Temporal variations of atmospheric depositional fluxes of ⁷Be and ²¹⁰Pb over 8 years (2006–2013) at Shanghai, China, and synthesis of global fallout data

Abstract

7Be and 210 Pb, two atmospherically delivered radionuclides, have been broadly applied to study the processes including air mass transport, soil erosion, and particle cycling in aqueous systems. These studies require temporal variations of their depositional fluxes. In the present work, monthly atmospheric bulk depositional fluxes of Pb. There were strong seasonal variations in the depositional fluxes of these nuclides. The seasonal fraction of depositional fluxes was >30% of the total annual depositional fluxes of Pb depositional fluxes increase with the distance from the coast in inland regions (distance from the coast >50 km) and increase with the amount of precipitation in onshore region (distance from the coast ≤50 km). We also report that Shanghai, China, has the second highest bulk depositional fluxes of 210 Pb in literature.

Seasonal distribution patterns of 7Be and 210Pb in surface sediments in the Changjiang Estuary, China and their implication

“…In the middle latitudes areas, there is an intrusion of stratospheric air in spring so that more 7 Be can transported into the troposphere from the stratosphere, causing the high depositional flux in spring (Feely et al, 1989;Yamamoto et al, 2006). The depositional flux of 210 Pb in Shanghai (with the average of 1.1 Bq m −2 d −1 in 2009 and 0.9 Bq m −2 d −1 in 2010) was much higher than the average values reported for other places (0.18-0.94 Bq m −2 d −1 ) (Du et al, 2015;Poet et al, 1972;Qian et al, 1986;Turekian et al, 1983;Yi et al, 2005), although 7 Be's fluxes were comparable with those in other places (Yi et al, 2005). The high 210 Pb's depositional fluxes in Shanghai are attributed to the influence of the continental air masses with high 210 Pb concentration of dust and the high flux of 222 Rn in China's soil (Du et al, 2008;Kim et al, 1999;Zhuo et al, 2008).…”

Scavenging and fractionation of particle-reactive radioisotopes 7Be, 210Pb and 210Po in the atmosphere

“…Such correlations suggest that given the same rainfall precipitation, more 7 Be and 210 Pb are scavenged in the spring than in non-spring seasons. The increased deposition of 7 Be in the spring has been reported for other locations (e.g., Baskaran, 1995;Su et al, 2003;Du et al, 2015) and attributed to the increased stratosphere-troposphere exchange of air masses in the mid-latitudes. For 210 Pb, the increased deposition is usually attributed to the increased input from the continental air masses where the production of 210 Pb is high due to the high emission of radon from the continents (Turekian et al, 1977).…”

Mobile mud dynamics in the East China Sea elucidated using 210Pb, 137Cs, 7Be, and 234Th as tracers

“…7 Be is derived primarily from direct atmospheric deposition, which depends on the amount of precipitation and secondarily from watershed erosional input; hence, the activities in shallow water sediments vary seasonally due to changes in the amount of precipitation. Atmospheric fluxes of 7 Be collected over 8 years in Shanghai, China indicate that the highest seasonal atmospheric fluxes occurred during the spring months 75% of the time [ Du et al ., ]. In May, the region south of the Changjiang River had higher 7 Be activities, with a decreasing trend from the river mouth to station F3.…”