Instituto Superior de Agronomia, LEAF, Tapada da Ajuda, Lisboa 1349-017, Portugal;2. Área de Producción Vegetal (Escuela de Ingenierías Agrarias) and IACYS, Universidad de Extremadura, Ctra. de Cáceres, Badajoz 06071, Spain;3. Área de Edafología y Química Agrícola (Facultad de Ciencias) and IACYS, Universidad de Extremadura, Avda de Elvas, Badajoz 06071, Spain;4. Instituto Politécnico de Portalegre, Escola Superior Agrária de Elvas, Apartado 254, Elvas 7350, Portugal;1. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, PR China;2. Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta, T6G2W2, Canada |
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| Abstract: | Methane (CH4) is a potent greenhouse gas that is emitted from paddy fields, and the large CH4 fluxes represent a worldwide issue for the rice production eco-compatibility. In this work a model is proposed to investigate the role of water flows on CH4 emissions from flooded paddy soils. The model is based on a system of partial differential mass balance equations of the chemical species affecting CH4 fate, and water flows are modeled by the Darcy equation. Moreover, in order to properly model the dynamics of CH4, a number of physico-chemical processes and features not included in currently available CH4 emission models are considered: paddy soil stratigraphy; nutrient adsorption and root water uptake; gas transport and respiration within root aerenchyma compartment. The proposed model allows to simulate the spatio-temporal dynamics of chemical compounds within paddy soil as well as to quantify the influence of different processes on nutrient input/output budgets. Simulations without water flow have shown a considerable overestimation of CH4 emissions due to a different spatio-temporal dynamics of dissolved organic matter (DOC – source of energy for CH4 production). In particular, when water fluxes have not been modeled the overestimation can reach 54%, 41% and 67% of daily minimum, daily maximum, and total over the whole growing season CH4 emission, respectively. Moreover, the model results suggest that roots influence CH4 dynamics principally due to their nutrient uptake, while root effect on advective flow plays a minor role. Finally, the analysis of CH4 transport fluxes has shown the limiting effect of upward dispersive transport fluxes on the downward CH4 percolation. |
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