The use of passive samplers to monitor effectiveness of AC - PowerPoint PPT Presentation

The use of passive samplers to monitor effectiveness of AC amendment to contaminated sediments Amy M.P. Oen, Elisabeth M.L. Janssen, Gerard Cornelissen, Gijs D. Breedveld, Espen Eek and Richard G. Luthy NORDROCS 2012 Oslo, Norway 18-21 September 2012

Traditional methods to determine vertical pore water profiles of HOCs

Field Site at mudflat in San Francisco Bay San Francisco Hunters Point Naval Shipyard South Basin South Basin • Hunters Point site • Activated carbon amendment to sequester PCBs Cho et al. 2009 (ES&T, 43, 3815 – 3823)

Passive samplers and PRCs • Sediment-penetrating sampling rods (40 cm) • Polyoxymethlyene (POM, 17 m m thick) • Polyethylene (PE, 51 m m thick) • Performance reference compounds (PRCs) • Tri (PCB 29) • Tetra (PCB 69) • Penta (PCB 103) • Hexa (PCB 155) • Hepta (PCB 192)

Deployment: August 2008 • pictures • 5 rods POM • 2 rods PE

Retrieval time series • POM: 14, 26, 57, 100 and 154 days • PE: 57 and 154 days

Vertical distribution of AC amendment TOC (%) 0 1 2 3 4 5 6 3 5 Depth (cm) 8 10 13 15

Calculating pore water concentrations • Assuming equilibrium has been achieved Measurement of PCB in passive sampler C  passive _ sampler C pore _ water K passive _ sampler Knowledge of passive sampler-water partition coefficient

PCB uptake in POM over the time series 4 0-2.5 cm, 3 TOC=2.9% Cpom (ng/mg) 13.5-19 cm, 2 TOC=4.5% 30-35.5 cm, 1 TOC=1.9% 0 0 50 100 150 200 Deployment exposure time (days) Measurements indicate equilibrium has been achieved Oen et al. 2011 (ES&T, DOI :10.1021/es200174v)

PRC depletion behavior at t = 154 days PRC reduction in PE (%) PRC reduction in POM (%) 0 50 100 0 50 100 0-2.5 2.5-8 Location of POM (cm from surface) PCB29 8-13.5 PCB 69 PCB 103 13.5-19 PCB 155 PCB 192 19-24.5 24.5-30 30-35.5 35.5-41

PCB uptake in PE over the time series 4 0-2.5 cm, 3 TOC=2.9% Cpe (ng/mg) 13.5-19 cm, 2 TOC=4.5% 30-35.5 cm, 1 TOC=1.9% 0 0 50 100 150 200 Deployment exposure time (days) Measurements support earlier investigations and approach to equilibrium is slow and ongoing Oen et al. 2011 (ES&T, DOI :10.1021/es200174v)

Calculating pore water concentrations • Including depletion of PRCs Measurement of PCB in passive sampler C  passive _ sampler C         pore _ water K 1 exp k t passive _ sampler e Knowledge of passive sampler-water Calculated exchange partition coefficient rate coefficient

Vertical pore water distributions POM - equilibrium PE – PRC depletion POM – PRC depletion Cpw (ng/l) Cpw (ng/l) Cpw (ng/l) (a) (b) (c) 0 4 8 12 0 4 8 12 0 4 8 12 0 0 0 Location of passive sampler (cm from surface) 5 5 5 10 10 10 15 15 15 20 20 20 25 25 25 30 30 30 35 35 35 40 40 40 45 45 45 Variations within a factor of two, reasonable for in-situ measurements

Vertical pore water distributions POM - equilibrium PE – PRC depletion POM – PRC depletion Cpw (ng/l) Cpw (ng/l) Cpw (ng/l) (a) (b) (c) 0 4 8 12 0 4 8 12 0 4 8 12 0 0 0 Location of passive sampler (cm from surface) 5 5 5 10 10 10 15 15 15 20 20 20 25 25 25 30 30 30 35 35 35 40 40 40 45 45 45 Sensitivity analysis for K pom values, ± 0.3 log units

Vertical pore water distributions POM - equilibrium PE – PRC depletion POM – PRC depletion Cpw (ng/l) Cpw (ng/l) Cpw (ng/l) (a) (b) (c) 0 4 8 12 0 4 8 12 0 4 8 12 0 0 0 Location of passive sampler (cm from surface) 5 5 5 10 10 10 2-4 % AC 15 15 15 20 20 20 25 25 25 30 30 30 1 % AC 35 35 35 40 40 40 45 45 45 Deeper layers have traces of AC amendment

AC amendment performance - modelling Hale 2009 (Ph.D. Dissertation, Newcastle University)

AC amendment performance – measurements compared to model Minimally mixed Well mixed In earlier study, measurements in top 15 cm (PE) showed 60% reduction in PCBs 18 months post AC-amendment Tomaszewski and Luthy 2008 (ES&T, 42, 6086 – 6091)

AC amendment performance - measurements compared to model Minimally mixed Well mixed In this study, measurements in top 15 cm (PE) showed 80% reduction in PCBs 30 months post AC-amendment

Conclusions and application • Vertical pore water profiles • good agreement among measurement and calculation methods • variations within a factor of two • In-situ measurement of pore water concentrations • more representative of field conditions • particularly for AC-amended sediments as traditional measurement methods probably underestimate actual pore water concentrations • Passive sampling approach is a robust and promising method for site monitoring and remedial treatment evaluation

Acknowledgements