A new multisource and high-frequency approach to measuring δ2H and δ18O in hydrological field studies

Measurements of delta H-2 and delta O-18 in isotope-based field studies have fundamentally improved our understanding of water flow and transport time scales in soils and headwater catchments. Until recently, however, technical constraints have limited the temporal resolution at which water samples could be collected and analyzed. We introduce a new sample acquisition systemconsisting of a four-channel peristaltic pump, custom flow manifold, and CTC LCPAL auto-samplerthat is paired with a field-deployable laser spectrometer (LGR LWIA). Our system enables high-frequency (subhourly) measurement of delta H-2 and delta O-18 in as many as four water sources. We deployed the system at a field site in Corvallis, OR, USA, where we measured the delta H-2 and delta O-18 composition of precipitation and the drainage from two lysimeters. The system produced delta H-2 and delta O-18 time series for precipitation and drainage from each lysimeter at a temporal frequency of one sample every 34 min, which, on average, corresponded to 0.84, 0.63, and 0.48 mm of precipitation or lysimeter drainage per sample. The high-frequency data showed substantially greater short-term variability than observed when sampling at successively longer time intervals. The system and sampling configuration are versatile and can be adapted to sample multiple water flows at variable frequencies depending on the characteristic transit times of each source.