Remediation of Weathered Light Nonaqueous Phase Liquids by Persulfate: In-Situ Performance Assessment and Numerical Modeling

Light nonaqueous phase liquids (LNAPLs) petroleum hydrocarbons (PHCs) subsurface contamination is complex and poses considerable risks to human health and the environment. The PHC contaminated sites are often difficult to access and remediate due to subsequent changes in composition and distribution of bulk LNAPL mass following the release. The cleanup process becomes even more challenging as the released product ages and leaves behind several weathered residual LNAPL blobs and ganglia that are heterogeneously distributed in the soil pores within the smear zone. The selection of a suitable remedial program is based on bench-scale treatability studies, and the duration of the program relies heavily on time-consuming, labor-intensive, and, therefore, expensive monitoring activities. In situ chemical oxidation (ISCO) using persulfate has been increasingly recognized as one of the most feasible and reliable tools for remediation of PHC contaminated sites. Despite this recognition, there is no modeling approach available that can capture a persulfate ISCO remediation system behavior, evaluate its efficiency and effectiveness, and assist with design optimization. Existing models that can estimate the efficiency of an ISCO remediation are greatly dependent on the availability of LNAPL mass, composition, architecture, and interphase mass transfer rate data. In reality, however, it is difficult, if not impossible, to determine many of these parameters at a weathered PHC contaminated site. The focus of the research was on developing a combined bench-scale and numerical modeling framework to assist with describing and capturing the persulfate ISCO system during the remediation activities of heavily weathered LNAPL PHC contaminated sites. A series of bench-scale experiments were designed and implemented to support the development of a numerical model. Aquifer material was collected from a heavily weathered diesel contaminated site (Site). Since a common feature of the gas chromatography analysis of a heavily weathered PHC is the presence of an unresolved complex mixture (UCM) of components, pseudocomponents F2 and F3, based on PHC fractions, were defined to estimate fundamental kinetic data. Aqueous phase treatability studies were performed using a series of well-mixed batch reactors to provide information on the ability of various persulfate systems (unactivated, citric acid chelated-ferrous activated, and alkaline activated persulfate) to degrade pseudocomponents F2 and F3 detected in the Site groundwater. Two concentrations of persulfate (40 and 80 g.L-1) and two different persulfate activators (alkaline and citric acid chelated ferrous) at a persulfate concentration of 40 g.L-1 were evaluated for the weathered diesel fuel contaminated groundwater. The pH of ~12 in alkaline activation of persulfate resulted in the highest reduction of ~99% LNAPL mass in groundwater. Chemical kinetic parameters of the aqueous treatment studies were estimated using a numerical approach in the modeling of soil columns. The alkaline activated and unactivated persulfate systems at a persulfate concentration of 40 g.L-1 were selected for remediation of the contaminated soil using the flow interruption column method with multiple persulfate injections. The LNAPL mass reduction of ~50% and 80% for unactivated and alkaline activated systems, respectively, were achieved. The observed data were used to develop an explanatory and practically useful model considering dissolution, advective–dispersive transport, and complex oxidation reactions occurring in porous media during ISCO remediation. The simulations showed that after two persulfate injections, the LNAPL mass reduction was limited by the dissolution process, and no further mass reduction occurred upon additional exposure to more persulfate. A Site-specific action plan was developed to scale up the bench-scale research to a pilot-scale for a demonstration study, where research data and findings in the laboratory were tested and evaluated under field conditions. A pilot area was selected at a historical Site with a weathered diesel fuel contaminated aquifer manifested as residual sources in soil and dissolved phase in groundwater. A comprehensive monitoring infra-structure was installed. In this unique pilot-scale experiment, the selected area was divided into three zones of treatment (TTZ), control (CZ), and a buffer area in between the TTZ and CZ. Two injection episodes were conducted at the pilot area. The unactivated persulfate system (or municipal water at CZ) was introduced into the subsurface of the treatment zone at locations/depths of PHCs impacts identified with laser-induced fluorescence (LIF) equipped with an ultra-violet optical screening tool (UVOST™) to maximize the opportunity of persulfate to degrade the dissolved F2 and F3 pseudocomponents. No injection activity was conducted at the buffer zone. The dissolved PHCs mass flux was monitored downstream of the pilot area across a transverse fence-line at 60 multilevel sampling points pre- and post-injection episodes. In general, the pilot test data indicate that the aqueous mass of F2 and F3 decreased following each injection episode; however, both the TTZ and CZ showed a similar decrease. Considering the lack of persulfate presence during 3-week monitoring in the post-injection samples collected from the CZ, oxidation of F2 and F3 in the CZ area with persulfate seems unlikely. One potential explanation can be that the injection of water caused a displacement of the dissolved phase and perhaps any mobile nonaqueous phase liquid. Another likely reason is that by injecting uncontaminated water into this area, oxygen was also supplemented to the subsurface and encouraged microbial activities. Generally, it is believed that oxygen is present within the smear zone, and given the age of this contaminated Site (~70 years), it is expected that aerobic bioremediation had long reached its operational limits. However, the latter explanation is in agreement with the results of groundwater treatment tests in control batch reactors in the absence of persulfate. The soil samples were collected and analyzed pre-injection activities, and after completion of the injection, Episode 2 corresponding to nearby LIF elevated response data. Since the places that persulfate can reach during injection are mainly unknown, the post-injection soil samples were collected from ~0.5 m above to ~0.5 m below the depths that pre-injection core samples were collected. The values in the post-injection column are the average of concentrations F2 and F3 in the soil samples that were collected within the intervals mentioned above. Overall, collected soil samples within the TTZ showed a decrease of ~50% in F2 and F3. Samples collected from CZ showed higher concentrations of F2 and F3 compared to pre-injection samples. This observation is not uncommon in the field because of the heterogeneity in contaminant distributions. However, since the overall 50% decrease in contaminant in soil was observed in TTZ, it can be concluded that the two injection episodes at the pilot-scale area were successful and generally in agreement with model simulation results

Evaluation of gas phase air cleaners for indoor environmental applications

While granular activated carbon (GAC) filters have been used extensively for removal of contaminants from industrial gas streams, little research has been done on their adsorption capacity for indoor environmental purposes where ventilation systems are used to remove volatile organic compounds (VOC) contaminants and may allow higher air recirculation. This research investigates the performance of GAC filters for indoor environments by challenging them with various VOCs and subsequently measuring their removal efficiencies and breakthrough times. A small environmental, closed-loop, dynamic test chamber was designed, constructed and used to measure the performance of eight different GAC filter samples when they were exposed to cyclohexane, ethyl acetate and toluene at different humidity levels. Three of the filters were composed of virgin activated carbon with granules of different sizes and/or shapes. The remainder filters were impregnated with either phosphoric acid or potassium hydroxide. The breakthrough times and removal efficiencies of the filters were analyzed. Within the concentration range examined and at 50% relative humidity (RH), toluene exhibited the highest adsorption capacity on the filters, followed by ethyl acetate and cyclohexane. At 50% RH, the virgin filters were 25% more efficient in adsorbing the VOCs than the impregnated ones. For toluene, the 50% breakthrough times of filters 1A, 1B and 1C were 4, 0.13 and 0.03 hours, respectively, and the 80% breakthrough times were 5.60, 1.03 and 0.50 hours. respectively. The effects of RH on adsorption of soluble (ethyl acetate) and insoluble (cyclohexane and toluene) VOCs on the performance of GAC filters were also investigated. The presence of water vapor in the chamber had little effect on the adsorption capacity of the toluene until about 50% RH. At 50% RH and above, an increase of 16.5% in adsorption capacity of ethyl acetate occurred, while the adsorption capacity of cyclohexane and toluene rapidly decreased. The 80% breakthrough times of filters IA, 2A and 3A for toluene decreased on average, up to 33%. 38% and 25%, respectively, when the RH increased from 30% to 70%. Therefore, competitive adsorption of VOCs with water vapor molecules shortened the breakthrough times of the filters for toluene and cyclohexane as the RH level increased

Surgical Management of Necrotizing Pancreatitis

Pancreatic necrosis is a highly morbid condition. It is most commonly associated with severe, acute pancreatitis, but can also be caused by trauma or chronic pancreatitis. Once diagnosed, management of pancreatic necrosis begins with supportive care, with an emphasis on early, and preferably, enteral nutrition. Intervention for necrosis, sterile or infected, is dictated by patient symptoms and response to conservative management. When possible, intervention should be delayed to allow the necrotic collection to form a capsule. First-line treatment for necrosis is with percutaneous drainage or endoscopic, transmural drainage. These strategies can be effective as monotherapy, but the need for repeated interventions, or for progression to more invasive interventions, is not uncommon. Necrosectomy may be performed using a previously established drainage tract, as in percutaneous endoscopic necrosectomy (PEN), video-assisted retroperitoneal debridement (VARD), and direct endoscopic necrosectomy (DEN). Although outcomes for these minimally-invasive techniques are better than for traditional necrosectomy, both laparoscopic and open techniques remain important for patients with extensive disease that cannot otherwise be adequately treated. This is especially true when pancreatic necrosis is complicated by disconnected pancreatic duct syndrome (DPDS), where necrosectomy remains standard of care

PIP3-Independent Activation of TorC2 and PKB at the Cell's Leading Edge Mediates Chemotaxis

SummaryBackgroundStudies show that high phosphotidylinositol 3,4,5-trisphosphate (PIP3) promotes cytoskeletal rearrangements and alters cell motility and chemotaxis, possibly through activation of protein kinase Bs (PKBs). However, chemotaxis can still occur in the absence of PIP3, and the identities of the PIP3-independent pathways remain unknown.ResultsHere, we outline a PIP3-independent pathway linking temporal and spatial activation of PKBs by Tor complex 2 (TorC2) to the chemotactic response. Within seconds of stimulating Dictyostelium cells with chemoattractant, two PKB homologs, PKBA and PKBR1, mediate transient phosphorylation of at least eight proteins, including Talin, PI4P 5-kinase, two Ras GEFs, and a RhoGap. Surprisingly, all of the substrates are phosphorylated with normal kinetics in cells lacking PI 3-kinase activity. Cells deficient in TorC2 or PKB activity show reduced phosphorylation of the endogenous substrates and are impaired in chemotaxis. The PKBs are activated through phosphorylation of their hydrophobic motifs via TorC2 and subsequent phosphorylation of their activation loops. These chemoattractant-inducible events are restricted to the cell's leading edge even in the absence of PIP3. Activation of TorC2 depends on heterotrimeric G protein function and intermediate G proteins, including Ras GTPases.ConclusionsThe data lead to a model where cytosolic TorC2, encountering locally activated small G protein(s) at the leading edge of the cell, becomes activated and phosphorylates PKBs. These in turn phosphorylate a series of signaling and cytoskeletal proteins, thereby regulating directed migration

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Macropinocytosis is a fundamental mechanism that allows cells to take up extracellular liquid into large vesicles. It critically depends on the formation of a ring of protrusive actin beneath the plasma membrane, which develops into the macropinocytic cup. We show that macropinocytic cups in Dictyostelium are organised around coincident intense patches of PIP3, active Ras and active Rac. These signalling patches are invariably associated with a ring of active SCAR/WAVE at their periphery, as are all examined structures based on PIP3 patches, including phagocytic cups and basal waves. Patch formation does not depend on the enclosing F-actin ring, and patches become enlarged when the RasGAP NF1 is mutated, showing that Ras plays an instructive role. New macropinocytic cups predominantly form by splitting from existing ones. We propose that cup-shaped plasma membrane structures form from self-organizing patches of active Ras/PIP3, which recruit a ring of actin nucleators to their periphery

Finding a satisfying assignment for planted NAE-E3-SAT using a voting style algorithm

A random planted formula is constructed by fixing a certain planted assignment to the variables, and then adding only clauses that are satisfied by the planted assignment. The purpose of such approach is to generate a random-like formula that is guaranteed to have a satisfying assignment. The random planted 3-SAT has received significant attention. In particular, it has been shown that when containing sufficiently many clauses, it is solvable with high probability in polynomial time. In this work we obtain a similar result for the random planted Not-All-Equal-SAT problem, which is defined in the same way except that the clauses added are the Not-All-Equal clauses. We follow one of the aforementioned approaches by Krivelevich and Vilenchik. In the case of NAE-SAT the first step, voting, makes no sense. We show that the same result can be achieved by solving the MAX-CUT problem in the co-occurrence graph of the formula

Partitioning of the response to cAMP via two specific Ras proteins during Dictyostelium discoideum development

Following starvation, Dictyostelium discoideum cells aggregate, a response that requires chemotaxis to cyclic AMP (cAMP) and the relay of the cAMP signal by the activation of adenylyl cyclase (ACA). Insertional inactivation of the rasG gene resulted in delayed aggregation and a partial inhibition of early gene expression, suggesting that RasG does have a role in early development. When the responses of rasG⁻ cells to cAMP were compared with the responses of rasC⁻ strain, these studies revealed that signal transduction through RasG is more important in chemotaxis and early gene expression, but that signal transduction through RasC is more important in ACA activation. Characterization of a rasC⁻/rasG⁻ mutant revealed that both cAMP chemotaxis and adenylyl cyclase (ACA) activation were negligible in this strain. The ectopic expression of carA from the actin 15 promoter restored early developmental gene expression to the rasC⁻/rasG⁻ strain, rendering it suitable for an analysis of cAMP signal transduction. Since there was negligible signaling through either the cAMP chemotactic pathway or the adenylyl cyclase activation pathway in this strain, it is clear that RasG and RasC are the only two Ras subfamily proteins that directly control these pathways. The mutational analysis of Switch I and Switch II regions also defined the key residues that generate functional differences between RasC and RasG. Rap1 is also activated in response to cAMP but its position in the signal transduction cascade was clarified by the finding that its activation was totally abolished in rasC⁻/rasG⁻/[act15]:carA and in rasG⁻ cells, but only slightly reduced in rasC⁻ cells. The finding that in vitro guanylyl cyclase activation is also abolished in the rasC/rasG⁻4act15]:carA strain identifies RasG⁻/RasC⁻ as the presumptive monomeric GTPases required for this activation. The phenotypes of the vegetative ras null mutants were also examined. The results indicate that RasG plays an important role in cytokinesis. The partial absence of chemotaxis to folate in rase cells compared to the total absence of chemotaxis to folate in rasC⁻/rasG⁻, and rasC⁻/rasG⁻/[act15]:carA cells suggests a compensatory role of RasC for RasG during this process, a similar phenomenon to that observed for cAMP chemotaxis by aggregating cells.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat