Background monitoring of atmospheric mercury in the Baikal region

Two-year study (2013-2015) of the gaseous elementary mercury (thereafter, mercury) was carried out at locations of two weather monitoring stations (near settlements Listvyanka and Tankhoj) in the Southern and Western Pribaikalye in a vicinity of the Lake Baikal.

During the first period, the mercury analyzer Lumex RA-915AM was installed on the territory of the meteorological station “Istok Angary” (WMO-30814; 51°52`16“ N, 104°49`42“ E; 467 m asl) at a distance of about 20 m from a shore of the lake. This station is located in the south-western part of the lake and in a close proximity to the Listvyanka urban settlement. It should be noted that since 2011, long-term monitoring of mercuryhas been carried out in this area on the research base of the Limnological Institute (Siberian Branch, Russian Academy of Sciences) under the Global Mercury Observation System programme, and in particular, at location of the Solar vacuum telescope. This made it possible to compare and evaluate the variability of measurements obtained near the Lake Baikal in terms of effects of the vertical distribution of atmospheric flows for two spatially distant measurement points.

For this period, it was recorded a substantial increase in concentration of mercury during 11-16 hour intervals on a daily cycle (with max – 4.78, min – 0.16 ng m-3). Such diurnal variability is characteristic only for a short period of time (in months of July – August 2013), but it is precisely during this time period that the most intense anthropogenic mercury emissions occurred in the coastal zone of Lake Baikal. This makes it possible to assess the influx of various forms of mercury into the ecosystems of the Baikal region under the influence of climatic and meteorological factors.

A comparative analysis of the concentration values of mercurywas performed out for two measurement points (August 2013), point №1 at the lake level (“Istok Angary”) and point №2 at a height of ~ 680 m asl (Solar vacuum telescope) with a distance between these points of about 5.2 km. Mercury from the atmosphere is deposited on the underlying surface, and the highest intensity total solar radiation and re-emission of mercury occurs with increased concentrations – 4.78 ng m-3 at point №1. Similar dynamics of mercury at point №2 was not recorded.

The second period of observations (from 27 July 2014 untill 11 January 2015) took place on the meteorological station “Tankhoy” (WMO-30824; 51o34’N, 105o07’E; 472 m asl). This site is located in the southeastern part of the Baikal Lake at a distance of about 376 m from the lake shore. The distance between two measurement sites is about 37.3 km.

Statistical analysis showed that the summer season is characterized by a high variability mercurybehavior; so, the average concentration was 1.19 ± 0.27 ng m-3 (with max – 2.86, min – 0.27 ng m-3). An assessment of the monthly averages showed that in July, on average, the mercuryconcentration was 1.18 ng m-3 (in August – 1.22 ng m-3), and these are the lowest concentrations observed in the Northern Hemisphere. The increase of concentration in the time period from 17 untill 21 was recorded for the meteorological station “Tankhoy” (with max – 2.86, min – 0.31 ng m-3). This is probably due to the intense burning of coal for heating houses. The average value for the entire period was 1.18 ± 0.27 ng m-3.

It can be seen that average concentration mercury for two monitoring points does not exceed the lower limit of the average concentration (1.5 – 1.7 ng m-3) in the Northern Hemisphere. Thus, the natural reserve territory of the Lake Baikal can serve as the main region with the background level of especially clean areas for monitoring heavy metals.

Text by Dr. Fidel Pankratov, Institute of the Industrial Ecology Problems of the North (INEP), KSC, Russian Academy of Sciences

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