Heavy metal accumulation in vegetables grown in urban gardens

Abstract

Urban agriculture is increasingly popular for social and economical benefits. However, edible crops grown in cities can be contaminated by airborne pollutants, thus leading to serious health risks. Therefore, we need a better understanding of contamination risks of urban cultivation to define safe practices. Here we study heavy metal risk in horticultural crops grown in urban gardens of Bologna, Italy. We investigated the effect of proximity to different pollution sources such as roads and railways, and the effect of the growing system used, that is soil versus soilless cultivation. We compared heavy metal concentration in urban and rural crops. We focused on surface deposition and tissue accumulation of pollutants during 3 years. Results show that in the city, crops near the road were polluted by heavy metals, with up to 160 mg per kilogram of dry weight for lettuce and 210 mg/kg for basil. The highest Cd accumulation of up to 1.2 mg/kg was found in rural tomato. Soilless planting systems enabled a reduction of heavy metal accumulation in plant tissue, of up to −71 % for rosemary leaves.

Rooftop production of leafy vegetables can be profitable and less contaminated than farm-grown vegetables

“…This is likely due to the ability to control the content of the hydroponic solution, which aside from plant nutrients was otherwise municipal grade tap water. This agrees with the report by Antisari et al (2015) that soil-less planting systems can reduce the accumulation of heavy metals, such as up to 71 % in rosemary leaves.…”

“…For instance, a recent study in Italy found that soil-grown vegetables in urban gardens have high heavy metal content, likely due to soil contamination near city roads (Antisari et al 2015). However, Gelman (2014) tested vegetables on five different roofs in Helsinki, Finland, and found insignificant differences in PAHs and trace metals compared to market samples.…”

Socially acceptable urban agriculture businesses

“…Scientific uncertainties regarding the health risks of urban food production remain, and these risks are an important focus of future research. Studies have identified some risks that can be avoided through proper management and control mechanisms (e.g., the establishment of minimum distances to main roads, proper washing practices, and the substitution of contaminated soil) (Antisari et al 2015;Säumel et al 2012). Health risks can also potentially be minimized by establishing a product certification scheme that guarantees low levels of contaminants.…”

“…Others estimate the general potentials and problems associated with urban horticulture (Eigenbrod and Gruda 2014), the urban agriculture effects on the environment (Sanyé-Mengual et al 2013, and the effect of urban agriculture on specific issues, including health issues (Säumel et al 2012;Antisari et al 2015). Particularly for northern Europe, urban agriculture has largely been investigated in relation to its social functions, and it has been proposed that urban agriculture as a "hobby" boosts quality of life, leisure, and community building.…”

Towards Regenerated and Productive Vacant Areas through Urban Horticulture: Lessons from Bologna, Italy

“…As reported by Orsini et al [81], in the city of Bologna about 82 ha of flat rooftops can be found, which could contribute to more than three-quarters of urban food needs. Additionally, their aboveground height is associated with a reduction in environmental pollution related to heavy metals [86]. However, these spaces are often inaccessible to residents either for the high managing costs or more frequently due to the lack of a common and shared management project.…”