. "5 What We Eat." Earth Materials and Health: Research Priorities for Earth Science and Public Health. Washington, DC: The National Academies Press, 2007.
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Earth Materials and Health: Research Priorities for Earth Science and Public Health
TABLE 5.1 Trace Element Concentrations (mg kg−1dry weight) in Agricultural Soils and Food Crops
Element
Common Range for Agricultural Soils
Selected Average for Soils
Typical Range for Food Crops
Arsenic (As)
<1−95
5.8
0.009−1.5
Barium
19–2368
500
1–198
Boron
1–467
9.5–85
1.3–16
Cadmium
0.01–2.5
0.06–1.1
0.13–0.28
Cobalt
0.1–70
7.9
8–100
Chromium
1.4–1300
54
0.013–4.2
Copper
1–205
13–24
1–10
Fluorine
10–1360
329
0.2–28.3
Mercury
0.05–0.3
0.03
0.0026–0.086
Molybdenum
0.013–17
1.8
0.07–1.75
Nickel
0.2–450
20
0.3–3.8
Lead
3–189
32
0.05–3.0
Selenium
0.005–3.5
0.33
0.001–18
Silver
0.03–0.9
0.05
0.03–2.9
Tin
1–11
—
0.2–7.9
Vanadium
18–115
58
0.5–280
Zinc
17–125
64
1.2–73
SOURCE: Alloway (2005).
age sludge and fertilizers and atmospheric deposition from industrial sources. Because of differences in the mineralogy of the parent materials and the variable levels and broad range of contamination from anthropogenic sources, soils are found with a wide range of trace metal concentrations. Trace element concentrations in agricultural soils can vary by two to three orders of magnitude (see Table 5.1).
Chaney (1983) classified trace elements in agricultural soils that received sewage sludge and other wastes according to their potential for risk. At a soil pH of 6-8, the low solubilities or strong adsorptions of silver (Ag), gold (Au), chromium (Cr), fluorine (F), galium (Ga), mercury (Hg), lead (Pb), palladium (Pd), platinum (Pt), silicon (Si), tin (Sn), titanium (Ti), and zirconium (Zr) essentially preclude significantly increased concentrations in plants even when the soils are greatly enriched in these elements. Increased concentrations of aluminum (Al), arsenic (As), boron (B), barium (Ba), beryllium (Be), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), vanadium (V), and zinc (Zn) in plants are insufficient to adversely affect animals because the element causes phytotoxicity, the element is well tolerated by animals, and/or the maximum increased level in plants is lower than the toxic level to animals. Elements that are easily
