Análise de metais pesados (chumbo e cádmio) no caranguejo-uçá (Ucides Cordatus Linnaeus, 1763) enquanto bioindicador de contaminação ambiental na região de Santo Amaro - BA

Abstract

Between the years of 1960 and 1993, a factory of beneficiation of lead ore remained active in the city of Santo Amaro -BA, where caused significantly environmental contamination of heavy metals due to no environmental concern. This study is aimed to characterize the currently environmental contamination by lead and cadmium in samples of crab (uçá crab) as biomarkers of contamination of the aquatic environment. In order to investigate the environmental contamination, samples of these crabs were collected in six pre-established points, then a database was created with information such as sex, physiological condition, and biometric data. Furthermore, the specimens were dissected in order to remotion of the gills, hepatopancreas and muscle tissues. The removed parts were individually weighted, transferred to Falcon tubes and stored in a freezer at -30 ºC. Sample treatment was carried out evolving freeze drying, granulometric adjust with analytical sieve (400µm / 200µm), digestion with block digestion system equipped with cold finger using nitric acid and hydrogen peroxide, dilution with ultrapure water to 25 mL and determination of metals by ICP-OES. According to RDC (Resolução da diretoria colegiada) Nº42, August 29th, 2013, the maximum value of organic contaminants such as lead and cadmium in food is 0,5mg/Kg (humid weight). The results obtained from the analysis of crabs collected show values of lead almost 3 times higher than the value stablished by the RDC. For Cadmium values, the values found are within the recommended range by the RDC. Is possible to recognize that the range of lead and cadmium is not homogeny spread in the points where the specimens were collected. In addition, was not identified a proportionality between the levels of lead and cadmium and distance from the factory. The points of collect that was identified higher levels of lead were P02, P03, P05, P04 and P06. Cadmium values higher than the preconized by the RDC were not found in any point of collect. These results show that the specimens of the analysed area have high level of lead contamination, and a possible risk for cadmium. The reason of this result are external factors that are linked to the history of the city.