Geochemical and Isotope Anomalies in Sioma River Gorge, Western Tajikistan

Djamshed A Abdushukurov,Marina V Frontasyeva,Octavian G Duliu,Daler Abdusamadzoda

doi:10.3390/radiation1020013

Abstract

For a better understanding of the previously observed increased natural radioactivity at the confluence of the Varzob and Sioma rivers, Central Tajikistan, the activity concentration of natural radioactive 40K, Th and U daughters as well as of the anthropogenic 137Cs were determined in nine locations covering the entire Sioma River. The radiometric determinations evidenced, in addition to increased activity concentrations of Th and U daughter radionuclides, an anomalous accumulation of anthropic 137Cs and natural 210Pb in the middle of the Sioma gorge. Complementarily, the mass fractions of natural Th and U determined by instrumental neutron activation analysis evidenced an increased presence of Th and U, which, in some places, overpasses six-times the average mass fraction found in the upper continental crust. The possible influence of active air transport from the southern Tadjik plane during the Afghani storms, as well as the presence of actinide-rich minerals, were analyzed and discussed.

Highlights

The Sioma River, a right-bank tributary of the Varzob River, flows into Varzob about50 km north of the city of Dushanbe, the capital of Tajikistan
The final data concerning the experimentally determined activity concentrations as well as instrumental neutron activation analysis (INAA)-determined mass fractions of Th and U are reproduced in Table A3 and illustrated as stacked columns in Figure 2a,b
Gamma ray spectrometry was used to determine the distribution of activity concentration of Th and U daughter radionuclides, i.e., 212 Pb, 212 Bi, and 214 Pb, 214 Bi as well as 210 Pb, respectively, together with 40 K and anthropogenic 137 Cs along the Sioma River, a high mountain tributary of the Varzob River

Summary

Introduction

The Sioma River, a right-bank tributary of the Varzob River, flows into Varzob about. 50 km north of the city of Dushanbe, the capital of Tajikistan. The Sioma River Gorge stretches parallel to the Hissar Range in an east–west orientation. 17 km long and rather narrow, its width not exceeding 500 m. It is framed by mountains with snow and glacial peaks 3500–4600 m high, while the gorge altitude varies between. The basin of the Sioma River, in geological terms, belongs to the South Hissar structural-formational zone of Central Tajikistan (Southern Tien Shan Mountains). Its catchment basin occurred in the multi-phase Hissar batholith, composed of various granitoids of the Middle Carboniferous–Early Permian age and broken in places by Early

Methods

Results

Conclusion