1. Rainwater chemistry in the Amazon Basin Rainwater chemistry in the Amazon Basin Eduardo T. Fernandes1, Paulo Artaxo 1, Dayse Magalhães A. de M. Figueiredo 2, Norbert Miekeley 3, Maria S.K. Souza1, Beatriz Machado Gomes 4 1 Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, São Paulo, SP, CEP 05315-900, Brazil. 2 Laboratório de Limnologia, UHE, Balbina 3 Departamento de Química, Pontifícia Universidade Católica do Rio de Janeiro, Rio de Janeiro, Brazil. 4 UNIR - Universidade Federal de Rondônia, Ji-paraná, Brazil. Figure 2 – Comparison between ICP-MS and ion chromatography result for Na in Balbina. Figure 1 – Comparison between ICP-MS and ion chromatography result for Mg in Balbina. Figure 5 – Comparison of the some Trace elements obtained from this work with literature. Figure 4 - Comparison of the ion chromatography results from this work with literature. Figure 3 – Comparison of pH concentration from this work with the literature. Conclusions The preliminary results for the ionic and elemental concentrations from ion chromatography and ICP- MS analyses show good agreement, besides IC measures the soluble fraction and ICP-MS the total elemental concentration, indicating that Na and Mg are present in rainwater as ionic compounds. The comparison of the measured concentrations with literature data shows remarkably similar concentrations. For the ICP-MS measurements, the concentrations in Africa presented much larger values than in the Amazon, probably due to the distinct vegetation and therefore distinct biogenic emission, as well as possible biomass burning impact in Africa, even in the wet season. It was not possible to measure phosphorus or phosphate at the present work. This indicates that the concentration of this element is very low in the atmosphere. Results This work presents data from wet season collected at Alta Floresta (long-term monitoring), Balbina (intensive campaign: LBA/CLAIRE with label BAC1 and BAC2 and long-term monitoring with label Balbina) and Rondônia (intensive campaign: LBA/AMC/TRMM). In table 1, the average elemental concentration values, standard deviation and number of the samples collected at Rondônia and Balbina are presented. The results were obtained by ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis. The label BAC1 and BAC2 distinguish the different sampling sites. The first site was located at the airport and other was located near the Limnology laboratory, about 12 km far from the first. In table 2, average ion concentration values, standard deviation and number of samples from Rondônia, Balbina and Alta Floresta by ion chromatography (IC) analysis are presented. Comparisons between concentrations measured by ICP-MS and ion chromatography for Mg and Na are presented in figures 1 and 2, respectively for Balbina site. The correlation coefficient (r 2 ) between ICP-MS and IC for both elements is larger than 0.9. Similar correlations were observed at the other sites. In figure 3, comparisons of the pH values from this work and values from other studies are presented: Williams et al. (1997) and Freydier et al (1998). In Williams et al., the samples were collected at Lake Calado (3 o 15’S, 60 o.34’W), approximately 80 km West of Manaus, in campaigns during the wet season. In Freydier et al., the samples were collected at Lamto (Ivory Coast) and Kollo (Niger), Africa, savanna vegetation regions. In general, pH values are very closer around 5.0. In figure 4, ion chromatography results from this work are compared with results from the literature. In general, average concentration are closer. In figure 5 ICP-MS results from this work are compared with results obtained by Freydier (1998) et al. Observed concentration values for Africa are frequently higher than from this work. That discrepancy may be due to the different type of vegetation. Introduction Rainwater elemental composition was studied at four different locations in the Amazon Basin during the wet and dry seasons. Three intensive field campaigns were carried out during the wet season: the LBA/CLAIRE during March and April of 1998, in Balbina, Amazonas state, the LBA/AMC/TRMM during January to March of 1999, in Ouro Preto do Oeste, Rondônia, and Santarém wet season in Santarém, Pará, during January to March of 2000. One intensive field campaign was carried out during the dry season in Rondônia. Rainwater samples were also collected in a long-term atmospheric monitoring at two sites located in Balbina and Alta Floresta. Balbina and Santarém are located in a region of undisturbed primary rain forest. Vegetation is dominated by grassland and pasture, with some primary rain forest areas at Ouro Preto do Oeste and Alta Floresta is located in a transition zone between cerrado vegetation and primary rain forest, with very significant deforestation in the region.