Constructed Wetlands: A promising system

It is easy to leave the tap running without caring about where the water is coming from. How often do we do this when brushing our teeth or washing dishes? However, the real cost of this wastage may be considerable, if we think about the loss of this valuable natural resource and the expense of water treatment. Thinking of wastewater, have you also considered what happens when you flush the toilet or dispose of laundry water containing soap or oils down the sink? Well, our urban wastewater receives treatment before it is discharged to the environment.

However, our situation is not the reality of developing countries, where water is often scarce and water treatment technologies must be reliable and sustainable. Efforts to mitigate negative environmental impacts and reduce public health risks in these countries require the development of low-cost wastewater treatment technologies that effectively eliminate wastewater contaminants; facilitating the breakdown and removal of pollutants using biological processes that avoid the hazards associated with chemical-based systems and their additional cost. A promising wastewater treatment system for this context is constructed wetlands (CW), which can provide sustained access to improved water and sanitation services.

Oksana Voloschenko, a Marie Curie fellow within the ADVOCATE project, is researching the development of this treatment concept, within the topic “microbial nitrogen transformation in horizontal subsurface flow constructed wetlands for the treatment of contaminated groundwater”. The focus is on the removal by CW of ammonium (NH4+) a major pollutant in groundwater from agricultural sources. Firstly, we need an overview of how CW serve as natural wastewater treatment systems for projects carried out in Africa, Latin America or India.

In general terms, constructed wetlands consist of beds of aquatic macrophytes (wetland plants). Their root systems provide surfaces for the attachment of microorganisms, enhancement of filtration effects and stabilization of the bed surface. Moreover, the roots contribute to the development of microorganisms by the release of oxygen and nutrients within the host material. Depending on flow conditions we can distinguish surface flow or subsurface flow CW (horizontal and vertical flow), as shown in the diagrams below.

Figure1

  • Surface flow CW consists of large, shallow lagoons that contain submerged, emergent, or floating plant species. They are most commonly used to remove nutrients to prevent eutrophication (algae growth) in the receiving water body.
  • Subsurface flow CW consist of shallow basins filled with coarse sand or gravel as filter material. Wetland plants are grown on the surface of the filter bed, and pre-treated wastewater flows through the bed horizontally below the surface. Subsurface flow CW can treat both nitrogen and phosphorus.

How do they work?

If we look at subsurface flow CW the main components are: a waterproof basin, filter material, wetland plants and inlet and outlet structures. This is shown in the diagram below.

Figure2

 

The waterproof basin is used to prevent soil and groundwater contamination through wastewater infiltration. Filter material has several functions. It retains solids from the pre-treated wastewater, provides surfaces for the adhesion and development of the microorganisms that play a crucial role in the degradation of organic pollutants and transformation of nitrogen compounds, and supports the development of root systems in the filter material for the wetland plants. Inlet and outlet structures are required for wastewater distribution and collection, respectively.

Our research efforts are focused on understanding the removal mechanism for pollutants, due to the complexity of the wetland systems, and the role that aerobic and anaerobic zones play within the root zone of the plants. This is the Oksana’s research. Obviously, as with all water treatment technologies, CW designs have limitations. These are currently are being studied by researchers such as Oksana.

ResearchBlogging.org

Coban, O., Kuschk, P., Wells, N., Strauch, G., & Knoeller, K. (2014). Microbial nitrogen transformation in constructed wetlands treating contaminated groundwater Environmental Science and Pollution Research DOI: 10.1007/s11356-014-3575-3

How is the choice of remediation alternative influenced by different sets of sustainability indicators and tool structures?

If we take a glance at the scientific literature, particularly those on soil treatments, the number of articles, reports and books available are uncountable. Suddenly the question comes to mind – which treatment is best for a define case? We know that all of them differ from each other and have their advantages and disadvantages, many factors come into play when deciding on the best technology. In addition, variations in boundary conditions defined between technologies, produce distorted environmental impact results. Thereupon, a balance between environmental, social, and economic costs and benefits must be required in identifying the optimal remediation solution. Key indicators need to be defined in each case.

More precisely, an indicator is a single characteristic that can be compared between the different tools to evaluate their relative weight in each technology. An important perspective about the indicators is how they are measured and how all of them are ultimately balanced in the evaluation of potential remediation strategies.

Determining the most appropriate course of action when faced with soil or groundwater contamination requires the consideration of technologies or approaches that can feasibly remove the contamination to the required target level within project-defined time and cost constraints. Consequently, the technology selection phase in the planning process consists of two steps: identify the feasible technologies and evaluate the financial, social and environmental financial costs of the different alternatives.

On the other hand, Decision Support Systems (DSSs) provide us a structured method of comparing these alternative courses. On the commercial market there are many examples of soil and groundwater remediation. Some DSSs examples are MMT (Mega-site Management Tool), DESYRE (Decision Support System for the Rehabilitation of contaminated sites), SBR (Sustainable Brownfields Redevelopment tool), CO2 calculator, SRT (Sustainable Remediation Tool), REC (Risk reduction, Environmental merit and Costs tool) or GoldSET.

Between all the above DSSs described, Alistair Beames and his colleagues from VITO established the use of four of them for its study on a specific contaminated area of Antwerp, exactly a petrochemical storage and distribution facility, providing a meta-analysis of sustainability appraisal of four technically feasible remediation alternatives proposed for the site: ex situ soil washing, ex situ thermal desorption, in situ thermal desorption and monitored natural attenuation.

The results generated after this study are compiled in a more detailed article titled Sustainability appraisal tools for soil and groundwater remediation: How is the choice of remediation alternative influenced by different sets of sustainability indicators and tool structures?

About the tools used, the CO2 calculator is an example of a standard environmental footprint calculator and considers an inventory solely focused on energy consumption and CO2 emissions. SRT and REC are tools with larger inventories across a range environmental impacts that also account for financial costs. SRT aggregates the different criterion scores according to economic valuation. REC integrates different criterion scores within a multi-criteria analysis framework. GoldSET is an example of tools used by consultants on behalf of clients and considers a broader range of impacts across the three pillars of sustainability (environmental, social and economic), many of which are measured qualitatively.

In conclusion, the results generated by these tools differ from one another when applied to the same case study, due to differing indicator sets and aggregation methods. Clearly broadening the scope of the assessment from only a few environmental indicators and financial costs to also considering social impacts and indirect economic impacts will influence the sustainability performance of the remediation alternatives.

All the information is available on the article

Beames A, Broekx S, Lookman R, Touchant K, & Seuntjens P (2014). Sustainability appraisal tools for soil and groundwater remediation: How is the choice of remediation alternative influenced by different sets of sustainability indicators and tool structures? The Science of the total environment, 470-471, 954-66 PMID: 24239816

ResearchBlogging.org

Stimulating bacterial growth to enhance natural biodegradation processes – a low cost treatment option for environmental pollutant removal

                                                           “No amount of experimentation can ever prove me right; a single experiment can prove me wrong.”

Albert Einstein

Naturally occurring bacteria found in soil, groundwater, water and sediments may be a key for environmental pollutant removal. This so-called biodegradation is a part of natural attenuation, which according to the US Environmental Protection Agency could be defined as “The effect of naturally occurring physical, chemical and biological processes, or any combination of those processes to reduce the load, concentration, flux or toxicity of polluting substances without human intervention”. The effectiveness of biodegradation depends on the type of contaminant present as well as on the complex environmental conditions that determine microbial community structure, electron donor availability (the electron donors could be defined as releasing an electron during cellular respiration, resulting in the release of energy. Microorganisms, such as bacteria, obtain energy in the electron transfer processes) and degradation reactions in the subsurface.  Under natural conditions, biodegradation of many contaminants is often a slow process and long timeframes may be required to achieve a remediation objective. Because of this, scientists lately focus more and more on stimulating the growth of that part of the site-specific microbial community that demonstrates the largest degradation potential. Here the idea is to study natural biodegradation processes occurring at a contaminated site in the lab to understand the microbial community structure, kinetics and determine the maximum degradation potential. Once these aspects are sufficiently understood and the site´s hydrogeology has been characterized, a growth-stimulating medium can be injected at certain locations to enhance biodegradation.

Although many studies have been carried over several decades, to improve our understanding of natural attenuation processes there is still a great deal to be learned regarding the mechanisms governing natural attenuation processes and their ability to address different types of contamination problems.

For example, chlorinated solvents, such as tetrachloroethene (PCE) and trichloroethene (TCE), represent a common class of contaminants used for degreasing in the dry cleaning, electronic manufacturing and machine maintenance industries. Where these contaminants had been used excessively in the past they often have leaked into the subsurface from storage tanks and machinery and have formed large plumes in the groundwater that often shows chlorinated ethene concentrations, which have been proven unhealthy.

The bacterium Dehalococcoides mccartyi is an organic halide-respiring anaerobic bacterium that uses chlorinated compounds for its dehalogenation activity. In other words, this bacterium is specialized to grow with halogenated compounds such as chlorinated aliphatic hydrocarbons as electron acceptor via a respiratory process, i.e. an electron-consuming process, and in most of the cases hydrogen is used as the final electron donor.

The removal of chlorinated ethenes by Dehalococcoides mccartyi via dehalogenation follows the sequential degradation of PCE to TCE to the dichloroethene isomers (cis-DCE, trans-DCE, 1,1-DCE), then to vinyl chloride (VC) and finally to ethene/ethane. However, a complete dechlorination always depends on the environmental conditions and other limiting factors. During the last two decades, several studies have been carried out based on the addition of electron donors for achieving a complete removal of chlorinated compounds, nevertheless, no convincing conclusions have yet been drawn.

declhoronation sequential

As a precursor to an in-situ stimulation of the natural biodegradation potential, Uwe Schneidewind and his colleagues from VITO evaluated the dechlorination reaction occurring at an aquifer contaminated with TCE and its daughter products, discharging into the Zenne River, Belgium, in their article titled “Kinetics of dechlorination by dehalococcoides mccartyi using different carbon sources”.

Sediment material was collected from three locations of the aquifer as well as from the riverbed and used in microcosm studies (measurement of microbial activity). The growth of the microbial community was stimulated by using different carbon sources (i.e. external supply of energy in the form of food) such as lactate (C3H6O3) or molasses (C6H12NNaO3S) and the dechlorination reaction in each microcosm was monitored. Afterwards, the observed reactions were modelled using first order, Michaelis-Menten and Monod kinetics.

Reductive dechlorination of TCE took place only when external carbon sources were added to microcosms, and occurred concomitant with a pronounced increase in the Dehalococcoides mccartyi cell count as determined by 16S rRNA gene-targeted qPCR (i.e. growth measurements and bioremediation monitoring method). This indicates that native dechlorinating bacteria are present in the aquifer of the Zenne site and that the oligotrophic nature of the aquifer prevents a complete degradation to ethene. The type of carbon source, the cell number of D. mccartyi or the reductive dehalogenase genes, however, did not unequivocally explain the observed differences in degradation rates or the extent of dechlorination. Results point to the role of the supporting microbial community but it remains to be verified how the complexity of the microbial (inter)actions should be represented in a model framework.

ResearchBlogging.org

Schneidewind, U., Haest, P., Atashgahi, S., Maphosa, F., Hamonts, K., Maesen, M., Calderer, M., Seuntjens, P., Smidt, H., Springael, D., & Dejonghe, W. (2014). Kinetics of dechlorination by Dehalococcoides mccartyi using different carbon sources Journal of Contaminant Hydrology, 157, 25-36 DOI: 10.1016/j.jconhyd.2013.10.006

Soil health, is it ok?

People used to think that the soil is something that doesn’t need care … but the reality is complete opposite. The overuse of pesticides, insecticides and the pollution that is caused on a daily basis by the uncontrolled dumping, the chemical industry spills, etc. affect our environment, our soil and obviously our health.

If we mapped out a map of the subsurface we would be able to understand its complexity and how important is its preservation. The soil acts as a natural filter, soil minerals, organic matter and multitude of soil organisms are part of its structure. Soil can degrade and detoxify organic and inorganic harmful substance that enters soil with industrial and municipal by-products or through atmospheric deposition. Soil can absorb contaminants from water, air and through their incorporation by humans. Some of these compounds are then degraded by microorganisms in the soil. But… when the soil sorption system is overloaded some contaminants can be released and when their concentrations exceed the quality standards, the soil is renamed as a “contaminated site”.

In order to establish the magnitude of this problem and define the actions to be undertaken it is necessary to diagnose its quality and the risk posed for human health. This risk will depend on their who’s?? exposure to existing sources. These ways of exposure may be through direct inhalation, direct contact, and consumption of vegetables, meat or water affected by pollutants.

Ways of exposure to pollution sources

For years, progress in the diagnostic and remediation technologies has been made giving the immense biography that we can find throughout the science library.  From the ADVOCATE project, we invite you to visit our webpage (theadvocateproject.eu), know more about our research topic and the outcomes that are being achieved. Our aim is to develop innovative in-situ approaches for sustainable management and remediation of soil and groundwater contamination.

For further information about this topic, take look at this article:

http://ec.europa.eu/environment/integration/research/newsalert/pdf/IR5.pdf

What a Marie Curie Fellow does?

Link

Lukasz’s topic within the ADVOCATE project is about “Microbial dynamics and biodegradation at the bioreactive fringe of contaminant plumes in groundwater”, difficult to understand, isn’t it? Lukasz shows us what he does by means of a simple and easy understood video. Don’t miss it!

Finding a friendly environmental technology providing effective and low-cost treatment for soils contaminated by PAHs. Part (I)

Contaminated soils show high concentrations of chemicals or other substances deriving from man’s use of the land. Soil contaminants can influence human health, surface and groundwater quality and the nature and viability of ecosystems. Therefore, government, industry, and the public now recognize the potential risks that complex chemical mixtures such as total petroleum hydrocarbons (TPH), polychloro biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), heavy metals, and pesticides pose to human health and the environment. Approximately 300 000 sites across Europe are estimated to be contaminated by past and present human activities. As a consequence, in response to a growing need to address environmental contamination, many remediation technologies have been developed to treat soil, leachate, wastewater, and groundwater.

Polycyclic Aromatic Hydrocarbons or Polynuclear Aromatic Hydrocarbons (PAHs) are chemical compounds made up of two or more fused aromatic rings in a linear or clustered arrangement (see figure below). They are produced through incomplete combustion and pyrolysis of organic matter. Both natural and anthropogenic sources such as forest fires, volcanic eruptions, vehicular emissions, residential wood burning, petroleum catalytic cracking and industrial combustion of fossil fuels contribute to the release of PAHs to the environment. However, spills of petroleum hydrocarbons were more common in the last few decades than nowadays. Their distinguishing feature is that they are highly hydrophobic. PAHs are easily adsorbed onto the organic matter of solid particles being catalogued as persistent micropollutants. Hydrocarbon spillage onto soils is a matter of concern. PAHs can be removed by natural remediation processes such as photo-oxidation, evaporation, dissolution or biodegradation. Alternatively, they can be sequestered within the soil’s mineral and organic matter structures. Significant amounts of contaminants are retained in soils. Degradation of contaminants shows an initial fast period which decreases with time. According to contaminant sequestration hypothesis, contaminants become less extractable and less bioavailable by sequestration within the soil matrix during aging. However, in general, three and four ring-PAH compounds show more bioavailability than five and six rings-PAHs. The latter compounds are strongly adsorbed into the microporous structure of particulates. Based on these hypotheses three- and four-ring PAH contaminated soils would pose a greater risk to the environment.

PAHs

It is very difficult to find an efficient method of soil cleanup. Conventional remediation technologies, such as soil vapour extraction or bioventing, require years to produce concentration reductions of 50 to 90 percent, depending on soil type and volatility or biodegradability of the contaminants. Meanwhile, biodegradation is limited by low mass transfer rates in the soil matrix. In general, the time scale involved is relatively large, and the residual contaminant level achievable may not be always appropriate. Less conventional technologies such as chemical oxidation, CO2-based processes, wet air oxidation and direct oxidation processes by means of novel oxidizing agents are promising techniques to increase the degradation rate of hydrocarbons in soils. The most significant advantages are the fast treatment period and the ability to treat contaminants present at high concentrations.

Here goes a brief description about them !

Fenton’s treatment

What is Fenton reagent? Fenton’s reagent is a solution of hydrogen peroxide and an iron catalyst that is used to oxidize contaminants. It was developed in the 1890s by Henry John Horstman Fenton.

Ferrous Iron(II) is oxidized by hydrogen peroxide to ferric iron(III), a hydroxyl radical, and a hydroxyl anion. Iron(III) is then reduced back to iron(II), a superoxide radical, and a proton by the same hydrogen peroxide. The net effect is a disproportionation of hydrogen peroxide to create two different oxygen-radical species, with water (H+ + OH–) as a byproduct.

 Fe2+ + H2O2 +H+ → Fe3+ + HO + H2O

Fe3+ + H2O2 → Fe2+ + HOO+ H+

Even after over 100 years of study and use in water treatment, in-situ remediation methods were slow to use Fenton’s Reagent, owing to safety concerns. Remediation of soil and groundwater contamination is accomplished by injecting this strong chemical oxidant, and a chain reaction is initiated, forming more radicals, which are very reactive and destroy chemical bonds of organic compounds. In addition, pH adjustment using a strong acid such as sulfuric acid (H2SO4) or hydrochloric acid (HCl), is common since reactions of classic Fenton’s Reagent are more rapid and efficient under low pH conditions (pH 2 to 4 is optimal).

Ozone

Ozone is defined as a triatomic molecule, consisting of three oxygen atoms, and it is formed from dioxygen by the action of ultraviolet light.

Among the technologies that can be applied “in situ” or “on site” soil ozone application is catalogued as one of the most promising systems. Molecular ozone (or its primary decomposition radical HO) steadily reacts with a high number of organic and inorganic contaminants. Injected ozone gas might directly attack target compounds, or alternatively, it can decompose over metal oxides in the surface soil to generate the non-specific hydroxyl radical which in turn can oxidise/mineralize adjacent sorbed pollutants. The efficiency of ozone in soil treatment has been assessed either at laboratory level and field scale.

Its key benefits as an oxidant in soil and groundwater remediation are: destruction of targeted pollutants; rapid reaction – process allows for a quick turnaround; contaminants are destroyed rather than transferred from one phase to another; clean reaction – no hazardous by-products produced; and micro-bubbles act to extract pollutants from both groundwater and soil pores, so acting across the total soil body.

 Supercritical CO2, green solvent for the 21st century

Supercritical fluids (SCFs), in particular supercritical carbon dioxide, are progressively deserving the epithet of “green solvents for the 21st century”. SCFs offer properties that are intermediate between liquids and gases.

Carbon dioxide usually behaves as a gas in air at standard temperature and pressure (STP), or as a solid called dry ice when frozen. If the temperature and pressure are both increased from STP to be at or above the critical point for carbon dioxide, it can adopt properties midway between a gas and a liquid. More specifically, it behaves as a supercritical fluid above its critical temperature (304.25 K) and critical pressure (72.9 atm or 7.39 MPa). Its properties can be summarized in lower viscosity and thermal conductivity than in liquids and better diffusion characteristics.  Carbon dioxide does not require an excessive amount of energy to get supercritical conditions. As well, other advantages include the low cost of the carbon dioxide, high chemical stability and lack of toxicity.

All of these properties make supercritical CO2 an important commercial and industrial solvent due to its role in chemical extraction in addition to its low toxicity and environmental impact. The relatively low temperature of the process and the stability of CO2 also allow most compounds to be extracted with little damage or denaturing. So, the use of supercritical CO2 in soil remediation processes is recently being considered. The advantages of using CO2 include the affinity for non-polar contaminants that are tightly adsorbed into solid particulates.

ResearchBlogging.org

Rivas FJ, García R, García-Araya JF, & Gimeno O (2008). Promoted wet air oxidation of polynuclear aromatic hydrocarbons. Journal of hazardous materials, 153 (1-2), 792-8 PMID: 17945415

Can carbon and chlorine stable isotope (δ13C – δ37Cl) act as indicators of treatment performance for groundwater remediation?

First of all, we need to understand what an isotope is. Easy answer? Let us give it a try… the atoms of a particular element must have the same number of protons and electrons, but they can have a different number of neutrons. When atoms differ only in the number of neutrons, they are referred to as isotopes of each other. In addition, if a particular isotope is not radioactive, it is called a stable isotope.

The key issue that we need to provide an answer for is how the isotopes may act as indicators of treatment efficiency and performance for natural biological processes such as bioremediation or natural attenuation, which can remove organic contaminants in the environment. What is helpful is that when organic contaminants are degraded in the environment, the ratio of stable isotopes will change, and the extent of degradation can be recognized and predicted from the change in the ratio of the stable isotopes. Recent advances in analytical chemistry make it possible to perform Compound Specific Isotope Analysis (CSIA) on dissolved organic contaminants such as chlorinated solvents, aromatic petroleum hydrocarbons, fuel oxygenates and many other organic chemicals, at concentrations in water that are near their regulatory standards.

Once we understood this, we can go one step further, and approach the research topic of Alice Badin, a Marie Curie Fellow in the ADVOCATE network. Alice is working at the University of Neuchatel in Switzerland. Her research looks at the variability of carbon and stables isotope ratios in chlorinated ethenes, which are common groundwater contaminants, for various applications such as source identification and characterisation of biodegradation. The isotopic signature measurement of such solvents might be a great help in providing a rigorous basis to identify the source, timing and fate of chemicals released to soil and groundwater.

According to a previous research, the isotopic signatures (i.e. combination of isotopic ratios of chlorine, noted δ37Cl and carbon, noted δ13C in the solvent molecule) of pure compounds from different manufacturers were measured, it could be observed that the signatures varied depending on the manufacturer. Hence, in the field, neighbour spills might have different signatures, so when we don’t know which spill is responsible for further downstream contamination, a comparison between the downstream signature and the suspected sources signatures might help delineating the responsible source (see drawing). However, there are few detailed case studies on the potential application, and the lack of signature variability at a country scale might be a brake to its use. This is the key reason why Alice’s research is partly evaluating the variability in stable isotopic signature of these organic chemicals in Switzerland.

Scheme 1

Based on this, Alice first completed field studies where she measured the isotopic signature of tetrachloroethene (PCE) at 10 different contaminated sites in Switzerland.

molecure

Tetrachloroethene (PCE)

The question that Alice had to contend with was: “Do sites contaminated with PCE in Switzerland have similar stable isotopic signatures?” Although the sites were distributed throughout the country and represented different industrial activities, the PCE examined had very similar isotopic signatures. This thus limits the use of isotopic signature measurement for PCE source delineation in Switzerland. On the other hand, an average value of the stable isotopic signatures determined in these sites could represent a starting point for the assessment of PCE biodegradation at contaminated sites in Switzerland.

The next step in Alice’s research was to assess the relationship between the δ13C and δ37Cl composition of chlorinated ethenes during PCE biodegradation, as this can further help assessing the extent of biodegradation in the field (see multistep biodegradation chain) Currently, the interpretation of this compound specific isotope data set is challenged by a shortage of experimental Cl isotope enrichment factors. Here, isotope enrichments factors for C and Cl were determined in the lab for biodegradation of PCE to TCE, using microbial enrichment cultures originating from an aquifer contaminated with chlorinated ethenes, which contains members of the bacterial genus Sulfurospirillum.

scheme 2

Multistep biodegradation: the most toxic compound vinyl chloride can eventually be degraded into not harmful ethene or inorganic carbon

These lab experiments are also intended to help understanding better the mechanisms involved during degradation by looking at trends in the stable isotopic ratios. The aim is to relate these changes to some possible degradation pathways or mechanisms, but this part is still under discussion.

After a painstaking and extensive study, Alice recently presented her results at the Isotopes 2013 conference in Sopot (Poland) under the heading “Carbon and chlorine isotopic trend in fingerprinting and anaerobic dechlorination of tetrachloroethene”

 

ResearchBlogging.org

Badin A, Buttet G, Maillard J, Holliger C, & Hunkeler D (2014). Multiple dual C-Cl isotope patterns associated with reductive dechlorination of tetrachloroethene. Environmental science & technology, 48 (16), 9179-86 PMID: 25000152

The installation of the Vadose Monitoring System (VMS) was carried out successfully in Belgium last June

The installation of the Vadose Monitoring System (VMS) was carried out successfully in Belgium last June

I am pleased to announce that Natalia Fernandez together with her research group, HGeo³-Hydrogéologie et Géologie de l’Environnement, proceeded with the installation of the Vadose Monitoring System (VMS) in Belgium in June. The objective is to develop a methodology that is able to quantify contaminant fluxes, identify their sources and pathways and understand the various reactive processes in soil and groundwater.

The combined experiment consisted of a tracer test performed directly in the vadose zone via infiltration rings, located within an infiltration pond. To do this, a flexible sleeve was installed in a slanted borehole with the aim of capturing a tracer infiltrated throughout undisturbed material above the borehole. To measure water content, Flexible Time Domain Reflectometry probes (FTDR), which contain stainless steel waveguides, were installed in the outer wall of the flexible sleeve. As well, Vadose Sampling Ports (VSP) were placed in the inner wall of the flexible sleeve for sampling pore water in the vadose zone. Finally, additional boreholes were installed in the unsaturated zone to conduct cross-hole geophysics with the aim of monitoring contaminants and tracers as they move into the saturated zone (see it in the pictures).

The outlook of this experiment is to use the advantages of the combination of the Vadose Monitoring System and geophysical techniques with the aim of developing a conceptual model that better characterizes the transport of pollutants in the vadose zone of industrial sites. The objective is to use such a methodology as an approach to improve risk assessment and remediation measures for the vadose zone.

Natalia experiment 0 Natalia experiment 1Natalia experiment 2  Natalia experiment 2b Natalia experiment 3aNatalia experiment 3bNatalia experiment 4aNatalia experiment 4b   Natalia experiment 5

How much impact has climate change on contaminated land and pollutants?

How much impact has climate change on contaminated land and pollutants? 

How much impact has climate change on contaminated land and pollutants is an excellent question with a blank answer currently. The impact of climate change factors on the risk assessment, design of future remediation systems and management of current and future contaminated sites will be likely a key point that we should take into account or consider.

On the one hand, sustainability indicators in terms of environmental, economic and social are the basis for the sustainable remediation assessment of contaminated soils and groundwater. In this way, the UK Sustainable Remediation Forum (SuRF-UK) has developed a framework for assessing their sustainability, and for incorporating sustainable development criteria in land contamination management strategies, setting up in this sense a series of sustainability indicators for their remediation. These indicators are indicative of the range of issues that may be relevant, and are provided to help assessors identify the most critical issues to evaluate further in a project. As well, they highlight which are the challenges at global, national or local level.

On the other hand, in readiness for our future climate and its changes, there is a need to evaluate the risks of climate change and to predict how it is going to affect our future. In this way, some European projects have tried to give a response since 2000. PRUDENCE, Prediction of Regional scenarios and Uncertainties for Defining EuropeaN Climate change risks and Effects, was a European scale investigation project which aimed to quantify the confidence and the uncertainties in predictions of future climate and its impacts, using an array of climate models and impact models and expert judgement on their performance. Continuing the theme of this investigation, the project ENSEMBLES was carried out, based on Predictions of Climate Changes and their Impacts. This project aimed to build a common ensemble climate forecast system which would be developed for use across a range of timescales (seasonal, decadal and longer) and spatial scales (global, regional and local). So, this model system would be used to construct integrated scenarios of future climate change, including both non-intervention and stabilisation scenarios. ENSEMBLES ended in 2009 and immediately a new major project was started up, CORDEX, COordinated Regional climate Downscaling Experiment, which is an international project to produce an improved generation of regional climate change projections world-wide for input into impact and adaptation studies.

All this effort provides us a quantitative risk assessment of climate change and climate variability. On this basis, the next step would be to quantify the impact of climate change on contaminated land and to examine technical evidence of this impact and potential technical adaptation strategies that should be followed.

Although, all projects identified in this document have done extremely respectable and useful work, there is currently very little published work providing experimental evidence of potential direct impacts of climate change on contaminated land and remediation systems. The closest work is that which investigates and compares the impacts of different climatic regions on biological and chemical properties of contaminated soils and contaminant behaviour. Consequently there is a need for effort in this area to ensure that remediation choices being made now are the right ones by future land use, climatic conditions and societal demographics. 

So, in the United Kingdom, in 2007, a multi-institutional and multi-disciplinary research consortium was involved in a project called SUBR:IM, Sustainable Urban Brownfield Regeneration: Integrated Management, whose aim was producing integrated and sustainable solutions for the development of brownfield land in urban areas. They concluded that from the evidence available in the literature and collected as part of the study, it is clear that certain climate change scenarios are expected to have significant impacts on current and future contaminated land and remediation systems. These impacts will have major effects on the future management of contaminated and remediated sites and are expected to influence the way risk is managed on those sites and the design of future remediation strategies. 

However, this project is only the beginning of an emerging area of research. We still have a long way to go. It is important to set up a good correlation between the climate change and the current soil remediation technologies so that their implementation will not be a complete waste of time in the future when the environmental conditions change, in particular, those systems that required long time scales.