The Spread of Emerging Contaminants in the Soil-Groundwater System

In recent years the risks of emerging contaminants (ECs) have received substantial attention as potential environmental pollutants that persist in the environment due to their continual release. This research presents the work of three studies that provide critical insight into the spread of ECs, particularly antibiotic resistant bacteria derived from dairy manure and potentially harmful particles originated from nanomaterials in the soil-groundwater system. The adhesion of particles to mineral surfaces was quantified with the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory that includes Lifshitz-van der Waals, Lewis acid-base, electrostatic double layer and steric repulsion interactions. The transport of ECs was conducted in column transport experiments and the quartz sands served as the porous media. The first study specifically evaluated the effects of outer membrane protein (OMP) TolC on the transport of E.coli within saturated sands. The results showed that OMP TolC altered the surface tension components of E.coli cells which eventually led to higher mobility when the ionic strength was 20 mM or higher, suggesting that antibiotic resistant bacteria expressing OMP TolC could spread more widely within sandy aquifers. The second study evaluated the transport of manure-derived tetracycline resistant (tetR) and susceptible (tetS) E.coli in unsaturated porous media with specific focus on pore-water chemistry and moisture content. The experimental results showed that under both high and low soil moisture content terms, tetR E.coli displayed higher mobility than tetS E. coli under higher ionic strength conditions. An increase in soil moisture content from 0.12 to 0.23 as well as decrease in ionic strength of solution led to minimal release of previously retained E. coli cells. A transport model was fitted to the experimental results using the computer program HYDRUS-1D. The third study detailed deposition and remobilization of graphene oxide (GO) nanoparticles within saturated sands. The kinetics of GO was examined as a function of ionic strength and the remobilization of previously retained GO particles was investigated via chemical perturbation. The results revealed that deposition of GO particles on the surface of the quartz sands was highly dependent on ionic strength while the retention was limited by GO particles deposition capacities. The results of chemical perturbation suggested that GO particles could be remobilized in aqueous environment. The combined results from these three studies highlight the potential of ECs being spread in the soil-groundwater system and therefore pose serious public health risks

Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review

Environmental applications of nanoparticles (NP) increasingly result in widespread NP distribution within porous media where they are subject to various concurrent transport mechanisms including irreversible deposition, attachment/detachment (equilibrium or kinetic), agglomeration, physical straining, site-blocking, ripening, and size exclusion. Fundamental research in NP transport is typically conducted at small scale, and theoretical mechanistic modeling of particle transport in porous media faces challenges when considering the simultaneous effects of transport mechanisms. Continuum modeling approaches, in contrast, are scalable across various scales ranging from column experiments to aquifer. They have also been able to successfully describe the simultaneous occurrence of various transport mechanisms of NP in porous media such as blocking/straining or agglomeration/deposition/detachment. However, the diversity of model equations developed by different authors and the lack of effective approaches for their validation present obstacles to the successful robust application of these models for describing or predicting NP transport phenomena. This review aims to describe consistently all the important NP transport mechanisms along with their representative mathematical continuum models as found in the current scientific literature. Detailed characterizations of each transport phenomenon in regards to their manifestation in the column experiment outcomes, i.e., breakthrough curve (BTC) and residual concentration profile (RCP), are presented to facilitate future interpretations of BTCs and RCPs. The review highlights two NP transport mechanisms, agglomeration and size exclusion, which are potentially of great importance in controlling the fate and transport of NP in the subsurface media yet have been widely neglected in many existing modeling studies. A critical limitation of the continuum modeling approach is the number of parameters used upon application to larger scales and when a series of transport mechanisms are involved. We investigate the use of simplifying assumptions, such as the equilibrium assumption, in modeling the attachment/detachment mechanisms within a continuum modelling framework. While acknowledging criticisms about the use of this assumption for NP deposition on a mechanistic (process) basis, we found that its use as a description of dynamic deposition behavior in a continuum model yields broadly similar results to those arising from a kinetic model. Furthermore, we show that in two dimensional (2-D) continuum models the modeling efficiency based on the Akaike information criterion (AIC) is enhanced for equilibrium vs kinetic with no significant reduction in model performance. This is because fewer parameters are needed for the equilibrium model compared to the kinetic model. Two major transport regimes are identified in the transport of NP within porous media. The first regime is characterized by higher particle-surface attachment affinity than particle-particle attachment affinity, and operative transport mechanisms of physicochemical filtration, blocking, and physical retention. The second regime is characterized by the domination of particle-particle attachment tendency over particle-surface affinity. In this regime although physicochemical filtration as well as straining may still be operative, ripening is predominant together with agglomeration and further subsequent retention. In both regimes careful assessment of NP fate and transport is necessary since certain combinations of concurrent transport phenomena leading to large migration distances are possible in either case

Interpretacja geometryczna zróżnicowania typów skał w przestrzeni Hilberta

Signal of vibrations accompanying the rotary drilling of three rock types (andesite, limestone and granite) by diamond core-drill bits was processed and evaluated in order to track the signal characteristics of tested rock types. Mathematical procedures of Hilbert’s abstract space were applied to express the differences between the rock types based on vibration signal. Experiments were performed using the laboratory drilling rig designed and constructed at the Institute of Geotechnics SAS providing automated continuous monitoring of key process parameters (thrust force, rotation speed, torque, advance rate, etc.). Nominal regime of thrust force 5000 N and rotation speed 1000 rpm was used in the experiments along with monitoring with sampling frequency 17 kHz. The vibration signal was recorded by accelerometers in three orthogonal directions: axial in the drilling directions and two radial directions in horizontal and vertical planes. For the purposes of evaluation, only the vibrations in axial direction were assessed as their signal exhibits the highest entropy. A method providing the expression of mutual differences between the vibrations formed during the drilling of different rock types was developed, which enables to set the differences in abstract space to the planar visualization.Sygnały drgań pochodzących z wierceniu obrotowego trzech rodzajów skał (andezyt, wapień i granit) za pomocą diamentowych wierteł rdzeniowych został przetworzony i oceniony w celu śledzenia charakterystyk sygnałowych badanych rodzajów skał. Zastosowano matematyczne procedury przestrzeni Hilberta, aby wyrazić różnice między rodzajami skał w oparciu o sygnał wibracyjny. Eksperymenty przeprowadzono na laboratoryjnej platformie wiertniczej zaprojektowanej i skonstruowanej w Instytucie Geotechniki SAS, zapewniającej zautomatyzowane ciągłe monitorowanie kluczowych parametrów procesu (siły ciągu, prędkości obrotowej, momentu obrotowego, prędkości posuwu itp.). W doświadczeniach zastosowano nominalną wartość siły nacisku 5000 N i prędkości obrotowej 1000 rpm wraz z monitorowaniem częstotliwości 17 kHz. Sygnał drgań został zarejestrowany przez akcelerometry w trzech kierunkach ortogonalnych: osiowym w kierunkach wiercenia i dwóch promieniowych w płaszczyznach poziomej i pionowej. Do celów oceny oceniono jedynie drgania w kierunku osiowym, ponieważ ich sygnał wykazuje najwyższą entropię. Opracowano metodę wyrażania wzajemnych różnic między drganiami powstającymi podczas wiercenia różnych rodzajów skał, która umożliwia przeniesienie różnic z przestrzeni Hilberta na wizualizację dwuwymiarową

Określenie wydajności zastosowanego Schematu Wykopu Maszyną Drążącą

Deployment of a tunnel boring machine (TBM) for excavation of tunnel structures in particular rock mass environment requires to provide an efficient TBM advance rate by application of the proper excavation regime. The applied regime has to respond to the changes in the excavated rock mass and to the wear of cutting discs installed on the TBM cutterhead. The paper describes a method for the control of excavation efficiency using the excavation process variables monitored during the TBM operation, with subsequent calculation of specific cutting energy, contact pressure of cutting discs and theoretical torque of the TBM cutterhead.Rozmieszczenie Maszyny Drążącej (ang. TBM) do wykopu tuneli, w szczególności w przypadku masy skalnej, wymaga uzyskania wydajnego wykorzystania TBM poprzez zastosowanie odpowiedniego schematu wykopu. Użyty schemat powinien reagować na zmiany w masie skalnej i na zużycie tarczy tnących umieszczonych na głowicy skrawającej TBM. Artykuł opisuje sposoby kontrolowania wydajności wykopu poprzez sprawdzenie zmiennych wykopu obserwowanych podczas pracy TBM z późniejszymi wyliczeniami rozporządzalnej energii tnącej, nacisku tarcz tnących i teoretycznej wartości obrotu głowicy skrawającej TBM

Effects of Outer Membrane Protein TolC on the Transport of <i>Escherichia coli</i> within Saturated Quartz Sands

The outer membrane protein (OMP) TolC is the cell surface component of several drug efflux pumps that are responsible for bacterial resistance against a variety of antibiotics. In this research, we investigated the effects of OMP TolC on <i>E. coli</i> transport within saturated sands through column experiments using a wild-type <i>E. coli</i> K12 strain (with OMP TolC), as well as the corresponding transposon mutant (<i>tolC::kan</i>) and the markerless deletion mutant (Δ<i>tolC</i>). Our results showed OMP TolC could significantly enhance the transport of <i>E. coli</i> when the ionic strength was 20 mM NaCl or higher. The deposition rate coefficients for the wild-type <i>E. coli</i> strain (with OMP TolC) was usually >50% lower than those of the <i>tolC</i>-negative mutants. The measurements of contact angles using three probe liquids suggested that TolC altered the surface tension components of <i>E. coli</i> cells and lead to lower Hamaker constants for the cell–water–sand system. The interaction energy calculations using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory suggested that the deposition of the <i>E. coli</i> cell primarily occurred at the secondary energy minimum. The depth of the secondary energy minimum increased with ionic strength, and was greater for the TolC-deletion strains under high ionic strength conditions. Overall, the transport behavior of three <i>E. coli</i> strains within saturated sands could be explained by the XDLVO calculations. Results from this research suggested that antibiotic resistant bacteria expressing OMP TolC could spread more widely within sandy aquifers

Behavioural, Pharmacokinetic, Metabolic, and Hyperthermic Profile of 3,4-Methylenedioxypyrovalerone (MDPV) in the Wistar Rat

3,4-methylenedioxypyrovalerone (MDPV) is a potent pyrovalerone cathinone that is substituted for amphetamines by recreational users. We report a comprehensive and detailed description of the effects of subcutaneous MDPV (1–4 mg/kg) on pharmacokinetics, biodistribution and metabolism, acute effects on thermoregulation under isolated and aggregated conditions, locomotion (open field) and sensory gating (prepulse inhibition, PPI). All studies used male Wistar rats. Pharmacokinetics after single dose of 2 mg/kg MDPV was measured over 6 h in serum, brain and lungs. The biotransformation study recorded 24 h urinary levels of MDPV and its metabolites after 4 mg/kg. The effect of 2 mg/kg and 4 mg/kg on body temperature (°C) was measured over 12 h in group- vs. individually-housed rats. In the open field, locomotion (cm) and its spatial distribution were assessed. In PPI, acoustic startle response (ASR), habituation, and PPI were measured (AVG amplitudes). In behavioural experiments, 1, 2, or 4 mg/kg MDPV was administered 15 or 60 min prior to testing. Thermoregulation and behavioural data were analysed using factorial analysis of variance (ANOVA). Peak concentrations of MDPV in sera, lung and brain tissue were reached in under 30 min. While negligible levels of metabolites were detected in tissues, the major metabolites in urine were demethylenyl-MDPV and demethylenyl-methyl-MDPV at levels three-four times higher than the parent drug. We also established a MDPV brain/serum ratio ~2 lasting for ~120 min, consistent with our behavioural observations of locomotor activation and disrupted spatial distribution of behaviour as well as moderate increases in body temperature (exacerbated in group-housed animals). Finally, 4 mg/kg induced stereotypy in the open field and transiently disrupted PPI. Our findings, along with previous research suggest that MDPV is rapidly absorbed, readily crosses the blood-brain barrier and is excreted primarily as metabolites. MDPV acts as a typical stimulant with modest hyperthermic and psychomimetic properties, consistent with a primarily dopaminergic mechanism of action. Since no specific signs of acute toxicity were observed, even at the highest doses used, clinical care and harm-reduction guidance should be in line with that available for other stimulants and cathinones