Assessment of soil contamination by the content of heavy metals in the soil profile

Abstract

A new soil-ecological definition of the maximal permissible concentration (MPC) of heavy metals in soils is suggested that regulates the sampling in contaminated territories. Instead of the shallow pits usually used for collecting surface samples for soil-hygienic and other investigations, it is proposed to fulfill a detailed analysis along the entire soil profile including not only the determination of the heavy element content in certain horizons but also the soil density in these horizons. For the polyelemental contamination Zc (according to the Saet equation) based on the background (clarke) excess, the established Zc values ranging from 1 to 128, may reach absurd values of 800–900 upon taking into consideration only one surface layer. At the same time, the use of the weighted average content of the metals in the soil profile adjusts the Zc values for the existing natural conditions. Upon aerial impact, the consideration of the heavy metal contents along the soil profile instead of their contents in the surface horizon only leads to a decrease in the indices of the soil contamination degree. Upon the hydrogenic impact, the transition from the heavy metal contents in the surface horizon to their contents in the soil profile gives higher values of the soil contamination.