Intra-Annual Deposition of Atmospheric 210Pb,210Po and the Residence Times of Aerosol in Xiamen, China (original) (raw)
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Geochemical Journal, 1995
Atmospheric bulk deposition and aerosol samples were collected simultaneously in the surface air over the west coast of Japan (38°46' N, 139°44' E), and analyzed for 210Pb. By coupling data with those pre viously reported for 210Po (Suzuki, 1994), the following results have been obtained. (1) The 210po/210Pb activity ratios in aerosols were consistently larger than those in atmospheric depositions, and (2) the activity ratios in April were larger than those in July and October in both aerosol and deposition samples. The results can be variously attributed to the difference of residence time between atmospheric suspending and settling particles, and the difference of contribution from various sources in which 210Pb and 210Po are in over-, under or secular-equilibrium.
Journal of Geophysical Research, 2007
Daughter products of 222 Rn (such as 210 Pb, half-life = 22.1 years, and 210 Po, half-life = 138 days) have been widely used as tracers to determine the removal rates of aerosols as well to obtain analog information on the behavior of other chemical species in the lower atmosphere. To establish the first data set on the depositional fluxes of 210 Po in bulk precipitation and concentrations in air samples from the midwestern United States, we measured the depositional fluxes of 210 Pb and 210 Po in the bulk (wet plus dry) and dry fallout by deploying a rain collector (dry and bulk) for a period of 17 months. We also collected 30 aerosol samples during this period to assess the temporal variations of these nuclides in the surface air in Detroit, Michigan. The activity of 210 Po in the surface air ranged from below detection limit to 0.118 mBq m À3 (mean of 0.072 mBq m À3). The specific activities of 210 Po and 210 Pb in aerosols ranged between 0.28 and 4.48 Bq g À1 (mean of 0.87 Bq g À1) and 2.7 and 30 Bq g À1 (mean of 13.6 Bq g À1), respectively; these values are about 1-2 orders of magnitude higher than the surface soil. The mean activity ratios of 210 Po/ 210 Pb in the bulk precipitation and dry fallout were found to be 0.049 (n = 27) and 0.25 (n = 8), corresponding to residence times of 15 and 75 days, respectively. Higher values in the dry fallout are attributed to resuspension of very fine older material from the ground. The 210 Po/ 210 Pb activity ratios in the aerosols varied between 0 and 0.210 (mean of 0.075), with corresponding residence times of 0-61 days (mean of 22 days). The mean deposition velocity and bulk washout ratio obtained using 210 Po is compared with those obtained for 210 Pb. From the measured aerosol mass concentrations and calculated values of the depositional velocity, the calculated depositional fluxes of aerosols are reported.
Tellus B, 2012
Atmospheric 210 Pb, 210 Po and their activity ratio (210 Po/ 210 Pb) have been studied for two years (January 2007Á April 2009) from an urban site (Kanpur: 26.58N and 80.38E) in the Indo-Gangetic Plain. The average activities of 210 Pb and 210 Po centre on 1.8 mBq m (3 (range: 0.5Á4.8 mBq m (3 for n099) and 0.094 mBq m (3 (n021, range: 0.002Á0.28 mBq m (3), respectively. The temporal variability in the activity of 210 Pb is significantly pronounced, with relatively high levels during OctoberÁNovember and DecemberÁFebruary; a trend similar to that observed for the carbonaceous species. The high aerosol abundance coinciding with the biomass burning emissions (agricultural-waste burning) during OctoberÁNovember and stagnant boundary layer in the wintertime (DecemberÁFebruary) is the dominant factor for the observed temporal trend. The preliminary data suggest that biomass burning emissions also contribute to the atmospheric 210 Po activity, as evident from the large variability in the 210 Po/ 210 Pb activity ratio (range: 0.02Á0.23) at this urban site. These results have implications to the model-based activity levels of 210 Pb and 210 Po from in-situ decay of the parent nuclide (222 Rn) for given latitude.
Journal of Geophysical Research, 2006
1] Fluxes of 7 Be and 210 Pb monitored at two contrasting sites in northern Taiwan were studied along with meteorological data to elucidate factors controlling their temporal and spatial variations. The 9 year time series of both nuclides at Nankang in the Taipei Basin show dependence on wet precipitation and follow an annual cycle regulated by typhoons, monsoons, and mei-yü. Superimposed on the annual cycle are interannual variation caused by El Niño-Southern Oscillation and intraseasonal oscillations due to the passage or invasion of fronts, cold surges, dust storms, and the Pacific high-pressure system. The observed 7 Be/ 210 Pb ratios are indicative of the source regions of the fallout nuclides, with higher ratios from high-altitude rain and lower ratios from dry fallout and low-altitude rain. The 2 year time series at Yangminshan shows that 7 Be and 210 Pb fluxes at the mountainous site are in phase with those at Nankang. However, nuclide fluxes at Yangminshan are 4-5 times those at Nankang. After combining results from this and other ancillary studies at Yangminshan, we suggest that (1) in applying fallout nuclides to study the Earth's surface processes, the assumption of constant flux should be made judicially according to the timescales involved, and that (2) the application of fallout nuclides to study soil erosion in hilly areas must consider not only control by wet and dry precipitation but also by direct contact and interaction of clouds with soils enhancing nuclide fluxes.
Deposition fluxes of 210 Pb on low and moderately high-elevation sites of Edinburgh (Scotland) and mid-Wales, respectively, have been measured. The excess 210 Pb fluxes in moorland Edinburgh soils did not vary significantly and ranged from 71 to 92 Bq m −2 y −1 with a mean value of 78 ± 9 Bq m −2 y −1 , for all the measured sites where both altitude and the mean annual rainfall are similar. On the other hand, the excess 210 Pb measured in moorland soils of mid-Wales sites increased by a factor of 2.4 at or near the summit (741 m asl) relative to the coast (∼15 m asl), whereas rainfall increased by a factor of 1.8 over the same height range. On average, the summit to valley ratio of 210 Pb concentration in rainfall was a factor of 1.3 due to scavenging of the feeder clouds by the seeder rain. These results are consistent with results for both modelled and field studies on the wet deposition of pollutants in complex terrain reported by several researchers. The long-term 210 Pb wet deposition field data will provide an important input parameter for the modelling of wet deposition of aerosols throughout the uplands of the UK and elsewhere where the seeder-feeder process is of common occurrence.
Impact of Precipitation with Different Intensity on PM2.5 over Typical Regions of China
Atmosphere
Atmospheric aerosol pollution has significant impacts on human health and economic society. One of the most efficient way to remove the pollutants from the atmosphere is wet deposition. This study selected three typical atmospheric pollution regions in China, the Beijing-Tianjin-Hebei (BTH), the Yangtze River Delta (YRD) and the Pearl River Delta (PRD) regions, as research areas, and used the hourly precipitation and PM2.5 mass concentration data from 2015 to 2017 to investigate the removal impacts of precipitation on PM2.5. The PM2.5 mass concentration difference before and after the hourly precipitation events was used to denote as the impacts of precipitation. Hourly precipitation event was selected so that the time difference between two PM2.5 observations was short enough to limit the PM2.5 change caused by other factors. This study focused on the differences in the removal effect of precipitation on PM2.5 under different precipitation intensities and pollution levels. The resu...
Pb-210 DEPOSITION MEASURED IN RAINFALL IN SÃO PAULO, SP – BRAZIL
Pb-210 (T 1/2 = 22.3 y), a natural radionuclide from U-238 serie can be found in the atmosphere, as a product of 222 Rn decay that emanates from the ground, where its atoms become rapidly fixed to aerosols and return to the earth as dry fallout or are washed out in the rain. This natural radionuclide has been widely used as an atmospheric tracer, to determine the aerosol residence time as well as chronometers in the environment. Pb-210 was measured during a period of two years, 2011 to 2013, in samples of rainfall in all the rainy events that ocurred at the Instituto de Pesquisas Energéticas e Nucleares (IPEN) campus (23 o 33'59.24 " S-46 o 44'15.63 " O at 760 m above sea level) which is located in the city of São Paulo, in the state of São Paulo, Brazil. Pb-210 concentration was measured in a total of 123 rainy events by beta gross counting in a low background gas flow proportional detector, after radiochemistry procedure. The results obtained were correlated to s...
Aerosol Science and Technology, 2000
Lead-210 and 210 Po were measured in size-fractionated aerosol samples collected at several sites in North America. Total particulate mass concentrations of the samples were 23-98 m g r r r r r m 3 , with 23-67% of the mass in size ranges below 2 m m. The aerosol mass size distributions below 9 m m were generally bimodal, with a maximum in the coarse-particle range occurring primarily at 3.1 m m and a maximum in the accumulation range occurring at approximately 0.6 m m. Total 210 Pb concentrations were 0.
Atmospheric Deposition of 7Be in the Southeast of China: A Case Study in Xiamen
Aerosol and Air Quality Research, 2017
Atmospheric deposition of 7 Be was measured at a time-series station in the southeast of China (Xiamen) from 2011 to 2013. The deposition fluxes of 7 Be ranged from 0.05 Bq m-2 d-1 to 7.42 Bq m-2 d-1 , averaging 1.87 ± 0.10 Bq m-2 d-1. High fluxes occurred in months with northeast monsoon, and low values were observed in the southwest monsoon prevailing months. The significant correlations between 7 Be deposition and precipitation, existing in both northeast and southwest monsoon seasons, suggested the dominant removal of atmospheric 7 Be via precipitation. However, the correlations showed a large slope for the northeast monsoon season, indicating higher 7 Be contents in the atmosphere during the northeast monsoon prevailing months, supported by the precipitation-normalized 7 Be and the temporal variability of 7 Be/ 210 Pb ratios. Such a scenario revealed more intensive exchange of air mass between the stratosphere and troposphere during the northeast monsoon prevailing months. Together with the high pollutant concentrations in ambient air observed in these seasons, the results indicated that the pollutants in Xiamen might enter into the upper troposphere via vertical air mass exchange.