Dynamics of heavy metals in the waters of Igarape do Quarenta: The water body that crosses the industrial hub in the brazilian amazon

Abstract

This study aimed to characterize an important body of water that crosses the industrial pole of Manaus – Igarapé do Quarenta, in Amazonas, and to evaluate possible sources of heavy metals in these waters. It is known that the anthropic and industrial influence is very intense in these waters, which significantly increases the levels of heavy metals. Thus, six water collections were carried out in the Quarenta creek, between the months of September and November 2019, every two weeks. Samples were collected near the surface, in the middle of the stream. A metalon stick was used to aid in water collection. The samples were collected in polyethylene bottles, conditioned and transported to INPA's Environmental Chemistry laboratory, where pH and electrical conductivity were determined by potentiometry. Samples for metal analysis were acidified with nitric acid. The samples were then transported to the Water Reuse Research Laboratory at Samsung da Amazônia. The results showed that the waters of the Quarenta stream are close to neutrality (pH from 6.87 to 7.03), which contradicts the acid values characteristic of the region. The electrical conductivity values exceeded 300 µS cm 1, which places the electrolyte charge of these waters almost 20 times higher than the natural values. Among the heavy metals studied, the highest contents were for Fe and Mn, whose concentrations were higher than those established by legislation. Along the Quarenta stream, sinks of heavy metals can be seen, probably due to the phenomenon of dilution or precipitation of these materials. The PLI demonstrated that there is a large polluting load of Pb, Cd, Cu and Mn. The HCA study showed associations between Mn – Fe, Cu – Cd, Ni -Pb and Cr – Zn, which reflect biogeochemical processes being altered by anthropogenic factors. Finally, PCA informs that pH and electrical conductivity inversely influence the concentrations of Zn and Cd and that Ni is the most representative metal in the dataset.