Bioavailability of Sodium and Trace Metals under Direct and Indirect Effects of Compost in Urban Soils. Issue 3 (1st May 2016) - Kargar, Maryam
Abstract : The contamination of urban soil with sodium (Na) and trace metals can be one of the major concerns for groundwater contamination and street tree health. The bioavailability of Na, copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in urban soil amended with 0, 5, and 10% w/w compost was evaluated at none, medium, and high contamination levels of soil mixtures. The relationship between soil properties, compost addition, contamination level and metal uptake by barley ( Hordeum vulgare L.) was determined using multivariate linear regression and path analysis. The results indicated the direct negative effect of compost on metal absorption possibly through specific complexation for Cu, Zn, Cd, and Pb. Compost can also affect the absorption of Na and Cd indirectly by means of cation exchange capacity (CEC) and pH. The degree of soil contamination with metals can affect the competition of cations for the complexing sites of the soil mixtures and, therefore, can induce changes in metal availability for plants. Compost addition to the soil also increased nutrient availability, except for ammonium (NH4 + ) and nitrate (NO3 − ). We concluded that in the short term, the addition of compost significantly reduced metal bioavailability and improved nutrient availability. However, more studies are required to monitor the long‐term ability of the compost to reduce Na and trace metal bioavailability in urban soil. Core Ideas: Compost can affect metal bioavailability directly and indirectly. Direct effect of compost can be related to the formation of organo‐metallic complexes. Strong bonds form between trace metals and the adsorbing surface in compost. Compost can affect ion concentration and type, which compete to be absorbed by plants. An indirect effect of compost is attributed to modified pH and CEC.