Mercúrio total e Metilmercúrio em sedimentos de fundo do lago Paru sob influência do pulso de inundação do Rio Solimões, no município de Manacapuru - Amazonas

Abstract

To check the influence of the flood pulse of the Solimões River in the Lake Paru (Manacapuru, Amazonas) in this study were determined concentrations of total mercury (THg) and methylmercury (MeHg) in bottom sediments in two seasons. The samples were collected in April (flood) and October (dry) in 2013 at Solimões River Basin. The locations of collected were 10 points; four located under influence of the black waters of the stream that flow into the lake and others next to the Solimões River. To analyze HgT, the sediments samples < 200 mesh were extracted with HCl:HNO3 and filtered through a cellulose membrane (3,0 μm and 9 cm) by approximately two hours. To analyze MeHg the samples < 200 mesh and lyophilized were extracted with 25% KOH/MeOH at 68°C by approximately four hours. The concentrations of HgT were determinates by atomic absorption spectrometry coupled to cold vapor generator (CV-AAS) and MeHg by aqueous ethylation separated by chromatography and detection by atomic fluorescence gas (GC- AFS). The results indicated that the means concentrations of HgT were 89,19 μg kg -1 (flood) and 115,07 μg kg -1 (dry), while the MeHg were 0,78 μg kg -1 (flood) and 0,17 μg kg -1 (dry). In terms of distribution was observed that HgT and MeHg don´t occur in the same way in both periods studied. At dry predominantes the deposition and at flood the remobilization of HgT. The MeHg has increase in the flood. Finally the HgT and MeHg concentrations at bottom sediments show the seasonally effect under the flood pulse at Solimões River and consequently in mercury cycle at the Paru Lake.