engleski

Salinity decreases dissolved organic carbon in the rhizosphere and increases trace elements phytoaccumulation

Soil degradation processes, like organic matter (OM) depletion, accompanied with metal contamination and salinisation are getting exacerbated, becoming a serious threat to crop production and human food security. A greenhouse study was conducted to assess a factorial combination of salinity (0, 20, 40 and 60 mM NaCl) and cadmium (0.3, 2.5 and 5.4 mg Cd kg-1) in organic soil (>90% OM) influencing dissolved organic carbon (DOC) in the rhizosphere and mineral phytoaccumulation in radish (Raphanus sativus L. var. sativus). A 34-day exposure to increasing NaCl salinity significantly decreased DOC concentration in the radish rhizosphere solution and positively influenced on trace elements (Cu, Zn and Cd) concentration, either in the rhizosphere or in leaf/fruit tissues of radish. Soil contamination by Cd progressively raised Cd concentration in soil solution, but markedly reduced total concentration of Cu and Zn, either in the rhizosphere or in radish leaves. The NICA-Donnan chemical speciation/distribution modelling confirmed the predominance of dissolved organic reactive surfaces (i.e. fulvic acid) in Cu and Cd chemisorption/complexation processes in the whole range of applied treatments (NaCl and Cd), whereas for Zn speciation organically-complexed pool dominated at low salinity (0-20 mM NaCl), and free Zn2+ was the most important one at increased salinity (≥40 mM NaCl). These results confirm that as a consequence of diminished dissolved organic pool under excessive salinity, Cu, Zn and Cd biogeochemistry in the rhizosphere can be affected in a way that would enhance solubility and phytoaccumulation of these trace metals into the food crops.

trace elements; DOC

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