A closed‐loop system for the semi‐continuous measurement of biogenic volatile organic compounds from marine organisms

The marine environment constitutes a significant source of Biogenic Volatile Organic Compounds (BVOCs) to the atmosphere with impacts on ecosystem functioning, atmospheric particle formation, carbon cycling and climate. However, processes governing BVOC emissions remain largely unconstrained due to their large spatial and temporal variability. Here, we describe a closed‐loop measurement system that couples a Proton Transfer Reaction Time‐of‐Flight Mass Spectrometer (PTR‐ToF‐MS) to gas‐tight chambers which allows for the real‐time semi‐continuous detection of BVOCs emitted by marine organisms under different experimental treatments. We tested our system for adsorptive losses, reproducibility, linearity and accuracy with four BVOCs (dimethyl sulfide (DMS), methanethiol (MeSH), isoprene and α ‐pinene) at concentrations relevant in the marine environment. While all compounds demonstrated linearity ( R 2 ≥ 0.970) between the dissolved and gas phase, the regressions were statistically significant for DMS and MeSH. A direct relationship between compound recovery and compound solubility was observed, with the low solubility compounds isoprene and α ‐pinene demonstrating poor recovery and the higher solubility compounds DMS and MeSH exhibiting greater recovery. The closed‐loop system demonstrated minor compound loss (< 7%) throughout and high reproducibility (> 88.5%). A sampling time of 605 s was determined to be sufficient for signal stabilization of the four target BVOCs during headspace sampling/measurements. The development of this system provides a novel approach for assessing key drivers of BVOC emissions with broad applicability to both marine and freshwater systems.