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| DOI：10.13522/j.cnki.ggps.2017.11.006 |
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| Simulating the Transport and Transformation of Non-point Contaminants in Paddy Field within a Irrigated District |
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LI Yuqing， ZHANG Cun， ZHANG Wenxian
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Xizang Agriculture and Animal Husbandry College, Nyingchi 860000, China
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| Abstract: |
| Simulating transport and transformation of contaminantsin irrigated paddy fields is essential to understand the mechanisms underlying their movement and accumulation, providing guidance to remediation strategies. In this paper, we divided paddy field water into surface and subsurface waters. The leaching of surface water and the dissolved solute NH4+, NO3- and PO43- within it were calculated using water-balance method. Water in the soil was simulated numerically from transient flow equation, from which we calculated the discharge rate to drainage ditch. Water flow in the drainage network was simulated using the wave equation and the biochemical reaction of the solutes was described by first-order kinetics. We then applied the model to Qianguo Irrigation District. The data measured over 2008—2009 were used to estimated the model parameters, and the model was validated against the data measured in 2010. The results showed that the model was capable of reproducing the breakthrough curves of these solutes in both surface and subsurface water. The Nash-Sutcliffe coefficient of the concentrations of NH4+, NO3- and PO43- simulated from the model was 0.772, 0.758 and 0.709 respectively, with their associated root-mean-square error being 0.645, 0.70 and 0.854 and relative root-mean-square error being 0.072, 0.060 and 0.031 respectively. |
| Key words: agricultural non-point source pollution; rice irrigation district; first order kinetic equation; simulation |
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