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5th Joint Nordic Meetingon Remediationof Contaminated Sites15-18 September 2014
Preliminary program
Registration Early bird
until 23 May 2014
Registration at www.nordrocs.org
NORDROCS 2014
crossing borders
VENUE: Clarion Hotel Sign, Stockholm
PROGRAM The program is subject to possible changes
Monday, September 15, 2014
SHORT COURSES at Clarion Hotel Sign Stockholm
10.00 – 12.00
Short course A - Geochemical modelling, Swedish Geotechnical Institute
Short course B – Reuse of material, Swedish Geotechnical Institute
12.00 – 13.00 Lunch
13.00 – 17.00 Short course A - Geochemical modelling, Swedish Geotechnical Institute (ends 16.30)
Short course C – Using the GeoProbe system for high resolution investigations at contaminated sites, NIRAS
18.30 – Joint walk from the hotel to Stockholm City Hall
19.00 – Welcome reception at Stockholm City Hall
Tuesday, September 16, 2014
09.00 – 10.00 Registration and coffee
10.00 – 12.00 OPENING SESSION Banquet hall, Hotel Clarion Sign
Malin Norin, NCC, Sweden, chair of Nätverket Renare MarkPeter Harms-Ringdahl, Empirikon Konsult, Sweden, coordinator of the organizing committee of NORDROCS 2014Chair: Jan Darpö, Professor, Department of Law, Uppsala University, Sweden EU Legislation applying to Contaminated sites management and future needs - Key note speaker: Dominique Darmendrail - COMMON FORUM, General secretary, France
Nordic EPAs, strategies and visions followed by discussion with the audience
12.00 – 13.30 Lunch, poster session and exhibition
to be continued
13.30 – 15.30 SESSION A
Sustainability Chair: Ingegerd Ask, Nyköping Municipality, Sweden Key note speaker: Igor Linkow, Ph.D., US Army Engineer Research and Development Center, Adjunct Professor, Carnegie Mellon University, U.S.A
A Sustainable Approach to Remediation of Kopeopeo Canal, New Zealand - Rob Burden, Domain Environmental Ltd, New Zealand
Re-use of material in Stockholm Royal Seaport - Anna Pramsten, City of Stockholm, and Helena Hellgren, NCC Construction, Sweden –
Initiatives towards sustainable use of excavated soil in the Capital Region of Denmark, and the creation of the Soil Portal – Jens Gregersen, Capital Region of Denmark and Kristian Kirkebjerg, Grontmij, Denmark
Incorporating sustainability into assessment and remediation of contaminated sites in Finland – Jussi Reinikainen, Finnish Environment Institute, Finland
SESSION B
Investigation and risk assessment Chair: Dominique Darmendrail - COMMON FORUM, General secretary, France Risk assessment of contaminated sites and diffuse sources to water resources - Key note speaker: Poul Bjerg, Professor, Department of Environmental Engineering, Technical University of Denmark
Assessment of soil-water partitioning of polycyclic aromatic compounds using passive samplers and leaching tests. – Anja Enell, Swedish Geotechnical institute
Comparison test on soil sampling containing volatile hydrocarbons - Katarina Björklöf, Finnish Environment Institute and Milja Vepsäläinen, Vahanen Environment Oy, Finland
Risk assessment of landfills in relation to surface water - Sanne Skov Nielsen, Orbicon, Denmark
Methodology for fast and reliable investigation and characterization of contaminated sites - Jørgen Mølgaard Christensen, DGE Group A/S, Denmark
15.30 – 16.30 Coffe break, poster session and exhibition.
16.30 – 17.30 SESSION C
Protecting indoor air
Chair: Marja Tuomela, Ph.D., Research scientist, University of Helsinki, Finland
Detecting intrusion pathways of contaminated soil gas to indoor air and describing remediation methods – Børge Hvidberg, Central Denmark Region, Denmark
Probabilistic risk assessment for six vapour intrusion algorithms - Jeroen Provoost, , Independent Researcher,
Freon – a new contaminant in the field? - Majbrith Langeland, Grontmij, Denmark
SESSION D
New Technologies - Thermal
Chair: Mads Terkelsen, Research and Development Manager, M.Sc. (geology), Capital Region of Denmark, Copenhagen
In-Situ Thermal Treatment of Fractured Rock - Gorm Heron, TerraTherm, Denmark
Indoor thermal remediation in an old industrial area in the Capital Region of Denmark - Katerina Hantzi, Capital Region of Denmark and Pernille Kjaersgaard, Orbicon, Denmark
Thermal desorption - pilot testing in Machelen – Beel Pieter, JV Jan De Nul-Envisan, Belgium
19.00 – 24.00 Dinner, Wasa museum 19:00 (bus leaves 18:30)
Program Tuesday, continued
VAPOUR INTRUSION ALGORITHMS
Probabilistic assessment and sensitivity analysis for six vapour intrusion algorithms used in contaminated land management
Jeroen Provoost1, Jan Bronders2, Ilse Van Keer2
1 Independent Researcher, Finland, ResearchGate: http://www.researchgate.net/profile/Jeroen Provoost2/
2 Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium
The e‐mail address of the presenting author(s): JProvoost‐01(at)yahoo.co.uk
1 IntroductionMany countries have developed contaminated land management (CLM) policies to reduce risks to humans and ecosystems originating from soil pollution (Provoost et al. 2008a). These policies often make use of model algorithms to calculate a soil screening values (SSV) to trigger further actions, such as higher tiers site specific human health risk assessment, or remediation actions to reduce the risks (Provoost et al. 2013). One of the major pathways of exposure for humans is inhalation of indoor air as a result of sub‐surface contamination with volatile organic chemicals (VOC), called vapour intrusion (VI) (DOH 2006). VI is a process not yet well understood. Swartjes (2007) looked into the variation of exposure by applying seven EU models for human health risk assessment, and concluded that the variation for exposure due to indoor air inhalation is large. Provoost et al. (2008a) investigated the reasons for the variation in SSV between different (EU) countries and the effect of harmonising algorithms and parameters on the SSV. The conclusion was that SSV for VOC vary 1 to 4 orders‐of‐magnitude (OoM) between (EU) countries. This is due to the application of different algorithm and its parameter values (scientific elements), while political elements, like toxicological criteria, have a moderate to high influence on the variation in SSV. Although geographical elements differ throughout Europe, they seemed to have a limited impact on the variation. The Common Forum recently released a note, named “Towards an European research agenda for contaminated land management”, which identifies gaps and needs for the different steps of CLM. The note states, for the site investigation step, that phase partitioning in the soil and the resulting VI in buildings needs further investigation. Furthermore it recognizes, for the step risk assessment, that a ‘one size fit all’ model algorithm is not realistic. A deeper understanding is required related to the content and the limits of the models and predicted values (Common Forum 2013).
If algorithms are applied predicting the soil air and indoor air concentration as a result of soil pollution, and the related human exposure, is complex and is affected by numerous factors. These factors are translated into screening algorithm’s parameters. Parameters can be divided generally in three categories: environmental, building and physico‐chemical (McAlary et al. 2011, Provoost et al. 2010), with each category characterised by a degree of uncertainty or variability. The algorithm’s output is therefore subject to two sources of parameter variation: uncertainty and variability. Variability regards variation that can be naturally expected, while uncertainty regards precision by which a quantity is measured (Van Belle 2008). Most of the present algorithms for VI calculate (deterministic) point estimates based on a set of default parameter values and therefore give no indication of the variation and conservatism of the predicted air concentrations.
2 MethodologyMeasured data from two well documented sites were used to compared predictions and observations, and are described in more detail in Provoost et al. (2014). The first site, Astral in Vilvoorde (Belgium), is contaminated with the aromatic hydrocarbons benzene (BE) and ethylbenzene (EB), while the second site, CDOT site in Denver (USA), contains among other chlorinated contaminants mainly trichloroethene (TCE). For both sites the majority of the contaminant source for VI was located in the vadose zone.
The algorithms selected were the Swedish dilution factor algorithm from 1996 (S‐EPA 1996), dilution factor algorithm from Norway (SFT 1999), Johnson and Ettinger model (United States) (Johnson et al. 1999), CSoil (Netherlands) (Brand et al. 2007), VolaSoil (Netherlands) (Waitz et al. 1996) and Vlier‐Humaan (region Flanders in Belgium) (OVAM, 2004).
For each algorithm a probabilistic assessment with sensitivity analysis was applied, as well as the calculation of the deterministic predicted concentrations. Probability distribution functions (PDF) were derived from the data gathered for three groups of parameters (soil, building and physico‐chemical properties for the 3 contaminants) and fed into the algorithms. Data were obtained from site measurements and literature. The PDF in algorithm’s input were propagated into an output distribution of the predicted (soil and indoor) air concentration (probabilistic analysis), and allows an analysis of the contribution of each parameter to the variation (sensitivity analysis). The results are displayed as box‐and‐whisker plots displaying the distribution of air concentrations, and sensitivity stacked bar charts (ranking of parameters according to the correlation between parameter and algorithm output). Algorithm parameters were adapted to site specific conditions where needed.
The predicted concentrations were evaluated against observed air concentrations to determine the accuracy of each algorithm, while the level of conservatism was obtained by comparing the 95 percentile predicted concentration from the probabilistic range with the deterministic predicted concentration. The analysis results in a ranking of algorithms for accuracy and conservatism in predicting soil air and indoor air concentrations, and thus determines their suitability for regulatory purposes.
The accuracy and conservatism of screening‐level algorithms is objectified by calculating the Maximum relative Error (ME), Root Mean Squared Error (RMSE) and Coefficient of Residual Mass (CRM), as described by Loague & Green (1991), for the paired predicted and observed air concentrations. These criteria were applied in Provoost et al. (2008b, 2009, 2014), and also in this study, for inter‐algorithm comparison, and provided a ranking of the algorithms as to their accuracy.
The box‐and‐whiskers plots include the tolerable concentration in air as a reference to inhalation risks of indoor air. Tolerable concentrations were obtained the World Health Organization (WHO 1996, 2010).
To be useful for a regulatory purpose screening‐level algorithms should be sufficiently conservative and may result in few false‐negative predictions. However, they should not be too conservative because then they might have insufficient discriminatory power (Provoost et al. 2009).
3 ResultsThe box‐and‐whiskers plot (Figure 1ab) display the minimum, 25 percentile, median, 75 percentile and maximum predicted soil or indoor air concentration, as well as the predicted deterministic concentration () and, in the case of indoor air concentrations, the tolerable concentration in air () for the pertaining contaminant. Also for each of the contaminants the observed (measured) soil air and indoor air concentrations are displayed to contrast with the predictions. The box‐and‐whiskers plots provide an insight in the spread (range of the values from the highest to the lowest value), and the midspread (range of middle 50% of the values) or also called inter‐quartile range. The location of
the median line relative to the 25 and 75 quartiles indicates the amount of skewness or asymmetry in the data.
DF SE: Dilution Factor algorithm from Sweden, DF NO: Dilution Factor algorithm from Norway, JEM: Johnson and Ettinger model, Vl-H: Vlier-Humaan, Obs: observed concentrations, Box plot: ▬ minimum, median or maximum concentration, box is 25 or 75 percentile concentration, deterministic concentration
Figure 1a. Box-and-whiskers plot for predicted and observed soil air concentrations by algorithm and contaminant
DF SE: Dilution Factor algorithm from Sweden, DF NO: Dilution Factor algorithm from Norway, JEM: Johnson and Ettinger model, Vl-H: Vlier-Humaan, Obs: observed concentrations, Box plot: ▬ minimum, median or maximum concentration, box is 25 or 75 percentile concentration, deterministic concentration, tolerable concentration in air
Figure 1b. Box-and-whiskers plot for predicted and observed indoor air concentrations by algorithm and contaminant
The sensitivity analysis allows for the ranking of dominant parameters to the variation in predicted air concentrations. Parameters were grouped by physico‐chemical, soil or building parameters (Table 1ab) resulting in an overall contribution of the group to the total variation (Figure 2ab).
DF SE: Dilution Factor algorithm from Sweden, DF NO: Dilution Factor algorithm from Norway, JEM: Johnson and Ettinger model, Vl‐H: Vlier‐Humaan
Figure 2a: Stack bars of the percentage that physico-chemical and soil parameter values contribute to the variation in soil air concentrations by algorithm and contaminant
DF SE: Dilution Factor algorithm from Sweden, DF NO: Dilution Factor algorithm from Norway, JEM: Johnson and Ettinger model, Vl-H: Vlier-Humaan
Figure 2b: Stack bars of the percentage that physico-chemical, soil and building parameter values contribute to the variation in indoor air concentrations by algorithm and contaminant
4 Discussion
4.1 SoilairSome of the box‐and‐whiskers plots show a negative skewness towards the higher concentrations. With some exception the deterministically predicted concentrations are in the midspread of the box‐plot (figure 1a).
The deterministic predicted soil air concentrations are overall higher than the median observed concentrations with the exception of VolaSoil and CSoil for benzene. The algorithms that most frequently over‐predict (less accurate) the observed soil air concentrations are the DF NO, VolaSoil and the DF SE algorithms, while the JEM, CSoil and Vl‐H have a higher accuracy.
4.2 IndoorairIn general the box‐and‐whisker plots for predicted indoor air concentrations do not show a particular positive or negative skewness (figure 1b). For predicting the indoor air concentrations JEM, DF NO, VolaSoil and Vl‐H seem to have a higher accuracy than DF SE and CSoil.
The comparison shows that the JEM and Vl‐H are the more conservative algorithms while maintaining some level accuracy (slightly over‐predict). The DF NO and SE, the VolaSoil, and CSoil algorithm have a lower accuracy (mostly over‐predict when compared to observations) and conservatism.
4.3 SensitivityanalysisThe sensitivity analysis allows for the ranking of dominant parameters to the variation in predicted air concentrations. Parameters were grouped by physico‐chemical, soil or building parameters (Table 1ab) resulting in an overall contribution of the groups to the variation (Figure 2ab).
Figure 2a shows that the soil air concentration for BE and EB are driven by the soil parameters and for TCE increasingly by the physico‐chemical parameters, with the exception of JEM. Table 1a provides details on what individual parameters contribute most to the soil air concentrations and for the physical‐chemical properties, depending on the algorithms and contaminant, are: the organic carbon‐water partitioning coefficient, octanol‐water partition coefficient, Henry’s coefficient, solubility and vapour pressure. For soil properties the dominant parameters were: initial concentration and organic carbon fraction.
Figure 2b shows that the most dominant parameters contributing to the variation in indoor air concentration are for BE and EB soil and building parameters and for TCE soil and physico‐chemical parameters. Table 1b reveals that for the physical‐chemical properties the most dominant parameters are, depends on the algorithms and contaminant considered: the organic carbon‐water partitioning coefficient, octanol‐water partition coefficient, Henry’s coefficient and solubility. For the soil properties the water and air filled porosity (correlated), air permeability, initial concentration and fraction organic carbon are dominant parameters. For the building properties the intrusion rate of pore air, soil‐building pressure differential and fraction air in concrete drive the variation.
5 ConclusionsAccording to this study, the screening‐level algorithms that have a higher degree of conservatism for their default parameter set are the Johnson and Ettinger model (JEM), Dilution Factor algorithm from Sweden (DF SE 1996), Vlier‐Humaan and VolaSoil. From these 4 algorithms the JEM and VolaSoil have a relative high accuracy (discriminative power). For the latter two algorithms different parameters, that are variable and uncertain, contribute to the variation in indoor air concentration. Differences between parameters that drive the variation were observed between the aromatic and chlorinated hydrocarbons.
For TCE, the default parameter set of Vlier‐Humaan, CSoil and DF SE 1996 should be adapted to arrive at a higher deterministically predicted indoor air concentration when a more conservative approach is required. The deterministically predicted air concentrations for BE and EB seem to be sufficiently conservative.
It is shown that the probabilistic approach allows for an improved insight into the relative
importance of parameters in the risk estimates. A probabilistic approach should be applied to more
sites to confirm the findings of this study.
Some algorithms are more accurate, but might produce (frequently) false negative predictions. A balance between accuracy and conservatism need to be sought and this balance determines the suitability for site specific assessment and/or deriving of SSV.
Given the above two algorithms for site specific risk assessment could be applied. Some of the algorithms are more accurate, depending on contaminant and source (groundwater/soil) and a “toolbox” with algorithms could be developed. For the algorithms in the toolbox fixed parameters could be defined that can be standardized (e.g. physico‐chemical parameters) and flexible parameters for which a range can be provided (geographical parameters related to the soil and building).
This paper contains content from Provoost et al. 2014. The full paper and data set (parameter values and PDF) can be downloaded from ResearchGate.net.
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