Atmospheric levels, multivariate statistical study, and health risk assessment of odorous compounds (H 2 S and NH 3 ) in areas near polluted urban rivers in the city of Salvador, in Northeastern Brazil

Odors are often associated with nuisance and health risks. In this study, the atmospheric levels of H 2 S and NH 3 were determined in 5 sites near polluted urban rivers during rainy and dry periods in the city of Salvador, Brazil, as well as the relationships between these odorous compounds and meteorological and water quality parameters applying multivariate analysis, and the non-carcinogenic risks (as hazard quotient—HQ). The compounds H 2 S and NH 3 were passively sampled and determined by molecular spectrophotometry. Average concentrations were lower in the rainy period (6.56 ± 0.83 μg m −3 for H 2 S; 8.67 ± 2.50 μg m −3 for NH 3 ) than in the dry period (8.05 ± 1.44 μg m −3 for H 2 S; 10.62 ± 4.39 μg m −3 for NH 3 ), probably due to lower water and air temperatures, which contribute to lower water–air transfer rates and higher precipitation and relative humidity values, thus favoring the removal of these compounds from the atmosphere. The PCA and HCA results confirmed these relationships, as well as showing strong positive correlations between NH 3 , N-NH 4 + , TN, T water , BOD, and EC, and strong negative correlations between H 2 S, pH, and DO, indicating that these water quality parameters also influence the levels of H 2 S and NH 3 in air, thereby confirming a common source for the gas emissions as being mainly from polluted rivers. The maximum H 2 S concentrations were above the odor threshold value established by the WHO in both periods. According to deterministic health risk assessment, the HQ values for NH 3 were below the acceptable limit set by USEPA (HQ = 1). However, all HQ values found for H 2 S (4.28, 2.80, 1.46 at 95th percentile) for the 3 groups of the exposed population in the dry period using probabilistic risk assessment with Monte Carlo simulation were above this limit, therefore indicating human health risks.