F. Slemr

Bio: F. Slemr is an academic researcher from Max Planck Society. The author has contributed to research in topics: Organic peroxide & Ozonolysis. The author has an hindex of 5, co-authored 5 publications receiving 653 citations.

Distribution, speciation, and budget of atmospheric mercury

Abstract: Total gaseous mercury (TGM) concentrations over the Atlantic Ocean and over Central Europe were measured repeatedly in the years 1978–1981. The latitudinal TGM distribution showed a pronounced and reproducible interhemispherical difference with higher TGM concentrations in the Northern Hemisphere. TGM was found to be vertically well mixed within the troposphere. The TGM concentration seems to increase with time at a rate of 10±8%/yr in the Northern and 8±3%/yr in the Southern Hemisphere. Measurements of mercury speciation showed that elemental mercury is the main TGM component contributing more than 92% and 83% of TGM in marine and continental air, respectively. The tropospheric mercury burden was calculated to be 6×109g. The interhemispheric distribution and temporal and spatial variability of TGM imply a tropospheric residence time of TGM of about 1 yr. Sink strengths calculated independently from the measured mercury concentration on particles and in rainwater are consistent with the above figures.

Field measurements of NO and NO2 emissions from fertilized and unfertilized soils

Abstract: Field measurements of NO and NO2 emissions from soils have been performed in Finthen near Mainz (F.R.G.) and in Utrera near Seville (Spain). The applied method employed a flow box coupled with a chemiluminescent NO x detector allowing the determination of minimum flux rates of 2 μg N m-2 h-1 for NO and 3 μg m-2 h-1 for NO2.

Nitrous oxide emissions from fertilized and unfertilized soils in a subtropical region (Andalusia, Spain)

Abstract: Field measurements of N2O emission rates were carried out from August until October 1982 in a subtropical region in Europe, i.e. in Andalusia, Spain. The measurements were performed by using an automatic sampling and analysis technique allowing the semi-continuous determination of N2O emission rates. The N2O emission rates were positively correlated to the soil surface temperature and exhibited a diurnal rhythm with maximum rates in the afternoon and minimum rates in the early morning with average values of 1 μg N2O−N/m2/h for the grass lawn and 15 μg N2O−N/m2/h for cultivated land. Application of urea and ammonium nitrate resulted in elevated N2O emission rates when compared to the unfertilized control. The loss of fertilizer-nitrogen as N2O was 0.18% for urea and 0.04% for NH4NO3 which compares very well with data obtained in a temperate climate (Germany). The total source strength of fertilizer-derived N2O is estimated to be 0.01–2.2 Tg N2O−N per year. The N2O flux from unfertilized natural soils may be as high as 4.5 Tg N2O−N, indicating that the N2O emission from soils contributes significantly to the global N2O budget.

Hydrogen Peroxide, Organic Peroxides and Higher Carbonyl Compounds Determined during the BERLIOZ Campaign

Abstract: Gas-phase H2O2, organic peroxides and carbonyl compounds were determined at various sites from Mid-July to early August 1998 during the BERLIOZ campaign in Germany. The sites were located northwest of Berlin and were chosen to determine pollutants downwind of the city emissions during a summer smog episode. Hydrogen peroxide (H2O2), methyl hydroperoxide (MHP, CH3OOH) and occasionally hydroxy methyl hydroperoxide (HMHP, HOCH2OOH) were quantified in air samples by commercial fluorimetric methods and classical HPLC with post-column derivati-sation by horseradish peroxidase/p-hydroxyphenyl acetic acid and fluorimetric detection. Carbonyl compounds were determined in ambient air by a novel method based on O-pentafluorobenzyl hy-droxylamine as derivatisation agent. Mixing ratio profiles of the hydroperoxides and the carbonyl compounds are reported for the intensive phase of the campaign, 20–21 July, 1998. Peroxides showed pronounced diurnal variations with peak mixing ratios in the early afternoon. At times, a second maximum was observed in the late afternoon. The major part of the H2O2 was formed through recombination reactions of HO2 radicals, but there is some evidence that H2O2 is also formed from ozonolysis of anthropogenic and/or biogenic alkenes. Diurnal variations of mixing ratios of various carbonyl compounds are reported: alkanals (C2 to C10, isobutanal), unsaturated carbonyl compounds (methacrolein, methylvinylketone, acrolein), hydroxycarbonyl (glycolaldehyde, hydroxyacetone) and dicarbonyl compounds (glyoxal, methylglyoxal, biacetyl), aromatic compounds (benzaldehyde, o- and m-tolylaldehyde) and pinonaldehyde.

Quecksilber in der Troposphäre

Abstract: Es werden Methoden fur die Bestimmung des Gesamtquecksilbers und fur Dimethylquecksilber im Konzentrationsbereich von 0,1 bis etwa 1000 ng Hg/m3 (STP) beschrieben. Beide Methoden basieren auf Anreicherung von Quecksilber und seiner Verbindungen an gold- bzw. silberbeschichteter Quarzwolle und auf dem Nachweis des Quecksilbers mit Atom-Absorptions- (AAS) bzw. Atom-Emissions-Spektroskopie (AES). Fur Messungen in reiner, anthropogen nicht beeinfluster Luftmasse ist ein Sammelvolumen von 200–400 l erforderlich, was einer Sammelzeit von 20 – 40 Minuten pro Einzelwert entspricht. Beide Methoden konnen bei Feldmessungen auf Schiffen und Flugzeugen eingesetzt werden. Die ersten Ergebnisse einiger Mesreihen in der unteren und oberen Troposphare zeigen eine gleichmasige “background”-Konzentration von 1,3 – 4,0 ng Hg/m3 (STP). Two analytical methods are described: one for the determination of total mercury and one for the determination of dimethyl mercury concentration in air. The methods can be applied within a concentration range of 0.1 -lo00 ng Hg/m3(STP). Both methods are based on the collection of different mercury species on gold and/or silver coated quartz wool. The mercury content of the collectors is subsequently deter- mined by atom absorption (AAS) or atom emission (AES) spectrometry. For measurements in clean atmosphere a sample volume of 200-400 I is required for analysis corresponding to a sampling time of 20-40 minutes. Both methods can be used for airplane and ship measurements. First results of the measurements in the lower and upper troposphere show a uniform background concentration of total mercury of 1.3 -4.0 ng Hg/m3(STP).

Soils, a sink for N2O? A review

Abstract: Soils are the main sources of the greenhouse gas nitrous oxide (N2O). The N2O emission at the soil surface is the result of production and consumption processes. So far, research has concentrated on net N2O production. However, in the literature, there are numerous reports of net negative fluxes of N2O, (i.e. fluxes from the atmosphere to the soil). Such fluxes are frequent and substantial and cannot simply be dismissed as experimental noise. Net N2O consumption has been measured under various conditions from the tropics to temperate areas, in natural and agricultural systems. Low mineral N and large moisture contents have sometimes been found to favour N2O consumption. This fits in with denitrification as the responsible process, reducing N2O to N2. However, it has also been reported that nitrifiers consume N2O in nitrifier denitrification. A contribution of various processes could explain the wide range of conditions found to allow N2O consumption, ranging from low to high temperatures, wet to dry soils, and fertilized to unfertilized plots. Generally, conditions interfering with N2O diffusion in the soil seem to enhance N2O consumption. However, the factors regulating N2O consumption are not yet well understood and merit further study. Frequent literature reports of net N2O consumption suggest that a soil sink could help account for the current imbalance in estimated global budgets of N2O. Therefore, a systematic investigation into N2O consumption is necessary. This should concentrate on the organisms, reactions, and environmental factors involved.

The Case for Atmospheric Mercury Contamination in Remote Areas

Abstract: Elevated levels of mercury in aquatic environments remote from industrial sources have been broadly attributed to long-range atmospheric transport and deposition of anthropogenic Hg. Evidence in support of this prevailing scientific viewglobal biogeochemical Hg models, sedimentary archives of historic Hg fluxes, and geographic trends in soil Hghave been challenged as being insuf ficiently rigorous to rule out the alternative explanation that natural geologic sources are the principal contributors of Hg in remote locations. In this review, we examine the weaknesses in interpretation and the choice of information that has been used to argue against atmospheric Hg contamination. Analytical advances in measuring trace levels of environmental Hg have greatly narrowed estimates of natural Hg fluxes, providing a clear measure of the relative magnitude of anthropogenic Hg emissions and deposition. Recent experimental results indicate that diagenetic processes cannot explain the mounting number of lake sediment an...

Methane and nitrous oxide fluxes in native, fertilized and cultivated grasslands

Abstract: Measurements of CH4 uptake and N2O emissions in native, nitrogen-fertilized, and wheat-growing prairie soils from spring to late autumn, 1990 are reported. It is found that nitrogen fertilization and cultivation can both decrease CH4 uptake and increase N2O production, thereby contributing to the increasing atmospheric concentrations of these gases.