Autonomous chemical pore water sensors for measuring benthic fluxes

Programme website: http://inspire-dtp.ac.uk

Project Rationale:
Quantifying the fluxes of chemical species from marine sediments into the oceans is critical for global biogeochemical cycles of many elements that are essential for life, and also for environmental monitoring of anthropogenically influenced ecosystems. The most common method for flux measurements is the extraction of porewater from retrieved sediment cores followed by laboratory analyses. This ex-situ approach has severe limitations as it is prone to contamination, affords poor temporal and spatial resolution and, most importantly, involves expensive ship time and manpower, which restricts measurements to easily accessible environments. Novel Lab on Chip (LoC) sensors overcome these restrictions as they can be used in-situ to measure chemical species autonomously, with high temporal resolution and over long time periods, requiring only miniature sampling volumes. However, LoCs are currently only used for water column chemistry.
This project will develop, test and apply a novel porewater version of LoC sensors to determine porewater concentrations of dissolved iron, manganese, and nutrients in-situ and fully autonomously. For the first time, this will allow long-term measurements that are cost effective and minimally invasive and thus can be used in undersampled regions (e.g. polar seas) and monitoring intensive environments (lakes, coastal seas). Once established, the measurements will revolutionize understanding of biogeochemical cycles in the marine environment analyses.

Methodology:
This PhD project will take advantage of novel LoC sensor technology and adapt it for automated in-situ measurements of reactive pore water species in the sediments. For this the LoC sensor will be adapted for in-situ fluid sampling. Pore fluid will be drawn through a filter into the LoC sensor, where concentrations will be measured and stored. The student will work with a team of engineers to optimize the LoC sensor for pore fluid samples and will test the sensors in the laboratory. This technology will be integrated on a benthic lander with other smart technologies for sediment and bottom water monitoring. The system will be applied in different marine environments for full field testing during dedicated field work. First applications will include the construction of reliable nitrate and iron fluxes in coastal sandy sediments (North Sea), to assess the denitrification capacity of these sediments and their potential to counteract the anthropogenic nitrogen input to the coastal ocean.

Training:
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the National Oceanography Centre (Marine Geoscience and Ocean Technology and Engineering Groups)
Specific training and activities will include adaptation, optimization of sensors, testing of the sensors in the laboratory and field deployment of sensors/analyzers. Beyond the exchanges associated with INSPIRE we anticipate the student will be involved in national and international projects run at NOC and to work with existing collaborators in Germany and elsewhere on this project. NOC offers opportunities for graduate students to participate in seagoing scientific research expeditions as part of their wider training.