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Soil degradation under excessive salinity and pollution by potentially toxic metals are increasing rapidly in agricultural areas, representing a serious threat to food production and human food security. A factorial combination of four salt concentrations (0, 20, 40 and 60 mM NaCl) and three cadmium (Cd) levels (0.3, 2.5 and 5 mg kg-1) in peat soil on mineral uptake/distribution in radish plants (Raphanus sativus L. var. sativus) was studied under the greenhouse conditions. After 34 days of exposure to increasing NaCl concentrations, plants proportionally increased Na and Cl accumulation in leaf and hypocotyl tissues. Salinity significantly increased accumulation of Cd (up to 20%), Cu (up to 11%) and Zn (up to 7%) in leaves. In contrast, raising salinity levels did not affect Cd and Cu translocation from leaves and deposition into the edible hypocotyls, which may indicate that the phloem mobility of those elements in radish plants is relatively poor and unaffected by NaCl exposure. Increasing salinity improved Zn accumulation in the hypocotyl tissue up to 27%. Soil contamination by Cd resulted in 10-fold increases of Cd content in leaf and hypocotyl tissues, and significant decreases of Zn and Cu content in leaves. Cu and Zn deposition in radish hypocotyls was unaffected under saline conditions. Leaf accumulation of all observed metals (Na, Cd, Zn and Cu) exceeded their accumulation in edible tissues, suggesting that the apoplast and the vacuoles of leaf cells may be the sites of preferential deposition of these metals.

Human-induced salinization and trace element contamination are widespread and increasing rapidly, but their interactions and environmental consequences are poorly understood. Phytoaccumulation, as the crucial entry pathway for biotoxic Cd into the human foodstuffs, correlates positively with rhizosphere salinity. Hypothesising that organic matter decreases the bioavailable Cd2+ pool and therefore restricts its phytoextraction, we assessed the effects of four salinity levels (0, 20, 40 and 60 mM NaCl) and three Cd levels (0.3, 5.5 and 10.4 mg kg− 1) in peat soil on mineral accumulation/distribution as well as vegetative growth and fruit yield parameters of muskmelon (Cucumis melo L.) in a greenhouse. Salt stress reduced shoot biomass and fruit production, accompanied by increased Na and Cl and decreased K concentration in above-ground tissues. A 25- and 50-day exposure to salinity increased Cd accumulation in leaves up to 87% and 46%, respectively. Accumulation of Cd in the fruits was up to 43 times lower than in leaves and remained unaltered by salinity. Soil contamination by Cd enhanced its accumulation in muskmelon tissues by an order of magnitude compared with non-contaminated control. In the drainage solution, concentrations of Na and Cl slightly exceeded those in the irrigation solution, whereas Cd concentration in drainage solution was lower by 2–3 orders of magnitude than the total amount added. Chemical speciation and distribution modelling (NICA-Donnan) using Visual MINTEQ showed predominance of dissolved organic ligands in Cd chemisorption and complexation in all treatments; however, an increase in salt addition caused a decrease in organic Cd complexes from 99 to 71%, with free Cd2+ increasing up to 6% and Cd-chlorocomplexes up to 23%. This work highlights the importance of soil organic reactive surfaces in reducing trace element bioavailability and phytoaccumulation. Chloride salinity increased Cd accumulation in leaves but not in fruit peel and pulp.