Atmospheric Concentrations Of 210Pb Research Articles

A study of temporal variations of 7Be and 210Pb concentrations and their correlations with rainfall and other parameters in the South West Coast of India

As a part of establishing a regional database on natural radioactivity, the atmospheric concentrations of 210Pb and 7Be were measured over a three and half year period (2014–2017) in Mangalore and Kaiga in the South West Coast of India. A total of 99 air samples, collected in the different months of the year, were analysed in this study. The mean activity concentrations of 7Be and 210Pb were found to be 5.5 ± 3.1 mBq m−3 and 1.1 ± 0.73 mBq m−3, respectively. Both the radionuclides exhibited strong seasonal variations, with maximum concentration of 7Be occurring in the summer and that of 210Pb in the winter season. The concentration of both the radionuclides was minimum in the rainy season. Higher 210Pb concentration during winter was attributed to the ingression of continental air masses due to the wind regime from the North East. The sunspot number index of the solar activity also plays an important role in the increase and decrease of 7Be concentration in the air. A clear trend of increased and lowered concentration of 7Be with lower and higher solar activity (low and high sunspot number), respectively, in accordance with the 11-year solar cycle, was observed in this study. The temporal variation of PM10 concentration was also studied and it showed maximum value in the winter and minimum in the rainy season with an average of 56.9 μg m−3. Statistically significant positive correlation was observed between the PM10 and 210Pb activity concentration, whereas a weak correlation was observed between PM10 and 7Be. This is due to the fact that 7Be is largely associated with sub-micrometer size particles, whereas PM10 is contributed by larger sizes. The dependence of the activity concentrations of 7Be and 210Pb with meteorological parameters such as rainfall, temperature, and humidity was studied through linear regression analysis. A significant correlation was observed between 7Be and 210Pb concentrations with rainfall intensity (with identical correlation coefficients), which suggested that the removal mechanisms of these two radionuclides were similar. 7Be showed a strong correlation with temperature, whereas 210Pb with humidity. A comparison of the data obtained in the present study for the South West Coast of India with the global literature values of 7Be and 210Pb in aerosols showed that the values did not reflect the well-known latitudinal dependence of the 7Be tropospheric fluxes. Overall, the study provides an improved understanding of the correlation and variability of 210Pb and 7Be concentrations in the atmosphere in the South West Coast of India.

Atmospheric Concentrations of 210Pb and 7Be Observed in Okinawa Islands

Atmospheric Concentrations of 210Pb and 7Be Observed in Okinawa Islands

Air mass origins by back trajectory analysis for evaluating atmospheric 210Pb concentrations at Rokkasho, Aomori, Japan

Atmospheric concentrations of 210Pb change with various factors such as meso-scale meteorological conditions. We have already reported the biweekly atmospheric 210Pb concentrations in Rokkasho, Japan for 5 years and found that they had clear seasonal variations: low concentrations in summer and high values in winter to spring. To study the reasons for the seasonal variations, the origins of the air mass flowing to Rokkasho were analyzed by 3-D backward air mass trajectory analysis. Routes of the calculated trajectories were classified into four regions: northeastern and southeastern Asian Continent, sea and other regions. The atmospheric 210Pb concentrations were well correlated with the frequency of the routes through the northeastern Asian Continent. A non-linear multiple regression analysis of the 210Pb concentrations and the relative frequencies of the four routes showed good fitting of the predicted values to the observed ones, and indicated that the atmospheric 210Pb concentrations in Rokkasho depended on the frequency of the air mass from the northeastern Asian Continent.

Simulation of the atmospheric concentrations of 210Pb and 7Be and comparison with daily observations at three surface sites

The atmospheric transport of 210Pb and 7Be is simulated by the Laboratoire de Météorologie Dynamique general circulation model, LMDz, driven by ECMWF reanalyses. Daily averaged concentrations collected at three surface stations are compared with numerical results for a 1 year (2004) global simulation. The model, with a resolution of 3.75°×2.5° and 19 levels, succeeds in reproducing daily variations of 210Pb and 7Be concentrations. Figures of merit in time (FMT), quantifying the overlapping of the predicted and observed time series over each month, range from 55% to 70%. Sensitivity studies as well as the analysis of numerical signals allow determining the main physical atmospheric processes characterizing the stations on a daily basis. Concentrations of 210Pb at the three stations are particularly sensitive to scavenging in convective updrafts.

Temporal changes of 7Be and 210Pb concentrations in surface air at temperate latitudes (40°N)

Atmospheric concentrations of 7Be and 210Pb were measured for 15 years (1987–2001) in ground-level air at Thessaloniki, Northern Greece (40°38′N, 22°58′E). Mean activity concentrations of 7Be and 210Pb were 5.02 mBq m −3 and 664 μBq m −3, respectively, characteristic of the latitude of 40°N. Monthly atmospheric concentrations of 7Be showed a strong seasonal trend with the highest values being observed in the summer and the lowest in the winter period. Multiple regression analysis of the data of 7Be concentrations and a number of meteorological parameters revealed that the sunspot number and temperature are the most significant parameters affecting the concentrations of 7Be in surface air. The observed strong positive correlation between the mean monthly concentrations of 7Be and the temperature confirms that the increased rate of vertical transport within the troposphere, especially during the warm months, has as a result to carry down to the surface layer air masses enriched in 7Be. Highest values of the mean monthly atmospheric concentrations of 210Pb were observed in the autumn and lowest in the spring period. The positive correlation that was observed between 210Pb and 7Be concentrations during the summer months suggests that these two radionuclides could be used together as tracers of environmental processes.

Atmospheric concentration of 210Pb and 7Be at Sarufutsu, Hokkaido, Japan

The atmospheric concentration of 210Pb and 7Be was observed at Sarufutsu on the coast of the Sea of Okhotsuk in Hokkaido, Japan. Measurements were carried out during the period from February to August, 2001. The atmospheric concentrations of 210Pb and 7Be ranged from 0.2 to 2.5 mBq/m3 and from 0.0 to 4.2 mBq/m3, respectively. The seasonal variation pattern of the atmospheric concentration of 210Pb indicated that the air mass from Chinese Continent reached the coast of the Sea of Okhotsuk.

Atmospheric Concentrations of 210Pb and 7Be over the Western Pacific Ocean.

Atmospheric concentrations of 210Pb and 7Be were observed in the region of the western Pacific Ocean with aerosol samples collected on board in cruises from Fremantle, Australia, to Kobe, Japan. Observations were carried out during the period from the end of August to early September in 1993 and 1994.The atmospheric concentrations of 210Pb and 7Be ranged from 0.0 to 1.4 mBq/m3 and from 1.1 to 9.5mBq/m3, respectively, and both nuclides exhibited a similar distribution pattern along the two cruising routes. The atmospheric concentrations of both nuclides observed in the 1994 cruising were generally higher than those in the 1993 cruising.

Determination of atmospheric lead-210 by alpha-scintillation counting of air filters

Alpha-counting of filters used to sample large volumes of air provides a convenient way of determining atmospheric concentrations of210Pb. Following decay of short-lived222Rn and220Rn progeny, alpha activity of the filters increases as210Pb decays to210Po. After transient equilibrium is reached at about 3 y, alpha activity diminishes with the 22.3 y halflife of210Pb. The degree of equilibrium between210Pb and210Po can be calculated subsequent to sampling, and the average concentration of210Pb in the air during the sampling period can be computed. Contributions to the total210Pb from ambient short-lived radon progeny are small, typically 2–4%. Using high volume air samplers with collection rates of 1.1–1.7 m3/min for 24 h periods, and using counting times of 2 h for 20 cm2 filter sections, we measured alpha counts ranging from 0.0100±0.0050 to 0.200±0.0200 dps. Periodic measurements on 100 of these filters over a 4 y period yielded mean210Pb levels with standard deviations less than ±15%. The method requires minimal sample preparation and can be used to determine past atmospheric210Pb concentrations on filters stored for up to 20 y and more.

Seasonal variation of atmospheric concentrations of 210Pb and 7Be at Tsukuba, Japan, with a possible observation of 210Pb originating from the 1991 eruption of Pinatubo volcano, Philippines.

Concentrations of 210Pb and 7Be in the surface air were measured at Tsukuba Science City (36°03′N, 140°07′E), Japan, during the period of November 1987 to May 1992. The air concentrations of 210Pb and 7Be ranged from 0.2 to 0.8 mBq/m3 and from 1 to 6 mBq/m3, respectively. Seasonal variation of 210Pb concentration was similar to that of 7Be, showing a “two-peak” variation pattern: high concentrations appeared in the spring and the fall. This variation pattern was formed on the 210Pb concentration generated from 222Rn in the surface air. This was interpreted as part of 222Rn emitted from the ground surface may be transported upwards to accumulate long-lived 210Pb in the lower part of the stratosphere. It may then subside into the troposphere with the cosmogenic 7Be through the tropopause break, during the spring, and along the descending currents, including those which accompany the migratory anticyclones passing frequently over Japan during the spring and fall. Unusual and temporal increase in the 210Pb concentration and in the 210Pb/7Be activity ratio observed in the winter months of 1991-1992 may be attributed partly to the 210Pb fallout originating from the 1991 eruption of Pinatubo volcano, Philippines.

Effects of polonium-210 on determination of atmospheric gross alpha-radioactivity

Ingrowth and decay of210Po on air filters used for gross alpha-determination can lead to errors in estimation of long-lived airborne radioactivity. Interferences are present to some degree in all samples and change with time, making the gross alpha-technique quantitatively invalid. However, since the degree of equilibrium between210Po and its parent210Pb can be calculated at any time after filter collection, it should be possible to use the gross alpha-method to estimate past atmospheric concentrations of210Pb. Measurements on filters after elapsed times of up to 15 years show that such determinations are feasible.