Chemical sensor program
Project Manager/Lead Engineer: Luke Coletti
Lead Scientist: Ken Johnson

The goal of the Chemical Sensor Laboratory is to develop a suite of chemical sensors for dissolved constituents in seawater. Development of such sensors is critical to the successful implementation of ocean observatories. The primary focus of our work in 2000 and 2001 has been the development of In Situ Ultraviolet Spectrophotometric (ISUS) sensors. We have completed development of the basic system and validated the performance of the instrument for nitrate and bisulfide measurements in a number of oceanographic studies. This includes deployments on towed, undulating vehicles, CTD profilers, long-term deployments on deep-sea moorings and deployments from the ROV Ventana. 

During 2002, we will continue to explore new types of analyses and environments in which this instrument can be deployed. These areas include high precision measurements of pH for carbon cycle studies using colored indicator dyes and applications using liquid core waveguides to enhance the sensitivity of nitrate analyses in oligotrophic waters. Application of the ISUS to fine scale profiling of nitrate and sulfide concentrations within marine sediments will also be an area we examine. Finally, we will begin planning for a large scale, externally funded project that will highlight the capabilities of the ISUS instrument.

In addition to efforts with ISUS, we will continue to explore the development of other chemical sensing systems. We have worked extensively with the solenoid-pumped, submersible chemical analyzers that were developed in our laboratory. The primary effort in 2000 and 2001 has focused on nitrate analyses in highly colored estuarine waters, where ISUS performance is degraded. Our efforts in 2002 with this instrument will focus on adapting the instrument to perform in situ trace element measurements and for phosphate and silicate analyses. We will also examine novel modes of operation for the instrument that take advantage of its flexibility. These new operating modes are intended to reduce reagent consumption and extend instrument endurance.  Finally, we will continue to test the feasibility of using the OSMOSamplers to collect uncontaminated seawater samples for time series studies in the upper ocean.