Danny Reible y The University of Texas at Austin Biogeochemistry - - PowerPoint PPT Presentation

Danny Reible y

The University of Texas at Austin

Biogeochemistry beneath the cap

A ti C i P bl d ti b i

Active Capping‐ Permeable adsorptive barrier

Material Options M t f lli t / /NAPL Management of upwelling water /gas/NAPL Effectiveness of materials Placement of materials Placement of materials Capping design‐ modeling

Monitoring Cap Performance

Monitoring Cap Performance

Definition of Cap Objectives

M t l ft ff ti l t i d b ti l

Metals often effectively contained by a conventional cap AVS vs. SEM‐ Capping will enhance reducing conditions

SEM

>

AVS

‐1 10 20 30 40

Salt Zn2+(ppb)

Metals will not be toxic M2+ + FeS(s) → MS(s) + Fe2+

1 2 3 Depth (cm)

SEM

<

AVS

Divalent metals may be

3 4 5 6 Sediment D

3

Divalent metals may be toxic

7 8

Conceptual Model

Pre-Cap Post-Cap

F OOH O2 O2 O2 FeOOH FeOOH FeOOH SO4

2-

Methyl mercury

SO4

2-

Methyl mercury

Mobility and toxicity generally not redox sensitive

D d ti i d iti

Degradation is redox sensitive

Hydrocarbon degradation facilitated aerobically Chl i t d i d ti l d hl i t b t Chlorinated organics reductively dechlorinate but many sediment contaminants refractory

Dynamics controlled by sorption in cap and Dynamics controlled by sorption in cap and

groundwater upwelling

Potentially greater effectiveness than with sand can

be achieved with “active” or amended caps

Encourage fate processes such as sequestration or degradation of contaminants beneath cap Discourage recontamination of cap g p

Feasible if high value components are placed in thin

layer in a controllable manner

Effective if time/capacity of active cap sufficient to Effective if time/capacity of active cap sufficient to

manage finite mass of contaminants

Significant stakeholder acceptance advantage

g p g

Permeability Control

Discourage upwelling through contaminated sediment b di i d fl by diverting groundwater flow

Contaminant Migration Control

Sl t i t i ti t i ll th h Slow contaminant migration, typically through sorption related retardation

Contaminant Degradation Aid Contaminant Degradation Aid

Less well developed, contaminant specific but designed to encourage contaminant fate processes

Clays for permeability control

Demonstrated

Clays for permeability control Activated Carbon or other carbon sequestration agent Organoclays for NAPL control & some dissolved control

Significant swelling and permeability reduction with NAPL Significant swelling and permeability reduction with NAPL

Clay and sequestration agent mixtures Phosphate additives for metals

k h h d d Rock phosphate (i.e. apatite) demonstrated

Iron Sulfide for Hg and MeHg control Siderite (FeCO3) for pH control Zero valent iron Oxygen or hydrogen release compounds/technologies Biopolymers Biopolymers Electrochemical controls on redox conditions

Speculative

C i ll il bl

Commercially available

AquaBlok B t t Bentomat HDPE

C f ll di t d t lli

Can successfully divert groundwater upwelling

Where will the groundwater go? Pl f l i d l Plan for gas accumulation and release Long term effectiveness in the face of gas/tidal dynamics? dynamics?

pH

Siderite

11 12 13

Vlassopoulos and Serrano, 2008

Siderite Ferrous Sulfate Alum

8 9 10

pH

Metals

Apatite

5 6 7

Available FeCO3 ~ 2 g/cm of layer thickness/cm2 2 cm/yr upwelling = 1000 years of pH protection

Iron Sulfide

Organics

.5 1 1.5 2 4 5

FeCO3 reacted (g/L) y p g y p p

Organoclay Activated carbon

NAPL present ‐ Organoclays

Capacity of O(1 g NAPL/g organoclay) Placement within a laminated mat for residual NAPL or to allow replacement if capacity exceeded Placement in bulk for significant NAPL volumes Placement in bulk for significant NAPL volumes Multiple organoclay layers or organoclay/activated carbon layer for both NAPL and dissolved contaminant control

l d l d b

Dissolved contaminants only ‐ Activated carbon

Placement in mat may be necessary to allow easy placement Placement as amendment also possible Placement as amendment also possible Activated carbon typically more subject to fouling than

• rganoclay

1.E+06

• n µg/kg

Hg (PM199)

y = 6920.9x0.7212 R² = 0.9516 1.E+04 1.E+06 Hg Concentratio Hg (PM199) 1.E+00 1.E+02 0.001 0.1 10 1000 Sorbed H Power (Hg (PM199))

Special Hg formulations exist

Hg Water Phase Concentration, µg/L

Spec a g o u a o s e s Conventional formulations may be similarly effective if Hg complexed with suspended

Hg (MRM)

Hg complexed with suspended

• rganic matter

y = 9417.7x0.6709 R² = 0.935 1 E+04 1.E+06 ation µg/kg 1.E+02 1.E+04 ed Hg concentra Hg (meas) Power (Hg (meas)) 1.E+00 0.001 0.1 10 1000 Sorb Hg concentration µg/L

100 mg/g 10 ncentration AC Site 1/10 1 ediment con AC Lab OC Site OC Lab 1/100 2 4 6 8 10 12 Se Water Concentration mg/L

50 60 70 n mg/g 30 40 50

• ncentration

AC Site

10 20 Sediment co

OC Site OC Lab

2 4 6 8 10 12 S Water Concentration mg/L Water Concentration mg/L

– Expect bioavailability reduction proportional to – Expect bioavailability reduction proportional to porewater concentration (inversely proportional to partition coefficient, Kd) – Equivalent sand cap thickness – diffusion/dispersion q p p dominated (u<<1 cm/day)

~

active

d active eff active active

K R L L L R K =

sand

ff sand d

R K

~ 10-4 Koc 0.01Koc focKoc ~ 100Koc Log Kd ~ 1-10Koc

f

16

foc ~ 0.01‐0.05

ACTIVE CAP DESIGN MODEL

To Appear Journal of Soil and Sediment Contamination – Summer 2009

including steady state design model from Lampert and Reible (2009)* Version 3.13 2/9/2008 Instructions: This spreadsheet determines concentrations and fluxes in a sediment cap at steady-state worksheet 1), unsteady state (worksheet 2), assuming advection, diffusion, dispersion, bioturbation, deposition/erosion, sorption onto ll id l i tt d b d l t f A ti l ith h d ti i id d b colloidal organic matter, and boundary layer mass transfer. An active cap layer with enhanced sorption is considered by converting to an equivalent conventional cap thickness. Depth is defined from the cap-water interface. A constant deposition rate can be entered but is not allowed to result in a net contaminant velocity <0 (relative to the changing cap-water interface) . The cells in blue are input cells; these can be changed for the design of interest. DO NOT CHANGE THE CELLS IN RED (or the spreadsheet will not function properly). A second worksheet calculates the transient profiles for a semi-infinite case. The third worksheet title "array" allows the user to create an array of outputs for a given input (e.g. to study different compounds for a given site) Contaminant Properties Contaminant Chlorobenzene Organic carbon partition coefficient, log K oc 2.52 log L/kg Colloidal organic carbon partition coefficient, log K DOC 2.15 log L/kg W t diff i it D 6 0E 06 cm2/s a given site).

0.00 10.00

Transient Concentration Profiles

Cap-Water Interface Bioturbation Layer Bioturbation Layer

Water diffusivity, D w 6.0E-06 cm /s Cap decay rate (porewater basis), λ 1 0.00 yr-1 Bioturbation layer decay rate (porewater basis), λ 2 0.00 yr-1 Sediment/Bioturbation Layer Properties Contaminant pore water concentration, C0 1 ug/L

20.00 30.00 40.00 50.00 Depth, cm

Series13 2 1.21E-11 1.0E+00 2.0E+00 3.0E+00 4.0E+00 5.0E+00 6 0E+00

Effective Cap Layer y Containment Layer

g Biological active zone fraction organic carbon, (f oc ) bio 0.05 Colloidal organic carbon concentration, ρ DOC 10 mg/L Darcy velocity, V 2 cm/yr Depositional velocity, V dep 0 cm/yr Bioturbation layer thickness, h bio 10 cm

60.00 70.00 0.00 0.20 0.40 0.60 0.80 1.00 Dimensionless Concentration

6.0E+00 7.0E+00 8.0E+00 9.0E+00 1.0E+01 Infinity

Underlying Sediment Underlying Sediment

Spreadsheet model

Transient model until penetration of chemical isolation layer Transient model until penetration of chemical isolation layer Steady state model (bioturbation &isolation layer) Variant for additional active cap layer‐ transient and ss p y

Numerical model

Matlab version Matlab version Multiple layers, nonlinear sorption, finite source

Available at http://www caee utexas edu/reiblegroup/ Available at http://www.caee.utexas.edu/reiblegroup/

|Performance Measures

Manag ing Co ntaminatio n

• I

so latio n o f c o ntaminate d se dime nt- Cap stability? E li i ti f di t i C

t bilit ?

Manag ing Co ntaminatio n

• E

liminatio n o f se dime nt re suspe nsio n – Cap stability?

• Re duc tio n in c o ntaminant flux to wate r – F

lux?

• Re duc tio n in c o ntaminant ac c umulatio n in be nthic
• Re duc tio n in c o ntaminant ac c umulatio n in be nthic
• rg anisms- F

lux? Co ntaminant iso latio n? Bio ac c umulatio n?

Thi L C i Thi k L C i Thin Layer Capping Thick Layer Capping vs.

T hin L aye r Cap T hic k L aye r Cap

Percent Sediment and Phen C/C

0versus Depth

15 17 Cap sediment Intermixing Zone 19 21

(cm)

Phenanthrene % Sediment

Clean Sand Cap Cap-sediment Intermixing Zone 23 25

Depth

Sediment 27 29 29 0% 50% 100% 150%

C/C0 and Percent Passing

lk d l f l d f

Bulk sediment concentration is less useful as indicator of

exposure‐risk i b d

Porewater concentration is better indicator

(even for active benthic uptake by ingestion) ff

Porewater is difficult to measure, but possible with solid

phase micro extraction (SPME)

21

Field deployable SPME, capable of measuring porewater with vertical resolution

PAH B(b)F B(k)F B P i M li t

35

PAH Tissue Correlation with Pore Water Concentration (0-7 cm)

35

PAH Tissue Correlation with TOC NormalizedSediment Concentration

PAHs – B(b)F, B(k)F, BaP in Muscalista

R² = 0.8723

10 15 20 25 30

entration (ug/kg)

R² = 0.2703

10 15 20 25 30

entration (ug/kg)

5 10 0.0 1.0 2.0 3.0 4.0

Tissue Conce Pore Water Concentration (ng/L)

5 10 5000 10000 15000 20000 25000 30000

Tissue Conce Sediment Concentration (ng/g)

Single correlation with porewater concentrations works well for all three compounds Single correlation with porewater concentrations works well for all three compounds

|T hin L aye r Capping |

4-c m Sand Cap 4-c m Sand Cap

Day 28 Day 0

|L abo rato ry Studie s o f T hin L aye r Capping

4-c m Sand Cap

Day 28 Day

Capping Performance Capping Performance

B[a]A Pore Water Concentrations

Capping Performance Capping Performance

• 4

Pore Water Concentration (ng/L)

Overlying Water

• 2

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 2 Depth (cm) ACS 0cm 2cm 4cm 4 D 6cm 6 8

25

Thin Layer Capping to Manage Thin Layer Capping to Manage Residuals Residuals Residuals Residuals

Pyrene Concentrations in Worm Tissue Overlying Water

12000 14000 8000 10000 12000

g)

4000 6000

C (ng/

2000

All Contaminated Sediment 0cm 2cm 4cm 6cm 10cm Sediment Depth of Cap

26

9000 7000 8000 9000 4000 5000 6000 /f l (ppb) Phenanthrene Chrysene B(a)A B(b)F 2000 3000 4000 C t / (b) B(k)F B(a)P 1 1.04 1 1000 1000 2000 3000 4000 5000 6000 7000 CpwKow (ppb)

Unit slope is BSF estimated by Kow

27

Conventional sand caps easy to place and effective

Conventional sand caps easy to place and effective

Contain sediment Retard contaminant migration g Physically separate organisms from contamination

There are existing and developing alternatives when a

conventional cap is not sufficiently protective

Permeability Control Adsorptive Caps

Porewater concentrations /profiles can be an effective

t l f d fi i t i t i ti d tool for defining contaminant migration, exposure and risk