Journal of Radioanalytical and Nuclear Chemistry, Vol. 270, No.1 (2006) 69–73 0236–5731/USD 20.00 Akadémiai Kiadó, Budapest © 2006 Akadémiai Kiadó, Budapest Springer, Dordrecht Surface contamination effects on leaf chemical composition in the Atlantic Forest A. A. Ferrari,* E. J. França, E. A. N. Fernandes, M. A. Bacchi Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, PO Box 96, 13400-970 Piracicaba SP, Brazil (Received April 6, 2006) The exogenous material that adheres to the leaf surface affects the elemental composition of the plant itself, thereby constituting one of the major error sources in plant analysis. The present work investigated the surface contamination of leaves from the Atlantic Forest. Instrumental neutron activation analysis (INAA) was applied to assess the efficiency of leaf EDTA-washing. Chemical element concentrations were corrected using Sc (soil tracer) since resuspended soil is the main source of contamination in leaves. As a result, EDTA-washing should be used mainly for the evaluation of terrigenous elements, while the Sc-corrected concentrations are considered satisfactory for the other elements. Introduction The concentration of chemical elements in leaves is affected by the presence of exogenous material, which usually causes elevated element content over the analyzed material. 1 Such alteration is identified as a source of error in plant analysis 2 and, consequently, results in studies of mineral metabolism, plant nutrition and physiology may be biased by these elevated concentration values. The same is also true in biomonitoring studies, in which, however, values for exogenous materials are of interest. Considering the fact that some anthropogenic effects can be slightly apparent in the Atlantic Forest, Parque Estadual Carlos Botelho (PECB) was chosen for the installation of a long-term plot in the context of the Biota Program (“Diversity, Dynamics and Conservation in the São Paulo State Forests: 40 ha of Permanent Parcels”) supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). About 10,000 trees were mapped in a plot of 0.1 km 2 (10 ha) and 200 plant species were recognized. In this case the most abundant species in the ecosystem were analyzed and diverse kinds of materials, including leaves, were taken into account. The problem in the study of the surface contamination of leaves becomes quite complex since the degree of enrichment of chemical concentrations depends on the inherent morphological characteristics of each leaf that is to be evaluated. The concentration of chemical elements, such as Fe, Hf and Sc are usually found to be high (up to 20%) in tropical ecosystems due to the presence of soil particles adhered to the surface of leaves. 3 Although different chemical elements can be used for the evaluation of soil surface contamination, scandium is quite applicable, 4–6 because of its accuracy in low level determination by means of INAA as well as the low content in plant which usually do not exceed 0.008 mg . kg –1 . 7 * E-mail: aferrari@cena.usp.br The present work aims to evaluate the surface contamination of leaves from the PECB long-term plot through instrumental neutron activation analysis (INAA) for the determination of chemical elements. Due to its metal complexation characteristic and easy availability, EDTA was used to wash some leaves, while other groups of leaves were washed with tap water to allow the comparison between the chemical concentrations from both washing procedures to be utilized. Moreover, a better understanding of Sc behavior in plants could be assessed by comparing the concentrations of this element in leaves washed by EDTA from the Atlantic Forest. Experimental Figure 1 presents the PECB long-term plot sub- divided into 256 sub-plots of 200 m 2 . Leaves from different species were collected in April, 2003 and July, 2004 (Table 1). For each species, 4 different individuals were taken resulting in a total of 84 samples. The leaves were washed with tap water (treatment 1) and with a 0.01M EDTA solution followed by bi-distilled water (treatment 2). Moreover, leaves were separately oven- dried at 60 °C until constant weight followed by particle reduction (size <0.5 mm) in a titanium rotor mill to avoid cross contamination. Test portions of approximately 250 mg of leaves were transferred to high purity polyethylene capsules (Vrije Universiteit, Amsterdam, The Netherlands) specifically designed for irradiation with neutrons. In order to evaluate the analytical quality, test portions of 200 mg of certified reference materials (IAEA 336 Lichen and INCT-TL-1 Tea Leaves) were analyzed together with the samples. Ni–Cr alloys with well- known composition 8 was employed for thermal neutron flux monitoring during irradiation.