The influence of alluvial gold mining on the natural complexes of river valleys of Amur River basin in Eastern Transbaikalia

The article presents the temporal characteristics of the climatic seasons of the year - the dates of stable transitions above certain air temperatures (0, 5, 10, 15 °С) in spring and autumn and the duration of periods with the indicated air temperatures on the territory of Eastern Transbaikalia. For the analysis in the work, we used observational data from 27 meteorological stations of ZabUGMS. So, the average daily air temperatures above 0 °C are the boundaries of the warm (frost-free) period. Inside it, one can distinguish the growing season (average daily air temperatures above 5 °C) and the period of active growing season (above 10 °C), as well as “climatic summer” (above 15 °C). In the study area for 1976-2018 the growth rate of the surface air temperature is 0.35 °С/10 years, and in the last 30 years the number of positive values of the deviations of the surface air temperature from the climatic norm has significantly increased. At the same time, at some meteorological stations in some years of the XXI century, average annual air temperatures were noted, which in the long-term series of their values, often reaching 100 years and above, were maximum. On average, in the territory of Eastern Transbaikalia, 183 days a year belong to the frost-free (warm) period, the boundaries of which are the average daily air temperatures above 0 °C. The duration of periods with stable air temperatures above 5, 10 and 15 °С on average throughout the region is 148, 118 and 63 days, respectively. In Eastern Transbaikalia, a stable transition of air temperature in spring from 0 to 15 °С and in autumn from 15 to 0 °С occurs in about 2 months. So, on average across the study area, a stable transition through 0 °С falls on April 12, after 5 °С - on May 2, after 10 °С - on May 20, and after 15 °С - on June 14. In autumn, a stable transition through 15 °C is observed on average on August 17, after 10 ° C on September 8, after 5 °C on September 26 and after 0 °C on October 13. During the study period, on average across the territory of Eastern Transbaikalia, there is a significant increase in the duration of stable periods above certain air temperatures. And if for periods above 0 and 5 °C this increase is 2.1 and 2.7 days/10 years, then for a period with an air temperature above 10 °C it is already 3.1 days/10 years, and for a period with a temperature air above 15 °С -5.7 days/10 years. This is due to a greater extent to earlier onset of stable transitions in the spring, and for a stable period with air temperatures above 15 °C, it's almost commensurate later onset in autumn is also characteristic. A similar picture is observed in some areas of the study area, however, there is no strict regularity in the spatial distribution of the linear trend value. In the context of global warming, the scientific results obtained must be used in the development of new mechanisms for adapting economic sectors to climate change in order to ensure the economic sustainability and environmental security of the region.

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