Low-frequency variability of beryllium-7 surface concentrations over the Eastern Mediterranean

Gerasopoulos, E.; Zerefos, C. S.; Papastefanou, C.; Zanis, Prodromos; O’Brien, K.

doi:10.1016/s1352-2310(03)00068-2

Cited by 59 publications

(37 citation statements)

References 28 publications

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“…Together with previously known results from (10) and (12), the above expression completes the formulae that relate A F (T S ) and a(t)=a 0 for the profiles of φ(t) that have, to our knowledge, been reported so far for the sampling of air in radioactivity studies.…”

Section: Example 3: A(t) Is Constant While φ(T) Decreases Linearlysupporting

confidence: 78%

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Air sampling by pumping through a filter: effects of air flow rate, concentration, and decay of airborne substances

Šoštarić

Petrinec

Babić

2016

Archives of Industrial Hygiene and Toxicology

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This paper tackles the issue of interpreting the number of airborne particles adsorbed on a filter through which a certain volume of sampled air has been pumped. This number is equal to the product of the pumped volume and particle concentration in air, but only if the concentration is constant over time and if there is no substance decomposition on the filter during sampling. If this is not the case, one must take into account the inconstancy of the concentration and the decay law for a given substance, which is complicated even further if the flow rate through the filter is not constant. In this paper, we develop a formalism which considers all of these factors, resulting in a single, compact expression of general applicability. The use of this expression is exemplified by addressing a case of sampling airborne radioactive matter, where the decay law is already well known. This law is combined with three experimentally observed time dependences of the flow rate and two models for the time dependence of the particle concentration. We also discuss the implications of these calculations for certain other situations of interest to environmental studies. KEY WORDS: air sampling filters; particle concentration; radioactivity; substance decompositionAir sampling for the purpose of determining the concentration (n) of an airborne substance is frequently carried out by pumping air through a sampling filter. The filter is subsequently subjected to an appropriate analysis and n should then be calculated from observables such as the volume (V) of the pumped air and the number (N F ) of the substance atoms or molecules adsorbed on the filter. The formula n=N F /V is valid only if n is constant during the sampling and the substance remains stable after it has been deposited onto the filter, which is not always the case (e.g., because of a radioactive decay or a spontaneous chemical decomposition). Generally speaking, one often has to develop a specific model for interpreting the relation between n, N F , and V rather than rely on the abovementioned simple ratio. For instance, a common outcome of such modelling is the correction to the calculated n (which is assumed to be constant) of a radioactive substance that has the half-life T 1/2 of the order of the sampling time T S (1). The situation may become even more complicated if the flow rate φ through the sampling filter also changes over time t, as demonstrated in the case of an exponentially decreasing φ(t) (2). Hence, inconstant n(t) and/or φ(t), as well as the decay of substances on the filter, cause deviations from N F =nV, which should not be neglected.In this paper, we develop a formalism that accounts for the interpretation of N F (T S ), which is N F at the end of a sampling at t=T S , in situations when a substance of interest decays over time, while either (or both) n(t) and φ(t) may be inconstant during the sampling. The profile of φ(t) is determined by the characteristics of a particular sampling system (e.g., reduction of filter porosity as the adsorption progr...

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Section: Example 3: A(t) Is Constant While φ(T) Decreases Linearlysupporting

confidence: 78%

“…A good example of an application of Eq. [10] is the routine monitoring of 7 Be (T 1/2 =53.4 days) when T S is about a few weeks (5-7). If T 1/2 >>T S , Eq.…”

Section: Example 1: Both A(t) and φ(T) Are Constantmentioning

confidence: 99%

Air sampling by pumping through a filter: effects of air flow rate, concentration, and decay of airborne substances

Šoštarić

Petrinec

Babić

2016

Archives of Industrial Hygiene and Toxicology

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“…Nevertheless, the percentiles chosen are related to full-year statistics and, thus, the results are less influenced by short-term variations than those by Elbern et al (1997). A one-year period is sufficiently short in comparison with known periodicities in surface 7 Be (Reiter et al, 1983;Koch and Mann, 1996;Gerasopoulos et al, 2003) in order to account for their influence.…”

Section: Discussionmentioning

confidence: 99%

Forecasted deep stratospheric intrusions over Central Europe: case studies and climatologies

et al. 2010

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Abstract. Based on daily predictions of stratospheric air intrusions, obtained from trajectory calculations by ETH Zürich with wind fields from ECMWF forecasts, a high number of measurements with the ozone lidar at IMK-IFU (Garmisch-Partenkirchen, Germany) were carried out in 2001. The lidar measurements show a large variety of rather different cases reflecting the full complexity of intrusion episodes that is not visible in classical case studies. In part, tropopause folds could be fully captured. The frequency of intrusion cases forecasted and verified by vertical sounding or in the in-situ data recorded at the nearby Zugspitze summit (2962 m a.s.l.) exceed that in previous work by more than a factor of two. Three cases mapped with the lidar were selected to validate the results for the corresponding time periods extracted from a one-year run with the new hemispheric version of the chemistry-transport model EURAD. Due to the high spatial resolution chosen for these simulations the agreement with the lidar measurements is satisfactory. The Zugspitze ozone data from 1978 to 2004 were recently filtered by applying different criteria for stratospheric air, based on the 7 Be and humidity measurements. Here, by using the daily model forecasts during the time period 2001-2005, we examine three criteria and determine how well they represent the stratospheric air intrusions reaching the mountain site. Seasonal cycles for the period 2001-2005 were derived forCorrespondence to: T. Trickl (thomas.trickl@kit.edu) the forecasts as well as the intrusion frequency per month for the forecasted intrusions and each of the criteria, distinguishing eight different characteristic transport pathways. In most cases a winter maximum and a summer minimum was obtained, but in the case of cyclonic arrival of intrusions starting over Greenland a late-spring maximum is seen. Two of the filtering criteria examined, based on combining a relativehumidity (RH) threshold of 60% with either a 7 Be threshold of 5.5 mBq m −3 or the requirement for RH≤30% within ±6 h, rather reliably predict periods of deep intrusions reaching the Zugspitze station. An "or" combination of both these criteria yields slightly more cases and covers 77.9% of the intrusions identified. The lack of observations in the complementary 22.1% are mostly explained by overpasses. In this way the long-term trend of stratospheric ozone observed at this site as well as the corresponding ozone budget may be derived on the basis of measurements only. This effort will be the subject of a subsequent publication.

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“…Concentrations of 7 Be in air at midlatitudes exhibit maxima in spring/summers periods attributed to seasonal thinning of tropopause that allows stratospheric masses rich with 7 Be to enter the troposphere (Agelaio et al, 1984;Bettoli et al, 1998;Cannizzaro et al, 1995;Hirose et al, 2004;Ioannidou & Papastefanou, 1997;Todorovic, 1997). Concentration of 7 Be in air is effected by air exchange between stratosphere and troposphere, vertical mixing within the troposphere and the washout effects (Todorovic, 1997;Gerasopoulos et al, 2003). 210 Pb (half life 22.3 years) is produced in the decay of 238 U into gaseous 222 Rn (half life 3.8 days) that escapes from soils into the atmosphere where one of its short lived daughters ( 218 Po) decays into 210 Pb (Gaggelar, 1995;Gaffney et al, 2004;Groundel & Postendourfen, 2004;Todorovic et al, 2000).…”

Section: Air Radioactivity Monitoringmentioning

confidence: 99%

Air Radioactivity Monitoring in Serbia

Popović¹,

Todorović²,

Jokic³

et al. 2008

Environmental Technologies

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Low-frequency variability of beryllium-7 surface concentrations over the Eastern Mediterranean

Cited by 59 publications

References 28 publications

Air sampling by pumping through a filter: effects of air flow rate, concentration, and decay of airborne substances

Air sampling by pumping through a filter: effects of air flow rate, concentration, and decay of airborne substances

Forecasted deep stratospheric intrusions over Central Europe: case studies and climatologies

Air Radioactivity Monitoring in Serbia

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