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negative biological effects may occur, all fall in the nanomolar range of the total recoverable
metal fraction (Table 1). Twelve percent (12%) of all documented water quality impairments in
2002 were attributed to metal contents above the recommended criteria level, indicating that
metal contamination of water resources is a nation-wide problem. While these WQ criteria
guidelines are designed to minimize negative impacts to aquatic ecosystems and water resource
users, they represent derived proxies for metal biogeochemistry and provide no assess-
ment of the contribution of metal speciation to their vital or toxic biological activity.
TABLE 1.
USEPA Recommended Water Quality Criteria (RWQCs) for priority toxic metal pollutants and non-
priority metals. Priority metals are indicated in
bold
. Values represent total dissolved concentrations below which
no significant detriment to aquatic life is predicted. Source: USEPA-8230R-03-010 2003. Values converted to
nanomolar (nM) to facilitate comparison with method detection limits. Assumes 100 mg CaCO
3
/L hardness for
freshwater.
ACT Workshop on Trace Metal Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Freshwater
Saltwater
Element
Symbol
Atomic
Wt
CMC
a
CCC
b
CMC
CCC
Arsenic
As
74.92
4538.2
2002.1
921.0
480.5
Cadmium
Cd
112.40
17.8
2.2
355.9
78.3
Chromium
(VI)
Cr
52.00
307.7
211.5
21153.8
961.5
Copper
Cu
63.55
204.6
141.6
75.5
48.8
Lead
Pb
207.20
313.7
12.1
1013.5
39.1
Mercury
Hg
200.60
7.0
3.8
9.0
4.7
Nickel
Ni
58.69
8008.2
886.0
1260.9
139.7
Selenium
Se
78.96
63.3
3672.7
899.2
Silver
Ag
107.90
29.7
17.6
Zinc
Zn
65.39
1835.1
1835.1
1376.4
1238.7
Aluminum
Al
26.98
27798.4
3224.6
Iron
Fe
55.85
17905.1
Manganese
Mn
54.94
a
CMC
: criteria maximum concentration, acute exposure acceptable limit.
b
CCC
: criterion continuous
concentration - maximum acceptable chronic exposure concentrations.