Data for: particle size analysis and contamination indices

Twenty-one soil samples taken from nine historic abandoned gold mine solid waste dump sites in the Witwatersrand Basin of South Africa were screened from a depth of 30-120 cm. On average, the particle size was 60% sand, 13% silt and 27% clay (Table S1). Metal content (mg/kg) was measured using inductively coupled plasma emission spectroscopy and reported as Pb (774.02) > As-metalloid (52.01) > U (13.89) > Ag (8.73) > Sn (2.09) > Tl (1.94) > Cd (0.20). Hg (331.61) > Au (17.84) were measured in µg/kg. The average values (mg/kg) of soluble inorganic anions were SO42- (3726.17) > NO3- (903.56) > CN- (t) (64.68) > PO43- (10.74) > NO2- (7.22). The average pH was measured at 3.89 and the EC was measured at 222.94 mS/m.

Contamination factor (CF) and pollution load index (PLI) were calculated from elemental data. CF varied between various elements, from just 0.003 in one tailing to 333.500 in the next (Table S2). PLI varied from 0.289 to 2.128 between tailing dumps (Table S2). Uncontaminated sites include CF < 1 and PLI < 0. Soil screening values (SSV) (mg/kg) are Pb (2.20-7070), As (0.20-11), Hg (0.06 –2630), U (1–69), SO42- (951–8355) and CN- ( 0.51–488.25), and exceeded international soil intervention standards. NO3- (5–16,000 mg/kg) exceeded South Africa's protective water resource and informal residential area recommendations. Descriptive statistics are shown in Table S3, with the standard deviation changing significantly from 0.34 to 2149.52.