A novel technology to understand environmental changes in marine sediments

众所周知，海洋非常重要，因为它对气候、天气、全球粮食安全、公共卫生和经济都有影响；然而，目前对海洋日益增加的压力导致了看不见的污染程度和全球重要化学循环的改变。从海岸到深海，海底大部分被松散聚集的沉积物覆盖。这些沉积物形成了地球上最大的生物反应器之一，在海洋环境的状态和健康中发挥着至关重要的作用，因为它们转化、储存和释放影响和控制生命的化合物。例如，它们促进强效温室气体的产生，是氧气的主要汇，但也循环利用营养物质并保留污染物。这些生物地球化学反应导致沉积物上部厘米到分米范围内化合物的陡峭梯度，这可以用来了解沉积物中的过程，它们对全球生物地球化学循环的影响以及它们对海洋环境的影响。然而，传统的分析方法往往不能很好地解决这些梯度，无论是在空间上还是在时间上，它们经常在沉积物收集过程中受到干扰；此外，这些测量既昂贵又耗时。在SANDMAN项目中，我将开发一种新的仪器，通过将尖端的芯片实验室传感器与深海平台技术相结合，直接测量海底沉积物（特别是孔隙水）中重要生物地球化学化合物的梯度，如营养物质（硝酸盐、磷酸盐）、金属（铁）和碳酸盐系统参数（总碱度），这种技术可以在海洋的极端环境中运行更长时间。芯片实验室传感器在自动化微流控平台上使用小型化标准实验室分析，由国家海洋学中心开发，直到最近才可用于长期应用。这些传感器非常适合直接测量沉积物中孔隙水的化学性质，因为它们非常节能，可以部署长达一年，并且只使用很少的样样量，因此沉积物中的陡峭梯度可以很容易地解决。在SANDMAN项目中，我将领导传感器适应和调整硬件，以适应沉积物的条件，设计流体采样系统，将孔隙水从沉积物的固相中分离出来，并将这些组件组合在一个独特的海底仪器中。该仪器的功能将首先在受控的实验室环境中进行测试，然后在沿海试验站进行测试，然后将用于回答有关目前未开发地区（如可渗透的沿海沉积物和深海海沟）中与营养物质和金属回收以及碳降解有关的过程的科学重要问题。这种独特的观测仪器可以将我们迫切需要的底栖生物地球化学分析的能力从依赖人类的单点和昂贵的采样转变为基于技术的长期，高质量和可靠的远程生物地球化学测量方法。SANDMAN系统将广泛适用于从海岸到深海，从极到极的海洋监测和工业应用。因此，它将为新的海底天气观测铺平道路，为政府/非政府组织、工业界、科学家和公众等利益攸关方提供关于环境健康和潜在危害的支持和信息。

It is well established that the ocean is of enormous importance as it has an impact on climate, weather, global food security, public health and the economy; however, currently the increasing pressure on the ocean results in unseen levels of pollution and alterations of globally important chemical cycles. From the coast to the deep sea the ocean floor is largely covered by loosely aggregated sediments. These sediments form one of the largest bioreactors on Earth and play a crucial role in the state and health of the marine environment as they convert, store and release chemical compounds that affect and control life. For example, they promote the production of potent greenhouse gases and are a major sink for oxygen, but also recycle nutrients and retain pollutants. These biogeochemical reactions lead to steep gradients of chemical compounds in the upper centimetre to decimetre of the sediments, which can be used to understand the processes proceeding in the sediment, their effects on the global biogeochemical cycles and their impact on the marine environment. However, with traditional analysis methods these gradients can often not be properly resolved, both spatially and temporally, and they are often disturbed during the collection of the sediment; in addition, these measurements are costly and time-consuming.In the SANDMAN project I will develop a new instrument to measure gradients of important biogeochemical compounds, such as nutrients (nitrate, phosphate), metals (iron) and carbonate system parameters (total alkalinity) directly within the seafloor sediment, in particular the porewater, by combining cutting-edge Lab-on-Chip sensors with deep sea platform technology that can operate in extreme environments in the oceans over longer periods of time. The Lab-On-Chip sensors, which use miniaturized standard laboratory analyses on an automated microfluidic platform, are developed at the National Oceanography Centre and only recently became available for longer-term applications. These sensors are ideal for measuring the chemistry of porewater directly in the sediment as they are very energy efficient and can be deployed for up to a year and only use very little sample volume, hence the steep gradients in the sediment can easily be resolved. During the SANDMAN project I will lead the sensor adaptation and adjustment of the hardware for conditions in sediments, the design of a fluid sampling system to separate the porewater from the solid phase of the sediment and the combination of these components in a unique seafloor instrument. The functionality of this instrument will first be tested in a controlled laboratory environment, then in a costal test station and afterwards it will be used to answer scientifically important questions about the processes linked to nutrient and metal recycling and carbon degradation in currently underexplored areas such as permeable costal sediments and deep-sea trenches. This unique observing instrument can transform our capacity for the urgently needed benthic biogeochemical analysis from a human-dependent, single-point and costly sampling to a technology-based long-term, high-quality and reliable approach for remote biogeochemical measurements. The SANDMAN system will be widely applicable from the coast to the deep sea and from pole to pole for marine monitoring and industrial applications. Thus it will pave the way to novel synoptic seafloor observations, providing data to support and inform stakeholders, such as government/non-governmental organisations, industries, scientists and the general public, on environmental health and potential hazards.