Compost application affects metal uptake in plants grown in urban garden soils and potential human health risk

Abstract

PurposeThis study explores the effect of varying organic matter content on the potential human health risk of consuming vegetables
grown in urban garden soils.

Materials and methodsMetal accumulation among edible tissues of green bean (Phaseolus vulgaris L.), lettuce (Lactuca sativa L.), and carrot (Daucus carota L.) was determined for plants grown in five urban garden soils amended with 0%, 9%, or 25% (v/v) compost. Potential risk to human health was assessed by calculating a bioconcentration factor and a hazard quotient.

Results and discussionOverall, the consumption of lettuce and green bean pods grown in some urban gardens posed a potential human health risk due
to unacceptably high concentrations of cadmium or lead. In many cases, compost amendment increased the accumulation of metals
in the vegetables. Even in soils considered uncontaminated by current guidelines, some hazard quotients exceeded the threshold
value of 1. The compost used in this study had a high fulvic acid to humic acid ratio, which may explain increased concentrations
of metals in plants grown in compost-amended soils.

ConclusionsThese results indicate a need to include soil characteristics, specifically organic matter quality, when setting threshold
criteria for metal content of urban garden soils.

KeywordsFulvic acid–Humic acid–Metal contamination–Organic matter–Risk assessment–Urban gardens