Mapping Soil Salinity: A Case Study from Marajó Island, Brazilian Amazonia

Remote sensing is a way to identify global surface salinity environments and its chemical and physical aspects. The study area was Marajó Island, a great archipelago situated in the Amazon River mouth, Brazil. This fluvio-marine ecosystem has extensive areas of saline-sodic plains. The aim of the study is the applicability of spectral indices to recognize the eastern Marajó Island salt-plains using Sentinel-2 and landscape soil analysis. This work was developed in three main stages: (i) fieldwork for soil sampling and environment recognition; (ii) laboratory procedures for obtaining the surface electrical conductivity (Ec); and (iii) use of Sentinel-2 satellite images for obtained the salt environment data and its spectral information. As result, the salinity indices applied were satisfactory to recognize regional zones with salt-affected soils. The eastern Marajó Island (lowlands) revealed a variable environment geodiversity, with potential to be better known the Holocene landscape evolution, along with predictions for the coming decades of climate change projections using the salt-plains as main environment guide. The salt-affect soils in the eastern of Marajó Island can be indicative of regional marine incursion, tidal effects, the rainfall accumulation over the years, groundwater, tectonic processes, evapotranspiration dynamic, and the sea-level rise projections. This study evidenced the high potential of remote sensing in recognize saline-sodic areas in Brazil, especially in a complex fluvio-marine ecosystem such as the Marajó archipelago in contribution to the PronaSolos Brazil Soil Project.