Análise integrada de impactos urbanos no estuário do Rio caraíva e na água subterrânea da Vila Histórica de Caraíva

Abstract

Water is one of the most important natural resources, an essential asset for the environment and for life. Because of this and its decreasing quality in several springs, caused mainly by the indiscriminate use of this resource and the surrounding areas, its monitoring is increasingly necessary in order to ensure responsible and lasting management. Therefore, due to the lack of continuous monitoring of the Caraíva River estuary, the lack of a sewage system in Vila de Caraíva (Porto Seguro, BA), an area of rare scenic beauty and of great tourist importance, and based on requests on the part of the community so that studies in this area could be carried out in the region, this work aims to determine the quality of the underground water of Vila de Caraíva and the surface waters of the Caraíva River estuary and its compatibility with its multiple uses. For that, analyzes were performed of Hydrogenionic Potential (pH), Total Dissolved Solids (SDT), Salinity, turbidity, Hardness, Chloride, Nitrate, Nitrite, Ammonia, Iron and Total and Thermotolerant Coliforms, of 24 wells, and the results were analyzed accordingly with the recommendations in Conama No. 396/2008, in Ordinance No. 5/2017, with the method of interpolation by Kriging and analysis of use and occupation of the area of influence of the wells and their correlation with water quality. In the Caraíva River estuary, six sampled points were selected during three campaigns to analyze water quality, where pH, Temperature, Dissolved Oxygen (OD), SDT, Conductivity, Salinity, Turbidity, Total and Thermotolerant Coliforms, Biochemical Demand of Oxygen (BOD), Nitrate, Nitrite, Total Nitrogen, Chlorophyll-a, Ammonia, Iron, Chloride, Total Phosphorus, Dissolved Phosphorus, and Total Solids. The results were analyzed according to what is recommended by Conama nº 357/2005, based on the calculation of the Water Quality Index (IQA), Principal Component Analysis (ACP) and the use and occupation of the basin's soil. Among the results obtained in the analysis of the quality of groundwater, discrepant values to the legislate were found for Chloride (15.35 to 358.24 mgL-1), Nitrate (0.10 to 15.79 mgL-1), pH (5 , 09 to 8.51), Thermotolerant Coliforms (3.0 to 1100.0 NMP100mL-1), SDT (24.0 to 1592.0 mgL-1), Iron (0.68 to 27.27 mgL-1) and Turbidity (6.10 to 41.00 NTU), being, according to the analyzes carried out, directly related to the inadequate sanitary sewage in the Vila and the characteristics of the region's soil. For the water quality results of the Caraíva River estuary, discrepant values were verified to the legislated for Total Phosphorus (5.99 to 0.02 mgL-1), Ammonia (0.01 to 3.86 mgL-1), Nitrate ( 0.05 to 1.08 mgL-1), OD (7.85 to 2.64 mgL-1), BOD (15.78 to 3.60 mgL-1), Iron (6.07 to 0.29 mgL -1), Chlorophyll a (5.15 to 33.62 mgL-1), pH (8.10 to 5.43), Total Nitrogen (0.06 to 3.41 mgL-1), mainly related to activities human activities carried out in the region. The results of the IQA indicated that the water in the estuary is classified as having a good and acceptable quality. ACP has already demonstrated that there is a positive relationship between water quality and rainfall. In view of this, it is essential to take actions by the public authorities and the population that aim to adapt the sewage system in the Vila, given the importance of valuing environmental health, well-being and tourist attractiveness in the region