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Carved out by ancient glaciers, the jagged lines of Puget Sound outline Washington State’s most rapidly growing areas. A hub of great economic and environmental significance, the great fjord initially helped place Seattle, WA on the map, and continues to provide vital resources that feed the region’s growth.

With rapid development anywhere in the world, a close watch on environmental impacts is vital. To monitor long-term changes, the King County Department of Natural Resources and Parks has been conducting marine monitoring to assess the baseline conditions and trends in Central Puget Sound. Among a suite of sensors and sampling equipment, a crucial part of this monitoring includes nitrate data measured by a SUNA V2 nitrate sensor, with twice-monthly observations at several marine stations and concurrent discrete water samples. This enables the direct comparison of in situ nitrate measurements made with the SUNA V2 nitrate sensor to those made with traditional wet chemistry methods and measured in the laboratory, providing a combination of highly accurate and high-resolution data.

In this application, the SUNA V2 was integrated with an SBE 25plus CTD and SBE 55 shipboard profiling carousel. The package collected in-situ sensor measurements in real-time and triggered the acquisition of discrete water samples during the upcast. Laboratory analysis confirmed that the SUNA V2 data delivered in real-time through the profiling package was within +/- 0.18 µM nitrate of the bottle samples.