土壤有机质和孔隙结构对新型有机污染物在土壤中非饱和迁移和积累的耦合影响

As emerging organic chemicals, such as pharmaceuticals and personal care products (PPCPs), are increasingly produced and used by human being, their release and accumulation in soil and aquatic systems through recycled use of wastewater is becoming a serious problem of environmental security and health. Treated wastewater is widely used for agricultural or landscape irrigation to meet the challenge of water scarcity in many regions of the world. However, many emerging organic pollutants are not completely removed from treatment plants, and some could be accumulated in irrigated soils causing environmental risks. Pore-filled soil organic matter(PF-SOM) may function as a significant natural control of retention, release, and degradation of these chemicals in shallow soils. This research will examine how soil pore system could be altered by PF-SOM, control the fate and transport of four typical emerging organic pollutants in relation to water dynamics. Specifically, we will (1) quantify the effects of fertilizers on the porosity and size distribution of SOM-filled pores (including the interior and blocked portions) and soil water hysteresis using ultra-small and small angle X-ray scattering technique, (2) examine the effects of PF-SOM on the retention, transport, and remobilization of emerging organic pollutants under unsaturated flow conditions, (3) quantify the concentration processes of the emerging organic pollutants as a function of PF-SOM content, pore size and connectivity, and water content and dynamics in soil pores using ultra-small and small angle neutron scattering technique, and (4) utilize novel forward/inverse modeling theory to determine the key processes controlling the mobility of emerging organic pollutants in micro-heterogeneous structured soil. Soils will be taken from a long-term maize experimental site, which has 24 fertilizer treatments. The project will highlight the importance of organic carbon preservation for pollution control in agriculture and will benefit farmers by providing strategic guidance on environmentally beneficial fertilizer application and secure wastewater irrigation.

新型有机污染物如药物制剂和个人护理化学品（统称PPCPs）的使用和通过污水排放及灌溉向环境系统的释放，导致环境的有机污染及其预防成为一个亟待解决的问题。有机污染物在非饱和土壤中的运移是土壤和地下水污染研究中的热点问题，但目前国内外的研究对其迁移和转化过程及其控制机制仍未有明确阐述。本研究以长期定位试验田土壤为研究对象，应用非饱和土柱实验技术和优势互补的超小角/小角X射线和中子散射技术，结合高级数值模型化技术来测定和阐明在不同施肥条件下有机质在土壤中的积累是如何通过影响土壤孔隙系统的孔隙度、孔径分布及连续性来控制不同土壤水分动态条件下有机污染物分子的迁移过程及其相关环境行为。通过从微观孔隙到宏观土柱的跨尺度过程分析与模型模拟，阐明何种农田施肥管理可以通过改善土壤有机质积累和储存方式来控制有机污染物的保持和向环境中的释放，从而增加污水灌溉的生态安全性。

新型有机污染物的使用和通过污水排放及灌溉向环境系统的释放，导致环境的有机污染及其预防成为一个亟待解决的问题。有机污染物在非饱和土壤中的运移是土壤和地下水污染研究中的热点问题，但目前国内外的研究对其迁移和转化过程及其控制机制仍未有明确阐述。本研究以长期定位试验田土壤为研究对象，应用非饱和土柱实验技术和优势互补的超小角/小角X射线和中子散射技术，结合高级数值模型化技术来测定和阐明在不同施肥条件下有机质在土壤中的积累是如何通过影响土壤孔隙系统的孔隙度、孔径分布及连续性来控制不同土壤水分动态条件下有机污染物分子的迁移过程及其相关环境行为。通过从微观孔隙到宏观土柱的跨尺度过程分析与模型模拟，阐明何种农田施肥管理可以通过改善土壤有机质积累和储存方式来控制有机污染物的保持和向环境中的释放，从而增加污水灌溉的生态安全性。.研究结果表明①农田施肥措施影响有机质对土壤孔隙的填充，进而影响土壤孔隙结构、土壤水分滞后性和水分在土壤孔隙中的不均匀分布，土壤微团聚体比大团聚体能更好地保护土壤有机碳，微团聚体中受保护的有机碳可以通过加强有机质的物理封闭和在粉粒（2-50 µm）和粘粒（<2 µm）尺度上与矿物质的胶结及聚合来促进土壤碳库的长期稳定性；②孔隙填充的有机质影响新型有机污染物在土壤中的保持、迁移及降解，土壤有机质主要通过两种机制影响有机污染物的滞留和迁移，其一是通过修饰土壤颗粒的表面化学特征来影响有机污染物吸附强度、容量和界面分子转化，其二是通过修饰土壤结构（例如团聚体形成）和孔隙特征（例如孔隙度、孔隙大小和连续性）来影响有机污染物的在土壤中的迁移和扩散；③非饱和土壤中存在的空气可以增加土壤中的液-气界面面积，从而通过疏水作用增加有机污染物在非饱和土壤中滞留和减少其迁移数量和距离。根据研究结果，我们开发了新颖数学模型，确定了新型有机污染物在土壤中的吸附和移动参数，为预测全国土壤的有机污染物风险提供科学依据。