Export of 134Cs and 137Cs in the Fukushima River Systems at Heavy

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Climate , and Sciences Sciences Dynamics 4 Chemistry of the Past Solid Earth Techniques Geoscientific Methods and and Physics and Atmospheric Atmospheric Atmospheric Data Systems Geoscientific Earth System Earth System Measurement Instrumentation Hydrology and Ocean Science Annales Biogeosciences The Cryosphere Natural Hazards Natural Hazards and Earth System and Earth Model Development Geophysicae Cs in river waters was 0.011– Cs by the heavy rain accounts , K. Fukushi 3 137 137 Cs in the Cs and Cs and Cs coupled with wind direction and precipi- .kanazawa-u.ac.jp) ﬀ 137 2768 2767 134 Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access 134 137

, S. Tomihara 1 Cs were 21–56 % in the normal flow condition, but 137 Cs and Climate Sciences Sciences Dynamics 134 Chemistry of the Past Solid Earth Techniques Geoscientific Methods and and Physics and Advances in , S. Ochiai Atmospheric Atmospheric Atmospheric Data Systems Geoscientific Geosciences Cs and 2 Earth System Earth System Measurement Cs and Instrumentation Hydrology and Ocean Science Biogeosciences The Cryosphere 134 Natural Hazards Natural Hazards EGU Journal Logos (RGB) EGU Journal Logos and Earth System and Earth 134 Model Development in high flow conditions by heavy rains occurring with the typhoon. The 1 Cs reveals considerable external radioactivity in a zone extending north- at normal flow conditions during July–September in 2011, but it increased 1 ) was also found in the Naka-dori region. The deposition pattern is ex- − 1 2 137 , M. Kanamori − − 1 Cs was released from the NPPCs as and a result of venting operations and hydrogen ects of a heavy rain event on radiocesium export were studied at stations on ff This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Aquamarine Fukuhsima, Onahama, Iwaki, FukushimaDivision 971–8101, of Japan Earth Dynamics, Institute of Nature and Environmental Technology, Kanazawa tation (Morino et al., 2011). after the137 2011 Tohoku earthquake andexplosions tsunami. (Japanese About Government,134 2011; 15 Chino PBq et of al.,west both 2011). from Surface the deposition NPP,the of about NPP 20 km (MEXT, 2011; wide600 kBqm Yoshida and and 50–70 Takahashi, km 2012).plained long Moderate by inside emission radioactivity rates the (100– of 80 km zone of coastal marine environments. 1 Introduction A nuclear accident at the Fukushima Daiichi Nuclear Power Plant (NPP) occurred 0.098 Bq L to 0.85 Bq L particulate fractions of were close to 100 %radiocesium associated after with the suspended typhoon. particlesby These from the land results heavy to indicate coastal rainfor that ocean 30–50 event. occurred the % Export of pulse annual flux inputfactor radiocesium of of flux controlling in the 2011. transport Results and show dispersion that rain of events radiocesium are in one river watersheds and E the Natsui River andRoke the during Same 21–22 September River 2011,Power in six Plant Fukushima months Prefecture, accident. after Japan the Radioactivity after Fukushima of Typhoon Daiichi Nuclear Abstract Biogeosciences Discuss., 10, 2767–2790, 2013 www.biogeosciences-discuss.net/10/2767/2013/ doi:10.5194/bgd-10-2767-2013 © Author(s) 2013. CC Attribution 3.0 License. Fukushima river systems at heavyby rains Typhoon Roke in September 2011 S. Nagao M. Yamamoto 1 Kanazawa University, Nomi, Ishikawa2 923–1224, Japan Kanazawa, Ishikawa 920–1192, Japan 3 4 University, Kakuma, Kanazawa, Ishikawa 920–1192, Japan Received: 31 December 2012 – Accepted: 15Correspondence January to: 2013 S. – Nagao Published: (nagao37@sta 15 FebruaryPublished 2013 by Copernicus Publications on behalf of the European Geosciences Union. Export of 5 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ´ en Cs 134 Cs have Cs in river 137 137 : MEXT, 2011) to 2 Cs and − Cs in river systems 134 Cs and 137 for the Natsui River and . That of the Same River 134 2 1 − Cs has decreased markedly s 100 kBqm 3 137 < Cs and 134 Cs in river waters at two rivers after the Cs in river waters was also found in the cient, which is the ratio of maximum /mini- 137 137 ffi 2770 2769 Cs shows little change from upstream to down- 137 Cs and Cs and 134 134 Cs derived from fallout increased at high flow conditions in the Kuji ects of rain events on export of radiocesium from land to ocean in the 137 ff for the Same River (Fukushima Prefectural Government, 2012). The water . The Natsui River length is 67 km. That of the Same River is 58 km. The 1 2 − s Cs from selected soil samples has indicated that both radionuclides in the soil 3 137 The sampling location is presented in Fig. 1. This study investigated Natsui River and This study was conducted to investigate the transport of To elucidate the short-term to long-term impacts of the Fukushima Daiichi NPP ac- A major part of radiocesium deposited on the ground surface is present at the sur- 21.4 m discharge data are presented in Fig. 2. River water samples (10–20 L) were collected Iwaki city, located in thethe southern Natsui coastal River. This regionfor of value 1981–2010: Fukushima is JMA, and about 2012). in one-tenth a of watershed the of annual meanSame River rainfall flowing (1409 through mm a less-contaminatedthe area Pacific ( coast. The Natsuiis River watershed 600 km area is 749annual km mean water discharge data in 2011 were 17.6 m Typhoon Roke (T1115) struckto Japan an on extra-strong 21 tropical Septemberprecipitated cyclone and on more 22 subsequently than September weakened 400(JMA, 2011 mm 2011). (JMA, Fukushima of Prefecture 2011). had rain The rainfallber. daily of The typhoon 100–200 daily in mm rainfall during parts on 15–22 21 Septem- of September was eastern 137 mm and by western the impact Japan of Typhoon Roke at toring results of radioactivityheavy of rain event by aat typhoon the in Natsui September River 2011. andJapan. Field the We experiments Same discussed were River conducted transport infrom behavior the inland of southern to radiocesium part coastal and of areas. estimated Fukushima Prefecture, its export flux 2 Materials and methods were formulated as ato function evaluate of e the waterFukushima discharge area. rates. Therefore, it is important systems in Fukushima Prefecture after rain events. This report describes the moni- suspended and dissolved form concentrations of elements in the Kuji River waters River because of rain events. Nagano et al. (2003) pointed out that variations of cident on ecosystems ofernment river has and been coastalin monitoring marine Fukushima environments, the Prefecture the radioactivity (MEXT, Japaneseriverbed of 2012b). slope, Gov- and Japanese high riversmum river have discharge regime a (Suetsugu, coe 2005). short Annualing length, mean 1971–2000 precipitation high was because high, ofmelting 1718 mm events “tsuyu” dur- in (the spring rainydioactivity (MLTI, season of 2012). in Matsunaga Japan), et typhoon al. and (1991) snow- reported that the ra- a delayed release inzano summer et during al., ice 1994). andtions The such snow transport as melting of vegetation, materials in slope,clarify generally mountain migration soil depends areas behavior types, on of (Spez- and radiocesium watershed springof and condi- its snow-melting. its dispersion controlling It in factors is Fukushima for important future Prefecture, to Japan. prediction ter the Fukushima Daiichi NPP accidentoutcomes (MEXT, 2012a; were Sakaguchi observed et al., at 2012). thenobyl Similar accident Pripyat in and 1986 Dnieper (IAEA, Riversover 2006a). in time The in Ukraine migration river after of waters the fromand Cher- Ukraine Ilus, (IAEA, 2001). 2006a; The IAEA, radioactivitystream 2006b) of and of Finland the (Sax exclusion zoneAn in the increase Pripyat in River of radioactivityChernobyl the of area Chernobyl during area a (IAEA, spring 2006a). flood event (IAEA, 2006a,b) and in northwest Italy from face to 5 cm depthand (MEXT, 2012a; Koarashi et al.,are 2012). only Chemical slightly extraction water of soluble.was Even only the approximately fraction 10 extracted % with (Matsunaga 1been et M transported al., ammonium 2013). from However, acetate contaminated watersheds to rivers in Fukushima Prefecture af- 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Cs and rac- ff 137 1 − Cs was Cs. The Cs activity 137 137 ects export ff . Suspended 137 Cs and ◦ 134 Cs/ Cs were 0.011– to 65 –0.089 BqL Cs and 134 1 137 ◦ − 134 Cs at normal and high flow Cs and 661 keV for 137 134 Cs was 0.009 BqL Cs using a Fukushima contaminated soil Cs versus radioactivity of dissolved forms 137 134 137 2772 2771 Cs Cs Cs in the filtered river waters was measured as 137 raction (XRD). XRD analysis of powdered samples Cs and ff 137 137 Cs in the high flow condition after the typhoon was 134 137 Cs in the river waters is shown in Table 1 and Fig. 3. . These results indicate that the heavy rain a 1 137 − Cs and in the normal flow condition. The radioactivity decreased Cs and Cs and 1 134 − 134 Cs occurred after the heavy rain event. The 134 Cs and ect was corrected for radiation operated at 40 kV and 30 mA from 2 ff 137 134 Cs and K α 134 –0.098 BqL , but in the high flow condition, that is after the heavy rain event, dissolved Cs and 1 1 − − 134 Cs. In a normal water flow condition, dissolved forms of 137 Cs was about 0.005 BqL Table 2 presents percentages of particulate phase The mineral composition of riverine suspended solids on the filters and of deposited The radioactivity of In normal flow conditions on 12 July and 14 September, dissolved and particulate conditions in the Natsui River and the Same River after the Fukushima Daiichi NPP 3.2 Existing forms of Figure 4 shows theof total radioactivity of 0.064 BqL 137 of radiocesium deposited onNPP the accident. ground Similar surface resultsChernobyl derived have accident from been (Matsunaga the reported et Fukushima al., for 1998). Daiichi Ukraine river systems after the ratio for all samplesderived from is the about Fukushima 1.0,rivers. Daiichi The corrected NPP highest to was radioactivity 11collected transported is in March 2–3 from 1985–1988 2011, orders (Hirose deposited higher et so surface al., than to that 1980; that Matsunaga radiocesium of et the al., 1991). Japanese rivers 3.1 Radioactivity of Radioactivity of The respective radioactivity0.011 of BqL concomitantly with increasing time after thethe Fukushima Daiichi radioactivity NPP accident. of However, about one order higherexport than of that at normal flow conditions, which indicates that high for clay mineral composition. 3 Results and discussion solids on GF/F and membrane filters were also mounted on glass slides and measured tometer using Cu for the activity calculation at 605cascade keV summing and e 795 keV for sample. The decay correctiondone at of each radioactive sampling concentration date.were The also for measured deposited using solids gamma-ray and spectrometryature. suspended after solids drying them on at the room filters temper- solids was analyzed using X-ray di mounted in glass slides was conducted with an Ultima IV (Rigaku Co. Ltd.) di dissolved forms of radiocesium with gamma-raydophosphate spectrometry (AMP)/Cs using compound ammonium method molyb- (Tanaka etwere al., measured using 2006). gamma-ray The spectrometry withLevel a Radioactivity low Laboratory BKG Ge and detectorUniversity the at for the Ogoya 1–3 Low Underground days Laboratory (Hamajima of and Kanazawa Komura, 2010). The gamma-lines were used 1 µm, and 0.45 µm. Inwere river separated waters after using the centrifugation heavyof rain and event 7 filtration µm) with with the filters typhoon, No. andusing particles 5A a No. (approximate pore 5A pore size filters size ofsolids and using 0.45 µm then centrifugation membrane are filtered filters. designatedfilters with Filtration as are membrane “deposits”. was designated filters. The conducted as In suspended “No.for solids 5A” this those on for collected study, those the with suspended filtered 0.45 µm with filters. No. 5A filters and “membrane” and 22 September at high-flowwas conditions conducted after Typhoon at Roke lastBridge the year. of The Iwaki-bashi the sampling Same Bridge River. of the Natsuiforms River of and radiocesium the were separated Eguri-Ohashi using cartridge filters with pore sizes of 10 µm, at normal flow conditions on 12 and 27 July, 14 September, 22 November, 6 December, 5 5 25 20 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | - 1 Cs Cs − -ss 1 − 137 137 for the values 1 d − K Cs and mLg 6 134 Cs is present as , respectively. All 10 θ 137 2 × ◦ Cs is 21–56 % on av- 137 is generated during large ff ). The fate and bioavailability Cs. Cs concentrations in the sus- 1 − 90 % of the total Cs specific activity was observed 137 137 > 137 Cs and Cs of fine particle fraction trapped on the -ss for the Same River. Therefore, radioce- Cs in river systems 1 134 − 137 2774 2773 137 and three peaks of 13–25 θ 2 ◦ for the Natsui River and 4.1–5.0 1 Cs and − Cs inventory from the surface down to depth in undis- Cs and Cs has been reported for illite and mica at laboratory 134 137 134 137 mLg raction analysis for the suspended solids filtered with Ad- respectively denote the and strength of the particle-contaminant association. Esti- ff 6 ) between suspended solids and river water is defined as d d K 10 K ) and dissolved phase (BqmL Cs derived from fallout as a tracer of suspended solids. Surface × 1 Cs and − : Ministry of the Environment, 2012) and soil in watershed (230– , (1) 137 dissolved 1 134 − C cient ( of the surface-derived suspended solids at the catchment scale. Direct ffi ff 17 %. The other rivers in central to northern Japan were 11–47 % (Hirose and dissolved : MEXT, 2012b). values was conducted using measurement data presented in Tables 1 and 1 erent stand species, surface coverage and forest management practices ± d − ff /C is 0.43–0.55 K solid d C K solid generally does not occur in forested areas, but unmanaged Japanese cypress C ff = ect the runo The cumulative Figure 5 shows X-ray di As Table 3 shows, radioactivity contents of suspended solids are about 2000 Bqkg d ff values found for the Natsui River and the Same River after the heavy rain. in the soil profileland sites was (Koarashi found et withinbeen al., studied the using 2012). upper The 5runo surface cm erosion layer processes at inplantations the watershed often cropland have have little and surfacerainstorms grass- cover, (Miyata and et surface al., runo 2007;that, Gomi et for al., di 2008). Fukuyama eta al. (2010) have shown input of suspended solids eroded from the ground surface is reflected in the higher of the Fukushima rivers areaccident two (Matsunaga orders higher et than al.,from that 1998), the of which watershed Ukraine and after is resuspension the regarded of Chernobyl as river bottom supplying sediments suspended byturbed solids rain soils events. in Fukushima Prefecture confirms that where pended matter (Bqg depend strongly on the mation of 3. The Same River. These values aresuch 1–2 as orders the higher Tone than River(Matsunaga those and et of the al., other Ishikari 1991) Japanese River before rivers (Hirose the et Fukushima al., Daiichi 1990) NPP and accident. the The Kuji River Distribution coe K 3.3 Migration behavior of have fixation and/or association ability for pended solids. Blank GF/Fas and a membrane broad peak filters between have 13samples and their include 35 own clay characteristics minerals such such in as fixation chlorite, of mica, radiocesium and/orrobova kaolin. has et Clay al., been mineral 2007). widely type Forin claimed example, floodplain an (e.g. increase Facchinelli soil in et2007). with al., Selective increased sorption 2001; smectite Ko- of experimental content systems (Brouwer in et al., clay 1983;clay fractions Staunton minerals and in (Korobova Roubaud, suspended 1997). et solids Therefore, from al., the Natsui River and the Same River appear to for the Natsui River andsium 7200–8660 Bqkg associated with suspendedareas. solids is an important pathway from landvantec to No. coastal 5A filters, membrane filters with a pore size of 0.45 µm, and deposited sus- particulate phase in the Natsui Riveris and predominant the in Same River. river The1991). waters particulate form after of the rain event in the Kujidried River suspended (Matsunaga solids et (ss). al., (about This 2000 value Bqkg corresponds to2400 Bqkg that of river-bottomfilters sediment in the river waters also show higher radioactivity content of 1550–2640 Bqkg cident. At normal flow conditions, theerage percentage of of 41 particulate et al., 1990; Matsunaga etradiocesium al., in 1991). the The Pripyat particulate(Voitsekhovich River et phase had al., during approximately 1997). 40–60 the % Heavy decade of rains show after that the a Chernobyl major accident part of accident, together with results for the Kuji River before the Fukushima Daiichi NPP ac- 5 5 20 25 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . 1 1 1 − − Cs − s Cs. 3 134 137 for the Cs and 1 ) of − 134 264 m F ± 0.004 BqL for 0.0315 BqL ± 1 ± − denotes the period of Bq/305 days for Bqday T 10 10 and 0.853 1 10 10 − × × Cs and 0.0566 4.8 Cs in river waters. 1.5 134 ± ± Cs except for the heavy rain sam- 137 for Cs in the Natsui River and the Same 137 Cs associated with riverine suspended 1 0.004 BqL − ± 137 137 Cs deposited in river bottom sediments was Cs and 2776 2775 Cs and 2.6 137 134 Cs from land to ocean after the Fukushima Dai- 134 Cs and Cs and 0.0276 BqL 137 134 134 Cs for the Natsui River and the Same River together ± Cs on 22 September 2011. This value, which corre- Cs and during March–December 2011. The fluxes ( 137 1 137 134 − Cs derived from global fallout have also been observed at s Cs and 3 for 137 1 134 − Cs during 1 January–10 March might be similar to that before the -sediment for the Natsui River and approx. 2000 Bqkg 137 1 30.8 m − ± 4.2 Bq/305 days for Cs were, respectively, 0.673 Bqday , (2) ± T 10 137 × 10 stands for the mean radioactivity of × WD Cs are defined as C × Cs, except for the sample taken after the heavy rain. Mean monthly water dis- 1.9 Cs and 137 C ± 137 134 Table 4 shows flux data of Regarding the heavy rain event, a mean daily water discharge was 350 Figure 6 presents a schematic illustration showing the export of radiocesium from the The radioactive content of = To realize transport of ichi NPP accident, river research was performed at the Natsui River and the Same 2011 is one orderin higher 1988–1989. than The that heavy of rain50 the event % by Tone of Typhoon River Roke the in on annual 1985–1986factor 22 export September and determining flux. occupied the These the 30– Kuji results export River River. indicate of that the heavy rain event is one 4 Summary itored at the Onahama siteof (JMA, rain 2012). events on However, we transport can of understand radiocesium the from importance inland towith the other ocean in river a systems.simple year. method The in flux this at study. the As Table Same 4 River shows, the was export estimated flux using in a Fukushima similar rivers in Fukushima Daiichi NPP accident andvalue 2–3 corresponds order to lower values. the Therefore, annual the export estimated flux. calculated from hourly water dischargeof on 22 September 2011. TheTherefore radioactivity the levels fluxes from2.6 river to ocean weresponds 2.0 to that ina March–December lack of 2011, consideration for represents the six a rain rough events with estimation precipitation greater because than 50 of mm mon- where ple, WD signifies11 the March–31 mean December in monthly 2011.timated The water as fluxes of 2.3 discharge, radiocesium and fromThe land radioactivity to of ocean are es- F To understand the impacts ofpersion heavy to rains coastal on the ocean,estimated transport simply flux of based of radiocesium on and radiocesiumdischarge data our its from (Fukushima dis- measurements, Prefectural land Government, as 2011). througheraged shown In radioactivity river the in was Natsui to Table 0.0493 River, the 1 oceanfor av- and was from water charge was 17.6 and sion and radioactivity of the Kuzuryuu River in 2009 after rain events (Nagao,3.4 unpublished data). Estimation of radiocesium flux from land to ocean particles might be shorttaminated in area the around Natsui therole river River as basin and sources and the of river Same particulate bottom phase River. sediments of Therefore, plays the an con- watershed important to a river. Erosionof of river riverbank bottom and sediments the occurs ground atincreases surfaces, rain and and events the so re-suspension radioactivity that of thesolids amount also of suspended increases. solids Similarthrough Ibaraki results and have Fukushima been prefectures reported (Matsunaga for et the al., Kuji 1998). River, Increased running ero- approx. 770 Bqkg Same River during 2011–2012varied (Ministry with of sampling, although the the Environment,river. samplings 2012). The were The conducted river at radioactivity bottom fixed stations sediments in are each sandy, so the apparent residence time of fine 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | of in Cs 1 ff − erent 137 ff = no , 2011 (in Bqday 10 Cs and e.html 10 134 36&block × = Cs was 21–56 % in no 137 , but at a high flow con- 1 − houkokusho pathways in steep nested catch- Cs and ff 134 10d.php?prec sfc Cs after the heavy rain event is estimated Cs accidentally discharged from the Fukushima 137 2778 2777 137 , 2012. I and = in the Natsui River and 0.74–0.87 Cs and 1 http://www.data.jma.go.jp/obd/stats/data/bosai/report/new/ 131 − 134 . Particulate phase of , 2011. &view 1 − = Bqday &day 10 = 10 The authors wish to thank S. Nishimura of Kanazawa University for as- × &month = http://www.kantei.go.jp/foreign/kan/topics/201106/iaea sokuji20110915-0922.pdf Nuclear Safety – The Accidentable at at: TEPCO’s Fukushima NuclearJapanese). Power Stations, 2011, avail- fecting vertical distribution of Fukushimaland-use accident-derived conditions, radiocesium Sci. in Total soil Environ., under 431, di 392–401, 2012. http://www.data.jma.go.jp/obd/stats/etrn/view/nml 47598&year Basin: Assessment by anPlan, Vienna, International Austria, Expert 2006b. Team and Recommendations forphoon as Action 15, 2011,jyun available at: Japan, J. Radioanal. Nucl. Ch., 141, 191–202, 1990. Accident and Their Remediation: Twenty Years of Experience, Vienna, Austria, 2006a. Fukuyama, T., and Fukushima, T.: Evaluation ofments storm draining runo a Japanese cypress forestProcess., in 24, central 550–566, Japan: 2008. a geochemical approach, Hydrol. Int. 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M., Misono, J., and Komura, K.: Vertical profiles of Spezzano, P., Bortoluzzi, S., Giacomelli, R., and Massironi, L.: Seasonal variations of Sakaguchi, A., Kadokura, A., Steier, P., Tanaka, K., Takahashi, Y., Chiga, H., Matsushima, A., Morino, Y., Ohara, T., and Nishizawa, M.: Atmospheric behavior, deposition, and budget of ra- Sax Ministry of the EnvironmentMiyata, in S., Kosugi, Japan, K., Gomi, available T., Onda, at: Y., and Mizuyama, T.: Occurrence of surface runo Ministry of Education, Culture Sports, Science and Technology in Japan (MEXT):Ministry Monitoring of Land, Infrastructure, Transport and Tourism in Japan (MLIT): Report on water re- Nagano, T., Yanase, N., Tsutsuki, K., and Nagao, S.: Particulate and dissolved loads in the Kuji Ministry of Education, Culture Sports, Science and Technology inMinistry Japan of (MEXT), Education, available at: Culture Sports, Science and Technology in Japan (MEXT): Report of Matsunaga, T., Koarashi, J., Atarashi-Andoh, M.-A., Nagao, S., Sato, T., and Nagai, H.: Com- Matsunaga, T., Ueno, T., Amano, H., Tkachenko, Y., Kovalyov, A., Watanabe, M., and On- Matsunaga, T., Amano, H., and Yanase, N.: Discharge of dissolved and particulate Korobova, E. M. and Chizhikova, N. P.:Distribution and mobility of radiocesium in relation to the 5 5 25 20 15 10 30 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ∗ Cs 0.06 0.03 0.07 0.01 0.03 0.06 0.04 0.16 0.10 0.01 0.05 0.13 137 ± ± ± ± ± ± ± ± ± ± ± ± Cs/ 134 in a normal flow condition. ) 1 1 − Cs − s 2.52.5 1.06 1.2 1.02 4.0 1.14 1.2 1.00 1.6 0.97 1.04 2.25.7 1.03 1.2 0.99 3.0 1.00 0.6 1.01 1.5 1.00 1.10 3 in a normal flow condition. ± ± ± ± ± ± ± ± ± ± ± ± 137 1 − BqL s 3 3 − Cs was done on 11 March 2011. 10 137 Cs in water samples from the Natsui × 137 9 6 Hirose et al. (1990) 5 2 This study 31 2 Hirose et al. (1990) 17 217 This study 12 Matsunaga et al. (1991) 77 1 Matsunaga et al. (1991) )( ± ± C 100 1 This study Cs and 1 ± ± ± − 1.31.61.2 52.0 4.0 98.0 1.8 26.0 1.4 853.0 78.7 27.7 2.45.91.3 81.0 3.0 52.0 0.7 18.9 1.0 424.0 15.3 11.4 ∼ 134 134 Cs (%) sample ± ± ± ± ± ± ± ± ± ± ± ± Cs and BqL 137 2782 2781 3 134 − . 1 ) − 10 c C Particulate No. Reference 1 × − 1.3 1.61.2 40 99 1 This study 4.0 26 Cs associated with suspended solids in the Natsui and 137 0.590.12 21 47 0.06 41 ± ± ± ± 137 ± ± ± BqL in a high flow condition and 11.0–23.7 m C) ( 3 1 ◦ − − s in a high flow condition and 8.1–59.4 m 3 10 1 − × Cs and s 3 134 Condition ( High 49.0 Normal 89.5 High 25.2 NormalNormal 673.0 0.12 High 1.0 a Sampling pHNatsui River WT 12 Jul 201127 Jul 2011 7.613 Sep 2011 7.4 29.522 Sep 2011 7.3 26.024 Nov 2011 7.8 25.56 Dec 2011 18.6 7.6 49.0 10.9 89.0 7.4Same 25.2 River 673.0 6.512 61.5 Jul 201127 Jul 2011 7.513 22.0 Sep 2011 7.5 25.422 Sep 7.8 2011 23.424 Nov 2011 22.9 7.96 Dec 2011 18.6 7.4 74.5 11.8 47.5 7.5 15.9 360.0 8.5 13.2 8.9 date ( Percentage of Water quality and radioactivity of Decay correction of radioactive concentration for a ∗ b Water discharge was 238–350 m Water discharge was 75.4 m River Flow Natsui Kuziryu 1.17 11 1 Hirose et al. (1990) Ishikari 0.37 Same KitakamiTone 0.77 0.14 39 1 Hirose et al. (1990) Kuji Proceeding precipitation was above 30 mmday a b c Table 2. Same River waters at low and high flow conditions. Table 1. River and the Same River. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ∗ Cs 0.01 0.02 0.01 0.04 0.04 0.01 137 ± ± ± ± ± ± Cs/ 134 93 1.03 14 1.01 1164 1.00 76 1.03 0.97 Cs -ss) 127 1.03 ± ± ± ± ± 1 137 ± − Cs was done on 11 March 137 ) (%) 1 Cs (Hirose et al., 1990) and mean − 1.9 50 2011 0.92 30 2011 Cs and 137 ± C ± 81 8649 14 1865 1158 2336 70 1817 2303 134 -ss) (Bqkg 113 8268 134 ± ± ± ± ± 1 Bqday C Contribution Year ± − 10 137 2784 2783 10 × Cs of suspended solids in water samples from the Natsui )( 1 137 − 1.31.2 2.6 0.87 0.26 – – 1988 0.38 – – 1985 ± ± Cs annual load (Matsunaga et al., 1991) and watershed area ± Annual Heavy rain of heavy rain 137 Bqyr Cs from land to ocean in the Natsui, Same, Kuji and Tone Rivers. 10 Cs and solid (g) (Bqkg 0.50 10 137 134 × ( b a Flux estimates from Flux estimates from the average radioactivity of RiverNatsui Export fluxSame of Kuji Tone 5.2 2.9 suspended solids in river water. Membrane 0.182 7691 Deposit 3.42 1569 No.5AMembrane 0.362 0.096No.5A 1934 1548 0.062 7176 Deposit 6.88 1980 a of the Kuji River. b annual water discharge in 1985 (MLIT, 2012). = Same River SampleNatsui River Suspended Decay correction of radioactive concentration for ss ∗ 2011. Export fluxes of Radioactivity of Table 4. Table 3. River and the Same River collected on 22 September 2011 after Typhoon Roke. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

23 Natsui River 10 km Same River Fukushima Dai-ichi NPP Fukushima Dai-ichi

2786 2785 ° ° 40 N ° 33 N 143 E Fukushima Dai-ichi NPP ° 135 E Sampling location of the Natsui River and the Same River. Closed circles represent Water discharge of the Natsui River and the Same River in 2011. Data were referred

Figure 2 Water discharge of the Natsui River and referred from the Fukushima Prefectural Government. the Same River in 2011. Data were

8 9 2 3 4 5 6 7 1 13 14 15 16 17 18 10 11 12

from the Fukushima Prefectural Government. Fig. 2. Fig. 1. sampling stations. Open circles showinverted a triangles monitoring represent water station level at observatory Onahama sites. for precipitation. Open Fig.1

) and the Same River ( ◦ Cs in river waters from the Natsui River (○) 137

Cs in river waters from the Natsui River ( 2788 2787 137 Cs in water samples from the Natsui River (○) and the Same 137 December 2011.

– Cs in water samples from the Natsui River ( 137 ng July ). • Total and dissolved radioactivity of Radioactivity of

Figure and 4 dissolved Total radioactivity of and the Same River (●).

Figure 3 Radioactivity of River (●) duri

Same 27 ) and

and Same River (a)

Cs from watersheds to rivers. Cs from watersheds to rivers. 137 137 Cs and 134 Cs and 2790 2789 134 ns of suspended solids in the Natsui River (a patter raction patterns of suspended solids in the Natsui River ﬀ ray diffraction -

Figure 6 Schematic illustrations of export of

X-ray di Schematic illustrations of export of

after the heavy rain event by Typhoon Roke in 2011. 2 3 4 5 6 7 8 9 1 10 11 12 13 14 15 16 17 re 5 X Fig. 6. (b) Fig. 5. gu

Fi Roke in 2011. Typhoon River (b) after the heavy rain event by

3 4 5 6 7 8 9 2 1 23 24 25 26 19 20 21 22 13 14 15 16 17 18 10 11 12