Haishan Chen, Fangda Teng, Wanxin Zhang, Hong Liao. Impacts of Anomalous Midlatitude Cyclone Activity over East Asia during Summer on the Decadal Mode of East Asian Summer Monsoon and Its Possible Mechanism. Journal of Climate, 739-753. 15 January 2017.
By using an objective identification and tracking algorithm of the cyclone, the statistics of midlatitude cyclone activity in East Asia during summer for the period 1979–2013 were analyzed. The impact of the midlatitude summer cyclone anomalies in East Asia on the decadal mode of East Asian summer monsoon (EASM) was investigated and possible mechanisms were proposed. The possible reasons for the anomalous cyclone activity from the perspective of land surface thermal forcing were also explored. Results indicate that the midlatitude summer cyclone activity over East Asia exhibits decadal changes in the period of 1979–2013 and is significantly weakened after early 1990s. Further analysis indicates that there is a close relationship between the midlatitude summer cyclone activity over East Asia and the decadal variation of EASM; when the midlatitude summer cyclone activity over East Asia is strong (weak), EASM tends to be intensified (weakened), and the weak cyclone activity after 1993 generally coincides with the decadal weakening of EASM. Moreover, there is a close linkage between the weakening of cyclonic activity after the early 1990s and the nonuniform surface warming of the Eurasian continent. Significant warming to the west of Mongolia tends to weaken the north–south temperature gradient and the atmospheric baroclinicity to its south and eventually can lead to weakening of the midlatitude cyclone activity over East Asia.
Hill L, Suursoo S, Kiisk M, Jantsikene A, Nilb N, Munter R, Realo E, Koch R, Putk K, Leier M, Vaasma T, Isakar K. Long-term monitoring of water treatment technology designed for radium removal-removal efficiencies and NORM formation. J Radiol Prot. 2017 Dec 6;38(1):1-24. doi: 10.1088/1361-6498/aa97f2.
A drinking water treatment plant in Viimsi, Estonia, was monitored over three years for iron, manganese, radium-226, radium-228, as well as their daughter nuclides, in order to determine the efficiency of the treatment process, gain an insight into the removal mechanisms and interactions between radium, iron, and manganese, and assess the overall longevity and performance of the technology along with the possible build-up of NORM in the treatment process. During the study, samples were collected from raw water, first and second stage filtrate, consumer water, backwash water and filter materials. The results show consistent removal efficiency for iron and manganese, as well as an average of over 85% removal for radium with a slight decline over time. The backwash process has been optimised for maximum radium removal from the filters, while keeping concentrations in the backwash water below exemption levels. However, the accumulation of radium and thorium occurs in the filter material, exceeding exemption levels in the top layer of the filter columns in less than a year. By the end of the observation period, activity concentrations in the top layer of the columns were above 30 000 Bq kg-1 for Ra-226 and Ra-228, and around 15 000 Bq kg-1 for Th-228. Radionuclides are not homogenously distributed in the filter columns. In order to estimate the average activity concentrations in the filter media, the height distribution of radionuclides has to be accounted for. Two years and two months after commissioning the treatment plant, the average activity concentrations of Ra isotopes in the filter columns were in the range 10 000 Bq kg-1, while Th-228 activity concentration was roughly 3500 Bq kg-1.