A novel approach to measure nutrient fluxes in permeable sediments

在地球仪周围，沿海海洋极为重要，因为它为环境、社会和经济提供了关键功能。沉积物在沿海生态系统的健康中发挥着重要作用，因为它们能够转化、储存和释放影响和控制生命的化合物。例如，沉积物是氧气的一个主要汇，但也有人认为，沿海沉积物在营养物的再循环方面非常重要，这一过程控制着初级生产，但也在沿海沃茨藻类大量繁殖或低氧条件的产生中发挥作用。然而，由于许多海岸沉积物的特定地球物理特征，（即，它们通常由松散的沙粒组成），量化沉积物和水柱之间的营养物交换的测量非常困难，因此这些桑迪沉积物中的营养物的再循环能力不能很好地量化，在这里，我们提出了一个概念验证研究，以开发一种新的能力，以量化不同类型的桑迪沉积物和水柱之间的营养物质交换。为了实现这一目标，我们将采用一种众所周知的技术来测量沉积物和水柱之间的氧气交换（即所谓的底栖室）。我们将为这些通量交换记录仪配备新型微型传感器，这些传感器可以自动测量封闭水体中的营养物浓度。我们还将把它们与测量水流和沉积物床特性的传感器集成在一起。我们首先将在实验室中验证新方法的功能，然后在现实世界中演示它。为此，我们选择了沿着英国南海岸的一个地区，该地区以农业排放、废水、城市径流和下水道溢流造成的高营养水平而闻名，历史上高营养投入已经导致了藻类大量繁殖和水柱中的低氧浓度。这种新的能力可以产生维持健康环境和管理我们的自然资源所迫切需要的知识，从长远来看，可以适用于测量其他地球化学物种，例如其他污染物和不同环境。

Around the globe, the coastal ocean is of immense importance, as it provides critical functions for the environment, society and economy. Sediments play a fundamental role in the wellbeing of the coastal ecosystems as they are able to convert, store and release chemical compounds that affect and control life. For example, sediments are a major sink for oxygen, but it is also suggested that coastal sediments are very important in the recycling of nutrients, a process that controls primary production, but also plays a role in the production of algal blooms or low oxygen conditions in coastal waters. However, due to the specific geophysical characteristics of many coastal sediments (i.e. they often are composed of loose sand grains), measurements that quantify the nutrient exchange between the sediments and water column are very difficult and hence the recycling capacity of nutrients in these sandy sediments is not well quantified, even though it is likely to be highly important.Here we propose a proof-of-concept study to develop a new capability to quantify the exchanges of nutrients between different types of sandy sediments and the water column. To achieve this, we will adapt a well-known technique to measure oxygen exchange between sediments and the water column (i.e. so called benthic chambers). We will equip these flux exchange recorders with novel miniaturized sensors that autonomously can measure nutrient concentrations in an enclosed volume of water. We will also integrate them with sensors measuring water flow and sediment bed properties. We first will verify the functioning of the new approach in the laboratory and then demonstrate it in a real-world scenario. For this we have chosen an area along the UK South Coast, that is known for high nutrient levels, caused by agricultural discharges, wastewater, urban runoff and sewer overflows, and where high nutrient inputs historically already led to algal blooms and low oxygen concentrations in the water column. This novel capacity can produce knowledge that is urgently needed to sustain a healthy environment and manage our natural resources and on the longer-term can be adapted to measure other geochemical species, e.g. other pollutants and in different environments.