Passive Membrane Samplers:

Transcription

1 Passive Membrane Samplers: An effective and cost-saving method to assess low level PAH water contamination Ekati Diamond Mine Stephanie Nabess M.Sc. R.P.Bio. (Stantec) Heather Lord Ph.D. (Maxxam Analytics) BEST Conference Whistler, BC May 21,

2 Agenda 1 Project Overview 2 Sampling Program 3 Passive Sampler Design 4 Laboratory Results 5 Project Results Source: Dominion Diamond Corp. (

3 Project Overview - Background Diamond Mine in NWT in operation since 1992 Pits and mine operations located within an area of interconnected lakes High value fish species including Lake Trout and Arctic Grayling Extensive aquatic effects monitoring program Source:

4 Project Overview - Problem Recent studies detected: low levels of dioxins and furans in lake bed sediments undetermined hydrocarbons in fish tissue No obvious source of hydrocarbons at mine site.

5 Project Overview Limitations Short sampling season (3 months open water) Inability to conduct large scale lethal sampling Multiple potential source locations Variable physical conditions between sites 5

6 Sampling Program - Components Passive water samplers Sediment Snow Air emissions All samples were analyzed for a minimum of 18 individual PAHs

7 Sampling Sites Sediment, Snow, Air Emissions Passive Samplers

8 Sampling Sites Image Source: Wikipedia Kodiak Tailings Pond Cell B Waste Rock Seep-348 KL LM Leslie Little SLDG Slipper Moose Nanuq NQ (reference site)

9 Passive Samplers Passive sampling overview Sampler design and fabrication Sample processing Water concentration calculation

10 Introduction to Passive Sampling Red line is the passive sampler concentration Water concentration is estimated from the passive sampler concentration based on the compound specific partition coefficient K SW Only valid once equilibrium is reached! uptake phase equilibrium phase Reference: EPA - Office of Research and Development, and Office of Superfund Remediation &Technology Innovation, OSWER Directive FS Before equilibrium, sampling rate must also be measured and included Deuterated PAHs (PRCs) loaded into samplers prior to deployment to monitor sampling rate Rate of PRC loss allows us to calculate uptake rate of water contaminants

11 Alkylated PAHs naphthalene = C0 CH 3 2-methylnaphthalene = C1 CH 3 2-ethylnaphthalene = C2 CH 3 CH 3 2-ethyl-3-methylnaphthalene = C3 Straight chain hydrocarbons attached at various points on rings

12 OIL Alkyl SANDS PAHs in Crude MONITORING Oil PROGRAM Dissolved Alkyl PAHs in Water 12

13 LDPE Passive Sampling Overview LDPE: low density polyethylene Used for surface water, groundwater or sediment pore water monitoring LDPE films placed into the water body, contaminants slowly move into the film from the water over time 30 days LDPE extracts only non-polar contaminants: eg. PAHs, PCBs, DDX, Dioxins/Furans After deployment the films are extracted in solvent analysed by GC/MS Modeling was used to predict appropriate film size and thickness Films used in this project: High quality flat sheet films normally used in food and pharmaceutical packaging Lohmann, R Envir. Sci. Technol., 46,

14 Pre-field Sampler Modelling Film Thickness: 1 mil 1 cm/s, 150 cm 2, 10 C Film Thickness: 6 mil 1 cm/s, 150 cm 2, 10 C 1.4 ng/l 1.4 ng/l Models allow for film thickness, area, water flow, deployment time and deployment temperature to be varied, to determine impact on detection limit (DL) and equilibration time.

15 Effect of Water Flow Water Flow: 0.1 cm/s 2 mil film, 15 cm dia, 10 C Water Flow: 10 cm/s 2 mil film, 15 cm dia, 10 C 0.4 ng/l

16 LDPE Set-up Deployment Three LDPE circles, 15 cm diameter, 1.4, 3, 8 mil thick Screening protects films from damage and keeps films flat Support bars and fastening clips for anchoring Deployed 3 x 1 month: June, July, August Lab Solvent extract, GC/MS Parent PAH reported for all films Alkyl PAH reported for selected films

17 Laboratory Results Detection Limits Parent PAH Alkyl PAH Weathering 17

18 Detection Limit Comparison (ng/l) Passive Sampler (Kodiak-Little June) Parameter Water Sample 1.4 mil 3 mil 8 mil Acenaphthylene Quinoline Naphthalene Acenaphthene Fluorene Phenanthrene Anthracene Acridine Fluoranthene Pyrene Benzo[a]anthracene Chrysene Benzo(b/J)fluoranthene Benzo(k)fluoranthene Benzo(e)pyrene Benzo(a)pyrene Benzo(g,h,i)perylene

19 Parent PAH Results Air, snow and sediment results around power station and incinerators not similar to stream results Cell B PAHs were consistent between water and sediment Source of naphthalene and biphenyl at NQ and SLDQ unknown

20 Alkyl PAH Results Consistency in PAHs present and PAH patterns between sites suggests a similar source Cell B has a generally petrogenic signature Seep, KL, and LM have similar patterns to Cell B, possibly with more degradation More degradation Less degradation 20

21 Alkylated PAH Ratio Plots Dbt/Phe ratio plots indicate source similarities: Cell B has a range of sources Seep 348 and KL (June) are similar LM and KL (July/August) are similar Cry/Dbt ratio plots indicate weathering: Higher ratios = more weathering Cell B PAHs more weathered in June By August weathering is similar to KL

22 Project Conclusions PAH concentrations are low, well below CCME guidelines Incinerator not the primary source of PAHs PAH compositions from Cell B, Seep, KL, LM and Haul Road sediments appear to share a similar petrogenic source Source is likely related to the use of DL-10 dust suppressant

23 Project Results - Successes Lower detection limits compared to existing water sampling Three film thicknesses = robust data Lower field and laboratory costs Multiple matrices useful Alkyl analysis was key 23

24 Project Results Lessons Water flow and biofilm affected results Use back-ups and duplicates! Water is a powerful force. Analyze a wide range of PAHs to enable use of more ratios Use of many sites allows development of a whole site picture

25 Overall Conclusions Reduced field time Simple to deploy Increase viable sampling sites Reduce lethal sampling Reduced detection limits

26 Acknowledgements: Dominion Diamond Ekati Corporation ERM Rescan (Logistical Support) Royal Roads University Contact Info Stephanie Nabess Biologist Stantec Heather Lord Manager, Environmental R&D Maxxam Questions?