A large number of hazardous compounds can be expected to be present in landfill leachates, many o... more A large number of hazardous compounds can be expected to be present in landfill leachates, many of which have not yet been identified. Thus this study screened samples from 12 Swedish municipal landfill sites for 400 parameters and compounds. More than 90 organic and metal organic compounds and 50 inorganic elements were detected, some of which seem to have not been detected before. Compounds detected include halogenated aliphatic compounds, benzene and alkylated benzenes, phenol and alkylated phenols, ethoxylates, polycyclic aromatic compounds, phthalic esters, chlorinated benzenes, chlorinated phenols, PCB, chlorinated dioxins and chlorinated furans, bromated flame-retardants, pesticides, organic tin, methyl mercury and heavy metals. The presence of this large number of hazardous compounds in landfill leachates should have a significant impact on future landfill risk assessments and the development of leachate treatment methods. We propose that future research should pay more atte...
An experimental system for simulating and analysing the fate of organic compounds in landfill-lik... more An experimental system for simulating and analysing the fate of organic compounds in landfill-like environments has been developed. The performance of the system was investigated by using 11 volatile organic compounds which have previously been identified in landfill leachates. The compounds represented a range of hydrophobicity and the limits of quantification were at μg/1-levels similar to that in actual landfill leachates. The automatised system consisted of a reservoir without headspace for storing the water solutions of the volatile test compounds, a reactor for studying the landfill processes, a pump, a Purge and Trap concentrator, a gas chromatograph (equipped with flame ionisation and electron capture detectors), and a computer for data collection.
The presence of hazardous compounds in waste presents ahazard to the environment both in the shor... more The presence of hazardous compounds in waste presents ahazard to the environment both in the short term and the longterm perspective. Landfills containing organic waste canassimilate certain levels of hazardous organic compounds sincethey offer a potential for retention and possibly degradationof organic constituents during events which occur in landfills.From a literature review the transitions of wastes andleachates with time have been compiled.In this thesis, specific organic compounds have beenidentified in leachates from a Swedish municipal landfill. Theresults showed considerable differences in the nature oforganic compounds identified, and the difficulty to determinethe origin of the compounds. It is not possible to analyse morethan a fraction of the organic compounds present in landfills.The organic compounds are primarily present in µg/l levelsin landfill leachates and only in exceptional cases in highconcentrations in the order of mg/l.A conceptual model was proposed including the most importantprocesses, sorption, water transport, transformation andevaporation. With this model, the physical, chemical andbiological characteristics of specific compounds werecorrelated to the emissions. Automatic experimental equipmentwas then developed with which different landfill processescould be examined at the µg/l concentration level. Thelaboratory equipment was used for determining the sorption oforganic compounds to actual waste. The time for reachingsorption equilibrium varied from hours to days, depending onthe hydrophobicities of the compounds. The sorption could bedescribed as linear, at least within limited concentrationintervals. The sorption was also found to be linearlycorrelated with the Kowof the compounds.Further the transport of organic compounds with percolatingwater through a pilot-scale landfill containing 540 m3of waste was examined. It was concluded that thewater was percolating along preferential flow paths through thelandfill, together with fractions of the added compounds.Laboratory experiments indicated that the transport of organiccompounds with mobile particles and colloids was significant.The fate of the organic compounds inside the landfill wastheoretically estimated from literature data concerningsorption, evaporation and transformation. It was concluded thata good correlation existed between the measured emissions andthe theoretically evaluated fate. It is therefore suggestedthat the emissions of organic compounds from landfills can bequalitatively predicted from literature data. Forquantitativepredictions the amount of a compound present in the landfillmust be known.Keywords: organic compounds, municipal landfills,sorption, transport, preferential flow
Forty-five organic compounds have been identified in leachates from a Swedish municipal landfill.... more Forty-five organic compounds have been identified in leachates from a Swedish municipal landfill. The samples were taken from the interior of the landfill to minimize alterations caused by contact with the surroundings and were identified and quantified by gas chromatography combined with mass spectrometry. Two analytical procedures were used, one for priority pollutants, the other for a wider range of phenolic and neutral compounds and acids. Analyses of the leachates for water quality parameters indicated that the part of the landfill which was sampled had reached an anaerobic stage in which methane was being produced. Possible origins for most of the compounds identified have been suggested.
Emissions of organic compounds from landfills depend on the fate of the compounds inside the land... more Emissions of organic compounds from landfills depend on the fate of the compounds inside the landfills. This field study was used to investigate the fate in landfills of organic compounds having different physical, chemical, and biological characteristics. For this purpose, a pilot-scale landfill was constructed containing 540 m3 of ordinary household waste, 12 organic compounds were added at the top of the landfill, and leachate and landfill gas samples were continually collected and analyzed. The fate of each compound was theoretically estimated from literature data on the processes which significantly affect the compounds: sorption, dissociation, evaporation, and transformation. These processes could be described by the octanol/water coefficients, Kow, the acid dissociation constants, pKa, the Henry's law constants, H, and the potential of the compounds to be biologically transformed. The use of a ranking score system was suggested as a tool for interpreting the predicted fate of specific compounds caused by several simultaneous processes. A good correlation could be found between the measured emissions and the theoretically evaluated fate. It was concluded that the construction of a pilot-scale landfill is a useful method for studying simultaneous processes in landfills and that the emissions of organic compounds from landfills can be qualitatively predicted from literature data.
W ithout a doubt, scientific research has contributed immensely to human progress and to the deve... more W ithout a doubt, scientific research has contributed immensely to human progress and to the development of modern society. Yet, the way in which scientific endeavors are pursued around the world is marked by clear inequalities (1). Developing countries generally spend less money on scientific research than industrialized countries (in relation to gross domestic product), and the number of scientists is smaller (in relation to population). For example, recruitment of new scientists in Africa has been very slow in the past few years. In addition, the number of Ph.D. holders of African descent who live and work outside their home countries far exceeds the total number of African-born scientists with Ph.D.s who work in Africa (2). Because of the uneven global distribution of resources needed to build and maintain scientific capacity, a large share of new research is created in industrialized countries, and much of that science neglects the problems that afflict most of the world's population (1). This unbalanced distribution generates serious problems for not only the scientific communities in the developing countries but also development itself. In addition to a critical mass of trained staff, another important factor in the technological development of a country is the availability of properly functioning scientific equipment (3). Unfortunately, many laboratories in developing countries are underequipped because of a lack of funds. Some institutions have poured their hardearned funds into buying capital equipment, only to discover that the instruments cannot be used for reasons related to installation, servicing, and maintenance. Using scientific equipment in a developing country is often surprisingly difficult because of infrastructure and climate conditions (4). Many universities and institutions have reported that maintenance and servicing are often a low priority (5-7). A 700-respondent survey conducted by Gaillard and Tullberg showed that, apart from insufficient funds, lack of access to functioning equipment was the main constraint to scientific research in Africa (8). The lack of competent technicians and support staff was identified as the fourth major problem. (The third Scientific research is the cornerstone of national growth, yet properly functioning scientific equipment cannot be taken for granted in developing countries. Scientific research is the cornerstone of national growth, yet properly functioning scientific equipment cannot be taken for granted in developing countries.
... In a parallel study, the fate of organic compounds in the landfill was determined (Öman submi... more ... In a parallel study, the fate of organic compounds in the landfill was determined (Öman submitted). ... More recent studies have also pointed out the heterogeneity of the landfilled waste and the existence of preferential flow paths (Bengtsson et al., 1994; Khanbilvardi et al., 1995 ...
It is generally accepted that scientific research offers a tool for meeting the development deman... more It is generally accepted that scientific research offers a tool for meeting the development demands in the area of water and sanitation. It is stressed by the authors that research should be performed by researchers in the countries most affected, on topics identified by these researchers and in their own environment. For researchers in developing countries the resources and scientific infrastructure constitutes a hindrance to scientific research. To address the situation this paper presents a strategy for scientific capacity strengthening. The strategy builds on a number of activities including; training courses on scientific methodology, literature review, fundraising, sampling, laboratory practices, statistical methods, experimental designs, participatory approaches, oral presentation, posters and manuscript development, as well as thematic workshops, workshop for revision of proposals, contacts with end-users, research grants, networks, purchasing and maintaining scientific equipment and scientific conferences. The strategy builds heavily on collaboration with local organisations. It has been concluded through assessments of activities arranged in Bangladesh, Benin, Burkina Faso, Cameroon, Ivory Coast, Ghana, Mali, Niger, Nigeria, Nepal, Sri Lanka and Togo that the strategy has been successful.
A large number of hazardous compounds can be expected to be present in landfill leachates, many o... more A large number of hazardous compounds can be expected to be present in landfill leachates, many of which have not yet been identified. Thus this study screened samples from 12 Swedish municipal landfill sites for 400 parameters and compounds. More than 90 organic and metal organic compounds and 50 inorganic elements were detected, some of which seem to have not been detected before. Compounds detected include halogenated aliphatic compounds, benzene and alkylated benzenes, phenol and alkylated phenols, ethoxylates, polycyclic aromatic compounds, phthalic esters, chlorinated benzenes, chlorinated phenols, PCB, chlorinated dioxins and chlorinated furans, bromated flame-retardants, pesticides, organic tin, methyl mercury and heavy metals. The presence of this large number of hazardous compounds in landfill leachates should have a significant impact on future landfill risk assessments and the development of leachate treatment methods. We propose that future research should pay more atte...
A large number of hazardous compounds can be expected to be present in landfill leachates, many o... more A large number of hazardous compounds can be expected to be present in landfill leachates, many of which have not yet been identified. Thus this study screened samples from 12 Swedish municipal landfill sites for 400 parameters and compounds. More than 90 organic and metal organic compounds and 50 inorganic elements were detected, some of which seem to have not been detected before. Compounds detected include halogenated aliphatic compounds, benzene and alkylated benzenes, phenol and alkylated phenols, ethoxylates, polycyclic aromatic compounds, phthalic esters, chlorinated benzenes, chlorinated phenols, PCB, chlorinated dioxins and chlorinated furans, bromated flame-retardants, pesticides, organic tin, methyl mercury and heavy metals. The presence of this large number of hazardous compounds in landfill leachates should have a significant impact on future landfill risk assessments and the development of leachate treatment methods. We propose that future research should pay more atte...
An experimental system for simulating and analysing the fate of organic compounds in landfill-lik... more An experimental system for simulating and analysing the fate of organic compounds in landfill-like environments has been developed. The performance of the system was investigated by using 11 volatile organic compounds which have previously been identified in landfill leachates. The compounds represented a range of hydrophobicity and the limits of quantification were at μg/1-levels similar to that in actual landfill leachates. The automatised system consisted of a reservoir without headspace for storing the water solutions of the volatile test compounds, a reactor for studying the landfill processes, a pump, a Purge and Trap concentrator, a gas chromatograph (equipped with flame ionisation and electron capture detectors), and a computer for data collection.
The presence of hazardous compounds in waste presents ahazard to the environment both in the shor... more The presence of hazardous compounds in waste presents ahazard to the environment both in the short term and the longterm perspective. Landfills containing organic waste canassimilate certain levels of hazardous organic compounds sincethey offer a potential for retention and possibly degradationof organic constituents during events which occur in landfills.From a literature review the transitions of wastes andleachates with time have been compiled.In this thesis, specific organic compounds have beenidentified in leachates from a Swedish municipal landfill. Theresults showed considerable differences in the nature oforganic compounds identified, and the difficulty to determinethe origin of the compounds. It is not possible to analyse morethan a fraction of the organic compounds present in landfills.The organic compounds are primarily present in µg/l levelsin landfill leachates and only in exceptional cases in highconcentrations in the order of mg/l.A conceptual model was proposed including the most importantprocesses, sorption, water transport, transformation andevaporation. With this model, the physical, chemical andbiological characteristics of specific compounds werecorrelated to the emissions. Automatic experimental equipmentwas then developed with which different landfill processescould be examined at the µg/l concentration level. Thelaboratory equipment was used for determining the sorption oforganic compounds to actual waste. The time for reachingsorption equilibrium varied from hours to days, depending onthe hydrophobicities of the compounds. The sorption could bedescribed as linear, at least within limited concentrationintervals. The sorption was also found to be linearlycorrelated with the Kowof the compounds.Further the transport of organic compounds with percolatingwater through a pilot-scale landfill containing 540 m3of waste was examined. It was concluded that thewater was percolating along preferential flow paths through thelandfill, together with fractions of the added compounds.Laboratory experiments indicated that the transport of organiccompounds with mobile particles and colloids was significant.The fate of the organic compounds inside the landfill wastheoretically estimated from literature data concerningsorption, evaporation and transformation. It was concluded thata good correlation existed between the measured emissions andthe theoretically evaluated fate. It is therefore suggestedthat the emissions of organic compounds from landfills can bequalitatively predicted from literature data. Forquantitativepredictions the amount of a compound present in the landfillmust be known.Keywords: organic compounds, municipal landfills,sorption, transport, preferential flow
Forty-five organic compounds have been identified in leachates from a Swedish municipal landfill.... more Forty-five organic compounds have been identified in leachates from a Swedish municipal landfill. The samples were taken from the interior of the landfill to minimize alterations caused by contact with the surroundings and were identified and quantified by gas chromatography combined with mass spectrometry. Two analytical procedures were used, one for priority pollutants, the other for a wider range of phenolic and neutral compounds and acids. Analyses of the leachates for water quality parameters indicated that the part of the landfill which was sampled had reached an anaerobic stage in which methane was being produced. Possible origins for most of the compounds identified have been suggested.
Emissions of organic compounds from landfills depend on the fate of the compounds inside the land... more Emissions of organic compounds from landfills depend on the fate of the compounds inside the landfills. This field study was used to investigate the fate in landfills of organic compounds having different physical, chemical, and biological characteristics. For this purpose, a pilot-scale landfill was constructed containing 540 m3 of ordinary household waste, 12 organic compounds were added at the top of the landfill, and leachate and landfill gas samples were continually collected and analyzed. The fate of each compound was theoretically estimated from literature data on the processes which significantly affect the compounds: sorption, dissociation, evaporation, and transformation. These processes could be described by the octanol/water coefficients, Kow, the acid dissociation constants, pKa, the Henry's law constants, H, and the potential of the compounds to be biologically transformed. The use of a ranking score system was suggested as a tool for interpreting the predicted fate of specific compounds caused by several simultaneous processes. A good correlation could be found between the measured emissions and the theoretically evaluated fate. It was concluded that the construction of a pilot-scale landfill is a useful method for studying simultaneous processes in landfills and that the emissions of organic compounds from landfills can be qualitatively predicted from literature data.
W ithout a doubt, scientific research has contributed immensely to human progress and to the deve... more W ithout a doubt, scientific research has contributed immensely to human progress and to the development of modern society. Yet, the way in which scientific endeavors are pursued around the world is marked by clear inequalities (1). Developing countries generally spend less money on scientific research than industrialized countries (in relation to gross domestic product), and the number of scientists is smaller (in relation to population). For example, recruitment of new scientists in Africa has been very slow in the past few years. In addition, the number of Ph.D. holders of African descent who live and work outside their home countries far exceeds the total number of African-born scientists with Ph.D.s who work in Africa (2). Because of the uneven global distribution of resources needed to build and maintain scientific capacity, a large share of new research is created in industrialized countries, and much of that science neglects the problems that afflict most of the world's population (1). This unbalanced distribution generates serious problems for not only the scientific communities in the developing countries but also development itself. In addition to a critical mass of trained staff, another important factor in the technological development of a country is the availability of properly functioning scientific equipment (3). Unfortunately, many laboratories in developing countries are underequipped because of a lack of funds. Some institutions have poured their hardearned funds into buying capital equipment, only to discover that the instruments cannot be used for reasons related to installation, servicing, and maintenance. Using scientific equipment in a developing country is often surprisingly difficult because of infrastructure and climate conditions (4). Many universities and institutions have reported that maintenance and servicing are often a low priority (5-7). A 700-respondent survey conducted by Gaillard and Tullberg showed that, apart from insufficient funds, lack of access to functioning equipment was the main constraint to scientific research in Africa (8). The lack of competent technicians and support staff was identified as the fourth major problem. (The third Scientific research is the cornerstone of national growth, yet properly functioning scientific equipment cannot be taken for granted in developing countries. Scientific research is the cornerstone of national growth, yet properly functioning scientific equipment cannot be taken for granted in developing countries.
... In a parallel study, the fate of organic compounds in the landfill was determined (Öman submi... more ... In a parallel study, the fate of organic compounds in the landfill was determined (Öman submitted). ... More recent studies have also pointed out the heterogeneity of the landfilled waste and the existence of preferential flow paths (Bengtsson et al., 1994; Khanbilvardi et al., 1995 ...
It is generally accepted that scientific research offers a tool for meeting the development deman... more It is generally accepted that scientific research offers a tool for meeting the development demands in the area of water and sanitation. It is stressed by the authors that research should be performed by researchers in the countries most affected, on topics identified by these researchers and in their own environment. For researchers in developing countries the resources and scientific infrastructure constitutes a hindrance to scientific research. To address the situation this paper presents a strategy for scientific capacity strengthening. The strategy builds on a number of activities including; training courses on scientific methodology, literature review, fundraising, sampling, laboratory practices, statistical methods, experimental designs, participatory approaches, oral presentation, posters and manuscript development, as well as thematic workshops, workshop for revision of proposals, contacts with end-users, research grants, networks, purchasing and maintaining scientific equipment and scientific conferences. The strategy builds heavily on collaboration with local organisations. It has been concluded through assessments of activities arranged in Bangladesh, Benin, Burkina Faso, Cameroon, Ivory Coast, Ghana, Mali, Niger, Nigeria, Nepal, Sri Lanka and Togo that the strategy has been successful.
A large number of hazardous compounds can be expected to be present in landfill leachates, many o... more A large number of hazardous compounds can be expected to be present in landfill leachates, many of which have not yet been identified. Thus this study screened samples from 12 Swedish municipal landfill sites for 400 parameters and compounds. More than 90 organic and metal organic compounds and 50 inorganic elements were detected, some of which seem to have not been detected before. Compounds detected include halogenated aliphatic compounds, benzene and alkylated benzenes, phenol and alkylated phenols, ethoxylates, polycyclic aromatic compounds, phthalic esters, chlorinated benzenes, chlorinated phenols, PCB, chlorinated dioxins and chlorinated furans, bromated flame-retardants, pesticides, organic tin, methyl mercury and heavy metals. The presence of this large number of hazardous compounds in landfill leachates should have a significant impact on future landfill risk assessments and the development of leachate treatment methods. We propose that future research should pay more atte...
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Papers by Cecilia Oman