WATER AND SEDIMENT SAMPLING FOR MEASURING CHEMICAL CONTAMINATION USING PASSIVE METHODS

Transcription

1 WATER AN SEIMENT SAMPLING FOR MEASURING CHEMICAL CONTAMINATION USING PASSIVE METHOS Chris Harman, Ian Allan, Øyvind Garmo, Oddvar Røyset Norwegian Institute for Water Research (NIVA) Gaustadalleen 21, 0349 Oslo 1

2 Outline 1. Introduction to passive sampling 2. Hydrophobic organic contaminants - Correction of exposure specific effects on hydrophobic contaminant uptake by PRCs - Basic field considerations - Blanks 3. Metals 1. GT performance and examples 2. GT sediment sampling 4. Ongoing research, application of techniques to routine monitoring 2

3 Principle of passive sampling A passive sampler can be defined as a human made device where sample collection and residue collection occur simultaneously in a completely passive manner Huckins et al, 2006 The driving force for uptake is diffusion and is directly related to the magnitude of a chemical's equilibrium partition coefficient (sampler-water) Exposure duration is a major factor in the total amount of chemical accumulated Water concentration of target compound also affects the amount of chemical accumulated but not its uptake rate (the volume of water cleared of chemical over a set time 3

4 Passive sampling configurations Applicable to a wide range of contaminants Nonpolar organics (e.g. PAHs, PCBs or PBEs) Polar organics (e.g. pharmaceuticals) Metals (e.g. Cd, Cu, Ni, Pb, Zn) Metalloids (e.g. As) and phosphate Radionuclides Organo-metallics (e.g. TBT, BT or MBT) Thus a wide range of samplers are also available SPMs, LPE, PMS, POM, Chemcatcher POCIS, Chemcatcher GTs, Chemcatcher 4

5 Why passive sample? Representativeness - spot water samples reflect residue composition only at the moment of sampling and may fail to detect or overestimate episodic contamination Passive samplers (PSs) are typically left to accumulate contaminants for periods of several weeks, unlike spot samples Concentration Time weighted etection problems - standard techniques often fail to detect low, but ecologically relevant, levels of contaminants, (e.g.tbt, EQS 0.2 ng L -1 ). average The sampling rate concept (R s L d -1 ) Hydrophobic compounds R s typically 5-10 L d -1, ( L) Relevance of extracted fraction - concentrations of truly dissolved contaminants are not accurately measured by most conventional approaches. e.g. liquid-liquid extraction Only freely dissolved compounds are extracted by PSs Time 5

6 Bioavailable fraction - comparisons with fish 1000 SPM 1000 FISH CF 10 CF Log K ow Log K ow PAH concentration factors in SPMs and fish (as OH metabolites) versus log K ow Uptake is comparable where water is the major exposure pathway, but discrepancy at higher log K ow Harman et al., J. Toxicol. Environ. Health A 6

7 2 Hydrophobic chemical samplers -Semipermeable membrane device (SPM) Lay-flat polyethylene tube 91.4 x 2.5 cm, ~75-90 µm thick Filled with 1 ml of lipid (ultra pure triolein). Hydrophobic organic chemicals with log K ow > 3.0 are accumulated substantially Sampling rates depend on exposure conditions and compound properties Many other types of sampler are available for such compounds; Chemcatcher, LPE, PMS, POM 7

8 Hydrophobic chemcial samplers - comparison 8

9 Uptake theory hydrophobic samplers Concentration Linear Curvelinear Equilibrium Time The stage of SPM uptake is determined by exposure conditions and duration. Sampling rates determined in the laboratory or by modelling 9

10 o lab R s values apply in the environment? - accuracy of water concentration calculations Bio-fouling Reduction in uptake in SPMs by up to 30-50% The temperature issue R s ~ factor 1-3 per 10 o C Water flow rates Boundary layer control of uptake Photo: Aud Helland, Rambøll 10

11 Uptake in hydrophobic samplers -performance reference compounds (PRCs) Concentration Time Analyte ref H AnalyteH field Fluorene Fluorene 10 PRC field PRC ref H H H H H H H H Uptake affected by exposure specific factors (temperature, water flow rates etc. ) and compound specific factors (physicochemical properties). The PRC approach allows adjustment for the effects of exposure specific factors and tells us how large our sample was (Booij et al., 1998; Huckins et al., 2002) 11

12 PRC release vs. target compound uptake -examples from these studies 100 A CH B Cl 80 H 3 C 80 Cl Cl % 60 % % C ays Examples of target compound uptake and PRC dissipation, from the same SPMs, over a four week period. % Cl Cl Cl Cl Cl Cl Uptake and release curves similar for compounds with similar log K ow Harman Unpublished Ph thesis 12

13 Correction for sampler fouling? R sfoul /R snon Ratio of sampling rates (Rs) for pre fouled and non fouled SPMs vs. hydrophobicity Experimental (squares), PRCs (crosses) and model predicted (dashed line) Harman et al Env. Toxicol. Chem. Log K ow 13

14 PRC results example WCMS 2008 PRC retention (%) Log K ow Harman et al., 2009 Mar. Poll. Bull. A total of 8 PRCs present, 3 used in calculations L water extracted during 6 week deployment Equilibrium reached for compounds with log K ow <4.5 14

15 PRC Summary Inter-site comparisons are hampered by differences in exposure conditions (flow, temperature, biofouling) HOW BIG IS MY SAMPLE? PRCs are always useful identify equilibrium check for inter-site differences in R s / normalise amounts calculate water concentrations (C w ) Water calculation mistakes wrong model incompatible units no surface area correction in R s wrong surface area (L W 2) wrong volume using logk sw instead of K sw 15

16 QC Blanks Blank type Blank description Blank purpose Fabrication (t 0 ) Process Batch of the same SPMs as those for project. (Same batch number if bought). Maintained frozen Made just prior to analysis of a set of SPMs (Labs that assemble SPMs) To correct for contamination in components, during manufacture, storage, processing etc. As above but time of production/storage different Field/ trip Exposed to air while deployment/retrieval is taking place Account for contamination during deployment and retrieval/ transport PRC samples SPM spike Reagent blanks As discussed earlier IST spiked directly into sampler All solvents/ all processes In situ sampling rates/ corrections Recoveries/ control limits (Expected >75% +/- 20%) Background from solvents etc. 16

17 Basic field considerations Representativeness eployment equipment Minimise tampering!! Cross contamination (if also sampling for metals etc..) Use Field Blanks iffusion speed Minimise air exposure Boat fumes, smoke etc. Minimise contact with the membrane and anything else Use gloves Hold cold if possible Use SOPs 17

18 3 Metals sampling - iffusive gradients in thin films (GTs) 18

19 GT - Performance About 30 metal ions collected at phs from iffusion coefficients close to those for ions in water iffusion gel resistance of about %. Good sensitivity - LOs µg/l per 24 hours Acceptable sampling precision of 10-20% 19

20 Uptake in GTs H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Lr Rf b Sg Bh Hs Mt La Ce Pr Nd Pm Sm Eu Gd Tb y Ho Er Tm Yb Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No iffusjonskontrollert opptak i GT Ikke tatt opp i GT Opptak i GT varierer med ph Begrenset kapasitet Opptak av forskjellige grunnstoffer i GT-prøvetakere med Chelex-ionebytter. Garmo et al., 2003, Anal. Chem. (Garmo et al. Anal. Chem. 2003) 20

21 Example of use - prediction of fish stress from aluminum by GTs Glucose and Chloride (mm) y = -0,363x R 2 = 0,79 y = 0,246x - 2,3 R 2 = 0, Gill Al day 7 and 14 (mg/g dw) Trout exposed to acid aluminium rich waters Al gill deposition induces stress Røyset et al., 2005, Environ. Sci. Technol. 21

22 GT sediment sampling 22

23 Muller et al, In prep 23

24 4 Ongoing research Using passive sampler non-detects for determining a maximum theoretical average concentration to fulfil EQS of the WF for compounds such as TBT (0.2 ng L -1 ) L of low pg L -1 Sampling rate data for new compounds Alkylated phenols (Harman et al., 2008, Chemosphere) PBEs (Allan et al., In prep) Further development of polar samplers Non PRC based environmental corrections? Semi quantitative calculations of emerging contaminants, pharmaceuticals, etc. In situ bioassay development 24

25 Sampling for methyl-mercury New MERX instrument for methylmercury. By distillation, ethylation and CV-GC-AFS 25

26 Application to routine monitoring - standardisation Expanded use in monitoring and risk assessment Predictive tool ischarge compliance Fingerprinting Standardisation First international standardisation document BSI (PAS61:2006) Possible ISO standard coming Passive sampling included in the chemical monitoring activity (CMA) documentation for WF (EA in Britain use for EQS compliance?) workshops/workshops 26

27 What about the non-freely dissolved fraction? 27

28 General summary Passive techniques offer effective sampling and extraction in one step, in situ Has significant advantages over traditional sampling/ monitoring methods. Careful handling required both in the field and in the lab to avoid contamination - blanks Use an appropriate PRC based approach for sampling hydrophobic organic compounds Excellent possibilities for expanding use, new applications and inclusion into routine monitoring 28