A motivating question for this project is how the cycling of calcium between vegetation, soil and waters responds to ecosystem disturbance, particularly harvesting of biomass. To address this, we've developed stable isotopes of calcium (⁴⁴Ca/⁴⁰Ca) as a tracer of Ca in streamwater. Plants discriminate slightly against the heavy isotope of calcium during root uptake, producing isotopically distinct Ca pools. We can then use these isotopically distinct Ca pools to determine where streamwater Ca originated.

Measurement of natural variations in calcium isotope ratios is analytically challenging primarily because the total range in ⁴⁴Ca/⁴⁰Ca is small relative to other stable isotope systems. We've developed procedures in the BU TIMS Facility, based on the established double-spike method, that allow us to confidently determine small variations in natural abundance ratios of calcium isotopes. This project is being carried out under the supervision of my advisor Dr. Andrew Kurtz.