Intercomparison of automated methodologies for determination of ambient isoprene during the PROPHET 1998 summer campaign

Barket, Dennis J.; Hurst, Julia M.; Couch, Tara L.; Colorado, Armando; Shepson, P. B.; Riemer, D. D.; Hills, A. J.; Apel, E. C.; Hafer, R.; Lamb, Brian; Westberg, Hal; Farmer, Charles T.; Stabenau, Erik; Zika, Rod G.

doi:10.1029/2000jd900562

Cited by 26 publications

(19 citation statements)

References 36 publications

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“…Since isoprene is by far the major reactive olefin that has been detected in the atmosphere at this site (Barket et al, 2001;Karl et al, 2003), there is little interference from other species. A full description of the instrument and calibration procedures can be found in Pressley et al (2005).…”

Section: Eddy Covariance Measurementsmentioning

confidence: 99%

The use of disjunct eddy sampling methods for the determination of ecosystem level fluxes of trace gases

et al. 2009

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Abstract. The concept of disjunct eddy sampling (DES) for use in measuring ecosystem-level micrometeorological fluxes is re-examined. The governing equations are discussed as well as other practical considerations and guidelines concerning this sampling method as it is applied to either the disjunct eddy covariance (DEC) or disjunct eddy accumulation (DEA) techniques. A disjunct eddy sampling system was constructed that could either be combined with relatively slow sensors (response time of 2 to 40 s) to measure fluxes using DEC, or could also be used to accumulate samples in stable reservoirs for later laboratory analysis (DEA technique). Both the DEC and DEA modes of this sampler were tested against conventional eddy covariance (EC) for fluxes of either CO 2 (DEC) or isoprene (DEA). Good agreement in both modes was observed relative to the EC systems. However, the uncertainty in a single DEA flux measurement was considerable (∼40%) due to both the reduced statistical sampling and the analytical precision of the concentration difference measurements. We have also re-investigated the effects of nonzero mean vertical wind velocity on accumulation techniques as it relates to our DEA measurements. Despite the higher uncertainty, disjunct eddy sampling can provide an alternative technique to eddy covariance for determining ecosystem-level fluxes for species where fast sensors do not currently exist.

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Section: Eddy Covariance Measurementsmentioning

confidence: 99%

The use of disjunct eddy sampling methods for the determination of ecosystem level fluxes of trace gases

et al. 2009

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“…Figure 1 shows the location of the UMBS measurement site on a regional map, along with point sources (>10 3 tons) of SO 2 and NO x for 2009. The unique feature of this site is that isoprene, MT and SQT have been measured since 1998 (Westberg et al, 2001;Apel et al, 2002;Pressley et al, 2005; al Barket Jr. et al, 2001;Kim et al, 2009;Ortega et al, 2007). The specific ecosystem at this site is in the transition zone between the mixed hardwood and the boreal forest on a high-outwash plain deposited by glacial drift (Pearsall, 1995;Schmid et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Isoprene suppression of new particle formation in a mixed deciduous forest

et al. 2011

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Abstract. Production of new particles over forests is an important source of cloud condensation nuclei that can affect climate. While such particle formation events have been widely observed, their formation mechanisms over forests are poorly understood. Our observations made in a mixed deciduous forest with large isoprene emissions during the summer displayed a surprisingly rare occurrence of new particle formation (NPF). Typically, NPF events occur around noon but no NPF events were observed during the 5 weeks of measurements. The exceptions were two evening ultrafine particle events. During the day, sulfuric acid concentrations were in the 10 6 cm −3 range with very low preexisting aerosol particles, a favorable condition for NPF to occur even during the summer. The ratio of emitted isoprene carbon to monoterpene carbon at this site was similar to that in Amazon rainforests (ratio >10), where NPF events are also very rare, compared with a ratio <0.5 in Finland boreal forests, where NPF events are frequent. Our results suggest that large isoprene emissions can suppress NPF formation in forests although the underlying mechanism for the suppression is unclear. The two evening ultrafine particle events were associated with the transported anthropogenic sulfur plumes and ultrafine particles were likely formed via ion-induced nucleation. Changes in landcover and environmental conditions could modify the isoprene suppression of NPF in some forest regions resulting in a radiative forcing that could have influence on the climate.

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“…However, PTR-MS cannot easily determine speciated monoterpene fluxes (Müller et al, 2009;Misztal et al, 2012) as these instruments tend measure the sum of all of the isobaric monoterpene species (e.g., Kim et al, 2009). Further, the Fast Isoprene Sensor suffers interference in environments where isoprene is not the dominant alkene (Edwards et al 2007;Barket et al, 2001). To measure the fluxes of both isoprene and speciated monoterpenes, methods that enable fast sampling with off-line analysis have been developed.…”

Section: Introductionmentioning

confidence: 99%

A disjunct eddy accumulation system for the measurement of BVOC fluxes: instrument characterizations and field deployment

et al. 2012

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Abstract. Biological volatile organic compounds (BVOCs), such as isoprene and monoterpenes, are emitted in large amounts from forests. Quantification of the flux of BVOCs is critical in the evaluation of the impact of these compounds on the concentrations of atmospheric oxidants and on the production of secondary organic aerosol. A disjunct eddy accumulation (DEA) sampler system was constructed for the measurement of speciated BVOC fluxes. Unlike traditional eddy covariance (EC), the relatively new technique of disjunct sampling differs by taking short, discrete samples that allow for slower sampling frequencies. Disjunct sample airflow is directed into cartridges containing sorbent materials at sampling rates proportional to the magnitude of the vertical wind. Compounds accumulated on the cartridges are then quantified by thermal desorption and gas chromatography. Herein, we describe our initial tests to evaluate the disjunct sampler including the application of vertical wind measurements to create optimized sampling thresholds. Measurements of BVOC fluxes obtained from DEA during its deployment above a mixed hardwood forest at the University of Michigan Biological Station (Pellston, MI) during the 2009 CABINEX field campaign are reported. Daytime (09:00 a.m. to 05:00 p.m. LT) isoprene fluxes, when averaged over the footprint of the tower, were 1.31 mg m −2 h −1 which are comparable to previous flux measurements at this location. Speciated monoterpene fluxes are some of the first to be reported from this site. Daytime averages were 26.7 µg m −2 h −1 for α-pinene and 10.6 µg m −2 h −1 for β-pinene. These measured concentrations and fluxes were compared to the output of an atmospheric chemistry model, and were found to be consistent with our knowledge of the variables that control BVOCs fluxes at this site.

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Intercomparison of automated methodologies for determination of ambient isoprene during the PROPHET 1998 summer campaign

Cited by 26 publications

References 36 publications

The use of disjunct eddy sampling methods for the determination of ecosystem level fluxes of trace gases

The use of disjunct eddy sampling methods for the determination of ecosystem level fluxes of trace gases

Isoprene suppression of new particle formation in a mixed deciduous forest

A disjunct eddy accumulation system for the measurement of BVOC fluxes: instrument characterizations and field deployment

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