2. Sample preparation and analytical methods selection for analyzing contaminant elements in environmental samples

### 2.1. Study area

Somes is a transboundary catchment located in the north‐western Romania. Its main sources of water are the surface waters, reservoirs, and ground waters. The overall water resources in the basin are theoretical about 4.348 billion m3 (of which 4.012 billion m3 coming from surface waters and 336 million m3 of groundwater), but only 21.7% are technically usable. In this region, there are 23 reservoirs with areas over 0.5 km2 such as the Gilau Lake (0.67 km2 ), Tarnita (2.2 km2 ), Somes Cald (0.8 km2 ), and Fantanele‐Belis (8.15 km2 ).

The main objective of this study was to characterize the surrounding areas of raw water accumulations from the catchment, in terms of its content in heavy metals and rare earth, correlated with the supply mechanism of these surface waters. Thus, an assessment of the quality of surface flowing waters, during 2009–2011, was performed. Waters from eight surveillance sections were sampled: the Gilau dam (Area 1); the Somes Cald River (Area 2); the end of Gilau Lake intersection with the Somes Cald River (Area 3); the Somes Cald Lake (Area 4); the confluence of Somes Cald Lake with Somes Rece Lake (Area 5); the Somes Rece Lake (Area 6); Tarnita (Area 7); and the end of Tarnita Lake bottom (exit from hydro plant—Area 8). The measurements were made with a variable frequency. Once with establishing the sampling data, we envisaged the possibility to set any correlations between the values of the monitored parameters and the climatic factors. Samples of sediment, soil, and vegetation corresponding to the surface water sampling points were also taken.
