Assessment of technogenic pollution of the urban environment in Chita by the snow cover state

Abstract

The pollution of the snow cover in the city of Chita (Transbaikalia) with heavy metals (Zn, Cd, Pb, and Cu) is analyzed, and a level of its pollution is compared with similar characteristics in the cities of neighboring regions. The method of inversion voltammetery made possible to find that the content of water-soluble forms of toxic trace elements in the snow is several times greater than in other settlements outside Chita. However, the median values of these values (indicators) are close. Similar results (indicators) were also noted in the ecological and geochemical coefficients, according to which the city of Chita may be attributed to areas with the average level of pollution (Z C = 35.66). Trends in the accumulation of mobile forms of heavy metals in the snow cover of other cities were similar features as it follows from low values of the Saet coefficient (Z C < 32). The charge coefficient calculated for the liquid fraction of the snow cover was found to be high. Therefore, for safe use, melt water should be diluted with clean water 75.24 times for fishery purposes and 9.4 times for economic and drinking use. Rather low content of heavy metals was found in the dust fraction of the snow cover, but in the industrial zone and the zone of residential many-storeyed buildings concentrations of all trace elements exceeded the maximum permissible values (TLV-threshold limit value). At the same time, similar data for other settlements had still greater values, and the exceedings were tens and hundreds times greater the TLV values (the maximum permissible concentrations). The total pollution index (Z C = 72.5) with consideration for the toxicity of chemical elements (Z CT = 98.8) shows that the geochemical conditions in Chita is at the average level. For most other cities, values of the Saet coefficient were smaller 32 that corresponds to low and medium pollution levels. According to the level of dust load Chita is characterized by a high level of pollution (P n ≥ 10 tons/km 2), and it means that more than 8000 tons of dust fall to the snow cover. It has been found that by the total load index (Z p = 493.5) the dust fraction characterizes urbanized territory of Chita as highly polluted, and in this case cadmium (Cu = 255.47) is the main polluter. Comparison of our results with those of other researchers allows making the conclusion that during the period of the Soviet Union disintegration by the beginning of the XXI century pollution of a snow cover notably reduced.