Continental dust flux

Continental dust flux is the main natural source of chromium in the atmosphere volcanic dust and gas flux are minor natural sources of chromium in the atmosphere (Fishbein 1981). Chromium is released into the atmosphere mainly by anthropogenic stationary point sources, including industrial, commercial, and residential fuel combustion, via the combustion of natural gas, oil, and coal. Other important anthropogenic stationary point sources of chromium emission to the atmosphere are metal industries. It... 

Fluxes of continental dust preserved in ice cores of Greenland and Antarctica suggest a 30-fold increase in dust flux during the last Glacial Maximum. Dramatic increases in new biological production in the HNLC regions may have resulted, resulting in the draw-down of atmospheric CO2 (Martin, 1990). 

The overall effect of the terrestrial weathering reactions has been the addition of the major ions, DSi, and alkalinity to river water and the removal of O2, and CO2 from the atmosphere. Because the major ions are present in high concentrations in crustal rocks and are relatively soluble, they have become the most abimdant solutes in seawater. Mass-wise, the annual flux of solids from river runoff (1.55 x 10 g/y) in the pre-Anthropocene was about three times greater than that of the solutes (0.42 x 10 g/y). The aeolian dust flux (0.045 X 10 g/y) to the ocean is about 30 times less than the river solids input. Although most of the riverine solids are deposited on the continental margin, their input has a significant impact on seawater chemistry because most of these particles are clay minerals that have cations adsorbed to their surfaces. Some of these cations are desorbed... 

Higgins S. M., Anderson R. F., Marcantonio F., Schlosser P., Stute M., Schwarz B., Frank M., and Strobl C. Fluxes of Extraterrestrial He, continental dust, and opal in North Pacific sediments over the past 7 Ma. Paleoceanography (submitted for publication). 

The major element content and mineralogy of air-borne particles reflect closely those of continental soils and shales, although atmospheric particulates also include materials of oceanic origin (Delaney et al., 1967), and show considerable enrichments in some trace metals (Buat-Menard and Chesselet, 1979). The average composition of shales and soils (Table 9.8) was chosen to represent the properties of dust transported from the continents to the ocean. Fluxes of elements in atmospheric transport to the ocean are given in Table 9.14. 

Solids eroded from the continental surface account for about 80% of the material mass transport (Table 3). Most of the solid material flux, about 95% of it, is carried by water discharge and the remaining 5% are transported by winds. The total suspended material load of rivers and the dust load of the atmosphere include products of the bedrock erosion as well as materials eroded from clastic and biogenic sediments exposed on the continents. Equating the sum of the riverine and atmospheric transport fluxes of solids with the rate of continental erosion or mechanical denudation implies that a part of the eroded mass that is stored in clastic sediments on land remains constant (Fig. 4) ... 

A few of the U/Th nuclides are supplied to the sea via atmospheric deposition and diffusion through sediment pore waters. Decay of Rn in the atmosphere to °Pb and its subsequent removal by wet and dry deposition is an important source of dissolved °Pb to the sea. As the bulk of the Rn in the atmosphere is of continental origin, the flux of °Pb via this route depends on factors such as distance from land and aerosol residence times. °Po is also deposited on the sea surface through this source, but its flux is <10% of that of °Pb. Leaching of atmospheric dust by sea water can also contribute to nuclide fluxes near the air-sea interface, this mechanism has been suggested as a source for dissolved Th. 

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