Air contaminants and litter fall decomposition in urban forest areas: The case of São Paulo - SP, Brazil

• Published in: Environmental research 2017-05, Vol.155, p.314-320
• Main Authors: Lamano Ferreira, Maurício, Portella Ribeiro, Andreza, Rodrigues Albuquerque, Caroline, Ferreira, Ana Paula do Nascimento Lamano, Figueira, Rubens César Lopes, Lafortezza, Raffaele
• Format: Article
• Language: English
• Subjects: Air Pollutants - analysis; Atmospheric pollutants; Brazil; Cities; Environmental Monitoring; Forests; Heavy metals; Metals, Heavy - analysis; Plant Leaves; Rain; Rainforest; Seasons; Soil ecotoxicology; Trees
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2017.02.023

Urban forests are usually affected by several types of atmospheric contaminants and by abnormal variations in weather conditions, thus facilitating the biotic homogenization and modification of ecosystem processes, such as nutrient cycling. Peri-urban forests and even natural forests that surround metropolitan areas are also subject to anthropogenic effects generated by cities, which may compromise the dynamics of these ecosystems. Hence, this study advances the hypothesis that the forests located at the margins of the Metropolitan Region of São Paulo (MRSP), Brazil, have high concentrations of atmospheric contaminants leading to adverse effects on litter fall stock. The production, stock and decomposition of litter fall in two forests were quantified. The first, known as Guarapiranga forest, lies closer to the urban area and is located within the MRSP, approximately 20km from the city center. The second, Curucutu forest, is located 70km from the urban center. This forest is situated exactly on the border of the largest continuum of vegetation of the Atlantic Forest. To verify the reach of atmospheric pollutants from the urban area, levels of heavy metals (Cd, Pb, Ni, Cu) adsorbed on the litter fall deposited on the soil surface of the forests were also quantified. The stock of litter fall and the levels of heavy metals were generally higher in the Guarapiranga forest in the samples collected during the lower rainfall season (dry season). Non-metric multidimensional scaling multivariate analysis showed a clear distinction of the sample units related to the concentrations of heavy metals in each forest. A subtle difference between the units related to the dry and rainy seasons in the Curucutu forest was also noted. Multivariate Analysis of Variance revealed that both site and season of the year (dry or rainy) were important to differentiate the quantity of heavy metals in litter fall stock, although the analysis did not show the interaction between these two factors. Precipitation appeared to be an important factor to disperse air pollutants; one method to better regulate this process is the development and integration of green infrastructure at city level, which might contribute to nature-based solutions. Results suggest that although the Curucutu forest is not very far from the MRSP, which could result in heavy metal levels similar to those observed in the Guarapiranga forest, the weather conditions, geographic location and rainfall rates might act as eff