Soilless cultivation in urban gardens for reduced potentially toxic elements (PTEs) contamination risk.

Urban agriculture is increasingly popular for social and economic benefits. However, edible crops grown in cities can be contaminated by airborne pollutants, thus leading to serious health risks. Therefore, a better understanding of contamination risks of urban cultivation is needed in order to define safe practices. The present study addresses the determination of potentially toxic elements (PTEs) risk in horticultural crops grown in urban gardens of Bologna, Italy. Seven experiments were conducted between June 2015 and November 2015, using the following crop species: tomato (Lycopersicon esculentum), sweet basil (Ocimum basilicum), onion (Allium cepa), lettuce (Lactuca sativa), black cabbage (Brassica oleracea), fennel (Foeniculum vulgare) and radish (Raphanus sativus). Plants were grown either on soil or on a soilless system filled with peat. Among studied species, radish grown on soil presented the highest accumulation levels for all PTEs under study. The adoption of soilless system reduced PTEs accumulation in most considered species. Accordingly, daily PTE intake presented a decrease of 80% for chromium, 38% for copper, 100% for cobalt, 53% for lithium, 27% for molybdenum, 78% for nickel, 55% for lead and 98% for vanadium in soilless grown vegetables.