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Aim: The extent at which different agricultural strategies may affect the uptake of potentially toxic elements (PTEs) by cropped plants is not completely understood at a field scale. This study dealt with the effect of seasonality, Trichoderma inoculation alone or combined to different applications of commercial grade clinoptilolite (i.e., foliar action, fertigation, and pellet) on the PTEs content of early- and late-ripening cultivars Cucumis Melo L. Methods: Two similar field experiments were performed in spring and summer. For each cultivar/treatment combination, the input of PTEs (namely, Cr, Cu, and Pb) to the soil-crop system through irrigation water, fertilizers, pesticides, and treatment products (i.e., Trichoderma and clinoptilolite products), as well as the PTE content of melon stem, leaves and fruit, were assessed through Inductively Coupled Plasma - Optic Emission Spectrometry. Results: Neither Trichoderma alone nor associated with clinoptilolite had visible effect on PTEs uptake by plants, while early season cultivation was strongly associated with lower uptake of Cu and Pb. The high correlation of Cu and Pb content with Ca content in stem and leaves, used as a proxy for different transpiration rates under different growing seasons, indicated a possible uptake of these metals through Ca-nonselective cation channels as a drought stress defence. Lower Cu and Pb concentration were found in early-ripening melon fruit cultivated in spring. Conclusions: To the scope of Cu and Pb risk management, in case of significant contamination in Mediterranean calcareous soils, the use of early-ripening Cucumis melo L. cultivars in place of late-ripening ones is suggested.

Purpose: Canal dredging and shaping produce considerable amounts of sediments whose reuse on- and off-site depends on their pollution level. This study explores the potential of a calcium chloride washing to remove potentially toxic elements (PTEs) from a freshly dredged calcareous sediment and to affect the aggregate stability of the washed sediment. Materials and methods: The ability of 0.5-M CaCl2 washing to restore the sediment samples polluted with Cu and Zn dredged from a freshwater canal was assessed. The distribution of the two metals among the sediment geochemical phases, the potential availability to plants (DTPA), and the water aggregate stability of particles were evaluated on the washed samples and compared to control. Results and discussion: In the most polluted sample (similar to 200 and 500mgkg(-1) of Cu and Zn, respectively), the washing decreased the amount of Cu by 26%, mainly in the sulfide/organic fraction, and of Zn by 10%, mainly in carbonates. A decrease in the dispersivity of clay fraction was observed due to the well-known effect of Ca2+ ions on flocculation of colloidal clay particles. At large scale, the aggregates formed by the interaction between large particles and flocculated clay showed lower water stability with respect to the control, thus suggesting the need to improve the physical properties of the treated material. Noteworthy, after 1 year of dry storage from washing, the average percentage of potentially bioavailable (DTPA) Cu and Zn (23 and 13% of pseudo-total amount, respectively) dropped with respect to the control (40 and 19%) and a concomitant carbonate increase (+33%) was observed. Conclusions: The CaCl2 washing is a promising method to reduce Cu and, to a minor extent, Zn in wet calcareous sediments dredged from freshwater canals. However, there is still room for improvement. The PTE fractions remaining in carbonates and organic component of washed sediment clearly indicate the potential of combining mild acidic pH values with calcium chloride in the washing to enhance the PTE removal.