Sou Matsunaga

Variation on the atmospheric concentrations of biogenic carbonyl compounds and their removal processes in the northern forest at Moshiri, Hokkaido Island in Japan

[1] Biogenic aldehydes, hydroxycarbonyls, and dicarbonyls in gas and particle phases were collected with an annular denuder sampling system (ADSS) in a Quercus crispula and Picea glehnii mast mixed forest. Eighty samples were collected from 22 to 29 August 2002. The size distributions of aerosols were also observed concurrently with a scanning mobility particle sizer (SMPS). The gaseous concentrations of these carbonyl compounds ranged from the detection limit (approximately 1 pptv) to 154 pptv (630 ng m -3 , 4-oxopentanal), and the particulate concentrations ranged from the detection limit (approximately 3 ng m -3 ) to 200 ng m -3 (4-oxopentanal). Although the production processes of these compounds are different from each other, the temporal variations of the gaseous concentrations were quite similar. In addition, the variation was also similar to that of the ambient temperature. Furthermore, gas-to-particle conversion was suggested to be an important removal process of these compounds. We could evaluate the importance of the gas-to-particle conversion as a removal process of the gaseous species by an ADSS measurement. In addition, the results of our experiment indicated that the conversion includes two processes. The first is an adsorption onto the aerosols which have already existed in the atmosphere. The next is dissolution into the water phases in the aerosols. The latter process was particular to water soluble compounds. The measurement allowed us to identify the most likely removal processes of biogenic semivolatile organic compounds (SOCs). In this study, we discuss about these processes of semivolatile and biogenic carbonyls in the forest atmosphere.

In situ measurement of isoprene in the marine air and surface seawater from the western North Pacific

Isoprene (2-methyl-1,3-butadiene) was measured on board of R/V Mirai for eight air samples and 14 seawater samples collected in the western North Pacific during ACE-Asia campaign (from 18 to 26 May 2001). The measurements were conducted in situ using a cryo-focus/gas chromatography/mass spectrometry (Cryo/GC/MS). Concentrations of isoprene ranged from 7.2 to 110 parts-per-trillion (pptv) in the marine air, and ranged from below 12 to 94 pmol l � 1 in the seawater. Based on these results, sea-to-air fluxes of isoprene were calculated to be 184 and 300 nmol m � 2 day � 1 for two samples, and the upper limits of the fluxes were also calculated to be from 32 to 300 nmol m � 2 day � 1 . Atmospheric isoprene concentrations cannot be explained only by the flux from the seawater. Thus, the concentrations of isoprene in the marine air in western North Pacific should be significantly affected by terrestrial vegetational emission and subsequent long-range atmospheric transport of isoprene. r 2002 Elsevier Science Ltd. All rights reserved.

Monoterpene and sesquiterpene emissions from Sugi (Cryptomeria japonica) based on a branch enclosure measurements

Abstract Sugi ( Cryptomeria japonica ) is the dominant tree species in the forested area of Japan. The forested area is approximately 250 000 km 2 and covers almost 70% of total area of Japan. However, there is little information available on biogenic volatile organic compounds (BVOCs) emissions from Sugi trees. BVOCs are known to have an important role in atmospheric chemistry due to their high reactivity and aerosol formation potential. Emissions of monoterpenes and sesquiterpenes, which are groups of BVOCs, were measured from Sugi using a bag enclosure system over four seasons at the Tanashi Experimental Station, located in a suburban area of Tokyo, Japan. Six monoterpenes accounted for the major emissions, and total monoterpene emission ranged up to 0.4 µg g –1 (dw) h –1 . The emission rates of both β –farnesene; which is a sesquiterpene, and monoterpenes clearly showed temperature dependence. Only β –farnesene was detected in the sesquiterpene fraction and determined to have a larger emission rate compared to that of total monoterpenes. The coefficient β for total monoterpene and β –farnesene calculated by G93 algorithm were 0.10 and 0.22, respectively. However, β showed largely different values on August (monoterpenes) and April (β–farnesene). The emission rates of β – farnesene show almost the same values in measured individuals and ranged from the detection limit (approximately 0.1 ng g –1 (dw) h –1 ) to 1.5 µg g –1 (dw) h –1 . The basal emission factor of monoterpenes in summer and sesquiterpenes in spring were generally lower compared to other seasons. This study indicated that Sugi trees in suburban areas emit sesquiterpene at a higher rate than total monoterpenes.

Gas-aerosol partitioning of semi volatile carbonyls in polluted atmosphere in Hachioji, Tokyo

Gaseous and particulate semi volatile carbonyls have been measured in urban air using an annular denuder sampling system. Three dicarbonyls, five aliphatic aldehydes and two hydroxy carbonyls were observed. Concentrations of other biogenic and anthropogenic volatile organic compounds (VOCs), SO2, CO, NO2 and particle concentration were also measured. Estimated gas-aerosol equilibrium constants for the carbonyls showed an inverse correlation with the concentrations of anthropogenic pollutants such as benzene, isopentane and SO2. This suggests that the increase in the fraction of non-polar anthropogenic particles in the atmosphere could change the average property of the ambient aerosols and drive the gas particle equilibrium of the carbonyls to the gas phase. This trend is uncommon in remote forest air. In this study, we examined the factors controlling the equilibrium in the polluted atmosphere and show that there is a difference in gas-aerosol partition between polluted and clean air.

Determination and potential importance of diterpene (kaur-16-ene) emitted from dominant coniferous trees in Japan

Reactive volatile organic compounds (VOCs) are known to affect atmospheric chemistry. Biogenic VOCs (BVOCs) have a significant impact on regional air quality due to their large emission rates and high reactivities. Diterpenes (most particularly, kaur-16-ene) were detected in all of the 205 enclosure air samples collected over multiple seasons at two different sites from Cryptomeria japonica and Chamaecyparis obtusa trees, the dominant coniferous trees in Japan,. The emission rate of kaur-16-ene, was determined to be from 0.01 to 7.1 μg dwg(-1) h(-1) (average: 0.61 μg dwg(-1) h(-1)) employing branch enclosure measurements using adsorbent sampling followed by solid phase-liquid extraction techniques. The emission rate was comparable to that of monoterpenes, which is known major BVOC emissions, collected from the same branches. In addition, total emission of kaur-16-ene at 30°C was estimated to exceed that of total anthropogenic VOC emissions.