| The pollution of soils by trace elements and heavy metals is a grave environmental problem, mainly due to their toxic and accumulative properties. The levels of lead, cadmium, copper, chromium, nickel, zinc and cobalt, extractable with 0.5 M acetic acid, have been determined in 134 soil samples, collected in the environs of a secondary smelter industry, have been determined to study the environmental effects caused by such industry. The chemometrics techniques applied to the founds results, ANOVA, PCA and Cluster Analysis, allow to conclude than the levels of zinc, lead and copper are greater near the industry, whereas for cadmium and cobalt the contributions is background type. The mobility of these metals has been assessed by using the Tessier's sequential extraction procedure, finding the greater percentages in the more strongly retained fractions.; We have also determined the background and reference levels of arsenic, cadmium, cobalt, chromium, copper, nickel, lead, antimony, tin and zinc in non-polluted soils located in the same geographical zone, as a function of the physiographic units. The pseudo-total contents have been found by using the USEPA 3051 norm in 61 samples corresponding to 31 different sampling points. The background levels have been established from the mean or the median, and also from the use of correlation equations of the metal with the organic matter and clay contents of the soils. From these values, the reference levels have been proposed. |
