Aerosol Populations, Processes, and Ages in Bulk Deposition: Insights From a 9‐Year Study of 7Be, 210Pb, Sulfate, and Major/Trace Elements

• Published in: Journal of geophysical research. Atmospheres 2021-11, Vol.126 (21), p.n/a
• Main Authors: Landis, Joshua D., Feng, Xiahong, Kaste, James M., Renshaw, Carl E.
• Format: Article
• Language: English
• Subjects: aerosol; Aerosols; atmosphere; Atmospheric particulates; Atmospheric precipitations; Atmospheric sciences; Beryllium; Beryllium 10; Beryllium 7; Contaminants; Convective storms; Deposition; Dry deposition; Dust storms; Earth; Earth surface; Fallout; Geophysics; Lead isotopes; lead‐210; Manganese; Mercury; Mercury (metal); Nitrogen; Particulate matter; Pollution transport; Populations; Precipitation; Radioisotopes; Rain; Rain water; Rainfall; Rainout; Ratios; Recharge; Recharging; Scavenging; Sediments; Soil; Soil contamination; Solar activity; Storms; Stratosphere; sulfate; Sulfates; Sulphates; Sunspots; Suspended particulate matter; Toxins; Trace elements; Tracers; Transport; Troposphere; Washout
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2021JD035612

We report fallout radionuclide (FRN) and major/trace element (MTE) contributions to bulk atmospheric deposition in Hanover, NH, USA (43.7022°N, 72.2896°W). Deposition of 7Be, 210Pb, and SO4 covary [R2 > 0.4, n = 461] but are discriminated by production sources, depositional mechanisms, meteorological controls, MTE associations, and seasonal biases. 7Be is dominated by rainout (78% of total deposition), recharged by long‐range transport (+23% over mean, o.m.), influenced by stratosphere‐troposphere exchange (+9% o.m.), and solar activity (−2% per doubling of sunspot count). Correlation with particulate nitrogen (+9% per doubling of N) indicates 7Be affinity for biogenic aerosols. 210Pb is dominated by dry + washout deposition (54% of total) and convective storms (+107% o.m), depleted in marine moisture sources (−133% o.m.), correlated with S (+9% per doubling of S), and biased to autumn with Mn, Hg, and V (+7% o.m.). Coincident long‐term declines in S and 210Pb (−14%, −4% per year) suggest co‐scavenging by PbSO4. 7Be:210Pb ratios increase asymptotically with precipitation through the dry‐washout‐rainout transition and recharge of 7Be. At the global scale, 7Be:210Pb increases with precipitation for North American/European sites due to recharge of 7Be in midlatitude storm belts [R2 = 0.64, n = 31]. Conversely, 7Be:210Pb is independent of precipitation for Southeast/East Asian sites where 7Be recharge is low [R2 = 0.01, n = 40]. Globally, 7Be:210Pb ratios in dry deposition reflect resuspended aerosols with mean age of ca. 200 days, contributing