Rapid Dilution Research Articles

Heterogeneous provenance and intracontinental rift evidence in the early–middle Jurassic La Boca Formation in the Huizachal-Peregrina Anticlinorium, Mexico

ABSTRACT The Early–Middle Jurassic Nazas continental rift province in Mexico has been debated as either an extensional continental arc due to eastward subduction beneath North America or an intracontinental rift linked to Pangea break-up. New petrographic and U-Pb geochronological data from the La Boca Formation near Ciudad Victoria – a key locality within this province – reveal diverse clastic sources, forming three provenance groups. Group 1 (Juan Capitán Member) crops out in the Huizachal Valley and consists of volcaniclastic fluvial deposits derived from a local volcanic centre. Group 2 (Agua de Las Minas Member), also found in the Huizachal Valley, overlies Group 1 and has mixed provenance from local volcanic and surrounding basement uplift sources. Both groups transition laterally to deposits of Group 3 (San Pedro Member) to the north, which consists of metamorphiclastic fluvial deposits from the eastern basement uplift and is not influenced by the volcanic centre. The rapid dilution of volcanic detritus within ~35 km highlights the limited extent of the volcanic centre as a source of sediment. Our results suggest that the Nazas province was more likely formed in a continental rift basin with sparse volcanic activity linked to Pangea break-up rather than as an extensive volcanic arc.

Quantification of volcanic degassing and analysis of uncertainties using numerical modeling: the case of Stephanos crater (Nisyros Island, Greece)

Nisyros Island (Greece) is affected by widespread gas emissions from fumarolic fields located at the bottom of hydrothermal craters in the southern part of its caldera. This morphology and the current low gas fluxes make Nisyros an ideal site for testing the limits of physics-based gas dispersal models in confined and low-emission conditions. Here, we focused our attention on the local scale volcanic gas dispersion from the Stephanos hydrothermal crater. In April 2023, a 1-week survey was carried out to measure weather data, CO2 and H2S gas fluxes, air concentrations from portable gas stations, and chemical composition of fumarolic gases and to acquire thermal images of the crater floor. These data were used as inputs and boundary conditions for numerical simulations using a DISGAS-2.6.0 model in order to quantify the present-day volcanic degassing and its associated uncertainties, accounting for the meteorological variability. Model results are provided in terms of H2S probabilistic exceedance and persistence maps, showing gas concentrations within the crater that fall below the thresholds indicated for the occurrence of serious respiratory problems. Since DISGAS-2.6.0 does not account for chemical reactions, this study represents a good opportunity to discuss the methodological limits of simulating the dispersion of H2S which is challenging due to its rapid degradation and dilution in the atmosphere. In this regard, we also provided an empirical law of the H2S depletion in low-emission conditions that takes into account the uncertainties related to the field measurements.

Dynamic Hydration and Viscosity Control of Konjac Glucomannan Enhance Long-Term Antiobesity Effects by Reducing Food Intake in High-Fat-Diet-Fed Mice.

The purpose of this study was to investigate the necessity and importance of dynamic hydration rate and ultimate viscosity control of konjac glucomannan (KGM) for long-term antiobesity effects in C57BL/6J mice on high-fat (HF) diets. KGM supplementation effectively attenuated HF-diet-induced increases in body and tissue weights. The hydration rate and viscosity changes of KGM in the digestive tract were found to have marked impacts on antiobesity effects. KGM with medium hydration and viscosity slowed gastric emptying and intestinal transit, leading to prolonged presence in the lower ileum, increased satiety-related hormones (GLP-1 and PYY), and an 18.27% reduction in daily food intake over 10 weeks (p < 0.05). This resulted in the greatest reduction in weight gain among HF-fed mice. In contrast, KGM with faster hydration and higher viscosity provided only short-term satiety due to rapid dilution. Furthermore, KGM improved metabolic health and altered glycolipid metabolism gene transcription while enriching beneficial gut bacteria; however, no significant differences were observed among the KGM groups in these effects. These findings highlight that synchronizing KGM's hydration rate and viscosity with digestive processes is crucial for regulating satiety and achieving long-term weight loss.

Cationic amphiphilic molecules as novel sclerosants for venous malformation treatment: A study on tranexamic acid-derived low-molecular-weight gels

Venous malformation (VM) is a prevalent congenital vascular anomaly characterized by abnormal blood vessel growth, leading to disfigurement and dysfunction. Sclerotherapy, a minimally invasive approach, has become a primary therapeutic modality for VM, but its efficacy is hampered by the rapid dilution and potential adverse effects. In this study, we introduced a series of cationic amphiphilic molecules, fatty alcohol esters (TA6, TA8, and TA9) of tranexamic acid (TA), which self-assembled into low-molecular-weight gels (LMWGs) in water. The TA9, in particular, is released slowly when hydrogel is injected into the vein locally. Then, it damages the venous wall by destroying cell membranes and precipitating proteins, causing inflammation and thrombosis, thickening of the venous wall, effectively inducing irreversible vein fibrosis. Additionally, TA9 can be rapidly degraded into TA in plasma to reduce toxicity caused by diffusion. Overall, this study suggests that the cationic amphiphilic molecule TA9 is a promising sclerosant for VM treatment, offering a novel, effective, and safe therapeutic option with potential for clinical translation.

Magnesium hydroxide addition reduces aqueous carbon dioxide in wastewater discharged to the ocean

Ocean alkalinity enhancement (OAE) reduces the concentration of dissolved carbon dioxide (CO2) in seawater, leading to atmospheric carbon dioxide removal (CDR). Here we report laboratory experiments and a field-trial of alkalinity enhancement through addition of magnesium hydroxide to wastewater and its subsequent discharge to the coastal ocean. In wastewater, a 10% increase of average alkalinity (+0.56 mmol/kg) led to a 74% reduction in aqueous CO2 (−0.41 mmol/kg) and pH increase of 0.4 units to 7.78 (efficiency 0.73 molCO2/mol alkalinity). The alkalinization signal was limited to within a few metres of the ocean discharge, evident as 27.2 μatm reduction in CO2 partial pressure and 0.017 unit pH increase, and was consistent with rapid dilution of the alkali-treated wastewater. While this proof of concept field trial did not achieve CDR due to its small scale, it demonstrated the potential of magnesium hydroxide addition to wastewater as a CDR solution.

Simultaneous determination of choline, L-carnitine, betaine, trimethylamine, trimethylamine N-oxide, and creatinine in plasma, liver, and feces of hyperlipidemic rats by UHPLC-MS/MS

BackgroundDue to the close correlation between choline, L-carnitine, betaine and their intestinal microbial metabolites, including trimethylamine (TMA) and trimethylamine N-oxide (TMAO), and creatinine, there has been an increasing interest in the study of these compounds in vivo. MethodsIn this study, a rapid stable isotope dilution (SID)-UHPLC-MS/MS method was developed for the simultaneous determination of choline, L-carnitine, betaine, TMA, TMAO and creatinine in plasma, liver and feces of rats. The method was validated using quality control (QC) samples spiked at low, medium and high levels. Second, we applied the method to quantify the effects of Rosa Roxburghii Tratt juice (RRTJ) on plasma, liver, and fecal levels of choline, L-carnitine, betaine, TMA, TMAO, and creatinine in high-fat diet-induced hyperlipidemic rats, demonstrating the utility of the method. ResultsThe limits of detection (LOD) were 0.04–0.027 µM and the limits of quantification (LOQ) were 0.009–0.094 µM. The linear ranges for each metabolite in plasma were choline1.50–96 µM; L-carnitine: 2–128 µM; betaine: 3–192 µM; TMA: 0.01–40.96 µM; TMAO: 0.06–61.44 µM and creatinine: 1–64 µM (R2 ≥ 0.9954). The linear ranges for each metabolite in liver were Choline: 12–768 µM; L-carnitine: 1.5–96 µM; betaine: 10–640 µM; TMA: 0.5–32 µM; TMAO: 0.02–81.92 µM and creatinine: 0.2–204.8 µM (R2 ≥ 0.9938). The linear ranges for each metabolite in feces were choline: 1.5–96 µM; L-carnitine: 0.01–40.96 µM; Betaine: 1.5–96 µM; TMA: 1–64 µM; TMAO: 0.02–81.92 µM and Creatinine: 0.02–81.92 µM (R2 ≥ 0.998). The intra-day and inter-day coefficients of variation were < 8 % for all analytes. The samples were stabilized after multiple freeze–thaw cycles (3 freeze–thaw cycles), 24 h at room temperature, 24 h at 4 °C and 20 days at −80 °C. The samples were stable. The average recovery was 89 %-99 %. This method was used to quantify TMAO and its related metabolites and creatinine levels in hyperlipidemic rats. The results showed that high-fat diet led to the disorder of TMAO and its related metabolites and creatinine in rats, which was effectively improved after the intervention of Rosa Roxburghii Tratt juice（RRTJ）. ConclusionsA method for the determination of choline, L-carnitine, betaine, TMA, TMAO and creatinine in plasma, liver and feces samples was established, which is simple, time-saving, high precision, accuracy and recovery.

Wastewater disinfection with photodynamic treatment and evaluation of its ecotoxicological effects

Research has demonstrated the presence of viruses in wastewater (WW), which can remain viable for a long period, posing potential health risks. Conventional WW treatment methods involving UV light, chlorine and ozone efficiently reduce microbial concentrations, however, they produce hazardous byproducts and microbial resistance that are detrimental to human health and the ecosystem. Hence, there is a need for novel disinfection techniques. Antimicrobial Photodynamic Inactivation (PDI) emerges as a promising strategy, utilizing photosensitizers (PS), light, and dioxygen to inactivate viruses. This study aims to assess the efficacy of PDI by testing methylene blue (MB) and the cationic porphyrin TMPyP as PSs, along a low energy consuming white light source (LED) at an irradiance of 50 mW/cm2, for the inactivation of bacteriophage Phi6. Phi6 serves as an enveloped RNA-viruses surrogate model in WW. PDI experiments were conducted in a buffer solution (PBS) and real WW matrices (filtered and non-filtered). Considering the environmental release of the treated effluents, this research also evaluated the ecotoxicity of the resulting solution (post-PDI treatment effluent) on the model organism Daphnia magna, following the Organisation for Economic Cooperation and Development (OECD) immobilization technical 202 guideline. Daphnids were exposed to WW containing the tested PS at different concentrations and dilutions (accounting for the dilution factor during WW release into receiving waters) over 48 h. The results indicate that PDI with MB efficiently inactivated the model virus in the different aqueous matrices, achieving reductions superior to 8 log10 PFU/mL, after treatments of 5 min in PBS and of ca. 90 min in WW. Daphnids survival increased when subjected to the PDI-treated WW with MB, considering the dilution factor. Overall, the effectiveness of PDI in eliminating viruses in WW, the fading of the toxic effects on daphnids after MB’ irradiation and the rapid dilution effect upon WW release in the environment highlight the possibility of using MB in WW PDI-disinfection.

Physicochemical and Heavy Metal Analysis of Industrial Pollution Model Calibration and Validation Using Field Measurements

This study assessed industrial pollution impacts on rivers near Port Harcourt, Nigeria using physicochemical analysis, heavy metal data, and contaminant transport modeling. Key findings show the rivers are severely degraded with extreme levels of heavy metals, low dissolved oxygen, high conductivity, nutrients, and fecal bacteria exceeding water quality guidelines. Uncontrolled effluent discharges from industries are primarily responsible. A first-order advection-diffusion model reliably predicted the rapid initial dilution and slower downstream attenuation of metals like magnesium and cadmium. The model was successfully calibrated and validated using field measurements to determine key transport parameters including dispersion coefficients. The severe contamination indicates current effluent treatment and regulations are inadequate and require urgent strengthening to control sources, expand monitoring, remediate contamination, restore habitats, and protect ecosystem and public health. Sustained engagement of government, industry, communities and researchers is essential to devise integrated solutions that improve water quality. The modeling provides quantitative guidance on pollution impacts and mitigation needs. Further work should refine predictions, establish ecological thresholds, and validate model results with biomonitoring to support evidence-based, adaptive management.

Catheter with Implantable Chamber Results of 432 Cases

The implantable catheter port is a permanent central venous access device typically used for long-lasting injectable treatments such as chemotherapy. Materials and Methods: We report a retrospective study spread over 6 years to identify 432 patients who benefited from the placement of an implantable catheter port. Patients were followed during hospitalization and at discharge, one month, and one year later. Results: The average age is 67.9 years. There are 284 women and 148 men. The primary cancer requiring the installation of a chamber is essentially represented by cancer and bronchopulmonary cancers. The right internal jugular approach was the most frequently performed. Complications are mainly represented by infection and pneumothorax. Discussion and Conclusion: For prolonged treatments or treatments with aggressive drugs for the veins, a central venous access is preferable to the short peripheral catheter because the repetition of the punctures and the venous irritation of certain injectable drugs expose to pain, thrombosis or even necrosis, peripheral veins. The implantable catheter chamber allows direct access to a vessel to position the end of the catheter at the entrance to the heart, therefore rapid blood dilution. This makes it possible to inject drugs over the long term and/or whose venous tolerance is poor. It is a quick and easy technique with low morbidity.

Rapid dilution effectively decreases hydrocarbons following small oil spills, but impacts on microeukaryote communities are still observed

Dilution affects the distribution and weathering of oil following a spill into coastal seawater, but including dilution in experiments is rare. In open water, dilution is expected to rapidly reduce the concentrations of hydrocarbons, and estimates of impacts and microbial responses from batch experiments may overestimate what happens during a spill event. Three experiments carried out in the southern Gulf of St. Lawrence incorporated periods of incubation of natural microbial communities with either Heidrun medium crude or Bunker C fuel oil followed by dilutions using unexposed seawater. Higher concentrations of n-alkanes (C10 – C35) in Heidrun, resulted in higher initial total hydrocarbon concentrations in incubations with Heidrun compared to Bunker C. Similar polycyclic aromatic hydrocarbon concentrations and potential toxicity were measured in the water column for both oils. Dilution effectively decreased the hydrocarbon concentrations, reducing them to background levels after two dilutions (13.8-fold). Neither the abundance nor the diversity of the prokaryote community was strongly affected by the addition of oil. The natural coastal microbiome was dominated by bacteria that may be facultative hydrocarbon degraders. The abundance of phytoplankton and the diversity of the microeukaryote community decreased during the second incubation in response to both Heidrun and Bunker C, potentially due to photooxidative byproducts produced under full sunlight. Dilution appears to limit the bacterial response to oil, but low hydrocarbon concentrations may still be linked to impacts on the microeukaryote community.

Influence of buoyancy on the mixing, flame structure, and production of NO in hydrogen diffusion flames

This study investigates the impact of buoyancy on the mixing and flame structure of hydrogen jet diffusion flames. A validated Computational Fluid Dynamics (CFD) model for hydrogen diffusion flames is developed, employing the k−ω turbulence model and a steady flamelet combustion model. By accounting for the buoyancy term, the model accurately predicts the stoichiometric hydrogen flame length within a mere 0.2% deviation from the experimental value. In contrast, excluding the buoyancy term leads to a prediction divergence of around 5%.Deeper analysis of the mixture fraction field indicates that buoyancy enhances mixing in the flame’s far-field region, facilitating a more rapid dilution of the fuel stream within the air. This, in turn, results in a shorter flame. The scope of the modelling is expanded to encompass buoyancy effects onhydrogen flames with jet Reynolds numbers (ReJ) up to 15,000. While the buoyancy’s influence on flame control weakens as ReJ increases, a noticeable ∼4% variation in stoichiometric flame length persists between scenarios with and without buoyancy.

Investigating the Hydrodynamics of Intravenous Drug Infusions

One of the most common reported adverse events for intravenous (IV) infusions are infusion site reactions, ranging from redness and pain at the site of infusion to thrombophlebitis. The connection between drug infusion and what drives these adverse events is not well understood. To aid in understanding these phenomena, it is crucial to accurately characterize the evolving hemodynamic environment of the infusion site when developing new intravenous formulations, as too rapid dilution may cause precipitation in the vein, while too little dilution might contribute to phlebitis. In this study, a Large-Eddy Simulation (LES) turbulence modeling inside a Computational Fluid Dynamics (CFD) framework has been used to simulate the flow and mixing characteristics of an infusion entering the bloodstream. This work represents the first such study reporting transient flow fields for intravenous infusions using LES CFD simulations with a realistic non-Newtonian blood model. The output of the CFD model closely resembled the flow and mixing patterns generated in benchtop tests for infusions into a blood analogue and water as the venous fluid across a wide range of flow rates. These models were then investigated further to compare how changes to the fluid rheology model, needle orientation and needle position within the vein resulted in altered mixing regimes at different flow rates.

Investigation on preventive inerting approach of coal spontaneous combustion in gob considering adsorption effect.

Coal spontaneous combustion in the gob poses a significant threat to coal mining operations. Designing optimal process parameters for nitrogen injection to prevent and control fires efficiently is crucial. To achieve this, a multi-field coupling equation was established, considering the adsorption of coal to gas. The model's accuracy was verified on-site, and the effects of nitrogen injection at different locations and flow rates were simulated. The optimal injection parameters were determined by analyzing temperature and inerting time. The results showed that the coal spontaneous combustion hazardous zone in the gob tested on-site was consistent with the simulation from the perspective of physisorption. Nitrogen injection had three stages: gas expansion, rapid oxygen dilution, and complete inerting. The nitrogen injection effect presented a nonlinear change in injection location and flow rate. The optimal nitrogen injection location for the Tingnan Coal Mine in Shaanxi was determined to be 90 m behind the working face on the inlet side, with an optimal flow rate of 800 m3/min. This study focused on gas adsorption and offered valuable insights for creating high-efficiency fire-fighting techniques that involve inserting in the gob.

Rate of dilution and redox ratio influence the refolding efficiency of recombinant fungal dehydrogenases

Dehydrogenases from fungi are attracting attention as industrial biocatalysts due to their high activity and chiral selectivity. However, these enzymes form insoluble aggregates when overexpressed in E. coli, limiting their industrial application. In the present study, we report the systematic development of a refolding process for selected, industrially relevant fungal dehydrogenases, viz., formate dehydrogenase from Candida boidinii (CbFDH) and formate and alcohol dehydrogenases from Geotrichum candium (GcFDH and GcADH, respectively). We first employed a screen to evaluate the effects of different variables on refolding including the buffer system, additives, and rate of dilution. The extent of refolding was determined by enzyme assays, circular dichroism, and tryptophan fluorescence. Our results showed that glycerol and reducing environment are essential for refolding of these dehydrogenases. Further, slow dilution of solubilized protein over 16 h dramatically improved the recovery of refolded enzymes compared to rapid dilution. The importance of slow dilution was further confirmed in a 10-fold scaled-up refolding trial. Overall, we demonstrate a robust method for refolding of fungal dehydrogenases, thus improving their availability for various biocatalytic applications.

Energy assessment and thermodynamic evolution of a novel semi-clathrate hydrate cold storage system with internally circulating gas bubble disturbance

Low energy storage density, intermittent phase changes, and heat transfer barriers have posed significant challenges in the implementation of hydrate energy storage systems. Based on the heterogeneous nucleation mechanism for tetrabutylammonium bromide (TBAB) hydrate phase change energy storage, a novel cold storage system with internally circulating gas disturbance was constructed for energy evaluation and thermodynamic evolution. The hydrate cold storage efficiency, response time, dynamic driving force, unique force pattern of the coils and guest molecule diffusion were analyzed for the first time. The bubbles generated by gas internal circulation provided numerous nucleation sites for hydrate formation, efficiently promoting the energy storage process. The disturbances caused by the bubbles also rapidly transmitted the energy generated by the phase change. A hydrate storage density of 57.4 kWh/m3 for this system was the maximum among known hydrate storage systems. Notably, a change in solution concentration (from 10 wt% to 40 wt%) resulted in a 2–3-fold increase in the cold charge capacity. Rapid dilution of local solutions and rapid release of cold were the ways to promote the cold discharge. Less damage to the stress structure of the coil was due to the loose accumulation of hydrate particles under gas disturbance. The microbubbles generated by the gas disturbance enabled heterogeneous nucleation and heat-mass transfer in the hydrate cold storage. The gas disturbance-based hydrate energy storage process holds significant guiding value for various applications such as refrigerated transport, building cooling systems, and grid peak shaving.

Field fluorometers for assessing oil dispersion at sea

Oil dispersion by the application of chemical dispersants is an important tool in oil spill response, but it is difficult to quantify in the field in a timely fashion that is useful for coordinators and decision-makers. One option is the use of rugged portable field fluorometers that can deliver essentially instantaneous results if access is attainable. The United States Coast Guard has suggested, in their Special Monitoring of Applied Response Technologies (SMART) protocols, that successful oil dispersion can be identified by a five-fold increase in oil fluorescence. Here we test three commercial fluorometers with different excitation/emission windows (SeaOWL, Cyclops 7FO, and Cyclops 7F-G) that might prove useful for such applications. Results show that they have significantly different dynamic ranges for detecting oil and that using them (or similar instruments) in combination is probably the best option for successfully assessing the effectiveness of oil dispersion operations. Nevertheless, the rapid dilution of dispersed oil means that measurements must be made within an hour or two of dispersion, suggesting that one feasible scenario would be monitoring ship-applied dispersants by vessels following close behind the dispersant application vessel. Alternatively, autonomous submersibles might be pre-deployed to monitor aerial dispersant application, although the logistical challenges in a real spill would be substantial.

Extravasation of pathogenic human type 17 Th cells requires both endothelial cell-bound and non-cell bound chemokines

Abstract Extravasation of pro-inflammatory T cells is critical for their effectiveness in host defense and for mediating tissue damage in immune-mediated disease. These cells co-express multiple chemokine receptors and understanding the activities of individual receptors in extravasation is essential for exploiting the chemokine system for therapeutic benefit – either to block or enhance the trafficking of these cells into sites of inflammation. CCR6 is expressed on all human Th17 cells, and we found that CCR6 +CCR2 +cells are enriched both in cells that express a pathogenic Th17 signature, including the ability to produce GM-CSF and IFNγ, and are unusually efficient at transendothelial migration (TEM). Ligands for CCR6, CCR5 and CXCR3 were secreted by and bound to endothelial cells activated with TNFα and IFNγ, and these receptors could all mediate firm arrest of CCR6 +CCR2 +cells under flow - but could not mediate TEM. TEM required CCR2, whose ligands, CCL2, CCL7 and CCL8, were all secreted by activated endothelial cells but failed to bind to endothelial cell surfaces. Chemokines were secreted from the basal as well as the apical sides of endothelial cells. Pre-treating CCR6 +CCR2 +cells with CCL2 or transducing endothelial cells to express a surface-bound CCL2-CXCL9 chimera led to both CCR2-mediated arrest and, importantly, inhibition of TEM. Taken together, our data suggest that while arrest requires endothelial surface-bound chemokine, TEM requires a transendothelial gradient maintained by the rapid dilution of non-bound luminal chemokine by flow. Consequently, mediating arrest versus TEM are not inherent, but nonetheless mutually exclusive activities of receptors that depend, respectively, on binding vs. non-binding chemokines. NIH

Numerical evidence on deflagration fronts in a methane/n-dodecane dual-fuel shear layer under engine relevant conditions

To date, high resolution spray-assisted dual-fuel (DF) studies have focused on capturing the ignition process while the subsequent post-ignition events have been largely neglected due to modeling requirements and high computational cost. Here, we use a simplified approach for studying ignition front evolution after ignition. Three-dimensional scale-resolved simulations of igniting shear layers (0≤Re≤1500) are studied to better understand reaction fronts in engine-relevant conditions. We carry out quasi-DNS in a DF combustion setup consisting of premixed n-dodecane/methane/air/EGR at 700K as a fuel stream and premixed methane/air as the oxidizer at a pressure of 60 atmospheres and an ambient temperature of 900 K. The flow solution resolution is δ/10, where δ=laminar flame thickness. The present study primarily focuses on the hypothesized flame formation and its characterization. Under these conditions, the simulations indicate two-stage ignition further leading to reaction front initiation and dual-fuel flame establishment. For Re<1500, a reaction front resembling DF deflagration is demonstrated close to the auto-ignition timescales. At Re=1500, mixing effects promote more rapid dilution and the DF deflagration front formation is slightly delayed although still observed. For the first time, at rather short timescales of 0.2−0.4IDT (ignition delay time) after the ignition, we provide numerical evidence on DF deflagration front emergence in shear-driven DF combustion processes via 3D numerical simulations for 0<Re≤1500.

Exposures to Particles and Volatile Organic Compounds across Multiple Transportation Modes

Travellers may be exposed to a wide range of different air pollutants during their journeys. In this study, personal exposures within vehicles and during active travel were tested in real-world conditions across nine different transport modes on journeys from London Paddington to Oxford City Centre, in the United Kingdom. The modes tested covered cycling, walking, buses, coaches, trains and private cars. Such exposures are relevant to questions of traveller comfort and safety in the context of airborne diseases such as COVID-19 and a growing awareness of the health, safety and productivity effects of interior air quality. Pollutants measured were particle number (PN), particle mass (PM), carbon dioxide (CO2) and speciated volatile organic compounds (VOCs), using devices carried on or with the traveller, with pumped sampling. Whilst only a relatively small number of journeys were assessed—inviting future work to assess their statistical significance—the current study highlights where a particular focus on exposure reduction should be placed. Real-time results showed that exposures were dominated by short-term spikes in ambient concentrations, such as when standing on a train platform, or at the roadside. The size distribution of particles varied significantly according to the situation. On average, the coach created the highest exposures overall; trains had mixed performance, while private cars and active transport typically had the lowest exposures. Sources of pollutants included both combustion products entering the vehicle and personal care products from other passengers, which were judged from desk research on the most likely source of each individual compound. Although more exposed to exhaust emissions while walking or cycling, the active traveller had the benefit of rapid dilution of these pollutants in the open air. An important variable in determining total exposure was the journey length, where the speed of the private car was advantageous compared to the relative slowness of the coach.

Habitat compression of an estuarine mytilid following half a century of streamflow decline

The distribution of species throughout estuaries is often regulated by salinity gradients, among other key environmental drivers. In many temperate estuaries, however, declining streamflow has led to increased marinization and thus potential habitat compression of some species. Since the mid-1970s, estuaries in south-western Australia have experienced among the greatest decline in streamflow in Australia due to a drying and warming climate. The resultant habitat modification would be particularly unfavourable to sessile fauna, such as mytilid mussels, which are unable to relocate due to their attachment to substrate via byssal threads. This study compared the settlement (and adult survival) of Black Pygmy Mussel Xenostrobus securis in the Swan-Canning Estuary with that described in this system sixty years earlier, over which time freshwater discharge declined by >50%. During the 1960s, settlement of X. securis occurred throughout much of the estuary, beginning in the estuary basin in November and in the upper Swan River in February/March as winter freshwater flow subsided and salinities increased. In contrast, in the current study (2019/2020), X. securis settlement was largely restricted to the upper zones of the estuary. Settlement of X. securis larvae also began much earlier, occurring in the upper Swan River in October, compared with February/March during the 1960s. This is consistent with the salinity tolerances of larval X. securis and declining streamflow, leading to increased marinization of the estuary basin and earlier encroachment of the salt-wedge upstream. In addition, the increased frequency of summer streamflow events in recent decades makes X. securis populations even more vulnerable to substantial mortalities caused by rapid dilution of salinity at warmer temperatures. Thus, the combination of habitat compression, from declining streamflow and increased occurrence of extreme summer rainfall events are likely to pose substantial problems for the survival of X. securis populations in this region into the future. The results of this study further our knowledge on the potential impacts of environmental change on sessile fauna and is of interest to environmental managers.