ABSTRACT
The marine environment has been affected by growing population and industrial pressures in the coastal zone. The first in situ analyzer used in the marine environment was for determining salinity on the basis of measurements of conductivity and temperature. A sensor is defined as a device that produces a response to a change in a physical condition, such as temperature or thermal conductivity, or to a change in chemical concentration. Another approach to achieving in situ measurements has been the miniaturization of existing analytical methods, such as colorimetric and spectroscopic methods. Analyzers based on flow-injection analysis methods for use in situ comprise a pump, detector, and narrow bore tube manifold. A number of spectroscopic- and spectrometric-based in situ devices have been developed for use in marine applications for measuring dissolved gases, nutrients, organic chemicals, and trace metals. Conductometric electrodes are used to measure salinity and are incorporated into a variety of commercially available charge-transfer device instruments.
