Combating Nitrogen-Driven Coastal Eutrophication: A Selective Ion Array Approach to Rapid In-Situ Measurement of Nitrate and Ammonium

The Investigator will develop tools and methods to detect the presence and the source of ammonium and nitrate ions in water of varying salinity. Such ions signal the presence of nitrogen-laden runoff which is responsible for the destructive eutrophication of bays and salt ponds. Arrays of electrodes capable of detecting these telltale ions will be implemented, and signal processing methods will be calibrated and tested for accuracy on site in natural waters. This capability will support decisions and policies to protect the Massachusetts estuarine ecosystems that serve as nurseries and spawning habitat for anadromous fish.

Objectives: To develop an in-situ system for the analysis of natural waters, focusing on nitrogen and specifically the ammonium and nitrate ion concentrations, which are responsible for most coastal eutrophication; to test the system over a full salinity range and in potentially biofouling environments within Massachusettsestuaries and coastal waters, and to analyze results in terms of capability of such a system to localize and quantify nitrogen sources responsible for eutrophication of coastal ecosystems.

Methodology: The methodology is both theoretical and experimental. The experimental aspects relate to testing of ion selective electrodes (ISEs) for their ability to be adapted to a wide range of salinities and for their protection from degradation by biofouling. Aspects that are both theoretical and experimental relate to the necessary signal processing that will be needed to correct for salinity effects and cross-reactivites of ISEs. To the extent that trade-offs in accuracy among the major ions must be made, the inorganic ions responsible for coastal eutrophication—nitrate ion and ammonium ion—will be favored.

Rationale: Maintaining and restoring water quality is an essential element of maintaining or restoring healthy coastal ecosystems, as well as the health of the watersheds that are i) responsible both for the majority of the nitrogen that causes coastal eutrophication, and ii) are linked to coastal waters through their roles in providing estuarine nursery areas and spawning habitat for anadromous fishes. The capability of rapid, on-site measurement of key water quality quantities will represent a major step in enabling management efforts and policies that appropriately protect the health of these ecosystems.