Soil selenium content

Indicator plants generally have an offensive odor, which varies with the selenium concentration. Other vegetable matter grown on seleniferous soils may have a sufficiently high selenium content to be toxic when ingested by animals or humans. Apart from appearance in these seleniferous plants, selenium has been considered as a variable contaminant. Selenium is a necessary micronutrient in living organisms, needed by humans as well as animals (see Mineral NUTHiENTs). 

The literature on the distribution of natural selenium in the soils, the absorption by vegetation, the toxicity of compounds of either natural or applied selenium to man and animals, and the use of selenium as a spray for insect control is voluminous and no attempt is made to cover it here. The literature has been well reviewed fairly recently ( ). Very little has been published on the increase in selenium content of apple peelings, due to the application of selenium-bearing sprays. 

The average selenium content of the earth s crust is about 0.8 mg/kg (Aubert and Pinta, 1977). Carbonated rocks contain higher Se (0.8 mg/kg) than metamorphic and sedimentary rocks (0.6 mg/kg) and igneous rocks (0.5 mg/kg) (Aubert and Pinta, 1977). Most of the world s soils contain 0.03-2 mg/kg Se (Ure and Berrow, 1982) with a mean of 0.4 mg/kg. In the U.S., the total Se concentration ranges from trace amounts to 82 mg/kg (Adriano, 2001). 

Selenium is an essential trace element for optimal health but an excess is toxic. The British population is now reckoned to be selenium deficient because more European wheat is now used to make bread at the expense of North American wheat. The difference in the selenium content is caused by the difference in the selenium content of the soils. In geological terms, European soil is older and the selenium has washed out. 

In the lower fan areas Se concentrations were monitored up to 400 pg/L. Similar historical distribution of soil Se content and shallow groundwater content indicate that dissolved selenium species were leached from saline soils by irrigation water. The drainage discharge of shallow groundwater and subsurface irrigation water was accompanied by increasing accumulation of Se in Kesterson Reservoir. 

The distribution of both endemic diseases has been found to relate to selenium content in the soils. The two diseases are distributed mainly in a distinct wide belt, usually referred to as the disease belt, running from the northeast to southeast of China and located in the middle transition belt from the southern coast to the northwest inland region (Figures 3 and 4). 

The belt is mainly represented by Temperate Forest ecosystems on forest-steppe soils (Brown Earth). The analyses of selenium content in various links of the biogeochemical food web (rock, water, soils, grains, hair, etc.) has shown that these... 

The selenium content of a plant is dependent on the plant species and on whether it is grown in seleniferous or non-seleniferous soil. Generally, Se content in plants increases with the level of Se available and decreases with the sulphur supply. Se concen-... 

S. Blagojevic, M. Jakovljevic, B. Zarkovic, InBuence of long-term fertilization on the selenium content of calcareous chernozem soil, J. Environ. Pathol. Toxicol. Oncol., 17 (1998), 183 D187. 

When the soil selenium decrease from the coast to the inland was proved, it was easy to understand that muscle degeneration in domestic animals due to selenium deficiency (Mikkelsen and Hansen, 1967, 1968) was concentrated in the valleys with low precipitation in the eastern part of Norway. Our neighbour country Finland, with a mostly typical continental climate, has from an early stage taken up the problem by adding selenium to the cattle fodder. In Finland, and in other Scandinavian countries as well, there is now a discussion on the possibilities of adding a selenium compound to commercial fertilizers to increase the selenium content in the plants. 

Generally, there is a strong correlation between the selenium content of rocks and the sediments and soils derived from them. Soil selenium concentrations are typically in the range 0.01-2 mg kg with a world average of 0.4mgkg Extremely high concentrations (up to 1,200 mg kg ) have been found in some... 

Several techniques are available to assess selenium bioavailability in soils. The most widely used is the water-soluble concentration (Fordyce et al., 2000b Jacobs, 1989 Tan, 1989). In most soils, only a small proportion of the total selenium is in dissolved form (0.3-7%), and water-soluble selenium contents are generally <0.1mgkg (Table 8). 

Wells, N., 1967. Selenium content of soil-forming rocks. N.Z. J. Geol. Geophys., 10 198—208. 

Selenium enters the food chain mainly as selenomethionine from plants that take the element up from the soil but do not appear to use it. The soil content of selenium is highly variable and can be low in volcanic soils when soluble salts are leached out by ground water. Soils in parts of China and New Zealand are particularly low in selenium. Acid soils, where insoluble selenium complexes can be formed with iron and aluminum, occur in some parts of Europe, resulting in low available soil selenium. The geographical source of plant and animal foodstuffs determines the level of dietary intake. In the United States and Canada, wheat and other cereal products are a good source of selenium average intakes in North America range from 80 to 220 fig Se per day, whereas in the UK dietary intake is about 30 to 60 Llg/day. Intakes in China are as low as 11 lg/day and in New Zealand 28 fig/day. ... 

The spatial heterogeneity of selenium content in rocks, various soils, and especially the peculiarities of its translocation from soils to plants, lead to the formation of so-called selenium biogeochemical provinces (see Chapter 7 Biogeochemical mapping ). These provinces are characterized by a deficient or excessive concentration of this trace metal in all links of biogeochemical food webs. Selenium deficiency in fodder crops is related to the less than 30 ppm content of this element (Table 8). This leads to myopatia (white colored animal tissues), necrotic degeneration of kidney, exude diathesis. The addition of sodium selenite is used for prevention of these diseases. 

An examination of thyroid hormone levels in lactating women residing in areas of Venezuela with high levels of selenium in the soil (selenium intake ranged from 250 to 980 pg per day as estimated from selenium content of breast milk) revealed a significant decrease in serum T3 levels, as compared with... 

The primary factor that controls selenium concentrations in soil is the selenium content of the parent bedrock materials that release selenium via weathering processes and leaching (NAS 1976a). Natural weathering processes are thought to release about 100,000-200,000 metric tons of selenium per year (Andren and Klein 1975). Atmospheric deposition of selenium also contributes to selenium in the soil. 

Cappon CJ. 1981. Mercury and selenium content and chemical form in vegetable crops grown on sludge amended soil. Arch Environ Contam Toxicol 10 673-690. 

USDA. 1961. Selenium content in soils. Agriculture Handbook 200. Washington, DC U.S. Department of Agriculture, 27-34. 

These findings are also translatable to HIV/AIDS Senegal has only 1.77% of its population infected with HIV-1, whereas Zimbabwe — with a very low selenium content in its soil — has an incidence over 25%. 

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