Use of levoglucosan, potassium, and water-soluble organic carbon to characterize the origins of biomass-burning aerosols Roberta Cerasi Urban a , Michele Lima-Souza b , Letícia Caetano-Silva b , Maria Eugênia C. Queiroz a , Raquel F.P. Nogueira b , Andrew G. Allen b , Arnaldo A. Cardoso b , Gerhard Held c , Maria Lucia A.M. Campos a, * a Departamento de Química, Faculdade de Filosoﬁa, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo,14040-901 Ribeirão Preto, SP, Brazil b UNESP-Universidade Estadual Paulista, Instituto de Química, 14800-900 Araraquara, SP, Brazil c UNESP-Universidade Estadual Paulista, Instituto de Pesquisas Meteorológicas, 17048-699 Bauru, SP, Brazil highlights < The aerosol chemical composition was highly affected by biomass burning. < Most of the levoglucosan (up to 89%) was present in small particles (<1.5 mm). < Biomass burning was an important source of WSOC. < The levoglucosan:K þ ratio in ﬁne particles (sugar-cane burning) was 0.24. article info Article history: Received 3 April 2012 Received in revised form 5 July 2012 Accepted 31 July 2012 Keywords: Brazil São Paulo State Sugar cane Cloud condensation nuclei Organic carbon abstract Three chemical species related to biomass burning, levoglucosan, potassium and water-soluble organic carbon (WSOC), were measured in aerosol samples collected in a rural area on the outskirts of the municipality of Ourinhos (São Paulo State, Brazil). This region is representative of the rural interior of the State, where the economy is based on agro-industrial production, and the most important crop is sugar cane. The manual harvesting process requires that the cane be ﬁrst burned to remove excess foliage, leading to large emissions of particulate materials to the atmosphere. Most of the levoglucosan (68e89%) was present in small particles (<1.5 mm), and its concentration in total aerosol ranged from 25 to 1186 ng m 3 . The highest values were found at night, when most of the biomass burning occurs. In contrast, WSOC showed no diurnal pattern, with an average concentration of 5.38  2.97 mgm 3 (n ¼ 27). A signiﬁcant linear correlation between levoglucosan and WSOC (r ¼ 0.54; n ¼ 26; p < 0.0001) conﬁrmed that biomass burning was in fact an important source of WSOC in the study region. A moderate (but signiﬁcant) linear correlation between levoglucosan and potassium concentrations (r ¼ 0.62; n ¼ 40; p < 0.0001) was indicative of the inﬂuence of other sources of potassium in the study region, such as soil resuspension and fertilizers. When only the ﬁne particles (<1.5 mm; typical of biomass burning) were considered, the linear coefﬁcient increased to 0.91 (n ¼ 9). In this case, the average levoglucosan/K þ ratio was 0.24, which may be typical of biomass burning in the study region. This ratio is about 5 times lower than that previously found for Amazon aerosol collected during the day, when ﬂaming combustion prevails. This suggests that the levoglucosan/K þ ratio may be especially helpful for characterization of the type of vegetation burned (such as crops or forest), when biomass-burning is the dominant source of potassium. The relatively high concentrations of WSOC (and inorganic ions) suggest an important inﬂuence on the formation of cloud condensation nuclei, which is likely to affect cloud formation and precipitation patterns. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Biomass burning introduces high loads of particulate matter and gases to the atmosphere, which inﬂuences cloud formation, radi- ation balance, ozone formation and, ultimately, human health and * Corresponding author. Tel.: þ55 16 36024368; fax: þ55 16 36024838. E-mail address: lcampos@ffclrp.usp.br (M.L.A.M. Campos). Contents lists available at SciVerse ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.atmosenv.2012.07.082 Atmospheric Environment 61 (2012) 562e569