Most of the samples have high and variable contents of toxic elements, in particular Pb, Zn and Cu (Table 6). The metal content commonly decreases with decreasing age of waste; proximal and distal soils show nearly the same concentrations, suggesting limited dispersion to occur with distance. Zinc constitutes an exception in this frame. The near neutral pH suggests that the processes of sulphide oxidation and of acid solution buffering balance each other. The acidification and sulphide oxidation observed in the roastings is probably caused by the lack of carbonates and by the large grain size and long residence time. Soils proximal to mine waste and roastings are scarcely deep and present limited development, with simple A-C horizonation. Texture is sandy skeletal, reaction acidic (pH=3.3-3.8); the ratio C/N=14 suggests humification to be effective in surface horizon; bulk density is low (1.2gcm-3). Table 6. Average concentrations of heavy metals, pH and grain size at Fenice Capanne Sample Fe % As Bi Cu Mn Pb Zn pH Texture (age) Roastings 17 927 320 3,450 418 825 2,480 3.5 Gravel, (ca.1890) pebble Tailings 3.6 515 22 853 424 2,050 2,490 4.2 Sand, (ca.1950) silt Tailings1 7.7 230 84 3,400 4,320 1,310 5,470 7.1 Sand, (ca.1960) silt Tailings2 5.1 116 30 508 3,520 214 1,560 7.4 Silt, (1970) clay Proximal 5.8 123 28 595 3,700 353 1,720 6.4 Coarse soil loamy (1999) Distal 6.3 119 27 445 2,900 413 522 6.7 Coarse soil loamy (1999) Adapted from Mascaro et al., 2001a. Distal soils too present limited differentiation, but have silty-clayey texture, neutral pH (6.2 7.8), C/N ratio = 15, bulk density a little higher –
Most of the samples have high and variable contents of toxic elements, in particular Pb, Zn and Cu (Table 6). The metal content commonly decreases with decreasing age of waste; proximal and distal soils show nearly the same concentrations, suggesting limited dispersion to occur with distance. Zinc constitutes an exception in this frame. The near neutral pH suggests that the processes of sulphide oxidation and of acid solution buffering balance each other. The acidification and sulphide oxidation observed in the roastings is probably caused by the lack of carbonates and by the large grain size and long residence time. Soils proximal to mine waste and roastings are scarcely deep and present limited development, with simple A-C horizonation. Texture is sandy skeletal, reaction acidic (pH=3.3-3.8); the ratio C/N=14 suggests humification to be effective in surface horizon; bulk density is low (1.2gcm-3). Table 6. Average concentrations of heavy metals, pH and grain size at Fenice Capanne Sample (age) Fe % As Bi Cu Mn Pb Zn pH Texture Roastings (ca.1890) 17 927 320 3,450 418 825 2,480 3.5 Gravel, pebble Tailings (ca.1950) 3.6 515 22 853 424 2,050 2,490 4.2 Sand, silt Tailings1 (ca.1960) 7.7 230 84 3,400 4,320 1,310 5,470 7.1 Sand, silt Tailings2 (1970) 5.1 116 30 508 3,520 214 1,560 7.4 Silt, clay Proximal soil (1999) 5.8 123 28 595 3,700 353 1,720 6.4 Coarse loamy Distal soil (1999) 6.3 119 27 445 2,900 413 522 6.7 Coarse loamy Adapted from Mascaro et al., 2001a. Distal soils too present limited differentiation, but have silty-clayey texture, neutral pH (6.2 – 7.8), C/N ratio = 15, bulk density a little higher
Abandoned%20mine%20waste-Bini.docx