Protocol for the use of an Optical Nitrate Nitrogen (NO3N) sensor for measuring ground and surface water NO3N concentrations

Optical nitrate-nitrogen (NO₃-N) sensors are used in environmental monitoring for the real-time detection of dissolved inorganic nitrate and are readily available and increasingly affordable for use by non-experts and may eventually replace the need for expensive laboratory analysis. Many different manufacturers have developed their own instruments for use as permanent <i>in situ</i> sensors in groundwater bores, or as portable <i>ex situ</i> units. The advantage of these NO₃-N sensors is that they can be deployed to complement traditional discrete sampling programmes and significantly improve temporal data resolution and provide high resolution data that captures the rate that NO₃-N may naturally vary in the environment. However, the potential over dependence on technology i.e. a plug and play approach without careful development of quality assurance protocols can easily lead to poor data outcomes. Thus, the effective use of an optical NO₃-N sensor, especially in community-led science, requires specific sensor protocols for its effective use, including:•A regimen of cross checks relative to known standards and/or independently verified laboratory results;•the collection of metadata to contextualise the results; and,•the need for Quality Assurance and Quality Control (QAQC) protocols to provide confidence in the data.