Abstract. We present the development and assessment of a new flight system that uses acommercially available continuous-wave, tunable infrared laser directabsorption spectrometer to measure N2O, CO2, CO, andH2O. When the commercial system is operated in an off-the-shelfmanner, we find a clear cabin pressure–altitude dependency forN2O, CO2, and CO. The characteristics of this artifactmake it difficult to reconcile with conventional calibration methods. Wepresent a novel procedure that extends upon traditional calibrationapproaches in a high-flow system with high-frequency, short-duration samplingof a known calibration gas of near-ambient concentration. This approachcorrects for cabin pressure dependency as well as other sources of drift inthe analyzer while maintaining a ∼90% duty cycle for 1Hz sampling.Assessment and validation of the flight system with both extensive in-flightcalibrations and comparisons with other flight-proven sensors demonstrate thevalidity of this method. In-flight 1σ precision is estimated at0.05ppb, 0.10ppm, 1.00ppb, and 10ppm for N2O,CO2, CO, and H2O respectively, and traceability to WorldMeteorological Organization (WMO) standards (1σ) is 0.28ppb,0.33ppm, and 1.92ppb for N2O, CO2, and CO. We showthe system is capable of precise, accurate 1Hz airborne observations ofN2O, CO2, CO, and H2O and highlight flightdata, illustrating the value of this analyzer for studying N2Oemissions on ∼100km spatial scales.
Abstract. Marine phytoplankton such as bloom-forming, calcite-producingcoccolithophores, are naturally exposed to solar ultraviolet radiation (UVR,280–400nm) in the ocean's upper mixed layers. Nevertheless, the effects ofincreasing carbon dioxide (CO2)-induced ocean acidification and warming have rarelybeen investigated in the presence of UVR. We examined calcification andphotosynthetic carbon fixation performance in the most cosmopolitancoccolithophorid, Emiliania huxleyi, grown under high(1000µatm, HC; pHT: 7.70) and low (400µatm,LC; pHT: 8.02) CO2 levels, at 15∘C,20∘C and 24∘C with or without UVR. The HCtreatment did not affect photosynthetic carbon fixation at 15∘C,but significantly enhanced it with increasing temperature. Exposure to UVRinhibited photosynthesis, with higher inhibition by UVA (320–395nm) thanUVB (295–320nm), except in the HC and 24∘C-grown cells, in whichUVB caused more inhibition than UVA. A reduced thickness of the coccolith layerin the HC-grown cells appeared to be responsible for the UV-inducedinhibition, and an increased repair rate of UVA-derived damage in theHC–high-temperature grown cells could be responsible for lowered UVA-induced inhibition.While calcification was reduced with elevated CO2 concentration,exposure to UVB or UVA affected the process differentially, with the formerinhibiting it and the latter enhancing it. UVA-induced stimulation of calcification washigher in the HC-grown cells at 15 and 20∘C, whereas at24∘C observed enhancement was not significant. The calcificationto photosynthesis ratio (Cal∕Pho ratio) was lower in the HC treatment,and increasing temperature also lowered the value. However, at 20 and24∘C, exposure to UVR significantly increased the Cal∕Phoratio, especially in HC-grown cells, by up to 100%. This implies thatUVR can counteract the negative effects of the “greenhouse” treatment onthe Cal∕Pho ratio; hence, UVR may be a key stressor when considering theimpacts of future greenhouse conditions on E. huxleyi.
more » « less- NSF-PAR ID:
- 10113602
- Date Published:
- Journal Name:
- Biogeosciences
- Volume:
- 16
- Issue:
- 2
- ISSN:
- 1726-4189
- Page Range / eLocation ID:
- 561 to 572
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/bg-16-561-2019
