USGS Study on Nitrate Sensors: Effect of Suspended Sediment and Color
The U. S. Geological Survey conducted a study of four commercially available ultraviolet spectrophotometric nitrate sensors to determine the effects of suspended sediment concentration (SSC) and colored dissolved organic matter (CDOM) on sensor accuracy. Released this spring, the report reviews the Hach NITRATAX plus sc (5mm path length), Hach NITRATAX plus sc (2mm), S::CAN Spectro::lyser (5mm), and Satlantic SUNA V2 (5mm).
Of the four sensors tested, the Satlantic SUNA V2's accuracy was affected the least in the CDOM test. The Hach 5mm, Hach 2mm, and SUNA V2 met their respective manufacturer accuracy specifications up to concentrations of 4,500 milligrams per liter (mg/L) SSC. The S::CAN failed to meet its accuracy specifications when the SSC concentrations exceeded 4,000 mg/L.
Results of this evaluation indicate that although suspended sediment and CDOM interfere with all of the UV spectrophotometric nitrate sensors, the sensors are more effective compensating for suspended sediment and less effective compensating for CDOM. These results suggest that the end user of these sensors should be aware of the potential skewing of the data due to these interferences, especially if the site is one that has highly colored (chromophoric) water. Read the full report here [PDF].
HydroCycle-PO4 Phosphate Sensor: Wet Chemistry Engineered for Environmental Monitoring
Sea-Bird Coastal's HydroCycle-PO4, with its advanced fluidics, stabilizes rapidly and gives accurate results once deployed without excessive priming. Its autonomous operations, low-power, and five-month reagent stability enable extended deployments in remote locations.
Data Reliability: The HydroCycle-PO4 filter was engineered to improve efficiency and limit clogging during sediment events.
Data Quality: Advanced fluidics, which are resistant to bubbles that plague wet chemical sensors, enable the HydroCycle-PO4 to make measurements at high oxygen saturation and greatly improves sensor uptime in these environments. Now users can expect greater than 90% uptime in bubble-rich conditions!
Data Quality Control: Spend less time analyzing data quality and more time analyzing what the data means. The HydroCycle-PO4 includes real-time quality-control flags that can be output via SDI-12 and RS-232. Additional quality-control analytics and statistics are available through the post-processing features in the software.