Rainfall chemistry composition in two ecosystems in the northeastern Brazilian Amazon (Amapa State)

The rainfall chemical composition in two Amazonian ecosystems, a "terra fir me" forest (dense tropical rain forest) and the "cerrado" (savanna) are pre sented. Both areas are located in the northeast Brazilian Amazon (Amapa Sta te). This study evaluated the statistical differences in the rainfall chemi stry, as well as the deposition through rainfall, for each ecosystem. The c hemical species evaluated in the rainwater were Na+, K+, Mg2+, Ca2+, NH4+, Cl-, NO3-, SO42-, Fe3+, Al3+, Zn2+, and Mn2+ for both ecosystems. Factor an alysis for the terra fume ecosystem indicated that there is a significant d ifference between the dry and wet periods in the rainfall chemical composit ion, indicating a biomass-burning signature (K+ in association with Zn2+. H igh deposition of solutes, except for Mn2+ and Cl+, was also observed durin g the dry period. Comparison between the terra fume and cerrado rainfall ch emistry showed statistical differences in concentration for the marine spec ies (Nac and CU and for the soil dust species (Al3+, Fe3+, and Mn2+. The se a-salt and biogenic sources of chemical species in terra fume forest rainwa ter are equally important. The site nearer to the sea (cerrado) has rainfal l chemistry dominated by species having marine origins. The terra firme for est also has rainfall chemistry dominated by marine origin species, althoug h the biogenic and soil dust origin species are highly significant at this site. Also in the terra firme a biomass-burning signature was observed. The amount of sea salt deposited was more than 50% larger in the cerrado owing to its proximity to the shore.