Aplicabilidade de Sedimentos Estuarinos em Solos com Baixa Aptidão Agrícola: Efeito na Fertilidade do Solo, Nutrição e Crescimento das Plantas

Abstract

Worldwide estuaries are losing their navigation capability due to the gradual deposition of sediments carried by watercourses, causing silting of the water system and hindering the passage of ships. The maintenance of these navigation channels that give access to ports through dredging work and subsequent disposal of these wastes, are of high cost for the ports, and implies in high impact to the environment. A plausible alternative is applying these dredging waste in nutrient-poor areas, which could replace all or part of conventional fertilizers, in order to restore the nutritional losses of soil, besides causing rejuvenation of the estuary. To evaluate this form of disposal of dredged material, sediments deposited in the Jurujuba Bay and Port of Niterói, State of Rio de Janeiro were analyzed for their potential risks to the environment and public health. The study includes grain size of the sediment, classification of the underwater residue, fertility levels, concentrations of heavy metals, pesticide contents, presence of pathogenic organisms, identification of oil-derived components, and salinity. The results were compared to reference standards in order to predict about the potential employment of this material as "mineralized fertilizer" for agricultural purposes. Preliminarily inferred analysis suggests that the sediment is nonhazardous waste. These clastic materials were also evaluated for the other parameters, and results, which varied in different places, are pH (7.7 -7.8), MO (53 -55 gdm^-3 ) , Zn (211-319 mg dm^-3 ), Cu (160-214 mg dm^-3 ), Hg (1.71 - 1.15 mg dm^-3 ), coliforms thermotolerant (14-38 NMP/gST), coliforms fecal (1-600 NMP/gST). These values were promising regarding the use of clastic material as a source of mineralized fertilizer for the purpose for which it is intended, once the studied sediments present in their chemical composition concentrations macro and microelements with satisfactory levels. This will certainly minimize the waste disposal problem in contaminated bodies of water, drastically reducing the environmental implications of their improper disposal on the environment.