Source Apportionment of Chemical Elements and Their Geochemical Baseline Values in Surface Water of the Parauapebas River Basin, Southeast Amazon, Brazil

Abstract

The present work aims to evaluate the chemical quality and establish the geochemical baseline values of elements in the surface waters of the Parauapebas River basin (PRB), which is one of the major subbasins in the Itacaiúnas River watershed (IRW) located in the Brazilian Amazon. A total of 327 surface water samples were collected during the rainy and dry seasons in 2017. Results indicate that waters are slightly acidic to alkaline (pH 6 to 8), and there was a strong influence of the seasonal variation on water quality, with higher values of turbidity, Fe, Al, Mn, TDS, etc. in the rainy season. Two geochemical baseline types for the PRB were defined, i.e., ‘conservative baseline’ (CB), represented by the cumulative frequency curve, and the ‘environmental baseline’ (EB), comprising the sum of natural and diffuse anthropogenic contributions, represented by the 98th percentile. Except Fe, Mn and Al, the CB and EB values of various trace elements (Ba, Co, Cr, Cu, Ni, Rb, Sn, Sr, Ti, V and Zn) were lower than the recommended limits of CONAMA 357/05—class 2. The principal component analysis (PCA) identified the major geochemical association (Al-Ti-Cu-Cr-Ni-V), which is an imprint of the local geological setting. Ni and Cr showed enrichment at sites where mafic and ultramafic rocks are concentrated, while Cu concentration is mainly associated with the north and south mineralization belts. High concentrations of Fe and Mn are characteristic of the waters of this region and this is mostly influenced by specific land use activities and intense weathering/erosion of catchment materials. At the upper Parauapebas, anthropogenic contributions associated with soil use and occupation were also important along with the geogenic effects. The obtained results regarding sources of contaminants in some microbasins can be taken as a starting point for future studies on the environmental quality of the region’s water resources.

Geodiversity in the Amazon drainage basin

“…Another hydrogeochemical research concerns the occurrence and source of toxic minerals in rivers, including but not limited to (heavy) metals such as mercury, arsenic, manganese, copper and iron [132, [153][154][155][156][157]. Though human activity is often seen as a source of pollution, research has shown that human activity is only partly to blame for the presence of polluting minerals [132,155], or that all pollution seems to be geogenic (i.e.…”

“…Though human activity is often seen as a source of pollution, research has shown that human activity is only partly to blame for the presence of polluting minerals [ 132 , 155 ], or that all pollution seems to be geogenic (i.e. originating from the natural environment) [ 153 , 154 , 156 , 157 ]. Moreover, the chemical characteristics of water are strongly influenced by seasonal variations [ 154 ].…”

“…originating from the natural environment) [ 153 , 154 , 156 , 157 ]. Moreover, the chemical characteristics of water are strongly influenced by seasonal variations [ 154 ]. The hydrological regime in the ADB is not static; it is characterized by periodical flooding.…”