Elsevier

Atmospheric Research

Volume 169, Part A, 1 March 2016, Pages 391-399
Atmospheric Research

Chemical composition monitoring of tropical rainwater during an atypical dry year

https://doi.org/10.1016/j.atmosres.2015.11.001Get rights and content

Highlights

  • The effects of a dry year on the rainwater were investigated in Southeast Brazil.

  • The samples characteristics were associated with the influence of air masses.

  • Rainwater chemical composition was studied on the driest year in the last 10 years.

  • Samples from dry season period presented higher analytes concentrations.

Abstract

The effects of an atypical dry year on the rainwater chemical composition were investigated. Conductivity, pH, major inorganic ions (Na+, K+, Mg2 +, Ca2 +, H+, Cl, NO3, SO42  and HCO3) and trace-elements (As, Cd, Cu, Mn and Pb) were determined in 53 rainwater samples, which were collected on a daily basis over 12 months, in a meteorological station from Juiz de Fora city, Southeast Brazil. The rainwater conductivity ranged from 3.9 a 46.5 μS cm 1 and the pH ranged from 5.04 to 7.10. The analytes concentrations decreased in the following order: Ca2 + > Na+ > K+ > Mg2 + > H+ for cations, NO3 > Cl > HCO3 > SO42  for anions and Cu > Mn > Pb > Cd > As for trace-elements. In general, higher analytes concentrations were observed during the dry season. The total annual rainfall in 2014 was 964.4 mm. This value is significantly lower than the historic annual mean of Juiz de Fora, which is 1550 mm. Therefore, the year 2014 was characterized as a very dry year.

Introduction

Water is a renewable natural resource, fundamental for the survival of living beings. On the water cycle, rain is the most effective scavenging factor for cleaning the atmosphere. During the condensation (rainout) and precipitation (washout), the gases and particulate materials present in the atmosphere are dissolved in raindrops and deposited. Thus, many substances from air pollution are present in rainwater, changing its chemical composition and the pH (Conceição et al., 2011, Flues et al., 2002, Oliveira et al., 2012).

Rainwater chemical constituents come from marine and biogenic aerosols, soil particles and volcanic emissions. Anthropogenic activities, like the use of fossil fuel, industrial emissions, waste incineration, agriculture and mining also contributes to the rainwater composition. The rainwater chemical composition can reflect the atmospheric quality of a specific region and depends on the emission site, on the sea level elevation and on the meteorological conditions (Flues et al., 2002, Santos et al., 2011). The chemical elements and compounds in atmosphere can be transported by wind as aerosols and travel long distances before being deposited by rain, affecting soil, superficial water and vegetation (Honório et al., 2010, Niu et al., 2014). Thus, the chemical investigation of rainwater is useful to trace different sources of atmospheric pollutants (Oliveira et al., 2012).

Southeast Brazil is a tropical area with increase of urbanization and large industrial expansion. This region has been highlighted as an area susceptible to emissions from urban and industrial activities (Lara et al., 2001, Mello and Almeida, 2004). As noted by Lara et al. (2001), numerous studies on atmospheric chemistry have been published in the Northern Hemisphere, but there are few works on rainwater chemistry in Brazil. Furthermore, studies of rainwater composition in the Southeast Brazil are mainly performed in São Paulo (SP) and Rio de Janeiro (RJ) states.

Thus, the purpose of this study was to investigate the rainwater chemical composition in Juiz de Fora, a city of Minas Gerais (MG) state, during a dry year and discuss the results relating them to the meteorological conditions in this period.

Section snippets

Sampling site

The rainwater samples were collected in an open area, in the Universidade Federal de Juiz de Fora (UFJF) meteorological station (latitude: 21° 41′ 40″ S, longitude: 43° 20′ 40″ W, altitude: 937 m), (Fig. 1), which has been operated since 1972. Juiz de Fora is a city with approximately 550,000 inhabitants, 1430 km2 area and is the third more populated city of the MG state (Prefeitura de Juiz de Fora, 2015, Cerqueira et al., 2014). The city has high-altitude tropical climate, with two defined

Climatological conditions in Juiz de Fora city during 2014

The data obtained from the UFJF meteorological station in 2014 allowed a climate characterization of this period under an unusual water shortage. The mean annual value for relative humidity was 75.3%, ranged from 18 to 98%. The air pressure annual mean was 912.4 hPa. The mean solar radiation was 830 kJ m 2 and the summer months (January, February and December) showed highest solar radiation (above 1000 kJ m 2). Table 1 presents the other weather parameters (temperature, wind and precipitation), also

Conclusion

In this work, a study was conducted about rainwater chemical composition, which allowed classifying and evaluating the rainwater quality in Juiz de Fora, during an unusual dry year. It was possible to obtain the concentration level of the major inorganic ions (Ca2 +, Mg2 +, Na+, K+, Cl, NO3, SO42 , HCO3) and trace-elements (As, Cd, Cu, Mn and Pb) in 53 rainwater samples, collected during the year of 2014. Parameters such as pH, conductivity and turbidity were also evaluated. All analytes

Acknowledgements

The authors would like to thank CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico), FAPEMIG (Fundação de Amparo à Pesquisa do Estado de Minas Gerais) and CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for financial support.

References (37)

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