DOI: 10.1016/j.atmosenv.2017.12.010
Scopus记录号: 2-s2.0-85038950833
论文题名: Characterising fifteen years of continuous atmospheric radon activity observations at Cape Point (South Africa)
作者: Botha R ; , Labuschagne C ; , Williams A ; G ; , Bosman G ; , Brunke E ; -G ; , Rossouw A ; , Lindsay R
刊名: Atmospheric Environment
ISSN: 0168-2563
EISSN: 1573-515X
出版年: 2018
卷: 176 起始页码: 30
结束页码: 39
语种: 英语
英文关键词: Inter-annual trend
; Periodicity
; Radon
; Seasonal cycle
; South Africa
Scopus关键词: Atmospheric chemistry
; Climate change
; Fast Fourier transforms
; Fourier series
; Time series analysis
; Circulation patterns
; Interannual
; Meteorological condition
; Periodicity
; Radon activity concentration
; Radon concentrations
; Seasonal cycle
; South Africa
; Radon
; radon
; air mass
; annual variation
; atmospheric chemistry
; coastal zone
; monitoring
; periodicity
; radioactivity
; radon
; seasonal variation
; skewness
; Southern Hemisphere
; trend analysis
; wind direction
; airflow
; altitude
; Article
; atmosphere
; circadian rhythm
; Fourier transformation
; meteorology
; oceanic regions
; periodicity
; power spectrum
; priority journal
; South Africa
; Southern Hemisphere
; spring
; summer
; surface property
; time series analysis
; winter
; Cape Point
; South Africa
; Western Cape
Scopus学科分类: Environmental Science: Water Science and Technology
; Earth and Planetary Sciences: Earth-Surface Processes
; Environmental Science: Environmental Chemistry
英文摘要: This paper describes and discusses fifteen years (1999–2013) of continuous hourly atmospheric radon (222Rn) monitoring at the coastal low-altitude Southern Hemisphere Cape Point Station in South Africa. A strong seasonal cycle is evident in the observed radon concentrations, with maxima during the winter months, when air masses arriving at the Cape Point station from over the African continental surface are more frequently observed, and minima during the summer months, when an oceanic fetch is predominant. An atmospheric mean radon activity concentration of 676 ± 2 mBq/m3 is found over the 15-year record, having a strongly skewed distribution that exhibits a large number of events falling into a compact range of low values (corresponding to oceanic air masses), and a smaller number of events with high radon values spread over a wide range (corresponding to continental air masses). The mean radon concentration from continental air masses (1 004 ± 6 mBq/m3) is about two times higher compared to oceanic air masses (479 ± 3 mBq/m3). The number of atmospheric radon events observed is strongly dependent on the wind direction. A power spectral Fast Fourier Transform analysis of the 15-year radon time series reveals prominent peaks at semi-diurnal, diurnal and annual timescales. Two inter-annual radon periodicities have been established, the diurnal 0.98 ± 0.04 day−1 and half-diurnal 2.07 ± 0.15 day−1. The annual peak reflects major seasonal changes in the patterns of offshore versus onshore flow associated with regional/hemispheric circulation patterns, whereas the diurnal and semi-diurnal peaks together reflect the influence of local nocturnal radon build-up over land, and the interplay between mesoscale sea/land breezes. The winter-time diurnal radon concentration had a significant decrease of about 200 mBq/m3 (17%) while the summer-time diurnal radon concentration revealed nearly no changes. A slow decline in the higher radon percentiles (75th and 95th) for the winter and spring seasons is found over the 15-year data set, with most of the change occurring in the first 9 years (1999–2007). This observed inter-annual decline appears to be associated with changes in the frequency of air masses having originated from over the African continental surfaces, and no significant trend is found in the lower radon percentiles associated with oceanic air masses. The general decrease of atmospheric radon-associated with continental air-masses at Cape Point could be attributed to changing meteorological conditions, possibly driven by climate change. © 2017 Elsevier Ltd Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/83039
Appears in Collections: 气候变化事实与影响
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作者单位: Department of Physics, University of Western Cape, Private Bag X17, Bellville, South Africa; South African Weather Service, c/o CSIR, PO Box 320, Stellenbosch, South Africa; Flerov Laboratory of Nuclear Reactions, JINR, Joliot-Curie str. 6, Dubna, Russian Federation; Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW, Australia; Department of Physics, Stellenbosch University, Private Bag X1, Matieland, South Africa; Department of E & E Engineering, Stellenbosch University, Private Bag X1, Matieland, South Africa
Recommended Citation:
Botha R,, Labuschagne C,, Williams A,et al. Characterising fifteen years of continuous atmospheric radon activity observations at Cape Point (South Africa)[J]. Atmospheric Environment,2018-01-01,176