METHODS AND PLATFORMS 



The sensor operates by equilibrating a colorimetric pH indicator with the seawater C0 2 

 and recording the color of this solution in a fiber optic flow cell. The sensor is designed for 

 autonomous operation on moorings although it may also be used on CTD's or towed platforms. 



STRENGTHS AND LIMITATIONS OF PROPOSED RESEARCH 



The sensor instrument is simple, durable, low power, and relatively inexpensive ($5-6K). 

 It operates with precision similar to the conventional Li-Cor infrared C0 2 analyzers and does not 

 require gas-phase equilibration. The long-term stability is very promising although it has not yet 

 been evaluated for a full 3 month period. Fouling was not a problem during low productivity 

 periods (winter and spring 1994). We'll see what happens as the water warms up. 



STATUS OF RESEARCH 



An autonomous C0 2 sensor instrument has been designed, built, and extensively 

 evaluated. Initial tests were performed in a shallow flow through seawater tank for a 12 day 

 period. These results were very comparable to the Li-Cor/equilibrator data taken over the same 

 period. The instrument has now operated continuously for three weeks (over 1000 measurements) 

 suspended off the WHOI dock in two meters of water. These results also appear very good 

 although they have not yet been fully examined. This instrument and perhaps one other will be 

 prepared for a month-long deployment off Cape Hatteras in August 1994. 



Keywords: carbon dioxide, pC0 2 , moored sensors 



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