Phosphorus release from alkaline soils to floodwater under simulated spring snowmelt conditions

淡水湖泊中磷浓度升高可能引发有毒蓝绿藻的过度生长，这是影响五大湖、温尼伯湖和北美许多其他湖泊的主要环境问题。 有毒藻华会导致鱼类和其他动物死亡，也可能威胁人类健康。在以农业为主的景观中，农田径流可能会为湖水提供大量的磷。由于相对平坦的地形，沿着缓慢渗透的重粘土，大草原的大多数农业土壤排水不良。在春季融雪期间，这些土地经常被洪水淹没几天到几周不等。长时间的洪水使土壤缺氧，导致土壤厌氧。土壤中的厌氧过程往往会促进磷从土壤中释放到洪水中。这种效应在富含铁的酸性土壤中得到了很好的证明;然而，北方大平原典型的碱性和石灰性土壤的信息有限。我们以前的研究表明，在碱性土壤模拟夏季降雨洪水在大多数土壤中的洪水磷浓度显着增加。根据土壤的不同，增加的幅度可高达约15倍。在加拿大大草原，春季融雪径流是土壤磷流失的主要模式，这发生在寒冷的温度下，频繁的冻融事件。虽然增强磷的可用性在土壤中已被很好地记录在室温下的洪水和夏季降雨洪水，有很少的可用信息在春季融雪洪水从土壤中释放磷。拟议的研究将解决这些知识差距。专注于石灰性和非石灰性碱性土壤，我们将通过模拟春季融雪条件，低温和冻融事件产生关于磷释放和动员的新信息。通过一个全面的多年计划的实验室培养和现场微观实验，我们将系统地研究厌氧条件如何改变磷成分在淹水的土壤，以及温度变化和冻融事件对这些变化的影响。然后，我们将研究如何土壤磷成分的变化与磷的释放和动员从土壤到地表洪水在不同时间的洪水。 根据这些信息，我们将开发一个模型，以确定土壤有可能释放大量的磷洪水下春季融雪洪水。所产生的信息和预测模型将在制定养分和水管理指南方面具有价值，可用于最大限度地减少一个地区农业土壤中的磷流失到水道中。

Elevated phosphorus concentrations in freshwater lakes may trigger excessive growth of toxic blue-green algae, a major environmental problem affecting the Great Lakes, Lake Winnipeg and many other lakes across North America. Toxic algal blooms can lead to death of fish, other animals and also may threaten human health. In agriculture-dominated landscapes, runoff from crop fields may contribute significant amounts of phosphorus to lake water. Due to the relatively flat landscape, along with slowly permeable heavy clay soils, most agricultural soils in the prairies are poorly drained. These lands often get flooded for a period ranging from a few days to several weeks during spring snowmelt. Prolonged flooding deprives the soil of oxygen, which results in anaerobic soil conditions. The anaerobic processes in soils tend to enhance the release of phosphorus from soil to floodwater. This effect is well documented for iron-rich acidic soils; however, information for alkaline and calcareous soils, which are typical of Northern Great Plains is limited. Our previous studies using alkaline soils showed a significant increase in phosphorus concentration in floodwater under simulated summer rainfall flooding in majority of soils. The magnitude of increase can be up to about 15-fold depending on the soil. In the Canadian prairies, spring snowmelt runoff is the dominant mode of phosphorus losses from soils, which occurs under cold temperatures with frequent freeze-thaw events. While enhanced phosphorus availability in soil has been well documented for flooding at room temperatures and summer rainfall flooding, there is little available information on phosphorus release from soils during spring snowmelt flooding. The proposed research will address these knowledge gaps. Focusing on calcareous and non-calcareous alkaline soils, we will generate new information on the release and mobilization of phosphorus by simulating spring snowmelt conditions, with cold temperatures and freeze-thaw events. Through a comprehensive multi-year program of laboratory incubation and field microcosm experiments, we will systematically investigate how anaerobic conditions changes phosphorus composition in flooded soils, and the influence of temperature variations and freeze-thaw events on these changes. We will then examine how soil phosphorus composition changes relate to the release and mobilization of phosphorus from soil to surface floodwater at different times of flooding. Based on the information, we will develop a model to identify soils that have the potential to release large quantities of phosphorus to floodwater under spring snowmelt flooding. The information generated and the predictive model will be valuable in developing nutrient and water management guidelines, which can be used to minimize phosphorus losses from the agricultural soils in a region into waterways.**