Stopping aquatic ammonia pollution

Run-off from agriculture increases ammonia levels in the world's oceans. Credit: Curioso_Photography, Pixabay.com

A new device to effectively monitor toxic ammonia that threatens the world's aquatic ecosystems

Ammonia pollution threatens the planets aquatic ecosystems. The ever-increasing levels of agriculture, using ammonia fertilizers in coastal regions, mean that ammonia levels in our oceans are on the rise. Our continued reliance on burning fossil fuels exacerbates the problem.

Ammonia is a molecule that can be highly toxic to sea life, especially fish. In addition, it is an indicator of faecal pollution—from human sewage or animal farms. Its presence in swimming areas is a human health hazard, and contaminated beaches can be a source of infectious microorganisms such as Escherichia coli. To prevent environmental disasters, we need to develop methods for effective monitoring and management of ammonia levels around the world.

Now, a team of researchers from the University of Melbourne, Australia, is working towards this goal. Led by Spas D. Kolev, the team includes Lenka O’Connor Šraj, Inês Almeida, Chelsea Bassett, and Ian McKelvie. These researchers want to help preserve the health of our oceans and protect them from pollutants like ammonia. As part of this quest, they have developed a new device that effectively monitors ammonia levels in seawater. The device can detect low levels of ammonia by accumulating this pollutant continuously over a period of several days. This allows the determination of the average ammonia concentration at the sampling site over this period.

Kolev explains, “The new device provides a reliable and inexpensive way of monitoring ammonia at low concentrations in seawater. It will be a great help in protecting the health of coastal waters across the globe.”

This work, published in Talanta, is the first to report an ammonia passive sampler that can be used in high salinity waters—such as seawater. Seawater is complex and has very high concentrations of dissolved salts and other compounds. This makes it hard to detect molecules such as ammonia, present in small amounts, as their presence can be masked by the high concentrations of other components. However, Kolev and his team have solved this problem by exploiting gas-diffusion. Dissolved gases, like ammonia, can be separated from the other constituents of seawater when they pass through the sampler’s hydrophobic semipermeable membrane. This makes it easier to detect their low concentrations.

Passive ammonia sampling is more effective than grab sampling methods used in traditional aquatic monitoring programs. In grab sampling, a water sample is taken from a point in the aquatic system (e.g., lake, river, sea) at one time. Samples need to be taken frequently and from many points to get a picture of the overall health of the aquatic system. This is expensive, time-consuming and ineffective if pollutant fluctuations occur outside sampling periods. Passive samplers can be deployed for extensive periods of time and at multiple locations. This increases the likelihood of rapid and accurate identification of intermittent sources or sinks of pollutants. They are also cheaper to produce and use.

Kolev concludes, “Field experiments carried out in the State of Victoria's coastal waters, Australia, have demonstrated the samplers potential as a powerful new tool for sea and estuarine water quality monitoring. We hope that this efficient and cost-effective tool will help with large-scale seawater monitoring of ammonia across the globe.”

Article details:

O’Connor Šraj, L. et al.: "Gas-diffusion-based passive sampler for ammonia monitoring in marine waters," Talanta (2017)