## 3 Occurrence, Distribution and Environmental Impacts of MPs
### MPs in Aquatic Environment  
A total of 60-80% of the marine litter are plastic materials [22]. Population size and the quality of waste management systems largely determine which countries contribute the greatest mass of uncaptured waste available to become plastic marine debris [23]. MP fragments suspended in the water column or deposited in sediments have various negative impacts on the marine ecosystems. Eighty percent of the plastic found in marine waste originates from the mainland [24; 25]. MPs that enter rivers directly, by wastewater effluent or through leachate water from landfill, are eventually transported to the sea [26; 27; 28]. MPs used in cosmetics can enter waterways through domestic or industrial drainage systems. A large proportion of MPs passes through filtration systems of wastewater treatment plants. Seasonal and climatic conditions can exacerbate the transfer of terrestrial debris to the sea and to riverine ecosystems, especially extreme outbursts like floods and hurricanes [27; 28; 29; 30]. Several studies have confirmed that the abundance of MPs in marine environments in Asia is higher during the rainy season than in dry season [31].  
Tourism, recreational activities, commercial fishing, sea vessels and maritime industries (e.g., aquaculture, offshore exploitation, etc.) represent a direct source of MP in the seas and oceans [29; 32]. Marine waste arises mainly from crumbling nets, ropes and abandoned vessels [25]. Discarded or lost fishing gear, including plastic monofilament line and nylon netting, is usually neutrally buoyant and therefore can float at various depths within the ocean [22; 33]. A study conducted by [PERSON] et al. (2018) [27] in the Adriatic Sea showed larger amounts of MPs in the coastal area (\(\leq\)4 km) than further offshore. The main reason is the proximity of land sources of MPs. The presence of some rare polymers and waves  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Environmental** & **Estimated** & **Units** & **Sources** & **Notes** \\
**Compartment** & **Abundance (2024)** & & & & \\ \hline Marine Water & 0.1–10 particles/m\({}^{3}\) & Particles per cubic & [15] & Higher concentrations near coastlines and urban areas; varies with depth and region. & \\  & (surface water) & & & & \\ \hline Rivers and & 10–1000 & Particles per cubic & [16] & & \\ Lakes & particles/m\({}^{3}\) & meter [m\({}^{3}\)] & & & \\ \hline Drinking Water & 110,000–370,000 particles/L & Particles per & [17] & & Most are \textless{1} \(\upmu\)m in size; recent findings (2024) using advanced spectroscopic techniques. \\  & (nanoplastics \textless{1} \(\upmu\)m) & & liter [L] & & \\  & & & & \\ \hline Soil & 63,000–430,000 tons/year input & Tons per year & [18; 19] & From agricultural sources, sludge application, plastic & \\ \hline Atmosphere & & & & & \\ (Urban Air) & 0.01–5 particles/m\({}^{3}\) & Particles per cubic & [20; 21] & Highly variable by location \\ (Urban Air) & & meter (m\({}^{3}\)) & & & \\ \hline Atmospheric & Up to 700 & Particles per m\({}^{2}\) per & & & \\ Deposition & particles/m\({}^{2}\)/day & day & [21] & & \\ \hline \end{tabular}
\end{table}
Table 1: Abundance of microplastics in different environmental compartments [15; 16; 17; 18; 19; 20; 21].  
used in food and dentistry indicated wastewater treatment plants as potential sources of MPs [27]. By monitoring the amount of MPs in sand and sediment samples from four selected beaches in Croatia during and after the tourist season, a higher amount of MPs was determined during the tourist season. Furthermore, the amount of MPs detected at the beach near the river delta was significantly higher than at the other beaches [34]. One of the highest recorded concentration of MPs in sea water so far is reported in the Gulf of Trieste (northern Adriatic) [35]. The main reason for the accumulation of MP waste in the Adriatic Sea is its narrow elongated sub-basin with a high ratio of land to sea surrounded by seven countries and many tourist destinations with strong anthropogenic influence [27, 34, 35].