Hydrochemical Profiles of a Pacific Island Groundwater Seawater Mixing Zone

Nauru Island's karst aquifer features a thick brackish water mixing zone where salinity increases gradationally to seawater at about 70 meters below sea level. Groundwater chemistry evolves from HCO3-Ca-Mg type to seawater, with saturation indices for carbonate minerals like dolomite and calcite increasing with salinity. This dataset from the Australian Ocean Data Network, last updated in April 2026, documents these chemical transitions.

Use Cases

• Modeling the relationship between total dissolved solids (TDS) concentration and mineral saturation indices for dolomite, calcite, and aragonite.
• Analyzing chemical evolution trends (open vs. closed system) based on partial pressure of CO2 data across the freshwater layer and saline mixing zone.
• Characterizing the gradational increase in groundwater salinity with depth, up to the seawater interface at approximately 70 meters below sea level.

Strengths

• Data characterizes a complete salinity gradient from freshwater to seawater in a karst island setting.
• Analysis includes specific saturation index thresholds for key carbonate minerals (e.g., dolomite at 300 mg/L TDS).

Limitations

• Specific sample size, row count, and column details are unknown.
• Data is presented in PDF/HTML formats, which may complicate direct quantitative analysis.
• Geographic scope is limited to a single island (Nauru).

Provenance

Source

Australian Ocean Data Network

Collection Method

Field measurements and hydrochemical analysis of groundwater samples.

Freshness

Last updated in April 2026.

Geography

Nauru Island, central Pacific Ocean.