Background
It is often challenging to remove all contamination sources when dealing with heavily contaminated sites.
On a metal-treating plant in Kvistgaard that lies within an area of special drinking water interest four hot-spot areas with TCE contamination have been found. The majority of the contaminant mass is located in till in both the vadose zone and the saturated zone. A smaller part of the TCE-mass has been found in the underlying saturated sandy aquifer, which may be in hydraulic contact with the primary groundwater aquifer in the area. Risk assessments based on the investigations carried out on the site show that the contamination poses a risk towards the groundwater resource and, in the long run, a risk for the nearest abstraction wells.
A strategy for remedial actions has been proposed focusing on the following three areas; tilly vadose zone, tilly saturated zone and sandy saturated zone (see the figure below). In connection with evaluation of appropriate and suitable remedial methods, the risk assessment has been expanded with the purpose of establishing cleanup levels, which are expected to give the desired environmental effect.
Objective
The objective of the talk is to give an example of a specific risk assessment used to optimize a remedial strategy towards removal of chlorinated solvents. Furthermore the risk assessment is used to evaluate the necessary scope of remediation and the consequences if it is not possible to remove all the contamination, i.e. to illustrate the environmental benefits when using different cleanup levels at each of the four hot-spots. Uncertainties in the risk model, in the selected points of compliance and end-point concentrations and the effect hereof on the resulting risk assessment and choice of remedial action will be discussed.
Content and results
The risk assessment uses back-calculations for each of the four hot-spots to assess 1) the total flux of TCE that is acceptable in the nearest abstraction wells and 2) the flux of TCE that is acceptable in different points of compliance downstream the contaminated site. The calculations take into account that there are more contaminated sites in the area and that the current site therefore is not the only source of TCE contamination of the aquifer. The risk calculations are carried out with Risc5 and DTUV1D.
The relation between source concentrations and the concentration in one or more downstream points of compliance, f.ex. the nearest abstraction well, is described with the aim of assessing the extent of cleanup, cleanup levels and the resulting remedial effect.
The calculation and risk assessment show that the Danish Groundwater Quality Criteria cannot be complied with 100 m downstream the site even though the source areas are cleaned up. Calculated end-point concentrations in points of compliance further downstream in relation to different remedial methods are compared with the overall environmental effects and remedial costs. On this basis the risk assessment makes it possible to select the most suitable combination of remedial methods in order to protect future drinking water interests.
Sellafield is the UK facility for Nuclear Fuel Reprocessing and Waste Management. It is a compact coastal site with an area of around 3 km². It is currently operational and is expected to remain licensed until 2120.
Radioactive material has entered the sub-surface environment during operations following accidental leaks. This material is currently under active risk management prior to a final hazard reduction and remediation phase. Sellafield Ltd is to understand and control the legacy of ground contamination to ensure protection of the workforce, the public and the environment. The main control exercised over this material is through an extensive monitoring and risk modelling programme. This work generates a quantity of important environmental data gathered at public cost. Sellafield Ltd wish to ensure that the best use is being made of appropriate methods for the sampling and analysis of these data.
Soils and groundwater data are necessarily spatially correlated and require dedicated geostatistics data processing. Different spatial anisotropies are observed in the saturated and non-saturated zones and integrated in the model. Uncertainty quantification of contaminated volume estimates according to several radiological waste thresholds is addressed to improve risk analysis (remediation feasibility, costs, waste management…). Finally, a critical review of the sampling effort identifies under- or over-sampled areas based on the spatial auto-correlation description.
Limited exposure from desorption-resistant PAHs in soot and soils
Philipp Mayer1, Varvara Gouliarmou2, Mette Algreen1, Andreas Loibner3, Chris D. Collins4, Ulrich Gosewinkel Karlson2, Kyle James5, Rachel E. Peters5, Steven D. Siciliano5, Stefan Trapp1
1 Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
2 Department of Environmental Science, Aarhus University, Roskilde, Denmark
3 Department for Agrobiotechnology, University of Natural Resources and Life Sciences Vienna, Tulln, Austria
4 Soil Research Center, Reading University, RG6 6DW, UK.
5 Department of Soil Science, University of Saskatchewan, Saskatchewan, Saskatoon, CANADA
Urban soils are generally diffusely contaminated with polycyclic aromatic hydrocarbons (PAHs) by atmospheric deposition of pyrogenic particles such as soot. Additionally at highly polluted sites, much of the PAHs are strongly bound to the soil matrix. Sorption is in both cases the governing process for many exposure and fate processes, which renders total PAH concentrations insufficient for risk assessment and management1. This asks for the implementation of the availability concept in risk assessment and management of contaminated sites, which requires addressing the underlying assumption that desorption-resistant contaminants in solid matrices give rise to limited exposure. Within the Danish REMTEC project, wood soot was incubated in contaminant traps2 for more than one year to remove the readily desorbing polycyclic aromatic hydrocarbons (PAHs) and to isolate desorption resistant PAHs. Four approaches were then applied to rigorously characterize the exposure originating from the desorption-resistant PAHs in the soot, which in some cases was compared to the PAH exposure in agricultural and industrially polluted soils:
(1) Bioaccessibility. Commonly used bioaccessibility extraction methods have insufficient sink capacity for bioaccessibility measurements of PAHs from soot and soils3. Therefore, a new sorptive physiologically based bioaccessibility extraction method had to be developed4,5 and was then applied to determine accessible PAH fractions, which were 1-2 orders of magnitude lower in the treated compared to the untreated soot.
(2) Chemical Activity. Equilibrium sampling was applied to measure chemical activity and freely dissolved concentrations of PAHs6, which were 1-3 orders of magnitude lower in the treated compared to the untreated soot.
(3) Oral uptake. Ιn vivo swine experiments were conducted to determine the systemic uptake after oral administration. Pyrene systemic uptake was 1.3% in the untreated compared to 0.6% in the treated soot, while the respective systemic uptake of benzo(b+k)fluoranthene was 0.9% and 0.4%.
(4) Plant uptake. Plant uptake experiments with radish and diffusive flux experiments using as PDMS passive sampler, were conducted in soils with and without soot addition. The soils used were an agricultural and industrially polluted soil. Concentrations were higher in root than stalk of the plants, and both were rather similar between all soil treatments despite large differences in PAH content and exposure parameters.
Overall, the conducted research supported that desorption-resistant PAHs give rise to limited exposure. Although soot and other pyrogenic materials can contain high concentrations of PAHs, desorption resistance and high KD values will often strongly reduce the actual exposure and risk. Relevant and reliable analytical methods and well defined availability parameters are thus needed to characterize and quantify the actual exposure potentials of a contaminated site, which generally will be elaborated by the combination of readily desorbing and desorption resistant PAH fractions.
Acknowledgements. This research was mainly funded by the Danish Council for Strategic Research through the project “Innovative Remediation and Assessment Technologies for Contaminated Soil and Groundwater (REMTEC)”, and we acknowledge additional support from the European Commission through the project MODELPROBE and the European Regional Development Fund (EFRE) and the Government of Lower Austria (project MACATA, WST3-T-95/017-2012).
References
1 Reichenberg F, Gosewinkel Karlson U, Gustafsson Ö, Long SM, Pritchard PH and P Mayer. 2010. Low accessibility and chemical activity of PAHs restrict bioremediation and risk of exposure in a manufactured gas plant site soil. Environmental Pollution 158: 1214 – 1220.
2 Mayer P, Olsen JL, Gouliarmou V, Hasinger M, Kendler R and AP Loibner. 2011. A contaminant trap as a tool for isolating and measuring the desorption resistant fraction of soil pollutants. Environmental Science and Technology 45: 2932–2937.
3 Collins CD, Mosquera-Vazquez M, Mayer P and Gouliarmou V. 2013. Is there sufficient ‘sink’ in current bioaccessibility determinations of organic pollutants in soils? Environmental Pollution 181: 128-132.
4 Gouliarmou V and P Mayer. 2012. Sorptive Bioaccessibility Extraction (SBE) of Soils: Combining a Mobilization Medium with an Absorption Sink. Environmental Science and Technology 46: 10682–10689.
5 Gouliarmou V, Collins CD, Christiansen E and P Mayer. 2013. Sorptive Physiologically Based Extraction of Contaminated Solid Matrices: Incorporating Silicone Rod As Absorption Sink for Hydrophobic Organic Contaminants. Environmental Science and Technology 47: 941-948.
6 Reichenberg F, Smedes F, Jönsson JÅ and P Mayer. 2008. Vials with polymer coatings of multiple thicknesses for equilibrium sampling of hydrophobic organic compounds in soil. Chemistry Central Journal 2008, 2:8.
Antimicrobial resistance is a growing public health concern in European hospitals and communities. Escherichia coli is one of the most common agents of bacterial infection which causes urinary tract infections as well as more serious infections. E. coli resistance to major antibiotics classes is increasing worldwide.
The aim of the project is to investigate the prevalence of extended-spectrum beta-lactamase (ESBL) producing E. coli in waste water treatment plants in the Burgundy region and to monitor the impact of treated effluents and sludge on water quality in the Ouche watershed near Dijon (East-central part of France). CTX-M is a recently occurring ESBL, encoded by the blaCTX-M genes, which causes resistance to 3rd generation cephalosporins (3GC).
A regional strategy for sampling surface and ground waters will be carried out in relation to existing data, in order to evaluate the capacity of CTX-M producing E. coli to spread and survive in water resources.
Based on previous data on E coli occurrences, we carried out sampling campaign through the studied watershed in order to evaluate the presence of E. coli and CTX-M producing E. coli in groundwater, surface water and springs. We also used molecular methods to monitor the presence of the blaCTX-M genes.
To characterize the dissemination of ESBL producing E. coli in the aquatic system, we have selected several sampling points according to hydrogeological contexts, land use and waste water plants with a particular interest for karst aquifers that are predominant in the studied area. Karst aquifers constitute an important volume of water resources but they are highly vulnerable to pollution even fecal coliform. In soils and aquifer, fecal coliforms are known to suffer retardation and degradation by sorption and filtering and die off. However, where by-pass occurs by preferential (fast) pathways (cracks, fissures and conduits) none of the retardation and degradation processes is effective.
For each sampling point, we combined microbial and chemical approaches.
Cultural detection of E. coli and ESBL producing E. coli was done by plating of selective TBX medium alone or supplemented with cefotaxime (3GC). Cefotaxim resistant isolates were then characterized by antibiotic susceptibility tests and MLST fingerprinting. blaCTX-M genes were monitored by real type PCR following DNA extraction.
Chemical analyses on inorganic elements (Major, trace elements) were performed to characterize the water composition as a tool to understand the water fluxes able to mobilize E. coli and identify the source of ESBL producing E. coli. Knowledge on water composition contributes to characterize hydrogeological features (rock type, time of contact…) mainly by understanding water-rock interactions of the studied system. Water composition allow to define chemical types of waters and anthropic pressure on water using chemical tracers such as agriculture pressure (NO3) or waste water (Boron). These classical parameters have been completed by analyses of REE among them Gadolinium. For tracing the different inputs of pharmaceutical products (that are related to antibiotic resistances) to groundwaters, several specific chemical markers are simultaneously monitored: Gadolinium, caffeine, carbamazepine, ibuprofen and acetaminophen. Positive Gd anomaly has been produced by the application of multidentate organic complexes of Gd in hospitals and clinics, as a contrast medium in magnetic resonance imaging (MRI) since 1988. From a hydro-geological point of view the anomalous Gd represents an excellent tool to trace the mixing of recycled water with surface and groundwater.
From the presence or absence of ESBL producing E. coli we attempt to identify the sources and vectors of water contamination by studying waste water treatment, land use (sewage sludge) and water fluxes in the studied watershed. The occurrence of CTX-M producing E. coli in groundwater resources and particularly the persistence of antibiotic resistance genes (ARG) such as blaCTX-M might constitute a health risk.
The LQM/CIEH S4ULs published in December 2014 are the third edition of generic assessment criteria published since 2006. The 1st and 2nd editions of the LQM/CIEH Generic Assessment Criteria rapidly gained widespread acceptance among practitioners and regulators. In 2012, the 2nd edition was specifically recognised within statutory guidance issues by the Secretary of State to support the contaminated land regime in England and in Wales. The S4UL are published alongside a set of collated information on the toxicity and transport properties for some 85 common contaminants to inform site-specific generic quantitative risk assessment (GQRA).
Although the terms ‘generic assessment criteria’ or ‘GAC’ were often used as synonyms for the 2nd edition LQM/CIEH GAC, these generic terms are also applicable to soil screening thresholds derived by a number of other companies and organisations. Furthermore, the ‘new’ LQM/CIEH S4ULs introduce a number of changes in relation to the modelling assumptions used, and include values for more land uses and substances. Consequently, it was considered appropriate to use a new, individual and specific name for the new criteria – the LQM/CIEH Suitable 4 Use Levels (S4ULs) - to differentiate them from other sets of assessment criteria and indicate their role under the planning regime.
The publication of the S4UL comes at a time when the future direction of government guidance on human health risk assessment of contaminated soils in the UK is being reviewed by Government. In March 2014, Defra published Category 4 Screening Levels (C4SLs) for six contaminants. These are based on a unique toxicological benchmark, the ‘low level of toxicological concern’ (LLTC) rather than the ‘minimal or tolerable level of risk’ basis for the Health Criteria Values defined in SR2 (Environment Agency, 2009a) and which underpin all previous Environment Agency Soil Guideline Values (SGVs) and other GACs. This is because the C4SLs were primarily intended for use under Part 2A of the Environmental Protection Act 1990 to quickly screen out Category 4 sites, where there is “no risk or that the level of risk posed is low”. There has been considerable, and inconclusive, debate amongst contaminated land practitioners and regulators about the applicability, and wisdom, of applying the lower standard of protection represented by the C4SLs, underlain by the less cautious LLTCs, outside of the Part 2A context for which they were derived. For example, under the planning regime sites need to be shown to be “safe” and “suitable for use”. We believe that the use of the current six C4SLs under planning requires an informed decision and site-specific justification by landowners, developers and their advisors to ensure that that the development meets the requirements in the National Planning policy Framework in England and its equivalents in the devolved administrations.
However, we also believe that ongoing safe development in the UK requires an up-to-date set of generic assessment criteria covering a wide-range of the contaminants commonly encountered during the redevelopment of previously developed land, and that are appropriate for the low soil organic matter contents often present in such soils. As such the S4UL remain based on the principles of ‘minimal’ or ‘tolerable’ risk enshrined in current Environment Agency guidance. Thus, the S4ULs are equivalent to the SGVs and previous editions of the LQM/CIEH GAC and hence are relevant ‘suitable 4 use levels’ for use in generic quantitative risk assessments under both the planning and Part 2A regimes.
Smouldering and thermal remediation processes are capable of achieving significant hydrocarbon contaminant mass reductions in soils over relatively short periods of time. Smouldering exposes soils in the treatment zone to temperatures on the order of 600-1100°C for periods of hours to days. Temperature and exposure duration are related to the contaminant type, extent of contamination, soil type, and other site-specific characteristics as well as remediation design parameters. Thermal remediation exposes soils to temperatures of ambient to 750°C for periods of weeks to months. Exposure temperature links to the type of heating used, proximity to heating source, and other design parameters while exposure duration is a consequence of remediation progress and operational decisions. For sites where substantial contaminant mass removal has been achieved, redevelopment including the installation of new infrastructure is possible; however, the effects of high temperature remediation on soil condition are not well understood. Hydrocarbon contamination is known to reduce soil strength. The extent to which soil strength may recover after remediation is unknown. This research explores the effects of high temperatures and associated physical changes on soil strength and geostructure stability after high temperature remediation so that safe redevelopment of formerly contaminated sites will be possible.
This study used sand and a mixture of 90% sand and 10% kaolin as simple soils. Soil samples were subjected to temperature treatments of 105°C, 250°C, 500°C, 750°C, or 1000°C in a furnace to capture the range of exposure conditions encountered during thermal remediation. Subsequent samples were artificially contaminated with 70,000mg/kg coal tar and subjected to smouldering remediation in a 3L vessel in a laboratory setting. An additional sample from a 3m3 smouldering experiment was tested to explore the effects of increased remediation scale and exposure duration. Changes to soil particle size distribution, porosity, surface mineralogy, and other characteristics were determined and compared to the characteristics of untreated soils.
Soil strength was evaluated with a 10cm x 10cm shear box testing using 400g specimens. Soil specimens were delivered to the shear box with aid of a pluviator. Once the specimen was in place, a loading plate was used to establish a vertical stress on the material. The shearing rate was fixed at 0.05mm/s. Vertical stresses of 50, 100, and 150kPa were tested. Subsamples of prepared materials were subjected to cement stabilisation, cured for 28 days, and tested for strength using a triaxial test in order to evaluate their suitability for a typical geotechnical stabilisation technique.
Soil physical properties were affected by heat treatment with changes apparent in particle size distribution, surface mineralogy and other characteristics. Differences were apparent between the sand and sand/kaolin mixture. Some properties such as particle size distribution were not determined for the smouldered samples because of the transfer steps led to particulate losses.
Soil strength linked to exposure temperature with decreases in calculated friction angle noted in the sand. These differences likely associate with mineral changes and potential smoothing of the grains. Kaolin experienced mineral transformation to meta-kaolin and mullite as well as thermal degradation, but these transformations seemed to have the effect of insulating the sand from heat exposure and filling the gaps between the grains. Where decreases in calculated friction angle were noted in the sand-only specimens, increases in calculated friction angle with increasing exposure temperature were observed in the sand/kaolin mixtures. The exception to this trend was the smouldered specimen. Cohesion was variable for all specimens but the smouldered seemed to be slightly less than the heat-treated specimens. Subsequent chemical analysis showed some hydrocarbon contamination remained and this factor combined with handling losses of fines during transfer of material to the shear box may explain the differences.
Post-remediation materials subjected to cement stabilisation were faster to cure and stronger based on triaxial testing. Although the calculated friction angle results reflect slightly lower strength in the field, the same factors that contribute to the lower strength may be benefits in terms of cement stabilisation. The clays interact less with the water and behave more as very fine sands, meaning that the water is taken up faster by the cement and curing starts faster. These preliminary results are promising for field applications of cement stabilisation after remediation, though further tests are necessary to evaluate the full complexity of field geotechnical stabilisation.
Based on these results, field practitioners need to be aware that these high temperature processes may affect soil properties. Site investigation after remediation should be used to establish the geotechnical properties of the post-remediation soil as neither unaffected soil nor pre-remediation contaminated soil will accurately reflect ground conditions. Based on preliminary tests, if soils require stabilisation measures, post-remediation soils seem amenable to one common soil stabilisation technique. Further testing is underway to explore more complex soils and other possible stabilisation techniques.
Expert centre PFCs: Adressing the problem of emerging contaminants
With an increasing frequency chemicals that have not historically been considered as “contaminants” are present in the environment on a global scale. Some of these substances could be a potential risk to humans and the environment and others are harmless. How do we determine the difference and how do we cooperate with stakeholders to address this issue?
Typical examples of these emerging contaminants are PFOS and PFOA (PFCs). Both are applied on a large scale, and both might cause a significant environmental problem. But characteristic for emerging contaminants is that too little is known about the occurrence, the actual risks and approach to formulate appropriate standards and legislation. To properly identify how to deal with PFCs and related emerging contaminants, knowledge, awareness and understanding is necessary.
Although much research on emerging contaminants as PFOS/PFOA/PFCs has been done, information and results are often not accessible outside the academic world. Because of a lack of information, decisions on how to deal with these substances are delayed, legislation is missing and practical solutions are not developed.
In the Netherlands, we therefore started an ‘Expert centre PFCs’ to connect the fields of policy and legislation, science, stakeholders and problem owners and business communities. PFOS is seen as a pilot to come to an approach on how to deal with emerging contaminants, including hormones, medicines, etc.
By making use of the case PFCs, the following challenges are explored:
- which decisions about emerging contaminants have to be made at different levels (production, business, research, polity and legislation);
- which information about emerging contaminants is essential to make these decisions;
- how to ensure that scientific information about emerging contaminants is used in practice, and that people act accordingly. And the other way around: how can practice address important issues and examples to science.
Goal of the Expert centre is to create a ‘ playing field’, in which policy makers in different countries can use the same information about emerging contaminants to base their policy on and explore cost effective and sustainable strategies to deal with these issues.
Keywords: PFCs, emerging contaminants, risk assessment and management
Background / Introduction
Damhusdalen is a residential areaestablished in the 1920s. During development, the land surface was leveled with waste products from porcelain factories among others. The dumping has contaminated the area with hydrocarbons, tar compounds and heavy metals.
In 2004, the Capital Region of Denmark investigated all the properties in the areawith a limited amount of soil samples. The sampling strategy included one borehole per property to determine the thickness of the fill layer and analysis of one soil sample from 0-0.1 and one sample from 0.4-0.5 m. bgs.
The investigations indicated contamination with tar compounds, heavy metals and oil products over at concentrations exceeding DanishMCLs. The top soil (0-0.5 m.bgs) on 150 properties was contaminated. A total of 176 properties out of 180 were identified as contaminated based on the fact that the deeper fill (>0.5 m.bgs) was likely to be contaminated compared to the contamination levels found in the first half meter. Subsequently, the upper 0.5 meters of soil fill were studied with a greater sampling density.
In 2010-2012 the Region studied the results from all the investigations in the area, to obtain an overall representation of the contamination. Based on these studies, the region decided that it was necessary to examine the contamination throughout the whole fill layer, in order to assess whether some properties were in fact uncontaminated.
New studies
The Capital Region performed additional investigations on a total of 42 properties. The purpose of the studies was to gain
• knowledge about the thickness of the fill layer on the examined properties and
• information on the contamination profile throughout the fill.
Based on the results of the new investigations, a statistical evaluation of the level of contamination in the fill soil in the whole area was performed. The primary objective was to investigate whether it was possible to assess the level of contamination in the fill soil deeper than 0.5 meters based on knowledge of the contamination levels in the upper 0.5 m of soil.
The data set consisted of 10.246 analyses in 31 different depths of 229 boreholes spread over 42 properties.
Statistical evaluation
The average analysis for the whole area
Based on the contamination levels in the boreholes, the probability of finding contamination in the fill soil below 0.5 meters, when the fill soil above 0.5 m is uncontaminated, is 10%.
In 13% of all the boreholes, the fill soil was contaminated at depths exceeding 0.5 m. In 31% of those, the fill soil above 0.5 m was also contaminated. Based on this, 24 % of boreholes with contamination in the upper 0.5 meters were also contaminated at depths greater than 0.5 meters.
I.e. to assume that the soil below 0.5 m. bgs is either contaminated or uncontaminated based on findings in the upper 0.5 meters, will include a risk of mapping uncontaminated soil in 75% of the cases and not mapping contaminated soil in 10% of the cases.
Geostatistical view of the area
From a geographical perspective, it is assessed whether it is possible to draw relevant correlations between the individual boreholes based on the compounds and the contamination levels found above and below 0.5 meters bgs.
A view of the substances individually shows that PAHs and heavy metals have a clear geographical correlation between the boreholes at a distance up to 40-60 meters - some with geographic correlation of up to 100 m in fill soil layers both above and deeper than 0.5 meters. For hydrocarbons there is little or no geographical correlation.
Strategy for contaminant mapping in Damhusdalen
Based on the results from the statistical evaluation the mapping status of the properties have been revaluated. Properties located outside the correlation distance of nearby boreholes are evaluated on the average statistical data.
Properties which have previously been registered as contaminated are still registered unless they are within correlated distance from boreholes.
The results of the evaluation
Approximately 30% of the properties in the residential area have been taken out of the soil contamination registry based on the statistic assessments for the area.
The Danish Regions are responsible for locating and remediating the contaminated sites posing a risk for groundwater that is used or can be used for drinking and/or pose a risk to human health.
The large number of contaminated sites within The Capital Region of Denmark necessitates a prioritization of the worst cases in order to maximize the profitability of the available resources. Today, initial prioritizing and risk assessment of individual contaminated sites depends on the specific solutes in question and their maximum concentration. Traditional transect methods with groundwater gradients and hydraulic conductivities are used to guide such prioritization. However, with improved knowledge on groundwater contaminated mass flux this could be optimized and make way for a more efficient use of available resources to target and remediate the most damaging or high-risk sites first.
As part of a still innovative development within the field of remediation of soil pollution, The Capital Region has joined collaboration with the company Sorbisense to develop a flux sampler. The flux samplers ability to give information about groundwater flux, flow direction and mass concentrations can help to an improved prioritization and risk assessment between individual contaminated sites. Moreover, it can be used to delineate soil contamination on already located contaminated sites and also to evaluate the effectiveness of ongoing remediation or natural attenuation.
Within the Capital Region the flux sampler is currently being tested on various projects, all initiated in 2014. These projects range from initial investigations where contaminated sites are located, to supplementary investigations, remediation projects and to reassessing remediation on older projects.
On 9 initial locations investigated for contamination, 10 flux samplers are installed with the purpose of getting an expression for the source strength and dispersal pathways (flow direction) of the specific solutes that have been shown with ordinary groundwater samples. The flux samplers are primarily installed in the secondary groundwater aquifer. This test should give us an indication of the benefits from using the flux sampler already in the initial stage of locating contaminated sites and guide the risk assessment and further prioritization.
In a remediation project with supplementary investigations where a heavy tar hotspot has been demonstrated near the vicinity of a groundwater abstraction well, 11 flux samplers are installed in various depths extending from 13-40 m.u.t. (primary and secondary aquifer). The purpose is to find the pollution dispersal pathways and flux to guide the remediation project of securing the drinking water. Here preliminary results show a coherent picture of both the flux and flow direction.
Finally, 5 flux samplers where installed in the secondary groundwater aquifer with the purpose of reassessing remediation on an older ongoing project. The challenge here has been relatively large variation in the results from the previously conducted monitoring events possibly due to a very low groundwater flow and inflow to the wells. Hence, the flux samplers are tested to estimate flux and flow direction in a low groundwater flow scenario.
OCCURENCE OF ANTIMONY IN SOIL AND GROUNDWATER AT FORMER SHOOTING RANGES
Jesper Alroe Steen (1), Maren Kann Hostrup (2), Mette Marie Mygind (2), Boerge Hansen (2), Henrik Soegaard Larsen (1), Jacqueline Falkenberg (1)
1. NIRAS A/S, Denmark.
2. Danish Ministry of Defense, Estates and Infrastructure Organisation, Environmental and Nature Section, Denmark
jas@niras.dk
BACKGROUND: Up until 2014, site investigations at military shooting range locations in Denmark have focused on lead as the primary contaminant of concern. Studies of sampling and analytical practice in other NATO countries have identified antimony as a contaminant of possible concern. Currently, Denmark has no quality criterion for antimony in soil or groundwater, which presents problems with respect to the drivers for site investigation and risk assessment.
Prior to site remediation at three shooting range locations, the Danish Defense have analyzed soil and groundwater samples in order to assess the occurrence of antimony. Subsequently, site remediation has been performed based on findings from the site investigations including the screening for antimony and the final risk assessment.
The site investigations have provided information on the presence of both lead and antimony as critical contaminants at former shooting range locations.
AIM: The aim of this presentation is to present recent studies on the occurrence of antimony in soils and groundwater at former military shooting ranges in Denmark. The presentation will include information concerning projectiles and activities that form the basis for the occurrence of antimony at shooting ranges, a correlation between the presence of both lead and antimony, and a comparison with contaminant levels at similar sites in other countries.
A secondary aim of the presentation is to highlight the process (focus on communication with environmental authorities) involved for site remediation if no national quality criteria are derived. The process requires the derivation of clean-up goals and approval by the environmental authorities based on documentation of the risk assessment process.
RELEVANCE: The presentation may be relevant to administrative personnel (national regions, environmental authorities etc.), consultants, entrepreneurs and others involved in site investigation and remediation at shooting range locations.
PROJECT: The project has included a literature study on the occurrence of antimony at shooting range soils, including a correlation for the presence in the soil of both lead and antimony (no national data existed).
Pre-investigations, including discrete soil and groundwater sampling, prior to site remediation, at three Danish shooting range locations have been performed in order to assess the occurrence of antimony. At the three locations, antimony was found in top soil in concentrations up to 515 mg/kg DW, 265 mg/kg DW and 12 mg/kg DW, respectively, and lead was present in concentrations up to 18,600 mg/kg DW.
As a significant supplement to the discrete soil sampling, Multi Incremental Sampling (MIS®) has been used to estimate average contaminant concentrations in target areas.
Groundwater samples have been collected from screened intervals in wells in the target area. Antimony concentrations in groundwater (ranging from non-detects to 2.2 µg/l) have been compared to the average antimony concentrations in soil in target areas illustrating the potential for leaching of antimony to the groundwater.
Based on these investigations, risk assessment has been performed in order to evaluate the potential risks to human health due to soil contact and on groundwater quality.
In relation to site remediation at the three specific shooting range locations, a proposal for a soil criteria for antimony has been prepared. The Danish EPA has undertaken to publish by early 2015, a national Danish soil and groundwater criterion for antimony which will be included in the presentation.
The presentation will also include data from the three site remediations, including the procedure for clean-up documentation.
CONCLUSION: Antimony and lead do co-exist in soil at shooting range locations. As the bullet core consist of 92-95% lead, 2-5% antimony and traces of other metals, contaminant concentrations at shooting range locations will be dominated by lead, but antimony can be a significant contaminant.
The mobility of antimony due to leaching from contaminated soil is greater than the mobility of lead, however both contaminants are strongly adsorbed to soil particles and transport in the unsaturated zone is thus greatly retarded.
Nevertheless, groundwater concentrations of antimony have been documented, indicating that the leaching of antimony does occur, although the calculated vertical transport times are very low.
For future investigations at shooting range locations, it will be relevant to sample for antimony, especially in relation to the pending national Danish soil and groundwater criteria for antimony.
The 1960’s and 70’s saw a growing awareness of the risks posed by soil and groundwater contaminations in The Netherlands. This was followed quickly by legislation on pollution prevention and maintenance of soil and groundwater quality in the 1980’s. Since then, thousands of potential groundwater contaminations have been researched and hundreds of sites have been remediated. More than 30 years later contaminations with chlorinated volatile organic compounds (VOCs) remain a persistent problem. Remediation is often more challenging than appears at first sight. Also on remediated sites, residual contaminations can still be present.
These historic contaminations originate mainly from spills at dry cleaners and metal processing sites. Besides perchloroethylene (per) and trichloroethylene (tri), vinylchloride (monochloroethylene, VC) is usually found in contaminated groundwater bodies. Vinylchloride is formed in groundwater as the result of the degradation (dechlorination) of per and tri. VC is highly volatile and harmful to humans, even at low exposure levels. As a result, the Dutch exposure model for assessing indoor exposure risks of volatile compounds in groundwater, VOLASOIL, often predicts an exceedance of the risk limit of VC in groundwater.
In practice, however, the presence of VC in the indoor air of buildings located over groundwater contaminations is rarely confirmed by site specific air measurements. For some time there is the presumption that degradation of VC in the unsaturated zone plays an important role in the rapid decrease of indoor air concentrations of this substance. Recent studies indeed show that VC degrades faster and on a larger scale under a variety of conditions, than was assumed earlier.
We present a simple approach to incorporate first order degradation in the existing equations for diffusive and convective transport of the volatilization model VOLASOIL. With this calculation method, it is possible to perform a more realistic assessment of the exposure of VC (and possibly other substances) due to volatilization and degradation in the unsaturated zone. The results obtained with the extended VOLASOIL model have been compared with site specific measurements. Combined with the most appropriate method for air sampling of VC, using canisters, it is possible to do a more extensive validation. This approach can also be implemented for VC in other human exposure models. With relevant degradation data the model can also be applied for other organic compounds (e.g. BTEX).
During large constructions of roads or structures, unexpected acid rock drainage (ARD) can be caused by local mineralization containing sulfides in the geology. The potential of ARD occurrence of a certain area sometimes must be assessed before initiation of any engineering earth works. However, it is difficult to assess the entire area through collecting rock samples and predicting the potential by laboratory tests, such as the acid-base accounting method. In this study, a new prediction protocol using a geochemical exploration survey technique of stream sediment is proposed. Sediment samples were collected at the case study area where a large development is expected in the future, and the contents of some major and heavy metal elements were compared according to the major geologies of the sampling points. The modified geoaccumulation indices (Igeo) of Fe, Pb and As could indicate a possible zone of pyrophyllite mineralization, which may cause the occurrence of ARD at the study area. Using the enrichment index of the three elements relative to the median values of the area, a high potential zone of ARD could be designated, which was in agreement with the laboratory ARD prediction tests of the rock samples. In the other areas with different mineralization processes, other metallic elements can be selected as indicators of the ARD potential. Likewise, the potential of the occurrence of ARD at an area can be assessed by evaluating the geochemical distributions and drawing the indicator elements for ARD through a stream sediment survey.
Biocides are common additives in building material. In-can and film preservatives in render and paint, as well as wood preservatives are used in order to protect façade materials from microbial spoilage. However, it is known that these compounds with fungicidal, bactericidal and algaecidal activity leach out of the material when it gets in contact with rainwater. While in city centers the total façade runoff drains on paved surfaces like streets and terraces and further into the sewer system, the runoff in residential areas drains to a certain amount to beds or the lawn surrounding the houses.
Based on a monitoring study of stormwater runoff from a residential catchment as well as direct façade runoff analysis, the present study was assessing the pollution of urban soil to biocides from building material. The stormwater runoff of a residential catchment in Silkeborg (Denmark) was monitored over nine months. The catchment covered 140 single family houses with a total façade area of about 24000 m2. However, only 25% of the total façade area was expected to release biocides (render, painted wood). Median concentrations of 45 and 52 ng L-1 (7 and 8 mg event-1) have been detected for carbendazim and terbutryn, respectively. The other studied biocides were usually lower. However, in some rain events the concentrations reached concentrations up to 1.8 µg L-1 (77 mg event-1), possibly resulting from freshly rendered or painted façades.
Emissions of freshly treated façades measured on artificial walls ranged from 1 to 10 mg m-2 event-1. Hence, the emissions of a freshly treated house with a façade area of 160 m2 might range from 40-400 mg event-1, since only one side of the house is exposed to the driving rain. Assuming the peak emissions of 77 mg in the stormwater monitoring to result from a freshly painted or rendered house, it is obvious that a huge part is actually draining directly to the soil and not to the sewer system. Consequently, the soil in urban areas is exposed to stormwater highly polluted by biocides which might affect the microbial community there.
The goal of this study is to develop a high-effective system for an ecological risk assessment and risk-based decision making for anthropogenic ecosystems, with particular focus to soils of the Kyrgyz Republic. The project is focused on the integration of Triad data including chemical, biological and ecotoxicological soil markers to estimate the potential risk of soils from highly anthropized areas impacted by the deposition of pollutants from mining operation. We will focus on technogenic area of Kyrgyzstan: the former uranium-producing province Kadzhi-Say.
Currently, Triad-based ecological risk assessment (ERA) and multi-criteria decision analysis (MCDA) for technogenic sites are not implemented in Kyrgyzstan. However, the vitality of such research is self-evident. There are about 50 tailing dumps and over 80 tips of radioactive waste, which are formed as a result of uranium and complex ores (mercury, antimony, lead, cadmium and etc) mining around the aforementioned unfavourable places. According to the Mining Wastes’ Tailings and Fills Rehabilitation Centre established in 1999 by special Government’s Resolution, one of the most ecologically dangerous uranium tailings is in Kadzhi-Say. Although uranium processing is no longer practiced in Kadzhi-Say, a significant number of open landfills and uranium ore storages remain abandoned along the vicinity of this settlement. These neglected sites have enormous problems associated with soil erosion and are known as “technogenic deserts”. The upper soil horizons are deprived of humus and vegetation, which favor the formation of low-buffer landscapes in the zones of maximum contamination. As a result, most of these areas are not re-cultivated and remain in critical environmental condition.
In this study Triad data for assessing environmental risk and biological vulnerability at contaminated sites is integrated. The following Triad-based parameters are employed: 1) chemical soil analyses (revealing the presence of potentially dangerous substances), 2) ecological parameters (assessing changes in microorganism’s community structure and functions, bioindication); 3) toxicological bioassays (utilizing classical endpoints such as survival and reproduction rates, genotoxicity). The output consists of 3 indexes: 1) Environmental Risk Index, quantifying the level of biological damage at population–community level, 2) Biological Vulnerability Index, assessing the potential threats to biological equilibriums, and 3) Genotoxicity Index, screening genotoxicity effects. This approach integrates a set of environmental Triad data obtained during study, which is carried out in order to estimate the potential risk from soils of highly human-impacted areas, called Kadzhi-Say, which have been primarily impacted by deposition of heavy metals and radionuclides.
The following tasks are solved:
• Characterization the physical-chemical parameters of soils with different sources of contamination. This task includes: (i) gathering historical data about land use; (ii) soil sampling campaigns for model technogenic sites for correct selection of the reference; (iii) assessment the mineralogical parameters, structural soil features, basic chemical and organic matter content; and (iv) mapping potential pollutant sources.
• Description the features of soil microbiota in the contaminated sites (in situ). Biological data (bioindication endpoints) include classical synecological parameters of bacterial and microscopic fungal (micromycetes) communities: (i) species indices of the taxonomic diversity of microbial communities; (ii) total biomass of bacterial and fungal cells, spores and mycelia; (iii) bio-morphological biodiversity and viability of fungal biomass – spore-mycelia ratio; and (iv) ratio of fungi and bacteria in the biomass of different samples of soil.
• Study of functional characteristics of soil biota. This category of testing includes parameters of fermentative activity of contaminated soils; determination of quantitative and qualitative content of enzymes, which carry out oxidizing reactions - peroxidase, catalase, and the reaction of hydrolysis - amylase, urease in soils. In addition with this multisubstrate and respirometric testing of samples to discriminate the fungal and bacterial activity after contamination of soils by different pollutants will be performed.
• Measurement toxicological endpoints in different model test-organisms. Bioassay responses obtained from organisms which represent different trophic levels: (i) producers (green algae and higher plant); (ii) consumers (crustacens and protozoan, mammalian cell culture), (iii) reducers (luminescent bacteria and pure culture of micromycete).
• Detection non-quantifiable attributes of microbe communities - presence of dark- pigmented toxicant-resistant fungi, pathogenic microorganisms, etc.
It will be created intellectual ecological models for the analysis of structural damage of the technogenic soils and soil cenoses based on complex of chemical and biotic parameters using multi-criteria decision analysis.
Acknowledgements. This work is supported by the ISTC grant (project KR-2092).
Carcinogenicity of benzo(a)pyrene (BaP) is one of the concerns related to polycyclic aromatic hydrocarbons (PAHs). This study investigates the mineralization of BaP using biocatalytic reactions of hemoglobin (Hb) and hydrogen peroxide (H2O2). Lab-scale oxidation tests (24 h) were carried out using 0.02 g Hb (2 g soil)-1 and 0.08 g H2O2 (2 g soil)-1. BaP degradation was 40% in the presence of both Hb and H2O2, while it was only 20 and 30% under the Hb-only and H2O2-only conditions. Toxicity test were performed with two luminescent bacteria, luxAB-marked YH9-RC and V. fischeri. Vibrio fischeri which is seawater originated halophilic microorganisms are commonly used for toxicity test. Janthinobacterium lividum is the groundwater borne microorganisms and well known as oligotrophic bacteria. The J. lividum YH9-RC used in this study is artificially generated luminescent bacteria possessing pUTluxAB vector of E.coli with harboring lux gene of V. fischeri. The concentration of BaP was decreased from 10 to 6 mg kg-1, and its removal efficiency was 40%. The EC50 values evaluated with two luminescent bacterial species were lower in BaP-contaminated soils compared to uncontaminated soils. The increase of EC50 was positively related with removal rate of BaP in both procedure using two luminescent bacterial species. The decrease of TU was positively related with BaP concentration degrade in both procedure using two luminescent bacterial species. Since the standard of soil toxicity has not published yet, examination of toxicity in both biocatalyst treated soils and uncontaminated soils is difficult. further study to create the standard of toxicity in soils will be necessary. In addition, this study using J. lividium YH9-RC showed more sensitive TU than that of V. fischeri. Advanced studies on J. lividium YH9-RC are essential. I suggested that toxicity test using freshwater microorganisms such J. lividium YH9-RC is more appropriate than that using seawater microorganisms like V. fischeri when soil samples are targeted.
The remediation of contaminated sites with important metal impacts in soil can be highly expensive, especially for conditions whereby in situ remediation or soil treatment is not technically feasible. In such situations a high resolution site characterization can contribute significantly to reducing the volumes to be excavated and disposed of on hazardous waste landfills at elevated unit costs.
The combination of a risk based approach, a high resolution field screening method and geostatistical techniques can contribute significantly to reducing the costs and the resourceintensity for site characterization and remediation, without compromising on the overall objective of land remediation, hence contributing to more sustainable remediation scenarios.
For a former battery production site with lead impact in soil exceeding 10 000 mg / kg dm, XRF (X-Ray Fluorescence) field screening was undertaken to support the high resolution site characterisation over an area of approximately 10 000 m². This method allows for obtaining a lot of data in a cost efficient and time efficient way with 100 direct analyses per day obtained on site by one field engineer, without sample transport and waste generation issues.
A geostatistical approach was used to determine the52 locations where XRF lead measurements were to be undertaken, with four discrete XRF samples over the vertical profile (first meter below ground surface with 25 cm intervals) for each of the 52 locations. The optimal location of these 52 sampling points was derived from historical information including lead laboratory analyses for 35 soil samples. A genetic sampling optimization algorithm aimed at putting the 52 new points in areas where they would contribute significantly to reducing the width of a 90% confidence interval associated with the mapping of lead concentrations. The algorithm tends to add points in areas where both concentrations and uncertainties are high and the algorithm should therefore efficiently contribute to reducing the overall uncertainty on the contaminant distribution in the subsurface. The selection of the XRF sampling points was undertaken in two phases with 22 sampling points for the first phase, the XRF results of which were then integrated in the sampling optimization algorithm to determine 30 additional XRF sampling locations for the second phase. In summary, the 52 XRF sampling locations were selected in a way that the overall uncertainty on the pollutant mapping could be reduced most efficiently.
A limited number of soil samples was sent to the laboratory to calibrate the 226 XRF field measurements taken at 52 locations. Estimated lead concentration maps where then produced with 3D kriging. Also stochastic simulation was used to produce probability maps expressing the likelihood to exceed the risk based remediationtarget value, allowing for optimising the contaminant mass removal and impacted soil removal still respecting the overall remediation objective.
Cd containing pigments are used in artists’ paints since begin of 19th century. CdS (PY35, Cadmium yellow) is one of the most important pigments in this group. More recently they are in the focus of environmental scientist due to possibly negative effects the use of these pigments may have for the environment. One possible pathway into the environment is cleaning used brushes with water and subsequent waste water treatment in sewage plants. The Cd sulfide settles together with the activated sludge in the sedimentation basin. Due to its high nutrient content this sludge is often used as fertilizer for agricultural used soils. This application will also transfer the Cd sulfides to the soil. For risk assessment knowledge about mobilization of cadmium from this pigment is necessary as mobile Cd can be transported to the groundwater or be introduced in the human food chain after up take by plants. Cd is toxic to aquatic organism and to humans, is suspected to cause cancer and harmful to the bone structure.
The Cd sulfide itself is sparingly soluble. However oxidizing or acidic conditions result in free Cd ions. Thus, the mobilization potential of Cd has to be determined under realistic environmental conditions. Column percolation tests are often used for investigations of leachable amounts as there a good compromise between effort, gained information and realistic conditions. In contrast to lysimeter studies accelerated experiments are possible enabling predictions for prolonged scenarios.
In this work the results of such percolations test under different redox conditions are presented. Sewage sludge spiked with Cd pigments was mixed with soil containing different amount of organic carbon. These materials were percolated using artificial rainwater up to a liquid to solid ration of 10. The redox potential was measured directly after the column outflow on-column. Eluate samples were taken during this time period and analyzed for Cd concentrations. Conductivity, pH-value, turbidity and DOC concentrations were also measured.
The redox potential is decreasing fast after start of the percolation and shows a clear relation to the organic carbon content of the soil material: eluates of columns with higher organic carbon show a slower decrease in redox potential. In accordance to the redox potential more Cd is released from soils with higher redox potential.
LEACHING AND TRANSPORT OF PERFLUORINATED COMPOUNDS AT A FIRE FIGHTING TRAINING SITE AT AN AIRPORT IN NORTHERN NORWAY
Øystein Seim Solaas (1)*
Gijs D. Breedveld (1, 2)
Beate Løland (1)
(1) Department of Geosciences, University of Oslo, PO Box 1047 Blindern, 0316 Oslo, Norway
(2) Norwegian Geotechnical Institute, PO Box. 3930 Ullevål Stadion, 0806 Oslo, Norway
* Corresponding author e-mail: o.s.solaas@kjemi.uio.no
Background
Perfluorinated compounds (PFCs) have for a number of years been spread to the environment at Norwegian airports through the use of aqueous film forming foam (AFFF) as a firefighting agent. PFCs are a group of chemicals that are persistent in the environment, and bioaccumulate in organisms. One PFC which has received most attention is perfluorooctane sulfonate (PFOS), which is identified as a priority hazardous substance in EU's water framework directive (WFD) (2013/39/EU).
Although the use of PFC containing AFFF has ceased, this investigation has revealed that high amounts of PFCs are still present in the soil at an airport in northern Norway. PFCs are continuously leaching from the soil to nearby water bodies. PFOS is the dominating PFC still present in the soil. The concentration of PFOS in the receiving inland surface water is exceeding the environmental quality standard set forth in the WFD.
Aim and relevance
The aim of this project was to determine the occurrence, fate and transport of PFCs at the airport. This was achieved through water and soil analysis and column experiments. The results have been used to develop a model for determining the fate and transport of PFCs at the site.
Project
Determination of PFCs in soil and soil water was carried out at several locations downstream a firefighting training site at the airport. Column experiments were carried out on undisturbed soil profiles to determine the partitioning characteristics of PFCs in the soil. This enabled modeling of the behavior of PFCs in the soil and hence an estimate of the environmental impact on recipients could be reached.
Conclusion
The results from the investigation at an airport in northern Norway have been used to develop a model for determining the fate and transport of PFCs. The model will be used to determine the potential effect of remedial actions at the site.
AP Reis1,2, I Santos1, S Costa1, C Patinha1, Y Noack3, J Wragg4, AJ Sousa5
1GEOBIOTEC, Departmento de Geociências, Campus Universitário de Santiago, Universidade de Aveiro, 3810-193 Aveiro, Portugal
2CICECO, Departmento de Química, Campus Universitário de Santiago, Universidade de Aveiro, 3810-193 Aveiro, Portugal
3Aix-Marseille Université, CNRS, CEREGE, UMR 7330, BP 80 13545, Aix en Provence Cedex 4, France
4British Geological Survey, Keyworth, Nottingham, NG12 5GG, United Kingdom
5CERENA, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
house dust
This study reports to data obtained from a pilot survey focusing on household dust collected from 20 home residences in Estarreja, a Portuguese industrial city. The study aims mainly at investigating the influence of the dust mineralogy in the oral bioaccessibility of Cr and V. Nevertheless, the relationships between concentrations of Cr and V in dusts collected from indoor and outdoor areas of the house, as well as their relationships with other chemical elements, were also investigated. An increased knowledge on such relationships is important to better understand the bioaccessibility estimates. A total of 21 households were recruited for the pilot study: 19 households in the urban area of Estarreja, forming the exposed group, plus 2 households from residential areas with no anticipated Cr and V that were used for comparison. The mineralogy of the indoor dusts, which was determined by X-Ray diffraction, is simple and composed by variable proportions of quartz, K-feldspar, Na-plagioclase and calcite. Semi-quantitative analysis of 55 chemical elements, including Cr and V, was carried out by Inductively Coupled Plasma - Mass Spectrometry. Average total Cr concentrations are more elevated in indoor than in outdoor house dusts and the difference is statistically significant (p < 0.05). For V, average concentrations are more elevated in outdoor house dusts and the difference is also statistically significant (p < 0.05). However, concentrations in the house dusts are similar to the ones obtained for control sites. Total metal concentrations in indoor dusts are not correlated with concentrations in the outdoor dusts, neither for Cr nor for V. Principal component analysis (PCA) applied to the entire data set shows that Cr and V are separately assigned to two uncorrelated clusters. It is worthwhile to point out the strong correlation obtained for V and Mn. The joint projection of variables and samples in the 1st PCA factorial plane also shows that the Cr-containing group of elements clusters due to metal concentrations in outdoor dust samples, while the V-containing group is associated to indoor dust samples. These results indicate that, for the dataset under study, outdoor metal sources are probably prevalent for Cr while indoor sources may be important contributors to the total V concentrations in the house dusts. Oral bioaccessibility measurements were obtained using the Unified BARGE Method (UBM) on a sub-set of 9 indoor dusts. The results used in this study report to the ones obtained in the gastric phase (G-phase) of the UBM protocol that provided higher extracted concentrations and better repeatability values, and was therefore used as a surrogate of oral bioavailability. The bioaccessible fraction (BAF) of Cr in the dusts varies between 16 and 35% and does not correlate with total Cr concentrations. Similar results were obtained for V that has BAF values ranging from 34-55%. Thus, important metal fractions are probably unavailable for absorption in the gastrointestinal tract following incidental dust ingestion. Investigation on the relationships between metal concentrations (total and bioaccessible) and mineralogy was carried out through simple linear regression analysis. No relationships were found between total concentrations of both metals and the mineralogy of the dust. However, for V the results show that increasing proportions of calcite in the bulk sample correspond to increasing estimated BAF values. Yet, the same relationship was not obtained for Cr. Several factors can be proposed to explain this distinct behavior for Cr and V.
Decabromo diphenyl ether (deca-BDE or BDE209) is the fully brominated congener in the family of polybrominated diphenyl ethers (PBDEs). Since the 1970s, PBDEs have been added to polymeric materials to inhibit their flammability. More recently, neurological and endocrine disrupting effects of PBDEs have been found alongside the detection of PBDEs in a wide range of biotic and abiotic samples from urban areas to the most remote regions such as the Arctic and Himalayan Plateau. Subsequently, the Stockholm Convention meetings (2011) added some of the lower brominated congeners to the list of Persistent Organic Pollutants (POPs), and in October 2013, the inclusion of Deca-BDE to the POPs list has been proposed. More scientific information about Deca-BDE fate, transport, and environmental availability is essential to support this evaluation alongside development of remediation strategies to address its presence in the environment.
This work investigates the adsorption and desorption kinetics of deca-BDE on four soil fractions: sand, silt, kaolin for the clay fraction, and peat to simulate the soil organic matter. Kinetics are calculated using the OECD batch method. In order to close the mass balance, an analytical method has been developed for the analysis of deca-BDE in both water and soil fractions. Solid samples are extracted through accelerated solvent extraction (ASE) and water samples by evaporation and substitution with acetonitrile. Concentrated solutions are than analysed by high performance liquid chromatography (HPLC) equipped with a UV detector. The HPLC analytical method has a limit of detection of 0.03mg/L and limit of quantification of 0.09 mg/L. The only inconvenience of using a UV detector instead of a mass spectrometer is the coelution of interference peaks, which could not be distinguished from the analyte. This problem is limited to the highly organic peat samples.
The experimental kinetic curves are fitted with first order kinetic models with one and two compartments. The two-compartment kinetics model has more degrees of freedom and fits the experimental curves better. The physical explanation commonly used to justify the two compartments model is to assume that each compartment represents a portion of soil active sites characterised by a different time that has been reached by the analyte. This research explores soil components and mixtures of soil components to simulate field-relevant conditions. This approach is used to evaluate the effects of heterogeneities in a controlled manner. The kinetics from soils composed in different proportions by the four soil components are compared with the linear combination of the single kinetics. This method also allows for the evaluation of the two-compartment model and whether it could be justified by different kinetics on the soil components.
In addition to the soil constituent properties, including surface interaction and internal porosity, that are taken into account, soil wetting, inter-particle porosity, and compaction may affect the mobility. The resulting information about decaBDE adsorption and desorption is invaluable to efforts to understand its mobility in the environment and develop remediation strategies that can be applied in the affected areas.