Fluxes of CO sub(2), CH sub(4), and N sub(2)O from forest soils were measured with an enclosed chamber technique between October 1990 and December 1991 in a deciduous forest near Darmstadt, Germany. ...Flux measurements were made before and after the removal of leaves and humus layer from the forest floor, and gas fluxes from the leaves and humus alone were also measured as well as depth profiles of CH sub(4), N sub(2)O, and soil moisture. Except for N sub(2)O, large seasonal variations were observed with generally higher gas fluxes during the summer. CO sub(2) and CH sub(4) fluxes were significantly dependent on changes in ambient temperature, whereas N sub(2)O fluxes were more affected by soil moisture. A good correlation between CO sub(2) production and CH sub(4) uptake was observed, but no relationship was found between N sub(2)O emissions and either CO sub(2) or CH sub(4) fluxes. Depth profiles of the CH sub(4) mixing ratio in soil air consistently showed an exponential decrease with depth, whereas N sub(2)O profiles were highly variable and appeared to be related to changes in soil moisture. The manipulated soil experiments indicate that the leaves and the humus layers contribute significantly to the soil-atmosphere exchange of trace gases.
Fluxes of CO
2
, CH
4
, and N
2
O from forest soils were measured with an enclosed chamber technique between October 1990 and December 1991 in a deciduous forest near Darmstadt, Germany. Flux ...measurements were made before and after the removal of leaves and humus layer from the forest floor, and gas fluxes from the leaves and humus alone were also measured as well as depth profiles of CH
4
, N
2
O, and soil moisture. Except for N
2
O, large seasonal variations were observed with generally higher gas fluxes during the summer. CO
2
and CH
4
fluxes were significantly dependent on changes in ambient temperature, whereas N
2
O fluxes were more affected by soil moisture. A good correlation between CO
2
production and CH
4
uptake was observed, but no relationship was found between N
2
O emissions and either CO
2
or CH
4
fluxes. Depth profiles of the CH
4
mixing ratio in soil air consistently showed an exponential decrease with depth, whereas N
2
O profiles were highly variable and appeared to be related to changes in soil moisture. The manipulated soil experiments indicate that the leaves and the humus layers contribute significantly to the soil-atmosphere exchange of trace gases.
Fluxes of CO sub(2) , CH sub(4) , and N sub(2) O from forest soils were measured with an enclosed chamber technique between October 1990 and December 1991 in a deciduous forest near Darmstadt, ...Germany. Flux measurements were made before and after the removal of leaves and humus layer from the forest floor, and gas fluxes from the leaves and humus alone were also measured as well as depth profiles of CH sub(4) , N sub(2) O, and soil moisture. Except for N sub(2) O, large seasonal variations were observed with generally higher gas fluxes during the summer. CO sub(2) and CH sub(4) fluxes were significantly dependent on changes in ambient temperature, whereas N sub(2) O fluxes were more affected by soil moisture. A good correlation between CO sub(2) production and CH sub(4) uptake was observed, but no relationship was found between N sub(2) O emissions and either CO sub(2) or CH sub(4) fluxes. Depth profiles of the CH sub(4) mixing ratio in soil air consistently showed an exponential decrease with depth, whereas N sub(2) O profiles were highly variable and appeared to be related to changes in soil moisture. The manipulated soil experiments indicate that the leaves and the humus layers contribute significantly to the soil-atmosphere exchange of trace gases.
Surface waters along a cruise track in the East Pacific Ocean were undersaturated in methyl bromide (CH sub(3)Br) in most areas except for coastal and upwelling regions, with saturation anomalies ...ranging from +100 percent in coastal waters to -50 percent in open ocean areas, representing a regionally weighted mean of -16 (-13 to -20) percent. The partial lifetime of atmospheric CH sub(3)Br with respect to calculated oceanic degradation along this cruise track is 3.0 (2.9 to 3.6) years. The global, mean dry mole fraction of CH sub(3)Br in the atmosphere was 9.8 plus or minus 0.6 parts per trillion, with an interhemispheric ratio of 1.31 plus or minus 0.08. These data indicate that similar to 8 percent (0.2 parts per trillion) of the observed interhemispheric difference in atmospheric CH sub(3)Br could be attributed to an uneven global distribution of oceanic sources and sinks.
Sulfur hexafluoride (SF
6
), an anthropogentically produced compound that is a potent greenhouse gas, has been measured in a number of NOAA GMDL air sampling programs. These include high resolution ...latitudinal profiles over the Atlantic and Pacific oceans, weekly flask samples from seven remote, globally distributed sites, hourly in situ measurements in rural North Carolina, and a series of archived air samples from Niwot Ridge, Colorado. The observed increase in atmospheric mixing ratio is consistent with an overall quadratic growth rate, at 6.9±0.2% yr
−1
(0.24±0.01 ppt yr
−1
) for early 1996. From these data we derive an early 1996 emission rate of 5.9±0.2 Gg SF
6
yr
−1
and an interhemispheric exchange time of 1.3±0.1 years.
Sulfur hexafluoride (SF sub(6)), an anthropogentically produced compound that is a potent greenhouse gas, has been measured in a number of NOAA GMDL air sampling programs. These include high ...resolution latitudinal profiles over the Atlantic and Pacific oceans, weekly flask samples from seven remote, globally distributed sites, hourly in situ measurements in rural North Carolina, and a series of archived air samples from Niwot Ridge, Colorado. The observed increase in atmospheric mixing ratio is consistent with an overall quadratic growth rate, at 6.9 plus or minus 0.2% yr super(-1) (0.24 plus or minus 0.01 ppt yr super(-1)) for early 1996. From these data we derive an early 1996 emission rate of 5.9 plus or minus 0.2 Gg SF sub(6) yr super(-1) and an interhemispheric exchange time of 1.3 plus or minus 0.1 years.
During the Mediterranean Intensive Oxidant Study MINOS in August 2001, 87 air samples were collected at the ground-based station Finokalia (35° 19' N, 25° 40' E) on the north coast of Crete and ...subsequently analysed by GC-MS. The analysis includes various hydrocarbons, organo-halogens, HCFCs and CFCs. These compounds have a wide variety of sources and sinks and a large range of atmospheric lifetimes. By plotting the measured variability of these species against lifetime, we found that the compounds describe a linear relationship. It is shown, based on air mass origin analysis and chemical ratios, that several distinct anthropogenic sources influenced the atmospheric composition in Crete. Propane observations are compared to a global model to assess the fossil fuel related emission inventory. Although the model reproduces the general pattern of the propane variations, the model mixing ratios are systematically too low by a factor of 1.5 to 3, probably due to an underestimation of the propane emissions from east European countries in the underlying global database EDGAR. Another important finding was that methyl chloroform, a compound banned under the Montreal protocol, showed significant enhancements from background, which were well correlated with CFC-113. This suggests continued use and emission of methyl chloroform by one or more European countries. We also discuss the observed variations of bromomethane and suggest that the significant peak observed on 12 August 2001 reflects heavy agricultural use as a soil fumigant in Italy.
This research was aimed to determine the occurrence of Brachyspira (B.) hyodysenteriae in Swiss multiplier pig herds.
In a pilot study a direct real-time polymerase chain reaction (PCR) method for ...B. hyodysenteriae was compared to culture followed by PCR on 106 samples from three herds. Subsequently 40 multiplier herds were epidemiologically characterized and analysed for the presence of B. hyodysenteriae using direct PCR on 1412 rectal swabs. For external validation 20 swabs obtained from two positive conventional herds were analysed.
The comparison of direct PCR with culture followed by PCR resulted in a moderate agreement (kappa index: 0.58). In the two conventional herds, 35% of the samples (7/20) tested positive. Samples from 39 multipliers tested negative. In one multiplier herd, 25% (9/36) of the samples tested PCR positive. Risk factors in the multiplier herd may have been rodents or birds, but not pig purchase.
B. hyodysenteriae have been detected in a Swiss multiplier herd, which underlines the threat of potential spread by replacement pigs. Consequently, a Brachyspira monitoring programme was established for Swiss multiplier herds.
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