SCENARIO W (Supplement v.2) Responses to the comments of participants 10 August 2005

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1 SCENARIO W (Supplement v.2) Responses to the comments of participants 10 August 2005 VALIDATION OF ENVIROMNEMTAL MODELS USING DATA FROM CHERNOBYL AIR POLLUTION IN THE MAZOVIA AREA Pawel Krajewski Central Laboratory for Radiological Protection Konwaliowa St.7, 93 Warsaw, Poland krajewski@clor.waw.pl The material in this document has been supplied by the contributors and has not been edited by the IAEA. The views expressed remain the responsibility of the named authors and do not necessarily reflect those of the government(s) of the designated Member State(s). In particular, neither the IAEA nor any other organization or body sponsoring the Project can be held responsible for any material reproduced in this document.

2 Introduction Te following chapters presents a summary of comments and remarks to the first draft of SCENARIO W (VALIDATION OF ENVIROMNEMTAL MODELS USING DATA FROM CHERNOBYL AIR POLLUTION IN THE MAZOVIA AREA) that have been formulated during the June and July period from participants of IWG. The questions from participants are in italic. The responses of the Scenario W authors are presented in blue color characters. This material has been prepared for the discussion on IWG meeting in Warsaw (29, 30, 31 August).

3 1 General comments 1.1 The data on volumetric concentration 137 Cs and 131 I in a cloud above only Warsaw are given in the initial data. Volumetric concentration 137 Cs and 131 I in a cloud above places of measurements 131 I in a grass, milk and a thyroid are not present. Deposition in Mazovia was basically dry. The additional information on which it would be possible to reconstruct volumetric concentration 131 I in a cloud above places of measurements is necessary for realization of calculations of activity 131 I in a grass, milk and a thyroid in places of measurements. It is 137 Cs density deposition in specific localities The data of 137 Cs data in soil indicate on rather constant 131 I concentration over Warsaw area, the two spots of elevated 137 Cs concentration in soil (Brwinow, Wolomin) are strongly correlated with reported local rains on 30 April Regarding Ostroleka area no rains were observed in the critical 29, 30 April 1986 and 137 Cs density is rather similar to the around Warsaw dry regions (about 4-5 kbq/m2). 1.2 Model of a homogeneous cloud above Mazovia. Volumetric activity 137 Cs in a cloud and 137 Cs density deposition in specific localities of measurements are used to restore effective rain intensity in places of measurements (there the rain are absent). Further, on identical 131 I volumetric activity in a cloud above all Mazovia and to the reconstructed rains in places of measurements it is possible to calculate 131 I density deposition, 131 I activities in a grass, in milk and a thyroid. One could notice that the rains that occurred on 30 April were as short local showers and it had no remarkably influence on contamination of whole Mazovia region. 1.3 Model of a non-uniform cloud above Mazovia. 137 Cs density deposition in places of measurements is used to restore 137 Cs activity above places of measurements. Volumetric activities of iodine in a cloud above places of measurements are reconstructed in the assumption of constant a 131 I/ 137 Cs ratio and iodine forms ratios in all cloud above all Mazovia. Reconstructed volumetric activities 131 I in a cloud above places of measurements are used to calculate 131 I density deposition, activity 131 I in a grass, in milk and a thyroid. The differences in 137 Cs deposition are less than factor three whereas other factors as pasturing ban or ban of consumption of contaminated food as well as iodine tablets might have greater effect. 1.4 Whether it is possible to make the assumption, that fallouts 131 I in all counties of theirs areas were same, as well as in the area centers? In Table 4 of this supplement one can find estimation of 137 Cs deposition in the particular counties. Only counties pruszkowski, grodziski mazowiecki and warszawskizachodni have 137 Cs deposition about two fold higher than remained area. It would not affect contribution to the average 131 I concentration in milk from the other counties. But one could be careful when estimates uncertainty ranges.

4 The 131 I concentration in soil samples collected in Warsaw from the same place during the period Whether it would be possible to recalculate data given in (TABLE ) The 131 I concentration in soil samples collected in Warsaw from the same place during the period in kbq/m 2 units. See paragraph 7 on page 11. You can use factor kg/m 2 but description of sampling method in this case is not very firm Cs content in soil in Mazovia region [kbq m -2 ] calculated on 1986 (TABLE ) How ground probes were selected? On the selected ground the grass grew or it there was only a pure (clean) ground? See paragraph 4 page 10. The samples were collected from so called meteopost gardens where only lawn grass is growing. 1.7 There is no information for location of Falenty diary in ScenarioW The location of Falenty diary is shown on Figure of Scenario W, but to facilitate calculation it is shown on figure below. e Location of Falenty Diary. About 2.5 km from Warsaw-Okecie Airport. Sampling points and 137 Cs deposition are presented.

5 1.8 Whether the dose from the inhalation should be the same from the two different area (Warsaw, Ostroleka area) or different because of various I-131 air concentrations for these areas. When one looks for Cs-137 deposition for Mazovia region, deposition seems to be rather uniform in exception of two places when was small local rains at 30 April 1986,on the other hand one could reconstruct I-131 concentration base on some trajectories and get different inhalation dose but the factor should be less than 2. Unfortunately, there are no data to check such approach e.g. no air measurements for Ostrołeka area, and no I- 131 concentration in grass (only milk and thyroids). 1.9 One could assess that the largest contribution (70-80 %) to the thyroid contamination comes from vegetables (lettuce) consumption. It might be that the intake of lettuce is overestimated. One can use the Table (page 31) and multiple the annual averaged by a factor of 2, because May is a typical fresh vegetable-season. Is it correct? The consumption of leafy vegetables had no big influence to the thyroid content, but it is worth comparing the I-131 thyroid burden with and without lettuce consumption. It was difficult to assess real situation in Poland, but due to the government warning, most of the people do not eat fresh lettuce during the first to weeks of May or some of them wash lettuce very carefully. From I-131 thyroid content measurements it was not possible to see apparent correlation between people eating or not eating fresh lettuce. Base on some information: most of the parents did not give lettuce for children. Therefore, milk gave more contribution. Of course, one could use the wider uncertainty ranges. 2 Ad. TABLE Selected agricultural information by counties 2.1 What is the yield productivity of meadows and pastures? Base on data of Central Statistical Office one can assume the average yield of grass for MAZOWIA region equal to kg m -2. There are no remarkable differences during the years among other neighbor regions Table 1, Figure 1. The yield of the pasture for intensively cultivated areas (nutrition usage) is less important because these areas are harvested (three times per year) for winter pasture storage Table 2.

6 Table 1. Average yield of grass (kg m -2 ) extensively cultivated in the particular regions of Poland Yield of grass (dry mass) meadows (extensively cultivated) REGION Average SD [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] ŁÓDZKIE MAZOWIA PODLASKIE WARMIŃSKO-MAZURSKIE TOTAL Table 2. Average yield of grass (kg m -2 ) intensively cultivated in the particular regions of Poland Yield of grass (dry mass) pasturing land (intensively cultivated) REGION Average SD [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] [kg/m 2 ] ŁÓDZKIE MAZOWIECKIE PODLASKIE WARMIŃSKO-MAZURSKIE TOTAL Figure 1. MAZIOWA region and neighboring regions specified in Table 1 and Table 2.

7 3 AD charter Climatic conditions 3.1 What was the temperature during previous months that could have effect on vegetation development? Table 3. Average daily temperature and total daily precipitation measured by meteorological stations in Warsaw and Ostroleka towns in the period 1 march 30 may Location of Meteorological Station is shown on Figure 3. (Institute of Meteorology and Water Management data). Average daily temperature C Total daily precipitation [mm] DATE N# 285 N# 375 Warszawa N# 285 N# 375 Warszawa DATA Ostrołeka Okecie Ostrołeka Okecie #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D!

8 Table 3. (cont) Average daily temperature and total daily precipitation measured by meteorological stations in Warsaw and Ostroleka in the period 1 March 30 May 1986 (Institute of Meteorology and Water Management data). Average daily temperature C Total daily precipitation [mm] DATE N# 285 N# 375 Warszawa N# 285 N# 375 Warszawa DATA Ostrołeka Okecie Ostrołeka Okecie #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D! #N/D!

9 Figure 2. Localization of Warsaw town area and Ostroleka area in the Mazovia province In 1986 there was rater warm spring with temperature above 15 C and it intensifies pasture grass growing (see Figure 3). Average Daily Temperature 1986 N# 285 Ostrołeka N# 375 Warszawa Okecie o C DATE Figure 3. Average daily temperature in 1986 in Mazovia area

10 4 AD. Table Rainfall records during the period 26 April - 15 May 1986 in Mazovia province 4.1 It is necessary to specify the nearest settlement to meteopost with the data of 137 Cs density fallout. The soil sampling and measurements of 137Cs content in soil started in Soil samples were taken in the meteorological posts gardens, therefore the Location in the first column of TABLE of Scenario W ( 137 Cs concentration in soil) is directly related to the meteopost. 4.2 Sampling methods The soil samples for further laboratory analyses were collected in 1988, 1989, 1990, 1992, 1996, 1998 and 2000 in the network of the fixed sampling sites which are located at the stations of the Institute of Meteorology and Water Management (the meteorological posts gardens). At the beginning there were 340 points located all over Poland but recently the number of them was reduced to 255. In the same sites, measurements of the gamma radiation dose were performed. The investigations are performed in the frame of the Polish environmental monitoring system and used for the all-country computerised radiological database and for a set of radiological maps of Poland. The soil samples are collected in undistributed areas without sheltering, vegetation (only grass) or structures. Each sample is taken by a knife-edge pipe of 2 inch diameter from 10 cm thick surface layer at seven places. Six of them are situated at the circumference of the circle of 2 m radius and one in the centre of the circle. At the laboratory the soil samples are dried at the room temperature first and than in ovens at temperature not exceeding 105 o C. The dried material is crushed to obtain homogeneous sample and put in a standard container of 0.5 l Marinelli beaker type. The measurements of radionuclide concentrations in soil samples are made using gamma spectrometric GENIE 2000 system with HPGe detectors located in lowbackground lead shielding chambers. The chambers reduce the external gamma radiation background by two orders of magnitude. The time of each measurement is s. Additionally in a frame of other projects determination of 137 Cs soil content was determined using 13 cm diameter and 30 cm core samplers. the averages of 137 Cs deposition in counties that contributed to the diaries in Warsaw and Ostroleka area are presented in Table 4. One needs to remark that for several counties no direct measurements of 137 Cs in soil were performed. In these cases the standard (IDW Inverse Distance Weight) interpolation from neighboring points was applied. Moreover, the counties borders are set for administrative reasons and cover areas of inhomogeneous deposition of 137 Cs (see Figure 4). This heterogeneity resulted mainly from local rains that occurred on 30 April 1986 and more intensive precipitations during 8-10 May On the other hand there are only two recorded spots of elevated 137 Cs content in soil in Mazovia region (see Figure 4) and overall average equal to kbq/m 2, where 1.5 kbq/m 2 is a Standard deviation of single value and can be considered as quantifier of uncertainty ranges.

11 5 AD Chapter ISOTOPIC COMPOSITION OF DEPOSITION ( 131 I/ 137 Cs) 5.1 Organic deposition velocity assumed in evaluation? Organic 131 I deposition velocity was taken equal to m s Cs deposition velocity? It was assumed that 137Cs deposition velocity is the same as iodine bound to aerosols. 6 Ad Chapter Cows pastured limitation 6.1 Mean 137Cs density fallout in county? See comments to Table page 10 7 AD Chapter I and 137 Cs concentration in soil AD. Table The 131 I concentration in soil samples collected in Warsaw from the same place during the period How to calculate Bq/kg to Bq/m 2? According to the sampling records the soil samples were taken from the area of 25 cm 20cm and 10cm, and soil has been dried at the room temperature and put in a standard container of 0.5 l Marinelli beaker type. The measurements of radionuclide concentrations in soil samples are made using gamma spectrometric system with HPGe detectors located in low-background lead shielding chambers. Assuming soil bulk density of g cm -3 the factor might be kg/m 2 8 Ad Chapter I concentration in milk samples 8.1 There is possible to obtain the 137 Cs density fallout for specified locality with milk and thyroid measurements? The average 137 Cs concentration measured in Warsaw-Okecie meteopost 2.5 km from Falenty diary was about 4 kb/m2, therefore close to the average of Mazovia area. Regarding milk measurements in diaries in Warsaw and Ostrołeka town 2.5 km as well as in several other locations there is no apparent correlation between 137 Cs density and measured 131 I in milk.

12 Table 4. Assessment of 137 Cs deposition in the particular counties of Mazovia region [kbq m -2 ] 1 Delivery area Estimated deposition of 137 Cs in county kbq/m 2 Measurements of 137 Cs kbq/m 2 WARSAW grodziski mazowiecki 8.6 WARSAW grojecki 4.2 WARSAW legionowski 4.1 WARSAW minski 4.5 WARSAW nowodworski mazowiecki 3.8 WARSAW otwocki 4.9 WARSAW piaseczynski 4.8 WARSAW pruszkowski 8.4 WARSAW pultuski 3.6 WARSAW warszawski 4.5 WARSAW warszawski zachodni 6.7 WARSAW wolominski 5.7 WARSAW wyszkowski 4.5 County Mean SD Min Max Meteo post location measured value Location (additonal measurements) measured value No meteopost NDM 3 9 No meteopost NDM 3 7 Legionowo 4.5 NDM 4 5 No meteopost NDM 2 6 No meteopost Wilkow Nowy 3.2 Świder 4.0 NDM 4 10 No meteopost NDM Brwinow 10.8 Brwinow bis 22.7 Warszawa-Okęcie 4.0 NDM Pułtusk 3.9 NDM 3 6 Warszawa-Obs.Astr. 3.3 NDM No meteopost NDM No meteopost Wolomin town 11.2 Wolomin town bis Niegów 3.7 NDM Overall average NDM NDM OSTROLEKA kolnenski No meteopost NDM OSTROLEKA lomzynski Marianowo 1.8 NDM OSTROLEKA makowski No meteopost NDM OSTROLEKA ostrolecki Myszyniec 5.2 Goworowo 5.5 OSTROLEKA OSTROLEKA Ostroleka 3.1 NDM OSTROLEKA piski Mikołajki 6.8 NDM OSTROLEKA przasnyski No meteopost NDM OSTROLEKA szczycienski Szczytno 5.1 NDM OSTROLEKA zambrowski No meteopost Szumowo 6.5 Overall average All 137 Cs values calculated on 26 April 1986

13 Figure 4. Assessment of 137 Cs deposition for MAZOVIA region. (Blue numbers present the sampling points and measured 137 Cs soil content (kbq/m2).