Thallium was determined in 120 samples of soil and 30 samples of stream sediments from the southeastern part of the Silesian-Cracowian zinc−lead ore deposits. Soil samples were taken from topsoils (0.0−0.2 m) and bottom soils (0.8 and 1.0 m). Thallium was determined by flow-injection−differential-pulse anodic stripping voltammetry. The samples were decomposed sequentially with 73% hydrofluoric acid and a mixture of nitric acid and hydrogen peroxide. The results showed that zinc−lead ore mining as well as their processing and smelting leads to a significant increase of thallium in the top layer of soil and in stream sediments. The highest recorded concentration was 150 ppm Tl for stream sediment and 35 ppm for a soil sample. Thallium concentration in small rivers from the investigated area was by 2 orders of magnitude higher than in the reference area. The highest recorded concentration being 3.24 μg L-1.

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A multidisciplinary three-step methodology is being developed to diagnose the extent and type of petroleum pollutants and resulting technological approaches to restore a contaminated site. At first, the site was delimitated and its zones identified by using remote sensors. An area of 307 ha considered of major importance to the national Mexican oil company, Petróleos Mexicanos (PEMEX), was identified. 75% of total analyzed soil samples ranged between 10-50,000 ppm of total petroleum hydrocarbons (TPH) and 25% between 50,000 and 434,000 ppm. Aliphatic and asphaltene groups were predominant and technological alternatives were proposed. In a second phase the identification of native botanical and microbial capabilities to biodegrade pollutants was achieved. Three native botanical species were selected for greenhouse studies: Cyperus laxus showed low sensitivity to TPH resulting in higher seed germination efficiency and growth rate. Since microbial consortia isolated from C. laxus rhizosphere were able todegrade up to 70% of TPH in 30 days laboratory cultures, a phytoremediation-reforest alternative was finally proposed to PEMEX. In a third step, the construction of a pilot plant in situ is now in course wherein both treatability studies and reforest strategies are being developed.

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