## 3 Results and Discussions
These types of plastic are representative of the types of plastic products used in people's daily lives [44], e.g., personal care products, shampoo bottles, pipes, etc. Polypropylene (PP) is also very common and is used in food packaging, snack wrappers,  
Figure 6: The size in \(\upmu\)m of the separated MPs, depending on the month. auto parts, etc. [20]. Polyethylene was dominant in the samples analyzed. It is used in personal care products, including body and facial scrubs, food packaging films, and water bottles [34; 36; 45; 46]. The microstructure of the separated microplastics was examined using SEM. The structures differed from each other within the same polymer, i.e., a smooth structure with various defect sizes (Figure 8A) and a honeycomb-shaped structure typical of foam materials (Figure 8B) [47]. The SEM micrographs show numerous microcracks and cracks, which indicate mechanical damage to the surface (Figure 8). Additionally, there are noticeable signs of surface peeling. Due to resistance to biodegradation and the action of physical and chemical factors, MPs accumulate in sewage sludge and, along with it, are introduced into the soil (for example, when used in agriculture) [48]. In the soil environment, other organic micropollutants, such as PAHs, are released into the environmental morphology of the MPs [48]. A review of the literature indicates that wastewater treatment processes may lead to the fragmentation of microplastics (MPs), which then end up in fertilizers used in agriculture, which is confirmed by the results of this study. MPs concentrations in stabilized sewage sludge intended for fertilizer production were significant, especially in the summer months. Microplastics act as both carriers and sources of organic and inorganic pollutants. They can adsorb toxic substances such as polychlorinated biphenyls (PCBs), dioxins, DDT or polycyclic aromatic hydrocarbons (PAHs) and transfer them between various ecosystem components [49]. Additionally, chemical compounds used as additives to plastics, e.g., polybrominated diphenyl ethers, may penetrate the tissues of organisms, disturbing their digestive activity [50]. The results of this work confirm that microplastics present in fertilizers may increase environmental risk, not only by introducing them into the soil, but also by the possibility of them transporting and accumulating harmful chemical compounds. In the context of a growing population and the reduction of agricultural regions in favor of urbanized and  
Figure 7: FTIR spectra of LDPE separated from stabilized sewage sludge. industrial areas, the results emphasize the need to monitor the MPs content in fertilizer products obtained from wastewater treatment. As reported by [PERSON] et al., the application of biosolids to agricultural land as fertilizers can potentially release 1.61 \(\times\) 10\({}^{10}\) and 1.02 \(\times\) 10\({}^{10}\) MPs in anaerobically digested and lime-stabilized sludge, respectively, every month. This illustrates the extent to which MPs can enter the terrestrial environment by this route [16]. Research shows that 0.5 kg of fertilizer is applied per m\({}^{2}\) per year for agricultural soils [14]. With such a large number of MPs found in sewage sludge samples, we can determine the number of MPs that will be emitted per year per 1 m\({}^{2}\) of soil. Taking into account the smallest number of MPs found in the May samples, about 1746 fragments per 100 g of sewage sludge, and the information that 70-95% of sewage sludge is used for fertilizer production, the annual emission per m\({}^{2}\) from fertilizer can reach 6110 to 8295 fractions [51; 52]. Taking into account the largest number of MPs in the June samples, 2924 fractions per 100 g of dry matter, the emission could range from 10,234 to 13,889 fractions. It should also be emphasized that, unlike micropollutants such as pharmaceuticals, they are present much longer, as their decomposition process is very slow, and they break down into smaller fragments, which increases their bioavailability [53].