Heavy metal contents in horticultural crops of a representative area of the European Mediterranean region

Heavy metal content (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) was analysed in the edible parts of two types of horticultural crops (leaf and inflorescence crops) from 30 agricultural fields in Castellón (Spain), a representative area of the European Mediterranean region. Selected soil properties relevant to control the mobility and bioavaibility of heavy metals were analysed for the general characterisation of these agricultural soils. The levels of clay, high percentages of organic matter and the presence of carbonate seem to suggest an important retention of heavy metals by these components in most of these soils. However, the high salinity in some fields (N4 dS/m) seems to facilitate the mobility of some heavy metals (e.g. Cu). The mean values of total contents of heavy metals in soils were similar to values obtained in other works on Spanish agricultural soils. However, there were some fields with a metal content (particularly Cu, Pb or Zn) higher than these works, reflecting an important anthropogenic source. In seven fields, the crop contents of Cd and/or Pb were higher than the maximum levels established by the Commission Regulation no. 466/2001 for horticultural crops. Heavy metal contents in leaf crops were higher than in inflorescence crops, except for Zn. The differences for Cd, Cr, Cu, Fe and Mn contents between these two types of crops were statistically significant. The analysis of crop heavy metal contents showed a higher absorption and/or accumulation of heavy metals in leaf crops than in inflorescence crops. Differences in crop characteristics seem to be responsible for the differential accumulation of heavy metals. Furthermore, agronomic practices and other sources of heavy metals (e.g. atmospheric deposition for Cd and Pb) may also have some influence on crop accumulation. Given the relevance of horticultural crops in the Mediterranean diet, it is highly necessary to extend the experience of this work to other areas of the European Mediterranean region.