Geochemical characteristics of bottom sediments of Lake Onega E.I. Valieva, E.N. Poludetkina, O.N. Vidishcheva, A.K. Mirinets and A.E. Rybalko E3S Web Conf., 266 (2021) 07010 Published online: 04 June 2021 DOI: 10.1051/e3sconf/202126607010