By using a dynamic branch enclosure system the emission of monoterpenes from European beech (Fagus sylvatica L.) was investigated during two consecutive summer vegetation periods in the years of 2002 ...and 2003 in Germany. All measurements were performed under field conditions within the framework of the ECHO project (Emission and Chemical Transformation of Biogenic Volatile Organic Compounds, AFO 2000). European beech was characterized as a substantial emitter of monoterpenes, with sabinene being the predominant compound released. The monoterpene emission from European beech was shown to be a function of light and temperature and agreed well to emission algorithms that consider a light and temperature dependent release of volatile organics. Standard emission factors that were measured from these sunlit leaves of European beech ranged up to 4–13 μg g−1 h−1 (normalized to 1000 μmol m−2 s−1, 30°C) in the years of 2003 and 2002, respectively. The nighttime emission of monoterpene compounds was negligible. Also the artificial darkening of the sunlit branch during daylight conditions led to an immediate cessation of monoterpene emission. European beech is the dominating deciduous tree species in Europe. To demonstrate the effect of an updated monoterpene emission factor for European beech in combination with the consideration of a light and temperature dependent monoterpene emission, we applied a species based model simulation on a European scale. With respect to conventional estimates of the European volatile organic compound budget, the latter simulation resulted in relative increases of 16% by taking solely this tree species into account. On local scales these increases exceeded even more than 100% depending on the respective vegetation area coverage of European beech.
Recent research pointed out the question of missing OH reactivity in a forest system and the question for unknown highly reactive biogenic emissions. In this study we show that coniferous forests are ...an important source of highly reactive hydrocarbons, the sesquiterpenes. We investigated the seasonality of terpene emissions from Scots pine to work out influences on atmospheric chemistry in different seasons for both mono- and sesquiterpenes. Especially sesquiterpenes (C
15) change dramatically in their contribution to the terpene emissions of Scots pine. Fourteen sesquiterpenes and oxygenated compounds were found in the emissions. In spring, the pattern was most complex with all 14 compounds being emitted, whereas in summer and fall it was reduced to 1,8-cineol and camphor. The emission pattern of the monoterpenes varied only slightly. The main compounds emitted were
α-pinene,
β-pinene, and 3-carene representing up to 90% of the total terpene emission. The total monoterpene emission rates varied from below detection limit to 460
pmol
m
−2
s
−1 with highest emission rates found in June. Standard emission rates of the main compounds calculated from the monthly measured diurnal emission courses varied considerably over the year. Highest values were found in spring and early summer with up to 700
pmol
m
−2
s
−1.
Ultrafine particles sampled during new particle formation bursts observed in the coastal zone were studied with transmission electron microscopy (TEM) and elemental analysis using energy‐dispersive X ...ray (EDX). It was observed that both iodine and sulphur were present in the new particles with diameter below 10 mn. Gaseous emissions of halogen compounds from seaweeds were also measured at the same location during low‐tide particle nucleation episodes. Based on the presence of iodine in the particle phase during low‐tide nucleation bursts, and the significant emission of iodine compounds from the seaweeds during these periods, it is apparent that part of the biogenic iodine species emitted from the seaweeds end up in the ultrafine particulate phase. It was not possible to quantitatively determine the iodine content in the particles; however, in most cases the relative contribution from iodine and sulphate was similar, while some cases indicated no sulphate. On larger sized particles the contribution of sulphate was significantly higher than iodine. It appears that the condensable species leading to the appearance of new particles in the coastal atmosphere is an iodine species. Whether or not this iodine species also participates in the nucleation of new stable clusters could not be completely verified.
The source strength of volatile organic compounds (VOCs) emitted by vegetation is of great interest for the understanding of processes in atmospheric chemistry and climate change. In this study ...terpene emissions from branches of European beech (Fagus sylvatica L.) were studied in a deciduous forest. Using the branch enclosure technique changes in the emission pattern and the variation of emission rates over the year were investigated over two consecutive vegetation periods. More than 10 monoterpene compounds were found in the emissions, among which sabinene dominates. For most compounds the emission pattern changed only slightly over the year. Interestingly, two compounds tentatively identified as para-cymene and cis-ocimene showed differences in the emission behaviour in late summer compared to the other terpenes. In contrast to previous studies our investigation characterise European beech as a strong emitter. For the main compounds the emission rates changed up to two orders of magnitude as a function of temperature and light over the day. In general, highest emission rates were observed in summer and lowest in fall. A seasonality was characterized by a temperature independent decline of emissions in late summer, resulting in changes of the standard emission rate on the order of one magnitude. A standard emission factor of up to 3.5 nmol m^sup -2^s^sup -1^ for the sum of measured terpenes was calculated. No emissions were found in early spring even though leaves were fully developed and temperature and light conditions were moderate. The results underline the importance of characterising the annual variation of the emission behaviour. Especially for the up-scaling to global VOC emissions, seasonal influences have to be considered to achieve realistic emission inventories.PUBLICATION ABSTRACT
This paper presents results from the first large‐scale in situ intercomparison of oxygenated volatile organic compound (OVOC) measurements. The intercomparison was conducted blind at the large (270 ...m3) simulation chamber, Simulation of Atmospheric Photochemistry in a Large Reaction Chamber (SAPHIR), in Jülich, Germany. Fifteen analytical instruments, representing a wide range of techniques, were challenged with measuring atmospherically relevant OVOC species and toluene (14 species, C1 to C7) in the approximate range of 0.5–10 ppbv under three different conditions: (1) OVOCs with no humidity or ozone, (2) OVOCs with humidity added (r.h. ≈ 50%), and (3) OVOCs with ozone (≈60 ppbv) and humidity (r.h. ≈ 50%). The SAPHIR chamber proved to be an excellent facility for conducting this experiment. Measurements from individual instruments were compared to mixing ratios calculated from the chamber volume and the known amount of OVOC injected into the chamber. Benzaldehyde and 1‐butanol, compounds with the lowest vapor pressure of those studied, presented the most overall difficulty because of a less than quantitative transfer through some of the participants' analytical systems. The performance of each individual instrument is evaluated with respect to reference values in terms of time series and correlation plots for each compound under the three measurement conditions. A few of the instruments performed very well, closely matching the reference values, and all techniques demonstrated the potential for quantitative OVOC measurements. However, this study showed that nonzero offsets are present for specific compounds in a number of instruments and overall improvements are necessary for the majority of the techniques evaluated here.
The present paper summarises results on the emission of biogenicvolatile organic compounds (BVOC) achieved within the frame of thenational `German Tropospheric Research Programme' (TFS) between 1997 ...and2000. Field measurements were carried out at the meteorologicalmonitoring station `Hartheimer Wald' located in the vicinity of Freiburg(upper Rhine valley), Germany, within a pine plantation dominated byScots pine (Pinus sylvestris L.). The measured BVOC emissionrates were used to determine the daily and seasonal variation of BVOCemission and its dependence on important meteorological and plantphysiological parameters. In parallel, laboratory experiments usingyoung trees of pine (P. sylvestris), poplar (Populustremula ×P. alba) and pedunculate oak (Quercusrobur L.) were performed, and the influence of abiotic (e.g.,light, temperature, seasonality, flooding) factors on the biosynthesisand emission of BVOC was quantified. Based on these data, emissionalgorithms were evaluated and a process-oriented numerical model for thesimulation of the isoprene emission by plants was developed. Inaddition, newly calculated land use and tree species distributions wereused for the calculation of an actual BVOC emission inventory ofGermany.PUBLICATION ABSTRACT
By using a dynamic branch enclosure system the emission of monoterpenes from European beech (Fagus sylvatica L.) was investigated during two consecutive summer vegetation periods in the years of 2002 ...and 2003 in Germany. All measurements were performed under field conditions within the framework of the ECHO project (Emission and Chemical Transformation of Biogenic Volatile Organic Compounds, AFO 2000). European beech was characterized as a substantial emitter of monoterpenes, with sabinene being the predominant compound released. The monoterpene emission from European beech was shown to be a function of light and temperature and agreed well to emission algorithms that consider a light and temperature dependent release of volatile organics. Standard emission factors that were measured from these sunlit leaves of European beech ranged up to 4–13 µg g-1 h-1 (normalized to 1000 µmol m-2 s-1, 30°C) in the years of 2003 and 2002, respectively. The nighttime emission of monoterpene compounds was negligible. Also the artificial darkening of the sunlit branch during daylight conditions led to an immediate cessation of monoterpene emission. European beech is the dominating deciduous tree species in Europe. To demonstrate the effect of an updated monoterpene emission factor for European beech in combination with the consideration of a light and temperature dependent monoterpene emission, we applied a species based model simulation on a European scale. With respect to conventional estimates of the European volatile organic compound budget, the latter simulation resulted in relative increases of 16% by taking solely this tree species into account. On local scales these increases exceeded even more than 100% depending on the respective vegetation area coverage of European beech
Elastically coupled multi-mass systems are a part of many industrial applications, like wind energy plants or drive trains in general. Dynamic load changes often cause peaks in the shaft torsion ...torque and jerk, resulting in damages to the system. A control strategy to reduce and / or limit this stress was presented, but needed difficult to implement and expensive measurements of the shaft torque. This paper presents an improved, observer based control strategy, eliminating the need for these expensive measurements, using only measurements usually already available. It also presents an easy to understand equivalent PID-cascade-structure for the control strategy, greatly improving the practical usability of the control presented.
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