ABSTRACT
Increasing quantities of atmospheric anthropogenic fixed nitrogen entering the open ocean could account for up to about a third of the ocean's external (nonrecycled) nitrogen supply and up to approximately 3% of the annual new marine biological production, approximately 0.3 petagram of carbon per year. This input could account for the production of up to approximately 1.6 teragrams of nitrous oxide (N2O) per year. Although approximately 10% of the ocean's drawdown of atmospheric anthropogenic carbon dioxide may result from this atmospheric nitrogen fertilization, leading to a decrease in radiative forcing, up to about two-thirds of this amount may be offset by the increase in N2O emissions. The effects of increasing atmospheric nitrogen deposition are expected to continue to grow in the future.
Subject(s)
Atmosphere , Human Activities , Nitrogen , Reactive Nitrogen Species , Seawater , Carbon , Carbon Dioxide/metabolism , Ecosystem , Humans , Nitrogen/metabolism , Nitrogen Fixation , Oceans and Seas , Reactive Nitrogen Species/metabolismABSTRACT
The environmental conditions of Earth, including the climate, are determined by physical, chemical, biological, and human interactions that transform and transport materials and energy. This is the "Earth system": a highly complex entity characterized by multiple nonlinear responses and thresholds, with linkages between disparate components. One important part of this system is the iron cycle, in which iron-containing soil dust is transported from land through the atmosphere to the oceans, affecting ocean biogeochemistry and hence having feedback effects on climate and dust production. Here we review the key components of this cycle, identifying critical uncertainties and priorities for future research.
Subject(s)
Climate , Dust , Iron , Seawater , Atmosphere , Carbon Dioxide , Desert Climate , Iron/metabolism , Oceans and Seas , Phytoplankton/physiology , SoilABSTRACT
The concentration of airborne soil dust at Enewetak Atoll(11 degrees N, 162 degrees E) in April 1979 was 2.3 micrograms per cubic meter but decreased steadily to 0.02 microgram per cubic meter over the next 5 months. The spring dust is probably derived from China; its deposition rate ( approximately 0.3 millimeter per 1000 years) suggests that it may be a significant contributor to the deep-sea sediments of the North Pacific.
Subject(s)
Air Pollutants/analysis , Arsenic/analysis , Activation Analysis , Methods , Spectrophotometry, Atomic , TemperatureABSTRACT
Inorganic and organic components of the gaseous tropospheric halogens chlorine, bromine, and iodine have been simultaneously measured. At four diverse remote locations the organic component contained the bulk of the halogen mass, varied less than the inorganic component, and was comparable in concentration to the independently measured halocarbon component.
ABSTRACT
The chemical composition of atmospheric particles collected near sea level over the North Atlantic indicates that Al, Sc, Mn, Fe, Co, Cr, Na, Mg, Ca, K, and Sr are derived from either crustal weathering or the ocean. The elements V, Zn, Cu, Cd, Pb, Sb, and Se are present in concentrations higher than expected from these sources. Although the V is probably derived from pollution sources on the North American continent, a comparison of enrichment factors relative to average crustal material for the remainder of these elements over the North Atlantic with enrichment factors for similar samples collected at the geographic South Pole suggests that the anomalously high enrichment factors may be due to natural rather than anthropogenic sources. A vapor phase for these metals may be involved at their source.
ABSTRACT
The chemical composition of atmospheric particulate material collected at the geographic South Pole indicates that Al, Sc, Th, Sm, V, Mn, Eu, Fe, La, Ce, Co, Cr, Na, K, Mg, and Ca are derived from either crustal weathering or the ocean. The relatively volatile elements Zn, Cu, Sb, Se, Pb, and Br are apparently derived from other sources. Because of their volatility, vapor-phase condensation or a high-temperature dispersion source is suspected for these elements or their compounds.
ABSTRACT
Concentrations of lead, iron, nickel, copper, fatty acids, hydrocarbons, and chlorinated hydrocarbons are enriched from 1.5 to 50 times in the top 100 to 150 micrometers of Narragansett Bay water relative to the bulk water 20 centimeters below the surface. Trace metal enrichment was observed in the particulate and organic fractions but not in the inorganic fraction. If these substances are concentrated in films only a few molecular layers thick on the water surface, the actual enrichment factor in the films may be well over 10(4), resulting in extremely high localized pollutant concentrations in the surface microlayer.
Subject(s)
Fatty Acids/analysis , Hydrocarbons/analysis , Metals/analysis , Water Pollution/analysis , Copper/analysis , Hydrocarbons, Halogenated/analysis , Iron/analysis , Lead/analysis , Nickel/analysis , Rhode Island , Seawater/analysis , Water Pollution, Chemical/analysisSubject(s)
Air Pollution/analysis , Bromine/analysis , Lead/analysis , Hawaii , Sampling Studies , Vehicle Emissions , WeatherSubject(s)
Aerosols/analysis , Air Pollution , Bromine/analysis , Chlorine/analysis , Iodine/analysis , Oceanography , Activation Analysis , Alaska , Antarctic Regions , Hawaii , Massachusetts , Trace Elements/analysisABSTRACT
Sediments from a unique high-altitude lake on Hawaii indicate ash falls and other airborne and waterborne materials for a period estimated to extend into the Pleistocene.