寒冷气候下冻融作用对水陆交错带磷素迁移转化的影响机制研究

Phosphorus is one of the main nutrients in terrestrial and aquatic ecological system, the quantitative variations of which in farmland soils and surface water have long been a hot issue in the field of ecological environment. The freezing and thawing affects processes of phosphorus transport and transformation between the soil and the water. In recent years, phosphorus exchanged frequently between soil and water due to climate of winter anomaly in China. In this study we choose the aquatic-terrestrial ecotone as areas of interest, focus on the influence mechanism of phosphorus transport and transformation processes at the water-soil interface under action of freeze-thaw. The coupling effect between the freeze-thaw cycling and the interface characteristics will be determined. The change of the content and forms of phosphorous in system will be identified by the laboratory and site tests, the isotope tracing technology and the sorption-desorption experiments. The kinetics of the movement of phosphorus in system will be confirmed. The eco-environment effect and spatial distribution pattern of phosphorus in the aquatic-terrestrial ecotone will be analyzed. The research is very useful to give a preliminary insight into the geochemical behaviors of phosphorus in this system in winter,which complement and make further improvement for phosphorus recycling theory on seasonal scales.

磷素是陆生和水生生态系统的重要生源要素之一，其在农田土壤和地表水体的丰缺变化一直是生态环境研究领域的热点问题，而土壤和水体的冻结融化影响着磷在水土之间的迁移转化过程。近年来，我国冬季气候变化异常，冻融作用对磷素活动的影响更加强烈，本研究以水陆交错带为切入点，作为研究区域，围绕冻融作用对磷在水-土界面迁移过程和赋存形态变化的影响机制这一核心科学问题，以冻融循环-水/土界面性质-磷素形态转化-水体和土壤中磷素迁移过程为研究主线，通过原位试验和室内模拟，综合利用同位素示踪技术、吸附解吸实验和磷形态分析法，确定冻融循环与水-土界面性质改变的耦合关系，探讨水陆交错带磷素在冻融作用下的赋存形态变化规律，明确磷在水-土邻界体系迁移动力学过程，初步揭示冻融作用下水陆交错带中磷迁移转化的时空过程及其生态环境效应。本研究有利于认识和了解磷素在冬季特异时空环境下的地球化学过程，在季节尺度上补充和完善磷循环理论。

本研究围绕冻融作用对磷在水-土界面迁移过程和赋存形态变化的影响机制这一核心科学问题，以冻融循环—水/土界面性质—磷素形态转化—水体和土壤中磷素迁移过程为研究主线，通过原位试验和室内模拟，综合利用同位素示踪技术、吸附解吸实验和磷形态分析法，明确了磷在水-土邻界体系迁移动力学过程，初步揭示了冻融作用下水陆交错带中磷迁移转化的时空过程及其生态环境效应。吸附实验的一级动力学方程、准二级动力学方程和二级动力学方程被用来描述沉积物对磷的吸附随时间变化规律，结果表明沉积物对上覆水磷吸附饱和时间为24h，吸附速率为0.02mg/（g•h），且拟合的吸附容量达到0.06 mg/g；冻融循环次数越多，岸坡土壤吸附能力越弱，但是水下土壤却与之相反，冻融循环次数越多，吸附磷的能力越强，平衡吸附量最高值是0.064mg/g，平衡吸附量最低值是0.031mg/g；同位素示踪实验表明，水体中的磷酸吸附进入岸边下层土壤，随后进一步进入岸边上层土壤。本研究有利于认识和了解磷素在冬季特异时空环境下的地球化学过程，在季节尺度上补充和完善磷循环理论。