Best technologies versus current practices in mercury contaminated land management: Results of the IMaHg survey

Transcription

1 Best technologies versus current practices in mercury contaminated land management: Results of the IMaHg survey Enhanced knowledge in mercury fate and transport for Improved Management of Hg soil contamination C. Merly, V. Guérin, Y. Ohlsson, D. P.-E. Back, Berggren Kleja, D. Jacques, B. Leterme, R. Sweeney

2 Mercury Regulatory Context Stringent regulatory framework for mercury emissions and risk control Negotiations at international level: UNEP GC/GMEF (2007 and on going) Minamata international convention (2013) Legally binding document in preparation (2013) At EU level Banned export of metallic mercury outside Europe (2008) End of industrial use of Hg ( ) No EU specific regulations for managing mercury present as non pure phase product in the various compartments of the soil. => Need for improving and sharing expertise in identifying, assessing, managing and remediating mercury.

3 Mercury CL management issues and challenges Multiple sources of emissions: industrial, mining & coal combustion Diffuse and point source pollution Multiple forms of mercury having very different fate and transport Very variable toxicity Leterne & Jacques 2012

4 IMaHg Project objectives Main objectives Improve the understanding of mercury speciation (chemical forms) and partition (physical forms) in the vadose zone Give recommendations for characterisation, assessment and management of mercury contamination Stress gaps and future needs to improve management of mercury contaminated land. Specific objectives To compile physical, chemical and thermodynamic constants of mercury forms & to improve mercury geochemical modelling To compare available and currently used practices in characterisation, risk assessment and management of mercury To draw some recommendations and identify further research needs for mercury management

5 Methodology EU wide consultation based on a questionnaire designed in four sections Characterisation Risk assessment Remediation References of national technical guidance Feedback on current practices interesting case study Difficulties faced & needs for future R&D Regulatory aspects Implementation of Hg regulation Development of guidelines for Hg management Targeted audience: service providers, problem owners, regulators and researchers Dissemination through national contacts points and CL networks such as SNOWMAN, Common Forum, Heracles, NICOLE Hg Working group and Eurodemo+, International Committee on Contaminated Land.

6 Results overview on participation 39 answers 18 countries: 13 EU countries, 5 non EU countries 6 5 University Research Institute Industry Regulatory bodies 4 Service providers Austria Belgium Czech Republic France Germany Ireland Lithuania Netherland Poland Spain Sweden Swissland UK USA Australia New Zealand Reported case studies: 1/3 Chloroalkali-plants, mining activities, other industrial activities, measurement equipment industry, electric industry and wood treatment plant industry. South Africa Brazil

7 Results Characterisation 24 answers Soil Sediment Groundwater Sub-surface compartments ph, E H Clay content Solid organic content Other parameters

8 Results Soil Characterisation Soil sampling technologies Issue of volatilisation Downwards migration Soil screening was performed in 30% of the cases Analyses of speciation in 42% of the case 100% Hg 0 75% Methylmercury 38% Cinnabar Four types of solid speciation metods: extraction, thermal desorption, spectroscopic and EXAF Need for method standardisation and development to provide reliable solid speciation at reasonable price

9 Results Water & Gas Characterisation Characterisation of Hg speciation - Water 1/3 case reported speciation Need for reliable analytical method HgCH 3 Water Passive samplers and specific probes gave bad reproducibility Gas analysis were performed in 1/5 of the reported cases in order to determine: 1. Ambient air (73%) 2. Soil gas (36%) 3. Indirect Source identification (45%) Systematic characterisation of Hg 0 and organic mercury half of the reported case study Need for better qualified operators for better data acquisition and interpretation

10 Results Characterisation Pitfalls (1 is very important and 5 is the least important) Representativeness 2,1 Knowledge of mercury species fate and transport 2,1 Loss of mercury associated with sampling protocol 2,8 Change of in situ conditions, while sampling 3,0 Matrix effect 3,0 Needs for new tools Yes No Improvement For solid For water 5 2 For gas For fauna For flora Technologies exists but must be used more systemically Solid: Speciation (Speciation analysis and Solid Phase Thermo Desorption), Standardization of sampling strategy Water: Speciation Flora: Assessment of mercury deposition

11 Results Risk assessment 21 answers 2% 12% 5% 29% Human health Ecology/environment Groundwater 14% Surface water Fish 17% 21% Crops/vegetables Others Protection targets for mercury contamination Mercury species: Total mercury was usually considered in the RA Organic mercury was considered in 10% of the cases Human Health RA: 40% comparison with generic guidelines values 40% site specific RA 20% combination of both generic and specific

12 Results Risk assessment Exposure pathways depends on phase partitioning Kd approach Measurements of pore gas and pore water concentrations Geochemical modelling Improvement for risk assessment Complex as it is site specific Oral intake pathways bioavailability tests Vapor intrusion pathways - pore gas measurements Development of Hg-specific transfer model (vapor exposure in particular) Better understanding of the MeHg bioamplification and accumulation in the foodchain For ecosystems, measurements of methylmercury apart of total Hg By more systematic application and definition of toxicological dose-effect-values (RfD, RfC, UR, etc.) for all Hg-Species

13 Results - Remediation 20 answers Type of remediation thresholds Did you look at mercury forms to select the remediation technology? Yes: 42% No: 58% If Yes, in accordance with Regulatory bodies, pilot test, based on RA, available treatment

14 Results - Remediation Type of remediation technologies used (in-situ vs ex-situ) For contaminated soil For contaminated water For contaminated gas: capture on activated carbon

15 Results Remediation difficulties Main difficulties encountered Remobilisation of Hg during the remediation process 1,9 Insufficient knowledge in Hg fate and transport 2 Lack of Hg contamination characterisation 2,3 Matrix effect 2,6 Achievement of the remediation goal 2,6 Lack of efficient remediation technologies 2,8 Presence of cocktail of Hg species having very different fate in the environment 3,1 Interaction of mercury with other contaminants 3,2 Solutions Only ex-situ method used By prior technical-economic feasibility study and field pilot tests Good and Enough sampling and quick measurement

16 Results Remediation Technology development and implementation Re-inforce passive & in-situ treatments for cost reduction More cost effective techniques for element mercury recovery from soils as opposed to segregation, solidification and disposal Management / Guidelines Spread of mercury by earthmoving equipment during excavation work is a concern that must be managed Development of a guideline for BAT selection Importance of a very good characterisation Further education and understanding on fate, transport and species of mercury

17 Results Regulatory aspects 13 responses Level of importance of mercury in CL management depends on the countries Mercury set as a priority compounds In Spain, Czech Republic, Belgium, (Australia) Not in France, Switzerland, the Netherlands, and Lithunia (Brazil) Risk from mercury contaminated sites in comparison with the risks from other means of exposure medium for Czech Republic, Netherlands, (Australia & Brazil) high for Spain, France and Switzerland low for Lithuania. National Hg specific technical guidelines: Germany and France

18 Conclusions Assessment of current Hg management practices Coming IMaHg technical reports Characterisation report: Synthetic information on advantages, drawbacks, conditions of use and regulation acceptance of all the main analytical methods and characterisation tools. Risk assessment report: Strategy for improved site specific risk assessment of Hg contaminated sites. This involves for the most important exposure pathways the current practice, potential for improvements and the estimated effect on the risk assessment outcome. Remediation report: Performance of remediation technologies, their applicability in EU context, their acceptance regarding the risk associated with adverse effects from the remediation works (remobilisation to the air and/or water) and their efficiency regarding the different forms of mercury

19 Thank you for your attention