PART X — ENVIRONMENTAL CONTAMINANTS 



ent time is 0.8 parts per million per 

 year for an atmosphere containing 

 about 320 parts per million. About 

 40 percent of the carbon dioxide so 

 introduced still remains in the atmos- 

 phere. 



The main sink for this added 

 carbon dioxide has not yet been es- 

 tablished, although it is most prob- 

 ably the deep ocean. There have 

 been suggestions that land plants, 

 through more extensive growth, have 

 accommodated this additional carbon 

 dioxide. Whether such introductions 

 have increased plant productivity in 

 the sea through the input of addi- 

 tional carbon dioxide to the surface 

 waters and whether the earth's tem- 

 perature has increased through the 

 "greenhouse effect" created by this 

 excess carbon dioxide are questions 

 not yet resolved. 



The search for the sinks of the 

 products of fossil-fuel combustion 

 has widened our knowledge of nat- 

 ural phenomena. For example, at 

 one time it was thought that the 

 fate of carbon monoxide, resulting 

 from the incomplete combustion of 

 fossil fuels, was either an atmospheric 

 oxidation or an uptake by seawater. 

 Surface seawaters have carbon mon- 

 oxide concentrations ten to forty 

 times higher than atmospheric equi- 

 librium values and the marine en- 

 vironment turns out to be a source 

 for carbon monoxide. Mid-tropo- 

 spheric concentrations in the sub- 

 tropics display no marked differences 

 between the two hemispheres, indi- 

 cating that the source of the carbon 

 monoxide is natural and that the 

 atmospheric lifetime of the gas is 

 of the order of a year or longer. 

 Higher values of carbon monoxide 

 have been found in the air over open 

 ocean waters as compared to the air 

 over bay and river waters. 



Preliminary calculations of the 

 oceanic output give a value of the 

 order of ten million tons per year, 

 about five percent of the 200 million 

 tons annually generated by the burn- 

 ings of fossil fuel. The sources of the 



carbon monoxide in the oceans are 

 probably biological — through the 

 bacterial or photochemical oxidation 

 of organic matters in surface waters or 

 through the direct production by 

 marine algae, "Portuguese Men of 

 War," or siphonophores. 



The disposition of the carbon 

 monoxide in the atmosphere is not 

 yet known. The principal sink will 

 probably turn out to be stratospheric 

 oxidation by OH, H-O.., or HO- radi- 

 cals. Another possible fate of the 

 carbon monoxide may be an oxidation 

 to carbon dioxide by soil bacteria. 



Insights into Natural Processes 



The researches with carbon mon- 

 oxide illustrate a common result 

 of environmental studies — we learn 

 about natural processes through in- 

 vestigations of pollutants. Such was 

 the case with the radioactive species 

 introduced through the detonation of 

 nuclear devices both in the atmos- 

 phere and in the oceans; our knowl- 

 edge of mixing processes within these 

 two geospheres was decidedly en- 

 hanced. In addition, marine eco- 

 logical research has been sponsored 

 primarily by atomic-energy agencies 

 that are concerned about the inter- 

 actions of radioactive species pro- 

 duced by fusion and fission reactions 

 with members of the biosphere. 



Complementarily, guidance as to 

 the fates of man-introduced materials 

 to the atmosphere-ocean system can 

 come from knowledge about the nat- 

 ural substances involved in the major 

 sedimentary cycle. 



Atmospheric Transport — Over the 

 past decade, the transport of solids 

 to the marine environment by at- 

 mospheric paths has become a most 

 attractive area of research. More than 

 a century ago, Darwin had suggested 

 that major expanses of sediment on 

 the open ocean sea floor are the result 

 of an atmospheric transport from 

 continental arid regions. Yet only 

 recently have we been able to state 

 with some confidence that most sedi- 



mentary solids in the North Pacific, 

 North Atlantic, and Arabian Sea are 

 derived from the continents by wind 

 transport. Perhaps more important 

 is the observation that the geographic 

 distribution patterns of diagnostic 

 minerals in the deposits moderately 

 well define the bounds of the wind 

 systems. For example, in the North 

 Pacific the concentration gradients of 

 the clay mineral illite and of quartz 

 in the sediments closely parallel the 

 gradients in the intensity of the jet 

 stream averaged over a year. Simi- 

 larly, off the west coast of Australia, 

 the prevailing southeasterly winds 

 are recorded in the sediments by high 

 concentrations of the clay mineral 

 kaolinite that they carried from the 

 Tertiary laterite deposits on land. 



Atmospheric Dust — Removal of 

 solids from the atmosphere takes 

 place through scavenging by precipi- 

 tation, rain, snow, sleet, and rime 

 and by gravitational settling, with the 

 former process being the more im- 

 portant. Since the average time be- 

 tween rains in many parts of the 

 world is counted in weeks, transport 

 of suspended particles can take place 

 over great distances. Dust collected 

 on the island of Barbados originated 

 in the European-African continents 

 with a transport by the northeast 

 trade winds. Such materials were 

 also picked up further along their 

 transport path in the glaciers of 

 Mexico. 



The industrial activities of civiliza- 

 tion are recorded in such dusts. Many 

 atmospheric solid samples collected 

 in the Atlantic are gray to dark gray 

 in color due to pollution by carbon 

 and fly-ash spherules. Increases in 

 the rate of dust accumulated in the 

 Caucasus glaciers have been related 

 to the mechanization and indus- 

 trialization of eastern Europe. The 

 dust accumulation rate clearly shows 

 marked increases beginning in 1950, 

 which parallels the growth in the 

 Soviet economy. (See Figure X-15) 



Possibly, a more pertinent case for 

 the impact of man upon the marine 



358 



