## 1 Introduction  
Microplastics (MPs) are particulate plastic debris, varying in shape, with dimensions ranging from 0.1 to 5000 \(\upmu\)m, according to general agreement [1]. These particles significantly contaminate environmental compartments such as the atmosphere, pedosphere, hydrosphere, and biosphere, leading to numerous interactions within and across them. The chemical compositions and shapes of these particles are crucial for their transport and sedimentation processes, as well as their interactions with living and non-living systems. Various types of adsorbed contaminants can be transported over relatively large distances along with MPs, especially substances of organic nature, including persistent organic pollutants, pesticides, and pharmaceuticals such as antibiotics and endocrine disruptors. Some of these substances that are bound to MPs tend to accumulate and manifest their toxicity in living systems at different trophic levels of the food chain. It is currently not possible to precisely estimate the overall environmental impact of these small particles in specific environments and at the global scale [2]. Biodegradable bio-based plastics (referred to as bioplastics in this text) are presented as greener alternatives to oil-derived plastics to address environmental concerns associated with conventional plastics, which are typically non-degradable and persist in the environment. Biodegradable plastics are a class of materials designed to decompose naturally in the environment through the action of living organisms, typically microbes [2]. These plastics are made from renewable raw materials and sometimes include petrochemicals with additives that improve their properties and modify biodegradability [3]. The chemistry behind biodegradable plastics is focused on ensuring that these materials break down under natural conditions, such as in soil or water, without leaving residues. The biodegradation of these plastics generally involves formation of biofilms on the surface, enzymatic scission of polymer chains, and assimilation of produced fragments. The products typically involve water, carbon dioxide (CO\({}_{2}\)), under aerobic conditions, and CO\({}_{2}\) and methane (CH\({}_{4}\)) under anaerobic conditions, and microbial biomass [3]. As bioplastics (also plastics, to a lesser extent) degrade, they release various low molecular weight organic compounds, which some microorganisms can utilize as a source of energy and carbon [4]. Biodegradable plastics currently include a specific group of polymeric substances such as polybutylene adipate terephthalate (PBAT); polybutylene succinate (PBS); polylactic acid (PLA); polyhydroxyalkanoateates (PHA), mostly polyhydroxybutyraterates (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV); and many similar substances. Bioplastics are mainly promoted in biomedical applications [5,6], packaging [7, 8, 9], and cosmetics [10], but they are also gradually coming to be used in agricultural applications, such as coatings of fertilisers [11], carriers of biologically active compounds and biodegradable plastic mulches (BDMs) [12]. It is assumed that they will cause lower plastic infestation and will have lower ecological impacts on soil health [13]. However, in some cases, BDMs have been shown to affect soil organisms and plant growth more than synthetic plastics [12]. As demonstrated under laboratory and greenhouse conditions, the presence of PHB BDMs increased the activity of soil microorganisms, which had a negative impact on plant growth [14] and induced the priming effect [15]. Nevertheless, the overall environmental impacts of these materials on soil health are still not well understood [12]. Depending on the actual conditions (mainly temperature, moisture content, pH, type and abundance of degrading microorganisms), bioplastics may degrade imperfectly, and the biodegradation itself may be slower than anticipated and/or incomplete under actual environmental conditions.