The flux of carbonyl sulfide and carbon disulfide between the atmosphere and a spruce forest

Abstract

Abstract. Turbulent fluxes of carbonyl sulfide (COS) and carbon disulfide (CS 2 ) were measured over a spruce forest in Central Germany using the relaxed eddy accumulation (REA) technique. A REA sampler was developed and validated using simultaneous measurements of CO 2 fluxes by REA and by eddy correlation. REA measurements were conducted during six campaigns covering spring, summer, and fall between 1997 and 1999. Both uptake and emission of COS and CS 2 by the forest were observed, with deposition occurring mainly during the sunlit period and emission mainly during the dark period. On the average, however, the forest acts as a sink for both gases. The average fluxes for COS and CS 2 are −93 ± 11.7 pmol m −2 s −1 and −18 ± 7.6 pmol m −2 s −1 , respectively. The fluxes of both gases appear to be correlated to photosynthetically active radiation and to the CO 2 and H 2 O fluxes, supporting the idea that the air-vegetation exchange of both gases is controlled by stomata. An uptake ratio COS/CO 2 of 10 ± 1.7 pmol µmol −1 has been derived from the regression line for the correlation between the COS and CO 2 fluxes. This uptake ratio, if representative for the global terrestrial net primary production, would correspond to a sink of 2.3 ± 0.5 Tg COS yr −1 .

Global uptake of carbonyl sulfide (COS) by terrestrial vegetation: Estimates corrected by deposition velocities normalized to the uptake of carbon dioxide (CO<sub>2</sub>)

“…The latter group, however, did not take into account the preferred uptake and enzymatic consumption of COS as related to the CO 2 assimilation. In contrast, the results of Xu et al (2002), based on flux measurements over a coniferous forest, fit well into such an estimation by taking into account a preferential uptake ratio of COS/CO 2 . Including such a preference by correction with the deposition velocity ratios, the new data presented here show that this new procedure results in a significant increase of the COS sink strength calculation again, as productivity, seasonality as well as the preferred uptake is taken into account.…”

“…In case of enclosure measurements we used the net exchange as measured with the enclosed branch or leaf (Net Primary Productivity; NPP cuvette ) in order to compare with other published data. However, in case of one data set (spruce forest, Xu et al 2002) from flux studies above the forest, a correction might be necessary, as this flux value is representing the net exchange as a result of gross photosynthesis minus autotrophic (=NPP) and heterotrophic (soils) respiration. For the enclosure related data we found a range of V d COS /V d CO 2 between 1.3 and 5.5 with the exception of 0.4 for non fertilized pea plants (Kesselmeier and Merk, 1993), 7.0 for young corn plants (Hoffmann, 1993) and 8.7-10.3 for a spruce enclosure study (Huber, 1994).…”

Characteristics and anthropogenic sources of carbonyl sulfide in Beijing

“…3a, COS mixing ratios during the summer day with wind speed less than 1 m/sec gradually decreased during morning hours, and slightly increased during noontime (12:00-14:00), and then decreased again in the afternoon followed by an increase after sunset. The typical diurnal variation of COS in the summer day was consistent with strong COS uptake by vegetation, because COS uptake by vegetation is mainly controlled by stomatal aperture (Xu et al, 2002) and the stomatal aperture is usually closed at noontime under strong sunlight irradiation and extremely high temperature. In addition, the relatively fast exchange between the lower layer and the upper layer of the atmosphere at noontime also can result in elevation of the ground COS level because of the relatively high COS mixing ratio in the upper layer.…”

Thermochemical stabilities and structures of the cluster ions OCS+, S2+, H+(OCS), and C2H5+ with OCS molecules in the gas phase

“…The behavior of the cluster ionÅ intensitiesÅ asÅ equilibriumÅ was approachedÅ was highlyÅunusual.ÅThis is illustratedÅinÅFigureÅ5,Åwhich demonstratesÅ theÅ timeÅ profiles of the normalized intensities for H ϩ (OCS)(OCS) n with n ϭ 0 -3 after the electron pulse at 161.5 K (1000/T ϭ 6.19). The H ϩ (OCS)(OCS) 3 intensity shows an initial steep increase followed by a rapid decrease toward a time-independent value. The same pattern, although less pronounced, applies to H ϩ (OCS)(OCS) 2 cluster.…”

“…OCS is the major source of stratospheric background aerosol because of its high abundance (ϳ500 ppt) and long lifetime (2-7 y) in the troposphere. Owing its physico-chemical properties, OCS contributes significantly to the earth's radiation budget and is of considerable importance in heterogeneous reactions involved in chemical ozone destruction [3]. The compound has also been detected in the interstellar medium [2].…”