Passive, Adsorbent-Based Sediment Pore Water Sampling

Transcription

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. Slide 1

2 Overview Common applications of passive sampling Sampler description and analysis Calculating concentrations Installation guidelines Case studies Canal sediment direct insertion River sediment - test cell Conclusions Slide 2

3 Common Applications 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 Slide 3

4 AGI Universal Sampler (formerly GORE Module and GORE-SORBER) GORE-TEX Membrane Inert, waterproof, vapor permeable Designed for vapor diffusion Hydrophobic, engineered sorbents VOCs, SVOCs, PAHs Sample integrity protected GORE-TEX Membrane 4,000 surveys worldwide Federal, state, international regulatory acceptance Slide 4

5 Vapor Transfer Rates Slide 5

6 Analysis TD\GC\MS (Modified EPA 8260C) Duplicate samples Screening level and accredited methods available Results available in mass and concentration Testing CERT # Slide 6

7 Installation in Sediment Courtesy of Peregrine Ventures Sampler can be inserted directly into sediment Courtesy Marion Environmental Courtesy URS Corporation Slide 7

8 Sampler Exposure Times Expected Concentration of Primary Contaminant (ppb) Residence Time in Sediment (Hr) 20 to to to to Slide 8

9 Model Concentration (ug/l) 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) Multiple times, temps, and sorbed mass Conc = (mass) b /(time) -d /[-SRo x exp(-ea/r(1/tr - 1/T))] Model vs Actual Concentration Toluene y = x R 2 = 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 Dosed Concentration (ug/l) Other inputs T = water temp (K), Tr = reference water temp (K) Slide 9

10 Mass (ug) to Pore Water Conc. (ppb) June 20, 2013 Equation for Sediment Conc pw = Conc w / f pw Conc pw = pore water concentration Conc w = water concentration f pw = fraction pore water Slide 10

11 Sediment Sampling Studies Direct insertion of sampler Canal Sediment Aromatic chlorinated benzenes Courtesy of URS Corp Test cell to separate solid material from pore water River sediment BTEX & PAHs Courtesy of Haley & Aldrich Slide 11

12 Direct Insertion into Sediment Background Former dye manufacturer Contaminated GW discharging into canal water and sediment Sheet pile barrier (SPB) installed to eliminate source GW below and down stream treated by interceptor well Selected MNA for remediation of sediment Goal: Find a rapid deployment assessment tool for monitoring natural attenuation Slide 12

13 Canal Sediment Sampling 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 PPWS = passive pore water sampler (AGI Sampler) Slide 13

14 Peepers (permeable sampler) ~ 1 meter Semi-permeable membrane covered cells filled with organic solvent or water Hydrophobic compounds diffuse from pore water across the membrane into the solvent Slide 14

15 Canal Sediment Sampling Typical Sediment Profile Unconsolidated silt fluffy to gravelly sand Temperature probe for sediment temp. Decagon EC5 moisture meter for vol. water content Slide 15

16 Depth from Sediment Surface, inches Canal Sediment Sampling Location B - Chlorobenzene by Depth PEEPER PPWS Pore Water Concentration, ug/l Peeper indicates concentration relatively stable -2 to -18 PPWS indicates concentration increases significantly with depth Slide 16

17 Depth from Sediment Surface, inches Canal Sediment Sampling Locations B & BB - Chlorobenzene by Depth PPWS - B PPWS - BB Pore Water Concentration, ug/l PPWS field duplicate shows somewhat similar increasing concentration pattern with sediment depth Slide 17

18 Depth from Sediment Surface, inches Canal Sediment Sampling Location C - Chlorobenzene by Depth PEEPER PPWS Pore Water Concentration, ug/l 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 Slide 18

19 Depth from Sediment Surface, inches Canal Sediment Sampling Locations C & CC - Chlorobenzene by Depth PPWS - C PPWS - CC Pore Water Concentration, ug/l PPWS field duplicate shows similar concentration pattern Slide 19

20 Canal Sediment Sampling 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 Slide 20

21 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 Slide 21

22 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 1 PVC 12 Screened Port Slide 22

23 Test Cell Sampling Pilot-Scale Reactive Cap and Test Cell PPWS Ports Micro-wells River Water Sand 12 Reactive Core Mat (RCM) Sand Organoclay mixture ~2cm 12 Sediment Sand Layer Approximate Placement of Sampling Ports PPWS inserted into tubing down to end sampling port Slide 23

24 Test Cell Sampling PPWS v. Low Flow PPWS MDL > Low Flow MDL Excellent agreement at higher concentrations Met study goals Slide 24

25 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 Slide 25

26 Conclusions 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 Slide 26