Mercury speciation in fish

Transcription

1 Mercury speciation in fish Milena Horvat, Janja Snoj Tratnik, Ana Miklavčič, Majda Pavlin, Urška Kristan, Ajda Trdin, Ingrid Falnoga, Vekoslava Stibilj, Darja Mazej, Vesna Fajon, et al., Department of Environmental Sciences, Jožef Stefan Institute, Slovenia ERAChair Isofood: Summer School, Speciation of elements in food,

2 Content Hg convention - Minamata Convention Mercury analysis and challenges Mercury in fish Conclusions and future research needs

3 Minamata Convention - a regulatory mechanism to decrease environmental Hg loadings. Paris Climate Agreement reduction of climate changing anthropogenic gases Hg is a persistent chemical, MeHg bioaccumulates and biomagnifies Recognizing that once released it actively cycles in the environment for hundreds-to-thousands of years before being buried in sediment

4 Minamata Convention on Mercury A global treaty to protect human health and the environment from the adverse effects of mercury Agreed at the 5 th session of the Intergovernmental Negotiating Committee (INC) in Geneva, Switzerland, 19 January 2013 Adopted at the diplomatic conference in Kumamoto, Japan, on 10. and 11. October, 2013 Ratified on 16. August,

5 Minamata Convention

6 Minamata Convention & Article 19 Monitoring levels of mercury and mercury compounds in environmental and biological media Harmonized methodologies Information on the environmental cycle, transport, transformation and fate 6

7 Mercury & EU Directives Directive 2004/107/EC on ambient air Directive 2010/75/EU on industrial emissions Directive 2013/39/EU as regards priority substances in the field of water policy 7

8 Concetration vector Hg 2+ Hg Contaminated sites

9 Log Concentration Speciation analysis is a challenge in water, sediments, soils % % MeHg in various environmental and biological matrices ,1 0,01 0,001 0,0001 0,00001 Air Water Sediment Biota THg MeHg % MeHg

10 Exposure pathways in humans Forms of Hg Inorganic Hg species Organic Hg species Exposure pathways dental amalgam accidental spills of Hg fever thermometers or certain energy-saving light bulbs occupational exposure foodstuff (Hg contaminated sites) air (Hg contaminated site) CONSUMPTION OF FISH AND OTHER SEAFOOD! use of thimerosal (ethylmercury thiosalicylate) as a preservative in some vaccines Hg 0 Inhaled: % Oral route: negligible Hg 2+ Oral route: 10-30% MeHg Oral route: 95% The toxicity of Hg depends on chemical species, level, duration and route of exposure. DIETARY COMPONENTS IN FOOD can affect the outcome of exposure.

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12 What is safe? Intake levels estimated to be safe: 4.3 µg Hg per kg body weight per week FAO/WHO, 1987 Variations: - risk assessment assumptions - data sets - uncertainty factors 0.1 µg MeHg per kg body weight per day EPA (United States Environmental Protection Agency), µg MeHg per kg body weight per week Joint FAO/WHO Expert Committee on Food Additives (JECFA), µg MeHg per kg body weight per week The EFSA Panel on Contaminants in the Food (CONTAM), 2012

13 CHEMICAL METROLOGY Sampling + Processing + Measurement = Result Representative Dissolution Comparison to SI units ± uncertainty Appropriate Extraction or conventional scale Contamination Dilution Stability Handling 13

14 Detection principles Colorimetric ng/mL Au-resistance 50 ng/ml XRF 1-5 ng/g GC AES 0,05ng/mL GC ECD 0,01-0,05ng/mL CV AAS 0,01-1 ng/ml 500 Concentration range (pm) 0,01 >50 mg/kg EXAFS XANES ICP AES 2 ng/ml Electrochemical Detectors 0,1-1ng/mL ICP MS <0,01 ng/ml CV AFS < 0,001-0,01ng/mL (R)NAA 0,1-1 ng/ml 14

15 CV AAS vs. CV AFS Less sensitivity Logarithmic response; Limited dynamic range Interferences Tekran 15

16 Measurement principles for Total Hg Aqueous solution Manual Reduction CV AAS Easy to maintain, field applications; 0,01 ng/ml Preconcentration (Au, Pt, amalgamation) Detection (CV AAS, CV AFS, ICP MS, AES,..) Automated Combustion amalgamation CV AAS High throughput, reproducible, sensitive 16

17 Measurement principles for Hg speciation/fractionation Liberation from its matrix (acid leaching, alkaline dissolution, volatilization, distillation, super fluid extraction, microwave assistance) Extraction/cleanup/preconcetration (Solvent extraction, derivatization such as ethylation, butylation, hydration and iodination; cryogenic trapping; preconcentration on solid phases ) Automated Separation of Hg species (gas chromatography; HPLC; IC, ES, ) Quantification (CV AAS, CV AFS, MS,..) 17

18 Mercury and selenium levels in fish available on the Slovenian market 1,4 1,2 1,0 mg/kg 1,0 n=10 n=18 Maximum allowed Hg level for predators. 0,8 0,6 0,5 mg/kg 0,4 Maximum allowed Hgn=24 level for other fishery products. 0,2 0,0-0, Fish samples selected according to the trophic levels Fresh fish samples selected according to their trophic levels 1: herbivores, feed on plankton, 2: feed on small fish, crayfish, cephalopod, 3: top predators 1: herbivores, feed on plankton 2: feed on small fish, crayfish, cephalopod 3: top predators Se (mg/kg) THg (mg/kg) MeHg (mg/kg) Se (mg/kg) THg (mg/kg) MeHg (mg/kg) Miklavčič et al., 2011 Food Chemistry

19 Total Hg in fish from the Adriatic Sea Box-and-whiskers plots (median with 5, 10, 25, 75, 90 and 95 th percentiles) of THg concentrations in the most studied fish species from the Adriatic Sea. Dotted and dashed lines correspond to the EU maximal allowed THg levels of 0.5 and 1.0 µg g -1 (* on graph), respectively. (Živković et al., submitted)

20 Hg and Se in fish Bull ray: weight vs. Hg in muscle. N=15. Muscle = 1,05±0,02 Bull ray: weight vs. Hg in liver. N=15. Liver Hg (mg/kg dw) 6,0 5,0 4,0 3,0 2,0 Bull ray THg IHg MeHg Enzymatic extraction/ solid residue 1,0 0,0 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 Se (mg/kg dw) 20

21 Lobinski R., pers. com Evolution of speciation analysis in biological systems Determination of mercury compounds/fractio ns in body fluids and tissues Hg 0, Hg 2+, MeHg +, EtHg + Me 2 Hg, etc Identification of unknown metallobiomolecules Complexes with Proteins, Nucleic acids, Carbohydrates Other elements such as Hg-Se- S -compounds Studies of bio-chemical reaction mechanisms

22 Speciation in biological system 22

23 Speciation vs. fractionation Speciation: Chemical species. Chemical elements: specific form of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure Speciation analysis. Analytical chemistry: analytical activities of identifying and/or measuring the quantities of one or more individual chemical species in a sample Speciation of an element; speciation. Distribution of an element amongst defined chemical species in a system Fractionation: Process of classification of an analyte or a group of analytes from a certain sample according to physical (e.g., size, solubility) or chemical (e.g., bonding, reactivity) properties. Templeton et al., Pure Appl. Chem. 72, 2000,

24 Hg isotopes Stable isotopes Isotope measurements of Hg (sources and pathways) 7 Hg stable isotopes (MDF and MIF) 13/12 CH 3 -Hg- Isotope dilution methods (validation of analytical methods and studies of transformation processes) Radioactive isotopes 203 Hg 197 Hg 14 CH 3 Hg- 24

25 MDF vs. MIF fractionation Photochemical processes generate strong MIF on odd isotopes ( 199 Hg, 201 Hg) Biological processes generate only MDF Single-collector ICP MS: 0,1% Multi-collector ICP/MS: 0,001% PRECISION 25

26 Concentratio n Donard, Berail, et al., 201 Hg analysis = Speciation Why? Where? : Tracking sources and fate of Hg in the environment - Soil and sediments - Air - Water - Biological tissues - Lichens

27 Sampling/stora ge/freeze drying Stabilization/ Equilibration time Isotope dilution analysis - IDA If cmehg/chg 2+ <0,05 Preconcetratio n Sample + enriched isotope spikes of n Hg(II) and/or Me nx Hg Extraction Separation If cmehg/chg 2+ >0,05 Derivatizatio n Detection by MS or ICP MS High degree of precision and accuracy but spikes must behave identically to natural endogenous species D-IDA D-SS-IDA IPD Adopted from Clemens et al

28 Conclusions Methods for THg and MeHg analysis in fish are well established and supported by certified reference materials (CRMs) Future research needs to address the following issues: Availability of inorg. Hg and MeHg in fish Hg and Se interactions Source apportionment of MeHg in fish Human susceptibility & MeHg exposure from fish 28

29 Acknowledgments ARRS: P Programme EU ERAChair Isofood EU Masstwin EU Pro-Metrofood,... H vala za pozornost!