The so far known methods of radiation monitoring of ecosystems based on biological indication by needles of trees and brush of area radioactive contamination include sampling, sample preparation and radiation analysis that consists in using needles as a biological indicator of radioactive contamination during a radiological survey of an area.

The new technology differs from the old techniques in that a reference bank of nucleotide background content in the needles of the basic wood species for all regions is made followed by a field and laboratory phases that include delineation of a sample area, description of live standing trees, sampling for the purpose of determining both background and increased content of nucleotides in the needles of the basic wood species in forest tracts of different types. To achieve this, first a 20 by 20 m sample area is delineated, then each live standing tree within that area is described using a formula where a letter would stand for a tree species, a numeral from 1 to 10 for that species’ significance, and a decimal for foliage closure throughout the sample area at different places.

Trees are characterized by species in terms of their height, age, trunk diameter and height of foliage attachment – all at specific tiers. Then, within the sample area branches from the lower foliage of principal wood species at 1.5 – 1.8 m above the ground are cut off by secateurs; needles taken from them are further differentiated into fractions, e.g. current year needles, second year needles and branches; this done, they are put into paper bags with appropriate tags. Sampling from each tree is carried out according to points of compass, i.e. they are taken from northern, eastern, southern and western sides and sent to the laboratory.

The patent covers three modifications of the new technique. The first one is distinct in that the sample preparation may be carried out in two phases – quick-time and standard: the quick-time preparation takes 10 minutes whereas the standard phase may last up to one hour. The second modification specificity is that during the quick-time preparation needles are thoroughly ground, weighed and put into a 1000 cm² disposable vessel like a milk packet, for example, which is further marked and passed on for radiation measuring of isotope content and for gamma-spectrometry. The specific feature of the third modification is that the standard sample preparation is carried out in such a way that the measured samples are taken out of the vessel, wrapped in paper and placed in the drier for two days at 105^oC until they are absolutely dry. Afterwards, the sample is turned into ash by burning it in a muffle furnace at 400^oC. Then, the ash remainder in amount of 3 g ± 0.25 mg, already cooled down in the exsiccator and weighed, is scattered over a substrate – an aluminum object vane 60 mm in diameter – and sent to the radiometric laboratory. The weighed quantity of the ash in amount from 40 mg to 1 g is poured in a paper bag and sent to the spectral analysis laboratory, all the samples sent have an accompanying note which includes a sample code, its absolute dry mass, weighed quantity mass, and a list of recommended analyses. The sample area, sampling date, sample’s wet and absolutely dry mass, ash mass and weighed quantity mass are entered in the work register.

A.V. Markelov

The Moscow State-run Enterprise – The Joint Environment Technology and Scientific Research Center for Neutralization of Radioactive Waste and Environment Protection (MosNPO RADON)

MosNPO RADON

P.O.Box 58, 115597 Moscow