Avaliação da influência antrópica na drenagem do Igarapé do Quarenta e Orla de Manaus

Abstract

The intense growth population of Manaus city, driven by a regional free zone, and inadequate environmental policies have caused the degradation of its urban watercourses, such as Educandos basin. In this The distribution and correlations of contaminants, impact of anthropic activity on the urban streams, seasonal effects and potential influences of the basin along the Black river (in Manaus shoreline) were evaluated. This environmental work was made in two seasons, dry and wet, in 17 places: three in the Educandos basin springs (in the environmental protection area of the UFAM campus), eight in the Quarenta, Mestre Chico and Cachoeirinha urban streams, and six on Black river, considering amounts and downstream of the mouth basin. This study was based on physical and chemical parameters in samples of water and suspended solids. Were mensured in water: pH, CE, turbidity, temperature, and TSS, anions (NO3-, NO2-, F-, Cl-, SO42-, Br-, PO43- and HCO3-) and cations (Ni, Pb, Cr, Cu, Fe, Zn and Al), with these metals also measured in suspended solids. Liquid chromatography was used to anions analysis (except HCO3-), the cations quantification was made by ICP-OES, the extraction of the suspended metals by microwave and other parameters by classic methods. Multiparametric statistics (PCA and HCA) was used to evidence the effects of anthropic activity and the distribution of contaminants. Basin contamination altered almost all quantifiable parameters in the urban streams, except Fe, Zn and Al in suspended solids and temperature. Quarenta brook didn’t change significantly, for the places used in this work, the Black river water quality levels in Manaus shoreline. The streams were slightly more contaminated in the dry season. C.E., pH, HCO3-, Cl-, F- and SO42- were higher in the places with the highest concentration of domestic sewage, with an increase of their levels in the last decades. Ni2+, Cr3+, Pb2+ and Cu2+ and V+ in the suspended solids predominated in the industrial zone, with some levels, in these places, above NOAA’s reference table. Pb2+, Cr3+, Cu2+, V+ and Hg in water were not quantifiable at any point, suitable to CONAMA's resolution standards for water quality, with lower levels than those verified in previous works, a possible indicator of potentially toxic metals emission reduction.