Inorganic Contaminants of Surface Water

Frontmatter

1. Introduction

Abstract

The process of environmental protection will come under staggering pressure during the 1990s and for the foreseeable future. It took all of human history to develop an economy of $600 billion by the year 1900. Eighty-five years later, the world economy was expanding by more than that amount every 2 years. In the year 2050, the global economy is expected to reach $13 trillion, more than five times what it is today (Speth, 1988). Resource use will expand enormously, as will the production of waste, the formation of chemical by-products, and the deposition of contaminants into surface waters.

Jame W. Moore

2. Aluminum

Abstract

Aluminum is the third most abundant element in the earth’s crust, with an average concentration of approximately 8%. It is chemically reactive, occurring principally as the halide or oxide, usually in complex silicates. Although aluminum is found in essentially all plant and animal species, it is not essential for survival. The environmental significance of aluminum has waxed enormously in recent years for two reasons: (1) increased mobilization due to acidification of surface waters, and (2) potential agent in the genesis of Alzheimer’s and related diseases.

Jame W. Moore

3. Arsenic

Abstract

Arsenic, a rare but ubiquitous element, cycles rapidly through water, land, air, and living systems. It occurs in the Earth’s crust at an average concentration of 2–5 mg/kg, principally as sulfide and oxide complexes. Arsenic forms a variety of inorganic and organic compounds of different toxicity, reflecting the physicochemical properties of arsenicals of different valency.

Jame W. Moore

4. Asbestos

Abstract

Asbestos is a generic term for a variety of hydrated silicate minerals that have been crystallized to form long, flexible fibers and can in turn be separated into bundles of fibrils. Asbestos is distinguished from non-asbestiform analogs by the presence of easily separated fibers, typically measuring >5 μm in length. There are six common types of asbestiform minerals and an equal number of asbestiform analogs (Table 4.1). Chrysotil is generally the most common form found in water.

Jame W. Moore

5. Barium

Abstract

Barium is a reactive metal, existing in nature mainly as the mineral barite (barium sulfate), with lesser amounts of witherite (barium carbonate). Although the concentration of barium in the Earth’s crust generally ranges from 300 to 500 mg/kg, certain geologic formations, such as fossil fuel deposits, yield concentrations in excess of 100,000 mg/kg. Barium and calcium are metabolized together in most animal species, and are predominantly deposited in the skeleton.

Jame W. Moore

6. Beryllium

Abstract

Beryllium is found in the Earth’s crust at an average concentration of 2.5 mg/kg, principally in association with silicate minerals rather than sulfides. Approximately 90% of the total crustal beryllium is bound to feldspar and related structures in the form of beryl, bromellite, chrysoberyl, and beryllonite. Although beryllium is absorbed by most plant and animal species, it is not normally metabolized.

Jame W. Moore

7. Boron

Abstract

Boron is a metalloid that occurs in more than 80 minerals, the most common being tourmaline, a complex silicate mineral present in igneous rocks and some sedimentary rocks. Boron in this form is largely inert and is released into the environment at an extremely slow rate through natural weathering processes. However, once released from silicate structures, boron forms highly soluble species that are readily absorbed by most plants and animals.

Jame W. Moore

8. Cadmium

Abstract

Cadmium is the 64th most abundant element, occurring in the earth’s crust at an average concentration of 0.2 mg/kg. Cadmium is classified as a soft acid, preferentially complexing with sulfides, often as greenockite (a hexagonal crystalline form of cadmium sulfide), hawleyite (a cubic crystalline form of cadmium sulfide), sphalerite (zinc sulfide), and otavite (a mineralized form of calcium carbonate). Cadmium is of considerable environmental and health significance because of its increasing mobilization and toxicity to many life forms.

Jame W. Moore

9. Chromium

Abstract

Chromium occurs in the earth’s crust at an average concentration of 100 mg/kg, principally as minerals in the chromite spinel group. These minerals have the generalized formula (Mg,Fe)O(Cr,Al,Fe)₂O₃. Depending on the degree of substitution in the Al, Fe, Cr series, the chromites contain from 13% to 65% Cr₂O₃. Numerous chromium compounds are manufactured from these minerals, most of which contain chromium in the stable 3 + or 6 + state.

Jame W. Moore

10. Cobalt

Abstract

Cobalt occurs in the Earth’s crust at an average concentration of 25 mg/kg, principally as linnaeite (Co₃S₄), carrollite (CuCo₂S₄), safflorite (CoAs₂), skutterudite ((Co,Fe)As₃), and erythrite (Co₃(AsO₄)₂·8H₂O). Although the concentration of cobalt in these minerals can be as high as 200 mg/kg, relatively large residues are also found in coal, uranium ores, some crude oils, and other sulfide ores. Vitamin B₁₂, essential to humans, contains cobalt.

Jame W. Moore

11. Copper

Abstract

Copper occurs in the earth’s crust at an average concentration of approximately 50 mg/kg, principally as a sulfide, both as the simple sulfide and in numerous sulfide minerals. Although the primary copper mineral is chalcopyrite (CuFeS₂), metallic copper, chalcocite (CuS₂), and bornite are also economically important. Copper is essential in many enzymatic reactions in mammals.

Jame W. Moore

12. Cyanides

Abstract

Cyanides are a group of inorganic and organic compounds that contain the cyano (CN) as an integral part of their structure. They exist in numerous forms, many with remarkably different environmental fate and toxicity. Some cyanides are highly reactive and exist only rarely in nature whereas others are moderately persistent and form inorganic complexes with metals.

Jame W. Moore

13. Iron

Abstract

With an average abundance of 5% by weight, iron is the fourth most abundant element in the earth’s crust. The principal ores include magnetite (Fe₃O₄), siderite (FeCO₃), limonite [FeO(OH)], and hematite (Fe₂O₃). Iron is an essential trace element, required by both animals and plants. In some waters it may limit, either directly or indirectly, the growth of algae; it is also essential to oxygen transport in the blood of all vertebrates and some invertebrates. Although iron is of little direct toxicologic significance, it often controls the concentration of other elements, including toxic heavy metals, in surface waters.

Jame W. Moore

14. Lead

Abstract

Lead is the 36th most abundant element in the earth’s crust, with an average concentration of 15 mg/kg. Although found in over 200 minerals, lead is concentrated (30 to 80 g/kg) in galena (PbS), gelesite (PbSO₄), and cerrusite (PbCO₃). The input of anthropogenically derived lead to the environment now outweighs all natural sources, and is likely to remain so for the foreseeable future.

Jame W. Moore

15. Manganese

Abstract

Manganese occurs in the Earth’s crust at an average concentration of 950 mg/kg, principally in ores: pyrolusite (MnO₂), rhodocrosite (MnCO₃), manganite (Mn₂O₃·H₂O), hausmannite (Mn₃O₄), biotite mica (K(Mg,Fe)₃(AlSi₃O₁₀)(OH)₂), and amphibole ((Mg,Fe)₇Si₈O₂₂(OH)₂). Manganese is an essential trace element required by both plants and animals. In some waters it may limit, either directly or indirectly, the growth of algae; it is also an essential component of several enzyme systems in animals. Although manganese is of little direct toxicologic significance, it may control the concentration of other elements, including toxic heavy metals, in surface waters.

Jame W. Moore

16. Mercury

Abstract

Mercury, with an average crustal abundance of 0.08 mg/kg, occurs in sedimentary, igneous, and metamorphic rocks. The most important ore is cinnabar (HgS), but there are at least another 30 common ores and gangue minerals that contain mercury in relatively high concentrations. Mercury, undergoing complex chemical reactions in the environment, forms a number of highly toxic organic derivatives. These compounds have been implicated in the adulteration of aquatic resources in numerous countries.

Jame W. Moore

17. Nickel

Abstract

Nickel ranks as the 23rd most abundant element in the earth’s crust, with an average concentration of 75 mg/kg. Although relatively low concentrations (1 mg/kg) are typically found in sedimentary rocks such as sandstone, much higher levels can be found in basalt (160 mg/kg) and peridotites and durites (2,000 mg/kg). The chief ores of nickel are pentlandite [(Fe,Ni)₉S₈], garnierite [(Ni,Mg)₆(OH)₆(Si₄O₁₁)H₂O], and limonite [(Ni,Fe)O(OH)·nH₂O]. Nickel is also often associated with arsenide ores which, upon mining and smelting, release arsenic into the environment.

Jame W. Moore

18. Nitrogen

Abstract

Nitrogen occurs in the biosphere in oxygenation states ranging from 3- (ammonia) to 5+ (nitrate). The most important inorganic forms of nitrogen are ammonia (NH₃), nitrate (NO₃ ^-), nitrite (NO₂ ^-), and molecular nitrogen (N₂). All of these forms are interrelated in the environment by the nitrogen cycle, a complicated series of transformations (described in Chemistry section). Naturally occurring organic nitrogen compounds occur in surface waters and contain amino and amide nitrogen, and some heterocyclic compounds such as purines and pyrimidines.

Jame W. Moore

19. Selenium

Abstract

Selenium, with an average crustal abundance of 0.1 mg/kg, occurs in most types of rock, but is enriched in shale (approx. 0.6 mg/kg). Geochemically, selenium resembles sulfur, and the two are often found in association with one another. Although unweathered rocks may contain an abundance of metallic selenide, weathering enhances oxidation of that complex. Selenium is present in acidic soils as the selenite ion bound to iron oxide whereas in alkaline soils, it is oxidized to the selenate ion.

Jame W. Moore

20. Silver

Abstract

Silver is a relatively rare element, with an average concentration in the earth’s crust of 0.7 mg/kg. That makes it the 69th most abundant element out of 88 in the crust (Taylor, 1964). Although silver can occur in the elemental form in the environment, several ores also contain silver, including argentite (Ag₂S), cerargyrite (AgCl), pyrargyrite (3Ag₂S·Sb₂S₃), and proustite (3AgS·As₂S₃). Because of its value, silver is recovered to minimize loss in the waste water of most production and user facilities.

Jame W. Moore

21. Sulfur

Abstract

Sulfur has enormous environmental significance because it (1) complexes with many toxic agents, organic materials, and hydrogen in surface waters, and (2) is the primary agent of acidification in many lakes and rivers. Sulfur, with a crustal abundance of approximately 260 mg/kg, is one of the four ore-forming elements (chalcogens) in Group VIA of the periodic chart. Valency states of 2- to 6+ occur in the environment, so sulfur and its complexes are stable over a wide range of conditions. More than 2,000 sulfur-bearing ores have been identified, and some of these, such as bravoite [(Ni,Fe)S₂], chalcopyrite (Cu₂S), cubanite (CuFe₂S₃), greigite (Fe₃S₄), molybdenite (MoS₂) and pyrite (FeS₂), may contain more than 35% by weight of sulfur.

Jame W. Moore

22. Thallium

Abstract

Thallium, with an average crustal abundance of approximately 0.5 mg/kg, occurs in a only a small number of independent minerals. These include lorandite (TlAsS₂), vrbaite (Hg₃Tl₄As₈Sb₂S₂₀), hutchinsonite [Pb, Tl)₂(Cu, Ag)As₅S₁₀], crookesite [Cu, Tl, Ag)₂Se], and avicennite (Tl₂O₃). Thallium is considered a soft acid, so it prefers to complex with sulfur rather than oxides or nitrogen.

Jame W. Moore

23. Tin

Abstract

The environmental significance of tin has risen enormously in recent years owing to the increased use of organic antifouling agents in marine and, to a lesser degree, freshwaters. Numerous environmental impacts, including the elimination or contamination of fish and invertebrates, have been observed in and around marinas and estuaries. Tin occurs in the earth’s crust at an average concentration of approximately 2 mg/kg, and is concentrated in the following commercially important minerals: cassiterite (SnO₂), stannite (Cu₂FeSnS₄), and teallite (PbZnSnS₂). Tin is a borderline metal, meaning that it exhibits equal preference for complexation with sulfur and oxygen/nitrogen.

Jame W. Moore

24. Vanadium

Abstract

Vanadium is a ubiquitous element in the earth’s crust, ranking 22nd in abundance with a mean concentration 150 mg/kg. Although igneous rock, carbonatite complexes, titaniferous magnetite complexes, and deposits of iron, uranium, chromium, and manganese all contain vanadium, high-content ores include vanadinite, descloizite, partonite, roscoelite, and carnotite. Elevated concentrations can also be found in many coals and other fossil fuels. Vanadium is a hard acid, so it prefers to complex with oxides and nitrogen.

Jame W. Moore

25. Zinc

Abstract

Zinc occurs in the earth’s crust at an average concentration of 70 mg/kg, making it the 24th most abundant element. The principal ores are sulfides, such as sphalerite, wurtzite (cubic and hexagonal ZnS, respectively), carbonate (known as smithsonite or calamine, ZnCO₃), and silicate (willemite, Zn₂SiO₄). Although an enormous amount of zinc is mobilized each year from natural and anthropogenic sources, the number of environmental problems caused by zinc has declined during the latter half of this century, reflecting the implementation of sound waste control practices.

Jame W. Moore

26. Summary and Conclusions

Abstract

There is still an enormous amount of work to be done on the environmental fate and toxicity of inorganic contaminants of surface water. Some of the agents evaluated in this book have waned in importance in recent years, whereas others have waxed, reflecting either increased use or mobilization of those agents. In some cases, new toxicological or chemical evidence has come to light, necessitating a reevaluation of the use of the agent.

Jame W. Moore

Backmatter