Carla Maria Salgado Vidal Silva

Cluster analysis and geochemical processes for the characterization of the aquifer system in Maracanã/São Luis/MA

To better know the aquifer system in the Maracana Environmental Protection Area were collected samples in four campaigns; the first during the drought season and the others in the following rainy one. The water samples were analised for eleven hydrochemical parameters, CE, Ca2+, Mg2+, Na+, K+, Cl-, SO42-, HCO3-, NO3-, Fe and P. Cluster analysis separated the wells in the area, identifing three different groups that exploit water with electrical conductivity in the ranges of 230 to 400 μS/cm, 87 to 210 μS/cm, and 22 to 64 μS/cm, respectively. Data show a predominance of sodium chlorinated water. With these results and identification of geochemical processes determined by changes in concentrations of Fe and P it was possible to develop a model that identifies the aquifer of the aquifer system exploited by each well.

Factor Analysis in the Study of Geochemical Processes in the Apodi Sedimentary Basin, Northeast of Brazil

Wells of the Jandaira aquifer (in the Northeast of Brazil) were sampled for analyses of Ca, Mg, Na, K, Cl, SO4 , HCO3 , CO3 , NH4 , NO2 , NO3 , Fe, pH, hardness, and electric conductivity (EC). 87 wells were sampled during the dry season of 2009 and during the rainy season of 2010. R-mode factor analysis was applied, using WINSTAT software and the centroid method and Varimax rotation, for the identification of interrelations between the parameters studied. Variables that contribute significantly to the principal factor during both dry and rainy season are Cl, EC, hardness, Na and Mg; K plays a role during the dry season only and CO3 2during the rainy season. It is seen that, in general, recharge to the aquifer reduces the load of the two principal factors in favor of the others. R-mode factor analysis emphasizes the seasonal changes that occur, even when they are too small to be detected in the individual results of chemical analyses on the large compound of samples.