Variação sazonal e espacial da concentração dos principais íons no lago Mamiá, Amazonas, Brasil

Abstract

The seasonal variation and spatial concentration of major ions (Na+, K+, Ca2+, Mg2+, Cl-, HCO3 - and SO4 2-) and measured temperature, dissolved oxygen, conductivity and pH, and water transparency, material matter and turbidity were studied in the water of the Solimões River, channel of the lake and the Mamiá lake, located in the city of Coari (AM), during the rising water period, high period, falling water period and start high water period during of the year 2008. The variables in the water column were measured with digital potentiometers. For other determinations of water samples were collected with Ruttner bottle, filtered and preserved. The major ions were analyzed by Atomic Absorption Spectrometry Flame, transparency was estimated using a Secchi disk, suspended material was determined gravimetrically and the turbidity measured in the turbidimeter. To check the behavior patterns of the variables and similarities between stations were used TWINSPAN, cluster analysis and principal component analysis (PCA). Limnological parameters such as temperature, dissolved oxygen, conductivity and pH, mixing and circulation identified in the water column in the Solimões River and lake Mamiá channel. The Mamiá lake was stratified during all periods studied. The concentration of major ions (Na+, K+, Ca2+, Mg2+, Cl-, HCO3 - and SO4 2-) and limnological variables such as water clarity, suspended solids and turbidity in the waters of the Solimões River, channel of the lake and the Mamiá lake showed that the flood pulse of the Solimões an influence on the chemical composition at two stations in the channel of the lake and in the first station the lake Mamiá in the early period of flooding. Seasonality in the concentrations of major ions in Mamiá lake showed the lowest values were found at low tide and the highest at the beginning of the flood. Multivariate analyzes TWINSPAN, cluster analysis and PCA demonstrated the formation of a group consisting of stations in the Solimões River and channel of the lake Mamiá in the start high water period and a second group consisting of other stations of the channel and the Mamiá lake in the all seasons. These analyzes showed that the concentrations of major ions, together with the values found for electrical conductivity, suspended solids and turbidity are limnological indicator of changes in the chemical composition of water in ria lakes during the flood pulse of the Solimões River.