Overview of approaches and guidance for monitoring PFOS and related PFASs in water under the GMP

Transcription

1 Overview of approaches and guidance for monitoring PFOS and related PFASs in water under the GMP Derek Muir Environment Canada Aquatic Contaminants Research Division Canada Centre for Inland Waters Burlington ON

2 Outline Water sampling Active sampling Passive vs. active samplers Other media eg sediments Possible locations and sampling design considerations Rivers, lakes, estuaries Timing, frequency Supporting data flow, depth, temperature, WWTP indicators etc Analytical aspects FOSA and other precursors? Filtered vs unfiltered? PFOS in the water column WEOG region Insights/conclusions from results to date

3 Water sample handling and processing Containers (sampling bottles, test tubes, vials etc) should be of high density polyethylene to minimize sorption to the material Freeze or refrigerate samples All equipment should be rinsed with methanol before usage Fortify the samples with a labelled surrogate directly after being sampled Serves to check for any losses due to sample handling Sample container should be rigorously shaken before subsamples are taken out to avoid non-homogenous sample solution Filtration?

4 Filtration? Most studies of PFAS in surface waters have using unfiltered samples Ahrens et al (2009a,b) found that PFOS was entirely in the dissolved phase in the North Sea and 70-85% dissolved in the Elbe River EtFOSE was exclusively found in the particulate phase. Paul et al. (2012) estimated that <20% of the total PFOS entering the Rhine was bound to sediments or suspended particles. Ahrens (2011) has noted that during filtration, PFASs can be adsorbed to the filtration equipment, while the dissolved phase can also adsorb to the filter material and equipment and to the walls of the receiving flask. The filter and equipment may also be a source for blank contamination. Conclusion: not recommended except for samples with high suspended solids Maybe be useful if neutral precursors such as EtFOSE, MeFOSE are analysed

5 Sampling locations monitoring study design (See UNEP/WHO guide) Surface waters from rivers, lakes, estuarine, and marine water to see ongoing distribution Best if coordinated with other programs for water chemistry, limnology and oceanography Homogeneity issues need investigation - vertical stratification, lateral and downstream mixing in rivers Knowledge of potential point sources is critical Lakes lake center or outflow Sample at turnover (temperate regions) Headwater lakes are best Depth profiles useful Rivers and estuaries Upstream and downstream of sources eg. WWTPs extent of mixing should be checked Representative sampling eg cross sectional, flow weighted Frequency - needs to take seasonal flow into account Sediments to follow time trends Dated sediment cores provide best information (lakes) Carefully collected surface sediments depositional areas in rivers, estuaries

6 Active Water Sampling methods Standard approaches for water chemistry and other contaminants eg mercury/methyl mercury 0.5-1L samples Clean hands- dirty hands protocol for bottle handling Hand dipping under the surface Direct pumping into sampling bottles (near surface) Collection of depth profiles from Niskin, Go-Flo, or van Dorn type samplers Ship intakes generally for oceanographic cruises only Avoid PTFE lined samplers eg Niskin, GoFlo etc, bottles, and tubing PTFE and related fluoropolymers could be a source of PFOA and PFNA as well as a sorbent

7 Concentration in water (ng/l) Differences between two detailed studies on the Rhine (Loos et al. 2008; Möller et al. 2010). Used to model PFOS by Paul et al. JEM Möller et al sampled by ship and used mainly ship intake system. Filtered samples Loos et al. sampled at mid stream from a bridge or from shore. Unfiltered samples. Predicted conc n Distance from Lake Constance/ or location

8 Other analytes and ancillary data in rivers and estuaries Include other chemical markers for waste water eg sucralose has been used as a WWTP indicator Flow at nearest gauging station temperature, ph-value, particulate organic carbon (POC), dissolved organic carbon (DOC), total organic carbon (TOC), Suspended particular matter (SPM) salinity

9 Spatial and temporal trends of PFOS in a river basin (Earnshaw et al EI 2014) PFOS 2010 PFOS 2013 River Aire PFOS 2010 PFOS 2013 River Calder

10 Passive Sampler for PFAS in water using modified POCIS with a weak anion exchange sorbent (Kaserzon et al. ES&T 2012) Good agreement between measured concentrations in grab samples and POCIS results Effect pf temperature, ph, and salinity on the magnitude of Ksw also requires further study. Polar Organic Chemical Integrative Sampler

11 Active versus passive sampling? Comparability of results worldwide Achievement of a concentration (ng/l) Integrative sample - highly sensitive to the water flow rate in case of a variable flow regime and to variable emissions in case of point Direct water sampling Passive water sampling sources uptake rate is a difficult parameter + provide an integrative sample less sensitive to short-terim variations in the water/emission regime Costs ~ ~ Required experience - sampling itself doesn t require much experience, but taking a representative sample requires much experience and Required additional data Convenience of sampling/installation Problems of difficult weather conditions/vandalism planning + Sampling site need to be specified, and weather conditions recorded - handling and correct installation of passive samplers requires more experience, but the obtained sample is more representative of the average environmental conditions on site - to calculate uptake rate and state of equilibrium extra measurements need to be performed + - a good fixation/anchorage of passive samplers requires planning/experience + - passive samplers can be lost due to flooding/storms or theft. A protected spot is required.

12 Neutral PFOS precursors in the Elbe Estuary and North Sea (Xie et al. Environ Sci Pollut Res 2013) North Sea Concentration (pg/l) EtFOSE MeFOSE EtFOSA MeFOSA PFOS = 2000 pg/l (Ahrens et al 2009)

13 Concentration in water (ng/l) Distribution of PFOS and FOSA in filtered water samples from the Elbe River, estuary and North Sea (Ahrens et al. Front. Environ. Sci. Engin. China 3, , 2009) PFOS Dissolved PFOS Particulates FOSA Dissolved FOSA Particulates 0 Dissolved Particulates Dissolved Particulates Dissolved Particulates Elbe River N=16 North Sea N=4 Elbe Estuary N=4

14 PFOS and precursors in the Bering Sea (Cai et al. Environ. Sci. Technol. 2012) Are precursors more prominent in remote waters? Station Sampling area Latitude PFOS FOSA MeFOSA EtFOSA MeFOSE EtFOSE A1 western Bering sea < A2 western Bering sea < A3 Bering Strait < C1 western Bering sea < B1 Bering Strait < Method quantification limit

15 Concentration (ng/l) PFOS (ng/l) in river waters in Western Europe, US, and Canada Arithmetic mean concentration and range background sites only i.e. not immediately downstream of WWTPs Includes European Arctic AA- EQS 0.01 Elbe Rhine astern USA & Canada

16 Concentration (ng/l) PFOS in lakes in Western Europe, Arctic, Antarctic, and North America AA- EQS 0.01

17 Concentration (ng/l) PFOS in estuaries and coastal seas: Arctic, Western Europe, North America AA- EQS 0.001

18 Conclusions/discussion points Some excellent study designs are available to guide monitoring programs Limited experience with temporal trends in water Passive vs active sampling Some important decisions needed re filtration/non-filtered and for PFOS precursors

19 Baseline stations Streams Minimum 4 per year, including high- and low-water stages Optimum 24 per year (every second week); weekly for total suspended solids Headwater lakes Minimum 1 per year at turnover; sampling at lake outlet Trend stations Optimum 1 per year at turnover, plus 1 vertical profile at end of stratification Rivers/estuaries Minimum 1 per year for large drainage areas, approximately 100,000 km 2 Maximum 24 per year for small drainage areas, approximately 10,000 km 2 Lakes/reservoirs Minimum 1 per year at turnover Maximum per year at turnover, 1 at maximum thermal stratification