Regulating (ecosystem) services of an urban natural area: A case study in the State of Rio de Janeiro, Brazil.

Peri-urban conserved natural or semi-natural areas provide several ecosystem services and assist in reducing air pollution in cities. The aim of this study is to assess the contribution to the improvement of air quality of a small area (<1 km) adjacent to a city in the Metropolitan Region of Rio de Janeiro (Brazil), which is seriously affected by vehicular and industrial emissions of pollutants. Hydrocarbon (HC) and carbonyl compounds (CC) levels were determined, by employing TO-15 and TO-11A US EPA Methods, respectively, in both the urban and green areas. The results showed that the concentrations of anthropogenic HC were approximately 1.7-2.1 times higher in the urban area which confirms that the natural park assists in the dispersion and reduction of pollutants. In the case of the CC compounds, for samples that were collected in the morning, the total mean and median values were 1.3-1.6 times higher in the urbanized zone, while during the afternoon the green area showed values that were 1.5-1.9 times higher. These results suggest that in the green area, the emission or formation of CC compounds through photochemical processes is significant, particularly in the afternoon. Anyway, the ozone forming potential was found to be lower within the natural park in both periods, which confirms the positive role played by conserved natural areas outside or surrounding extensive metropolitan areas in the reduction of atmospheric pollution, in spite of the negative impact of anthropogenic emissions.