364 research outputs found
The use of disjunct eddy sampling methods for the determination of ecosystem level fluxes of trace gases
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 CO2 (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
Rapid formation of isoprene photo-oxidation products observed in Amazonia
Isoprene represents the single most important reactive hydrocarbon for atmospheric chemistry in the tropical atmosphere. It plays a central role in global and regional atmospheric chemistry and possible climate feedbacks. Photo-oxidation of primary hydrocarbons (e.g. isoprene) leads to the formation of oxygenated VOCs (OVOCs). The evolution of these intermediates affects the oxidative capacity of the atmosphere (by reacting with OH) and can contribute to secondary aerosol formation, a poorly understood process. An accurate and quantitative understanding of VOC oxidation processes is needed for model simulations of regional air quality and global climate. Based on field measurements conducted during the Amazonian Aerosol Characterization Experiment (AMAZE-08) we show that the production of certain OVOCs (e.g. hydroxyacetone) from isoprene photo-oxidation in the lower atmosphere is significantly underpredicted by standard chemistry schemes. Recently reported fast secondary production could explain 50% of the observed discrepancy with the remaining part possibly produced via a novel primary production channel, which has been proposed theoretically. The observations of OVOCs are also used to test a recently proposed HO<sub>x</sub> recycling mechanism via degradation of isoprene peroxy radicals. If generalized our observations suggest that prompt photochemical formation of OVOCs and other uncertainties in VOC oxidation schemes could result in uncertainties of modelled OH reactivity, potentially explaining a fraction of the missing OH sink over forests which has previously been largely attributed to a missing source of primary biogenic VOCs
Response of Soybean Insects to Foliar Applications of a Chitin Synthesis Inhibitor TH 6040
The activity of TH 6040, a chitin synthesis inhibitor, was determined against velvetbean caterpillar, Anticarsia gemmatalis Hübner, and other soybean defoliators in field tests in Georgia, South Carolina, and Brazil. Single applications at rates as low as 75 g AI/ha afforded adequate initial and excellent residual control of A. gemmatalis and some suppression of low populations of Plusia spp. Two applications at higher rates gave significant control of soybean looper, Pseudoplusia includens (Walker), and showed promise against green cloverworm, Plathypena scabra (F.), and Mexican bean beetle, Epilachna varivestis Mulsant. Populations of geocorids and nabids were lower in 1 test, possibly because of insecticidal activity, scarcity of prey, or both
Response of Soybean Insects to Foliar Applications of a Chitin Synthesis Inhibitor TH 6040
The activity of TH 6040, a chitin synthesis inhibitor, was determined against velvetbean caterpillar, Anticarsia gemmatalis Hübner, and other soybean defoliators in field tests in Georgia, South Carolina, and Brazil. Single applications at rates as low as 75 g AI/ha afforded adequate initial and excellent residual control of A. gemmatalis and some suppression of low populations of Plusia spp. Two applications at higher rates gave significant control of soybean looper, Pseudoplusia includens (Walker), and showed promise against green cloverworm, Plathypena scabra (F.), and Mexican bean beetle, Epilachna varivestis Mulsant. Populations of geocorids and nabids were lower in 1 test, possibly because of insecticidal activity, scarcity of prey, or both
Insetos da soja no Brasil.
Insetos-pragas da soja; Inimigos naturais de insetos-pragas da soja; Importancia economica de especies-pragas da soja; Sistemas de manejo de insetos da soja.bitstream/item/77369/1/CNPSO-BOL.-TEC.-1-77.pd
Texas Turkey Poults
Weekly report of the Texas Crop and Livestock Reporting Service on turkey poult numbers in Texas and compared with other states. It includes compiled statistics across six consecutive weeks during two years for turkey eggs set and poults hatched
Texas Turkey Poults
Weekly report of the Texas Crop and Livestock Reporting Service on turkey poult numbers in Texas and compared with other states. It includes compiled statistics across six consecutive weeks during two years for turkey eggs set and poults hatched
Texas Turkey Poults
Weekly report of the Texas Crop and Livestock Reporting Service on turkey poult numbers in Texas and compared with other states. It includes compiled statistics across six consecutive weeks, from the week ending March 21 to the week ending April 18, during 1980 and 1981 for turkey eggs set and poults hatched
Texas Turkey Poults
Weekly report of the Texas Crop and Livestock Reporting Service on turkey poult numbers in Texas and compared with other states. It includes compiled statistics across six consecutive weeks during two years for turkey eggs set and poults hatched
Texas Turkey Poults
Weekly report of the Texas Crop and Livestock Reporting Service on turkey poult numbers in Texas and compared with other states. It includes compiled statistics across six consecutive weeks during two years for turkey eggs set and poults hatched
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