Abstract
Accurate assessment of the type and extent of water pollution is a difficult and complicated task. Therefore, the use of the Water Quality Index (WQI) proves to be a useful tool, as this index has the advantage of resulting in a single number that is easy to communicate and understand. One of the statistical methods that can be used to develop a new WQI equation for a given water body is Multiple Linear Regression (MLR). Therefore, this work aims to develop a new WQI equation for Mirim Lagoon through MLR and to evaluate the suitability of that equation. For this, 154 samples collected at 7 monitoring points of Mirim Lagoon over three years were analyzed, from which the original WQI results were obtained. With these results, MLR was applied, generating a new WQI equation with only three variables: phosphorus, dissolved oxygen (DO) and thermotolerant coliforms. This MLR model obtained an R2 coefficient equal to 0.728, demonstrating that 72.8% of the data variability was explained by the equation generated by this model. Through the paired t test it was possible to demonstrate that the results of the new WQI did not differ significantly from the results of the original WQI, obtaining significance values greater than 0.05 for both absolute WQI values and quality ranges (p value 0.886 and 0.467, respectively), attesting to the adequacy of the new equation. The reduction in the number of variables for monitoring water quality has several advantages, from financial ones, as it makes monitoring less costly, even in reducing the eclipse effect. Therefore, it is concluded that it is of great importance to generate an equation with fewer variables for monitoring the quality of the waters of Mirim Lagoon.
Highlights
Along the entire length of the water bodies, there are several processes that can influence the quality of its waters [28]
The Water Quality Index (WQI) developed by National Sanitation Foundation (NSF) in the USA and adapted in Brazil by CETESB, hereinafter referred to as the original WQI, is calculated by the weighted product of each of its nine parameters
Recent studies have used this WQI in assessing the quality of Mirim Lagoon, which found a likely influence of anthropic activities on its quality, such as agricultural activities developed in its surroundings [39, 46]
Summary
Along the entire length of the water bodies, there are several processes that can influence the quality of its waters [28]. From a historical point of view, having urban centers developed around freshwater rivers and lakes, it can be said that these water resources play a great role in the development of populations [29]. Influenced by the new standards of modern life, as well as the ever-increasing population growth rate, the demand for water is increasing. This and other factors, such as the inappropriate disposal of solid waste and industrial and urban effluents, end up influencing a worrying increase in the pollution of water resources
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