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

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

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