## 4 Discussion
### Inter-Elemental Relationship and Related Groups
It is known that association Sr-P-Ca is characteristic of apatite-group minerals [99] and phosphorus fertilizers produced from them. High content of Sr can be found in superphosphate, although it depends on raw material: igneous rock phosphates contain more Sr than sedimentary [100]. This difference is also confirmed by our data (Table S2). Having in mind that the chemical industry company \"Lifosa\" operates in Kedainiaiai (Lithuania) is one of the greatest phosphorus fertilizer manufacturers in Europe [101], the production and raw materials of which are stevedored in Klaipeda, successful fixation of its emissions with the help of factor and cluster analysis is quite accurate. Side-by-side to Sr-P linked up in L3 cluster, there the is ((Cu-Zn)-Ni)-V group which constitutes L2 cluster. Further, amalgamation of both clusters takes place in earlier stage than with other clusters in the left branch of the dendrogram. Factor F4\({}_{\text{TSP}}\) corresponds to L2 cluster. In comparison with \(\mathbf{Bn}\), the increased contents of Cu, Zn, Ni, and V are found in the dust of stevedored phosphorites. However, Zn and Cu are distinct indicators of various anthropogenic activity, first of all, urban traffic. Brake wear and exhaust emissions (fuel, lubricating oil, and motor wear) have been shown as responsible for emissions of Cu, Zn, and Pb [102]. Cluster of Zn and Cu with Pb and oil products in the topsoil of the central urban districts of Vilnius also confirms this [48]. Presumably, shipbuilding and ship repair [103] is also one of Zn and Cu sources. Both elements are tracers of waste incineration plants, too [104], and geochemical composition of ash from Klaipeda waste incineration plant does not deny this finding (Table S2). Another two indicators of anthropogenic activity, i.e., Ni and V, are close to pair Zn and Cu. Heavy oil used in boilers [15; 94], as well as used in marine engines [18; 105; 106] has high contents of these elements. These facts enable to presume that part of V and Ni can be transferred to ambient air due to shipping activity. Besides, one should have in mind that the impact of \"Mazekiiai Refinery\" [107] which is one of the greatest oil refineries in the region and is located only at 110 km northwest from Klaipeda is also possible. In the next stage, cluster L1 composed of anionic elements Br, S, and Cl link up with joint cluster L3 + L2. The same three elements have significant loadings on respective factor F3\({}_{\text{TSP}}\). There is usually little doubt that Cl originates from sea salts [82; 84; 108], meanwhile statements about marine origin of Br [109] and S [110] are rather rare. The latter circumstance can be predetermined by lack of Br measurement data (Figure 6). For example, in the Belgium study [82], Br content was not presented, although the equipment used allowed its reliable determination. Chlorine, S, and Br are sensitive to meteorological conditions (Table S6). This affinity can determine the possibility that some their proportion appears in Klaipeda by long-range atmospheric transfer, dominant from western directions of Europe [12]. The data of S and Br in Table S3 does not deny this. The concentration of S in PM10 of Belgium (value of for \"all stations\" given [PERSON] et al. in [82] is 2080 ng m\({}^{-3}\), after recalculation to mass concentration in dust it is -70,034 ug g\({}^{-1}\)) more than 13 times exceeds the median value in TSP of Klaipeda. The explanation of such a difference solely by the capability of finer particles to accumulate pollutants is insufficient, because e.g., [PERSON] et al. [67] have not found significant differences in the contents of S in PM2.5 and TSP. The TSP of Klaipeda has more than 20 times less Br than PM2.5 of Krakow, in which the variations of concentrations of Br and Cl (S data was not included in study data set), also K, Pb, Cu, and Zn are explained by their origin from combustion of coal and/or biomass [83].