应用CNMM-DNDC模拟小流域土壤水力侵蚀和颗粒态碳氮磷迁移

Simulation of water-induced erosion and transport of particulate elements in a catchment by extending the CNMM-DNDC model

摘要

摘要:水力侵蚀是我国分布最广、危害最严重的水土流失类型, 由此导致的土壤和生源要素流失会引起土壤质量下降、河流湖泊富营养化等生态环境问题。水文生物地球化学模型水力侵蚀过程的优化, 对定量评估水力侵蚀强度并识别其空间分布特征具有重要意义。因此, 本研究以土壤水力侵蚀物理模型ROSE为基础, 在分布式流域水碳氮耦合模型CNMM-DNDC中拓展了土壤水力侵蚀流失和颗粒态碳氮磷元素富集模块。以川中丘陵区盐亭截流紫色土农林复合小流域(简称“截流小流域”)为例, 开展了地块尺度验证和小流域尺度的土壤水力侵蚀和颗粒态碳氮磷流失的高时空分辨率模拟应用。结果表明: 增加了土壤水力侵蚀和颗粒态碳氮磷富集模块的CNMM-DNDC模型, 能够较好地模拟截流小流域玉米-小麦轮作径流小区产沙量和颗粒态氮流失量的季节动态特征, 模型验证阶段模拟值和观测值均表现出显著线性拟合关系( R ²分别为0.83和0.85), 改进的CNMM-DNDC模型能够用于模拟评估流域水土流失和颗粒态碳氮磷流失强度空间分布。截流小流域由地表径流引起的土壤水力侵蚀、颗粒态碳氮磷流失强度与土地利用和地形特征密切相关, 其中坡耕地和居民区土壤水力侵蚀最严重, 同时也是截流小流域颗粒态碳氮磷流失的主要来源。模型的模拟结果显示, 2004—2006年截流小流域栅格尺度土壤侵蚀模数均值分别为400 t∙km ⁻²∙a ⁻¹、701 t∙km ⁻²∙a ⁻¹和1550 t∙km ⁻²∙a ⁻¹, 属于轻度水力侵蚀区域。2004—2006年截流小流域由水力侵蚀引起的颗粒态碳年总流失量的平均值分别为63.9 kg(C)∙hm ⁻²∙a ⁻¹、107.2 kg(C)∙hm ⁻²∙a ⁻¹和200.2 kg(C)∙hm ⁻²∙a ⁻¹, 同期颗粒态氮年总流失量的平均值分别为6.3 kg(N)∙hm ⁻²∙a ⁻¹、10.5 kg(N)∙hm ⁻²∙a ⁻¹和19.5 kg(N)∙hm ⁻²∙a ⁻¹, 颗粒态磷年总流失量平均值分别为0.9 kg(P)∙hm ⁻²∙a ⁻¹、1.5 kg(P)∙hm ⁻²∙a ⁻¹和2.8 kg(P)∙hm ⁻²∙a ⁻¹。本研究拓展了CNMM-DNDC模型对土壤水力侵蚀产沙和随之的颗粒态碳氮磷迁移的模拟功能, 为水土流失和面源污染的研究和防控提供先进的模型工具。

Abstract:Water-induced erosion is one of the most widely distributed and severely impaired types of soil and water loss in China. Particulate carbon (C), nitrogen (N), and phosphorus (P) losses associated with soil erosion has led to several environmental problems, such as a decline in soil fertility and eutrophication of rivers and lakes. Quantitative assessment of soil erosion intensity and the identification of soil erosion spatial distribution characteristics are of great significance for control of soil and water loss and prevention of non-point source pollution. In this study, based on a well-applied soil erosion physical model of ROSE, we extended several modules of simulating the soil erosion loss and particulate C/N/P enrichments in a catchment-scale hydrology and biogeochemistry coupled model of CNMM-DNDC to simulate soil erosion and particulate C/N/P losses at a high spatiotemporal resolution on the scales of plots and catchments. For instance, the Jieliu catchment in Yanting County, Sichuan Province was used for model verification and application. The results indicated that the CNMM-DNDC with soil erosion extension performed well in simulating the seasonal dynamics of sediment yield ( R ²=0.83, RMSE=32.0%) and particulate N loss ( R ²=0.85, RMSE=88.0%) in the runoff plot with a maize-wheat rotation in the Jieliu Catchment. Therefore, the extended CNMM-DNDC model was able to simulate and evaluate the spatial distribution of soil erosion and particulate C/N/P loss intensity in the catchment. The soil erosion and particulate C/N/P loss intensity caused by land surface runoff are related to land use types and topographical features of the catchment, where severe soil erosion and high particulate C/N/P loss came from sloping cultivated lands and residential areas. From 2004 to 2006, the simulated soil erosions in the Jieliu Catchment were 400, 701, and 1550 t∙km ⁻²∙a ⁻¹, respectively, and were classified as the low erosion category. Meanwhile, the simulated annual particulate C losses caused by the water-induced erosion in Jieliu in 2004, 2005 and 2006 were 63.9, 107.2, and 200.2 kg(C)∙hm ⁻²∙a ⁻¹, respectively. Consequently, the simulated annual particulate N losses from 2004 to 2006 were 6.3, 10.5, and 19.5 kg(N)∙hm ⁻²∙a ⁻¹, respectively; and the simulated annual particulate P losses were 0.9, 1.5, and 2.8 kg(P)∙hm ⁻²∙a ⁻¹, respectively. This study extended the erosion functionality of the CNMM-DNDC model in terms of simulating soil sediment yield and particulate C/N/P loss and can provide useful supporting tools for the research and control of soil erosion and non-point source pollution.

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