High‐frequency measurement of seawater chemistry: Flow‐injection analysis of macronutrients
We adapted a commercially available flow‐injection autoanalyzer (Lachat Quik‐Chem 8000) to measure seawater nitrate concentrations at a rate of nearly 0.1 Hz and phosphate and silicate concentrations at a rate half that. Several minor improvements, including reduced sample‐loop size, high sample flu...
| Published in: | Limnology and Oceanography: Methods |
|---|---|
| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
2004
|
| Subjects: | |
| Online Access: | http://dx.doi.org/10.4319/lom.2004.2.91 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.4319%2Flom.2004.2.91 https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lom.2004.2.91 |
| Summary: | We adapted a commercially available flow‐injection autoanalyzer (Lachat Quik‐Chem 8000) to measure seawater nitrate concentrations at a rate of nearly 0.1 Hz and phosphate and silicate concentrations at a rate half that. Several minor improvements, including reduced sample‐loop size, high sample flushing rate, modified carrier chemistry, and use of peak height rather than peak area as a proxy for nutrient concentration aided in the increase in sampling rate. The most significant improvement, however, was the construction of a copperized cadmium NO 3 − reduction column that had a high surface area to volume ratio and a stable packing geometry. Preliminary results from a cruise in the Ross Sea in austral spring of 1997 are shown. Precision of all three analyses is better than 1%. Comparison of the nutrient concentrations determined by the rapid analysis method described here with traditional discrete analyses shows that nitrate and silicate determined by the two approaches are within a few percent of each other, but that the phosphate concentrations determined by the rapid analysis are as much as 10% lower than those determined by the discrete analyses. |
|---|