Soil degradation caused by post-mining and post-metallurgical waste - detection using gas chromatography–mass spectrometry (GC-MS) and electrical resistivity tomography (ERT)

Land reclamation is a significant environmental and economic issue. Nowadays, there is a need to restore industrial areas to a state as close to nature as possible. Therefore, it is essential to monitor the condition of soils in a quick and non-invasive way. In southern Poland, the mining industry led to the creation of diverse waste dumps like post-mining waste, tailings from flotation, or Zn-Pb wash waste dumps. The research area covers the industrial waste dumps in Olkusz, Bytom and Piekary Śląskie. For the study, soil samples were taken from 1 m soil pits to determine the migration of pollutants into the soil profile. Additionally, waste dumps contacting the soils were sampled (from 0.5 m deep pits). The total organic carbon and sulphur were determined using Eltra Elemental Analyser CS530, while the composition of the total extracts was analyzed using Agilent gas chromatograph 7890A, with a DB-5 column coupled with a mass spectrometer 5975 C XL MDS. The total concentration of trace elements was determined using atomic absorption spectrometry in an acetylene-air flame (Analyst 400, Perkin Elmer). The ERT measurements were performed using LUND electrical imaging system with SAS 4000 Terrameter produced by ABEM Malå (Guideline Geo).

The samples contain av. 3.7 wt. % TOC and 0.4 wt. % TS. In GC-MS chromatograms, the Bytom and Piekary Śląskie samples show a higher PAHs abundance than the Olkusz samples. In soil profiles near waste dumps, a higher abundance of PAHs was found not only in the surface layer but also in samples to 0.75 m depth. In soil profiles away from the landfill, a higher abundance of PAHs was found only to 0.5 m depth. The PAHs abundance was decreased below 0.5 m depth, and even some of the PAHs weren't found. The high PAHs abundance even at a depth of up to 1m was observed in soil profiles under a waste layer. In samples, the concentrations of trace elements are higher than the limit values (Cd 1.1 to 135.7, Pb 17 to 12407 and Zn 19 to 28903 mg/kg). Soil contamination and its spatial diversity with trace elements in the mining area can be successfully located and studied using ERT measurements. The impact of soil pollution was observed on the geoelectric cross-sections in the form of reduced electrical resistivity associated with an elevated trace element content compared to the unpolluted area. The differentiation of the electrical resistivity was related in particular to the sites of surface runoff from the waste dump. The sediment washed out from the waste dump changed the physical characteristics of the soil and lowered the electrical resistivity of the native geology. The results suggest that the trace elements and toxic organic compounds in wastes are mobilised by surface runoff and the infiltration of rainwater into the ground.

Acknowledgements

The financial support of the National Science Centre, grant No 2017/27/B/ST10/00680 is gratefully acknowledged.

Presentation preference: poster on-site in Vienna