Carbonaceous amendment addition as an alternative to decrease phytotoxicity of sediments from the Matanza-Riachuelo Basin (Argentina)

Abstract

Sustainable management strategies for highly polluted dredged sediments are crucial in ports and waterways, where dredging activities take place on a regular basis. In the case of Argentina, the lack of national legislation enables the unregulated sediment disposal in marginal areas, exposing low-resource populations to these sources of pollution. In order to decrease the sediment phytotoxicity for the potential revegetation of dredged sediments from the Matanza-Riachuelo River, with high concentrations of heavy metals, the effect of two types of carbonaceous amendments (biochar, BC, and commercial activated carbon, AC) in different proportions (10% and 20%) was studied. With the defined treatments, germination and root elongation tests, and seedling-level tests were carried out to compare the phytotoxicity of the amended sediments with that of the pure sediment. Lettuce ( Lactuca sativa ) was used as an indicator species. Both amendments in the highest dose (AC20% and BC20%) improved germination index. AC20% presented the highest heavy metal accumulation in biomass for all the metals under analysis, but plants did not exhibit negative morphological alteration or phytotoxic symptoms. By contrast, BC treatments did not improve lettuce’s morphological variables and heavy metal accumulation significantly. Together with adequate agronomic practices, the appropriate selection and dosage of carbonaceous amendments could be a useful strategy to modify the physicochemical conditions of the sediment conveniently, and promote either heavy metal mobilization or stabilization. • The effect of carbonaceous amendments was studied in a heavy metal polluted sediment. • The type of amendment (biochar, activated carbon) and dose (10%, 20%) were compared. • Treatments BC20% and AC20% improved lettuce’s germination index. • AC20% also improved lettuce’s growth parameters significantly. • AC increased Cu, Cr, Zn and Pb uptake by lettuce with no phytotoxic symptoms.