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  • Evaluating Precipitation Amount and Water Isotope Ratios in the OPEnS and Palmex RS1 Passive Collectors: Implications for High‐Frequency Precipitation Sampling
Title: Evaluating Precipitation Amount and Water Isotope Ratios in the OPEnS and Palmex RS1 Passive Collectors: Implications for High‐Frequency Precipitation Sampling
ABSTRACT For decades, precipitation passive collectors for water stable isotopes (δ2H, δ18O andd‐excess) analysis have been debated regarding secondary fractionation, sample integrity over time and sampling costs. This study compares the performance of precipitation (N = 36 events) passive collectors for water isotope analysis in the Dallas‐Fort Worth Metroplex (north‐central Texas, USA). Three systems were compared: (1) the low‐cost OPEnS collector (version 3.0), (2) the Palmex RS1 collector alone and (3) the Palmex RS1 collector combined with a portable autosampler for sub‐daily sampling. Our results showed no significant variation in the annual arithmetic mean between OPEnS and the other sampling systems. Statistical evaluations between the OPEnS and Palmex RS1 and Palmex‐autosampler yieldedpvalues of 0.545 and 0.921 for δ18O, 0.789 and 0.886 for δ2H and 0.410 and 0.937 ford‐excess, respectively. The annual precipitation weighted means of δ18O, δ2H andd‐excess were −4.25‰ ± 1.94‰, −21.2‰ ± 15.1‰ and 12.8‰ ± 7.1‰ for the OPEnS collector; −3.59‰ ± 1.59‰, −18.5‰ ± 13.7‰ and 10.2‰ ± 5.4‰ for the Palmex RS1; and −4.69‰ ± 2.36‰, −23.4‰ ± 16.7‰ and 14.1‰ ± 7.6‰ for the Palmex‐autosampler setup. Strong linear correlations were observed between OPEnS and both Palmex RS1 (δ18O:r2 = 0.97, δ2H:r2 = 0.98 andd‐excess:r2 = 0.97) and Palmex‐autosampler (δ18O:r2 = 0.87 and δ2H:r2 = 0.93), while the correlation ford‐excess was weaker (r2 = 0.72) with the autosampler setup. The best agreement in precipitation amounts was found between OPEnS and Palmex RS1 (r2 = 0.91). Combining the Palmex with an autosampler resulted in a lower precipitation amount performance (r2 = 0.59). Precipitation amount discrepancies may occur because of (i) the vertical instability in the OPEnS collector during windy and heavy rainfall conditions, and (ii) the Palmex‐autosampler mechanical challenges related to ponding or residual water in the connecting vinyl tubing and distributor's arm movement across the 24‐bottle carousel. Meteoric water lines suggest a larger influence of secondary evaporation when using the Palmex‐autosampler setup (δ2H = 6.55 × δ18O + 5.36;r2 = 0.84) compared to the OPEnS collector (δ2H = 7.33 × δ18O + 8.87;r2 = 0.84) and Palmex RS1 (δ2H = 7.56 × δ18O + 8.52;r2 = 0.85). The OPEnS collector is a consistent, cost‐effective and reliable alternative for precipitation sampling that is similar to the Palmex RS1 collector. Autosampler assemblages to Palmex RS1 or other in‐house collectors should be carefully tested and revised regarding precipitation amounts and post‐sampling evaporation.  more » « less
Award ID(s):
2243963 2243964
PAR ID:
10695662
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
Wiley
Date Published:
Journal Name:
Hydrological Processes
Volume:
39
Issue:
7
ISSN:
0885-6087
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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