Contamination of subsurface soil layers with heavy metals around the southern ring road of Kraków

Significant traffic congestion can lead to contamination of the soil and water environment within the range of its impact, i.a. with mercury, lead, cadmium, chromium and zinc. As a consequence of contamination of the subsurface soil layers, migration of metal ions into groundwater is possible, consequently leading to contamination of local aquifers. In 2015-2016 a soil test was conducted at a depth of 0.4-0.6 m below surface level in the vicinity of about a dozen kilometers from the southern ring road of Kraków. The total contents of mercury, lead, cadmium, chromium and zinc were measured in the collected samples (mainly medium and fine sands) and a leaching test was conducted using the classical batch test 1:10. The mercury content in the soil samples ranged between 0.02 and 0.06 mg/kg, cadmium 0.1 to 0.7 mg/kg, chromium 0.3 to as much as 116 mg/kg, lead from 3.7 to 26.6 mg/kg and zinc from 17 to 102 mg/kg. The conducted leaching tests have shown that in all samples the release of metal ions into the solution may be observed. The solubility of the compounds of the analyzed metals ranges from a fraction of a percentage point (0.01% for zinc) up to a few and even, as in the case of mercury, over a dozen percent (approx. 15.7%) of the total metal content accumulated in the soil