Investigation of rainwater contamination sources in the southern part of Brazil

Abstract

Rainwater quality is influenced by air pollutants and can affect sensitive ecosystems. This study was conducted to identify the sources of rainwater contamination in a receptor investigated in the southern part of Brazil. A total of 22 rainwater samples were collected at Florianópolis, Brazil. The sampling station is influenced by continental emissions (soil resuspension, traffic emissions and combustion) and marine aerosols. Over the sampling period, the average pH and electrical conductivity (EC) of the precipitation was found to be 4.97±0.41 and 14.68 μS cm⁻¹±13.47, respectively. In addition to pH and EC, ions and trace metals in the collected rainwater were quantified. The results were investigated by a combination of techniques including principal component analysis (PCA), a back trajectory model and other statistical and graphical interpretation methodologies. A PCA showed that Cl⁻, Na⁺, Mg²⁺ and part of the K⁺ and content were mainly contributed by marine aerosols, whereas the contribution from continental sources (combustion, traffic emissions and other urban activities) was dominant in the content of NO ₃⁻ and part of the and Mn content. Soil resuspension was responsible for the concentrations of most of the trace metals (apart from Mn) and Ca²⁺ in the rainwater. An inverse correlation among the elemental concentrations, amount of rainfall and wind speed was observed. The northern transport pathway was identified as being associated with high concentrations of NO ₃⁻ and slightly decreased pH values. However, the low standard deviation observed for the pH values during the sampling campaign also showed a small variation in the data, suggesting that the acidity is most probably being constantly sourced from a natural origin, such as organic acids.

Keywords:

• air pollution
• rainwater
• principal component analysis (PCA)
• HYSPLIT

A special acknowledgement is given to Pedro Luiz Borges Chaffe for GIS support. This work was based on Renata Martins’ dissertation.

Notes

1. Small city located in the state of São Paulo with 71,217 inhabitants.

2. Analysis conducted using data from the meteorological station and measured concentrations.