<p>This thesis compares different methods for risk assessment of a creosote contaminated site in Vansbro, Dalarna. In a complementary study the importance of using representative data for calibration and validation of stationary groundwater models is discussed. The time dependency between surface water levels and groundwater levels on the site in Vansbro is evaluated by step response analysis. The results show that the groundwater levels reflect only long-term variation in the surface water levels. Hence the use of such long-term means for calibration and validation of the stationary groundwater models is the only theoretically defendable alternative.</p><p>As a first step in the comparison of risk assessment methods the degree of contamination is evaluated on the basis of generic guideline values for contaminated soils, developed by the Swedish Environmental Protection Agency. The guidelines specifically developed for contaminated petrol stations are also taken into consideration. Secondly, a site-specific evaluation is carried out. The transport of contaminants from the soil to the on-site groundwater and nearby surface water is calculated using the mathematical models behind the aforementioned guideline values. The calculated groundwater concentrations show a poor agreement with observed data and the thesis points out several possible explanations of this deviation. A sensitivity analysis is carried out and the influence of biodegradation during the transport in the aquifer is evaluated. The results indicate that the deviation between observed and calculated groundwater concentrations cannot be explained by the absence of biodegradation in the mathematical models, but rather by other simplifications and uncertainties in estimated model parameters.</p><p>Finally, a risk assessment is made on the basis of observed groundwater concentrations instead of observed soil concentrations as in the assessments above. Observed groundwater concentrations are compared with guideline values for groundwater on contaminated sites. The risk of negative environmental effects in the surface water is evaluated based on the estimated inflow of contaminated groundwater and its concentration of contaminants. The inflow is estimated from the interpolation of observed groundwater levels as well as with two numerical groundwater models of varying hydrogeological complexity: a three-dimensional flow model developed in Visual MODFLOW and a two-dimensional flow model developed in TWODAN. The models are compared with respect to the calculated inflows of contaminated groundwater into the surface water body as well as their ability to reproduce observed groundwater levels. The results indicate that the differences between the models, with respect to the calculated inflows, are of lesser importance to the risk assessment in comparison with the uncertainties associated with other parameters. The choice to base the assessment on observed contaminant concentrations in either the soil or the groundwater is shown to be of crucial importance.</p> / <p>I detta examensarbete jämförs olika metoder att bedöma de hälsomässiga och miljömässiga risker som föreligger med ett kreosotförorenat markområde i Vansbro, Dalarna. I en kompletterande undersökning belyses vikten av att stationära grundvattenmodeller kalibreras och valideras mot tidskompatibla indata. Tidsberoendet mellan yt- och grundvattennivåer på området i Vansbro studeras genom stegsvarsanalys. Resultaten visar att grundvattennivåerna på området anpassar sig mycket långsamt efter rådande ytvattennivåer. Grundvattennivåerna återspeglar således medelvärden av ytvattennivåerna över en mycket lång tidsperiod. Därför är användandet av sådana medelvärden för kalibrering och validering av modellerna det enda teoretiskt försvarbara alternativet.</p><p>Som ett första steg i jämförelsen mellan olika riskbedömningsmetoder utvärderas föroreningssituationen baserat på uppmätta föroreningskoncentrationer i jorden och med hjälp av Naturvårdsverkets generella samt branschspecifika riktvärden för förorenad mark. Därefter genomförs en platsspecifik riskbedömning. Föroreningstransporten från markområdet till grundvattnet samt till ett närbeläget ytvatten beräknas med de matematiska modeller som användes av Naturvårdsverket vid framtagandet av ovannämnda riktvärden. Beräknade grundvattenkoncentrationer jämförs med uppmätta koncentrationer och resultaten visar på stora avvikelser. En känslighetsanalys utförs och inverkan av biologisk nedbrytning i akviferen utvärderas. Resultaten tyder på att avvikelsen mellan uppmätta och beräknade grundvattenkoncentrationer ej förklaras av att biologisk nedbrytning inte beaktas i modellerna utan att avvikelsen härrör från andra förenklingar och från osäkerheter i indata.</p><p>Slutligen genomförs en platsspecifik riskbedömning, motsvarande den ovan, men denna gång utifrån uppmätta föroreningskoncentrationer i grundvattnet. De uppmätta grundvattenkoncentrationerna jämförs direkt mot Naturvårdsverkets riktvärden för grundvatten på förorenade områden. Risken för negativa ekologiska effekter i ytvattnet utvärderas utifrån det beräknade inflödet av förorenat grundvatten samt dess koncentration. Inflödet beräknas överslagsmässigt utifrån interpolerade grundvattennivåer samt med två numeriska grundvattenmodeller av olika hydrogeologisk komplexitet: en tredimensionell flödesmodell uppbyggd i Visual MODFLOW och en tvådimensionell modell uppbyggd i TWODAN. Grundvattenmodellerna jämförs med avseende på det beräknade inflödet och med avseende på deras förmåga att beskriva observerade grundvattenförhållanden.Resultaten tyder på att skillnaden i det, med de olika metoderna, beräknade inflödet är av liten betydelse för riskbedömningen i förhållande till osäkerheter förknippade med övriga parametrar. Störst betydelse för riskbedömningen får valet att utgå från uppmätta föroreningskoncentrationer i antingen jorden eller grundvattnet.</p>

This study examined the interaction of model cationic, neutral and anionic endocrine disrupting compounds, pharmaceuticals and personal care products (EDC/PPCPs) with bulk and fractionated freshwater and waste water dissolved organic matter (DOM). The chemical composition of the freshwater DOM (Suwannee River, GA, SROM) proved to be rich in plant-derived hydrophobic aromatics, while the wastewater DOM (WWOM) contained a greater proportion of microbial biomolecular products, presumably resulting mainly from human waste. Studies focused on the fluorescence quenching of excitation-emission matrices (EEMs) of WWOM indicated that interaction with bis-phenol A (BPA), carbamazepine (CBZ), and ibuprofen (IBU) occurred preferentially with soluble protein-like and fulvic acid-like constituents. However, upon introduction to bulk SROM, BPA and CBZ were observed to quench humic acid-like regions of the EEMs, while negatively charged ibuprofen preferentially quenched the protein-like and fulvic acid components irrespective of DOM source and/or fraction. Despite this evidence of EDC/PPCP interactions with both DOM types, the strength of bonds formed was generally not sufficient to preclude full recovery and quantification of all three contaminants by liquid chromatography tandem mass spectrometry (LC-MSMS). An important exception, however, was for the hydrophilic acid fraction (HiA) of both DOM types, whose apparent bonding to cationic CBZ and anionic IBU significantly diminished LC-MSMS recovery. Thus, water sources rich in HiA character might produce a concentration underestimation of ionized EDC/PPCPs even with the use of sophisticated instruments such as LC-MSMS.The results of this research are consistent with the evolving ""supramolecular"" theory of natural organic matter, which postulates that organic matter itself is comprised of fragments of partially degraded biomolecules that are aggregated into ""supramolecular"" structures of apparent higher molar mass via relatively weak electrostatic, hydrophobic, and van der Waals interaction. Our findings suggest that EDC/PPCP contaminants, which comprise many of the same functional groups as waste water and freshwater DOM, may be incorporated into such DOM supramolecular structures, likely via the same types of intermolecular bonding, when they are present in natural waters under environmentally-relevant conditions.

The magnitude of contaminant mass flux reduction associated with a specific amount of contaminant mass removed is a key consideration for evaluating the effectiveness of a source-zone remediation effort. Thus, there is great interest in characterizing, estimating and predicting relationships between mass flux reduction and mass removal. Intermediate-scale flow- cell experiments and published data for several field studies were examined to evaluate factors controlling the mass-flux-reduction/mass-removal relationship. Flow-cell experiments evaluated the impact of source-zone architecture and flow-field heterogeneity on mass-flux-reduction/mass-removal behavior. Significant reductions in mass flux occurred for systems wherein immiscible-liquid mass was present at both residual saturation and in high saturation pools. For a system with immiscible liquid present in multiple zones of different permeability, an increase in mass flux was observed for late stages of mass removal. Image analysis confirmed that the late stage increase in mass flux was attributed to changes in relative permeability. Early reductions in mass flux were also observed for systems wherein immiscible-liquid mass was poorly accessible to flowing water. End-point analysis, based on comparing masses and mass fluxes measured before and after a source-zone remediation effort, conducted for 21 field remediation projects ranged from slightly less than to slightly greater than one-to-one. Time-continuous analysis, based on continuous monitoring of mass removal and mass flux, performed for two sites illustrated the dependence of the mass-flux-reduction/mass-removal relationship on source-zone architecture and mass-transfer processes. Minimal mass flux reduction was observed for a system wherein mass removal was relatively efficient. Conversely, a significant degree of mass flux reduction was observed for a site wherein mass removal was inefficient. A simple mass-removal function was used to evaluate the measured data at both the intermediate and field scales. This function was unable to capture the complex behavior observed for some of the systems unless specific measurable system parameters were incorporated into the function. Finally, mathematical models of varying complexity used to simulate immiscible liquid dissolution illustrated the dependence of the calibrated dissolution rate coefficient on implicit and explicit consideration of larger-scale factors influencing immiscible liquid dissolution.

Volatile Organic Compounds (VOCs) constitute an important class of indoor air contaminants and they may cause adverse health effects for occupants in buildings. Indoor generated contaminants may be transferred between the supply and exhaust air streams of the building’s Heating, Ventilation and Air-conditioning (HVAC) system when air-to-air energy recovery devices are used. The run-around membrane energy exchanger (RAMEE) is a novel exchanger, which uses aqueous magnesium chloride (MgCl2) salt solution (34-35 wt%) as a liquid desiccant to transfer heat and moisture between remote supply and exhaust air streams. In the RAMEE, a gas-phase porous membrane is placed between the air stream and the liquid desiccant stream in each exchanger and the membrane prevents the salt solution from entering the air stream but still allows the transfer of water vapor through the semi-permeable membrane. In the RAMEE, VOCs may transfer between the exhaust and supply air streams due to (i) air leakage or (ii) due to dissolution of VOCs into the liquid desiccant in the exhaust exchanger and their subsequent evaporation into the air stream of the supply exchanger. These two transfer mechanisms were tested in the laboratory using two counter-cross-flow RAMEE prototypes (Prototype #4 and Prototype #6). Tests were conducted at different air and desiccant flow rates at AHRI standard summer and winter operating conditions. Sulfur hexafluoride (SF6) was used as a tracer gas to test air leakage and toluene (C7H8) and formaldehyde (HCHO) were used to test VOC dissolution and transfer. From an external source, a known concentration of VOC was injected into the exhaust air inlet stream and the transfer fraction of VOC to the supply air stream was calculated. This transfer fraction or Exhaust Air Transfer Ratio (EATR) defined by ANSI/ASHRAE Standard 84 (2012) at steady state conditions was used to quantify and compare the transfer fraction of contaminants in both prototypes. The uncertainty in the transfer fraction was calculated and all the uncertainty bounds were calculated for 95% confidence interval. The transfer fraction of sulfur hexafluoride was 0.02 +/- 3.6% for both prototypes tested, which means that the air leakage between the air streams is negligible. The transfer of toluene, which has a low solubility in water, was less than the uncertainty in the measurement. EATR* values for toluene were 2.3-3.4% and the uncertainties were 3.4-3.6%. The transfer of formaldehyde between the exhaust and the supply air streams was the highest and the EATR* values just exceeded the uncertainties in the EATR* measurement. The highest EATR* values for the transfer of formaldehyde in Prototype #4 and Prototype #6 were 6.4 +/- 3.6% and 5.3 +/- 3.6%, respectively. At steady state, the measured EATR* values for both prototypes were insensitive to changes in the air flow rate, the liquid desiccant flow rate, the latent effectiveness and the environmental conditions but time delays to reach steady state were significant. These results imply that there is a negligible transfer of contaminants due to air leakage between the air streams, a negligible transfer of low water soluble VOCs (such as toluene), but possibly a small detectable transfer of very water soluble VOCs (such as formaldehyde) between the exhaust and supply air streams of the RAMEE.

A series of local and bench scale laboratory experiments and bench and field scale numerical simulations were conducted to develop a better understanding of the interrelationship between nonwetting phase (NWP) source zones and downgradient aqueous phase concentrations in saturated porous media contaminated by immiscible organic liquids. Specific emphasis was placed on the factors governing the rate of NWP source zone evolution and the factors governing the rate of mass transfer from the NWP to the aqueous phase. Hysteretic NWP relative permeability-saturation (krN-SW) relationships were measured at the local scale for six sands to examine the relationship between krN-SW functions and porous media type. Parameterization of the measured constitutive relationships revealed a strong correlation between mean grain diameter and the maximum value of NWP relative permeability. The measured krN-SW relationships, were validated through a bench scale experiment involving the infiltration, redistribution, and immobilisation of NWP in an initially water saturated heterogeneous porous medium. This match of simulation to experiment represents the first validation of a multiphase flow model for transient, fixed volume NWP releases. Multiphase flow simulations of the bench scale experiment were only able to reproduce the experimental observations, in both time and space, when the measured krN-SW relationships were employed. Two-dimensional field scale simulations of a fixed volume NWP release into a heterogeneous aquifer demonstrate the influence of spatially variable krN-S relationships correlated to porous media type. Both the volume of the NWP invaded porous media, and the length of time during which NWP is migrating, will be under predicted if variable (correlated) kr,N is not accounted for in the numerical model iv formulation. This under prediction is exacerbated as the mean intrinsic permeability of the release location decreases. A new, thermodynamically-based interfacial area (IFA) model was developed for use in the single-boundary layer expression of mass transfer as an alternative to existing empirical correlation expressions. The IFA model considers consistency and continuity of constitutive relationships, energy losses, effective specific interfacial area for mass transfer, and dissolution of residual NWP. A bench scale experiment involving the release and dissolution of a transient NWP source zone in heterogeneous porous media was conducted to evaluate the appropriateness of the developed IFA model when utilised to predict NWP dissolution rates. Comparison of measured downgradient dissolved phase concentrations and source zone NWP saturations in time and space with those from numerical simulations of the experiment reveal that the proposed IFA model is superior to both a local equilibrium assumption and existing empirical correlation expressions. This represents the first mass transfer model validated for the dissolution of a complex NWP source zone. Twodimensional simulations at the field scale of multiphase flow and dissolution suggest that employing existing mass transfer expressions instead of the IFA model lead to incorrect predictions of the life spans of NWP source zones, downgradient dissolved phase concentrations, and the rate of mass flux through a downgradient boundary. The practical implication of this research is that accurate numerical predictions of the evolution of a transient NWP source in porous media require consideration of krN-S relationships and NWP / aqueous phase IFA, as these factors dictate the rates of the key subsurface contaminant processes of migration and dissolution, respectively.

Master of Science / Department of Mechanical and Nuclear Engineering / Mohammad H. Hosni / Byron W. Jones / With the increasing number of passengers traveling on commercial aircraft, it is important to mitigate the possibility of diseases and contaminants spreading throughout aircraft cabins and becoming harmful to the health of passengers. The ventilation system on a Boeing 767 aircraft is designed to create lateral flow to isolate contaminants to a single row of the cabin and remove the harmful air quickly. There are many variables that can influence the airflow patterns inside the cabin. The thermal plumes created by occupants are one of the variables investigated in this experimentation. Another special case investigated is the transport of gases in the cabin when the ventilation air is eliminated. Experimentation is performed in a mock-up Boeing 767 cabin. The mock-up enclosure consists of 11 rows and 7 columns of seats in each row. Ventilation apparatus, seating, and cabin dimensions used for testing are all representative of an actual aircraft. Thermal manikins are placed in the cabin seats to simulate the heat load from a seated person. A mixture of carbon dioxide (CO²) and helium (He) is injected into the cabin as a tracer gas to simulate the release of contaminants. The CO² concentration is measured by analyzers placed at the cabin inlet, exhaust, and seat of interest. The tracer gas can be injected and sampled at any of the 77 seats. In order to determine the effects of passenger density, testing is performed with maximum occupant load and repeated with half of the passenger load. Tracer gas is injected in three locations of the cabin and sampled in 32 seats for each injection seat. The testing revealed a significant effect of passenger load on airflow patterns. To determine the effects of removing the ventilation air, the cabin is supplied with 1400 cfm of outdoor air at 60°F for three hours to bring the cabin to a steady state temperature. Then, the supply air is shut off, and tracer gas is injected into the cabin and the CO² concentration is sampled at 12 locations throughout the cabin. It was found that contaminants are still transported throughout the cabin without the ventilation air.

A ocorrência de produtos farmacêuticos e de cuidados pessoais no meio ambiente tem levado a preocupações sobre seu impacto ambiental e à saúde pública. O sulfametoxazol (SMX) é um fármaco que tem sido encontrado amplamente no ambiente. Neste estudo foi verificada a eficácia de vários processos, a saber eletroquímico, eletroquímico foto assistido, fotoquímico, Fenton e foto-Fenton, para a degradação de SMX em solução aquosa. A degradação eletroquímica e eletroquímica foto assistida foram realizadas em uma célula de fluxo do tipo filtro-prensa, usando um ânodo dimensionalmente estável comercial com composição nominal Ti/Ru0,3Ti0,7O2. Durante ambos os processos, efeitos de diferentes parâmetros foram analisados, como a natureza do eletrólito, a concentração de eletrólito suporte (NaCl) e a densidade de corrente aplicada. Os experimentos fotoquímicos, Fenton e foto-Fenton foram realizados em um reator de vidro cilíndrico de compartimento único. O efeito das concentrações inicias de Fe2+ e de H2O2 foram estudados para os processos Fenton e foto-Fenton. Similarmente, o efeito do pH inicial, a concentração inicial do SMX e a temperatura foram investigados para todos os processos. A variação da concentração de SMX foi determinada por cromatografia líquida de alta eficiência (CLAE) e a quantidade de matéria orgânica foi monitorada por análise de carbono orgânico total (COT). Os resultados obtidos indicaram que o SMX foi completamente degradado, porém, o COT foi apenas parcialmente removido em todos os processos. No período de tempo de ensaio estabelecido o aumento da densidade de corrente e da concentração de NaCl mais eficiente para a degradação e remoção de COT nos processos eletroquímicos. A quantidade de Fe2+ e H2O2 aumenta a eficiência do processo Fenton e foto-Fenton, e meio ácido foi favorável para todos os processos. O consumo de energia elétrica, baseado no parâmetro EEO (energia por ordem) mostrou que os processos eletroquímicos são energeticamente mais eficientes do que os fotoquímicos. As degradações acompanhadas por CLAE acoplado à espectrometria de massas, permitiu que vários intermediários fossem identificados, sendo então proposta uma sequência reacional para a degradação do SMX. O radical hidroxila e o cloro ativo atacam os anéis benzílico e isoxazólico, tendo sido demonstrado que os compostos iniciais formados foram os compostos hidrolisados e clorados. Os íons inorgânicos, tais como: NO3-, NH4+ e SO42-, também foram identificados durante os processos de degradação. / The occurrence of pharmaceuticals and personal care products in the environment has raised concerns about their impact upon environmental and public health. Sulfamethoxazole (SMX) is a pharmaceutical that has been found widely in the environment. This study investigated the effectiveness of various processes such as electrochemical, photo assisted electrochemical, photochemical, Fenton photo-Fenton to SMX degradation in aqueous solution. The electrochemical and photo-assisted electrochemical degradations were performed in a filter press type flow cell using a dimensionally stable anode with nominal composition of Ti/Ru0.3Ti0.7O2. During both these processes the effects of different parameters were analyzed, such as, nature of the electrolyte concentration of the supporting electrolyte (NaCl) and the applied current density. The photochemical, Fenton and photo - Fenton experiments were carried out in a single compartment cylindrical glass reactor. The effects initial iron concentrations and H2O2 were studied for Fenton and photo-Fenton processes. Similarly the effect of initial pH, initial concentration of SMX and temperature were investigated for all processes. The variation of SMX concentration was determined by high performance liquid chromatography (HPLC) and the amount of organic matter was monitored by analysis of total organic carbon (TOC). The results indicated that SMX was completely degraded, but TOC was partially removed in all processes studied, during experimental period the increase of the current density and NaCl concentration enhanced the degradation and TOC removal in the electrochemical processes. The amount of iron and H2O2 increases the efficiency of Fenton and photo-Fenton processes and acidic media was favorable for all processes. The electrical energy consumption parameter based on EEO (energy per order) was also evaluated and it was observed that the electrochemical processes are more energetically efficient than the photochemical. The degradations followed by HPLC coupled with mass spectrometry, in which several intermediates were identified and proposed a reaction sequence for the degradation of SMX. The hydroxyl radical and active chlorine attack benzene and isoxazólico rings, and has been demonstrated that the initial compounds formed were hydrolyzed and chlorinated compounds. Inorganic ions such NO3-, NH4+ and SO42- were also identified during degradation processes.

Pesticide use has steadily increased in the United States and throughout the world since the development of more highly effective agrichemicals dating back to World War II. While many of these compounds are considered to have little to no detrimental environmental impact with relatively low toxicity and potential for causing adverse health effects in humans, many recent studies examining the toxicological properties and health outcomes associated with exposure to a variety of pesticides suggest otherwise. In heavily agricultural-based regions, particularly where row crops predominate, large amounts of herbicides and insecticides are used in activities involving pest management annually. The high volume of chemical applications to agricultural fields is cause for concern due their potential for leaching into soil following application events and subsequent transport to water systems. Pesticide-contaminated ground and surface water systems may pose a threat to public health by the presence and persistent elevated concentrations of chemicals found in both public and private drinking water. The herbicides atrazine and glyphosate are and have been the two most heavily applied pesticides in the U.S. Many studies have examined occupational exposures to these compounds and related health outcomes, yet very few have evaluated low-level exposures to more susceptible rural populations. This thesis will examine state-of-the- science behind atrazine and glyphosate, evaluate drinking water quality measurements in relation to herbicide usage estimates in Iowa, and finally, make recommendations for future atrazine and glyphosate exposure assessment studies in rural Iowa populations.

Soil Washing is a promising alternative treatment method for contaminated site remediation. An industry contaminated site - the OMEX site was selected for the study, and several extraction additives (chelating agent and surfactant) were used to investigate the application of soil washing for the removal of heavy metals and hydrocarbons. The interactions and transport of the contaminants were studied by bench-scale experiments for both heavy metals and hydrocarbons. Soil characterization was performed before the experiments.The soil characterization indicated that the OMEX soil contained large amounts of Pb, Zn (heavy metal) and total petroleum hydrocarbons (TPH). The contaminant concentrations were 986 mg/kg of Pb, 284 mg/kg of Zn, and 29000 mg/kg of TPH. The contaminated soil was also high in moisture content, organic content and total organic carbon (TOC). From soil analyses on different particle size fractions, most contaminants were concentrated in the fine soil fraction, below 150gm, which constituted about 35% by weight of the contaminated soil.Heavy metal removal by chelating agents was conducted first. The results showed that 3% EDTA solution offered the highest removal efficiency for both Pb and Zn. About 90% of Pb and 65% of Zn were removed by using 3% EDTA solution for 29 hours. The extraction kinetics proved to be slow, reaching equilibrium in a relatively long time (more than 10 hours). In soil washing the solution pH had some effect on the removal of both Pb and Zn with marginally better removals observed at a lower pH. The experimental study indicated that the ratio of washing solution volume to soil weight (LIS) had little effect on the percentage removal of both Pb and Zn.In hydrocarbons removal tests, experiments verified that surfactant solutions can be effective in removing organics from coarse soil fraction, while some amount of surfactants were ++ / adsorbed by fine soil particles. Anionic surfactants such as SIDS exhibited less sorption capacity than nonionic surfactants due to the electrostatic repulsion of the former. 4% SDS solution had the highest TPH removal efficiency for OMEX soil, but the 2% SIDS solution was used as it produced only marginally lower results than the 4%. The percentage removal of TPH was about 78% by using 2% SIDS solution. The TPH removal by SDS solution was observed to be a slow and non-equilibrium process. Higher solution temperature can improve removal efficiency of TPH from OMEX soil. Combined washing with a chelating agent and a surfactant was effective in removing both heavy metals and hydrocarbons. Removals of 78% Pb, 82% Zn and 81% TPH were obtained from OMEX soil in the combination test. However, the TPH concentration in fine soil was still very high after washing and would need further treatment.

The most common method of monitoring and mapping groundwatercontaminants is to extract and analyse a number of groundwatersamples from wells in the investigation area. However, thereare a number of limitations with this type of point-wiseinvestigation, as it is hard to acquire an adequate picture ofa heterogeneous and anisotropic subsurface using a fewpoints. To overcome the limitations of point investigations and toimprove ground monitoring investigations in a cost-effectiveway, support can be provided by direct current resistivitymeasurements, which give a characterisation of the electricalproperties of a ground volume. The main objective with this work was to investigate theusability of the resistivity method as a support in monitoringgroundwater contaminants in glaciated terrains and underdifferent seasons, both in long-term monitoring programmes andintracer tests. The work comprised field investigations at several differentsanitary landfills and four tracer tests in differentgeological environments, around the Stockholm region. The maininvestigations have been done at Högbytorp, Stockholmwhich has been used for long-term investigations of theresistivity variation, together with a field set up formonitoring and measurements on seasonal variation in soilmoisture, ground temperature and precipitation. It can be concluded that the use of resistivity measurementssupplies valuable information in the case of mapping andmonitoring conductive groundwater contaminants andfurthermore: The variation in resistivity (in shallow investigations&lt;1 m) can be extensive between different seasons (around30 % compared to a mean value in till and clay soils) andshould be considered, so that anthropogenic affects can beseparated from natural resistivity variation. For deeperinvestigations (&gt;5 m) the seasonal resistivity variationwas more moderate (around 15% compared to a mean value intill and clay soils). Soil moisture variation shows a strong relationship toresistivity variation in the investigated clay and tillsoils. Together with temperature correction 47 to 65% of thevariation has been explained. Three types of monitoring systems can be applied:Permanently installed, partly installed and fully mobilesystems. For the actual measurements, all three types can useeither high-density techniques such as CVES (ContinuousVertical Electrical Sounding) or low-density measuring withone or some different electrode spacings. The suggested evaluation tool for monitoring programmesshowed that it was possible to detect a decrease of 15 % inthe mean value at a specific site using Modified Double Masscalculations between resistivity time series and time seriesat a reference site with a comparable seasonalvariation. Resistivity measurements may be used as a valuablecomplement to groundwater sampling in tracer tests. Adecrease in resistivity, a minimum and a recovery phasereflect the passage of a NaCl-solution, which can be used toestimate flow velocity and flow patterns of the investigatedaquifer. The achieved recovery of NaCl in the tracer testscarried out was estimated to 20 to 70 %. The measurement system for long-term monitoring or tracertests, which should be chosen with regard to layout andfrequency, depends on the purpose of measurement and onsite-specific conditions and therefore no standard solutioncan be proposed. Key words:Resistivity, Direct Current, Monitoring,Groundwater, Contaminant, Tracer test, Geophysics.