A Portable Absorption Spectrophotometer for Detecting Nitrate in Natural Waters.

Nitrate is found in natural water sources and is known to be harmful to both humans who ingest it, and aquatic ecosystems into which it is transported.  According to the United States Environmental Protection Agency, when infants and children are exposed to high levels of nitrate from drinking sources or otherwise, they experience adverse health effects, most notable of which is oxygen deficiency-induced suffocation, known as “blue baby syndrome” (methemoglobinemia).  When agricultural runoff and leaching reaches streams, nitrate can cause accelerated eutrophication, which harms fish habitats.

Current tools for detecting nitrate concentrations in natural waters are expensive, high-maintenance, or indirect.  Many existing methods require either frequently calibrating an ion-selective electrode, or extracting a water sample from the source and bringing it to the lab for analysis, where procedures include filtering and acidifying the sample before running it through a spectrophotometer.  Several other methods exist for detecting nitrate, such as portable spectrophotometers (Hach, Satlantic), and lysimeters for tracking nitrate leaching (Goss and Ehlers, 2009)

The work done here was an effort to bring a relatively inexpensive, low-maintenance, portable nitrate sensor to the field, eliminating most sample preparation steps.  This device includes a peristaltic pump for sample delivery, allowing for easy integration into existing equipment such as the Decagon Devices Drain Gauge G3, as well as versatility in site locations.