Lead (Pb), cobalt (Co) and chromium (Cr)
In the vineyard soils studied, lead (Pb) has average values (Table 3) of 21.9 mg·kg–1 in topsoil and 20.2 mg·kg–1 in subsoil. In some cases moderately high Pb levels (31.6 mg·kg–1) are detected in some soils when compared to the pedogeochemical baseline levels for Castilla-La Mancha (19.3 mg·kg–1, Jiménez Ballesta et al. 2010). This level is probably caused by the mechanized equipment used for works carried out in the vineyard. However, these values are still far below the total mean contents of other regions. For example, the lead content in Castellon, Spain, is 56.1 mg·kg–1 (Peris et al. 2007), in the Champagne region of France Pb ranges from 76 (deep horizon) to 141 mg·kg–1 (topsoil) (Chopin et al. 2008) and, in the case of the soils from Brestnik village, (Bulgaria), values range from 72.6 mg·kg–1 for a depth of 0–10 cm to 61.4 mg·kg–1 (Huzum et al. 2012).
In the present study, the chromium (Cr) content is in the range between 71.0 and 29.9 mg·kg–1 (Table 3), with an average of 51.4 mg·kg–1, in top horizons, whereas in the subsoil the values range between 70.9 and 25.5 mg·kg–1, with an average of 50.0 mg·kg–1. The chromium contents in soils worldwide differ greatly, i.e., in the range from 7 to 2221 mg·kg–1 (McBride 1994), and this depends mostly on the parent material and soil mineralogy. Mîrlean et al. (2007) suggested a variation between 8.2 (young plantation) and 77.9 mg·kg–1. In Portugal the Cr content has an average of 31 mg·kg–1 (from a minimum of 3 to a maximum value of 243 mg·kg–1) (Reis et al. 2007), while the values for some areas in Spain are quite similar, with a total mean content of 32.2 mg·kg–1 (Peris et al. 2007). With some exceptions, the chromium concentrations did not exceed the pedogeochemical baseline value for soils of Castilla-La Mancha (Jiménez Ballesta et al. 2010).
The average cobalt (Co) content is near to 10.5 mg·kg–1 (Table 3) for both topsoil and subsoil, with values slightly higher than for the soils of Castilla-La Mancha (5.8 mg·kg–1, Jiménez Ballesta et al. 2010). Cobalt is an element that is essential to human health but excess amounts can cause detrimental effects (ATSDR 2004). The transfer potential from soil to the edible parts of plants is rather low (Luo et al. 2010).
The total average nickel (Ni) contents (Table 3) in the topsoil and subsoil of Alcubillas are similar (34.7 vs 33.9 mg·kg–1, respectively). In terms of Ni values, a total mean content of 19.9 mg·kg–1 was reported for the Castellon area of Spain (Peris et al. 2007) and a mean value of 28 mg·kg–1 (with a minimum of 2 mg·kg–1 and a maximum of 539 mg·kg–1) was found in the Douro basin, Portugal (Reis et al. 2007). The levels of Ni in Alcubillas are slightly higher than the current Castilla-La Mancha pedogeochemical reference value (16.9 mg·kg–1).