Análise de risco associado à qualidade da água e sua relação com indicadores ambientais em reservatórios do Rio Grande do Norte - RN

Abstract

The state of Rio Grande do Norte is located in the Brazilian semiarid with more than 3.5 million inhabitants. Due to its environmental characteristics, it faces problems with water scarcity, aggravated in the last years due in part to the climate changes represented in the last almost 10 years of extreme drought, the worst of the last 50 years. Therefore, the few available water resources become strategic matters, so that they are conducive to human development. This scenario is aggravated when the quality of the water is affected due to the geological characteristics and the anthropic activities developed in the region. In this sense, it is eminent that effective actions need to be implemented in a satisfactory way, encouraging the conservation of water bodies. The study aimed to analyze factors resulting from human development and natural characteristics that may influence the environmental quality of some of the most representative water reservoirs in the state. With this purpose, a geospatial analysis with satellite images was carried out to map the changes in land use and occupation of the productive activities carried out in the years 2008 and 2017 within a 5 km area from the edges of the reservoir. A significant socio-demographic increase was observed, highlighting a growing of activities with polluting potential, such as mining, pisciculture and ceramic industries in a polarized way, remarking the generalized growth of agriculture in the environments of all reservoirs. However, the most important point to stand out in this study was the need for implementation of environmental control, since there was a disregard for environmental policies, represented by the invasion of these activities within the permanent protection areas, describing the potential pollution impact on the water resources and consequently causing clear consequences on the quality of the water and therefore describing an imminent health risk. In order to evaluate the aforementioned facts, studies were conducted in surface water bodies to understand the water quality and the toxicological consequences for the population of the use of this resource. For these purposes, two environmental samples were carried out (2015 and 2017), in order to evaluate the water quality of the reservoirs in the studied environmental scenario. For these purposes, water samples were assessed through physical-chemical variables such as: electrical conductivity, colour, turbidity, pH, total solids, total alkalinity, total hardness, ammoniacal, organic and total nitrogen, chlorophyll, chloride, nitrite, nitrate and phosphorus, as well as metals (Ag, Al, Cd, Co, Cu, Cr, Pb, Fe, Hg, Mn, Ni and Zn). In addition, the alpha and beta radiation levels, radon concentration along with phytoplankton analysis were performed. In soil samples, the content of the aforementioned metals, radon emanated, and gamma-ray emitters (uranium, thorium and potassium) were measured. In the air samples radon was also assessed. The results obtained were compared with the threshold values indicated by national and international legislation. Apart from that, for a risk assessment, the variables of toxicological interest were categorized by comparison with the used reference threshold values to describe the individual risk associated along with by the integration of this information through a composite index. Finally, the spatial pattern of cancer was analysed considering the areas of influence of the water reservoirs and its association with the described risk. And compared with the scores of the risk composite index in order to evaluate possible associations. The results obtained revealed the improper quality of water for human consumption, with potential health consequences besides the need to establish environmental monitoring along with the implementation of mitigating actions against the occurrence of substances of toxicological relevance, considering the risks of associated pathologies linked to an exposure to these agents.