Research of the growth and development of woody plants in radon-active territories of Karelia

. The influence of lithospheric gases on the growth and development of plants is studied. Using a number of areas in Karelia as an example, the weak (300-700 Bq/m 3 ) and strong (6000-8000 Bq/m 3 ) effects of radon on woody plants were analyzed. In areas with high radon activity, an increased frequency of structural anomalies of plant trunks, tumor-like growths, bark necrosis, cancerous diseases of fungal origin, and loss of immunity in plants at a young age are noted. Resistant species in such zones are alder and juniper. In zones of moderate radon activity, carbon dioxide fluxes from the soil surface and at different depths were measured, and the processes of growth and CO 2 gas exchange of Scots pine shoots were studied. It has been shown that a CO 2 flow of deep origin can increase pine growth by 15-20%.


Introduction
Radon-hazardous areas of the territory of Karelia are associated with the presence of uranium ore occurrences.In such areas, the volumetric activity of radon ranges from 200 to 10,000 Bq m -3 , while the background activity in most regions of Karelia is 50-150 Bq m -3 , close to the MPC values.
Botanical studies note a correlation between the volumetric activity of radon and the frequency of occurrence of tree anomalies, including the occurrence of Karelian birch [1].In Belarus, in areas with radon volumetric activity of 2-10 kBq/m3, hundreds of Karelian birch trees per hectare grow [2].A similar situation took place in the 30s of the twentieth century on the Zaonezhsky Peninsula of Karelia, in local areas of which, with high radon activity, the frequency of occurrence of Karelian birch also reached 100 or more trees per hectare [3].Plant mutations arise due to radiation damage to DNA molecules by ions formed by alpha particles emitted by radioactive radon and its decay products.
The purpose of the work is to study the influence of strong and moderate activity of soil radon and carbon dioxide on the growth and development of woody plants.The results obtained on the northern outskirts of the settlement Tolvuya (Medvezhyegorsk district, Zaonezhsky peninsula) and trial areas (cuttings) in the vicinity of the village Konchezero (Kondopozhsky district, 50 km north of Petrozavodsk) are analyzed.

Materials and methods
The volumetric activity of radon was determined by the seismic radon station SRS-05 (Fig. 1a), radon detector indicators SIRAD M 106 N, gamma radiation background -by the scintillation radiometer SRP-68, natural radioactivity of soils and bedrock -by the gamma spectrometer SGS-200.Samples of soil and bedrock were examined for the natural radioactivity of the elements radium 226 Ra, thorium 232 Th, potassium 40 K.
In addition to determining the frequency of occurrence of tree anomalies, the growth performance of trees and CO2 gas exchange of leaves were studied.Gas exchange studies on one-year-old pine shoots were carried out in a closed circuit using a portable gas analyzer LI 6200 (Li-Cor, USA).When measuring CO2 fluxes from the soil, the gas analyzer was reprogrammed to take measurements using an open circuit (Fig. 1b).A gas analyzer chamber with an area of 4.67 dm 2 and a volume of about 5.2 l with holes with a total area of 508 mm 2 was installed: on the vegetation cover and on the soil after removing the litter at depths of 10, 20, 30 cm.The intensity of CO2 (R) emission from the soil was calculated according to the formula: where  is the density of carbon dioxide (under normal conditions = 1.977 g/l), V is the air pumping speed (1.2 l/min), S is the soil area in the chamber, Сchamber and Cair are the concentrations of CO2 in the chamber and ambient air, respectively.According to the recommendations [4], the selected chamber parameters contribute to the rapid stabilization of CO2 concentration in the chamber (2-3 minutes) and make the overestimation of CO2 removal from the soil surface to a minimum.
The study of soil radon and CO2 flows, growth and CO2 gas exchange of pine shoots was carried out in clearings: 1 -2 km from the village Konchezerskaya Chupa (62°10´28.1´´N,33°59´58.8´´E),felling in 2009; 2 -near Lake Gabozero, 2 km west of the village Konchezero (Kondopozhsky district (62.101917°N, 33.969944°E)), logging in 2014.Before logging, fresh blueberry pine forests of 80 years of age grew in these areas (grade 2).The composition of the young growth mainly includes Scots pine (about 70%) with an admixture of birch and aspen [5].Soil type -sandy illuvial-humus ferruginous podzol.

Results and discussion
In the surveyed areas in Konchezerskaya Chupa and Gabozero, the radiation background of 2-9 μR/h was within normal limits.Clarke contents of radioactive isotopes 226 Ra, 232 Th, 40 K were found in the soil and bedrock.
In the southeast of the Zaonezhsky Peninsula (Tolvuya settlement -62°30′39″ N 35°17′14″ E), the volumetric activity of soil radon ranged from 1500 to 8000 Bq/m 3 with large spatial and temporal variations over an area of 0.1 ha.Measurements in the surface layer of soil (30-50 cm) were made using radon detectors SIRAD M 106 N. Experience with the seismic radon station SRS-05 shows that even higher activity should be expected in layers 1 m or more deep.
Research of the species composition of plants in the vicinity of the village Tolvuya showed an almost complete absence of conifers, except for juniper.Birch, willow, and bird cherry were found on the borders of radon hazardous zones.In the zones, trees that had reached 10-15 years of age were observed to die, and trees growing near the zones had growth anomalies (burls, wils, witches' brooms, and others).The main species growing in areas with high soil radon activity (7000 -8000 Bq m -3 ) is alder.On alder trees growing in the epicenter of radon-hazardous zones, fissured tumor-like growths are noticeable on branches and trunks.Already at a young age, trees in these zones lost their immunity, they developed bark necrosis, and characteristic fungal structures formed: conidiomas, fruiting bodies, stromas.There were cancerous diseases, probably of fungal origin, leading to weakening and gradual drying out of the trees (Fig. 2).The skeletons of such trees, preserved for a long time, were indicators of areas with high volumetric activity of soil radon.Measurements of CO2 fluxes from the soil in two studied clearings in the 3rd ten-day period of August 2023 showed that the average values of CO2 fluxes from the vegetation cover of the soil in Konchezerskaya Chupa were more than 3 times higher than those in Gabozero, and with the litter removed -4.5 times (Table 1).
On a clearing in the Konchezerskaya Chupa, a place was found where the CO2 flow from the soil without litter was 9.12 μmol m -2 s -1 , while in the gabozer it did not exceed 1.5 μmol m -2 s -1 .At depths of 20-25 cm, the magnitude of the maximum flows amounted to 5.82 and 0.43 μmol m -2 s -1 , respectively.
Measurements of CO2 gas exchange in the daytime during the period of intensive plant growth in two clearings showed similar average values for last year's shoots -at the level of 6-7 µmol m -2 s -1 .However, in the second half of September, at an air temperature of 20˚C and good soil water content, CO2 gas exchange in the shoots of the current year in Konchezerskaya Chupa and Gabozero amounted to 5.1 and 3.2 µmol m -2 s -1 , respectively.It was noted that the pines in Konchezerskaya Chupa were shedding last year's needles.90% of the trees retained needles from only the current year, while in Gabozero there were needles of 3 years.Note.The chamber was instaled 1 -on vegetation cover, 2 -on soil without vegetation cover, 3on isolated vegetation cover, 4 -on soil without vegetation cover, at a depth of 10-12 cm, 5 -on soil without vegetation cover, at a depth of 20-25 cm.
High levels of radon activity in the village.Tolvuya are associated with the geological structure of the Zaonezhsky Peninsula and ore deposits on its territory.The Onega trough is a bowl-like synclinor structure with an Archean granite-gneiss foundation, filled with Lower Proterozoic volcanic-sedimentary formations.The gentle bedding of rocks is disrupted by fold-fault dislocations of northwestern strike in the form of isoclinal and fanshaped anticlines.Five deposits (Kosmozerskoye, Srednyaya Padma, Vesennye, etc.) and more than 10 ore occurrences (Shulginovskoye, Velikogubskoye, Shungsky navolok, Svetloye, etc.) of uranium-noble-metal-vanadium ores have been discovered on the territory of the peninsula [6,7].The Srednyaya Padma deposit is located 17 km from the village Tolvuya.
Other studied areas in geological terms also belong to the Onega structure, composed of rocks of the Ludykov superhorizon.The volcanic phase is represented by basalts, the near-surface rocks are volcanic breccia from cemented small fragments of lava.The thickness of the formation is estimated from several meters to 400 m [8].
Background levels of gamma radiation recorded in clearings in Konchezerskaya Chupa and Gabozero are not consistent with the volumetric activity of radon, which exceeds the standard for buildings -200 Bq m -3 .This fact, as well as the clarke contents of uranium, thorium, and potassium in volcanic breccia, indicate the supply of radon to the earth's surface from deep horizons.
Externally similar study areas differed in groundwater levels.If in Gabozero this level is determined by a nearby lake and below the water table the thickness of sand to rocks is at least 10 m, then in Konchezerskaya Chupa waterproof rocks lie at a depth of 2-3 m.After the snow melts, a layer of water is formed on them, used by the trees throughout the entire growing season.
The rocky base of the deforestation in Konchezerskaya Chupa, located quite close to the earth's surface, released 6-7 times more CO2 than the sandy soils in Gabozero.Part of the carbon dioxide was absorbed by the litter, the other part was absorbed with water by the roots, and ultimately reached the chloroplasts.This had virtually no effect on the CO2 gas exchange values measured by the gas analyzer.
High growth of pine shoots in areas with intense release of soil CO2 is explained by the fact that the addition of deep CO2 enhances tree growth [9].It is possible that the increased activity of soil radon also contributes by stimulating the growth processes of pine.In the clearing in Konchezerskaya Chupa there are 8-9 dichotomous trees per 500 m 2 , and in Gabozero there are 2-3 such trees.
The mechanism of direct stimulating and inhibitory effects of radiation on growth processes may be the formation of reactive oxygen species caused by radiation exposure, which perform both damaging and signaling, coordinating functions that increase the regulation of plant systems [10].
The correlation between emissions of lithospheric CO2 and radon may be related to the mechanism of their transport to the earth's surface.It is known that heavy radon is transported by bubble formations of light hydrogen and methane [11].In part, this also applies to heavy carbon dioxide.In practical terms, when high radon activity is detected, an increased CO2 flux can be expected, and measuring the volumetric activity of radon in some cases is easier than determining the CO2 concentration.

Conclusion
During the study, information was obtained on the volumetric activity of soil radon in different territories of Karelia.Areas of increased and moderate radon activity were identified, in which the species composition and morphological features of vegetation were analyzed.
In radon hazardous areas of the village Tolvuya was noted the absence of conifers with the exception of juniper, the predominance of alder, the frequent occurrence of tumor-like growths in its trees, bark necrosis, fungal and cancerous diseases, and loss of immunity at a young age.
Measurements of moderate volumetric radon activity in typical clearings in Konchezerskaya Chupa and Gabozero, supplemented by determination of soil CO2 fluxes and measurements of growth processes of young pine trees, showed that the higher soil CO2 flux of cleared areas in Konchezerskaya Chupa corresponds to higher values of volumetric radon activity and better tree growth rates.
Interpretations of the result are related to the groundwater level in clearings, the influence of deep CO2 flow on plants, and a possible stimulating effect of moderate doses of radiation on growth processes of the plants.
A possible correlation between the volumetric activity of radon and soil CO2 may be explained by the same mechanism of their transportation from the interior to the earth's surface and further by bubble formations of hydrogen and methane.

Fig. 1 .
Fig. 1.Measurement of volumetric radon activity with a seismic radon station SRS-05 (a) and soil CO2 flow with a portable gas analyzer LI 6200 with a chamber for air intake (b).

Fig. 2
Cancerous diseases (a) and tumor-like growths on the branches and trunks of alder (b,c).Volumetric activity of soil radon 6500-8000 Bq/m3

Table 1 .
Carbon dioxide flows from the soil in two clearings