Oxygen*

<0.5 mg/L

Tolerated, suppresses the reductive pathway at higher concentrations

3

Oxygen*

>5 mg/L

Not tolerated; however, VC may be oxidized aerobically

Nitrate*

< 1 mg/L

At higher concentrations may compete with reductive pathway

2

Iron II*

>1 mg/L

Reductive pathway possible; VC may be oxidized under Fe(III)-reducing conditions

3

Sulfate*

<20 mg/L

At higher concentrations may compete with reductive pathway

2

Sulfide*

>1 mg/L

Reductive pathway possible

3

Methane*

<0.5 mg/L >0.5 mg/L

VC oxidizes Ultimate reductive daughter product, VC Accumulates

0
3

Oxidation Reduction Potential* (ORP) against Ag/AgCI electrode

<50 millivolts (mV) <-100 mV

Reductive pathway possible Reductive pathway likely

1
2

pH*

5 < pH < 9 5 > pH > 9

Optimal range for reductive pathway Outside optimal range for reductive pathway

0
-2

TOC

> 20 mg/L

Carbon and energy source; drives dechlorination; can be natural or anthropogenic

2

Temperature*

> 208C

At T>208C biochemical process is accelerated

1

Carbon Dioxide

>2x background

Ultimate oxidative daughter product

1

Alkalinity

>2x background

Results from interaction between CO2 and aquifer minerals

1

Chloride*

>2x background

Daughter product of organic chlorine

2

Hydrogen

>1 nM

Reductive pathway possible, VC may accumulate

3

Hydrogen

<1 nM

VC oxidized

0

Volatile Fatty Acids

>0.1 mg/L

Intermediates resulting from biodegradation of more complex compounds; carbon and energy source

2

BTEX*

>0.1 mg/L

Carbon and energy source; drives dechlorination

2

Tetrachloroethene

Material released

0

Trichloroethene*

Material released Daughter product of PCE

0
2^a/

DCE*

Materiel released Daughter product of TCE If cis is > 80% of total DCE it is likely a daughter product 1.1-DCE can be chemical reaction product of TCA

0
2^a/

VC*

Material released Daughter product of DCE

0
2^a)

1,1,1-Trichloroethane

Material released

0

DCA

Daughter product of TCA under reducing conditions

2

Carbon Tetrachloride

Material released

0

Chloroethane*

Daughter product of DCA of VC under reducing conditions

2

Ethene/Ethane

>0.01 mg/L >0.1 mg/L

Daughter product of VC/ethene

2
3

Chloroform

Material released Daughter product of Carbon Tetrachloride

0
2

Dichloromethane

Material released Daughter product of Chloroform

0
2

Score

Interpretation

0 to 5

Inadequate Wevidence for anaerobic biodegradation* of chlorinated organics

6 to 14

Limited evidence for anaerobic biodegradation* of chlorinated organics

15 to 20

Adequate evidence for anaerobic biodegradation* of chlorinated organics

> 20

Strong evidence for anaerobic biodegradation* of chlorinated organics