## 2 Materials and Methods
### Study Area  
Klaipeda is an ice-free port city, established in 1252 on the coast of the Curonian Lagoon and the Baltic Sea (55 deg42'40'' N, 21 deg7'50'' E). Now it is the third largest city in Lithuania, covers 98 km2, and the population in 2020 was about 150,000. The western industrial zone stretches along the coast of Curonian Lagoon and includes the state seaport with companies involved in stevedoring (having many shipment storehouses), shipbuilding and ship repair; the eastern one includes the \"free economic zone\" (FEZ) (Figure 1) [21]. The port area covers 540 ha, while FEZ covers 412 ha and has about 100 different companies [22]. Apart from these two large zones, the dense urban structure competes particularly strongly with port and industrial areas. With the growth of the city, some of industrial facilities are already surrounded by residential, commercial, and social zones. An orthophoto map of sampling sites of total suspended particles (TSP) with indicated potential pollution sources is shown in Figure 1.  
Figure 1: Location of TSP sampling sites (their identification number is in the circle) and potential sources of impact in Klaipeda port city. In the port area, the main stevedoring terminals are: A—bulk products loading (fertilizers: KCl, NH\({}_{4}\)NO\({}_{3}\), (NH\({}_{2}\))\({}_{2}\)CO, etc.; grain: wheat, barley, etc.); B—open loading (iron ore, scrap metal, building materials, etc.); C—bulk products loading (cement, apatite, phosphorites, etc.); D—bulk products loading (KCI fertilizers). Other companies and works: E—open warehousing, handling, transportation of granite, dolomite, mineral powder production by rail and trucks; F—waste incineration plant (70-m-high chimney, power plant burns about 255,000 tons per year); _FEZ_—works of free economic zone (manufacture of electrical installation, PET, HDFE, metal structures, cement packaging etc.); _a_—oil terminal; _b_—winter port; _c_—yacht port; _d_—ship repair and shipbuilding; _e_—paper and cardboard factory; _f_—ferry terminal; _g_—railway station; _h_—manufacture of wood products; _i_—heat, energy production (natural gas, biofuel), _j_—production and storage of concrete, building mixtures, etc., _k_—location of former galvanic batteries factory, _Cr_—anomaly of contaminated topsoil [21]. 1–20 Sampling locations. Orthophoto map layer data: google maps.  
In Klaipeda, the average annual temperature is +8.5 \({}^{\circ}\)C and rainfall is 774 mm; the average monthly temperatures range from \(-\)1.4 \({}^{\circ}\)C in January to around 19.0 \({}^{\circ}\)C in July, while the amount of rainfall is from 41 mm in April to 85 mm in August [23]. The wind parameters during the study periods are presented in Table S1. The study area belongs to Lithuanian Maritime Region with a complicated quaternary geological structure closely related to Baltic Sea development [24]. A simplified scheme of the Quaternary geological map of Klaipeda and discussion on elemental background values levels in topsoil is presented in [25]. According to state departments in 2020 [26], the average concentration of PM10 in Klaipeda was 19.5 \(\upmu\)g m\({}^{-3}\), while of PM it was 2.5-7.28 \(\upmu\)g m\({}^{-3}\). However, these values do not address the real state of air quality, especially in the northern part of the city (B locality on the Figure 1).