Abstract
Eucalyptus stands are among the most commonly used species for reforestation in the “Vale do Paraiba”. The objective of this study was to detect for the first time isoprene emission by commercial plantations of eucalyptus and relate it to the local tropospheric ozone, thus evaluating the environmental impact of these forests. The samples were collected from denuders of Air Toxics analyzed by gas chromatography through thermal desorption. Ozone was monitored by UV Photometric O 3 Analyzer Model 49i. There were two field trials: one in the summer of 2010 and another in the winter of 2011, in the city of Cacapava, Sao Paulo state. At midday, the highest mixing ratios were detected of isoprene, ranging from a maximum of 8.3 ppbv on November 29, 2010 to 3.5 ppbv on June 30, 2011. Also at midday, the air temperature and photosynthetic active radiation were higher: 33.7°C and 2243 µmol s -1 and 18 oC and 387 µmol s -1 , respectively. The decrease observed in winter weather parameters directly influence isoprene emission which was 65% lower than in weeks of the summer study. The ozone introduced a maximum delayed peak about two hours later than a maximum of isoprene, which is justifiable due to the time required for this gas to react with other precursors and ozone forms. Considering the maximum detected ozone (27.9 ppbv), the atmosphere in this region is considered clean in accordance with the CONAMA.
Highlights
Eucalyptus (Eucalyptus sp.) is one of the main species used in reforestation of degraded areas, due to its rapid growth, low nutrient requirement and wide application in the timber industry (CAMPINHOS JR., 1999)
From 21 hours, the mixing ratio reached an average of 0,8 ppbv and decreased at night, showing the lowest value in the evening. This result confirms the predicted by Harley et al (2004) that is a strong dependence of solar radiation on isoprene emissions by eucalyptus
Rizzo (2006) with samples collected in the Amazon in the summer of 2004 noted that in the early afternoon isoprene peaked at 7,8 ppbv and at night, 0,7 ppbv, indicating the mixing ratio similar to that detected during the night in this work
Summary
Eucalyptus (Eucalyptus sp.) is one of the main species used in reforestation of degraded areas, due to its rapid growth, low nutrient requirement and wide application in the timber industry (CAMPINHOS JR., 1999). The commercial plantations with fast growing species can provide adequate protection to critical areas, assisting in the stabilization of dunes, control of erosion, operation of the catchment areas and the recovery of mining areas (LIMA, 1990). Brazil is the world’s largest producer of pulp (MORA; GARCIA, 2000), with the area reforested eucalyptus growing (FLYNN; SHIELD, 1999). The average annual growth in Brazil is 66% higher than the United States and 38% in South Africa, respectively (FIBRIA, personal communication, 2012). In the current scenario of global climate change, issues such as reforestation programs and expansion of commercial forests are increasingly debated and studies that provide an understanding of the consequences caused by this activity are necessary
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