Chemical Science International Journal

Aims: Determine the concentration of trace-metals (Na, K, Mg, Ca, Pb and Zn) in sediments and plant Cenchrus echinatus L. species on Canal of Jandiá and Igarape of Fortaleza in the municipality of Macapa, Amapa, Brazil.

Study Design: The sediment samples were collected (0.3kg) at 05 points on Canal of Jandiá and Igarape of Fortaleza, totaling 10 sampling points, where each point contained a distance of 200m between them, which was determined with the aid of equipment Garmin GPS model. The samples of plants of the Cenchrus echinatus L. species (0.2kg) were used to determine the concentration of metals and submitted to calcination and filtration process, and analyzes carried out in atomic absorption spectrophotometer model 6300 Shimadzu AAS.

Place and Duration of Study/Methodology: The study and analyses were carried out at the Department of Biological Sciences and Health, in Laboratory of Atomic Absorption and Bioprospecting (LAAB), Laboratory of General and Analytical Chemistry of Federal University of Amapá and Department of Aquaculture and Fisheries (Embrapa) between January to October of 2011.

Results: The statistical significance was calculated using a two-tailed Student t test and Mann-Whitney U test with 95% confidence interval. In Igarape of Fortaleza, the values ​​of trace-metals in sediments for K ranged from 0.2mg/L to 6.1mg/L, Ca from 5.5mg/L to 18.1mg/L, Mg from 1.4mg/L to 1.6mg/L, Pb from 0.13mg/L to 4.2 mg/L and Zn from 1.3mg/L to 2.1mg/L. In the Canal of Jandiá, measured values of Na ranged from 0.0 to 9.4mg/L, Ca from 5.3mg/L to 18.4mg/L, Pb from 0.4mg/L to 1.6mg/L and Zn from 1.6mg/L to 2.7mg/L. Trace-metals not detected were Na, in Igarape of Fortaleza, and K, in the Canal of Jandiá. The results obtained in the determination of trace-metals (Na, K, Mg, Ca, Pb and Zn) in plants of the Cenchrus echinatus L. species in the Canal of Jandiá, showed that the measured values of Na ranged from 0.0 to 9.4mg/L, Ca from 5.9mg/L to 1.1mg/L, Pb from 0.4mg/L to 1.6mg/L and Zn from 0.2mg/L to 2.07mg/L. In Igarape of Fortaleza, the trace-metal of Ca ranged from 8.07mg/L to 26.2mg/L, Mg from 1.3mg/L to 1.4mg/L, Pb from 0.06mg/L to 0.1mg/L and Zn from 0.4mg/L to 0.5mg/L. Trace-metals not detected were Na, in Igarape of Fortaleza and Mg and in the Canal of Jandiá. The ion K had no variation in measurements in Igarape of Fortaleza.

Conclusion: The metals Pb and Zn exceeded the reference values of CONAMA nº344/2004 resolution, which undertake plants and sediments. For the other elements the concentrations were found within recommended limit. However, they require special attentions since the concentration of the metals at some points are close recommended limits.