title: Air contaminants and litter fall decomposition in urban forest areas: The case of São Paulo - SP, Brazil.
abstract: 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 efficient physical barriers against the dispersion of pollutants in the urban area. However, it is important to highlight that in the period studied (2012-2013), MRSP presented unusual features during the winter period marked by the highest levels of precipitation which was due to several numbers of frontal systems and also due to their permanence for a couple days in the region. Thus, it is recommended to continue this study in order to obtain a database for characterizing the seasonal variation of air pollution levels in the litter fall and their adverse effects on ecosystem processes in these remnants of the Atlantic Forest.
authors.affiliation: Smart and Sustainable Cities Program, University Nove de Julho (UNINOVE), São CEP SP, Brazil.
authors.forename: Maurício
authors.initials: M
authors.lastname: Lamano Ferreira
authors.affiliation: Smart and Sustainable Cities Program, University Nove de Julho (UNINOVE), São CEP SP, Brazil; Professional Masters in Environmental Management and Sustainability, University Nove de Julho (UNINOVE), São Paulo CEP 05001-100, SP, Brazil.
authors.forename: Andreza
authors.initials: A
authors.lastname: Portella Ribeiro
authors.affiliation: Health Directorate, University Nove de Julho (UNINOVE), São Paulo SP, Brazil.
authors.forename: Caroline
authors.initials: C
authors.lastname: Rodrigues Albuquerque
authors.affiliation: Professional Masters in Environmental Management and Sustainability, University Nove de Julho (UNINOVE), São Paulo CEP 05001-100, SP, Brazil.
authors.forename: Ana Paula do Nascimento Lamano
authors.initials: AP
authors.lastname: Ferreira
authors.affiliation: Oceanographic Institute, University of São Paulo, São Paulo SP, Brazil.
authors.forename: Rubens César Lopes
authors.initials: RC
authors.lastname: Figueira
authors.affiliation: Department of Agricultural and Environmental Sciences, University of Bari 'A. Moro', 70126 Bari, Italy; Center for Global Change and Earth Observations (CGCEO), Michigan State University, East Lansing, MI 48823, USA.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Lafortezza
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001938:Brazil; D002947:Cities; D004784:Environmental Monitoring; D065928:Forests; D019216:Metals, Heavy / Q000032:analysis*; D018515:Plant Leaves; D011891:Rain; D012621:Seasons; D014197:Trees
chemical_list: D000393:Air Pollutants; D019216:Metals, Heavy
keywords: Atmospheric pollutants; Heavy metals; Rainforest; Soil ecotoxicology