1. Evaluating Natural Attenuation
Shu-Chi Chang, Ph.D., P.E., P.A.
Assistant Professor1 and Division Chief2
1Department of Environmental Engineering
2Division of Occupational Safety and Health,
Center for Environmental Protection and Occupational Safety and Health
National Chung Hsing University
May 2, 2007

2. Course plan 5/2: Midterm and Evaluating NA
5/9: Evaluating NA and Biobarrier (4 hours)
5/16: Air sparging case study, GW and soil sampling demonstration (4 hours)
5/23: Modeling natural attenuation or guest speaker on NA (1 hour)

3. Course plan 5/30: Modeling natural attenuation 6/6: Case study 1
6/20: Student presentation. Each group will have 30 minutes.
6/27: Final examination

4. Outline Chemical and geochemical data Lines of evidence
Documented loss of contaminant mass of plume stabilization
Analytical data confirming intrinsic bioremediation
Microbiological data
Estimating biodegradation rates
Screening natural attenuation of PHCs
Screening natural attenuation of chlorinated solvents

5. Analytical data
Several broad categories: source term and sorption parameters, contaminants and daughter compounds, electron acceptors, metabolic by-products, and general quality parameters.
The analytes listed in the tables in next few pages are useful for
Estimating the composition and strength of a NAPL source
Showing that natural attenuation is occuring
Evaluating the relative importance of the various natural attenuation mechanism

6. Soil-sediment analytical parameters

7. Data quality objectives

8. GW parameters useful for evaluating natural attenuation (I)

9. GW parameters useful for evaluating natural attenuation (II)

10. GW parameters useful for evaluating natural attenuation (III)

12. GW analytical data quality objectives (II)

13. GW analytical data quality objectives (III)

14. Source term and sorption parameters
Continuing source: mobile or residual NAPL, or contaminant sorbed to the aquifer matrix
Degree of weathering of the NAPL, and its composition and strength-> amount of aqueous phase NAPL
TOC content is important to judge the sorption and possible retardation

15. Contaminant and daughter compounds
Method 8020 can be used if site contamination is limited to petroleum hydrocarbons.
Method SW 8020a is used if only chlorinated solvents of PHCs mixed with solvent are found in the subsurface
The dissolved concentration of combined BTEX and trimethylbenzene should not exceed 30 mg/L for a JP-4 spill or about 135 mg/L for a gasoline spill.

16. Electron acceptors and metabolic by-products
Again, dissolved oxygen (DO), nitrate, Mn(IV), Fe (III), sulfate, and CO2 (for methanogenesis).
Again, observe from the reduced form: Fe(II), Mn(II)
Readily measurable by-products: Fe(II), CO2, H2S, CH4, C2H6, C2H4, alkalinity, lowered redox potential, chloride, and hydrogen.

17. General water quality parameterspH
Temperature: Q10 rule
Conductivity
Those values better to be measured “fresh”

18. General groundwater sampling consideration
Type:
Monitoring wells: most common and versatile but may be biased
Monitoring points
Geoprobe®
Drive by cone penetrometer, hydraulic percussion, manually powered equipment
Grab sampling locations
Hydraulic punch, Geoprobe, cone penetrometer, hand-driven

19. Geoprobe®

20. Cone penetrometer technology (CPT)

21. Groundwater sampling Generic classification Grab: Bailer (most common)
Advantages: can be used at any depth
Disadvantages: aeration and agitation
Suction lift: peristaltic pump
Advantages: no cross contamination, no turbulence (better DO and redox potential measurement)
Disadvantages: limited depth, offgassing
Positive displacement: submersible pump
Advantages: Deep withdraw, high volume
Disadvantages: size limitation, rigorous decontamination

22. Bailer

23. Peristaltic pump

24. Submersible pump

25. Light drilling machine

26. Well-head measurement
Flow-through cell
<5% Height
If bubbles were observed, slow down
If still has bubbles, replace the tubing
Bailer
Slowly immersing into water
Downhole measurement
Care for decon

27. A few tips Sample should be collected directly from the pump
Avoid aeration
No air in the container and sealed well

28. Lines of evidence used to evaluate natural attenuation
Historical trends in contaminant data showing plume stabilization and/or loss of contaminant mass overtime
Analytical data showing
Depletion of electron acceptors and donors
Increasing metabolic by-product
Decreasing parent compounds
Increasing daughtor compounds
Microbiological data that support the occurrence of biodegradation.

31. Documented loss of contaminant mass or plume stabilization
Visual tests of plume stabilization
Statistical tests of plume stabilization
Mann-Whitney U test
Mann-Kendal test

32. Visual tests of plume stabilization

33. Statistical tests of plume stabilization
Mann-Whitney U test

34. Statistical tests of plume stabilization
Mann-Kendall test
Well data
Data comparison
Menn-Kendall statistic

35. Statistical tests of plume stabilization
Mann-Kendal test

36. Analytical data confirming intrinsic bioremediation
Electron acceptors
Daughter compounds
Metabolic by-products
Spatial distribution of e donors, e acceptors, metabolic by-products, and daughter compounds
Deducing the distribution of TEAPs in GW

37. Electron acceptors, by-products, and daughter compoundsDO
Nitrate
Sulfate
By-products
Fe(II) and Mn(II)
H2S
CH4
CO2
Alkalinity
Redox potential
Dissolved hydrogen
Chloride
Daughter compounds

39. Spatial distribution of e donors, e acceptors, metabolic by-products, and daughter compounds

40. Microbiological data

41. Estimating biodegradation rates

42. Screening for NA of PHCs

43. Screening of NA of chlorinated solvents