Transport is one of the most important sources of environmental pollution. More and more information has shown that one of the greatest sources of emissions from transport are emissions related to the release of microplastics from tyres. This is one of the most underestimated sources of emissions into the environment. In this study, environmental samples are analysed for the presence of these particles. For this purpose, optical methods and spectroscopic methods are used. Fourier transform infrared (FTIR) spectroscopy is used to identify synthetic rubber, most likely derived from car tyres. A complementary confocal microscopy method is used to confirm the FTIR results. The soil samples and road dust from the areas with heavy traffic are tested. An average of 372 ± 50 fragments per kilogram dry weight are detected in the soil samples. In the case of samples from the road, this number is 515 ± 20 fragments per kilogram of dry matter. In the samples, most of the microplastics come from tyres, which confirms the scientists’ assumptions about the amount of emissions in the environment. More than 90% of the black fragments later identified as tyre-derived synthetic rubber are found in the samples. A greater number of microplastics are found in road dust samples than in the soil. This may be due to the direct influence of braking, which causes greater accumulation of samples at the emission source than at a short distance into the soil. There is also a noticeable difference in the size of the fraction. In the case of soils, a fraction below 50 µm accounts for the majority of cases. When one analyses road dust samples, one may observe that most of the fractions are between 50 and 200 µm. This may be due to the possibility of smaller emission particles over longer distances and the greater degradation process that occurs in soils. The microplastics from the road dust are less degraded than the microplastics from the soil.

Wastewater treatment processes can fragment microplastics (MPs), which may subsequently enter fertilizers applied in agricultural settings. This study aimed to quantify the occurrence of MPs in stabilized sewage sludge intended for fertilizer production. Matrix elimination was performed using an oxidative method to isolate MPs, followed by MPs separation with a saturated salt solution of appropriate density to enhance the accuracy of identification. The resulting samples were analyzed using spectroscopic and microscopic techniques to provide the detailed characterization of MPs content. The highest concentrations of MPs were recorded during the months of June, July, and May, with average values of 2942, 2341, and 1746 fragments per 100 g of dry weight, respectively. The analysis revealed that fragments were the dominant morphological form, and low-density polyethylene was the most common polymer type detected. These findings underscore a significant risk of MPs re-emission into the environment through the agricultural application of fertilizers derived from sewage sludge. Such practices may lead to the introduction of between 6110 and 13,889 MPs per square meter of soil, depending on the application rates, thereby posing potential risks to soil health and the broader ecosystem. This study highlights the importance of monitoring MPs content in fertilizers derived from wastewater treatment by-products.

Microplastics are an increasingly concerning environmental pollutant. Their presence in agricultural settings is particularly troubling due to their persistence and potential to infiltrate soil, groundwater, and the food chain. This study focused on analyzing fertilizer derived from stabilized sewage sludge collected in June and July. The average mass of microplastics isolated per 100 g of fertilizer was 461.28 mg in June and 458.92 mg in July. The analysis revealed a substantial quantity of microplastics, with fragments and fibers being the predominant forms. In the June samples, an average of 860 microplastic particles was detected, compared to 734 in July (507 fragments and 227 fibers). The most common particle sizes in June ranged from 1500 to 2000 µm and 2000 to 2500 µm, with a significant proportion also exceeding 4000 µm. In July, particles larger than 4000 µm were the most prevalent. Qualitative analysis using Raman microscopy identified polyethylene—a widely used, inexpensive, and chemically stable polymer—as one of the main types of plastic present.

Microplastics found in sewage are mainly microparticles from cosmetics (peelings, toothpaste) and fibres from fabrics (which get into the sewage during washing). Microplastics removed from wastewater accumulate primarily in raw sludge, which it ends up in the sludge processing sector. Due to their low susceptibility to biodegradation, microplastics together with stabilised sewage sludge end up in the soil or are otherwise processed together with the sludge.The purpose of the research was to analyze the content of microplastics in stabilised sewage sludge, of which up to 90% is used to produce fertilizers. The analysis was based first on the oxidation of the matrix with peroxide and then density separation with a saturated solution of zinc chloride (ZnCl2). The second stage consisted of the analysis of separated microplastic fractions. For this purpose, the ATR FTIR and FTIR microscope were used. A complementary apparatus was also used, which was a confocal Raman microscope. Stabilised sewage sludge was analyzed depending on the day of its collection. The highest amount of microplastics was found in the samples from Monday, Friday and Saturday. This was due to the increased release of hygiene products containing plastic microbeads. Qualitative analysis, which showed the highest amount of LDPE microplastic fraction. The highest amount of microplastics per 100 grammes of dry weight was 1,084 fragments and 1,128 fibres, for a total of 2,212 microplastic particles. If 90% of the stabilised sewage sludge was used for the production of fertiliser, the emission would be about 1990 particles per 100 grammes. The study showed that the use of sewage sludge to create fertilisers will contribute to the emission of a significant amount of microplastics into the environment. Acknowledgments: A Research project financed by program “Initiative for Excellence – ResearchUniversity” for the AGH University of Science and Technology. The research was supported byResearch Subsidy AGH 16.16.210.476.