Cadmium anthropogenic sources

The contribution of the external European anthropogenic sources to cadmium depositions in Europe in 2002 varies from 4 to 75%. In 17 countries it exceeded 50%. The countries most affected by the trans-boundary transport of cadmium are Belarus, Ukraine, Lithuania, and Czech Republic. These countries are located close to Poland, which is a significant emitter of cadmium. Similar to lead, the lowest contributions are observed in Spain and Iceland. The contribution of the trans-boundary transport to pollution of the European Union with cadmium is about 15%. 

Annual emissions of heavy metals from the anthropogenic sources of HELCOM countries significantly decreased during the period of 1990-2001. In particular, annual emissions of cadmium decreased by 45%, whereas lead and mercury emissions reduced by 60%. Following this reduction and also due to the changes of heavy metals emissions in other European countries the level of atmospheric depositions to the Baltic Sea has also significantly decreased (Figure 20). Compared to 1990... 

The main anthropogenic sources of arsine include its accidental formation, particularly in the chemical and nonfer-rous (like zinc, copper, and cadmium) metallurgical industries, production or use of the gas itself during manufacture of semiconductors as a doping agent (Aposhian, 1997 Winski et al, 1997) and in battery production as an alloy with lead (Wald and Becker, 1986). 

Cook and Morrow 1995, Anthropogenic Sources of Cadmium in Canada, National Workshop on Cadmium Transport Into Plants, Canadian Network of Toxicology Centres, Ottawa, Ontario, Canada, June 20-21,1995. 

Cadmium deposited from the atmosphere onto soil can come from a variety of natural and anthropogenic sources (Alloway and Steinnes, 1999 McArthur, 2001). It is estimated that volcanoes, the dominant natural source of atmospheric Cd, emit 520 mg of Cd into the atmosphere aimually. The dominant anthropogenic source of emission of Cd into the atmosphere is primary non-ferrous metal production, which accounts for an estimated 4721 mg of Cd emitted into the atmosphere annually. The amount of Cd emitted into the atmosphere from all anthropogenic sources is estimated to be about one order of magnitude greater than that emitted from all natural sources. 

Some inotganic ionic species found in water are primarily from anthropogenic sources. The majority of these ions are heavy metals such as cadmium (Ca" " ), chromium (Cr+, Cr+ ), lead (Pb+ ), and mercury (Hg+ ) that tend to accumulate in living oiganisms until toxic levels are attained. 

Worldwide cadmium production at present is around 17 000 metric tons/year and the global emission of cadmium compounds into the atmosphere is estimated to be 7000 metric tons/year, mainly from anthropogenic sources (Stoeppler 1991). 

As a rule, simulations consider emissions of heavy metals from anthropogenic and natural sources, transport in the atmosphere and deposition to the underlying surface (Figure 6). It is assumed that lead and cadmium are transported in the atmosphere only as a part of aerosol particles. Besides, chemical transformations of these metals do not change removal properties of their particles-carriers. On the contrary, mercury enters the atmosphere in different physical and chemical forms and undergoes numerous transformations during its pathway in the atmosphere (Ilyn et al., 2002 2004 Ilyin and Travnikov, 2003). 

Each country is not only a receptor but also a source of the trans-boundary transport. As much as 153 t (60% of anthropogenic emission in Europe) of cadmium, emitted in Europe, leaves the territory of the counties and is involved in the long-range transport. The highest absolute value—30 t/yr—of cadmium transported across national borders was obtained for Poland. The significant exporters of cadmium are Spain, the Russian Federation, Romania and Italy. Nearly 40 t of cadmium is transported outside the European Union. Besides, only nine countries control more than 75% of cadmium trans-boundary transport. 

For each sea the contribution of various emission sources to atmospheric depositions was assessed. It is obvious that the countries with high emissions, located close to the seas, make the highest contributions to anthropogenic depositions. For example, the most significant contribution to the North Sea comes from the United Kingdom (28%) and Germany (16%). The main anthropogenic contributor to the Caspian Sea is Russia (46%), followed by Azerbaijan (22%) and Turkey (12%). Similar information is also available for cadmium and mercury. 

Biological, chemical, and physical effects of airborne metals are a direct function of particle size, concentration, and composition. The major parameter governing the significance of natural and anthropogenic emissions of environmentally important metals is particle size. Metals associated with fine particulates are of concern particles larger than about 3-fjim aerodynamic equivalent diameter are minimally respirable, are ineffective in atmospheric interactions, and have a short air residence time. Seventeen environmentally important metals are identified arsenic, beryllium, cadmium, chromium, copper, iron, mercury, magnesium, manganese, nickel, lead, antimony, selenium, tin, vanadium, and zinc. This report reviews the major sources of these metals with emphasis on fine particulate emissions. 

---