passive, adsorbent-based sediment pore water...

© Copyright 2013 AMPLIFIED GEOCHEMICAL IMAGING, LLC www.agisurveys.net Slide 1

Passive, Adsorbent-Based Sediment Pore Water

Sampling

2013 NEMC

August 5, 2013 Jim Whetzel

Amplified Geochemical Imaging, LLC. (AGI)

Special thanks to Kathy West, URS Corporation

Ken Alepidis and Sean Caroll, Haley & Aldrich, Inc.


• Common applications of passive sampling

• Sampler description and analysis

• Calculating concentrations

• Installation guidelines

• Case studies

– Canal sediment – direct insertion

– River sediment - test cell

• Conclusions

Overview


• Site assessment – Rapid, high-resolution

– Shifts sampling from exploration to confirmation

– Focuses more intrusive expensive sampling

• Brownfields – property transfers

• Vapor intrusion

• Monitoring – Groundwater long-term

– Site remediation

• Water sampling – Ground & surface water, sediment pore water

Common Applications


• GORE-TEX® Membrane

– Inert, waterproof, vapor permeable

– Designed for vapor diffusion

• Hydrophobic, engineered sorbents

– VOCs, SVOCs, PAHs

• Sample integrity protected

• 4,000 surveys worldwide – Federal, state, international regulatory acceptance

AGI Universal Sampler (formerly GORE® Module and GORE-SORBER)

GORE-TEX® Membrane


Vapor Transfer Rates


Analysis

• TD\GC\MS (Modified EPA 8260C) – Duplicate samples

– Screening level and accredited methods available

• Results available in mass and concentration

Testing CERT #3062.01


Installation in Sediment

Courtesy of Peregrine Ventures

Sampler can

be inserted

directly into

sediment

Courtesy Marion Environmental

Courtesy URS Corporation


Sampler Exposure Times

Expected Concentration of Primary Contaminant

(ppb)

Residence Time in Sediment (Hr)

20 to 5000 0.5

10 to 3500 1

5 to 2000 2

3 to 1000 4


Mass (ug) to Pore Water Conc. (ppb)

Simplified equation for water - Single conc., time, temp

Conc (ug/L) = mass(ug)/time(Hr)/SR(L/Hr)

Model vs Actual Concentration

Toluene

y = 1.0855x

R2 = 0.9738

1

10

100

1000

10000

1 10 100 1000 10000

Dosed Concentration (ug/L)

Mo

del

Co

ncen

trati

on

(ug

/L)

Multiple times, temps, and sorbed mass Conc = (mass)b /(time)-d /[-SRo x exp(-Ea/R(1/Tr - 1/T))]

Regression output from ln(conc) versus ln(mass), ln(time), 1/temp b & d = exponents accounting for non-linear response -Ea/R = correction for deviation from ref. temp SRo = Sampling rate Other inputs T = water temp (K), Tr = reference water temp (K)


Mass (ug) to Pore Water Conc. (ppb)

http://toxics.usgs.gov/definitions/pore_water.html,

June 20, 2013

Equation for Sediment Concpw = Concw / fpw

Concpw = pore water concentration Concw = water concentration fpw = fraction pore water

http://toxics.usgs.gov/definitions/pore_water.html


Sediment Sampling Studies

• Direct insertion of sampler – Canal Sediment

– Aromatic chlorinated benzenes

• Test cell to separate solid material from pore water

– River sediment

– BTEX & PAHs

Courtesy of Haley & Aldrich

Courtesy of URS Corp


Direct Insertion into Sediment

Background

• Former dye manufacturer

• Contaminated GW discharging into canal water and sediment

Goal: Find a rapid deployment assessment tool for monitoring natural attenuation

• Sheet pile barrier (SPB) installed to eliminate source

• GW below and down stream treated by interceptor well

• Selected MNA for remediation of sediment


• Focus on 2 sampling locations: B, C

- Field Duplicates BB, CC

• PPWS placed above sediment and

every 3 to 4 inches - Quick & Simple installation

- 5 to 60min exposure

• Comparison with Peepers

- Exposure over several days to weeks

- Sampling not done concurrently

Canal Sediment Sampling

PPWS = passive pore water sampler (AGI Sampler)


Peepers (permeable sampler)

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•Semi-permeable membrane covered cells filled with organic solvent or water

•Hydrophobic compounds diffuse from pore water across the membrane into the solvent

http://www.epa.gov/greatlakes/sediment/iscmain/five.html

~ 1

mete

r


Unconsolidated silt “fluffy” to gravelly sand

• Temperature probe for sediment temp.

• Decagon EC5 moisture meter for vol. water content


Typical Sediment Profile



0 2000 4000 6000 8000 10000 12000 14000

Pore Water Concentration, ug/L

-38

-34

-30

-26

-22

-18

-14

-10

-6

-2

2

De

pth

fro

m S

ed

ime

nt

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ce

, in

ch

es

Location B - Chlorobenzene by Depth

PEEPER

PPWS

• Peeper indicates concentration relatively stable -2” to -18”

• PPWS indicates concentration increases significantly with depth



0 2000 4000 6000 8000 10000 12000 14000


2

-34

-26

-18

-10

-2

De

pth

fro

m S

ed

ime

nt

Su

rfa

ce

, in

ch

es

Locations B & BB - Chlorobenzene by Depth

PPWS -

B

PPWS -

BB

•PPWS field duplicate shows somewhat similar increasing concentration pattern with sediment depth



• Peeper indicates concentration in water (2”) is similar to concentration in shallow sediment

• PPWS indicates concentration increases from water to sediment and levels out after ~6” depth

0 2000 4000 6000 8000 10000 12000


-34

-26

-18

-10

-2

6

De

pth

fro

m S

ed

ime

nt

Su

rfa

ce

, in

ch

es

Location C - Chlorobenzene by Depth

PEEPER

PPWS



•PPWS field duplicate shows similar concentration pattern

0 1000 2000 3000 4000 5000 6000 7000


2

-34

-26

-18

-10

-2

Dep

th f

rom

Sed

imen

t

Su

rface, in

ch

es

Locations C & CC - Chlorobenzene by Depth

PPWS -

C

PPWS -

CC


Study Observations

• Quick and simple sampling

• Comparison to Peepers

– Lower overall cost

– Somewhat similar values at higher concentrations

– PPWS shows greater variation in pore water concentrations

• Sediment profile consistent between PPWS field dups



Test Cell Sampling Background

• Former MGP site

• COCs detected in river sediments – VOCs and PAHs

• GW and soil remediation addressing source completed

• Sediment remediation planned

- Excavation and permeable cap placement

• Pilot scale reactive cap test cell constructed

• Problem: Micro-wells tend to clog due to matrix

Goals: 1. Design sampling system that won’t clog during testing/

monitoring

2. Sampling must be able to demonstrate efficacy of capping • results must be similar to Micro-well at target

concentrations


Test Cell Sampling

Evaluation of Test Cell Sampling Design • Sampling ports for Passive Pore Water Sampling (PPWS – AGI Sampler)

• Micro-wells for low flow water sampling

12” Screened Port

1” PVC


Test Cell Sampling

PPWS Ports

Pilot-Scale Reactive Cap and Test Cell Micro-wells

River Water

Sand Organoclay® mixture

Reactive Core Mat (RCM)

Sand 12”

~2cm

12”

Sediment

Sand Layer

•Approximate Placement of Sampling Ports

•PPWS inserted into tubing down to end sampling port


Test Cell Sampling

PPWS v. Low Flow

•PPWS MDL > Low Flow MDL

•Excellent agreement at higher concentrations

•Met study goals


Test Cell Sampling

Test Conclusion:

•Passive Pore Water Sampling Design capable of being used to sample pore water in test cell

•PPWS able to show differences in test cell zones

•Analytical results compare well at target

concentrations

-Comparison suitable for project DQOs

-Lower concentrations differ due to differences in MDLs

-PPWS Analysis MDL> Water method MDL


• Flexible applications

• Acceptable agreement with Peepers and Micro-well data

• Quick, simple, accurate, and cost effective solution

• Passive Pore Water Sampling attractive alternative to other sediment pore-water techniques

Conclusions

passive, adsorbent-based sediment pore water...

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