Bulimba Creek tops Brisbane waterways for hazardous microplastics, risk analysis finds

A QUT investigation of the composition of microplastic types in three Brisbane creeks found that Bulimba Creek had a high load of hazardous microplastics. The work is published in the journal Marine Pollution Bulletin.

First author Ph.D. candidate Heshani Mudalige, from QUT’s School of Chemistry and Physics, said the team developed an integrated microplastic risk-zoning framework to assess the ecological risk of microplastics (MP) based on analyses of sediment from Kedron Brook and Bulimba and Enoggera creeks.

“Our new risk assessment framework captures the complete risk profile of MPs in aquatic sediments by integrating their abundance (potential load index—PLI), their polymer composition hazard level (PHI) and the risk they pose to the ecology of the creek (PERI),” Mudalige said.

The three plastic polymer types with the highest hazard scores—PVC, PMMA and polyester—were found in sediment at various points on the three creeks and are major contributors to ecological risk.

Mudalige said the biggest ecological threat was not just the number of microplastics but the presence of more hazardous polymer types.

“We identified that PHI and PERI values indicated a strong influence of hazardous polymer composition on toxicity-weighted ecological risk compared to PLI,” she said.

“We found sites with relatively small amounts of microplastics but with a very high ecological risk due to the presence of highly hazardous polymers.

“While Bulimba Creek showed the highest scores for both hazardous MPs and ecological risk, Kedron Brook had the highest PLI.

“When aquatic organisms at the bottom of the food chain consume PVC particles, the toxic chemicals in them affect the growth, reproduction and survival of fish as the MPs move through the food chain.

“Similarly, PMMA may cause physical stress, reduced feeding efficiency and energy loss in organisms that consume it.

“PVC is on the high hazard list for its ease of being ingested in fiber form and may cause blockages, reduced feeding and physiological stress, while transporting other pollutants attached to the MP surface.”

Mudalige said MPs were detrimental to human health because they could absorb pollutants from the surrounding environment and release chemicals already contained within the plastic.

“MP particles and their associated contaminants are toxic and enter the human body primarily through consuming seafood.

“MPs are linked to potential harm to human circulatory and immune systems and neurodegenerative disorders.”

The researchers took sediment samples from six sampling sites on each of the three urban creeks to reflect the mix of different land uses each creek flowed through.

“We sampled the six sites on each creek four times over a year and then analyzed them to develop our ecological risk-assessment zoning framework for aquatic sediments.

“The results show that land use, whether industrial, commercial or residential, plays an important role in MP risk distribution.

“By integrating the three main risk indices, our framework enables consistent identification of hotspots to help environmental managers focus cleanup and protection efforts where they are needed most.”

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Sadie Harley

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Andrew Zinin

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