Effects of Green Waste Compost Addition to Dredged Sediments of the Matanza-Riachuelo River (Argentina) on Heavy Metal Extractability and Bioaccumulation in Lettuce (Lactuca sativa)

Abstract

Soil amendments can be an effective and low-cost treatment to reduce metal bioavailability of contaminated dredged sediments disposed on land. The effect of green waste compost addition on Cu, Cr, Ni, Pb, and Zn extractability and bioaccumulation in lettuce was studied in a greenhouse experiment, using dredged sediments from different sites of the Matanza-Riachuelo River (Argentina). Moreover, the effect of compost addition in lettuce morphological and biochemical variables was analyzed. The treatments were prepared by adding 15% and 30% of compost to the sediments (w/w), and untreated sediments were used as controls. Metal concentrations in lettuce shoots and metals extracted by DTPA correlated significantly. In the site where the land use is mainly agriculture and cattle grazing, compost addition did not affect the accumulation of metals in lettuce. Conversely, in site where the land use is peri-urban and industrial, compost addition decreased Cr, Ni, Pb, and Zn concentrations in lettuce, similar for both treatments. In particular, in the basin’s more industrialized and densely populated site, the addition of 30% compost to the sediment was more effective in reducing the metals bioaccumulation and improving morphological variables and chlorophyll content in lettuce shoots. The results presented in this study show that the addition of soil amendments, particularly of 30% of green waste compost, can improve the physicochemical properties enabling, for instance, a controlled disposal scheme.