Phthalates uptake by tomatoes after biosolids application: worst case and operational practice in greenhouse conditions

International audience

English. Application of sewage sludge to agricultural land may be beneficial because it can improve the physical, chemical and biological properties of soils but it may also introduce organic pollutants in soils which could have adverse effects on wildlife and human health if these compounds enter food chain. The present study aims at evaluating the potential transfer of phthalates from biosolids to tomato plants (Lycopersicon esculentum) in a greenhouse experiment. Four phthalates were studied simultaneously: dimethylphthalate, diethylphthalate, dibutylphthalate and di(ethyl)hexylphthalate. Two types of experiments were carried out: aquiculture (hydroponic conditions) and soil culture. Aquiculture experiments involved (1) addition of phthalates as pure substances to the plant growth solution and (2) addition of filtrate from wastewater treatment plant biosolids to the plant growth solution. Soil experiments were carried out testing biosolid from three different origins and treatments (dried biosolids from municipal wastewater treatment plant, biosolids from municipal wastewater treatment plant composted with green wastes and dehydrated biosolids from industrial wastewater treatment plant) with application rate at 30 t.ha(-1). Phthalates were quantified by high resolution gas chromatography coupled with a low resolution mass spectrometer in single ion monitoring mode into roots, sap, leaves and fruits. The results clearly show a difference in behaviour of phthalates according to the part of the plant and kind of experiment. Two transfer pathways were identified: (1) uptake by roots and translocation (2) foliar uptake of vapour from surrounding air. The concentration of phthalates varied from non quantifiable to 174 mg.kg(-1)dry matter in roots, from non quantifiable to 24 mg.kg(-1)dry matter in leaves and from non quantifiable to 6.5 mg.kg(-1)dry matter in fruits. Di(ethyl)hexylphthalate concentration in tomato plant was positively correlated with levels in the biosolids. Compared to the control, application of biosolids resulted in increases concentration of phthalate in plant. However, transfer percentage of di(ethyl)hexylphtalate in fruits were less than 1% even in an experiment designed to maximize transfer.