ESTUDO DA BIOMAGNIFICAÇÃO DO MERCÚRIO TOTAL E ORGÂNICO NA CADEIA TRÓFICA AQUÁTICA NO RIO MADEIRA-RO

Abstract

This research aimed to gain a deeper understanding of the processes of mercury bioaccumulation and biomagnification, as well as the mechanisms of toxicity associated with this metal in the aquatic trophic chain of the Madeira River. The goal was to determine whether contamination exists in organisms ranging from primary (base of the chain) to quaternary (top of the chain) levels. Based on the results, the study aimed to theorize whether there are risks of harm to human health for those consuming fish from this region, considering the maximum allowable quantities set by current regulations. Samples of surface water, phytoplankton, zooplankton, invertebrates, and fish (Branquinha - Potamorhina latior; Dourada - Brachyplatystoma flavicans) were collected along the Madeira River in the Porto Velho-RO region.Total mercury (HgT) and methylmercury (MeHg) were quantified in water using fluorescence spectrophotometry coupled with cold vapor atomic fluorescence spectrometry and pre-concentration on a gold column (CVAFS). For HgT in plankton, invertebrates, and fish, a specialized atomic absorption spectrometer (AAS) was used to measure mercury concentrations in solid samples. Methylmercury was measured using an atomic fluorescence spectrometer (AFS). The quantified results showed that the average concentration of HgT in water was 0.024 μg/kg, with methylmercury levels below the limit of quantification. For phytoplankton, the average HgT concentration was 293.132 μg/kg, and the average MeHg concentration was 29.713 μg/kg. Zooplankton had an average HgT concentration of 367.012 μg/kg and an average MeHg concentration of 37.353 μg/kg. Invertebrates showed an average HgT concentration of 609.310 μg/kg and an average MeHg concentration of 44.060 μg/kg. The Branquinha fish had an average HgT concentration of 385.000 μg/kg and an average MeHg concentration of 235.000 μg/kg, while the Dourada fish had an average HgT concentration of 975.000 μg/kg and an average MeHg concentration of 790.000 μg/kg. Consequently, the HgT growth occurred as follows: 1244093.5% from water to phytoplankton, 1557675.9% from water to zooplankton, 66.0% from zooplankton to invertebrates. When comparing the two fish species, the Branquinha, which is detritivorous, exhibited a 153.3% increase compared to the carnivorous Dourada. The results indicate evidence of mercury bioaccumulation and biomagnification in the aquatic food web of the Madeira River. Despite this, the fish remain within the limits established by Mercosur for mercury concentrations, suggesting that they do not pose a direct risk to human health. However, it is important to emphasize the significance of monitoring and controlling this contamination to preserve the health of aquatic ecosystems and ensure safe nutrition for populations.