Radioactivity and elemental composition of slag from ancient metallurgical production

Abstract

Mines, works, water rock-crushing mills, furnaces for smelting of metals (gold, silver, lead, copper, zinc, mercury, iron), and fields of slag dumps dating from the 1st through the 19th centuries have been found in more than 50 places in the Chatkalo-Kuraminskii mining district (Tashkent Oasis) [1].The goal of the present work is to determine the specific activity of natural radionuclides in the uranium-thorium families and 40 K and to establish the elemental composition in samples of slag taken from dumps in the basins of the Bashkyzylsai River and its tributary, the Kyzylalmasai in the foothills of the Chatkal range, dating to the 5-7th centuries and from tributaries of the Akhangaran-Karabau and Karasarai Rivers in the foothills of the Kuraminskii Range, dating to the 11-12th centuries. The radionuclide composition of the samples was determined by γ-ray spectroscopy and the elemental composition, by neutron activation and x-ray spectral analysis.Two forms of samples were taken by quartering: vitrified slag in the form of solidified streams with smooth surfaces (initially extracted from the bottom of a smelter furnace) and slag with a porous structure formed on a molten metal surface. The color of the slag varied from black to dark gray. The overall number of samples was 27, each with a mass of 2 kg. The samples were first ground up in a agate mortar to a powder with a grain size of ≤10 µm and packaged in polyethylene bags. Samples with a mass of 1.5 kg, ground to a grain size of 5 mm and packed in sealed, one-liter Marinelli vessels, were used for the γ spectroscopy studies. The 50-mg samples for neutron activation analysis were packed in polyethylene bags and samples for x-ray spectroscopic analysis were prepared by drying 500 mg ground samples in vacuum and then adding 50 mg of boric acid. Samples in the form of 10 × 2 mm tablets were prepared by pressing (3 tons/cm 2 ) the carefully blended mixture.The radioactivity of the samples was measured in a Marinelli geometry using a scintillation gamma-ray spectrometer equipped with a 63 × 63 mm NaI(Tl) crystal (10% energy resolution at the E γ = 661 keV 137 Co line) and mounted in a lead box with 10-cm-thick walls. The γ-ray spectrum of each sample was accumulated over a period of 6 h. The instrument

Radiochemistry

“…A review article 249 has considered the ways in which activities such as mining, ore processing and refining can enhance natural radioactivity, either in wastes or the final product whilst more specific reports have considered the radioactivity of ancient slags 250 and of natural and artificial gem stones. 251 The natural radioactivity of oil, 252 coal 253 and lignite 254 and in the neighbourhood of old uranium mines 255 has also received attention.…”