LCA and contaminated sites | EPFL Graph Search

Life cycle assessment (LCA) is a tool for assessing the environmental impact of services or products. This project wants to explore the potential contribution of LCA for contaminated site management, via the comparison of several remediation strategies (excavation, phytoremediation and “do nothing” options) for soils contaminated by heavy metals. The study aims at identifying the main methodological gaps in modelling impacts at midpoint and endpoint levels and providing insights for filling in these gaps. In particular, emphasis is put on the impact of the site itself on the surrounding environment compared to remediation options. Excavation resulted to have the greater impact on the human health, while it is the smallest for the water ecosystem. Temporal and spatial dimension play a role in the evaluation of the damage. The results given by global and regional IMPACT2002 model are compared, and their allocation in short-term and long-term periods is shown with the introduction of the Stored Additional Impact (SAI), which goal is to help the comprehension of the outcome. The most important missing information in the method is the evaluation of the pollution impact on the contaminated site itself and its ecological and economical value after the management. To do this the combination of Ecological Risk Assessment (ERA) and LCA is suggested. The conclusion is that LCA can bring additional information that contribute to the decision making process of site management. In particular, the “do nothing” scenario serves as a reference impact and helps deducing the real efficiency and utility of the other remediation processes.

Analysis of microbial community structures and functions in heavy metal-contaminated soils using molecular methods

Fabienne Gremion

The contamination of agricultural land and groundwater by heavy metals is essentially linked to human activities. A major problem with heavy metals is that they cannot be biodegraded and therefore reside in the environment for long periods of time if they are not removed. Thus, depending of the kind and depth of contamination, different remediation techniques were developed. One of these methods, called "phytoextraction", uses the ability of so-called hyperaccumulating plants to extract high amounts of heavy metals. Accumulation of heavy metals in the environment is a serious concern for animal and human health. At the microscopic scale, heavy metals may have also deleterious effects on bacteria which are the key-players of the different nutrient turnovers in soils. Consequently, ecosystem functioning can be seriously perturbed and the long-term soil fertility may be threatened. The recent development of molecular biology greatly contributed to the discovery of the microbial diversity and its function in the soil. However, to date only a small number of studies used molecular methods to investigate the impacts of heavy metals on the bacterial community. In this thesis, a pot experiment was conducted under controlled conditions with one hyperaccumulating plant (Thlaspi caerulescens) grown in two different soils, a long-term and an artificially heavy metal-contaminated soil. The impact of heavy metals on the microbial community was then investigated with several molecular methods. Moreover, the decrease of the bioavailable heavy metals concentrations in soil due to plant uptake allowed to study the consequences on bacterial community structure and function. Based on the 16S ribosomal RNA and the corresponding gene (16S rDNA), four clone libraries were constructed to retrieve information on the structure of the microbial community and the potentially active part of the microbial community in the rhizosphere of Thlaspi caerulescens grown during three months in a long-term contaminated soil. The data obtained with the two clone libraries (rRNA and rDNA) from the rhizosphere of Thlaspi caerulescens were compared with the bulk soil data to identify any effect of the plant on the soil microbial community structure. Partial sequence analysis of 282 clones revealed that most of the environmental sequences in both soils affiliated with five major phylogenetic groups, the Actinobacteria, α-Proteobacteria, β-Proteobacteria, Acidobacteria and the Planctomycetales. The taxa dominating the bacterial community structure in the bulk soil also dominated the rhizosphere community, indicating that the plant did not exert a major influence on the overall bacterial diversity. However, all dominant taxa, with the exception of the Actinobacteria, were relatively less represented in the rRNA libraries as compared to the rDNA libraries. On the contrary, sequences belonging to the Actinobacteria dominated both bulk and rhizosphere soil libraries derived from rRNA. Seventy per cent of these clone sequences were related to two subgroups of the Rubrobacteria, which was an indication that this group of bacteria was probably metabolically active in heavy metal-contaminated soils. Fluorescence in situ hybridization (FISH) was used for the in situ detection and quantification of selected bacterial groups previously detected in the clone libraries from the rhizosphere of Thlaspi caerulescens. By applying the most general probe EUB338, only 20% of the total rhizosphere microbial community could be detected. Based on this result, it was difficult to conclude with certitude which were the most dominant bacteria in the rhizosphere. However, despite this low detection rate, it was possible to detect the major groups present in the rhizosphere clone libraries using group-specific oligonucleotide probes. As part of our sequences were affiliated to two emerging bacterial groups, the Acidobacteria and the Rubrobacteria, two new probes were designed, Acido228 (specific for the subgroup 1 of the Acidobacterium division) and Rubro198 (specific for the all Rubrobacteria subclass), for the detection of these microorganisms. These two probes were first checked for their specificity with pure cultures and finally applied in the rhizosphere soil allowing for the first time the detection of these organisms in situ. Finally, the impact of heavy metals and a subsequent one-year phytoextraction with Thlaspi caerulescens on the soil microbial community was investigated in an artificially heavy metal-contaminated soil. All the different molecular and culture-dependent techniques used, denaturing gradient gel electrophoresis (DGGE), community level physiological profile (CLPP) and potential ammonium-oxidation measurement showed that the heavy metal addition induced drastic changes in the bacterial community. Moreover, the analysis of the different bacterial DGGE patterns (Bacteria, β-Proteobacteria and ammonia-oxidising bacteria) obtained during this experiment showed that one-year phytoremediation was not sufficient to recover the initial community present in the non-contaminated soil. However, with the CLPP analysis, it was possible to detect a stimulating effect of the plant on a part of the microbial community in both contaminated and non-contaminated soils. The most obvious result was obtained in the contaminated soil where the number of substrates metabolised increased significantly in the presence of the plant as compared to the unplanted contaminated samples. The measurement of the potential ammonium-oxidation was used as a criterion for soil quality. Although this test showed that the ammonia-oxidising bacteria were significantly stimulated in the planted non-contaminated soil samples, the positive effect of the plant on these bacteria was not sufficient to overcome the inhibition induced by the presence of the heavy metals in the contaminated soil, even after one year phytoremediation. To conclude, molecular methods in combination with culture-dependent techniques have proven in this study to be very useful for the detection of the changes induced by the heavy metals in the structure and the function of the microbial community. Moreover, the molecular techniques contributed to the identification of bacteria which could be potentially used for the bioremediation of contaminated soils thus offering new perspectives of investigation and technology development.

EPFL2003

Assessing toxic impacts on aquatic ecosystems in life cycle assessment (LCA)

Jérôme Payet

In the last decade, several Life Cycle Assessment (LCA) methods for assessing impact of products on living resources have been developed. Beyond the quantified assessments of impacts on living systems, it also checked the feasibility of the impact assessment on human health and ecosystems quality and helps to identify the limits of such methods. Among the different impact categories, that of toxic substances on ecosystems occupies an important place. The extent of these impacts has been stressed on many occasions and the necessity of preserving ecological areas and biodiversity has become a major issue on an international level. By focusing on aquatic ecosystems, this thesis aims at identifying constraints connected with assessment of the impact of chemical substances on ecosystems in LCA and setting up a method for assessing impacts of toxic substances on aquatic ecosystems which meets the requirements of a comparative approach like Life Cycle Assessment. The overall purpose of the thesis is to propose a comparative method for the Life Cycle Impact Assessment of toxics on aquatic ecosystems. With that aim, the dissertation is going throughout 6 major issues: The feasibility of the comparative impact assessment on ecosystems and the identification of associated constraints. The development of a statistical method for comparing impact on ecosystems; The review of the data availability for calculation of Effect Factors. The choice of the most relevant ecotoxicity measure (ECxs1, NOECs2 and LOECs3) for a comparative purpose. The development of best-estimate extrapolation factors for assessing chronic effects based on acute data. The analysis of the ecological realism of the comparative assessment method. These points are analysed throughout the 7 chapters of the thesis. Chapter 1 aims at introducing the thesis. A general presentation of Life Cycle Assessment is proposed, following by a detailed description of the Life Cycle Impact Assessment on ecosystems. This description covers the state of the art of researches and identifies the development needed. Therefore the scope of the thesis and the main points that must be addressed by this research are presented. Chapter 2 starts with a review of existing methods for Life Cycle Impact Assessment on ecosystems (LCIA), the chapter presents the parametric version of the AMI method (Assessment of the Mean Impact), which has been developed during the PhD for the assessment of impact on aquatic ecosystems. For this purpose, a framework and the main requirements for the development of this method are presented. For a comparative assessment, the Hazardous Concentration of a toxic affecting 50% of the species over their chronic EC50 (Effect Concentration affecting 50% of tested individuals), also called HC50EC50, is selected for the calculation of Effect Factors to be implemented in current LCIA methods. The Confidence Interval on the HC50EC50 is provided, enabling comparison between the impact values obtained as results of a Life Cycle Assessment study. The choice of EC50s is based on review of the main ecotoxicological databases, and analysis of the availability and reliability of test results. Moreover, bearing in mind that mostly acute data are available, while LCA deals mainly with chronic exposure, best-estimate extrapolation factors for the HC50EC50 and the associated uncertainty are provided for inorganics, nonpesticide organics, and pesticide organics. Concerning the method itself, in order to find the best methods for calculation of a toxicity indicator, several statistical estimators, parametric and non-parametric approaches are compared, identifying their properties and respective strengths for a comparative method. The analysis relates to both the reliability of the estimator and its Confidence Interval, especially in terms of statistical robustness and Effect Factor stability. Based on these findings, the AMI method is described in detail, and an example of application comparing two wheat crop scenarios differing by the pesticides used is presented. Chapter 3 presents in detail the four methods currently used for the development of Effect Factors for the Life Cycle Impact Assessment (LCIA) on Ecosystems: the parametric version of AMI (Assessment of the Mean Impact) based on HC50EC50s; the Eco-Indicator based on HC50NOECs; USES-LCA based on both HC5NOECs and the Most sensitive species, and the PNEC (Predicted No- Effect Concentration) based on the Most sensitive species. After presentation of the LCIA framework and its main divergences from Environmental Risk Assessment for chemical regulation, the four methods are detailed and applied for the calculation of Effect Factors for 83 substances, covering inorganics, non-pesticide organics, and pesticide organics. Each method is therefore analysed concerning three key points: applicability in the LCA framework, environmental relevance, and statistical reliability. Particular attention is paid to possible bias and the uncertainty, highlighting the following findings: (1) HC5NOECs are on average 50 times higher than the most sensitive species, and this difference in conservatism introduces a bias in the analyses for the method mixing HC5NOECs and most sensitive species. (2) Effect Factors based on the most sensitive species increase the relative weight of the most toxic chemicals by two orders of magnitude, depending on whether the study is based on US or European ecotoxicity databases. (3) the methods based on HC50EC50s and HC5NOECs are the only ones able to provide a Confidence Interval on the Effect Factor, but the Confidence Interval on the HC5NOECs can be more than 10 orders of magnitude greater than that of the HC50EC50s. (4) compared with the Confidence Interval on the HC50EC50s, the most sensitive species cannot be distinguished from HC50EC50s for chemicals characterised by fewer than 5 species, and the HC5NOECs cannot be distinguished from the HC50EC50s for chemicals characterised by fewer than 8 species. Chapter 4 compares two statistical estimators, aiming at calculate the average toxicity of substances on biological species. The two methods provide an estimation of the HC50EC50 and the associated Confidence Interval. On the one hand, parametric method using the geometric mean and a calculation of the confidence interval with Student is considered. On the other hand, a distribution-free method calculates the HC50EC50 based on the median response of species and the confidence interval based on bootstrap. In order to facilitate the use of the non-parametric method, a table linking the number of species tested and the size of the confidence interval is provided for samples from 5 to 500 species. The comparison is based on actual data concerning 191 substances covering inorganics, non-Pesticide organics, and Pesticide organics. The mean and width of the chronic EC50s samples for all the substances are presented. The Shapiro-Wilk test is performed for the 191 EC50s samples and the assumption of log-normality of the distribution failed in more than 20% of the cases. Two causes of this non Log-normality are identified; (1) the skewness, which is shown to be an important issue for the assessment of the average toxicity of chemicals while (2) the multi-modal distributions, which are not likely to influence considerably the final result. A detailed application of the two methods is done with the comparison of two herbicides, the Sulfosulfuron and the Prosulfuron, where the distribution-free method appears to be more powerful than the parametric for a substance-to-substance comparison. Nevertheless, the distribution-free method requires a minimum of 5 chronic EC50s, that cannot be satisfied in most cases. Chapter 5 aims at illustrating the previous chapter in using the nonparametric version of the AMI method for the comparative assessment of the impacts of metals on aquatic ecosystems. This chapter briefly describes the method, then it focuses on the comparative analysis of 9 metals sometimes tested with different salts and speciations. Two interesting results can be highlighted: (1) the toxicity of metals covers the whole range of toxicity of chemicals; (2) the confidence interval of the HC50EC50 for metals is on average twice as great for metals compared with other chemicals. This increase in the variability of ecotoxicological responses from species is likely to be due to the change in bioavailability of metals associated with a change of test conditions (e.g. pH, or Organic Matter). Chapter 6 reviews and analyses the reliability of existing aquatic toxicity databases which can be used for the calculation of Effect Factors for Life Cycle Impact Assessment (LCIA). For that purpose, the main LCIA methods are presented focusing on their data requirement. It concerns: EDIP4 (based on the PNEC); AMI5 (based on parametric HC50EC50); Eco-Indicator (based on the HC50NOEC); USES-LCA (based on the HC5NOEC). Moreover 6 ecotoxicity databases available in an electronic format are analysed: Aquire; Pesticide Ecotoxicity Database (PED); IUCLID; Acute Toxicity Database (ATD); Fathead Minnow database (FMD); and ECETOC Aquatic Toxicity Database (EAT). The analysis especially focuses on the identification of the substances and organisms, the definition of the tests conditions, and the control procedure of the database. A selection of tests is done, retaining a dataset of 128,864 tests results, acute, sub-chronic and chronic. A description of the data availability on the basis of the selected test is performed, considering the available EC50s (Effect Concentration affecting 50% of the individuals tested), LOECs and NOECs (Lowest or No Observed Effect Concentration). The number of covered substances is also analysed regarding the number of species or phyla considered. On that basis, an estimation of the maximum number of possible Effect Factors is performed. The results highlight the discrepancy between the large number of test results available (128,864), and the relatively restricted number of Effect Factors (betweeen 34 and 4959 depending on the method)) that can be calculated for a comparative purpose like LCIA. Chapter 7 provides a conclusion to the work, answering the points underlined in introduction. Then, the fey features of the AMI method are restated and the perspectives and output of the work are presented. In the last part of the thesis, the AMI HC50EC50 database is presented. It provides acute and chronic HC50EC50 data calculated with the parametric version of AMI (geometric mean of the EC50s and confidence interval based on Student) for 522 susbtances. ------------------------------ 1 ECx: concentration of susbtance that affects 50% of the individuals tested for a given effect. 2 NOEC: No Observable Effect Concentration 3 LOEC: Lowest Observable Effect Concentration 4 EDIP: Environmental Design for Industrial Product 5 AMI : Assessment of the Mean Impact

EPFL2004

Life cycle environmental assessment of retaining walls in unsaturated soils

Alessio Ferrari, Gianluca Speranza

Retaining structures above groundwater level support soils that are usually in a state of partial saturation and subject to the actions of atmospheric agents. The current design approach considers the possible extremes of soil conditions - either totally dry or totally saturated - but it neglects matric suction's contribution to soil shear strength. This work aims to describe how unsaturated-soil mechanics of can positively influence the sustainability of retaining structures through a holistic, multidisciplinary, geotechnical, and environmental analysis. The geotechnical analysis allows to estimate the lateral earth pressure of a geostructure in both unsaturated and extreme soil conditions (dry or saturated), which will directly influence the geometrical dimensions of the geostructure. Next, the environmental analysis is performed with the standardized and globally applied Life Cycle Assessment (LCA) tool, in order to quantify the potential environmental impacts of the retaining structure according to both a life cycle and a multi-criteria perspective. First, an LCA model is built for a cantilever retaining wall according to two design approaches: (a) an unsaturated design approach (UDA), i.e. when unsaturated soils' principles are considered in the design procedure, and (b) a conventional design approach (CDA), i.e. if soil is considered dry or saturated. Three different types of retained soil (i.e. fine-grained soil, volcanic ash, and coarse-grained soil) are considered. Then, the associated environmental impacts on climate change, human health, ecosystems and resources are calculated for the two design approaches. Their comparison allows to quantify the potential reductions in environmental damages provided by the adoption of unsaturated-soil mechanics. The presented case study shows a high potential reduction in environmental impacts for retaining walls interacting with fine-grained soils (silt), lower potential environmental benefits with volcanic ash (clayey-silty sand), but no environmental gain for interaction with a coarse-grained soil (sand) compared to a conventional design approach considering extreme soil conditions. (c) 2021 Elsevier Ltd. All rights reserved.

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