Other Inorganic Nutrients

There is some evidence that chromium (Cr ), silicic acid (Si(OH)4) or related silicon-based compounds, borate (8407 ), nickel (NP ), and arsenate (AsOf ) are required inorganic nutrients. However, the available evidence tends to be not convincing to all researchers (Reeves, 1997). The functions of arsenate and nickel are not clear. There is some indication that arsenate is used in the metabolism of sulfur-containing amino acids. An experimentally induced deficiency in arsenate or nickel results in impaired growth. 

Chromium is a trivalent cation that occurs as Cr . A typical daily intake is 0.5-3.8 xmol (25-200 p.g/day). After absorption from the diet, chromium occurs boimd to transferrin. A safe and adequate intake of 50 to 200 ig Cr/day has been established. Chromium appears to participate in glucose metabolism. The ion may play a part in mediating the hormonal effects of insulin. Chromium deficiency results in abnormally high glucose tolerance curves and impaired clearance of plasma glucose. Chromium deficiency can be induced in animals. There is evidence that 

The usual dietary intake of borate is about 0.1 mmol/day. Borate occurs as B(OH)3 and B(OH), and also occurs as weak, covalent complexes with sugars. Borate never occurs in biology as free boron atoms. Dietary borate is readily absorbed by the gut, and most of this chemical is excreted in the lu-ine. Studies wifii humans have revealed that 88-97% of dietary borate is excreted in the urine (Himt et al., 1997). There is some evidence that borate deficiency provokes a further decline in health during vitamin D deficiency. 

Silicon appears to be required for the normal synthesis of the organic matrix of bone and for its normal calcification. The silicon in the blood serum occurs entirely as silicic acid. Osteoblasts may contain the highest concentrations of silicon of all the cells of the body. Mthin these cells, silicon occurs mainly in the mitochondria. Silicon deficiency in animals results in bones with abnormal structiues. These abnormalities include thinner cortical bone, reduced bone flexibility, and flattened cranial bones. Silicon deficiency also affects cartilage, and results in a dramatic reduction in the width of the epiphyseal cartilage (Carlisle, 1985). 

Cobalt is a required mineral since it is a vital component of vitamin B12. There is no reason to believe that extra cobalt needs to be supplied, in addition to that occurring in dietary cobalamin. 

There is some evidence that chromium Cr ), silicic acid (SitOH) ) or related silicon-based compounds, borate nickel and arsenate (AsO ) are 

The usual dietary intake of borate is about D.l mmol/day. Borate occurs as B(OH)j and and also occurs as weak, covalent compleKes with sugars. Borate 

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Water, sodium, potassium, and chloride are discussed first in this chapter because disturbances in the metabolism of these nutrients arc more serious and more widespread than disturbances involving the other inorganic nutrients. Iodine is discussed next because deficiencies in this nutrient, widespread in some areas of the world, lead to serious and irreversible problems. Iron follows, as moderate deficiencies in this nutrient occur in all regions cjf the world. Iron deficiency is often associated with increased iosses of the nutrient rather than with the consumption of poor diets. 

Some inorganic nutrients are distinguished as being stored in the body. They are stored in a reservoir that can be tapped during periods of a dietary deficiency. These nutrients are iron, calcium, and phosphate. Most of the other inorganic nutrients tend not to be stored in usable, mobilizable forms in the body. 

The data on the effects of the concentration of other inorganic nutrients on the growth rate is less complete. Since algae use carbon dioxide as their carbon source during photosynthesis, this is clearly a nutrient which can reduce the growth rate at low concentrations (43). Reported saturation concentration for Chlorella is < 0.1% atm (24). 

Except for the development of on-line systems for nutrients monitoring, the measurement of other inorganic non-metallic constituents is rather rare. Some commercial systems based on electrochemical sensing are proposed for the measurement of cyanide. A simple and rapid procedure for sulphide measurement in crude oil refinery wastewater has been developed [ 32 ]. Based on the de-convolution of the UV spectrum of a sample, this method has a detection limit of 0.5 mg L 1 and has been validated for crude oil refinery wastewater. 

BTEX bioremediation projects often focus on overcoming limitations to natural degradative processes associated with the insufficient supply of inorganic nutrients and electron acceptors. However, other limitations associated with the presence and expression of appropriate microbial catabolic capacities may also hinder the effectiveness of bioremediation. Thus, while subsurface addition of oxygen or nitrate has proven sufficient to remove BTEX below detection levels [134,145,292,315,316], it has been only marginally effective at some sites [6]. Sometimes, the concentration of a target BTEX compound fails to decrease below a threshold level even after years of continuous addition of nutrients and electron acceptors [317]. This phenomenon has also been observed for many other xenobiotic and natural substrates under various experimental conditions [327-332]. 

Slurry-phase bioremediation is not effective for treating metals and other inorganic contaminants. This limitation may be overcome by using slurry-phase bioremediation with a physical separation technology, such as soil washing or filtration. Temperature, pH, nutrient status, oxygen potential, and contaminant bioavailability can also be limiting factors in the slurry-phase bioremediation process. 

Storm water runoff from cities and villages presents another problem. This runoff contains salts from road deicing, street refuse, animal waste, food litter, residue from atmospheric deposition of sulfuric and nitric acid, metals, asbestos from automobile brakes, rubber from tires, hydrocarbons from motor vehicle exhaust condensates, oil and grease, soil and inorganic nutrients from construction sites, and a variety of other chemicals. Research shows a heavy impact of urban nonpoint pollution on freshwater quality (World Resources Institute, 1988). 

Agriculture therefore depends on there being a sufficient supply of inorganic nutrients to plants. Cereals, vegetables, fruit-bearing trees or plants, and animal fodder require bioavailable nutrients, that is, nutrients in forms that they can use. Since intensive agriculture depletes many natural nutrients, synthetic nutrients (fertilizers) must be supplied.1-7 In particular, we need to fix the inert N2 of the atmosphere as soluble, reactive compounds such as nitrates, ammonia, and ammonium salts. Other major fertilizer components are sulfate, potassium, and phosphate ions. It may also be necessary to provide trace nutrients, such as cobalt compounds, or to remove excess soil acidity by treatment with lime (CaO). World fertilizer demand in the year 2001 is expected to be about 1.5 x 10s metric tons N, 7.6 x 107 metric tons P2O5, and 6.7 x 107 metric tons K2O these projections represent an... 

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