Avaliação localizada de metais em águas pluviais na cidade do Rio de Janeiro

Abstract

As pluviometric precipitation occurs over roofing areas, atmospheric pollutants resulting from urbanization are carried on the surface and directed to conventional urban drainage systems. When available in storage systems, these pollutants can be collected and observed in order to obtain the quality of the precipitated effective volume. This work aims to characterize the rainwater to verify the quality of the water and destine it for drinking use. Thus, some metals and physicochemical parameters present in the rainwater samples collected and stored at the Instituto Fernando Rodrigues da Silveira (CAp-UERJ), located in Rio Comprido neighborhood, in the city of Rio de Janeiro-RJ, were investigated. Sample collection points include: Direct Precipitation (PD), First-Flush (FF) and Reservoir (RR) from November 2017 to October 2018. The methodology consists of analyzes of the metals Calcium (Ca), Cadmium ( (Ni), Lead (Pb) and Zinc (Zn), Conductivity analysis, pH, Chloride (Cu), Iron (Fe), Potassium (K), Manganese , turbidity and volatile organic compounds. Data analysis was performed using R language with multivariate statistical treatment including principal components analysis, Pearson linear correlation, hierarchical grouping analysis, Tukey test and boxplot. The results indicate accentuated characteristics of acid rain at the PD and high turbidity at the FF point. The chloride is within the recommended 250 mg L-1 by Ordinance no. 05/2017 of the Ministry of Health for water potability. Sodium meets drinking water guidelines (200 mg L-1), however, the other metals presented nonconformity throughout the study, indicating natural and anthropogenic influences probably attributed to vehicular emissions close to the site. The disposal system is not efficient to reduce the concentration of metals in the RR, exceeding the limits of potability. Copper, potassium and sodium present higher concentrations in the wet period, exhibiting a seasonal behavior, whereas in the dry period higher concentrations of calcium were observed. Aromatic hydrocarbons such as Toluene, Ethylbenzene and Xylene (TEX) were found, as well as chloroform and ethane at the RR and FF points, possibly due to emissions from the combustion of fossil fuels. In this way, the use of rainwater for human consumption is not recommended.