LAUSR

Abstract We outline the methodology for detection of carbon dioxide (CO 2 ) leaks to the atmosphere from carbon capture and storage (CCS) using measurements of radiocarbon in CO 2 . The radiocarbon method can unambiguously identify recently added fossil-derived CO 2 such as CCS leaks due to the very large isotopic difference between radiocarbon-free fossil derived CO 2 and natural CO 2 sources with ambient radiocarbon levels. The detection threshold of 1 ppm of fossil-derived CO 2 is comparable to other proposed atmospheric detection methods for CCS leakage. We demonstrate that this method will allow detection of a 1000 ton C yr −1 leak 200–300 m from the source during the day and more than 600 m away at night. Using time-integrated sampling techniques, long time periods can be covered with few measurements, making the method feasible with existing laboratory-based radiocarbon measurement methods We examine the method using previously published observations and new model simulations for a case study in Taranaki, New Zealand. Plant material faithfully records the radiocarbon content of assimilated CO 2 and we show that short-lived grass leaves and cellulose from tree rings provide effective time-integrated collection methods, allowing dense spatial sampling at low cost. A CO 2 absorption sampler allows collection at controlled times, including nighttime, and gives similar results.