Assessment of the influence of the toxic effect of municipal solid waste on the ecological state of the soil

Abstract

Introduction. Тhe municipal solid waste of pollution negatively affects on the state of the environment, since during their storage on the territory of landfills and the adjacent territory, accumulation of heavy metals (HM) can change the biological indicators of soil conditions: microbiological, biochemical, and phytotoxic.
 The aim of the study was to assess the influence of the toxic effect of the municipal waste landfill “Azov” in the Rostov region on the ecological state of the soil. 
 Materials and methods. It was explored the influence of municipal solid waste landfill “Azov” of the Rostov region on the ecological condition of the ordinary chernozem in the landfill and adjacent territory (140, 260, 380, and 540 m). The content of heavy metals in the soil, such as chromium (Cr), strontium (Sr), zinc (Zn), vanadium (V), copper (Cu), nickel (Ni), cobalt (Co), lead (Pb), and arsenic (As) were defined. The ecological state is assessed by sensitive and informative-biological indicators of soil pollution: the abundance of bacteria of the genus Azotobacter, the total prevalence of soil bacteria, the activity of catalase, dehydrogenases. 
 Results. Soils were found to contaminate with arsenic by MAC / TAC (exceeding the MAC by 7 times at the landfill and exceeding the MAC by 4 to 6 times in the territory). Pollution with heavy metals according to German MACs with chromium exceeded by 1.4 times). The highest concentration of heavy metals prevailed in the body of the landfill. Depending on distance from the landfill the concentration of heavy metals in the soil decreased. HM contamination leads to negative consequences for the ecological state of ordinary chernozem: the total number of bacteria decreases (until to 95% of the control), the number of the genus Azotobacter decreases (up to 95% of the control), the activity of catalase (up to 25% of the control) and dehydrogenase decreases (up to 30% of control) and increased soil phytotoxicity (up to 60% of control). It can be concluded that the exploitation of the landfill leads to a deterioration of the environmental situation on the territory of the landfill and beyond.
 Limitations. The ecotoxic effect of HMs on soils less buffered to pollution will be higher than on the chernozems studied in the article.
 Conclusion. The Landfill “Azov” was found to impact on the microbiological, biochemical, and phytotoxic parameters of the soil negatively. This problem connects with influence of heavy metals which get into the soil of during the operation of the landfill. The most sensitive and informative biological indicators are total number of bacteria and length of radish roots.