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- Title
Hydrological response and 137Cs wash-off evaluated by continuous observation with USLE plots in Chernobyl exclusion zone.
- Authors
Wakiyama, Yoshifumi; Igarashi, Yasunori; Onda, Yuichi; Takahashi, Junko; Samoilov, Dmitry; Obrizan, Sergii; Lisovyi, Hlib; Laptev, Gennady; Konoplev, Alexei; Tsukada, Hirofumi; Nanba, Kenji
- Abstract
Radionuclide wash-off is a key issue for understanding its redistribution in theenvironments after nuclear disasters. Plot-scale radionuclide wash-off was evaluatedby coupling runoff plots with artificial rainfall experiment and snowmelt runoffmonitoring after the accident of Chernobyl nuclear power plant. However, there isno continuous observation of plot-scale radionuclide wash-off in Chernobyl andtherefore long-term dynamics of radionuclide and hydrological response to naturalrainfall remained unclear. This study shows approximately one-year observationof radionuclides wash-off from three runoff plots during 2018 in the Chernobylexclusion zone. Runoff plots were established on a pine forest in the Kopachi area(PF-KP), an abandoned farmland in the Korogod area (AF-KR) and a post wild fireterritory in the Red Forest (WF-RF) in December 2017. Each runoff plot following astandard for Universal Soil Loss Equation studies consists of eroding surface of22.13 m length and 5 m width, a 30˚ V-notch weir with water level sensor formonitoring surface runoff and tanks for collecting runoff water and sediments.Sensors were installed at depths of 5, 10, 20, 30 and 50 cm in soil around the plots tomonitor soil water content and soil temperature. An interval camera was installed ateach plot for evaluating soil surface condition during runoff events. Since February2018, runoff water and sediment samples trapped in the weir and tanks have beencollected after rainfall events and analyzed for their particulate and dissolved 137Csactivity concentrations. The 137Cs inventories around the plots were quantifiedby soil sampling. During winter-spring season, one runoff event for the PF-KPand three runoff events for the AF-KR were observed. Soil temperature of 5cmdepth was below 0˚ C during precipitation at the PF-KP and it was suggested bothrain and snowmelt water ran off on frozen soil. In contrast, soil temperature wereabove 0˚ C at time of precipitation through winter-spring season in the AF-KRand it is suggested that snowmelt water mainly ran off from the AF-KR. Duringwinter-spring season, particulate and dissolved 137Cs activity concentration forPF-KP was 150000 Bq kg−1 and 4.3 Bq L−1(n = 1), respectively. Those for theAF-KR was, in average (n = 4), 3300 Bq kg−1 and 0.29 Bq L−1, respectively. Duringsummer season, one runoff event on the PF-KP and one runoff event on the WF-RFwere observed during a rainfall event on 30th June with total rainfall of 57.8 mm.Runoff coefficient for the PF-KP and the WF-RF in this event was 1.1% and 1.9%,respectively. Because no runoff was observed in the AF-KR which showed morefrequent runoff during winter-spring season, surface runoff from the PF-KP and theWF-RF could be attributed to severe water-repellency. Furthermore, the image fromthe interval cameras for the WF-RF showed that entire surface soil within the plotwas saturated during the rainfall event and it is suggested that ash resulted fromwild-fire created strongly-hydrophobic layer and prevented water infiltration. Theseresults suggest that wild fire could increase surface runoff and radionuclide wash-off.
- Subjects
RUNOFF; SOIL infiltration; UNIVERSAL soil loss equation; SOIL moisture; SEEPAGE; FROZEN ground; SOIL temperature
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article