Chicago-based researchers used mosses to monitor for heavy metal pollution around the city, and they found that even outlying natural areas were susceptible to pollution.
The team led by scientists at Northeastern Illinois University and the Field Museum of Natural History reported this week in BioRisk that they had used bags of Sphagnum moss with portable X-ray fluorescence spectrometry instruments to measure metal pollution in and near Chicago. They said that the techniques can be used to provide rapid, accurate, and low-cost monitoring for environmental contamination.
“Future research, including broader geographical application and methodological standardization, will strengthen its utility in addressing environmental justice and promoting sustainable urban air quality management,” they said.
They noted that the work complements established moss-based biomonitoring research in Europe.
Cleaned, bright green segments of the moss were distributed in June and July 2024 to locations near a metals recycling facility, an industry and transportation corridor, a suburban rail hub, and an outlying semi-natural area. Meanwhile, controls were maintained at the Field Museum.
The researchers collected samples at one, three, and four weeks, processed them into homogenous powder, and tested them for concentrations of titanium, manganese, iron, nickel, copper, and zinc. The samples that were near the metals recycling facility had elevated levels of all six metals while those collected from the industry and transportation hub had elevated iron and nickel concentrations. Samples from the suburban rail hub, meanwhile, had the highest iron levels.
“Elevated iron levels across multiple sites likely reflect its widespread presence in urban particulate matter, predominantly originating from vehicle exhaust, brake wear, rail transport, and industrial processes,” the authors wrote.
The authors noted that samples from the semi-natural area had elevated nickel concentrations, which they attributed to a highway that was less than one kilometer away. They said that the results suggest atmospheric dispersion of metals throughout the region, which aligns with results that were published by European scientists in 2020.
However, the Chicago-based researchers noted that their study had limited sample sizes and they were collected over a limited time, and they had not evaluated the effects of weather on the results. During the study, they had also attached six bags of the moss to a diesel truck that was used in Chicago and found increases in iron, zinc, copper, titanium, and manganese concentrations during the first three days followed by a decline on day four, when rain had washed away some of the contamination.
The researchers also said that the mosses and materials used in the study may introduce baseline contamination, and the analyzers used in the study provided semi-quantitative results with detection limits that are unsuitable for the detection of low-level contamination.
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