Avocado to reduce heavy metal contamination

A young researcher has found a way to reduce heavy metal contamination in waterways… using avocados.

Almost 1.3 billion tonnes of avocados are thrown into landfills every year.

This figure incorporates reports from the European Union, Australia, and the United States. Such a volume of avocados generates a tremendous amount of waste before the local impact of increased avocado farming is considered.

However, one person has investigated using avocado skin powder to collect and remove heavy metals from waterways.

That person is Lily Rofail, a Year 10 student at PLC Sydney. Her project, “Hey-sop! Fix-up! and Avo-clean Water System,” won the 2024 Australian Stockholm Junior Water Prize at the Australian Water Association (AWA) Australian Water Awards. Her project investigated using water hyssop and avocado skin powder to remove heavy metals from aquatic environments.

“I know Lily is intelligent and hard-working,” said Dr Paul Burgis, principal of PLC Sydney. “The thing that impresses me the most is that she is imaginative. Her accomplishments take great creativity. Lily thoroughly deserves these accolades. We are all very proud of her.”

This is the second time PLC Sydney has had a student win the prize. In 2022, Julia Cummins won for her study on nanosilver, the tiny particles of silver that have a detrimental impact on our environment when released into waterways. By studying the population and heart rates of the aquatic organism Daphnia magna in varying concentrations of nanosilver, Cummins discovered a level at which nanosilver does not pose a toxicity risk. This level was 0.26–0.50 milligrams per litre (mg/L). Exceeding this value would cause toxicity in Daphnia magna and other aquatic organisms.

What drives Rofail?

Growing up in Sydney, Rofail has always been interested in scientific, environmental, and social issues around water. At 16 years old, this budding young scientist is interested in solving global water problems and how she can make a difference.

“Water and water toxicity are such important issues for the well-being of our world,” she said. “Water is the basis of all life on this planet. Without water, our planet will not survive.”

This drove her interest in water and, more specifically, water quality. As an essential influence on the world’s structure, she said new methods must be considered to improve water quality for everyone.

“There are many places around the world where people do not have access to enough clean water,” Rofail said. “This needs to be improved for the well-being of billions of people worldwide. In addition, waterways have been significantly affected by water pollution, destroying ecosystems, and we need to preserve these important ecosystems. This is particularly true in this decade of sustainability when the environment is changing under the impact of climate change.”

Her inspiration

Rofail spoke openly about the role her science teachers had had on her.

“The science department at PLC Sydney has always encouraged us to take out-of-the-box thinking and find new ways to solve really big issues,” she said. “My amazing teachers, from primary school years to early secondary, as well as this year, Mr John Trimble and Mrs Jo McGrouther, have been truly encouraging.”

Rofail’s commitment to science comes in part from her two different science classes. She is undertaking Cambridge IGCSE Combined Science as an elective while completing the NSW Education Standards Authority (NESA) Science course. The Cambridge IGCSE courses provide an alternative university path while encouraging in-depth scientific research. The richer content provided by studying the NESA and Cambridge programs allows students to delve deeper into their research. PLC Sydney believes that this cross-pollination of science curriculums has allowed Rofail to undertake a ground-breaking research project.

“It’s easy to ask why or how,” said McGrouther, Head of the Science Faculty. “Lily asks, ‘What if?’ She proposes offbeat relationships underpinned by good research and is relentless in devising rigorous methodologies to test her ideas. She is quite extraordinary.”

When it comes to her project, there were multiple reasons for Rofail to concentrate on water hyssop and avocado skin powder as her two primary variables. The project wanted to see if water hyssop and avocado skin powder could reduce the concentration of copper in aquatic environments.

“I chose avocado because it is in large supply worldwide, pretty much all year round,” Rofail said. “There is so much supply that about one point three billion tonnes of avocados are thrown into landfills each year. I wanted to look at what could be done with them that benefits the planet instead of contributing to air pollution, wastage, and greenhouse gases.”

It also helped that her grandfather had a flourishing avocado tree in his backyard. By using these avocados, there were no questions about their provenance. She could show that they are Australian-grown avocados, free from pesticides and with known growing processes.

Water hyssop continues Australian innovation

Water hyssop (officially Bacopa monnieri) is a perennial creeping herb native to many areas around the world, including Australia. Its broad use worldwide has made it native to many communities.

“If we think about large-scale introduction of water plants into an environment, we want to make sure that it will not impact the current ecosystem,” Rofail said. “Using water hyssops can improve the environment’s ability to stay unpolluted.”

Another benefit of water hyssop is that it absorbs copper and mercury. Scientific research has suggested that other heavy metals that water hyssop can absorb include aluminium, arsenic, cadmium, chromium, iron, manganese, nickel, and zinc.

In her research, Rofail found that avocado skin powder is particularly good for environments with low nutrient quality. At the same time, water hyssop is good at extracting heavy metals from environments with high nutrient levels.

“The avocado skin powder acts as a nutrient enhancer, similar to what people would

normally add to water to enhance soil and plant growth,” she said. “There are minimal by-products released by the avocado skin. We particularly need to look at pigments, which will need further study to ensure they do not affect aquatic environments in the long run. As for the water hyssop, it can absorb the copper and be used to grow and produce more leaves and nodes. That makes it self-enhancing and will continue to absorb excess heavy metals with minimal effect on local aquatic organisms and environments, including fish..”

Bioremediation, avocado and native plants

Bioremediation is a low-cost, natural and eco-friendly method that can remove heavy metals from water. Only a few studies have focussed on bioremediation, especially phytoremediation using plants or plant derivatives to remove heavy metals from aquatic environments.

Duckweed (Lemna Disperma) is the ideal plant for studying the effect of phytoremediation as it is fast-growing and can double its size in one to two days. It is a rapidly spreading, small, free-floating plant native to Australia and many parts of the world.

Environmental control and mining regulation agents in Canada, the United States, and the Organisation for Economic Co-operation and Development (OECD) countries use duckweed to monitor heavy metal toxicity. Leaf count and/or dry weight are commonly measured. Thus, Duckweed frond growth or the number of leaves alive can be used to measure the effectiveness of bioremediation strategies to remove heavy metals such as copper from water.

Rofail’s study aimed to determine if avocado skin powder and Bacopa monnieri can improve duckweed survival outcomes in copper-contaminated aquatic environments. The results supported the hypothesis that avocado skin powder and Bacopa monnieri (Water hyssop) significantly improved duckweed survival outcomes in copper-contaminated aquatic environments compared to the base case.

Further, the average copper concentrations, measured by assessing duckweed growth rates and a calorimeter, were reduced with Bacopa monnieri and avocado skin powder. Thus, it was discovered that both avocado skin powder and Bacopa monnieri can be implemented as phytoremediation strategies.

Reaction from the industry and her future

Under the tutelage of her teachers and the science faculty at PLC Sydney, Rofail has developed this project over several years. Having won awards in 2022 for this project, including one for science communication, she has spent time improving and enhancing her scientific research.

“PLC Sydney has been very supportive of my project journey in general, and my science teachers were very happy to see the results of my project. The water industry has been really welcoming, particularly when I attended OzWater in Melbourne. I met so many amazing people who encouraged me to pursue a career in science.”

The Stockholm Junior Water Prize is a prestigious award that recognises innovative solutions to water challenges and showcases the creativity and talent of high school students. Rofail will travel to Sweden later this year to represent Australia at the global level.

Ultimately, Rofail aims to pursue a career where she can make a physical change in the world.

“I think the water industry makes a physical change to our world when it comes to water issues,” she said. “I hope to do more research into water issues and find out how to make lasting physical changes beyond my school project. Science is such a wonderful field of study. I want to do more research and hopefully pursue a career in science.”