Radioactivity and geochemical characteristics of cryoconite on the Tien Shan glacier.

The article reports on a study of the cryoconite contamination with anthropogenic and natural radionuclides, as well as ore caused elements, conducted on the Tuyuksu Glacier. The activity concentrations of anthropogenic radionuclides 137Cs, 239+240Pu, 238Pu, and 241Am were determined, with maximum values of about 2000 Bq kg-1, 35 Bq kg-1, 1 Bq kg-1, and 25 Bq kg-1, respectively. An analysis of the radionuclide activity concentration ratios indicates that global fallout is the main and likely the only source of anthropogenic radionuclides. Natural isotopes 235U, 238U, and 232Th, along with their decay products were found to have a lithogenic origin. The study of the elemental composition of cryoconite sediments revealed significant accumulations of Cu, Mo, Sn, Zn, As, Co, Sb, Pb, and Se, which are characteristic of polymetallic and other ore deposits in this region. The Clarke values of concentrations for these elements exceed those of the Upper Continental Crust (UCC) by several times. We believe this reflects the combined influence of numerous large mining, processing, and metallurgical enterprises in Kazakhstan and neighboring countries.