Nuclear technology to trace the sources of water pollution

Nitrogen, an essential and abundant element on Earth, is a fertiliser that has been used extensively in agriculture since the mid-20th century and is also one of the major global problems in terms of water quality as land has been over-fertilised for decades, either with manure or synthetic fertilisers. All these nutrients, especially variations of nitrogens such as nitrates, enter groundwater and end up in rivers, lakes, and streams.

Excess nitrate in lakes, seas, and rivers can increase algal growth, with the risk of blooms of toxic blue-green algae or cyanobacteria that sink to the bottom of lakes, feed bacteria, and create ‘dead zones’ that kill bottom-dwelling fish.

Removing nitrates from water is very difficult and expensive, so tools are needed to detect nitrogen sources as well as ways to communicate information about water protection and efforts to remedy the problem.

The International Atomic Energy Agency (IAEA), in collaboration with the University of Massachusetts, has developed a cutting-edge method to find the source of nitrogen pollution in lakes, seas, and rivers. It is a tool that uses nuclear technology and offers a cheaper, faster, and safer way to determine whether excess nitrogen compounds are due to agriculture, sewage systems, or industry.

Nitrate has two stable isotopes, or variations of its atoms, with different weights. As the weight difference is not the same in human waste or fertilisers, for example, isotopes can be used to identify the source.

Current methods use genetically modified bacteria or cadmium, a highly toxic metal, for the conversion of nitrous oxide. These methods are laborious, expensive, and limited to a few specific laboratories. However, the new technology, which uses a type of titanium chloride (a salt) to convert the nitrate in a water sample into nitrous oxide gas, and from this gas the isotopes can be analysed with equipment such as mass spectrometers or lasers, allows the sample to be analysed at 5-10 times less cost than before and takes only a few minutes to prepare.

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