Novel method to analyze microplastic particle pollution can facilitate environmental impact assessment

Over the past decade, an increasing number of researchers have studied plastic pollution, one of the world’s most pressing environmental hazards. They have made progress but still face challenges, such as the comparability of results, especially for microplastic particles.

There is no standard methodology for sample collection and analysis, for example. Most studies present conclusions based on the number of particles as if they were environmentally identical regardless of size, volume, mass or surface area.

An article was published by three Brazilian researchers i Environmental Science and Pollution Research It aims to contribute to progress in this field by proposing a new perspective on particle morphology.

Using a theoretical approach, the authors argue that morphological characteristics in the analysis can reveal significant differences between samples of microplastic particles, showing that samples initially considered equivalent because they contain the same number of particles have impacts they have different environments due to variations in particle size. and shape.

Microplastic particles (MPs) are artificial polymers with a length between 0.001 and 5.0 millimeters, or 1-5,000 micrometers (μm), and are found in all types of environment. Few studies on pollution from MPs have been published in Brazil, especially in relation to inland aquatic areas.

“Most of the research done on MPs reports the number of particles in terms of the unit taken for the type of sample, from volume in the case of water, to mass when the analysis involves soil and sediment, and individuals for biota. We have been researching MPs in the laboratory for several years, and we have confirmed that size matters and makes a difference. We measure the size of the particles in each sample. particle size and very different levels of plastic pollution based on the mass and volume of the particles,” said Décio Semensatto, first author of the article, to Agência FAPESP. He is a professor at the Institute of Environmental, Chemical and Pharmaceutical Sciences of the Federal University of São Paulo (ICAQF-UNIFESP).

The other authors of the article are Professor Górgia Labuto and Cristiano Rezende Gerolin, a former researcher at UNIFESP.

According to Semensatto, the group is finalizing an article on the Guarapiranga reservoir, a source of drinking water for São Paulo and two nearby towns, Itapecerica da Serra and Embu-Guaçu. “We collected samples in the wet and dry seasons and found more MPs in one season than another, with an even greater difference in terms of the mass of each sample and the total volume of plastic. Using the number of particles as a single parameter focuses on one aspect. and it ignores the fact that different particle sizes have different impacts on ecosystems,” he said.

Comparisons

According to the recent article, the researchers analyzed seven samples with 100 MP each. These will be considered equivalent based on conventional pollution metrics. However, the comparisons made showed that their impact on the environment would be very different. In one example, the MPs were larger in terms of volume, mass and specific surface area. It therefore had more plastic than the others and was likely to produce a greater number of even smaller particles when broken down by physical and chemical degradation.

In another comparison, they analyzed samples with 100 MP and 10 MP respectively, noting that if only the number of particles were considered, the conclusion is that the first had ten times more plastic than the latter, although both had the same total mass and volume of plastic, and the former had greater particle size and specific surface area.

The authors also emphasize the issue of morphology or the shape of the particles. Samples containing fibers, for example, had smaller volume, mass and surface area.

“We also explore the issue of specific surface area, which is very relevant, especially when we are studying BP as carriers of other pollutants, such as metals or pharmaceuticals,” said Semensatto. “The size of the particles has an effect on the surface area available for the adsorption of these pollutants. In addition, MPs also create a plastisphere that acts as a substrate for organisms and spreads these organisms to other environments, with consequences for health world.”

The plastisphere is the community of bacteria, fungi, algae, viruses and other microorganisms that have evolved to live on man-made plastic.

“By considering particle size, mass and specific surface area, we can better understand how MPs pollute water bodies and the behavior of other agents responsible for pollution, including microorganisms,” said Semensatto . “Analysis of all the characteristics of the samples brings new possibilities to light and extends the comparability of the results.”

The scale of the problem

Global plastic production reached 348 million metric tons in 2017, up from 2 million tons in 1950. The global plastic industry is worth $522.6 billion, and is expected to double in capacity by 2040, according to a report by The Pew Charitable Trusts and SystemIQ, in partnership with Oxford and Leeds Universities in the UK.

Plastic production and pollution affect human health and greenhouse gas emissions. More than 800 marine and coastal species can ingest plastic or cause accidents involving it. Around 11 million tonnes of plastic waste enter the oceans every year.

In 2022, 175 countries represented at the UN General Assembly adopted a historic resolution to make a commitment by 2024 to end global plastic pollution. To that end, they established an intergovernmental negotiating committee, which held its first session in December.

“With this study, we set out to contribute to academic efforts to develop routines and methodologies to deal with plastic pollution,” said Semensatto. “Our article encourages discussion within the academic community. The proposal is open for discussion. We are inviting other scientists to measure BASs and report their morphological characteristics, in order to contribute to the discussion of their environmental importance.”

In this context, a group at UNIFESP linked to Semensatto is working with the São Paulo State Environmental Corporation (CETESB) to develop protocols to collect water samples and analyze MPs in the coastal region of the state. The main aim is to find a way to compare results so that MPs can be part of continuous monitoring of the environment, which they are not currently in São Paulo.

This project is being carried out under the auspices of Rede Hydropoll, a network of researchers at different institutions studying water source pollution.