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1986 | Buch

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Trace Elements in the Terrestrial Environment

verfasst von: D. C. Adriano

Verlag: Springer New York

Enthalten in: Professional Book Archive

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I intend to fill, with this book, a need that has long been felt by students and professionals in many areas of agricultural, biological, natural, and environmental sciences-the need for a comprehensive reference book on many important aspects of trace elements in the "land" environment. This book is different from other books on trace elements (also commonly referred to as heavy metals) in that each chapter focuses on a particular element, which in tum is discussed in terms of its importance in our economy, its natural occurrence, its fate and behavior in the soil-plant system, its requirement by and detriment to plants, its health limits in drinking water and food, and its origin in the environment. Because of long distance transport to pristine areas of cadmium, lead, copper, and zinc in relatively large quantities, these elements have an extra section on natural ecosystems. A blend of pictorial and tabular data are provided to enhance understanding of the relevant information being conveyed. Since individual chapters are independent of one another, they are arranged alphabetically. However, readers with weak backgrounds in soil science are advised to start with the chapter on zinc, since soil terminology is discussed in more detail here. Sections on sorption, forms and speciation, complexation, and transformations become more technical as soil physical-(bio )chemical phenomena are discussed. The less important "environmental" trace elements are discussed together in the "Other Trace Elements" chapter.

Inhaltsverzeichnis

Frontmatter

1. Introduction

Abstract

The ever-increasing production and demand for some elements in developed and developing countries (see Appendix Table 1.1)* suggest the mounting probability of their dispersal and contact with the environment. An element may be dispersed from the time its ore is being mined to the time it becomes usable as a finished product or ingredient of a product. In addition, increasing demands for fertilizers in high-production agriculture may enhance this probability. Land disposal techniques that seem promising for agricultural wastes and other solid wastes may also increase the metal burden of the soil. Trace element research has been intense during the last three or so decades, highlighted by exploration into Itaiitai disease and Minamata disease in Japan. At stake are the integrity and quality of land resources in the United States: 182.1 × 10⁶ hectares (ha) of cropland, 404.7 × 10⁶ ha of forest and range, and 202.4 × 10⁶ ha of nonagricultural land (USDA, 1969). At similar risk are the world’s land resources.

D. C. Adriano

2. Arsenic

Abstract

Arsenic (atomic no. 33) is a steel-gray, brittle, crystalline metalloid with three allotropic forms that are yellow, black, and gray. It tarnishes in air and when heated is rapidly oxidized to arsenous oxide (As₂O₃) with the odor of garlic. It belongs to Group V-A, has an atomic weight of 74.922, and closely resembles phosphorus chemically. Gray As, the ordinary stable form, has a density of 5.73 g/cm³, a melting point of 817°C, and sublimes at 613°C. The more common oxidation states available to As are — III, 0, III, and V. Arsenic compounds compete with their phosphorus analogs for chemical binding sites. Arsenic bonds covalently with most nonmetals and metals and forms stable organic compounds in both its trivalent and pentavalent states. The most important compounds are white As (As₂O₃), the sulfide, Paris Green [3 Cu(AsO₂)₂•Cu(C₂H₃O₂)₂], calcium arsenate, and lead arsenate, the last three being used as agricultural pesticides and poisons.

D. C. Adriano

3. Boron

Abstract

Boron belongs to Group III-A of the periodic table and is the only nonmetal among the plant micronutrients. It has an atomic weight of 10.811, a melting point of 2,300°C, with specific gravity of crystals, 2.34. Boron has two stable isotopes in nature, ¹⁰B (18.98%) and ¹¹B (81.02%). At room temperature, B is inert except to strong oxidizing agents, such as HNO₃. When fused with oxidizing alkaline mixtures, such as NaOH and NaNO₃, it forms borates. The only important oxide is boric oxide (B₂O₃), which is acidic, soluble in water, and forms boric acid B(OH)₃, a very weak acid. In nature, B is fairly rare and occurs primarily as the borates of Ca and Na. Borax (Na₂B₄O₇•10H₂O) is the most common compound, along with boric or boracic acid. By far the most important source of B is the mineral kernite (Na₂B₄O₇•4H₂O), an evaporite deposit found in the Mojave desert of California. It almost always occurs in chemical combination with O₂, as a borate, usually coordinated with three O atoms and occasionally with four. Boron, which has a constant oxidation number of III, never behaves as a cation.

D. C. Adriano

4. Cadmium

Abstract

Cadmium is a soft, ductile, silver-white, electropositive metal, with an atomic weight of 112.40, specific gravity of 8.642, and melting point of 320.9°C. It has eight stable isotopes in nature: ¹⁰⁶Cd, 1.22%; ¹⁰⁸Cd, 0.88%; ¹¹⁰Cd, 12.39%; ¹¹¹Cd, 12.75%; ¹¹²Cd, 24.07%; ¹¹³Cd, 12.26%; ¹¹⁴Cd, 28.86%; and ¹¹⁶Cd, 7.58%. Like Zn and Hg, Cd is a transition metal in Group IIb of the periodic table. Cadmium and Zn, however, differ from Hg in that the latter forms particularly strong Hg-C bonds. Like Zn, Cd is almost always divalent in all stable compounds, and its ion is colorless. Its most common compound is CdS. It forms hydroxides and complex ions with ammonia and cyanide—e.g., Cd(NH₃)₆ ⁴⁻ and Cd(CN)₄ ²⁻. It also forms a variety of complex organic amines, sulfur complexes, and chelates. Cadmium ions form insoluble white compounds, usually hydrated, with carbonates, arsenates, phosphates, oxalates, and ferrocyanides.

D. C. Adriano

5. Chromium

Abstract

Chromium, a member of Group VI-B of the periodic table, has an atomic no. of 24, an atomic weight of 51.996, a specific gravity of 7.18 at 20°C, a melting point of 1,903°C and four stable isotopes with the following percent abundance: ⁵⁰Cr (4.31%); ⁵²Cr (83.76%); ⁵³Cr (9.55%); and ⁵⁴Cr (2.38%). It has five radioactive isotopes, but only ⁵¹Cr, with a halflife of 27.8 days is the most commonly used for tracer studies. Chromium is a steel-gray, lustrous, hard, brittle metal that takes a high polish. It dissolves readily in nonoxidizing mineral acids but not in cold aqua regia or HNO₃. In other words, it is resistant to attack by oxidizing acids and a range of other chemicals, hence its use in corrosion-resistant alloys.

D. C. Adriano

6. Copper

Abstract

Copper (atomic no. 29), one of the most important metals to man, is reddish colored, takes on a bright metallic luster, and is malleable, ductile, and a good conductor of heat and electricity (second only to silver in electrical conductivity). It belongs to Group I-B of the periodic table, has an atomic weight of 63.546, a melting point of 1,083°C, and specific gravity of 8.96. It consists of two natural isotopes: ⁶³Cu and ⁶⁵Cu with relative abundances of 69.09% and 30.91%, respectively. The radioactive isotope, ⁶⁴Cu, with a halflife of 12.8 hours, is the most suitable for tracer work.

D. C. Adriano

7. Lead

Abstract

Lead (atomic no. 82) is a bluish-white metal of bright luster, is soft, highly malleable, ductile, and a poor conductor of electricity. It is very resistant to corrosion. It belongs to Group IV-A of the periodic table, has an atomic weight of 207.19, melting point of 327.5°C, boiling point of 1,744°C, and specific gravity of 11.35. It has oxidation states of II or IV. Lead has four stable isotopes, ²⁰⁴Pb(1.48%), ²⁰⁶Pb(23.6%), ²⁰⁷Pb(22.6%), and ²⁰⁸Pb(52.3%). Two radioactive isotopes ²¹⁰Pb (t½ = 22 years) and ²¹²Pb (t½ = 10 hours) are used in tracer experiments. The chloride and bromide salts are slightly soluble (about 1%) in cold water, whereas carbonate and hydroxide salts are almost insoluble.

D. C. Adriano

8. Manganese

Abstract

Manganese (atomic no. 25; atomic wt. 54.938; melting pt. 1,244 ± 3°C, specific gravity 7.21 to 7.22, depending on the allotropic form) is a member of Group VII-A of the periodic table. It is next to Fe in the atomic series, is similar to it in chemical behavior, and is often closely associated with it in its natural occurrence. It can exist in its compounds in the oxidation states of I, II, III, IV, VI, and VII. Its most stable salts are those of oxidation states II, IV, VI, and VII. The lower oxides, MnO and Mn₂O₃, are basic; the higher oxides are acidic. Manganese is a whitish-gray metal, harder than iron but quite brittle. Manganese metal oxidizes superficially in air and rusts in moist air.

D. C. Adriano

9. Mercury

Abstract

Mercury, also called liquid silver, has the atomic number 80, an atomic weight of 200.59, boiling point of 356.6°C, melting point of −38.9°C, specific gravity of 13.55, vapor pressure of 1.22 × 10⁻³ mm at 20°C (2.8 × 10⁻³ mm at 30°C), and solubility in water of 6 × 10⁻⁶ g per 100 ml (25°C). It is a heavy, glistening, silvery-white metal, a rather poor conductor of heat but a fair conductor of electricity. It has seven stable isotopes with the following percent abundances: ¹⁹⁵Hg (0.15); ¹⁹⁸Hg (10.1); ¹⁹⁹Hg (17.0); ²⁰⁰Hg (23.3); ²⁰¹Hg (13.2); ²⁰²Hg (29.6); and ²⁰⁴Hg (6.7). There are many minerals of Hg; the commonest are the sulfides cinnabar and metacinnabar. Mercury is recovered almost entirely from cinnabar (α-HgS, 86.2% Hg); less important sources are livingstonite (HgS•2Sb₂S₃), metacinnabar (β-HgS), and about 25 other Hg-containing minerals. Its unusual high volatility, which increases with increasing temperature, accounts for its presence in the atmosphere in appreciable amounts.

D. C. Adriano

10. Molybdenum

Abstract

Molybdenum (atomic wt. 95.95) is in the second row of the transition metal elements and occurs as five isotopes. It is in Group VI-B with Cr and W and shares some chemical properties with each of these elements. It has a density of 10.2, melting point of 2,620 ± 10°C, and boiling point of 4,800°C. Molybdenum has five possible oxidation states (II, III, IV, V, and VI), but in nature, the IV and VI oxidation states predominate, with the latter being the most stable (Krauskopf, 1972). The most important compound is the trioxide (MoO₃), from which most of the known Mo compounds can be prepared. Molybdenum is resistant to HC1, H₂SO₄, H₃PO₄, and HF solutions under many conditions of concentration and temperature. However, the metal is attacked by oxidizing acids and fused alkalis. It is rapidly oxidized in air at >500°C (Shamberger, 1979). At moderate to high concentrations in solution, molybdate readily polymerizes into polymolybdates with a wide variety of very complex structures. However, in dilute solutions, such as those found in soils or in most natural waters, the predominant form of soluble Mo is the molybdate anion, Mo0 ₄ ²⁻ . Only under unusual conditions of very high enrichment will Mo be found as soluble polymolybdate in waters. In nature the only important ore is molybdenite (MoS₂); however, some powellite and deposits containing wulfenite also occur.

D. C. Adriano

11. Nickel

Abstract

Nickel (atomic no. 28) belongs in Group VIII of the periodic table, the so-called iron-cobalt group of metals, and has an atomic weight of 58.71, specific gravity of 8.902, and melting point of 1,453°C. It is silvery white, takes on a high polish, is hard, malleable, ductile, and a good conductor of heat and electricity. It is insoluble in water, soluble in dilute HNO₃, slightly soluble in HC1 and H₂SO₄, and insoluble in NH₄OH.

D. C. Adriano

12. Selenium

Abstract

Selenium (atomic no. 34) is a member of Group VI, also known as the S family, in the periodic table. It has specific gravities of 4.79 g/cm³ for the metallic (gray) form, or 4.28 g/cm³ for the vitreous (black) form. It has an atomic weight of 78.96, melting point of (gray form) 217°C, and boiling point of (gray form) 684.9 ± 1°C. Because of its chemical similarity to S, it resembles S both in its forms and compounds and accounts for their many interrelations in biology. It has six stable isotopes in nature with the following percentage isotopic composition: ⁷⁴Se, 0.87; ⁷⁶Se, 9.02; ⁷⁷Se, 7.58; ⁷⁸Se, 23.52; ⁸⁰Se, 49.82; and ⁸²Se, 9.19. The most important oxidation states of Se are — II, II, IV, and VI. Selenium can be easily oxidized from Se(0), elemental Se, to Se(IV), (SeO₃ ²⁻), and to Se(VI), (SeO₄ ²⁻). Selenites (SeO₃ ²⁻) are stable in alkaline to mildly acidic conditions and can be found in nature. Some of the known commercial Se compounds are H₂Se, metallic selenides Se(— II), SeO₂, H₂SeO₃, SeF₄, Se₂C1₂, and H₂SeO₄ (selenic acid). Selenium also forms a large number of organic compounds that are analogous to those of S.

D. C. Adriano

13. Zinc

Abstract

Zinc (atomic no. 30) is a bluish-white, relatively soft metal with a density of 7.133 g/cm³. It belongs to Group IIb of the periodic table, has an atomic weight of 65.37, melting point of 419.6°C, and boiling point of 907°C. Zinc is divalent in all its compounds. It is a composite of five stable isotopes: ⁶⁴Zn, ⁶⁶Zn, ⁶⁷Zn, ⁶⁸Zn, and ⁷⁰Zn. Their relative abundances are: 48.89%, 27.81%, 4.11%, 18.56%, and 0.62%, respectively. Six radioactive isotopes have been identified: ⁶²Zn, ⁶³Zn, ⁶⁵Zn, ⁶⁹Zn, ⁷²Zn, and ⁷³Zn with ⁶⁵Zn (t½ = 245 days) and ⁶⁹Zn (t½ = 55 minutes) being the most commonly used.

D. C. Adriano

14. Other Trace Elements

Abstract

The bluish-white, lustrous, very brittle metal (atomic no. 51, atomic wt., 121.75; specific gravity, 6.691; melting pt., 631°C) is found in nature in more than 100 minerals. However, only about one dozen ores are commercially important, such as Sb oxides and sulfides, and complex Cu-, Pb-, and Hg-Sb sulfides, the most important of which is stibnite (Sb₂S₃). In nature, it occurs primarily in the III oxidation state.

D. C. Adriano

Backmatter

Titel: Trace Elements in the Terrestrial Environment
verfasst von: D. C. Adriano
Verlag: Springer New York
Electronic ISBN: 978-1-4757-1907-9
Print ISBN: 978-1-4757-1909-3
DOI: https://doi.org/10.1007/978-1-4757-1907-9

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Inhaltsverzeichnis

Frontmatter

1. Introduction

2. Arsenic

3. Boron

4. Cadmium

5. Chromium

6. Copper

7. Lead

8. Manganese

9. Mercury

10. Molybdenum

11. Nickel

12. Selenium

13. Zinc

14. Other Trace Elements

Backmatter