Heavy metal pollution in soils and urban-grown organic vegetables in the province of Sevilla, Spain

Sources of heavy metal pollution in vegetables can be varied. The focus of this study was to determine the factors affecting trace metal pollution in soils and vegetables that are grown on community urban and periurban organic farms in Spain. The results showed that soil and dust deposition affected plant composition more than other anthropogenic sources, such as traffic loads. Lettuce and broad bean samples collected from one urban farm showed high concentrations of crustal metals Fe, Ca, Mn and Cr, which was thought be due to Saharan dust deposition. The build-up of soil Cu concentration, due to the use of Cu-based fungicide over a long term, was observed on the farm where vegetables had been grown over a long period of time. On the same farm, concentrations of Pb in the soil and the vegetables were noted to be at levels that could pose a risk to human health and/or the environment and this was concluded to be due to the random and uncontrolled disposal of demolition waste containing lead-based white paints. The increased risks for consumers due to these different sources of pollution acting simultaneously demonstrated the need for careful selection of urban soils intended for agricultural use. Soil organic matter counteracted Pb availability, hence organic management and intensive use of organic amendments were recommended for urban farms.