A new lattice Boltzmann model for interface reactions between immiscible fluids

In this paper, we describe a lattice Boltzmann model to simulate chemical reactions taking place at the interface between two immiscible fluids. The phase-field approach is used to identify the interface and its orientation, the concentration of reactant at the interface is then calculated iteratively to impose the correct reactive flux condition. The main advantages of the model is that interfaces are considered part of the bulk dynamics with the corrective reactive flux introduced as a source/sink term in the collision step, and, as a consequence, the model’s implementation and performance is independent of the interface geometry and orientation. Results obtained with the proposed model are compared to analytical solution for three different benchmark tests (stationary flat boundary, moving flat boundary and dissolving droplet). We find an excellent agreement between analytical and numerical solutions in all cases. Finally, we present a simulation coupling the Shan Chen multiphase model and the interface reactive model to simulate the dissolution of a collection of immiscible droplets with different sizes rising by buoyancy in a stagnant fluid

Experimental studies of self-sustaining thermal aquifer remediation (STAR) for non-aqueous phase liquid (NAPL) sources

Self-sustaining Thermal Aquifer Remediation (STAR) is a novel technology that employs smouldering combustion for the remediation of subsurface contamination by non-aqueous phase liquids (NAPLs). Smouldering is a form of combustion that is slower and less energetic than flaming combustion. Familiar examples of smouldering involve solid fuels that are destroyed by the reaction (e.g., a smouldering cigarette or peat smouldering after a wildfire). In STAR, the NAPL serves as the fuel within an inert, porous soil medium. Results from experiments across a range of scales are very promising. Detailed characterisation has focused on coal tar, a common denser-than-water NAPL (DNAPL) contaminant. Complete remediation is demonstrated across this range of scales. Visual observations are supported bychemical extraction results. Further experiments suggest that STAR can be self-sustaining, meaning that once ignited the process can supply its own energy to propagate. Costly energy input is reduced significantly. Comparison of large scale to small scale laboratory experiments, a volume increase by a factor of 100, suggests that STAR process efficiency increases with scale. This increase in efficiency results from reduced heat losses at larger scales while maximum the temperature achieved by STAR is unaffected. The research also demonstrates the controllability of STAR, where the termination of airflow to the reaction terminates the STAR process. The scale-up process provides important guidance to the development of full scale STAR for ex situ remediation of NAPL-contaminated soil

The many roads to psychosis: recent advances in understanding risk and mechanisms.

Schizophrenia is a chronic and severe mental illness which frequently leads to substantial lifelong disability. The past five years have seen major progress in our understanding of the complex genetic architecture of this disorder. Two major barriers to understanding the core biological processes that underlie schizophrenia and developing better interventions are (1) the absence of etiologically defined biomarkers and (2) the clinical and genetic heterogeneity of the disorder. Here, we review recent advances that have led to changes in our understanding of risk factors and mechanisms involved in the development of schizophrenia. In particular, mechanistic and clinically oriented approaches have now converged on a focus on disruptions in early neurodevelopment and synaptic plasticity as being critical for both understanding trajectories and intervening to change them. Translating these new findings into treatments that substantively change the lives of patients is the next major challenge for the field

Locating NAPLs in Ground Water Using Partitioning Fluorescent Dyes

A major challenge in ground water remediation is locating nonaqueous phase liquids (NAPLs). Partitioning tracers can be used to identify NAPL sources between injection and extraction wells. NAPLs are only slightly soluble in water, pose a long-term source of groundwater contamination, and can be difficult to remove. The complexity of recovery processes requires the development of new technologies that guarantee cost effective methods for locating and quantifying NAPLs. Traditional methods like soil coring have been inefficient since they underestimate the quantity of NAPLs and are expensive. Partitioning tracer tests are some of the most recent methods developed for locating these contaminants and determining the volume of the NAPL present in the inter-well zone. The results of the tests can be used to develop remediation techniques to recover NAPLs entrapped in the contaminated zone. Fluorescent dyes may be useful as partitioning tracers. They can be analyzed quickly at the field site, resulting in a shorter analysis time and lower costs than other partitioning tracers. This project pursued the selection of suitable tracers and the development of partitioning tracer techniques to locate and quantify NAPLs in the subsurface

Effect of varying the rate of partitioning of phenanthrene in nonaqueous-phase liquids on biodegradation in soil slurries

A study was conducted to determine the influence of varying the rates of partitioning of phenanthrene from nonaqueous-phase liquids to water on its biodegradation. Partitioning rates from dibutyl phthalate and 2,2,4,4,6,8,8-heptamethylnonane were rapid in slurries of soil or aquifer solids that were shaken and were affected by the identity and volume of the non-aqueous-phase liquid. Concentrations of the surfactant Alfonic 810-60 that increased partitioning inhibited biodegradation. The rates of mass transfer from the phthalate to water were not influenced by the identity of the environmental sample. Although the rate of mass transfer of phenanthrene did not limit its mineralization by microorganisms in the soil or aquifer solids, treatments that increased the rate of partitioning enhanced biodegradation, presumably because the treatment overcame some other factor that limited degradation of the hydrocarbon.Peer Reviewe

Mapping the storing and filtering capacity of European soils

The purpose of the current study was to develop an estimation method based on available soil map information (categorical data) and thereafter estimate and map across Europe the soil filtering and storing capacity of different substances, which support ecosystem services and those which present a hazard to the ecosystem functioning. Pollutants were grouped as follows: (1) elements in cationic form; (2) elements in anionic form; (3) solids and pathogenic microorganisms; (4) non-polar organic chemicals and (5) nonaqueous phase liquids (NAPLs). The spatial pattern of areas with high soil storing capacity are largely different depending on the stored substances. In general, those soils are characterized by good storing capability that have thick topsoil and subsoil layers and these layers are free from the effects of groundwater. As the content of clay and humus content increases and the stone or gravel content decreases, the storage capacity increases simultaneously. However, the effect of soil pH and the soil mineralogy is different depending on the various groups of pollutants (e.g. the calcareous soils with high swelling clay mineral content are able to bind more cations, whereas the acidic soils or the soils with high sesquioxide content have higher anion storing capacity). The soil filtering capacity pattern of Europe in the case of different groups of substances are in part similar to the storing capacity pattern. The main difference between the two parameters was to take account of infiltration rate and the thickness of the filtration path up to the groundwater during the filtering capacity estimation.JRC.D.3-Land Resource

Small-scale forward smouldering experiments for remediation of coal tar in inert media

This paper presents a series of experiments conducted to assess the potential of smouldering combustion as a novel technology for remediation of contaminated land by water-immiscible organic compounds. The results from a detailed study of the conditions under which a smouldering reaction propagates in sand embedded with coal tar are presented. The objective of the study is to provide further understanding of the governing mechanisms of smouldering combustion of liquids in porous media. A small-scale apparatus consisting of a 100 mm in diameter quartz cylinder arranged in an upward configuration was used for the experiments. Thermocouple measurements and visible digital imaging served to track and characterize the ignition and propagation of the smouldering reaction. These two diagnostics are combined here to provide valuable information on the development of the reaction front. Post-treatment analyses of the sand were used to assess the amount of coal tar remaining in the soil. Experiments explored a range of inlet airflows and fuel concentrations. The smouldering ignition of coal tar was achieved for all the conditions presented here and self-sustained propagation was established after the igniter was turned off. It was found that the combustion is oxygen limited and peak temperatures in the range 800-1080 °C were observed. The peak temperature increased with the airflow at the lower range of flows but decreased with airflow at the higher range of flows. Higher airflows were found to produce faster propagation. Higher fuel concentrations were found to produce higher peak temperatures and slower propagation. The measured mass removal of coal tar was above 99% for sand obtained from the core and 98% for sand in the periphery of the apparatus

Laboratory and numerical simulations of light nonaqueous phase liquid (LNAPL) in unsaturated zone

The contamination of hydrocarbons in soil and groundwater by fuels and industrial chemicals has become a problem of growing concern. The contaminated groundwater is not only unsafe for human and animal consumption but also not suitable for irrigation purposes. The leaking from underground storage tanks (USTs) and pipelines, hazardous waste sites and surface spills are the general sources of nonaqueous phase liquids (NAPLs). The NAPLs is a common term used in hydrogeology to describe the immiscible, separate liquids phase when in contact with water and/or air that occurred in subsurface environment. These liquids typically have different density and viscosity than water (Charbeneau, 2000). A NAPL with a density less than water is classified as light nonaqueous phase liquid (LNAPL), and a NAPL denser than water is classified as dense nonaqueous phase liquid (DNAPL)

Field validation of radon monitoring as a screening methodology for NAPL-contaminated sites

Screening methodologies aim at improving knowledge about subsurface contamination processes before expensive intrusive operations, i.e. drilling and core-sampling, well installation and development, sampling of groundwater and free-phase product, are implemented. Blind field tests carried out at a hydrocarbon storage and distribution center in NE Spain suggest that Rn monitoring can be effectively used to locate the boundaries of subsurface accumulations of NAPLs. Sixty seven measurements of Rn in soil air were performed with a SARAD RTM 2100 current-ionization alpha-particle spectrometer following a 10 m square grid. Reductions of 222Rn concentration above a pool of LNAPL due to the preferential partition of Rn into the organic phase were spatially analyzed and resolved to yield the surface contour of the NAPL source zone. This surface trace of the source zone agreed well with the extent and situation inferred from measurements of free-phase thickness taken at eight monitoring wells at the site. Moreover, the good repeatability (as measured by replicate measurements at the same sampling point) and spatial resolution of the technique suggest that the boundaries of the plume can be delineated at the sub-decametre level