M. Koike

Performance of an aircraft instrument for the measurement of NO y

Measurements of NO and NOy using a chemiluminescence technique were made on board a DC-8 aircraft during NASAs Pacific Exploratory Mission-West B (PEM-West B). The gold converter to convert NOy species into NO was operated at a constant pressure using a servo-controlled Teflon valve, which has been used for NOy measurements on board the ER-2 aircraft. The results of laboratory tests and some flight data during PEM-West B are presented. These experiments indicate no detectable inlet loss of HNO3 in dry air, although some loss was observed at H2O mixing ratios of 1–2%. The laboratory tests also showed small variability in the NOy artifact, high conversion efficiency for NO2 and HNO3, low HCN conversion efficiency, good repeatability of the measurements, and fast response. The control of the converter pressure during flight has been proven to be very advantageous in making reliable aircraft NOy measurements in the troposphere. The uncertainties of the NO and NOy PEM-West B data, including the effects of HCN conversion and HNO3 inlet loss, have been estimated.

In situ HNO3 to NOy instrument comparison during SOLVE

Measurements of HNO 3 mixing ratios from the chemical ionization mass spectrometer have been critically compared with simultaneous measurements of total gas phase NO y from the NO chemiluminescence detector aboard the NASA DC-8 aircraft during the SAGE 3 Ozone Loss and Validation Experiment (SOLVE). The data were obtained in the arctic upper troposphere and lower stratosphere in the winter of 1999-2000. A brief comparison to the NOy instrument aboard the NASA ER-2 is also presented. The time responses, detection limits, relative precision, and stability of relative calibrations for the instruments were in excellent agreement throughout the mission. However, the average slope of the HNO 3 to NO y correlation was 1.13 ± 0.03 overall and 1.06 ± 0.03 in stratospheric air, indicating that the two measurements had a systematic calibration offset. Possible sources for the offset error are presented, and methods to reduce the calibration error in future flights are suggested.

Early trace of life from 3.95 Ga sedimentary rocks in Labrador, Canada

The vestiges of life in Eoarchean rocks have the potential to elucidate the origin of life. However, gathering evidence from many terrains is not always possible, and biogenic graphite has thus far been found only in the 3.7–3.8 Ga (gigayears ago) Isua supracrustal belt. Here we present the total organic carbon contents and carbon isotope values of graphite (δ13Corg) and carbonate (δ13Ccarb) in the oldest metasedimentary rocks from northern Labrador. Some pelitic rocks have low δ13Corg values of −28.2, comparable to the lowest value in younger rocks. The consistency between crystallization temperatures of the graphite and metamorphic temperature of the host rocks establishes that the graphite does not originate from later contamination. A clear correlation between the δ13Corg values and metamorphic grade indicates that variations in the δ13Corg values are due to metamorphism, and that the pre-metamorphic value was lower than the minimum value. We concluded that the large fractionation between the δ13Ccarb and δ13Corg values, up to 25‰, indicates the oldest evidence of organisms greater than 3.95 Ga. The discovery of the biogenic graphite enables geochemical study of the biogenic materials themselves, and will provide insight into early life not only on Earth but also on other planets.

Photochemical production of O3 in biomass burning plumes in the boundary layer over northern Australia

Author(s): Takegawa, N; Kondo, Y; Ko, M; Koike, M; Kita, K; Blake, DR; Hu, W; Scott, C; Kawakami, S; Miyazaki, Y; Russell-Smith, J; Ogawa, T | Abstract: In situ aircraft measurements of ozone (O3) and its precursors were made over northern Australia in August-September 1999 during the Biomass Burning and Lightning Experiment Phase B (BIBLE-B). A clear positive correlation of O3 with carbon monoxide (CO) was found in biomass burning plumes in the boundary layer (l3 km). The ΔO3/ΔCO ratio (linear regression slope of O3-CO correlation) is found to be 0.12 ppbv/ppbv, which is comparable to the ratio of 0.15 ppbv/ppbv observed at 0-4 km over the Amazon and Africa in previous studies. The net flux of O3 exported from northern Australia during BIBLE-B is estimated to be 0.3 Gmol O3/day. In the biomass burning region, large enhancements of O3 were coincident with the locations of biomass burning hot spots, suggesting that major O3 production occurred near fires (horizontal scale l50 km).

Airborne vacuum ultraviolet resonance fluorescence instrument for in situ measurement of CO

An airborne instrument for fast-response, high-precision measurement of tropospheric carbon monoxide (CO) was developed using a vacuum ultraviolet (VUV) resonance fluorescence technique. The excitation radiation is obtained by a DC discharge CO resonance lamp combined with an optical filter for the CO fourth positive band emission around 150 nm. The optical filter consists of a VUV monochromator and a crystalline quartz window (<147-nm cutoff). The crystalline quartz window ensures a sharp discrimination against wavelengths below 135.7 nm that yield a positive interference from water vapor. Laboratory tests showed that the optical system achieved a precision of 1. 1 parts per billion by volume (ppbv) at a CO concentration of 100 ppbv for a 1-s integration period, and the flow system provided a response time (1/e time constant) of ∼2 s. The aircraft measurement campaign Biomass Burning and Lightning Experiment-phase B (BIBLE-B) was conducted between August and September 1999 over the western Pacific and Australia. The flight data obtained during this campaign were used to demonstrate the high precision and fast response of the instrument. An intercomparison of the VUV CO measurement and a gas chromatographic CO measurement was conducted during BIBLE-B. Overall, these two independent measurements showed good agreement, within the experimental uncertainties.

U–Pb and Hf–W dating of young zircon in Mesosiderite Asuka 882023

Mesosiderites are unique stony-iron meteorites, composed of eucrite-like silicates and Fe–Ni metals. Their formation, including silicate–metal mixing and metamorphisms, provide important insights into early planetary processes in the inner solar system. This report describes the first in-situ U–Pb and Hf–W dating of zircon in a mesosiderite Asuka 882023. The U–Pb (4502 ± 75 Ma) and Hf–W (4532.8 + 5.7/-10.5 Ma) ages may represent timing of the zircon formation, which is considerably younger than crustal differentiation of the parent body. This evidence, combined with earlier studies of chronology, implies that mesosiderites were reheated at 4530–4520 Ma, clearly after the silicate–metal mixing.

Correction to “Nitric acid condensation on ice: 1. Non-HNO3 constituent of NOY condensing on upper tropospheric cirrus particles”

[1] Measurements of NOy condensation on cirrus particles during the SOLVE-I field campaign are analyzed and segregated based on altitude. Significant amounts ofNOywere found on the upper tropospheric ice particles; therefore condensation on ice appears to be an important method of NOy removal from the gas phase at the low temperatures of the Scandinavian upper troposphere. For the data set collected on 23 January 2000, NOy condensation on cirrus particles has different properties depending on whether the ice particles are sampled in the upper troposphere, where HNO 3 does not dominate NO Y , or in the lower stratosphere, where HNO 3 does dominate NOy Nitric acid becomes enriched in the gas phase as NOy condenses on upper tropospheric ice crystals, indicating that a non-HNO 3 component of NOy is condensing on upper tropospheric ice particles much faster and at higher concentrations than HNO 3 alone on this day. It is unclear which non-HNO 3 constituent of NOy is condensing on upper tropospheric ice particles, although N 2 O 5 is the most likely species. This condensation of a non-HNO 3 component of NOy is not universal in the upper troposphere but depends on the conditions of the air parcel in which sampling occurred, notably exposure to sunlight.