Catching microplastics with cobwebs

Oldenburg researchers study spider webs to track plastic particles in the air. Credit: University of Oldenburg/Daniel Schmidt

Flies, mosquitoes, dust and even microplastics – cobwebs trap everything that travels through the air. University researchers have now tested for the first time whether they can get an overview of plastic particles in the air by examining the capture of the eight-legged creatures.

In inner-city streets with varying traffic, they mainly found plastic PET, presumably from textiles, but also particles from the wear of car tires and polyvinyl chloride (PVC). The amounts of plastic particles found depended on the location. Spider webs, the team concludes, are a simple and inexpensive means of monitoring air pollution from microplastics in the city and identifying particularly polluted areas. The findings are published in the journal Science of the total environment.

“Spiders are found all over the world, including in cities. Their sticky webs are an ideal trap for anything that floats through the air,” explains Dr Barbara Scholz-Böttcher. The microplastics expert from the University’s Institute of Chemistry and Biology of the Marine Environment (ICBM) led the study. Previous studies have shown that pollutants such as heavy metals or magnetic particles get trapped in the webs, she adds. “However, no one has examined cobwebs for microplastics,” says the geochemist, even though the air we breathe is increasingly polluted with microplastics.

Bus stops as a shelter for cobwebs

To find out whether microplastics can be detected in cobwebs and whether there are certain distribution patterns, Environmental Sciences student Rebecca Süßmuth collected cobwebs from the upper part of semi-covered bus stops at various times for her thesis. The bus stops were located along roads of varying traffic intensities in the city of Oldenburg in northwestern Germany. The samples were prepared in the laboratory and the particles adhering to the webs were concentrated on filters.

The team first examined the filters microscopically and found, among other things, fibers that presumably come from textiles and soot particles. They then heated the samples at very high temperatures in the absence of oxygen (pyrolysis) and separated the resulting plastic fragments using a gas chromatograph. A downstream mass spectrometer made it possible to assign and determine the different types of plastic.

The result: “All cobwebs were contaminated with microplastics”, reports Isabel Goßmann, who was involved in the research as part of her dissertation. In some cases, the plastic content even accounted for a good tenth of the total weight of a web. Nearly 90 percent of the plastic consisted of PET (polyethylene terephthalate), PVC and material from car tires. The proportion of tire waste varied greatly depending on the traffic on the adjacent road.

“Our results also indicate that road marking wear is another major source of microplastic loading along roads,” explains Scholz-Böttcher. The researchers also found evidence that the tiny plastic particles accumulate surprisingly quickly in the cobwebs. According to Scholz-Böttcher, the method is a simple alternative to complex measurements to compare the microplastic content in the immediate ambient air. This may be of particular importance in the context of further toxicological research.

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More information:
Isabel Goßmann et al, Plastic in the air?!—Cobwebs as a spatial and temporal mirror for microplastics including tire wear particles in urban air, Science of the total environment (2022). DOI: 10.116/j.scitotenv.2022.155008

Provided by Carl von Ossietzky University of Oldenburg

Quote: Catching Microplastics With Cobwebs (2022, June 2), retrieved August 23, 2022 from

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