The chernobyl accident: Air radioactivity measurements in Italy

Summary The data of the air radioactivity collected in the period 26/4–25/5, 1986 after the Chernobyl accident are presented. In particular the network of the sampling stations and the analyses carried out are briefly described. The meteorological situation responsible for the long-range transport of the pollutants from the place of emission to our country is also shown. Then the data of the air radioactivity are discussed and finally some observations on the functioning of the network are done.

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Riassunto Si presentano in questa nota i dati di radioattività dell'aria raccolti nel periodo 26/4–25/5, 1986 a seguito dell'incidente di Chernobyl. In particolare, dopo una breve descrizione della rete che ha effettuato i rilevamenti e delle modalità di campionamento, si analizza la situazione meteorologica responsabile del trasporto dei radionuclidi dal luogo di emissione fino al nostro paese. Si presentano poi i dati relativi alla contaminazione riscontrata nelle varie località. Segue una breve discussione sull'andamento dei dati e si chiude con alcune osservazioni sullo stato della rete e sulla necessità di un suo potenziamento.

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Резюме Приводятся данные по радиоактивности воздуха, собранные в период 26/04–25/05 1986 г. после аварии в Чернобыле. В частности, описываются система станций сбора проб и приведенные анализы. Также рассматривается метеорологическая ситуация, вызвавшая перенос загрязняющих веществ на большие расстояния от места выброса в Италию. Обсуждаются данные по радиоактивности воздуха и анализируются некоторые наблюденния функционирования системы станций сбора проб.

     

Study of the medium- and long-range transport analysing the data of the Chernobyl accident

Summary In the present work we analyse the meteorological factors that characterized the transport and deposition on the ground of the radionuclides from the Chernobyl nuclear power station over Northern Italy during the accident in April–May 1986. The aim of our study is to test some computational procedures and meteorological analyses specific for a comprehensive study of long-range pollution transport problem. By reconstructing the particle trajectories of the radioactive Chernobyl plume, we determined the most probable starting and arrival date of the plume and the level over the source. Moreover, analysis of the meteorological configuration up-and downwind the Alps permitted us to explain the temporal displacement between different kinds of measured fall-out.

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Riassunto Nel presente lavoro si analizzano i fattori meteorologici che hanno caratterizzato il trasporto e la deposizione sull'Italia Settentrionale del materiale radioattivo fuoriuscito dalla centrale nucleare di Chernobyl durante l'incidente di aprile-maggio 1986. Lo studio ha avuto come scopo quello di verificare e mettere a punto procedure di calcolo e di analisi di dati meteorologici finalizzate ai problemi di trasporto d'inquinanti a lunga distanza. La ricostruzione delle traiettorie percorse dalla nube radioattiva ha permesso di determinare la data di partenza e di arrivo piú probabile della nube e l'altezza di livellamento sopra la sorgente. Inoltre considerazioni sulla situazione meteorologica sopra e sottovento le Alpi hanno permesso di spiegare lo sfasamento temporale tra i diversi tipi di fall-out misurati.

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Резюме В этой работе мы анализируем метереологические факторы, которые характеризуют транспорт и оседание на землю радионуклидов в Севертоной Италии после аварии на Чернобыльской АЭС в апреля-мае 1986 г. Цель этой работы проверить некоторые вычислительные приемы и метереологический анализ, предлагаемые для исследования проблем транспорта загрязнений на большие расстояния. Реконструируя траектории частиц радиоактивного выброса в Чернобыле, мы определяем наиболее вероятные данные для выброса и уровня над источником. Более того, анаяиз метереологической ситуации в Альпах позволил объяснить временные смещение мезду различными типами измеренных радиоактивных выпадений.

     

Wind climatology between 950 and 500 hPa over the Mediterranean area above Italy

Summary In order to improve the simulation of wind probability distributions at ground level, eight years of wind data of the multivariate analyses at 850, 700, 500 hPa levels over Italy, and eleven years of wind radiosoundings performed at 5 Italian Air Force stations at 950, 900, 800, 700, 600, and 500 hPa have been processed. The vertical profiles of the distribution parameters of wind speed present predictable behaviour, with the exception of Brindisi. The frequency distribution profiles of the wind directions are more complex. Temporarily seconded to the RISOE National Laboratory (DK) as part of the EEC-DGXII Programme ?Stimulation Action?.     

The precipitation in Italy during the period Autumn 1988–Spring 1990

Summary In Italy the period November 1988–April 1990 shows an anomalous trend of precipitations. Severe drought during the cold season and above normal amounts during summer, in particular in July 1989, was recorded. In this paper an analysis is carried out of this anomaly which explains the phenomenon on the basis of the meteorological patterns, recorded during the two years, and excludes that it could be significant of an eventual climatic change.     

The role of chemical reactions in the Chernobyl accident

It is shown that chemical reactions played an essential role in the Chernobyl accident at all of its stages. It is important that the reactor before the explosion was at maximal xenon poisoning, and its reactivity, apparently, was not destroyed by the explosion. The reactivity release due to decay of Xe-235 on the second day after the explosion led to a reactor power of 80–110 MW. Owing to this power, the chemical reactions of reduction of uranium, plutonium, and other metals at a temperature of about 2000°C occurred in the core. The yield of fission products thus sharply increased. Uranium and other metals flew down in the bottom water communications and rooms. After reduction of the uranium and its separation from the graphite, the chain reaction stopped, the temperature of the core decreased, and the activity yield stopped.     

On the time variation of the surface air temperature in Genoa, Italy

Summary The annual averages of the maximum, minimum and mean daily temperatures measured at the Genoa University Observatory from 1833 to 1986 are examined. All maxima lie between 20.0°C and 17.2°C and the minima between 14.7°C and 11.5°C; while the mean values lie between 17.1°C and 13.2°C. The smallest value of every series was recorded in 1956, the coldest of the last 154 years. The courses show sequences of years with increasing and decreasing temperatures and oscillations with different amplitudes and periods. The time occurrences of the sequences and the sign of the variations agree very well with those observed in many European places while differences concerning the amount of the variations were found. The comparison between the annual mean values of the minima in Genoa and in a rural site (Mt. Cappellino) during the last 30-year period shows a smaller increase of their differences. Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.     

Theory of quasi-biennial and some other oscillations in meteorological parameters

Summary We show that quasi-biennial and several other oscillations in meteorological parameters are caused by ?foldover distortions? in the physical processes represented by the formulations contained in our recent theory. The periods of all these oscillations extend from about 50 days up to over 200 000 years. Additional oscillations within and outside this periodicity range are correspondingly generated primarily as a result of nonlinearities in the earth-atmosphere system. Our analysis agrees quite well with past observations as well as results of analyses on climatic records from different locations on the Earth and can, therefore, be useful in attempts to make climatic predictions as briefly indicated in the text.     

Magnetic and ionospheric effects of the strong magnetospheric storm of March 13th, 1989 over Italy

Summary In March 1989 a series of intense solar events caused relevant effects on the Earth's magnetosphere and ionosphere. Interesting phenomena like exceptional brilliant Auroras, total blackouts of the HF radio links and one of the strongest magnetospheric and ionospheric storms ever recorded in this century, were observed during this month. In this paper the study of the main magnetic and ionospheric effects that occurred before and during the strong magnetospheric storm of March 13th, as they were observed over Italy, is reported. A brief discussion about the magnetic and ionospheric disturbances occurred after a solar flare is also presented. Geomagnetic-field elements from two italian magnetic Observatories (L'Aquila, Castello Tesino) and a temporary magnetic station (S. Nicolò Gerrei) as well as the data scaled from two ionospheric stations (Rome and Gibilmanna) are discussed considering their latitudinal dependence as well as other different site characteristics.     

Characteristics of high-frequency atmospheric eddies over the mediterranean area in different seasons

Summary We examine the properties of atmospheric eddies over Europe and the Mediterranean, as revealed by an analysis of high-pass filtered time series of geopotential height. The data used are seven years of 6-hourly initialized analyses, prepared at ECMWF. The application of a time-filter with cut-off around 6 days allows us to isolate the variability associated with travelling eddies, which generally come from the Atlantic and whose properties (spatial structure, propagation characteristics) are deeply modified when they pass over the Mediterranean region. Different statistical indicators have been derived to reveal these modifications, that are particularly evident in the lower troposphere. It appears that the orography surrounding the Mediterranean region is the main factor influencing eddy behaviour. This conclusion is supported, among other considerations, by the comparison between winter and summer statistics: notwithstanding the different climatological properties of the mean atmospheric circulation and of the surface heat fluxes in the two seasons, some peculiar properties of the high-frequency components over the European and Mediterranean region, such as the vertical and horizontal structure, do not vary much as a function of the season.

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Riassunto Sono esaminate le proprietà dei vortici atmosferici sull'Europa e il Mediterraneo, mediante un'analisi di serie temporali di altezza di geopotenziale, filtrate con un filtro passa alto. I dati utilizzati sono costituiti da sette anni di analisi inizializzate, disponibili ad intervalli di 6 ore, preparate dal Centro Europeo di Previsione Meteorologica a Medio Termine (ECMWF). L'applicazione di un filtro temporale con un periodo di taglio di circa 6 giorni permette di isolare la variabilità associata con vortici viaggianti che generalmente provengono dall'Atlantico e le cui proprietà (struttura spaziale, caratteristiche di propagazione) sono profondamente modificate allorquando essi transitano sopra la regione mediterranea. Sono stati calcolati diversi indicatori statistici allo scopo di rivelare tali modifiche, che sono particolarmente evidenti nella bassa troposfera. L'orografia che circonda la regione mediterranea rappresenta il fattore principale che influenza il comportamento dei vortici. Questa conclusione è rafforzata, fra l'altro, dal confronto tra le statistiche riferite ai periodi invernale ed estivo: nonostante le differenti proprietà climatologiche della circolazione atmosferica media e dei flussi di calore alla superficie durante le due stagioni, alcune proprietà peculiari delle componenti di alta frequenza della circolazione sulla regione europea e mediterranea, quali la struttura orizzontale e verticale, non variano molto in funzione della stagione.

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Резюме Мы исследуем свойства атмосферных вихрей над Европой и над Средиземным морем, которые были обнаружены при анализе фильтрованных временных последовательностей для геопотенциальной высоты. Данные собирались в течение семи лет. Применение временного фильтра с обрезанием в 6 дней позволяет нам выделить изменчивость, связанную с перемещаюимися вихрями, которые обычно приходят из Атлантики и чьи свойства (пространственная структура, характеристики распространения) сильно изменяются, когда вихри проходят над областью Средиземного моря. Используются различные статистические индикаторы, чтобы обнаружить эти изменения, которые наблюдаются в нижней части тропосферы. Оказывается, что орография, окружающая область Средиземного моря, является основным фактором, влияющим на поведение вихрей. Это утверждение подтверждается также сравнением зимней и летней статистик: несмотря на различные климатологические свойства средней атмосферной циркуляции и поверхностных потоков в течение двух сезонов, некоторые свойства высокочастотных компонент над Европой и областью Средиземного моря, такие как вертикальная и горизонтальная структуры, существенно не изменяются в зависимости от сезона.

     

Experimental test of the EEC wind climatology model in a Mediterranean coastal area

Summary The analysis of 18 months of meteorological measurements collected in three stations located in Sardinia (Italy), is presented. The experimental wind distributions for 12 sectors of 30 degrees each have been fitted with the Weibull distribution function. The experimental Weibull parameters have been compared with the ones simulated by using the model produced within the EEC programme ?Wind Atlas for Europe?. Discrepancies between the experimental and simulated wind distributions have been discussed. Time series of the three stations have been compared to study the modification of the characteristics of the air flow from the coast to inland. Statistics of the atmospheric stratification, based on the concept of Pasquill stability classes has been produced by using semi-empirical methods. Further developments have been suggested.     

Spectral characteristics of wind and air pollution data in an industrial area

Summary A comparison is made between the spectral features of sulfur dioxide concentration and zonal and meridional components of wind speed over a highly industrialized area situated on the coast. The paper focuses on the characteristic times of the meso-synoptic scale. Diurnal and longer period oscillations were identified. Variations of ground-level SO₂ concentrations are attributed to local sea-breeze circulation and to the synoptic weather period of wind speed.     

Measurements of134Cs and137Cs by gamma spectrometry in some Italian soils following the nuclear reactor accident of chernobyl

Summary The concentration as well as the vertical distribution of¹³⁴Cs and¹³⁷Cs were determined in several soil samples subsequently to the Chernobyl accident. The soil samples were selected in some representative geomorphological situation in Apulia that is a region of Italy. Both undisturbed and cultivated soils were considered. The total deposition of¹³⁷Cs as due to the Chernobyl accident was estimated and the obtained results were also controlled by measurements of the radioactive fall-out in rain and snow during 1986 and 1987. Also the deposition of^239,240Pu during 1986 and 1987 was measured.

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Riassunto è stata determinata la concentrazione e la distribuzione verticale, di¹³⁴Cs e¹³⁷Cs in alcuni campioni di terreno successivamente all'incidente di Chernobyl. I campioni sono stati selezionati in alcune situazioni geomorfologiche rappresentative della Puglia. Sono stati presi in considerazione sia terreni indisturbati che coltivati. è stata determinata la deposizione totale di¹³⁷Cs dovuta all'incidente di Chernobyl. Questo risultato è stato valutato anche in relazione alle misure di ricaduta di¹³⁷Cs nella pioggia e nella neve durante l'ultimo quadrimestre 1986 e il 1987. Per la medesima ricaduta è stato anche misurato il^239,249Pu.

     

Observations and simulations with linked numerical PBL and air pollution models and a Gaussian model under low wind speed conditions: a case study of the urban-industrial Linz area

Summary A one-week-long field study was carried out to investigate dispersion conditions and SO₂ patterns under low wind speed conditions in the industrial city of Linz. Meteorological fields generated with the URBMET PBL model were used as input for a 28 hour simulation of the SO₂ concentrations with a Eulerian model. Results were compared with the operational Gaussian model of the Austrian meteorological service. On the basis of balloon soundings at two sites, horizontal temperature profiles evaluated from car trips and the stationary observational network wind, temperature and SO₂ patterns were analysed and used to evaluate model results. Paper presented at the GNFAO/EURASAP Meeting, Turin, September 1989. To speed up publication, proofs were not sent to the authors and were supervised by the Scientific Committee.     

The global carbon cycle change: Le Chatelier principle in the response of biota to changing CO2 concentration in the atmosphere

Summary The long-term existence of natural biota in the environment means that such a system is stable with respect to external disturbances. This system must follow the Le Chatelier principle which is based on the processes that compensate the disturbing effects. The use of the Le Chatelier principle makes it possible to choose between contradictory observational data. Available observational data on variations of the concentration of rare carbon isotopes in various media show that the oceanic biota follows the Le Chatelier principle and absorbs about half the carbon which the ocean gets from the atmosphere, compensating an increment of carbon in the atmosphere caused by an anthropogenic impact. The strongly anthropogenically disturbed land biota does not follow the Le Chatelier principle, starting from the middle of this century. The land biota not only cannot absorb excess carbon accumulated in the atmosphere: it ejects carbon to the atmosphere in quantities equal to halved emission of carbon through fossil fuel burning. All the quantitative results considered in the paper have been obtained without using models of the biota and of the ocean.     

Two-dimensional distributions of sulfur compounds in the troposphere: Implications for the atmospheric sulfur budget

Summary We have built a two-dimensional model of the lower atmosphere extending from pole to pole and from the ground to about 20 km. Meridional circulation is obtained from observational data of vertical velocity and is made self-consistent for the meridional velocity through the use of the continuity equation. Eddy processes are parameterized in terms of eddy diffusion coefficients. Results are reported for OCS, CS₂, H₂S, CH₃SCH₃, SO₂ and compared both with available experimental data and other similar calculations. Our results show a general agreement with both concentrations and fluxes. Production of SO₂ takes into account both natural and anthropogenic sources. An interesting result is found for OCS which seems to have a net chemical production in the troposphere. A possible role of OCS as a stratospheric sulphur source should be reconsidered. Paper presented at the 1° Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.     

Experimental study of radioactive aerosols in the vicinity of the Chernobyl Nuclear Power Plant

Study of radioactive aerosols in the relocation zone and in the populated areas have been carried out for a number of years. The experiments on modelling resuspension were performed while conducting agricultural work. Nuclear track radiography and alpha spectrometry with radiochemical extraction of plutonium were used as analytical methods for the determination of the transuranium elements contents. The distributions of radioactive particles were obtained as to activity and sizes. Specific activity of “hot particles” increases with decreasing diameter. In aerosols selected at a distance of more than 10 km from the Chernobyl NPP pure fuel particles with sizes of more than 5 μm were not found. The activity of the finely dispersed fraction of aerosols, which is more dangerous when inhaled by the organism, is comparable with a total activity of large particles.     

Recent developments in the theory of orographic cyclogenesis: Impact of orographic modifications on statistical properties

Summary Recent developments in the normal mode theory of lee cyclogenesis are presented. The topographic modifications of the most unstable eigenmode are computed in the most general case of primitive equations and isolated topography. The basic state about which linearization is performed is a midlatitude jet with maximum speed at tropopause level. The orographic modification consists in a pressure dipole scaling on the Rossby deformation radius already found in previous theoretical and numerical studies. The modifications of the statistical properties introduced by topography on the nonlinear feedback between zonal wind and transient waves are determined using a simple quasi-geostrophic two-layer model. Systematic differences are found to be consistent with the predictions of linear theories. A brief discussion on the limits of the linear theory is also included Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.     

Atmospheric CO2 and destructivity of the land biota: Seasonal variations

Summary The seasonal variations of the carbon content in the ocean are shown to be small as compared to those taking place in the atmosphere. Atmospheric meridional mixing is not intense enough to compensate for the variations of the atmospheric CO₂. If we assume meridional mixing to be zero, then the seasonal variations of carbon in the atmospheric column should be equal to those of carbon in the continental bionass but opposite to them in sign. This latter value is essentially the difference between productivity and destructivity of the land biomass Productivity of humid areas at any latitude is proportional to the diurnal mean solar radiation flux at that latitude. In the present study the temporal variations of this flux are harmonically approximated. Further, an harmonic approximation is found for expressing the temporal course of biomass destructivity at various latitudes. Productivity/destructivity oscillations appear to be almost in couterphase but amplitudinally close to each other.

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Riassunto Le variazioni stagionali del contenuto di carbonio nell'oceano sono piccole rispetto a quelle che si verificano nell'atmosfera. Il mescolamento atmosferico meridionale non è abbastanza intenso da compensare le variazioni del CO₂ atmosferico. Se si ammette che il mescolamento sia zero, le variazioni stagionali del carbonio nella colonna atmo-sferica dovrebbero essere uguali a quelle del carbonio nella biomassa continentale ma opposte a queste ultime come segno. Quest'ultimo valore è essenzialmente la differenza tra la produttività e la distruttività nella biomassa terrestre. La produttività delle aree umide ad ogni latitudine è proporzionale al flusso di radiazione solare diurno medio a quella latitudine. In questo studio si approssimano armonicamente le variazioni temporali di questo flusso. Inoltre si trova un'approssimazione armonica per esprimere l'andamento temporale della distruttività della biomassa a varie latitudini. Le oscillazioni di producttività/distruttività sembrano quasi in controfase ma prossime l'una all'altra per quanto riguarda l'ampiezza.

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Резюме Показано, что сезонные изменения содержания углерода в океане малы по сравнению с изменениями в атмосфере. Меридионаляное перемешивание атмосферы не успевает выравнивать атмосферные колебания CO₂. В приближении нулевого меридионляного перемешиваиия сезонные колебания содержания углерода в атмосферном столбе равны по величине и противололожны по знаку изменению содерзания углерода в континентальной биомассе, иоторое равно разности продуктивности и деструктивности. Продуктивность гумидных областей на разных широтах пропорционаляна среднесуточному потоку солнечной радиации на зтих широтах. В работе найдено гармоническое привлижение для изменения во времени последних величин. С помощью зтих данных определено гармоническое приближение для поведения во времени деструктивности на ражных широтах. Колебание продуктивности и деструктивности оказались происходящими почти в противофазя с близкими по величине амплитудами.