Hydrochemical and Sediment Biomarker Evidence of the Impact of Organic Matter Biodegradation on Arsenic Mobilization in Shallow Aquifers of Datong Basin,China

Biomarker and hydrochemical characteristics of geogenic arsenic-contaminated aquifers at Datong Basin, northern China, were analyzed to better understand the impact of organic matter (OM) biodegradation on arsenic enrichment in groundwater. The hydrochemical characteristics of high arsenic groundwater from the Datong Basin indicate that arsenic mobilization and iron and manganese oxide/hydroxide reduction were controlled by biodegradation of OM. The elevated value of alkalinity produced by microbial oxidation of OM is another important factor for arsenic mobilization via competitive sorption. Bulk geochemistry of the sediments shows that arsenic has close correlation with iron and manganese, indicating iron- and manganese-bearing minerals could be the major pools for arsenic. Results of biomarker analysis reveal that all the sediments contained natural petroleum-sourced hydrocarbons which may have undergone biodegradation, as suggested by the carbon preference index, C₂₉ sterane, and the distribution pattern of hopanes. The presence of unresolved complex mixtures in all samples also indicates the natural petroleum origin of hydrocarbons and the effect of biodegradation. At some depths (5.4–11.8, 31–33.2, and 40–48.4 m below the land surface), the samples have low n-alkane content and no odd-over-even predominance, suggesting that indigenous microbes within the aquifer can preferentially remove the petroleum-sourced n-alkanes. The bioavailability of organic carbon is very important to promote the microbially mediated reductive dissolution of iron oxides/hydroxides and subsequent arsenic release from aquifer sediment into groundwater.     

Modelling the Density Contrast Effect on a Chlorinated Hydrocarbon Plume Reaching the Shore Line

Diffused petroleum and chlorinated hydrocarbon contamination was detected in a sandy aquifer below a chemical plant in Southern Italy. The contamination was due to underground leaking tanks and pipes. The site is located near the shore line and is bordered by canals which, in combination with pumping wells, control the groundwater flow direction toward the sea. In this study, a comprehensive three-dimensional flow model was developed and calibrated to simulate the general groundwater flow system and to individuate a flow line. On this latter, a detailed field investigation was performed in order to determine the fate of dissolved hydrocarbons. Depth profiles obtained from multi-level samplers located along the modelled flow line, including measurements of hydrocarbons, all major ions and dissolved gasses, were used to constrain the conceptual model. These data were then included into a two-dimensional transport model in order to verify the efficacy of the hydraulic barrier (HB) in preventing the hydrocarbon plume to reach the shore line. Two different approaches were used in the transport simulation, one accounting for density-dependent flow and the other not. The calibrated models show that the plume length and consequently, the submarine groundwater discharge of contaminants is slightly different for the two approaches. For the simulation not accounting for the density contrast between freshwater and saltwater, the mass of contaminant discharged downstream to the HB was underestimated and also the reconstructed plume geometry was different than the observed. Moreover, the reconstruction of the saltwater intrusion interface (SWII) with the two different approaches was substantially different. This study demonstrates that at field site, variable density processes should be carefully taken into account not only when the modelling is devoted to the reconstruction of the SWII but also when the modelling is targeting the fate of hydrocarbons at sites affected by SWII, in order to provide accurate data on which soundly environmental management of the coastal zone can be based.     

Assessing the Effect of Saltwater Intrusion on Petroleum Hydrocarbons Plumes Via Numerical Modelling

A contamination by petroleum hydrocarbons was detected in a sandy aquifer below a petrochemical plant in Southern Italy. The site is located near the coastline and bordered by canals which, together with pumping wells, control submarine groundwater discharge toward the sea and seawater intrusion (SWI) inland. In this study, a three-dimensional flow and transport model was developed using SEAWAT-4.0 to simulate the density-dependent groundwater flow system. Equivalent freshwater heads from 246 piezometers were employed to calibrate the flow simulation, while salinity in 193 piezometers was used to calibrate the conservative transport. A second dissolved species, total petroleum hydrocarbons (TPH), was included in the numerical model to simulate the plumes originating from light non-aqueous-phase liquid. A detailed field investigation was performed in order to determine the fate of dissolved hydrocarbons. Fifteen depth profiles obtained from multilevel samplers (MLS) were used to improve the conceptual model, originally built using a standard monitoring technique with integrated depth sampling (IDS) of salinity and TPH concentrations. The calibrated simulation emphasises that density-dependent flow has a great influence on the migration pattern of the hydrocarbons plume. This study confirms that calibration of density-dependent models in sites affected by SWI can be successfully reached only with MLS data, while standard IDS data can lead to misleading results. Thus, it is recommended to include MLS in the characterization protocols of contaminated sites affected by SWI, in order to properly manage environmental pollution problems of coastal zones.     

高级氧化技术修复萘污染土壤和地下水研究进展

多环芳烃是土壤和地下水中普遍存在的持久性有机污染物。其中，萘是结构最简单的多环芳烃，具有迁移性强的特点，可通过多种途径在土壤和地下水中富集，是焦化、化工等历史遗留地块重点关注的污染物之一。高级氧化技术高效、安全且经济，因此，基于高级氧化的萘污染土壤和地下水修复技术受到越来越多的关注。本文综述了芬顿和类芬顿氧化、臭氧氧化和过硫酸盐氧化的反应机理，重点阐述了二价铁、微纳级零价铁、铁矿物、铁螯合物等均相及非均相活化剂活化的氧化技术在修复萘污染土壤和地下水方面取得的研究进展，介绍了多种高级氧化技术联合修复以及高级氧化技术与生物降解技术协同修复的研究现状，指出了目前萘的高级氧化技术研究存在的问题，并对研究做出了展望。     

Comparison of Two Methods for Assessment of In Situ Jet-fuel Remediation Efficiency

In 1997, total petroleum hydrocarbon (TPH) remediation started at a former Air Force Base, which operated from 1940 to 1991. TPH had been released to soil and groundwater at the site by military activities. The TPH was 70% jet fuel and the affected area covered 28 ha. Remediation involved a combination of technologies, including removal of volatile organic compounds using soil vapor extraction and air sparging, free product vacuum recovery and aerobic biodegradation of organics with oxygen supplied by the air sparging system, along with nutrient addition. The primary remedial method was found to be biodegradation, which has removed 93% of the contaminants from the site to date. A significant aspect of the remedial action was performance monitoring, including documentation of remediation efficiency. The goal of the research was to assess the relative accuracy of methods commonly used for monitoring in situ TPH remediation. Two such methods were selected for the research: monitoring change in soil TPH concentration (specified as non-polar extractable substances) and monitoring respiration activity in soil with a subsequent stoichiometric mass balance to estimate the mass of TPH destroyed. The study demonstrated that both of the methods provided comparable results regarding the effectiveness of in situ TPH remediation, despite the fact that their methodologies are very different.     

Bubble Extraction of Dissolved Gases from Groundwater Samples

A technique is described for measuring the concentration of dissolved methane in water samples. A 250 μL bubble is injected into a 5 mL vial to create a headspace. The headspace gas is subsequently analysed by gas chromatograph. The technique requires a headspace equilibrium time of at least 13 hours. The extraction efficiency of the method for methane saturated water was 101.9% ± 1%. The technique is applicable to other dissolved gases in groundwater. The method was used during a comparative evaluation of groundwater sampling devices at a field site. It was found that low flow rate sampling with either a Grundfos electric submersible pump or a peristaltic pump were more precise than using a bailer to measure dissolved methane.     

Reactive Modeling of Denitrification in Soils with Natural and Depleted Organic Matter

Nitrogen fertilizers used in agriculture often cause nitrate leaching towards shallow groundwater, especially in lowland areas where the flat topography minimize the surface run off. In order to introduce good agricultural practices that reduce the amount of nitrate entering the groundwater system, it is important to quantify the kinetic control on nitrate attenuation capacity. With this aim, a series of anaerobic batch experiments, consisting of loamy soils and nitrate-contaminated groundwater, were carried out using acetate and natural dissolved organic matter as electron donors. Acetate was chosen because it is the main intermediate species in many biodegradation pathways of organic compounds, and it is a suitable carbon source for denitrification. Sorption of acetate was also determined, fitting a Langmuir isotherm in both natural and artificially depleted organic matter soils. Experiments were performed in quadruplicate to account for the spatial variability of soil parameters. The geochemical code PHREEQC (version 2) was used to simulate kinetic denitrification using Monod equation, equilibrium Langmuir sorption of acetate, and equilibrium reactions of gas and mineral phases (calcite). The reactive modeling results highlighted a rapid acetate and nitrate mineralization rate, suggesting that the main pathway of nitrate attenuation is through denitrification while calcite acted as a buffer for pH. However, in the absence of acetate, the natural content of organic matter did not allow to complete the denitrification process leading to nitrite accumulation. Reactive modeling is thought to be an efficient and robust tool to quantify the complex biogeochemical reactions which can take place in underground environments.     

堆肥化过程中有机污染物生物降解的研究进展

简介了卤代烃、多环芳烃、农药类及石油烃类等几种有机污染物在堆肥过程中的生物降解及其机理研究进展,并指出今后应重点加强高效降解微生物的分离培养、基因工程菌的开发、表面活性剂对生物降解的强化作用以及适合有机污染物降解的堆肥条件和有机污染物在堆制过程中降解的中间产物及终产物等方面研究。     

"引大入秦"灌溉工程对甘肃秦王川盆地地下水化学组分的影响

为研究“引大入秦”灌溉工程对秦王川盆地地下水化学组分的影响,该文在对该盆地地下水进行系统采样分析的基础上,通过对比“引大入秦”工程运行前后盆地内水化学数据,利用数理统计、Gibbs图、离子比等方法,对盆地内地下水化学组分演化进行了深入分析。结果表明:工程运行前,研究区水化学类型以Cl·SO4-Na、Cl·SO4-Na·Mg和SO4·Cl-Na为主。工程运行初期,在灌溉渗水淋洗作用下包气带易溶盐进入地下水,盆地地下水向盐化和硬化方向演化。随着工程的继续运行,包气带盐分被逐步洗脱殆尽,灌溉淋滤水的含盐量逐渐降低,其中处于盆地汇水区的平原区中部下降趋势最为明显,地下水化学类型由Cl·SO4-Na演化为HCO3·SO4-Na(Na·Ca·Mg)和Cl·SO4·HCO3-Na。盆地周缘黄土丘陵区水资源贫乏,受原生沉积地层中高含量易溶盐影响,Cl·SO4-Na·Mg型水分布范围基本保持不变。盆地南部当铺一带地下水由Cl·SO4-Na型演化为Cl·SO4-Na·Mg型水。在这一过程中,研究区水化学组分受硅酸盐岩风化溶解以及岩盐和蒸发岩盐溶解共同作用,在蒸发浓缩作用下富集。盆地地下水受工矿企业污染影响较小,但化肥的使用导致地下水NO3-质量浓度明显升高。研究结果为秦王川灌区地下水资源的可持续发开利用提供参考。     

Isotopic evidence and quantification assessment of in situ RDX biodegradation in the deep unsaturated zone

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is an explosive compound whose extensive use has resulted in significant contamination of soils and groundwater worldwide. We studied its in situ biodegradation along the unsaturated zone beneath an explosives wastewater lagoon using compound-specific isotope analysis (CSIA) of RDX in the unsaturated zone, together with biodegradation slurry experiments under anaerobic conditions. We found the highest degradation potential of RDX and its nitroso derivatives in the upper part of the soil profile while in the lower parts, RDX-degradation potential was lower and the nitroso derivatives tended to persist. This was also observed in the field, as reflected by the isotopic composition of RDX along the profile. We also found a correlation between biodegradation potential and clay content: biodegradation was further enhanced in layers characterized by high-clay content or in those influenced by the high-clay layers. In addition, in the presence of high organic matter content, further enhancement of biodegradation was observed. We obtained different isotopic enrichment factors (?) for RDX biodegradation in different sections of the unsaturated profile and suggest that different degradation pathways exist simultaneously in situ, in variable proportions. Using the range of enrichment factors, we were able to assess the biodegradation extent of RDX at different sampling points along the profile, which ranged between 30 and 99.4%. The novel application of CSIA together with slurry experiments provides better insight into degradation processes that are otherwise difficult to detect and assess.     

北京市东南郊再生水灌区地下水多环芳烃污染风险评估

为研究污染物随再生水进入地下环境后其迁移衰减情况及对地下水的潜在危害性,以Multi-cell模型为基础,结合污染物质量守恒、在水土中吸附再分配、生物降解等机理,针对地下水污染风险评估构建了计算污染物随水在土壤剖面的垂向迁移衰减一维模型,并以北京通州大兴再生水灌区为研究区域,以再生水中持久性有机污染物多环芳烃萘和菲为研究对象,根据当地钻孔资料及灌溉水水质、地下水水质资料,应用该模型进行试算。结果表明,经过多年连续灌溉后,通州大兴大部分地区进入潜水含水层的萘、菲浓度较低,整体污染风险较低,仅在通州区潞城镇等个别地区萘、菲浓度较高,应引起重视;由于大兴区整体包气带较厚,其污染风险低于通州区。土壤粘土层是萘、菲积累的主要层位,其吸附容量远大于细砂等粗颗粒介质,在土壤表层低环多环芳烃迁移性更强。应用这一模型,能够较为宏观地掌握通州大兴再生水灌区不同区域地下水中多环芳烃萘和菲的污染风险差异。     

Biodegradation of Synthetic Dyes—A Review

The upper Great Egg Harbor River watershed in New Jersey’s Coastal Plain is urbanized but extensive freshwater wetlands are present downstream. In 2006–2007, studies to assess levels of total mercury (THg) found concentrations in unfiltered streamwater to range as high as 187 ng/L in urbanized areas. THg concentrations were <20 ng/L in streamwater in forested/wetlands areas where both THg and dissolved organic carbon concentrations tended to increase while pH and concentrations of dissolved oxygen and nitrate decreased with flushing of soils after rain. Most of the river’s flow comes from groundwater seepage; unfiltered groundwater samples contained up to 177 ng/L of THg in urban areas where there is a history of well water with THg that exceeds the drinking water standard (2,000 ng/L). THg concentrations were lower (<25 ng/L) in unfiltered groundwater from downstream wetland areas. In addition to higher THg concentrations (mostly particulate), concentrations of chloride were higher in streamwater and groundwater from urban areas than in those from downstream wetland areas. Methylmercury (MeHg) concentrations in unfiltered streamwater ranged from 0.17 ng/L at a forest/wetlands site to 2.94 ng/L at an urban site. The percentage of THg present as MeHg increased as the percentage of forest + wetlands increased, but also was high in some urban areas. MeHg was detected only in groundwater <1 m below the water/sediment interface. Atmospheric deposition is presumed to be the main source of Hg to the wetlands and also may be a source to groundwater, where wastewater inputs in urban areas are hypothesized to mobilize Hg deposited to soils.     

Soil matric potential and salt transport in response to different irrigated lands and soil heterogeneity in the North China Plain

Purpose

In the lowland area of the North China Plain (NCP), increasing utilization of brackish water could promote the transformation of precipitation into available water resources, and alleviate the conflict between increase food production and freshwater scarcity. However, the processes of soil water movement and salt migration might be altered, because utilization of brackish water results in frequent changes in groundwater depth and thickness of vadose zone. Thus, it was necessary to understand soil water movement and salt migration when using brackish water for irrigation.

Materials and methods

In this study, soil matric potential (SMP) and total dissolved solids (TDS) at multiple depths were measured in situ to investigate the mechanisms of soil water movement and salt migration at one grassland (site 1) and at three typical irrigated croplands (sites 2, 3, and 4) with different soil textures and groundwater depths in a lowland area of the NCP.

Results and discussion

The study showed that deep soil water and groundwater were recharged generally following heavy precipitation during rainy season. SMP values increased quickly at site 4 due to relatively homogeneous soils, followed by site 3?>?site 2?>?site 1 with an obvious hysteresis response of SMP at multiple depths to precipitation. Soil water mainly moved downward in piston flow, and preferential flow also existed in the soil above 100 cm in the percolation process at four sites. Generally, SMP values followed the order of site 4?>?site 1?>?site 2?>?site 3 and exhibited an inverse trend for TDS, which was mainly due to soil heterogeneity and soil texture in vertical profiles. The differences in SMP among the four sites were mainly due to land use and groundwater depth. There were significantly differences in spatiotemporal distribution of water and salts between homogenous and heterogeneous soils. The processes of infiltration and water redistribution ended quickly in relatively homogeneous soils after heavy rains. However, there was obvious hysteresis in SMP with an increase in soil depth in heterogeneous soils.

Conclusions

Homogenous soils favored water infiltration, salt leaching, and groundwater recharge, and the flow of soil water flow was blocked and salt accumulated significantly in layered soils. The soil water movement and the transformation relationship between water and salt in the vadose zone provided a basis for utilization of brackish water irrigation in lowland region of the NCP.

     

Groundwater Contribution of Metals from an Abandoned Mine to The North Fork of The American Fork River, Utah

Surface water discharge measurements and metals concentrations in the North Fork of the American Fork River, Utah, its tributaries, and the groundwater in the vicinity of the Pacific Mine were used to evaluate the impact of groundwater on loading rates of metals and As to the river. Fish in the river contain As, Cd, and Pb at concentrations that are hazardous to human health if consumed. The results suggest that dissolved As, Cd, Cu, Fe, Mn, Pb, and Zn enter the river when it is a gaining stream. However, the suspended metals load is significantly greater than the dissolved load, and generally decreases through the reach of river adjacent to the mine site. Cadmium and Mn travel as dissolved species while Cu, Fe, Pb, and Zn travel as suspended solids. Arsenic seems to travel both with the suspended solids and in the dissolved state. The geochemical modeling program PHREEQC and a diffuse double layer surface complexation model were used to investigate the chemical controls on metals mobility and attenuation in the surface and groundwaters at the site. Based on the PHREEQC results, the most important process in these waters is the precipitation of ferrihydrite, also referred to as hydrous ferric oxide (HFO). Copper, Pb, most importantly Zn, and to a lesser degree As sorb to HFO.     

Polycyclic Aromatic Hydrocarbons (PAHs) Slurry Phase Bioremediation of a Manufacturing Gas Plant (MGP) Site Aged Soil

Bench scale tests have been carried out in order to investigatebioremediation feasibility of a Manufacturing Gas Plant site(Bovisa Gasometri – MI – I) aged soil, highly contaminated bypolyaromatic hydrocarbons (PAHs) and mineral oils. Biodegradationstudies were carried out at 22 °C in a slurry system reactor, with a solid to liquid ratio of 10% w/w. Three testswere performed, over a period of 23, 24 and 91 days respectively.In the first test, only soil and water were put into the system.In the second test, microbial activity was inhibited to evaluatethe amount of abiotic losses. In the third test, macronutrientswere added to the reactor; bioaugmentation was also carried outby an inoculum of autochthonous PAH-degrading microorganisms. Saturated hydrocarbons, PAHs, transformation products, heterotropic and PAH-degrading bacteria and fungi were monitored.Tests showed that high removal efficiency could be obtained following 23 days of treatment for all PAHs, including high molecular weight compounds. Abiotic losses were an importantprocess contributing to concentration abatement in soil, especially in the first phase of the treatment. Lag time lackfor all polyaromatic hydrocarbons revealed that autochthonousmicroorganisms were well adapted to these contaminants; bioaugmentation did not seem to speed up the process. The higherremoval rate and efficiency for high molecular weight PAHs obtained in the third test suggested that nutrient addition could play an important role in the biodegradation process ofthese compounds, whereas it did not significantly modify total(abiotic + biotic) removal of light compounds.     

Source Treatment of Acid Mine Drainage at a Backfilled Coal Mine Using Remote Sensing and Biogeochemistry

A biological source treatment (BST) technique using remote sensing and biogeochemistry has been developed to address acid mine drainage (AMD) at its source. The BST technique utilizes down-hole injections of microbial inoculum and substrate amendments to establish a biofilm on the surface of metal sulfides (AMD source material). The treatment results in an elevated groundwater pH (from acidic to circum-neutral levels) and prevents further oxidation of AMD source material. The first 2 years of an ongoing field study of the BST technique at a reclaimed coal mine in central Tennessee (USA) has produced successful results. For instance, the water chemistry in a monitoring well down-gradient from injection wells has improved substantially as follows: the pH increased 1.3 units from 5.7 to 7.3, the dissolved (0.45 µm-filtered) iron concentration decreased by 84% from 93 to 15 mg/l, the conductivity decreased by 379 µS/cm, and sulfate decreased by 78 mg/l. Electromagnetic induction surveys were conducted to identify AMD source material and monitor BST performance by measuring changes in subsurface resistivity throughout the site. These surveys revealed a treatment zone created between injection wells where the resistance of contaminated groundwater from up-gradient AMD sources increased as it flowed past injection wells, thus, suggesting this technique could be used to treat AMD sources directly or to intercept and neutralize sub-surface AMD.     

Effect of Fluctuating Hydrological Conditions on the Mobility of Heavy Metals in Soils of a Freshwater Estuary in the Netherlands

The objective of this study was to measure the mobility of heavy metals in freshwater estuary soils that are seasonally inundated and to characterize the distribution of sulfide precipitates in these soils. Precipitation and dissolution of labile sulfides may account for changing pore water concentrations of heavy metals in freshwater wetland soils that are subject to temporary flooding or fluctuating groundwater levels. The presence of authigenic zinc- and iron-(mono)sulfide in this type of soils during periods with a high groundwater level was demonstrated by electron microprobe analyses. Because sulfide precipitates are strongly associated with root remnants, fresh soil organic material may be an important intermediary in the sulfur cycling and, consequently, in the behavior of heavy metals in these freshwater soils. Oxidation of labile sulfides may be partly responsible for the increased zinc and sulfate concentrations in the pore water during periods with low groundwater levels. Heavy metals may also be mobilized by degradation of their host phase organic matter during periods with high biodegradation.     

Non-additive effects of mixing different sources of dissolved organic matter on its biodegradation

To examine the potential impact of plant species richness on ecosystems, we studied non-additive effects of different plant litters on the biodegradation rate of dissolved organic matter (DOM) when mixing plant leaf-derived DOM derived from different plant species. A full factorial biodegradation experiment (31 possible singular and multiple combinations of five litter type-derived DOM sources) was conducted using plant litters from the five most abundant plant species in a subtropical watershed ecosystem, from which dissolved organic carbon (DOC) disappearance was measured. Loss of DOC over time was considered biodegradable DOC. We tested whether DOM diversity, measured as source species richness and composition, would affect biodegradation rates. Overall, we found significant non-additive (synergistic) effects of DOM diversity on biodegradation rates of DOM, which were explained both by plant species richness and composition. Across all treatments, a significantly higher biodegradation rate was correlated with the presence of DOM from higher nitrogen (N) containing plant litters; conversely, the presence of lower N decreased these rates. The N content and chemical characteristic of DOM might influence the magnitude of the synergistic effect. Our results suggest that loss of plant litter species diversity would not affect DOC biodegradation rate, provided that at least two species are conserved. However, the variability in DOC biodegradation rate across the treatments decreased with increased DOM diversity at three incubation time points. Our results also indicate that in an ecosystem with low plant biodiversity, loss of key species such as Lophostemon confertus could reduce the synergistic effects on DOC biodegradation rate.     

Uptake of Hydrocarbon by Pseudomonas fluorescens (P1) and Pseudomonas putida (K1) Strains in the Presence of Surfactants: A Cell Surface Modification

The objective of this research was the evaluation of the effects of exogenous added surfactants on hydrocarbon biodegradation and on cell surface properties. Crude oil hydrocarbons are often difficult to remove from the environment because of their insolubility in water. The addition of surfactants enhances the removal of hydrocarbons by raising the solubility of these compounds. These surfactants cause them to become more vulnerable to degradation, thereby facilitating transportation across the cell membrane. The obtained results showed that the microorganism consortia of bacteria are useful biological agents within environmental bioremediation. The most effective amongst all, as regards biodegradation, were the consortia of Pseudomonas spp. and Bacillus spp. strains. The results indicated that the natural surfactants (rhamnolipides and saponins) are more effective surfactants in hydrocarbon biodegradation as compared to Triton X-100. The addition of natural surfactants enhanced the removal of hydrocarbon and diesel oil from the environment. Very promising was the use of saponins as a surfactant in hydrocarbon biodegradation. This surfactant significantly increases the organic compound biodegradation. In the case of those surfactants that could be easily adsorbed on cells of strains (e.g., rhamnolipides), a change of hydrophobicity to ca. 30-40% was noted. As the final result, an increase in hydrocarbon biodegradation was observed.     

Determination of effective release rates of polycyclic aromatic hydrocarbons and dissolved organic carbon by column outflow experiments

Risk assessment of groundwater pollution requires quantitative information on the release kinetics of pollutants and organic matter from contaminated soil. We applied a new experimental design for column outflow experiments to investigate the release of polycyclic aromatic hydrocarbons (PAHs) and dissolved organic matter under water-saturated flow conditions. We used materials originating from a soil contaminated with non-aqueous phase liquids. To distinguish between release at equilibrium and release limited by mass transfer, we used two flow velocities and multiple interruptions to the flow. We quantified release and transport parameters by inverse numerical simulation of the individual breakthrough curves, applying a model based on the advection–dispersion equation including non-equilibrium and non-linear sorption. Release of the dissolved organic C takes place in two steps. Initially, a large amount of readily available organic matter is released. This first flush is followed by an outflow with typical characteristics of rate-limited release: larger concentrations in slower flow and increased concentrations after interruptions. The breakthrough of PAHs responds neither to the different flow velocities nor to the interruptions. We hypothesize that release of PAHs from the contaminated material is governed by dissolution at equilibrium according to Raoult's law. The boundary conditions of the experimental design, i.e. the flow velocities and multiple interruptions, enable us to distinguish between release at equilibrium and that which is rate-limited. Also, the response of the breakthrough behaviour to the boundary conditions can be used to estimate inversely effective release parameters.