Land use and groundwater quality: the case of Baixo Acaraú Irrigated Perimeter, Brazil

Eunice Maia De Andrade,Deodato Do Nascimento Aquino,Deborah Mithya Barros Alexandre,Helba Araújo Queiroz Palácio,Fernando Bezerra Lopes

doi:10.1590/s1806-66902010000200006

Abstract

The aim of this work was to identify and to investigate the determining factors of water table quality in the Irrigated Perimeter of Baixo Acaraú, Ceará, Brazil, using factor analysis/principal component analysis (FA/PCA). It was sampled nine shallow wells spread out on two different types of land: uncultivated area (A1) and irrigated area (A2). Groundwater was sampled monthly from Dec/2003 to Nov/2005, Nov/2006, Mar and April/2007. We measured the following parameters: pH, electrical conductivity (EC), and concentrations of Na+, Ca2+, Mg2+, K+, Cl-, PO4-, NH4-, NO3-, SO4-2, HCO3- and CO3- 2. The PCA resulted in a model composed of three components that explained 93.06% and 83.72% of the total variance of the data set from A1 and A2, respectively. It was found that the determining factors of water quality were the mineralization processes and anthropogenic activities in both areas. The anthropogenic activities in the irrigated area were related to nitrogenous fertilizers, while those in the uncultivated area were associated with the presence of septic tanks (from the lack of sewage treatment).

Highlights

Human occupation and land use change the biological, physical and chemical processes of the surrounding ecosystem (ANDRADE et al, 2007); these alterations can be evaluated by monitoring the water quality (MONTEIRO; PINHEIRO, 2004) of the ecosystem
The chemical composition of the groundwater is the resultant of the composition of the water that percolates through the soil and the chemical makeup that directly develops by way of the local lithology
Principal component analysis The best model had a high Kayser Mayer Olkim (KMO) and the highest percent of total variance accounted in a smaller number of factors

Summary

Introduction

Human occupation and land use change the biological, physical and chemical processes of the surrounding ecosystem (ANDRADE et al, 2007); these alterations can be evaluated by monitoring the water quality (MONTEIRO; PINHEIRO, 2004) of the ecosystem. To examine deeper the influence of anthropogenic activities on water quality, scientists have focused on studying irrigated agriculture, the main consumer and one of the main polluters of water bodies, both surface and groundwater (DOWD et al, 2008; MULLER et al, 2007; FENG et al, 2005). Until the 1970s, it was believed that the soils and sub soils worked as filters, retaining the contaminants before they could reach the groundwater. More recently, it was verified that the contaminants can, reach groundwater (AQUINO et al, 2008; MINDRISZ, 2006). The chemical composition of the groundwater is the resultant of the composition of the water that percolates through the soil and the chemical makeup that directly develops by way of the local lithology. The local lithology defines the concentration of the substances dissolved in the water; this concentration increases as the water penetrates through the profile of the soil

Objectives

Methods

Results

Conclusion