Entity

Time filter

Source Type

Oregon City, OR, United States

Kim S.,U.S. National Center for Atmospheric Research | Karl T.,U.S. National Center for Atmospheric Research | Guenther A.,U.S. National Center for Atmospheric Research | Tyndall G.,U.S. National Center for Atmospheric Research | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2010

Two proton-transfer-reaction mass spectrometry systems were deployed at the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H 2O2, Organics and Nitrogen-Southern Rocky Mountain 2008 field campaign (BEACHON-SRM08; July to September, 2008) at the Manitou Forest Observatory in a ponderosa pine woodland near Woodland Park, Colorado USA. The two PTR-MS systems simultaneously measured BVOC emissions and ambient distributions of their oxidation products. Here, we present mass spectral analysis in a wide range of masses (m/z 40+ to 210+) to assess our understanding of BVOC emissions and their photochemical processing inside of the forest canopy. The biogenic terpenoids, 2-methyl-3-butene-2-ol (MBO, 50.2%) and several monoterpenes (MT, 33.5%) were identified as the dominant BVOC emissions from a transmission corrected mass spectrum (PTR-MS), averaged over the daytime (11 a.m. to 3 p.m., local time) of three days. To assess contributions of oxidation products of local BVOC, we calculate an oxidation product spectrum with the OH-and ozone-initiated oxidation product distribution mass spectra of two major BVOC emissions at the ecosystem (MBO and β-pinene) that were observed from laboratory oxidation experiments. The majority (∼76%) of the total signal in the transmission corrected PTR-MS spectra could be explained by identified compounds. The remainder are attributed to oxidation products of BVOC emitted from nearby ecosystems and transported to the site, and oxidation products of unidentified BVOC emitted from the ponderosa pine ecosystem. Source


Misztal P.K.,UK Center for Ecology and Hydrology | Misztal P.K.,University of Edinburgh | Owen S.M.,UK Center for Ecology and Hydrology | Guenther A.B.,U.S. National Center for Atmospheric Research | And 12 more authors.
Atmospheric Chemistry and Physics | Year: 2010

During two field campaigns (OP3 and ACES), which ran in Borneo in 2008, we measured large emissions of estragole (methyl chavicol; IUPAC systematic name 1-allyl-4-methoxybenzene; CAS number 140-67-0) in ambient air above oil palm canopies (0.81 mgm-2 h-1 and 3.2 ppbv for mean midday fluxes and mixing ratios respectively) and subsequently from flower enclosures. However, we did not detect this compound at a nearby rainforest. Estragole is a known attractant of the African oil palm weevil (Elaeidobius kamerunicus), which pollinates oil palms (Elaeis guineensis). There has been recent interest in the biogenic emissions of estragole but it is normally not included in atmospheric models of biogenic emissions and atmospheric chemistry despite its relatively high potential for secondary organic aerosol formation from photooxidation and high reactivity with OH radical. We report the first direct canopy-scale measurements of estragole fluxes from tropical oil palms by the virtual disjunct eddy covariance technique and compare them with previously reported data for estragole emissions from Ponderosa pine. Flowers, rather than leaves, appear to be the main source of estragole from oil palms; we derive a global estimate of estragole emissions from oil palm plantations of ∼0.5 Tg y-1. The observed ecosystem mean fluxes (0.44 mgm-2 h-1) and mean ambient volume mixing ratios (3.0 ppbv) of estragole are the highest reported so far. The value for midday mixing ratios is not much different from the total average as, unlike other VOCs (e.g. isoprene), the main peak occurred in the evening rather than in the middle of the day. Despite this, we show that the estragole flux can be parameterised using a modified G06 algorithm for emission. However, the model underestimates the afternoon peak even though a similar approach works well for isoprene. Our measurements suggest that this biogenic compound may have an impact on regional atmospheric chemistry that previously has not been accounted for in models and could become more important in the future due to expansion of the areas of oil palm plantation. © 2010 Author(s). Source


Geron C.,U.S. Environmental Protection Agency | Daly R.,U.S. Environmental Protection Agency | Harley P.,U.S. National Center for Atmospheric Research | Rasmussen R.,Oregon Graduate Institute | And 4 more authors.
Chemosphere | Year: 2016

Leaf-level isoprene and monoterpene emissions were collected and analyzed from five of the most abundant oak (Quercus) species in Central Missouri's Ozarks Region in 2012 during PINOT NOIR (Particle Investigations at a Northern Ozarks Tower - NOx, Oxidants, Isoprene Research). June measurements, prior to the onset of severe drought, showed isoprene emission rates and leaf temperature responses similar to those previously reported in the literature and used in Biogenic Volatile Organic Compound (BVOC) emission models. During the peak of the drought in August, isoprene emission rates were substantially reduced, and response to temperature was dramatically altered, especially for the species in the red oak subgenus (Erythrobalanus). Quercus stellata (in the white oak subgenus Leucobalanus), on the other hand, increased its isoprene emission rate during August, and showed no decline at high temperatures during June or August, consistent with its high tolerance to drought and adaptation to xeric sites at the prairie-deciduous forest interface. Mid-late October measurements were conducted after soil moisture recharge, but were affected by senescence and cooler temperatures. Isoprene emission rates were considerably lower from all species compared to June and August data. The large differences between the oaks in response to drought emphasizes the need to consider BVOC emissions at the species level instead of just the whole canopy. Monoterpene emissions from Quercus rubra in limited data were highest among the oaks studied, while monoterpene emissions from the other oak species were 80-95% lower and less than assumed in current BVOC emission models. Major monoterpenes from Q. rubra (and in ambient air) were p-cymene, α-pinene, β-pinene, d-limonene, γ-terpinene, β-ocimene (predominantly1,3,7-trans-β-ocimene, but also 1,3,6-trans-β-ocimene), tricyclene, α-terpinene, sabinene, terpinolene, and myrcene. Results are discussed in the context of canopy flux studies conducted at the site during PINOT NOIR, which are described elsewhere. The leaf isoprene emissions before and during the drought were consistent with above canopy fluxes, while leaf and branch monoterpene emissions were an order of magnitude lower than the observed above canopy fluxes, implying that other sources may be contributing substantially to monoterpene fluxes at this site. This strongly demonstrates the need for further simultaneous canopy and enclosure BVOC emission studies. © 2015 . Source


Grant
Agency: Department of Defense | Branch: Defense Advanced Research Projects Agency | Program: STTR | Phase: Phase I | Award Amount: 98.50K | Year: 1999

N/A


Mhaidat K.M.,Oregon Graduate Institute | Mhaidat K.M.,Jordan University of Science and Technology | Jabri M.A.,Oregon Graduate Institute | Jabri M.A.,Portland State University | Hammerstrom D.W.,Oregon Graduate Institute
International Journal of Circuit Theory and Applications | Year: 2011

In this paper, we present an efficient representation of the analog signal using the inter-pulse interval (IPI) time. Based on this representation, methods and circuits for conversion and computation have been developed. To validate these methods and circuits, a test chip has been fabricated using a 0.35μm mixed-signal CMOS process. Together, the circuits occupy 59.52 × 10 -3mm2 of chip area and consume 8.8 mW of power from a 3.2 V supply. Test results at 10 MHz and simulations results at 100 MHz show good accuracy over ±600mV range. © 2010 John Wiley & Sons, Ltd. Source

Discover hidden collaborations