Assessing the natural and anthropogenic radionuclide activities of the Pechora River estuary: Bottom sediments and water (Arctic Ocean Basin)

Abstract

This paper studies the activity of natural and technogenic radionuclides in bottom sediments and surface water of the Pechora River estuary, which is the largest Arctic river within the European part of Russia. The relevance of conducting radioecological studies of this region is associated with active oil and gas activities in the Pechora basin and the presence of potential sources of radiation hazard. The average activities of ¹³⁷Cs, ²²⁶Ra, ²³²Th, and ⁴⁰K in bottom sediments were 0.16, 18.72, 13.36, and 373.59 Bq·kg^-1, respectively. The average activity of ²²⁶Ra in the bottom sediments of the Pechora delta was two times higher than in other rivers of the Arctic basin of the European part of Russia, which is associated with oil and gas activities that are carried out in the Pechora basin. This is due to the fact that the decay products of uranium are the main by-products of oil and gas production. The specific activity of technogenic ¹³⁷Cs in bottom sediments of the Pechora River delta was low and did not exceed 2.2 Bq·kg-1. We did not detect any radioactive ⁹⁰Sr in bottom sediments. The low ¹³⁷Cs activity in the bottom sediments of the Pechora delta was associated with both the larger granulometric composition of the sediments in comparison with the estuaries of the Siberian rivers, and with low concentrations of ¹³⁷Cs in the terrigenous material (soil) entering the river from the catchment area. This was due to the low levels of ¹³⁷Cs contamination in the soil of the Pechora river basin. We did not find any negative radiation effects of the underground nuclear explosion "Pyrite" carried out in the northern part of the delta, since there were no other technogenic radionuclides. The values of the radionuclides ³H, ¹³⁷Cs, ²²⁶Ra, ²³²Th and ⁴⁰K, as well as the total alpha activity in the surface waters of the Pechora River delta, turned out to be below the detection limit. In surface waters, we were able to determine only the total beta activity, which varied over a range from 19.6 to 59.6 Bq·m^-3 with an average value of 33.9 Bq·m^-3, which was significantly lower than the radiation safety standards. The values of the radiation hazard parameters were below the world average levels and were not significantly hazardous to the health of people living in the area of the Pechora River delta. We concluded that at present, in the Pechora River delta, there are pastures for reindeer with low levels of natural and man-made radioactivity. These conducted studies are the source material in a series of comprehensive studies of the current radioecological state of the tundra territories of the European part of Russia.

Keywords: Arctic Ocean Basin; Hazard parameters; Pechora River estuary; Radionuclides; Sediments; Water.