## 3500 OTHER METALS

The following sections contain background information on, and refer the user to analytical methods for, a diverse group of metals that occur in nature and/or have important industrial uses.



## 3500-Sb Antimony

Antimony (Sb) is the fourth element in Group VA in the periodic table; it has an atomic number of 51, an atomic weight of 121.75, and valences of 3 and 5. The average abundance of Sb in the earth’s crust is 0.2 ppm; in soils it is 1 ppm; in streams it
is 1  g/L, and in groundwaters it is  0.1 mg/L. Antimony is sometimes found native, but more commonly in stibnite (Sb 2S 3 ). It is used in alloys of lead and in batteries, bullets, solder, pyrotechnics, and semiconductors. The common aqueous species are SbO 2, HSbO 2 , and com

plexes with carbonate and sulfate. Soluble salts of antimony are toxic. The U.S. EPA primary drinking water standard MCL is 6



g/L. The electrothermal atomic absorption spectrometric method (3113B) or the inductively coupled plasma/mass spectrometricmethod (3125) are the methods of choice because of their sensitivity. Alternatively use the flame atomic absorption spectrometric method (3111B) or the inductively coupled plasma method (3120) when high sensitivity is not required.



## 3500-Ba Barium

Barium (Ba) is the fifth element in Group IIA in the periodic table; it has an atomic number of 56, an atomic weight of 137.33, and a valence of 2. The average abundance of Ba in the earth’s crust is 390 ppm; in soils it is 63 to 810 ppm; in streams it is 10 mg/L; in U.S. drinking waters it is 49

g/L; and in groundwaters it is 0.05 to 1 mg/L. It is found chiefly in barite (BaSO 4 ) or in witherite (BaCO 3 ). Barium’s main use is in mud slurries used in drilling oil and exploration wells, but it is also used in pigments, rat poisons, pyrotechnics, and in medicine.

The solubility of barium in natural waters is controlled by the solubility of BaSO 4 , and somewhat by its adsorption on hydrox

ides. High concentrations of barium occur in some brines. Concentrations exceeding 1 mg/L constitute a toxicity hazard in the marine environment. The U.S. EPA primary drinking water standard MCL is 1 mg/L.

Perform analyses by the atomic absorption spectrometric methods (3111D or E), the electrothermal atomic absorption method (3113B), or the inductively coupled plasma methods (3120 or 3125).



## 3500-Be Beryllium

Beryllium (Be) is the first element in Group IIA of the periodic table; it has an atomic number of 4, an atomic weight of 9.01, and a valence of 2. The average abundance of Be in the earth’s crust is 2 ppm; in soils it is 0.8 to 1.3 ppm; in streams it is 0.2



g/L, in U.S. drinking waters and in groundwaters it is typically

 0.1  g/L. Beryllium occurs in nature in deposits of beryls ingranitic rocks. Beryllium is used in high-strength alloys of copper and nickel, windows in X-ray tubes, and as a moderator in
nuclear reactors.

Beryllium solubility is controlled in natural waters by the solubility of beryllium hydroxides. The solubility at pH 6.0 is approximately 0.1  g/L. It is nonessential for plants and animals. Acute toxicity occurs at 130  g/L, and chronic toxicity at 5  g/L in freshwater species. The United Nations Food and Agriculture Organization recommended maximum level for irrigation waters
is 100  g/L. The U.S. EPA primary drinking water standard MCL for beryllium is 4  g/L. The atomic absorption spectrometric methods (3111D and E, and 3113B) and the inductively coupled plasma (ICP) methods (3120 and 3125) are the methods of choice. If atomic absorptionor ICP instrumentation is not available, the aluminon colorimetric method detailed in the 19th Edition of Standard Methods may be used. This method has poorer precision and bias than the
methods of choice. Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

1

## 3500-Bi Bismuth

Bismuth (Bi) is the fifth element in Group VA in the periodic table; it has an atomic number of 83, an atomic weight of 208.98, and valences of 3 and 5. The average abundance of Bi in the earth’s crust in 0.08 ppm; in streams it is  0.02 mg/L, and in groundwaters it is  0.1 mg/L. Bismuth occurs in association with lead and silver ores, and occasionally as the native element.

210Bi, 212Bi, and 214Bi are naturally occuring radioisotopes pro

duced in the decay of uranium and thorium. The metal is used in alloys of lead, tin, and cadmium, and in some pharmaceuticals. In natural water, Bi 3  ion will occur, and complex ions with nitrate and chloride also might be expected. The iodide and telluride compounds are toxic by ingestion or inhalation.

Perform analyses by the atomic absorption spectrometric method (3111B) or by the electrothermal atomic absorptionmethod (3113B). The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though bismuth is not specifically listed as an analyte in the method.



## 3500-B Boron

See Section 4500-B.



## 3500-Cd Cadmium

Cadmium (Cd) is the second element in Group IIB of the periodic table; it has an atomic number of 48, an atomic weight of 112.41, and a valence of 2. The average abundance of Cd in the earth’s crust is 0.16 ppm; in soils it is 0.1 to 0.5 ppm; in
streams it is 1  g/L, and in groundwaters it is from 1 to 10  g/L. Cadmium occurs in sulfide minerals that also contain zinc, lead, or copper. The metal is used in electroplating, batteries, paint pigments, and in alloys with various other metals. Cadmium is usually associated with zinc at a ratio of about 1 part cadmium to 500 parts zinc in most rocks and soils.

The solubility of cadmium is controlled in natural waters bycarbonate equilibria. Guidelines for maximum cadmium concentrations in natural water are linked to the hardness or alkalinity of the water (i.e., the softer the water, the lower the permitted level of cadmium). It is nonessential for plants and animals. Cadmium is extremely toxic and accumulates in the kidneys andliver, with prolonged intake at low levels sometimes leading to dysfunction of the kidneys. The United Nations Food andAgriculture Organization recommended maximum level for cadmium in irrigation waters is 10  g/L. The U.S. EPA primary drinking water standard MCL is 10  g/L. The electrothermal atomic absorption spectrometric method (3113B) is preferred. The flame atomic absorption methods (3111B and C) and inductively coupled plasma methods (3120 and 3125) provide acceptable precision and bias, with higher detection limits. Anodic stripping voltammetry (3130B) canachieve superior detection limits, but is susceptible to interferences from copper, silver, gold, and organic compounds. When atomic absorption spectrometric or inductively coupled plasma apparatus is unavailable and the desired precision is not as great,

the dithizone method detailed in the 19th Edition of Standard

Methods is suitable.



## 3500-Cs Cesium

Cesium (Cs) is the sixth element in Group IA of the periodic table; it has an atomic number of 55, an atomic weight of 132.90, and a valence of 1. The average abundance of Cs in the earth’s crust is 2.6 ppm; in soils it is 1 to 5 ppm; in streams it is 0.02 mg/L; and in groundwaters it is generally

 0.1 mg/L. Cesium is found in lepidolite and in the water of certain mineral springs. 137 Cs, with a 33-year half-life, is widely dispersed on the earth’s surface as a result of the radioactive fallout from the atmospheric testing of nuclear weapons. Cesium compounds are used in photoelectric cells, as a catalyst, and in brewing. Some cesium compounds are

fire hazards.

Perform analyses by the flame atomic absorption spectrometric method (3111B). The inductively coupled plasma/mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though cesium is not specifically listed as an analyte in the method. Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al. 3500 OTHER METALS/Cesium

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## 3500-Co Cobalt

Cobalt (Co) is the second element in Group VIII in the periodic table; it has an atomic number of 27, an atomic weight of 58.93, and valences of 1, 2, and 3. The average abundance of Co in the earth’s crust is 29 ppm; in soils it is 1.0 to 14 ppm; in

streams it is 0.2  g/L; and in groundwaters it is 1 to 10  g/L. Cobalt occurs only sparingly in ores, usually as the sulfide or thearsenide. It is widely used in alloys of various steels, in electroplating, in fertilizers, and in porcelain and glass. The solubility of cobalt is controlled by coprecipitation oradsorption by oxides or manganese and iron, by carbonate precipitation, and by the formation of complex ions. Cobalt dust isflammable and is toxic by inhalation. Cobalt is considered essential for algae and some bacteria, nonessential for higher plants, and an essential trace element for animals. The UnitedNations Food and Agriculture Organization recommended maximum level for irrigation waters is 100  g/L.Perform analyses by the flame atomic absorption spectrometric methods (3111B and C), by the electrothermal atomic absorption method (3113B), or by the inductively coupled plasma methods (3120 and 3125).



## 3500-Ga Gallium

Gallium (Ga) is the third element in Group IIIA in the periodic table; it has an atomic number of 31, an atomic weight of 67.72, and valences of 1, 2, and 3. The average abundance of Ga in the earth’s crust is 19 ppm; in soils it is 1.9 to 29 ppm; in streams it
is 0.09  g/L; and in groundwaters it is  0.1 mg/L. Gallium occurs in many zinc ores, and nearly always in bauxite. Gallium compounds are used in semiconducting devices. The element exists as Ga3  in natural water, and its solubility is controlled by formation of the hydroxide. It is considered nonessential for plants and animals.

Perform analyses by the electrothermal atomic absorptionmethod (3113B). The inductively coupled plasma/mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though gallium is not specifically listed as an analyte in the method.



## 3500-Ge Germanium

Germanium (Ge) is the third element in Group IVA in the periodic table; it has an atomic number of 32, an atomic weight of 72.59, and valences of 2 and 4. The average abundance of Ge in the earth’s crust is 1.5 ppm; in streams it is 0.03 to 0.1  g/L; and in groundwaters it is  0.1 mg/L. Germanium is found in germanite, in certain zinc ores, and in elevated levels in certain hot spring waters. Germanium alloys are used in transistors, gold alloys, phosphors, and semiconducting devices. Germanium is present in natural waters in the tetravalent state, and its distribution in natural waters probably is controlled by adsorption on clay mineral surfaces. It is nonessential for plants

and animals.

Perform analyses by the electrothermal atomic absorptionmethod (3113B). The inductively coupled plasma/mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though germanium is not specifically listed as an analyte in the method.



## 3500-Au Gold

Gold (Au) is the third element in Group IB in the periodic table; it has an atomic number of 79, an atomic weight of 196.97, and valences of 1 and 3. The average abundance of Au in the earth’s crust is 0.004 ppm; in streams it is 2  g/L; and in groundwater it is  0.1 mg/L. Gold occurs in the native form, and is associated with quartz or pyrite. The main uses of gold are in jewelry, dentistry, electronics, and the aerospace industry.

Gold solubility is restricted to acidic waters in the presence of oxidizing agents and chloride, or in alkaline solutions in the presence of hydrogen sulfide. Its solubility may be influenced by Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al. 3500 OTHER METALS/Gold

3natural organic acids. Compounds of gold containing thiosulfate and cyanide have some human toxicity.

Perform analyses by the atomic absorption spectrometric method (3111B) or by the electrothermal atomic absorption method (3113B). The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though gold is not specifically listed as an analyte in the method.



## 3500-In Indium

Indium (In) is the fourth element in Group IIIA in the periodic table; it has an atomic number of 49, an atomic weight of 114.82, and valences of 1, 2, and 3. The average abundance of indium in the earth’s crust is 0.19 ppm; in streams it is  0.01  g/L; and in groundwaters it is  0.1 mg/L. Indium often occurs in combination with zinc ores, and sometimes with pyrites and siderite. Indium is used in alloys for bearings, brazing, solder, and in
electrical devices. Indium exists as In 3  and as a number of complex ions. Itssolubility is controlled by the formation of the insoluble hydroxide. The metal and its compounds are toxic by inhalation.

Perform analyses by the electrothermal atomic absorptionmethod (3113B). The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though indium is not specifically listed as an analyte in the method.



## 3500-Ir Iridium

Iridium (Ir) is the eighth element in Group VIII of the periodic table; it has an atomic number of 77, an atomic weight of 192.2, and valences of 1, 3, and 4. The average abundance of Ir in the earth’s crust is probably  0.001 ppm, and in groundwaters it is

 0.1 mg/L. Iridium occurs uncombined with platinum and othermetals. It is used in alloys with platinum in catalysts, thermocouples, electrodes, and wires. The aqueous chemistry is controlled by complex compounds, although the solubility in natural waters is relatively unknown.

Perform analyses by the flame atomic absorption spectrometric method (3111B). The inductively coupled plasma/mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though iridium is not specifically listed as an analyte in the method.



## 3500-Hg Mercury

Mercury (Hg) is the third element in Group IIB in the periodic table; it has an atomic number of 80, an atomic weight of 200.59, and valences of 1 and 2. The average abundance of Hg in the earth’s crust is 0.09 ppm; in soils it is 30 to 160 ppb; in streams
it is 0.07  g/L, and in groundwaters it is 0.5 to 1  g/L. Mercury occurs free in nature, but the chief source is cinnabar (HgS). Mercury is used in amalgams, mirror coatings, vapor lamps,paints, measuring devices (thermometers, barometers, manometers), pharmaceuticals, pesticides, and fungicides. It is often used in paper mills as a mold retardant for paper.

The common aqueous species are Hg 2  , Hg(OH) 20 , Hg 0 , and stable complexes with organic ligands. Inorganic mercury can bemethylated in sediments when sulfides are present to form dimethyl mercury, (CH 3 ) 2Hg, which is very toxic and can concen

trate in the aquatic food chain. Mercury poisoning occurred in Japan in the 1950s as the result of consumption of shellfish that had accumulated mercury. In times past, mercury was used in the haberdashery industry to block hats (the cause of the “mad hatter” syndrome).

Mercury is considered nonessential for plants and animals. The U.S. EPA primary drinking water standard MCL is 2  g/L. The cold-vapor atomic absorption method (3112B) is the method of choice for all samples. The inductively coupled plasma mass spectrometric method (3125) also may be appliedsuccessfully in some cases, even though mercury is not specifically listed as an analyte in the method. The dithizone method
detailed in the 19th edition of Standard Methods can be used for determining high levels of mercury (  2  g/L) in potable waters. Because mercury can be lost readily from samples, preserve them by treating with HNO 3 to reduce the pH to  2 (see Section 1060). Glass storage containers are preferred to plastic, because they can extend the holding time to 30 d, rather than only the 14 d allowed in plastic containers. Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al. 3500 OTHER METALS/Mercury

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## 3500-Mo Molybdenum

Molybdenum (Mo) is the second element in Group VIB in the periodic table; it has an atomic number of 42, and atomic weight of 95.95, and valences of 2, 3, 4, 5, and 6. The average abundance of Mo in the earth’s crust is 1.2 ppm; in soils it is 2.5 ppm; in streams
it is 1  g/L, and in groundwaters it is  0.1 mg/L. Molybdenum occurs naturally as molybdenite (MoS 2) and wulfenite (PbMoO4). It is used in alloys, ink pigments, catalysts, and lubricants. The common aqueous species are HMoO 4 , MoO 4 2

, and organic complexes. It is considered an essential trace element for plants and animals. The United Nations Food and Agriculture Organization recommended maximum level for irrigation waters is 0.01 mg/L.

Use one of the flame atomic absorption spectrometric methods(3111D or E), the electrothermal atomic absorption spectrometric method (3113B), or one of the inductively coupled plasma methods (3120 or 3125).



## 3500-Ni Nickel

Nickel (Ni) is the third element in Group VIII in the periodic table; it has an atomic number of 28, an atomic weight of 58.69, and a common valence of 2 and less commonly 1, 3, or 4. The average abundance of Ni in the earth’s crust is 1.2 ppm; in soils it is 2.5 ppm; in streams it is 1  g/L, and in groundwaters it is

 0.1 mg/L. Nickel is obtained chiefly from pyrrhotite and garnierite. Nickel is used in alloys, magnets, protective coatings, catalysts, and batteries.

The common aqueous species is Ni 2  . In reducing conditions insoluble sulfides can form, while in aerobic conditions nickel complexes with hydroxide, carbonates, and organic ligands can form. It is suspected to be an essential trace element for some plants and animals. The United Nations Food and Agriculture Organization recommended maximum level for irrigation waters

is 200  g/L. The U.S. EPA primary drinking water standard MCL is 0.1 mg/L.

The atomic absorption spectrometric methods (3111B and C), the inductively coupled plasma methods (3120 and 3125), and the electrothermal atomic absorption spectrometric method (3113B) are the methods of choice for all samples.



## 3500-Os Osmium

Osmium (Os) is the seventh element in Group VIII in the periodic table; it has an atomic number of 76, an atomic weight of 190.2, and valences of 3, 4, and 6, and less commonly 1, 2, 5, 7, and 8. The average abundance of Os in the earth’s crust is probably  0.005 ppm, and in groundwaters it is  0.01 mg/L. Osmium occurs in iridosime and in platinum-bearing river sands. Osmium is used as a hardener with iridium and as a catalyst with platinum.

The aqueous chemistry is controlled by complex compounds, although the solubility in natural waters is relatively

unknown.

Analyze by flame atomic absorption methods (3111D and E).



## 3500-Pd Palladium

Palladium (Pd) is the sixth element in Group VIII of the periodic table; it has an atomic number of 46, an atomic weight of 106.42, and valences of 2 and 4. Palladium occurs with platinum in nature. It is used in alloys to make electrical relays, catalysts, in the making f “white gold,” and in protective coatings. Palladium has no known toxic effects. The United Nations Food and Agriculture Organization recommended maximum level for irrigation waters is 5 mg/L.

Preferably analyze by flame atomic absorption method (3111B). The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though palladium is not specifically listed as an analyte in the method. Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al. 3500 OTHER METALS/Palladium

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## 3500-Pt Platinum

Platinum (Pt) is the ninth element in Group VIII of the periodic table; it has an atomic number of 78, an atomic weight of 195.1, and valences of 2 and 4. The average abundance of Pt in the earth’s crust is probably  0.01 ppm, and in groundwaters it is  0.1 mg/L. Platinum is usually found in its native state, but also may be found as sperrylite (PtAs 2). Platinum is used as a catalyst and in laboratory ware, jewelry, and surgical wire. The aqueous chemistry in natural waters is relatively unknown, although its solubility is probably controlled by complex compounds. In powder form, platinum can be flammable, and its soluble salts are toxic by inhalation.

Preferably analyze by flame atomic absorption method (3111B). The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases(with lower detection levels), even though platinum is not specifically listed as an analyte in the method.



## 3500-Re Rhenium

Rhenium (Re) is the third element in Group VIIB in the periodic table; it has an atomic number of 75, an atomic weight of 186.21, and valences of 1 through 7, with 7 being the most stable. The average abundance of Re in the earth’s crust is 7 ppm, and in groundwaters it is  0.1 mg/L. Rhenium is found in columbite, tantalite, and wolframite, as well as in molybdenum ore concentrates. It is used in tungsten-molybdenum-based alloys, thermocouples, filaments, and flash bulbs. Rhenium in the powder form can be flammable.

For analysis methods, see flame atomic absorption methods(3111D and E). The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though rhenium is not specifically listed as an analyte in the method.



## 3500-Rh Rhodium

Rhodium (Rh) is the fifth element in Group VIII in the periodic table; it has an atomic number of 45, an atomic weight of 102.91, and valences of 1 through 6, the most common being 1 and 3. Rhodium is found in its native state in platinum-bearing sands. It is used in platinum alloys for thermocouples, electrical contacts, and jewelry. The aqueous chemistry in natural waters is relatively unknown. The metal is flammable in the powder form, and its salts are toxic by inhalation.

For analysis see flame atomic absorption method (3111B). The inductively coupled plasma/mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though rhodium is not specifically listed as an analyte in the method.



## 3500-Ru Ruthenium

Ruthenium (Ru) is the fourth element in Group VIII in the periodic table; it has an atomic number of 44, an atomic weight of 101.07, and valences of 1 through 7, the most common being 2, 3, and 4. The average abundance of Ru in the earth’s crust is probably  0.01 ppm, and in groundwaters it is  0.1 mg/L. It occurs in its native state in platinum-bearing river sands. It is used in jewelry with platinum, in electrical contacts, and as a catalyst.

The aqueous chemistry in natural waters is relatively unknown. Ruthenium has no known toxic effects.

For analysis see flame atomic absorption method (3111B). The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection levels), even though ruthenium is not specifically listed as an analyte in the method. Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al. 3500 OTHER METALS/Ruthenium

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## 3500-Ag Silver

Silver (Ag) is the second element in Group IB of the periodic table; it has an atomic number of 47, an atomic weight of 107.87, and valences of 1 and 2. The average abundance of Ag in the earth’s crust is 0.08 ppm; in soils it is  0.01 to 0.5 ppm; in
streams it is 0.3  g/L; in U.S. drinking waters it is 0.23  g/L, and in groundwater it is  0.1  g/L. Silver occurs in its native state and in combination with many nonmetallic elements such as argentite (Ag 2S) and horn silver (AgCl). Lead and copper ores also may yield considerable silver. Silver is widely used in photography, silverware, jewelry, mirrors, and batteries. Silver iodide has been used in the seeding of clouds, and silver oxide to
a limited extent is used as a disinfectant for water.

In acidic water Ag  would predominate, and in highchloride water a series of complexes would be expected. Silver is nonessential for plants and animals. Silver can cause argyria, a permanent, blue-gray discoloration of the skin and eyes that imparts a ghostly appearance. Concentrations in the range of 0.4 to 1 mg/L have caused pathological changes in the kidneys, liver, and spleen of rats. Toxic effects on fish in
fresh water have been observed at concentrations as low as 0.17 g/L. For freshwater aquatic life, total recoverable silver should not exceed 1.2 mg/L.

The atomic absorption spectrometric methods (3111B and C) and the inductively coupled plasma methods (3120 and 3125) are preferred. The electrothermal atomization method (3113B) is the most sensitive for determining silver in natural waters. The
dithizone method detailed in the 19th edition of Standard Methods can be used when an atomic absorption spectrometer is unavailable. A method suitable for analysis of silver in industrial or other wastewaters at levels above 1 mg/L is available. 1

If total silver is to be determined, acidify sample with conc nitric acid (HNO 3 ) to pH  2 at time of collection. If sample contains particulate matter and only the “dissolved” metal content is to be determined, filter through a 0.45-  m membrane filter at time of collection. After filtration, acidify filtrate with HNO 3 to pH  2.Complete analysis as soon after collection as possible. Some samples may require special storage and digestion; see Section 3030D.

Reference

1. U.S. ENVIRONMENTAL PROTECTION AGENCY . 1994. Approved Inorganic

Test Procedures. Federal Register 59(20):4504.



## 3500-Te Tellurium

Tellurium (Te) is the fourth element in Group VIA in the periodic table; it has an atomic number of 52, an atomic weight of 127.60, and valences of 2, 4, and 6. The average abundance of Te in the earth’s crust is 0.002 ppm; in soils it is 0.001 to 0.01 ppm; and in groundwaters it is  0.1 mg/L. Tellurium is found in its native state and as the telluride of gold and other metals. It is used in alloys, catalysts, batteries, and as a coloring agent in glass and ceramics. The common aqueous species is TeO 3 2

. The metal and its compounds are toxic by inhalation.

Perform analyses by the electrothermal atomic absorptionmethod (3113B). The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection limits), even though tellurium is not specifically listed as an analyte in the method.



## 3500-Tl Thallium

Thallium (Tl) is the fifth element in Group IIIA in the periodic table; it has an atomic number of 81, an atomic weight of 204.38, and valences of 1 and 3. The averageabundance in the earth’s crust is 0.07 ppm, and in groundwaters it is  0.1 mg/L. The metal occurs chiefly in pyrites.Thallium is used in the production of glasses and rodenticides, in photoelectric applications, and in electrodes for dissolved oxygen meters.

The common aqueous species is Tl  . It is nonessential for plants and animals. Compounds of thallium are toxic on contactwith moisture, and by inhalation. The U.S. EPA primary drinking water standard MCL is 2  g/L. For analysis, use one of the atomic absorption spectrometric methods (3111B or 3113B), or one of the inductively coupled plasma methods (3120 or 3125), depending upon sensitivity requirements. Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al. 3500 OTHER METALS/Thallium

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## 3500-Th Thorium

Thorium (Th) is the first element in the actinium series of the periodic table; it has an atomic number of 90, an atomic weight of 232.04, and a valence of 4. The average abundance in the earth’s crust is 8.1 ppm; in soils it is 13 ppm; in streams it is 0.1



g/L, and in groundwaters it is  0.1 mg/L. Thorium is a radioactive element, with 232Th having a half-life of 1.4  10 10 years. It is widely distributed in the earth, with the principalmineral being monazite. Thorium is used in sun lamps, photoelectric cells, incandescent lighting, and gas mantles. The aqueous chemistry of thorium is controlled by the Th4  ion, which forms a set of complex species with hydroxides.Thorium’s radioactive decay isotopes are dangerous when inhaled or ingested as thorium dust particles.

Either of the flame atomic absorption spectrometric methods (3111D or E) may be used for analysis. The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection limits), even though thorium is not specifically listed as an analyte in the method.



## 3500-Sn Tin

Tin (Sn) is the fourth element in Group IVA in the periodic table; it has an atomic number of 50, an atomic weight of 118.69, and valences of 2 and 4. The average abundance in the earth’s crust is 2.1 ppm; in soils it is 10 ppm; in streams it is 0.1  g/L, and in groundwaters it is  0.1 mg/L. Tin is found mostly in the mineral cassiterite (SnO 2), in association with granitic rocks. Tin is used in reducing agents, solder, bronze, pewter, and coatings
for various metals.

The common aqueous species are Sn 4  , Sn(OH) 4 , SnO(OH) 2 , and SnO(OH) 3 . Tin is adsorbed to suspended solids, sulfides, and hydroxides. Tin can be methylated in sediments. Tributyl tin undergoes biodegradation quickly.Organo-tin compounds are toxic. Tin is considered nonessential for plants and animals.

Either the flame atomic absorption method (3111B) or the electrothermal atomic absorption method (3113B) may be used successfully for analyses, depending upon the sensitivity desired. The inductively coupled plasma/mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection limits), even though tin is not specifically listed as an analyte in the method.



## 3500-Ti Titanium

Titanium (Ti) is the first element in Group IVB in the periodic table; it has an atomic number of 22, an atomic weight of 47.88, and valences of 2, 3, and 4. The average abundance of Ti in the earth’s crust is 0.6%; in soils it is 1700 to 6600 ppm; in streams it is 3  g/L, and in groundwaters it is  0.1 mg/L. The element is commonly associated with iron minerals. Titanium is used in alloys for aircraft, marine, and food-handling equipment. Compounds of the metal are used in pigments and as a reducing agent.

Titanium species are usually insoluble in natural waters, with the
Ti4  species being the most common ion when found. Some com

pounds are toxic by ingestion and the pure metal is flammable.

Either of the flame atomic absorption spectrometric methods (3111D or E) may be used. The inductively coupled plasma mass spectrometric method (3125) also may be applied successfully in most cases (with lower detection limits), even though titanium is not specifically listed as an analyte in the method.



## 3500-U Uranium

Uranium (U) is the third element in the actinide series of the periodic table; it has an atomic number of 92, an atomic weight of 238.04, and valences of 3, 4, and 6. The average abundance of U in the earth’s crust is 2.3 ppm, and in soils it is 1.8 ppm. Concentrations of uranium in drinking waters usually are expressed in terms of picocuries per liter, but that is now being replaced by Becquerel per liter (Bq/L). Theapproximate conversion factor, assuming equilibrium between 234U and 238 U, is 1 g uranium equals 0.67 pCi. The Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al.

Joint Task Group: 20th Edition—See Section 3500-Al. 3500 OTHER METALS/Uranium

8mean concentration of uranium in drinking water is 1.8 pCi/L. The chief ore is uraninite, or pitchblende, uranous uranate [U(UO 4 ) 2 ]. Uranium is known mainly for its use in the nuclear industry, but has also been used in glass, ceramics, and photography.

Uranium compounds are radioactive and are thereby toxicby inhalation and ingestion. There are three natural radioisotopes of uranium. Uranium-238 has a half-life of 4.5 
10 9years, represents 99% of uranium’s natural abundance, and is not fissionable, but can be used to form plutonium-239,
which is fissionable. Uranium-235 has a half-life of 7.1  10 8 years, represents 0.75% of uranium’s natural abundance, is readily fissionable, and was the energy source in the original
atomic bombs. Uranium-234 has a half-life of 2.5  10 5 years and represents only 0.006% of uranium’s natural abundance.

The common forms in natural water are U 4  and UO 2 2  . In natural waters below pH 5, UO 2 2  would dominate; in the pH range of 5 to 10, soluble carbonate complexes predominate. Although there is no U.S. EPA drinking water standard MCL for uranium, an analysis for uranium is required if the gross alpha activity of a water sample is greater than 15 pCi/L.

Perform analyses by the inductively coupled plasma/mass spectrometry method (3125) or by one of the methods in 7500-U (for regulatory compliance purposes). 3500 OTHER METALS/Uranium

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