The chromium issue in soils of the leather tannery district in Italy

摘要

Among heavy metals,up to now chromium has received little attention.The reasons for this lack of interest are diverse.One is that Cr was considered a "local source" contaminant,thus constituting a non-widespread environmental problem.A second reason is that the dominant naturally occurring form of chromium,Cr2O3,is considered essentially immobile in the environment,in contrast with the highly mobile and toxic Cr(VI).Based on these assumptions,we have started a research program aimed at assessing the actual chromium accumulation in soils and plants of a tannery industrial district in NE Italy.Further objectives of our study were:to highlight possible contamination of soils,plants and waters;to ascertain the potential risk to human health.Large differences in Cr concentration were observed in the area investigated,with a very scattered distribution.Mean Cr concentration in soils is 210 mg/kg (range 50-10,000).Most of the investigated sites present surface Cr concentrations higher than subsurface,suggesting local sources of Cr to be responsible for soil contamination.Chromium concentrations in selected plants (Taraxacum officinale,Plantago lanceolata) present wide ranges in both the species examined,with little translocation from roots to leaves (barrier effect).To determine the groundwater pollution hazard in the surveyed district,we have compared the soil Cr concentration with the soil vulnerability map.Surface soils having the highest Cr concentration correspond to sites with very high to high vulnerability.Therefore,considering the present soil Cr concentrations and the pollution hazard,precaution and control acts are needed,in order to avoid more damage to land and waters.Moreover,considering all the above items,hazard for human health by direct contact with soil,ingestion,and inhalation should be taken in consideration by decision makers.