title: Autonomous in situ measurements of seawater alkalinity.
abstract: Total alkalinity (AT) is an important parameter for describing the marine inorganic carbon system and understanding the effects of atmospheric CO2 on the oceans. Measurements of AT are limited, however, because of the laborious process of collecting and analyzing samples. In this work we evaluate the performance of an autonomous instrument for high temporal resolution measurements of seawater AT. The Submersible Autonomous Moored Instrument for alkalinity (SAMI-alk) uses a novel tracer monitored titration method where a colorimetric pH indicator quantifies both pH and relative volumes of sample and titrant, circumventing the need for gravimetric or volumetric measurements. The SAMI-alk performance was validated in the laboratory and in situ during two field studies. Overall in situ accuracy was -2.2 ± 13.1 μmol kg(-1) (n = 86), on the basis of comparison to discrete samples. Precision on duplicate analyses of a carbonate standard was ±4.7 μmol kg(-1) (n = 22). This prototype instrument can measure in situ AT hourly for one month, limited by consumption of reagent and standard solutions.
authors: Sunburst Sensors, 1226 W Broadway, Missoula, Montana 59802, United States.
authors: Reggie S
authors: RS
authors: Spaulding
authors: Michael D
authors: MD
authors: DeGrandpre
authors: James C
authors: JC
authors: Beck
authors: Robert D
authors: RD
authors: Hart
authors: Brittany
authors: B
authors: Peterson
authors: Eric H
authors: EH
authors: De Carlo
authors: Patrick S
authors: PS
authors: Drupp
authors: Terry R
authors: TR
authors: Hammar
mesh_terms: D002244:Carbon / Q000032:analysis; D002245:Carbon Dioxide / Q000032:analysis; D003124:Colorimetry / Q000379:methods; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods*; D006254:Hawaii; D006863:Hydrogen-Ion Concentration; D009792:Oceans and Seas; D009922:Oregon; D015203:Reproducibility of Results; D012623:Seawater / Q000032:analysis* / Q000737:chemistry*
chemical_list: D002245:Carbon Dioxide; D002244:Carbon