灌区硝态氮反硝化的空间变异规律及其参数和过程的数据驱动技术研究

Field experiments have proven the spatial variability of denitrification process. Planting structure, irrigation and drainage further aggravate the variability. Ignoring the spatial variability of denitrification will not be able to scientifically reveal the accumulation and degradation features of nitrate, and not able to accurately assess the impact of agricultural activities on the ecological environment in irrigation district. This study focuses on three major objectives: Firstly, to reveal the variability patterns of denitrification process under general conditions, including various planting structures, various cultivation ages and different irrigation and drainage practices; Secondly, to quantify the causes of denitrification variability by combining surface-ground hydrologic process, soil structure evolution process, dissolved oxygen and organic matter transport process, and biogeochemical process; Thirdly, to develop data-driven modeling technique for spatial variable denitrification process. Multiple types of measurement data are integrated to inverse heterogeneous parameters and to calibrate the denitrification process. Benefit-Cost analysis is implemented to explore the most valuable data. This study is helpful to optimize the plating structure, and irrigation and drainage practices, so the nitrate accumulation trend can be depressed or reversed.

野外试验已经证实了反硝化空间变异性的存在；种植结构、灌溉排水等农业活动加剧了反硝化过程的空间变异性。忽略该空间变异性不利于科学地揭示灌区硝态氮的累积和降解规律，也不能准确地评估农业活动对灌区生态环境的影响。本项目的主要研究内容包括：揭示一般条件下（不同种植类型、不同耕作年龄、不同灌排方式等）反硝化过程的空间变化规律；以地表地下水文过程为主体，综合土壤结构演变过程、溶解氧和有机质迁移过程和生物化学过程，实现对反硝化空间变异性的量化表达；开发数据驱动技术，利用多种类型的观测数据，充分发掘数据价值，反演非均匀分布的反硝化系数，校正空间变异的反硝化过程。上述研究可用于指导农业活动，提出优化的种植结构和灌排方式，减少或逆转灌区的硝态氮累积。

本项目立足于准确刻画空间上变异的硝态氮反硝化过程，主要开展了以下研究：通过批试验和土柱试验多角度探讨了土壤干湿条件变化、温度及碳源等因素对硝态氮反硝化过程的影响；以地表地下水文过程为主体，综合土壤结构演变过程、溶解氧和有机质迁移过程和生物化学过程，开发了适合灌区的分布式反硝化模型，实现对反硝化空间变异性的量化表达；发展了反硝化过程的数据驱动技术，建立了基于集合卡尔曼滤波（EnKF）的反应性溶质数据同化模型并耦合高斯过程回归技术，融合了多种类型的观测数据，有效减小了反硝化过程参数及结构上的误差，校正了空间变异的反硝化过程；提出一种耦合了集合卡尔曼滤波的顺序性数据价值评估方法，充分发掘了不同类型数据的价值，可用于指导监测方案。上述研究对指导农业活动、制定优化的种植结构和灌排方式、减少或逆转灌区的硝态氮累计具有重要的指导意义。