Deposition of heavy metals from particulate settleable matter in soils of an industrialised area

Particulate air pollutants from industrial emissions and natural resource exploitation represent an important contribution to soil contamination. These atmospheric particles, usually settleable particulate (which settle by gravity) are deposited on the ground through both dry and wet depositions. The most direct consequences of air pollutants on the ground are acidification and salinization, not to mention the pollution that can cause heavy metals as components of suspended particulate matter. A study of heavy metal concentrations in the settleable particulate matter in two locations has been performed with the aim to assess the influence of air pollution on soil composition. These two locations, (Almazora and Vila-real) are within the ceramic cluster of Castellón (Spain) and they have high industrial density. Settleable particulate samples were collected with a PS Standard British captor (MCV-PS2) for monthly periods between January 2007 and December 2009. Heavy metals (Cd, Pb, Ni, Sb and Bi) have been analysed in the soluble fraction of settleable air particles using ICP-MS. The results related to the heavy metal concentration over the observation period show a high seasonal variability for heavy metal content in settleable particulate and a strong dependence on the rainfall in the study area. The maximum values of heavy metals were obtained in spring or autumn coinciding with the highest rainfall, while the lowest values were generally obtained during periods of low rainfall (summer).The annual variation of the results obtained in both populations shows a decline over the study period in the concentrations of heavy metals analysed. This fact is associated with the steady implementation of corrective measures in the main industrial enterprises in the area based on the treatment of mineral raw materials. Moreover, this decline is, in turn, a lower quantity of heavy metals entering the soil, which results in the presence of soils with low contamination by heavy metals in the sampling area.