Meanwhile, nitrate is used as a powerful terminal electron acceptor by denitrifying bacteria to deliver the energy they need to thrive.

Under anaerobic conditions, nitrate is the strongest electron acceptor used by prokaryote microorganisms (bacteria and archaea) to respirate.

In natural waters, inevitably contaminated by microorganisms, nitrate is a quite unstable and labile dissolved chemical species because it is metabolised by denitrifying bacteria.

The reactive oxygen species (ROS) generated by NO contribute to the oxidative stress, a condition involved in vascular dysfunction and atherogenesis.

The sample is introduced in a flow injection analyzer, and the resulting nitrite-containing effluent is then combined with a reagent for colorimetric or electrochemical detection.

The most popular of these assays is the Griess test, whereby nitrite is converted to a deeply colored azo dye suited for UV-vis spectroscopic analysis.

[1] The significance of nitrate extends beyond its role as a nutrient since it acts as a signaling molecule in plants, regulating processes such as root growth, flowering, and leaf development.

[7] While nitrate is beneficial for agriculture since it enhances soil fertility and crop yields, its excessive use can lead to nutrient runoff, water pollution, and the proliferation of aquatic dead zones.

Nitrate's importance in ecosystems is evident since it supports the growth and development of plants, contributing to biodiversity and ecological balance.

In fact, nitrates (NO−3), often present at too high concentration in drinkwater, are only the precursor chemical species of nitrites (NO−2), the real culprits of methemoglobinemia.

Infants younger than 4 months are at greater risk given that they drink more water per body weight, they have a lower NADH-cytochrome b5 reductase activity, and they have a higher level of fetal hemoglobin which converts more easily to methemoglobin.

[18] An acceptable daily intake (ADI) for nitrate ions was established in the range of 0–3.7 mg (kg body weight)−1 day−1 by the Joint FAO/WHO Expert Committee on Food Additives (JEFCA).

As a consequence, as nitrate forms a component of total dissolved solids, they are widely used as an indicator of water quality.

Nitrate deposition into ecosystems has markedly increased due to anthropogenic activities, notably from the widespread application of nitrogen-rich fertilizers in agriculture and the emissions from fossil fuel combustion.

[23] Annually, about 195 million metric tons of synthetic nitrogen fertilizers are used worldwide, with nitrates constituting a significant portion of this amount.

[24] The impact of increased nitrate deposition extends beyond plant communities to affect soil microbial populations.

[25] The change in soil chemistry and nutrient dynamics can disrupt the natural processes of nitrogen fixation, nitrification, and denitrification, leading to altered microbial community structures and functions.

[26] A source of nitrate in the human diets arises from the consumption of leafy green foods, such as spinach and arugula.

Nitric oxide is a physiological signaling molecule which intervenes in, among other things, regulation of muscle blood flow and mitochondrial respiration.

[27] Symptoms of nitrate poisoning in domestic animals include increased heart rate and respiration; in advanced cases blood and tissue may turn a blue or brown color.