Dados da Submissão

Título

Groundwater quality evaluation for drinking and irigation in the Mirandiba Basin: Water quality indexes and GIS-based mapping

Texto do resumo

Water scarcity has become a global issue mainly in arid to semi-arid regions. In this sense, it is imperative to recognize the reserves for the efficient use and integrated management of the drop of water available (water resources management). The Mirandiba town, located in a semi-arid region of Pernambuco, NE Brazil, suffers from surficial water shortage, and groundwater from the Mirandiba Basin constitutes the foremost long-term water source for drinking, agriculture, pasture, economic activity, etc. Although the significant role of groundwater in living activities, groundwater quality information is still poorly known. In this study, physical-chemical parameters (potential of hydrogen [pH], electrical conductivity [EC], total dissolved solids [TDS], Total Hardness [TH], sodium [Na+], calcium [Ca2+], magnesium [Mg2+], potassium [K+], chloride [Cl−], sulfate [SO42−], bicarbonate [HCO3−], nitrate [NO3−], and total iron [Fe]) of sixty-seven groundwater analyses were employed. All parameters obtained were compared with those from the World Health Organization (WHO) and Brazilian standards. The parameters results were used to retrieve water quality indexes for drinking (DWQI) and irrigation. Furthermore, selected parameters and calculated index values in a GIS-based (ArcGIS Desktop 10.7) environment produced interpolated maps to reveal groundwater spatial variability. pH values range from 4.2 to 9.4 (avg. 6.5, std deviation 1.1) with nineteen samples slightly out of the WHO limits. For EC, TDS, and TH, respectively, three, three, and two samples surpass the WHO threshold. Ca2+ and Mg2+ varied from 2 to 80 mg/L and 2.5 to 117 mg/L within WHO limits, whereas Na+ and K+ ranged from 2 to 338 mg/L and 4 to 69 mg/L with two and four samples above WHO allowable limits. SO42− and NO3− varied from below the detected limit to 196 mg/L and 0.01 to 3.7 mg/L within the WHO threshold, whereas Cl− and HCO3− varied from 14 to 701 mg/L and 4 to 483 mg/L with eight and one, respectively, groundwater samples beyond WHO limits. Conversely, Fe varied between 0.15 and 0.97 mg/L showing more than half of the samples slightly above the WHO recommended threshold (avg. 0.33, std deviation 0.16). Drinking water quality indexes were calculated using the obtained values compared to WHO quality standards and provided DWQI ≤ 102 mainly within the excellent (sixty-one samples) and good (four samples) categories for drinking purposes. Sodium Absorption Ratio (SAR), Soluble Sodium Percentage (SSP), Kelley Ratio (KR), Residual Sodium Carbonate (RSC), and Permeability Index (PI) as well as salinity [EC/TDS] were used to evaluate the suitability of groundwater for irrigation use. All irrigation ion-based indexes, except MH, showed that most groundwater is suitable for irrigation purposes. Water quality indexes and resulting GIS maps reveal that groundwaters are adequate for drinking and irrigation. Those results should be used to provide knowledge for society, decision-makers, and the scientific community. Furthermore, the data must be employed to build a monitoring network for continuous information on water quality since the work results represent only a snapshot.

Palavras Chave

Drinking Water Quality; Irrigation Indexes; GIS-based techniques; Mirandiba Basin; NE Brazil