Trace Metal Enrichments in Water of the Okavango Delta (Botswana): Hydrological Consequences

The Okavango Delta in northern Botswana is an endorheic ecosystem formed by 150,000 islands surrounded a flood plain. vegetation of these displays external tree ring enclosing barren interior domain with evaporitic deposits. We sampled the groundwater into piezometers across island at southwest Delta, and drilled sediments. geochemical analysis water exhibits two different compositions: fresh floodplain saline part. These inner samples display enrichments heavy metals, metalloids critical metals such as, Rare Earth Elements (REE). latest show continuous enrichment from LREE to HREE positive Ce Eu anomalies, associated alkaline pH. Overall, types displayed REE patterns fingerprint sources. geochemistry sediments indicates same composition whatever sample location no traces deposits was found. variations table depth shows hydrological behaviors between zone which does not follow cycle. Thus, we document aquifers independent behaviors: surface fresh-water aquifer connected channels, confined below islands. contrasted waters explains distribution survives through access water. architecture this southwestern differs other islands, highlighting complexity Delta.