Water quality assessment in areas under the influence of shrimp aquaculture and estuarine dynamics: the case of Aracati, Ceará

The Jaguaribe River represents the main socioeconomic and environmental development axis of the municipality of Aracati, Ceará. However, the intensification of anthropogenic activities, especially shrimp aquaculture and accelerated urbanization, has altered water quality in the Lower Jaguaribe region. This study aimed to perform a hydrogeochemical diagnosis of surface and groundwater quality, investigating the influence of aquaculture and estuarine dynamics across different hydrogeological domains. The methodology consisted of physicochemical analyses along a longitudinal profile of the river and at an effluent discharge point, alongside in situ chemical monitoring of 20 groundwater wells and static level measurements at 24 points. Surface water results revealed critical degradation along the estuarine reach, characterized by elevated turbidity and nutrient inputs (such as phosphate) driven by shrimp aquaculture. Regarding groundwater, all 20 sampled wells failed to comply with the Maximum Permissible Values established by Brazilian Drinking Water Ordinance GM/MS No. 888/2021 due to critical variations in pH and Total Dissolved Solids (TDS) exceeding 500 mg/L. This vulnerability was strongly pronounced in the shallow Alluvial Aquifer due to its direct hydraulic connectivity with the salinized river, whereas the deeper Barreiras aquitard reflected structural facies variations. It is concluded that the current scenario demands the immediate improvement of effluent management practices and systematic seasonal monitoring, providing a crucial baseline to mitigate progressive salinization and ensure water security in this semi-arid deltaic zone.