Relations of the groundwater quality and disorderly occupation in an Amazon low-income neighborhood developed over a former dump area, Santarém/PA, Brazil

Groundwaters are better protected than surface waters. However, in unconfined conditions, groundwater can be easily contaminated when the land use and occupation are considered as determining factor. In the city of Santarém/PA, Brazil, the district of Santo André has experienced a population growth until reaching areas close to a former dump, and this may have caused an impact on the quality of the Alter do Chão Aquifer. In order to analyze these impacts generated, seven ground-penetrating radar sections to set the dump boundaries, physicochemical and bacteriological analyses in six pumping wells to set the drinkability values of the water, and potentiometric surface map in order to understand groundwater flow directions were carried out. Geophysical data indicated the presence of lateritic crusts, buried pipelines, as well as faults and fractures, which may serve as preferred pathways for contaminant infiltrations up to the aquifer. The geophysical data also indicated the dump boundaries are larger than expected, where the population has built their residences over the compacted garbage. Consequently, every pumping well presented total amounts of coliforms higher than the allowed values, and three of these wells have above 10 mg/L values of nitrate, indicating the region has waters in disagreement to the drinkability standards set, directly influenced by the contamination of the former dump under the Alter do Chão Aquifer.