Excess nitrate in lakes, seas and rivers could increase algae growth, at the risk of toxic blooms or cyanobacteria. An innovative method uses nuclear technology to monitor the origin of nitrate pollution in water.
Searching for the source of pollution
The International Atomic Energy Agency (IAEA), in cooperation with the University of Massachusetts, developed a cutting-edge method to find the origin of nitrogen pollution in lakes, seas and rivers. This tool uses nuclear technology and offers a cheaper, faster, safe technique to determine if the excess of nitrogen components stem from agriculture, sewage systems or industry.
Nitrogen, an essential element that can be found abundantly on Earth, is a fertilizer widely used in agriculture since the mid 20th Century. According to Leonard Wassenaar, head of the IAEA Isotope Hydrology Section, “one of the major global problems in terms of water quality is that we have been overfertilizing our landscapes for decades, either with manure or with synthetic fertilizers. All of these nutrients, particularly nitrogen forms such as nitrates, are seeping into groundwater and eventually into rivers, lakes and streams”.
The danger of nitrates
The excessive nitrate levels increase algae growth, which can lead to toxic algae. They also sink into the bottom of the lakes, feed bacteria and create “dead zones” that kill the fish living at the bottom.
It is very difficult and expensive to eliminate nitrates from water; we need tools to detect the sources of nitrogen, as well as a way to transmit information on water protection and the necessary efforts to fix the problem.
This new method measures the quantity and proportion of stable nitrate isotopes in the water
Nitrate has two stable isotopes or variations of its atoms, with varying weights. Since the weight difference is not the same in human waste or fertilizers, for example, isotopes can be used to identify the source.
The new method uses a type of titanium chloride (a salt) to turn nitrate from a water sample into nitrous oxide gas. From this gas, the isotopes can be analyzed with devices like mass spectrometers or lasers. The current methods use genetically modified bacteria or cadmium, a highly toxic metal, to convert nitrous oxide. These methods are elaborate, expensive and limited to a few specific laboratories. With the new technology, analyzing the sample costs 5 to 10 times less than before, and it only takes a few minutes to prepare it.
The first applications
This method will be applied to study the impact of pollution-controlling measures on the Long Island Sound, on the East Coast of the United States, which was heavily impacted by an excess of nitrate in the past.