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Hexavalent
Chromium
Cr0
Cr(CO)6
Chromium (III) oxide
Chromium (III) fluoride
Chromium (III) chloride
Chromium (III) hydroxide
Cr2O3
CrF3
CrCl3
Cr(OH)3
BaCrO4
CrO42Na2Cr2O7
Cr2O72-
+3
Barium chromate
Chromate anion
Sodium dichromate
Dichromate anion
+6
Water Quality Criteria and Guidelines1
0.6
1,245
1,230
1,229
1,200
N2 + 6H2O
Mn2+ + 2H2O
H2O
Cr(OH)2+ + 2H2O
Fe(OH)3 + 3H+ + 3e-
1,057
Fe2+ + 3H2O
CrO4-
0.4
Cr3+
0.2
Cr3(OH)45+
Cr(OH)2+
0
Cr(OH)3
SO42- + 10H+ + 8e-
303
H2S + 4H2O
CO2 + 8H+ + 8e-
169
CH4(g) + 2H2O
-
Chromium (0) (elemental, metal)
Chromium (0) carbonyl
2NO3- + 12H+ + 10eMnO2 + 4H+ + 2eO2 + 4H+ + 4eHCrO4- + 5H+ + 3e-
+
0
HCrO4-
0.8
Cr(OH)2
Formula
Eh (volts)
Compound
Name
Eo (mv)
Oxidation State
Redox Potential
Eh-pH Diagram
1
Cr(OH)4
Natural Chromium Oxidation States
0.2
25o
2
4
6
pH
8
10
Regulatory Limit
(ug/L)
Analysis
Preliminary Health
Goal
Maximum Contaminant
Level
Total Chromium (USEPA)
---
100
Total Chromium (CA)
---
50
Hexavalent Chromium (CA)
0.02
---
Maximum Detected
Concentration (ug/L)
Number of Sources
% of Detections
> 50
7
<1
41 - 50
3
<1
31 - 40
17
<1
21 - 30
63
3
11 - 20
243
11
6 - 10
484
21
1-5
1,493
65
Total
2,310
--
Sources:
1. CDPH. (2011). MCLs, DLRs, and PHGs for Regulated Drinking Water Contaminants.
2. CDPH. (2012). Chromium-6 in Drinking Water Sources: Sampling Results. May 10.
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Email: [email protected]
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Hexavalent Chromium Detections in California
Drinking Water Sources (2000 - 2011)2