Trace elements global cycling

Lantzy RJ and McKenzie FT (1979) Atmospheric trace elements global cycles and assessment of man s impact, Geochim Cosmochim Acta 43 511-525. 

In contrast to their rather low dissolved concentrations in seawater, some of the trace metals, e g., iron and aluminum, along with oxygen and silicon, comprise the bulk of Earth s crust. Some trace elements are micronutrients and, hence, have the potential to control plankton species composition and productivity. This provides a connection in the crustal-ocean-atmosphere fectory to the carbon cycle and global climate. 

The role of the ocean in the global biogeochemical cycling of trace elements is the subject of this chapter. The processes that introduce and remove these elements from the ocean are summarized in Figure 11.2 and discussed in detail next. 

In a number of studies, the elemental composition of aerosol particles has been related to their source. Schroeder and co-workers (1987) review the sources, sinks, analysis, deposition, chemical forms, and global cycles of various trace elements. Because the relative amounts of trace elements vary for coal compared to oil-fueled power plants, for example, it has been suggested that certain elements or ratios of elements may serve as tracers for various sources (e.g., see Gordon, 1988 and Rahn and Lowenthal, 1984). Thus V and Ni are indicative of oil combustion, and elevated concentrations of elements such as As and Se are usually... 

Finally, we must somehow resolve the vexing problem of the chemical speciation of trace elements in seawater what is the chemical nature of the various metal chelators whose existence has been demonstrated by electrochemistry Is the chemistry of several metals in surface seawater really controlled by metallophores released by prokaryotes Or are dissolved metals chiefly present as parts of metalloproteins in the process of remineralization How do metal chelators affect the residence times of metals (in particular, scavenged elements such as iron and cobalt) and in turn how do those chelators influence the global carbon cycle via changes in marine primary productivity ... 

Particles represent important agents of transport in global ocean cycles of many trace elements, of carbon, and of other substances. Once introduced into the oceans, many trace elements are removed from seawater by scavenging (sorption, com-plexation, and other forms of surface reactions) to particles (Goldberg, 1954 Turekian, 1977). Scavenging and burial in marine sediments represents the principal loss process influencing the biogeochemical cycle of many trace elements in the ocean (Li, 1981). 

Martin J.-M. and Windom H. L. (1991) Present and future roles of ocean margins in regulating marine biogeochem-ical cycles of trace elements. In Ocean Margin Process in Global Change (eds. R. F. C. Mantoura, J.-M. Martin, and R. Wollast). Wiley-Interscience, New York, pp. 45-67. 

Figure 3.15 Correlation between trace-element concentrations in streams and permissible concentrations in water supplies. From R. M. Carrels et al. 1975. Chemical cycles and the global environment.

Iron-sulfide minerals are important sinks for iron and sulfur as well as for trace metals and play an important role in the global cycles of these elements. Over the past 30 years extensive studies -... 

Description. Molybdenum is an essential trace element for virtually all life forms. It functions as a cofactor for a number of enzymes that catalyze important chemical transformations in the global carbon, nitrogen, and sulfur cycles. ... 

Church TM, Veron A, Patterson C, Settle D, Erel Y, Maring H, Flegal AR (1990) Trace elements in the north Atlantic troposphere Shipboard results of precipitation and aerosols. Global Biogeochem Cycles 4 431-443. 

An important block of the MBWB is the methods of determination of various parameters of the water cycle. Such methods are based on the use of surface, satellite, and airborne measurements. The MBWB used as a global model makes it easier to understand the role of the oceans and land in the hydrological cycle, to identify the main factors that control it, as well as to trace the dynamics of its interaction with plants, soil, and topographic characteristics of the Earth surface. It is based on the interaction between the elements of the water cycle, and takes natural and anthropogenic factors into account by means of information interfaces with other units of the global model (Krapivin and Kondratyev, 2002). 

---