Additional files [RJEE Vol. 6 (2). 2021 – 4] Fig. 1. Location of sampling points: 1 – settlement Novorybnoye; 2 – 25 km from the mouth; 3 – 45 km from the mouth; 4 – 67 km from the mouth; 5 – settlement Khatanga; 6 – settlement Kresty