Carbon Flux Explorer optical assessment of C, N and P fluxes

Abstract. The magnitude and controls of particulate carbon exported from surface watersand its remineralization at depth are poorly constrained. The Carbon FluxExplorer (CFE), a Lagrangian float-deployed imaging sediment trap, has beendesigned to optically measure the hourly variations of particle flux tokilometer depths for months to seasons while relaying data in near-real timeto shore via satellite without attending ships. The main optical proxy forparticle load recorded by the CFE, volume attenuance (VA; units ofmATN&thinsp;cm2), while rigorously defined and highly precise, has not beenrobustly calibrated in terms of particulate organic carbon (POC), nitrogen(PN) and phosphorus (PP). In this study, a novel 3-D-printed particle samplerusing cutting edge additive manufacturing was developed and integrated withthe CFE. Two such modified floats (CFE-Cals) were deployed a total of15 times for 18–24&thinsp;h periods to gain calibration imagery and samples atdepths near 150&thinsp;m in four contrasting productivity environments during theJune 2017 California Current Ecosystem Long-Term Ecological Research (LTER)process study. Regression slopes for VA&thinsp;:&thinsp;POC and VA&thinsp;:&thinsp;PN (unitsmATN&thinsp;cm2:&thinsp;mmol; R2, n, p value in parentheses) were1.01×104 (0.86, 12, &lt;&thinsp;0.001) and 1.01×105(0.86, 15, &lt;&thinsp;0.001), respectively, and were not sensitive toparticle size classes or the contrasting environments encountered. PP was notwell correlated with VA, reflecting the high lability more »

Authors:
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Award ID(s):
Publication Date:
NSF-PAR ID:
10092134
Journal Name:
Biogeosciences
Volume:
16
Issue:
6
Page Range or eLocation-ID:
1249 to 1264
ISSN:
1726-4189
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4. Abstract. Chemical ionization massspectrometry (CIMS) instruments routinely detect hundreds of oxidized organic compoundsin the atmosphere. A major limitation of these instruments is the uncertaintyin their sensitivity to many of the detected ions. We describe thedevelopment of a new high-resolution time-of-flight chemical ionization massspectrometer that operates in one of two ionization modes: using eitherammonium ion ligand-switching reactions such as for ${\mathrm{NH}}_{\mathrm{4}}^{+}$ CIMS orproton transfer reactions such as for proton-transfer-reaction massspectrometer (PTR-MS). Switching between the modes can be done within 2&thinsp;min.The ${\mathrm{NH}}_{\mathrm{4}}^{+}$ CIMS mode of the new instrument has sensitivities of upto 67&thinsp;000&thinsp;dcps&thinsp;ppbv−1 (duty-cycle-corrected ion counts per second perpart per billion by volume) and detection limits between 1 and 60&thinsp;pptv at2σ for a 1&thinsp;s integration time for numerous oxygenated volatileorganic compounds. We present a mass spectrometric voltage scanning procedurebased on collision-induced dissociation that allows us to determine thestability of ammonium-organic ions detected by the ${\mathrm{NH}}_{\mathrm{4}}^{+}$more » CIMS instrument.Using this procedure, we can effectively constrain the sensitivity of theammonia chemical ionization mass spectrometer to a wide range of detectedoxidized volatile organic compounds for which no calibration standards exist.We demonstrate the application of this procedure by quantifying thecomposition of secondary organic aerosols in a series of laboratoryexperiments.