Advancing laser ablation ICP-MS techniques to analyse novel biogeochemical weathering archives and study plant nutrient cycles

This research is funded by the Swiss National Science Foundation (project no. P2EZP2_168836).

To distinguish abiotic from biotic processes in the Critical Zone- the narrow zone between unweathered bedrock and the top of the vegetation, novel metal stable isotope tracers are employed by geochemists. Two frequently used tracers for silicate weathering are Silicon stable isotope ratios and Germanium/Silicon ratios. In soil and river water, opposing trends in these ratios are generated by abiotic weathering and biotic uptake, respectively. However, not all compartments in the Critical Zone are easily probed; especially (soil)-water is not preserved over weathering time scales. Here, phytoliths (plant silica deposits) could act as an archive from which the past water composition can be inferred, provided the associated fractionation factors and mechanisms are known.

In this research project D. Frick will establish a novel method to analyse single phytoliths (biogenic silica) for their stable metal isotopic and elemental composition, as currently available methods are not suitable. To achieve this goal, I will develop an analytical routine, using state-of-the-art femtosecond-Laser Ablation Split Stream Inductively Coupled Plasma Mass Spectrometry (fs-LASS-ICP-MS), to determine in situ the stable metal isotope ratios (using a multicollector ICP-MS) and elemental composition (using a quadrupole ICP-MS) of individual phytoliths simultaneously.

The chemical and isotopic characteristic of individual phytoliths discloses intrinsic information on the environmental conditions under which the plant host grew. With this newly developed routine, not only geological record of past soil environments can be accessed, but also the uptake and redistribution of Silicon and the formation of phytoliths can be studied.

Phytoliths and the isotopic composition of a single specimen
Daniel Frick
Dr. Daniel Frick
Earth Surface Geochemistry
Building E, Room 227
14473 Potsdam
+49 331 288-28963