Characterization of Gorleben groundwater colloids by atomic force microscopy.

Area of Science:

• Environmental Science
• Geochemistry
• Colloid Science

Background:

• Groundwater colloids play a crucial role in contaminant transport.
• Understanding the structure and composition of these colloids is essential for predicting contaminant migration.
• The Gorleben site in Germany is a key area for studying groundwater behavior.

Purpose of the Study:

• To characterize groundwater colloids from the Gorleben site using advanced microscopy techniques.
• To investigate the native hydrated state of aquatic colloids and their aggregates.
• To assess the potential influence of colloid structure on contaminant migration processes.

Main Methods:

• Tapping-mode atomic force microscopy (AFM) with phase contrast imaging was employed.
• Investigations were conducted using a liquid cell to maintain samples in their native hydrated state.
• Eu(III) was used as a probe in the presence of groundwater colloids.

Main Results:

• AFM revealed a diverse range of colloid structures, including spherical particles, fibrous aggregates, and hollow formations.
• Phase contrast imaging suggested partial coating of clay particle edges by humic colloids.
• The characterized colloids represent a complex mixture of components within the Gorleben groundwater.

Conclusions:

• Groundwater colloids at the Gorleben site exhibit complex and varied structures.
• The presence of humic and clay colloids, along with their aggregation patterns, is significant.
• These complex colloid mixtures likely influence various processes governing groundwater contaminant migration.