Dense Nonaqueous Phase Liquids (DNAPLs)

Chlorinated Aliphatic Hydrocarbons (CAHs)

EPA SW-846: 8260B (laboratory)

Field gas chromatography (GC) or GC/mass spectroscopy (MS)

Regulatory compliance for COCs, the values by which success of the remediation system will be measured.

CAHs and dechlorination products typically are expected to decline to below regulatory compliance levels within the treatment zone after substrate addition.

Baseline and recommended for each groundwater sampling round.

Methane, Ethane, Ethene

EPA SW-846: 5021A

Robert S. Kerr Laboratory RSK-175 SOP followed by GC or GC/MS

Elevated levels of methane indicate fermentation is occurring in a highly anaerobic environment and that reducing conditions are appropriate for anaerobic dechlorination of CAHs. Elevated levels of ethene and ethane (at least an order of magnitude greater than background levels) can be used to infer anaerobic dechlorination of CAHs.

Methane levels >1.0 mg/L are desirable but not required for dechlorination to occur. Methane levels <1.0 mg/L and the accumulation of cis-1,2-DCE, VC, or other CAHs could indicate that additional substrate is required to shift reducing conditions into an environment suitable for reduction of these compounds. If elevated levels of ethene or ethane are not observed, potential accumulation of cis-1,2-DCE or VC should be monitored.

Recommended for each sampling round. Might require analysis by a specialty laboratory.

Total Organic

Carbon/Dissolved Organic Carbon (TOC/DOC)

EPA SW-846: 9060A

APHA et al. 1992: 5310 B, C, or D

Indicator of natural organic carbon present at site during baseline characterization and as an indicator of substrate distribution during performance monitoring. TOC/DOC concentrations >20-50 mg/L are desired in the anaerobic treatment zone.

Stable or declining TOC/DOC levels <20 mg/L in conjunction with elevated levels of VOCs and alternate electron acceptors indicate additional substrate is required to sustain the anaerobic treatment zone.

Baseline and recommended for each sampling event.

Dehalococcoides ethogenes (DHE) or other appropriate microorganism

Quantified by quantitative polymerase chain reaction.- specialist laboratory

Determine presence of DHE or other appropriate microorganism at baseline periods after bioaugmentation.

DHE or other appropriate microorganism will be detected and increase as a consequence of adding electron donor to create anaerobic conditions or increase after inoculation with DHE or other appropriate microorganism-containing culture.

Baseline prior to injection and quarterly based on the numbers achieved. Once a high titer is measured and growth is ensured, the test can be continued but is not critical

Ammonia

APHA et al. 1992: 4500-NH3 C, D, E, F

Ion-selective electrode¹ (ISE) method can be used in the field

Ammonia can represent a form of biologically available nitrogen.

Indicator parameter only.

Baseline.

Nitrate

EPA Method 300.1 or SW-846: 9056A  (laboratory- based ion chromatography methods) 

ISE can be used in the field.

Nitrate is an alternate electron acceptor for microbial respiration in the absence of oxygen. Depleted levels of nitrate (relative to background) indicate that the groundwater environment is sufficiently reducing nitrate.

Indicator parameter. Nitrate level <1.0 mg/L is desirable for anaerobic ISB.

Optional and troubleshooting. Recommended for each sampling event if nitrate reduction appears to be a significant terminal electron accepting process (TEAP).

Nitrite

EPA 300.1 or SW-846: 9056A (laboratory)

In most aquifers the concentration of nitrate is naturally much higher than nitrite, and total nitrate/nitrite can be used as an estimate of nitrate.

Indicator parameter.

Optional and troubleshooting. Alternative method.

Manganese (Mn) 

EPA SW-846: 6010C (laboratory) or Hach Method 8034 (field)

Mn(IV) is an alternate electron acceptor for microbial respiration in the absence of oxygen and nitrate. An increase in dissolved Mn(II) or total manganese indicates that the groundwater environment is sufficiently reducing to sustain Mn reduction and for anaerobic dechlorination to occur.

Elevated levels of dissolved Mn could indicate a competing TEAP to anaerobic dechlorination of CAHs.

Optional. Recommended for each sampling event only if manganese reduction appears to be a significant TEAP.

Major Cations (Ca, Mg, Na, K)

EPA SW-846: 6010C

ISE can be used in the field.

Major cations along with major anions are good general groundwater chemistry parameters and are inexpensive to analyze.

Only as a check if the system is not working as planned.

Baseline and as needed in subsequent sampling events.

Ferrous Iron (Fe[II])

APHA et al. 1992: 3500-Fe D

Colorimetric Hach Method 8146 (field)

Ferric iron is an alternate electron acceptor for microbial respiration in the absence of oxygen and nitrate. Reduction of ferric iron produces ferrous iron. Elevated levels of ferrous iron indicate that the groundwater environment is sufficiently reducing to sustain iron reduction and for anaerobic dechlorination to occur.

Elevated levels of ferrous iron can indicate a competing TEAP to anaerobic dechlorination of CAHs.

Recommended for each sampling round. Typically measured at the well head to protect samples from exposure to oxygen.

Biologically Available Iron

(Fe[III])

Laboratory specialty method (laboratory)

Bioassay with quantification of bioavailable solid-phase ferric iron Fe(III), which is a competing electron acceptor. Optional method that can be used to determine competition from iron reduction. Might also affect potential abiotic reactions.

Recommended only for clastic sediments with potential for significant iron concentrations. Also can be used as a diagnostic tool if sulfate reduction or methanogenic redox conditions cannot be achieved.

Optional at initial sampling.

Sulfate (SO₄)^-2

EPA Method 300.1, SW-846: 9056A (ion chromatography) and SW-846 Methods 9035, 9036, and 9038 (colorimetric and turbidimetric methods) (laboratory)

Hach Method 8051 (field)

Sulfate is an alternate electron acceptor for microbial respiration in the absence of oxygen, nitrate, Mn, and ferric iron. Depleted concentrations of sulfate relative to background indicate that the groundwater environment is sufficiently reducing to sustain sulfate reduction and for anaerobic dechlorination to occur.

Sulfate levels <20 mg/L are desirable but not required for anaerobic dechlorination to occur. High levels of sulfate in conjunction with the absence of TOC/DOC indicate additional substrate might be required to promote anaerobic dechlorination.

Recommend for baseline and each sampling round.

Sulfide

Hach Method 8131 or similar (field colorimetric method)

Field determination of sulfide can also be made by ISE.

By-product of sulfate reduction. Sulfide typically precipitates with iron minerals, but elevated levels of sulfide might be toxic to dechlorinating microorganisms.

Elevated levels of sulfide in conjunction with elevated levels of CAHs can indicate that iron compounds should be added to precipitate sulfides and reduce toxicity effects.

Optional. Recommended when elevated levels of sulfate (>20 mg/L) are present.

Hydrogen Sulfide

Soil gas analyzer calibrated in the field according to the manufacturer's specifications (field)

Useful for determining biological activity in vadose zone and generation of biogenic methane.

Explosive levels of noxious levels of hydrogen sulfide accumulating in structures or utilities can pose a health risk.

Optional. Recommended when soil vapor exposure pathway exists.

Bromide or Iodide

EPA Method 300.1 (laboratory) or ISE (field).

Used as a conservative groundwater tracer.

Indicator parameter for tracer tests.

Used only with tracer testing.

Carbon Dioxide

(CO₂)

APHA et al. 1992: 4500-CO2  C (titrimetric) or 4500-CO2 D (calculation requiring known values for total alkalinity and pH)

ISE for field measurement

Carbon dioxide is a by-product of both aerobic and anaerobic degradation. Elevated levels of carbon dioxide indicate microbial activity has been stimulated.

Indicator parameter.

Optional.

pH

Field probe with direct-reading meter calibrated in the field according to the manufacturer's specifications (APHA et al. 1992: 4500-H⁺ B)

Biological processes are pH sensitive, and the ideal range of pH for dechlorinating bacteria is 5 to 9. Outside this range, biological activity is less likely to occur.

pH levels within a range of 5 to 9 are desirable. pH <5 indicates that a buffering agent might be required to sustain high rates of anaerobic dechlorination. Desorption toward phase equilibrium is the basis of dissolved CAH "rebound," which extends treatment duration.

Baseline and recommended for each sampling event.

Oxidation Reduction Potential (ORP)

Direct-reading meter, A2580B, or USGS A6.5 (field)

ORP of groundwater provides data on whether or not anaerobic conditions are present. Reducing conditions are required for anaerobic dechlorination of CAHs. Used in conjunction with other geochemical parameters to determine whether or not groundwater conditions are optimal for anaerobic biodegradation.

Positive ORP values (>0.0 mV) in conjunction with elevated levels of DO and the absence of TOC/DOC can indicate that additional substrate is required to promote anaerobic dechlorination.

Baseline and typically measured at the well head using a flow-through cell to protect samples from exposure to oxygen.

Dissolved Oxygen (DO)

DO meter calibrated in the field according to the manufacturer's specifications (APHA et al. 1992: 4500-G) (field)

DO should be depleted in an anaerobic bioremediation system. DO <0.5 mg/L generally indicates an anaerobic pathway suitable for anaerobic dechlorination to occur.

DO concentrations >1.0 mg/L in conjunction with elevated levels of CAHs and the absence of TOC/DOC indicate additional substrate might be required to promote anaerobic dechlorination.

Baseline and recommended for each sampling event. Typically measured at the well head using a flow-through cell.

Temperature

Field probe with direct-reading meter (APHA et al. 1992: 2550 B)

General water quality parameter used as a well purging stabilization indicator. Microbial activity is slower at lower temperatures.

Indicator parameter. Typically used as a well purge stabilization parameter.

Baseline and every subsequent sampling

Specific Conductance

EPA 120.1/SW-846: 9050A, direct-reading meter (laboratory or field)

General water quality parameter used as a well purging stabilization indicator. Can correlate with and support interpretations of other geochemical analyses.

Indicator parameter. Typically used as a well purge stabilization parameter.

Baseline and every subsequent sampling event.

Fraction of Organic Carbon (f_oc)

SW-846: 9060A modified for soil matrix (laboratory)

Fraction of organic carbon in the aquifer matrix is used to calculate retardation factors for dissolved contaminant transport and to estimate the amount of contaminant mass sorbed to the aquifer matrix.

A large portion of contaminant mass might be sorbed to the aquifer matrix.

Recommended at baseline sampling.

Volatile Fatty Acids (VFAs)

Laboratory specialty

method, EPA

Robert S. Kerr

Laboratory (RSK)–

SOP 112

VFAs are an indicator of substrate distribution and are also degradation products of more complex substrates (e.g., vegetable oils or carbohydrates). Fermentation of VFAs produces molecular hydrogen for anaerobic dechlorination.

Measurable concentrations of VFAs (>10-20 mg/L) are desirable in the treatment zone. The presence of mg/L concentrations of propionate or butyrate is considered favorable. Absence of measurable VFAs in conjunction with elevated levels of CAHs and alternate electron acceptors indicates additional substrate might be required to sustain the anaerobic treatment zone.

Optional. Useful as a troubleshooting parameter.

Alkalinity

APHA et al. 1992: 2320 B, or Hach alkalinity test kit model AL AP MG-L or Hach Method #8203 (field or laboratory)

ISE for field measurement

Indicator of biodegradation and the buffering capacity of the aquifer (neutralization of weak acids). Used in conjunction with pH. An increase in alkalinity and stable pH indicates the buffering capacity of the aquifer is sufficient to neutralize metabolic acids produced by degradation of substrates. Can also be used as measurement of salinity.

Concentrations of alkalinity that remain at or below background in conjunction with pH <5 indicates that a buffering agent could be required to sustain high rates of anaerobic dechlorination. High salinity conditions can inhibit microbiological activity.

Baseline and recommended for each sampling event.

Dissolved Phosphate

EPA 300.1 or SW-846: 9056A (ion chromatography -laboratory)

Nutrient needed for microbial growth. Might be needed as a substrate amendment

May indicate need for phosphate amendment.

Optional.

Chloride

EPA  Method 300.1 or SW-846: 9056A (laboratory methods),

Hach chloride test kit Model 8-P, or ISE for field measurements

General water quality parameter. Chloride is produced by anaerobic dechlorination of CAHs. Elevated levels of chloride can indicate that dechlorination is occurring if observed concentrations are greater than three times background and consistent with CAH molar concentrations.

Indicator parameter only.

Baseline and every subsequent sampling event.

Contaminants of Concern (COCs)

VOCs, EPA SW-846: 8260B

SVOCs, SW-846: 8270D. Other methods might be more appropriate depending upon the COC (e.g., SW-846: 8310 for PAHs and SW-846: 8330A for Nitro Aromatics).

Field GC or GC/MS might also be appropriate.

Regulatory compliance for COCs, the values by which success of the remediation system will be measured.

Contaminants are typically expected to decline to less than regulatory compliance levels within the contaminant area or in the case of monitored natural attenuation the plume should stabilize or shrink.

Baseline and recommended for each sampling round.

Degradation products, if appropriate (e.g., nitrobenzene produces aniline)

VOCs, EPA SW-846: 8260B

SVOCs, SW-846: 8270D.

Field GC or GC/MS can also be appropriate.

Regulatory compliance when degradation products are also hazardous. Line of evidence that degradation is taking place.

Hazardous degradation products are typically expected to decline to less than regulatory compliance levels within the contaminant area or in the case of monitored natural attenuation the plume should stabilize or shrink.

Baseline and recommended for each sampling round.

Soluble Iron (Suggested by San Mateo County 1996)

Preferred method is to field filter (0.45 µm filter) and ICP 200.7 (measures total of ferric and ferrous iron); alternate field method measuring ferrous iron: Colorimetric Hach Method 8146 (ITRC 2008)

Ferric iron is an alternate electron acceptor for microbial respiration in the absence of oxygen and nitrate. Reduction of ferric iron produces ferrous iron. Elevated levels of ferrous iron indicate that the groundwater environment is sufficiently reducing to sustain iron reduction and for anaerobic degradation to occur—hence conditions are probably not conducive for aerobic degradation.

Indicator of extent of anaerobic degradation. Useful at sites where MNA is chosen (San Mateo County 1996). Not necessary at sites where active aeration is taking place.

Recommended for each sampling round. Typically measured at the well head to protect samples from exposure to oxygen. (ITRC 2008)

Chloride

EPA Method E300.1 or SW-846: 9056A (laboratory methods)

Hach chloride test kit Model 8-P, or ISE for field measurements

General water quality parameter. Chloride is produced by aerobic dechlorination of several chlorinated hydrocarbons (CH) (e.g., chlorobenzene, methylene chloride, vinyl chloride). Elevated levels of chloride can indicate that dechlorination is occurring if observed concentrations are greater than 3 times background and consistent with CH molar concentrations.

Indicator parameter only.

Baseline and every subsequent sampling event.

Nitrate

EPA Method 300.1 or SW-846: 9056A  (laboratory- based ion chromatography methods) 

ISE may be used in field

Nutrient needed for microbial growth. Determines if phosphate needs to be injected into the subsurface and whether it is being consumed or accumulated. (EPA 2004)

May indicate need for phosphate amendment.

Baseline and quarterly thereafter (EPA 2004)

Dissolved Phosphate

EPA Method 300.

EPA SW-846: 9056A  (laboratory)

Nutrient needed for microbial growth. Determines if phosphate needs to be injected into the subsurface and whether it is being consumed or accumulated. (EPA 2004)

May indicate need for phosphate amendment.

Baseline and quarterly thereafter (EPA 2004)

Dissolved Oxygen (DO)

DO meter calibrated in the field according to the manufacturer's specifications (APHA et al. 1992: 4500-O G) (field). Should be done with downhole probe or flow-through cell to avoid atmospheric contact.

If MNA, to determine where aerobic degradation is possible. If active, to determine the success of the oxygen amendment application.

Active injection of an oxygen amendment (air, oxygen, ozone, hydrogen peroxide, Oxygen Release Compound^®) into a source area and somewhat down gradient should re-establish aerobic degradation.

Baseline and quarterly for MNA (Pope 2004)

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

Carbon Dioxide

APHA et al. 1992: 4500-CO2  C (titrimetric) or 4500-CO2 D (calculation requiring known values for total alkalinity and  pH)

ISE for field measurement

Carbon dioxide is a by-product of both aerobic and anaerobic degradation. Elevated levels of carbon dioxide indicate microbial activity has been stimulated.

Indicator parameter.

Optional for active system (ITRC 2008).

For MNA baseline and quarterly thereafter (San Mateo County 1996)

Oxidation Reduction Potential (ORP)

Direct-reading meter, A2580B, or USGS A6.5 (field)

ORP of groundwater provides data on whether or not aerobic conditions are present. Oxidizing conditions are required for aerobic degradation of contaminants. Used in conjunction with other geochemical parameters to determine whether or not groundwater conditions are optimal for aerobic biodegradation.

Positive ORP values (>0.0 mV) in conjunction with elevated levels of DO indicate aerobic conditions and the success of oxidant addition.

Optional for MNA remediation.

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004). Avoid aeration of sample during measurement.

Temperature

Field probe with direct-reading meter (APHA et al. 1992: 2550 B)

General water quality parameter used as a well purging stabilization indicator. Microbial activity is slower at lower temperatures.

Indicator parameter. Typically used as a well purge stabilization parameter.

Optional but generally done as part of well purge stabilization parameter suite.

pH

Field probe with direct-reading meter calibrated in the field according to the manufacturer�s specifications (APHA et al. 1992: 4500-H⁺ B)

Confirms pH conditions are stable and suitable for microbial bioremediation or identifies trends of concern. (EPA 2004)

The optimum pH for bacterial growth is approximately 7,

enhanced aerobic bioremediation can be effective over a pH range of 5 to 9 pH units (EPA 2004).

For MNA: baseline and quarterly thereafter (EPA 2004).

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

Alkalinity

APHA et al. 1992: 2320 B, or Hach alkalinity test kit model AL AP MG-L, or Hach Method #8203 (field or laboratory)

ISE for field measurement

Indicator of biodegradation and aquifer buffering capacity (neutralization of weak acids). Used in conjunction with pH. An increase in alkalinity/stable pH indicate the aquifer's buffering capacity is sufficient to neutralize metabolic acids produced by degradation process (San Mateo County 1996).

Concentrations of alkalinity that remain at or below background in conjunction with pH <5 indicates that a buffering agent may be required (ITRC 2008).

Baseline and all sampling events thereafter (San Mateo County 1996).

Water Table Elevations

Water/air interface meter

Determines direction of groundwater flow and allows for estimate of flow rate.

For MNA groundwater flow direction and rate should fall within the expected range.

Determines if hydraulic conditions (groundwater flow) are consistent with design intent or if enhanced aerobic bioremediation technology application has had an unanticipated effect on these conditions (EPA 2004).

For MNA baseline and all sampling events thereafter (San Mateo County 1996).

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

SOIL VAPOR

Carbon Dioxide

Draeger Tube

Bacharach Fyrite^® Gas Analyzer

Carbon dioxide is a by-product of both anaerobic and aerobic degradation. Elevated levels of carbon dioxide indicate microbial activity has been stimulated.

Indicator parameter.

For MNA at least bi-annually (Pope 2004)

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

Methane

EPA Method 18 (GC)

EPA SW-846: 5021A

Robert S. Kerr Laboratory RSK-175 SOP followed by GC or GC/MS

Provides evidence that biodegradation is occurring

Methane is usually the product of anaerobic biodegradation. High levels will give an indication that biodegradation is proceeding. High levels of methane will also indicate that efforts to aerate the target area may not be succeeding.

For MNA at least biannually (EPA 2004).

Oxygen

Bacharach Fyrite� Gas Analyzer

Oxygen level in soil gas is an indication that aerobic biodegradation is occurring in MNA systems.

Oxygen level indicates the success of oxidant input in active systems.

Reduced oxygen levels are expected during aerobic biodegradation in MNA systems.

Steady state or enriched oxygen levels are one indication that soil conditions are appropriate for aerobic biodegradation

For MNA at least bi-annually (EPA 2004).

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

Volatile COCs

EPA SW-846: 8260B Laboratory

Field GC or GC/MS

Contaminant levels give indication of success of remedial effort.

Suggests residual sources in soil or fugitive emissions associated with the remedial effort

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

SOIL

COCs

VOCs, EPA SW-846: 8260B    SVOCs, SW-846: 8270D

Determine success of remediation.

Soil contaminant concentrations should be dropping over time.

For MNA a statistically significant number of continuous soil cores located throughout the area of contamination (Pope 2004).

For active systems quarterly to annually (EPA 2004).