Nitrate is one of the most important parameters in assessing surface and ground water quality. Nitrates are naturally present in surface and ground waters in low concentrations, but are harmful to humans and livestock and cause aquatic ecosystem degradation in high concentrations. Nitrates enter the environment as human-induced pollution from a variety of sources, but the largest source is from agricultural fertiliser runoff. Other sources include wastewater treatment discharge, septic systems, and from pet waste. Nitrate is highly soluble in water and therefore readily leaches into water sources, whereas other human- associated pollutants, such as phosphates and ammonia, are not transported as easily. This ability to be quickly transported into ground and natural waters such as drinking water wells, aquifers, reservoirs, lakes, and streams, coupled with its health and environmental implications make nitrate pollution and monitoring of major concern in Australia.

High nitrate levels in fresh and salt water systems accelerate algae growth. As these abnormally large populations of algae die and decompose, dissolved oxygen is consumed and can result in waters with oxygen levels too low to sustain aquatic life, called “dead zones.” These dead zones most often form where rivers transporting high nitrate levels flow into a salt water body, such as an estuary or a bay, where nitrogen is a limiting nutrient. This excess nitrogen then results in accelerated growth of undesirable bacteria and algae. Dead zones are most prevalent in the summer months, when dissolved oxygen levels are already low due to the decreased solubility of oxygen in warmer waters.

Many environmental groups in Australia are interested in quantifying the nitrate concentration over time. For example, it is important to identify areas where high rates of nitrate pollutants enter the river. To confirm the initial observations obtained in field spot tests, ecologists may need to continuously monitor nitrate concentrations upstream and downstream of the suspected site of nitrate pollution. Continuous monitoring allows them to identify patterns present in the nitrate concentration in the river, such as increased concentrations after rainfall events or seasonal changes in nitrate concentrations.