Cadmium in groundwater - A synopsis based on a large hydrogeochemical data set

Area of Science:

• Environmental Science
• Hydrogeology
• Geochemistry

Background:

• Elevated cadmium (Cd) concentrations in groundwater pose risks to water supply and agriculture.
• While Cd aqueous chemistry is simple, hydrogeochemical interactions significantly influence its mobility, especially beyond industrial pollution.
• Understanding these interactions is crucial for managing groundwater quality.

Purpose of the Study:

• To investigate the behavior and mobility of cadmium in groundwater.
• To identify key hydrogeochemical parameters controlling Cd concentrations.
• To analyze the influence of natural and anthropogenic factors on Cd levels in Northern German groundwater.

Main Methods:

• Statistical analysis of a large hydrogeochemical dataset (6300 sampling locations).
• Correlation of Cd concentrations with groundwater conditions, including pH, redox potential, and nitrate levels.
• Assessment of geogenic and anthropogenic Cd input sources.

Main Results:

• Cadmium concentrations above 0.5 μg/L were linked to groundwater conditions influenced by woodlands (acidification) and farmland (nitrate enrichment).
• Geogenic and anthropogenic Cd inputs were less significant drivers of elevated concentrations.
• Oxic conditions and autotrophic nitrate reduction were primary factors for elevated Cd.
• pH and redox potential were key hydrogeochemical parameters affecting Cd mobility, likely through sorption and release mechanisms.
• Enhanced groundwater recharge and limited aquifer retention capacity exacerbated high Cd levels.

Conclusions:

• Groundwater cadmium levels are primarily controlled by natural hydrogeochemical processes, particularly under oxic and nitrate-rich conditions.
• Acidification in wooded areas and nitrate from fertilizers significantly increase Cd mobility.
• Effective management of groundwater quality requires addressing these specific hydrogeochemical factors to prevent regulatory breaches.