Sediment, ocean, impact

Milliman J.D. and Kao J.S. (2005). Hyperpycnal discharge of fluvial sediment to the ocean Impact of Super-Typhoon Herb (1996) on Taiwanese rivers. Journal of Geology, 113, 503-516. 

Christensen J. P., Murray, J. W., Devol, A. H. and Codispoti, L. A. (1987). Denitrification in continental shelf sediments has major impact on oceanic nitrogen cycle. Glob. Biogeochem. Cycles 1,97-116. 

Thomas M. Church. From Meteorites to Man The Patterson Geochemical Heritage. Unpublished manuscript. Source for the impact of Patterson s Ph.D. thesis on geologists few understood age of Earth work ocean sediments MIT sabbatical, Hardy and biology Goldberg s tip Schaule device and lead-free rats. 

Geologists have deemed it necessary to recognize this new epoch because sediments now accumulating on the seafloor are chemically distinct from those whose origins predate human impacts on the crustal-ocean-atmosphere factory. 

The sedimentary and metamorphic rocks uplifted onto land have become part of continents or oceanic islands. These rocks are now subject to chemical weathering. The dissolved and particulate weathering products are transported back to the ocean by river runoff. Once in the ocean, the weathering products are available for removal back into a marine sedimentary reservoir. At present, most mass flows on this planet involve transport of the secondary (recycled) materials rather than the chemical reworking of the primary (juvenile) minerals and gases. The natirre of these transport and sediment formation processes has been covered in Chapters 14 through 19 from the perspective of the secondary minerals formed. We now reconsider these processes from the perspective of impacts on elemental segregation between the reservoirs of the crustal-ocean-atmosphere factory and the mantle. 

The last include wet and dry deposition of particles and solutes and gas exchange across the air-sea interface. Because of proximity to source, coastal waters tend to be more polluted than the open ocean. A notable exception is the worldwide acidification of surface waters caused by CO2 emissions. Of all the coastal waters, estuaries tend to be the most impacted. This is due to high rates of pollutant loading and to natural processes that act to concentrate these pollutants in the local sediments and biota. This is most unfortunate as estuarine waters support the world s largest fisheries and are where recreation is concentrated. 

Syvitski JPM, Vorosmarty CJ, Kettner AJ, Green P (2005) Impact of humans on the flux of terrestrial sediment to the global coastal ocean. Science 308 376-380... 

Thousands of tonnes of methyl chloride are produced naturally every day, primarily in the oceans. Other significant natural sources include forest and brush fires and volcanoes. Although the atmospheric budget of methyl chloride can be accounted for by volatilization from the oceanic reservoir, its production and use in the manufacture of silicones and other chemicals and as a solvent and propellant can make a significant impact on the local atmospheric concentration of methyl chloride. It has been detected at low levels in drinking-water, groundwater, surface water, seawater, effluents, sediments, in the atmosphere, in fish samples and in human milk samples (Holbrook, 1993 United States National Library of Medicine, 1998). Tobacco smoke contains methyl chloride (lARC, 1986). 

Esser and Turekian (1988) estimated an accretion rate of extraterrestrial particles in ocean bottom and in varved glacial lake deposit on the basis of osmium isotope systematics and concluded a maximum accretion rate of between 4.9 x 104 and 5.6 x 104 tons/a. The discrepancy between this estimate and those derived from helium can easily be attributed to the difference in the size of the cosmic dust particles under consideration. Cosmic dusts of greater than a few ten micrometers may not be important in the helium inventory of sediments because the larger grains are likely to lose helium due to atmospheric impact heating (e.g., Brownlee, 1985). Stuart et al. (1999) concluded from studies on Antarctic micrometeorites that 50- to 1 OO-qm micrometeorites may contribute about 5% of the total flux of extraterrestrial 3He to terrestrial sediments. Therefore, the helium-based estimate deals only with these smaller particles. 

One of the major environmental issues of our time is the impact of anthropogenically generated CO2 on the environment (see Chapter 9 for discussion). The major processes associated with fossil fuel CO2 in the oceans are the uptake of fossil fuel CO2 by the upper ocean, mixing and transport within the ocean, and reaction with calcium carbonate in sediments. In addition, biologic productivity may be influenced by increased Pc02 values- The two major reactions for uptake of CO2 by the oceans, beyond those that would occur for a chemically unreactive gas, are in a simple form ... 

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