Water Chemistry Research Articles

Spatial characterizations of bacterial dynamics for food safety: Modeling for shared water processing environments

Bacterial dynamics occurring in shared water environments during food processing are typically modeled assuming a homogeneous mixing profile. However, given the tank configurations, and water recirculation and reuse specifications used in many facilities, uniform mixing is not always applicable. Towards this goal, we here developed a novel reaction-diffusion-advection model that captures temporal and spatial variations in the water tanks under dynamic conditions. We utilize the dynamics involved in poultry chilling as an example, as this process features a comprehensive interplay of bacteria, water chemistry and water flow dynamics, as well as determining bacteria levels on carcasses moving into final phases of the food production chain, thus directly influencing public health risk. Well-posedness, existence and uniqueness of positive steady-state solutions with global stability are proved, as well as an estimation of the time scale of convergence to the steady-state solution provided. Simulations are used to verify the analytical results incorporating parameters informed by experimental data from generic, non-pathogenic E. coli, and predictively estimate the time to equilibrium. We show that during a typical 8 h processing shift, the model reaches steady state within 2 h, applying this result to validate model simulations against commercial data. The calibrated model predicts a distribution of E. coli levels on post-chill carcasses with mean and standard deviation of 3.35 ± 0.56 Log10 CFU/carcass, which closely compares to the experimentally observed distribution of 3.55 ± 0.64 Log10 CFU/carcass in an industrial setting. Our results reinforce the key role of space in quantifying essential mechanisms that govern water chemistry and E. coli dynamics during poultry chilling. Our model is an important tool to improve decision making for pathogen control during poultry chilling, as well as a blueprint from which models for processing other commodities like fresh produce and pork can be established.

A rigorously simple quantitative model for free radical behavior in aerobic biological systems

Background Human life is based on oxygen respiration and an enzymatic, free radical-dependent water chemistry, whose billions of parallel reactions take place at pH ∼7.4 and a temperature of 37°C, in accordance with the laws of chemistry. The cellular metabolic processes occur over time periods covered by the half-lives of ROS (reactive oxygen species) for °OH to over 10 s for LOS (lipid oxygen species), indicating that mixtures of free radicals form the basic components for these processes. Summary and Key Messages The main source of radicals is the mitochondrial conversion of 1-5 % oxygen into "primary" ROS and "secondary" LOS. Every endogenous and exogenous radical generation, triggered by "natural background radiation", "natural environment" or "solar radiation" leads to qualitatively similar mixtures of "primary" ROS and "secondary" LOS or RNS (reactive nitrogen species). A Multilevel Antioxidant Regulation, Repair and Protection System (MARRPS) keeps these radical mixtures in a steady state. Depending on the total number of free radicals, different areas of radical action are defined. The Free Radical Ground State (FRGS) with "homeostasis" and "adaptive homeostasis", the Free Radical Threshold Value (FRTV) and Free Radical Pathological Conditions (FRPC). The quantitative ratio ROS > LOS comprehensively characterizes the "homeostasis" and "adaptive homeostasis" area of the FRGS. The total number of free radicals cannot be measured directly in the "homeostasis" area. "Adaptive homeostasis" is achieved when excess radicals are stable produced beyond "homeostasis" of the FRGS. The quantity that remains controllable in this range is a maximum of ∼3.58 10¹² radicals/mg, the value of the body constant FRTV. The sensitized MARRPS provides "semi-stable homeostatic" states characterized by dual stability with ROS > LOS and a stable total ROS/LOS and RNS count beyond the basal FRGS "homeostasis". If the total number of all radicals exceeds the FRTV, where LOS > ROS, this initiates uncontrolled radical chain reactions. The partial failure of the MARRPS in the FRPC area leads to pathological processes which are the starting point for a hundred different diseases. The design principle described by this simple model applies universally to all aerobic life.

Bio-irrigation Promotes Reactive Phosphorus Recycling in an Oxidized Sedimentary Environment

Bio-irrigation by burrowing macrofauna regulates benthic functioning via direct and indirect effects on sediment properties, microbial activities, oxygen dynamics, and organic matter and nutrient turnover. The effects of macrofauna bio-irrigation on benthic nitrogen cycling have been thoroughly investigated, whereas those on phosphorus (P) are comparatively understudied. This is surprising as such effects contribute to sediment oxidation and have a large potential to regulate P mobility and increase P retention. Dissolved oxygen (O2) and inorganic phosphorus (DIP) fluxes, pore water chemistry (DIPpw, Fe[II]pw, Mn[II]pw, pHpw, and oxidation–reduction potential (ORPpw)), and solid-phase Fe(III) pools were measured in reconstructed sediments without or with surface (the amphipod Corophium volutator) and deep (the polychaete Alitta succinea) burrowing macrofauna. Sediments and burrowing macrofauna were collected from the Goro Lagoon (Po River Delta, Italy) in April 2022. Measurements were carried out after a 2-week preincubation to allow sediment conditioning by bioturbators (e.g., burrow construction, bio-irrigation, burrow wall oxidation, steady chemical gradients within sediments and between pore and bottom waters). ORPpw analysis suggested that bio-irrigated sediments were less reduced, and Fe solid-phase analysis suggested a tendency towards an increase in the Fe(III) pool in deep bio-irrigated sediments. Both bioturbators stimulated O2 fluxes and DIP recycling (by a factor of ~ 2), and halved DIPpw, Fe(II)pw, and Mn(II)pw concentrations. The amphipod contributed to DIP fluxes via direct excretion, whereas polychaete excretion was negligible. Polychaetes contributed to DIP fluxes by ventilation of deep burrows within DIP-rich pore water. Bio-irrigation by both burrowers simultaneously promoted higher DIP recycling and sediment oxidation, ensuring the mobilization of a limiting nutrient and preventing the accumulation of reduced chemical species in the surface sediment.

Impact of Water Ionic Chemistry on Kombucha Fermentation

Kombucha is made by using a symbiotic culture of bacteria and yeast (SCOBY) to ferment sweetened tea. This fermentation produces a beverage with a unique aroma and acidic flavor. Kombucha has recently gained popularity in the United States and has been reported to have numerous health benefits. While there is a wide variation in kombucha composition, little is known about the impact water’s chemistry has on the fermentation and the resulting kombucha. Brewing water for kombucha was altered using the following ions: bicarbonate, chloride, calcium, magnesium, and sulfate at different concentrations. Pre-(tea) and post-(kombucha) fermentation (kombucha) products were analyzed for total acidity, pH, free amino nitrogen (FAN), total phenols, antioxidants, and biological components. A one-way ANOVA was run to determine statistical (p < 0.05) differences between the characteristics analyzed. Statistical differences were observed between the different water chemistry ions for all of the characteristics analyzed. Further investigation into the impact water chemistry has on flavor analysis is required. The information obtained from this research can be used to help producers to make kombuchas with an optimized chemical profile and improved antioxidant potentials.

Adsorption Structure-Activity Correlation in the Photocatalytic Chemistry of Methanol and Water on TiO2(110).

ConspectusPhotocatalysis, a process involving light absorption (band gap excitation), charge separation, interfacial charge transfer, and surface redox reactions, has attracted intensive attention because of the potential applications in solar to fuel conversion. Despite the great efforts devoted to the design of materials and optimization of charge separation and overall efficiency, the molecular mechanism of photocatalytic reactions, for example, water oxidation, is still unclear, mainly because of the complexity of powder catalysts and the aqueous environment which prevent the direct experimental detection of adsorption sites, surface species, and charge/energy transfer dynamics. Without direct evidence, the charge transfer and elementary reaction steps remain elusive, and misleading conclusions are sometimes drawn. For instance, the positively charged 5-fold coordinated Ti sites (Ti5cs) on TiO2 surfaces are argued to propel holes and therefore cannot be active sites for oxidative reactions, regardless of the demonstration by scanning tunneling microscopy (STM). Direct site-specific measurements are thus highly demanded. Surface science studies, which rely on well-defined single crystals and ultrahigh vacuum based techniques, can identify the active sites and active species at the catalyst surfaces and measure the interfacial electronic structure and energy of desorbing species for charge transfer analysis, providing direct evidence for investigating the photocatalytic reaction mechanism at the molecular level.In this Account, the elementary photocatalytic chemistry of methanol and water on TiO2, which are investigated by surface science techniques such as atom-resolved STM, ensemble-averaged mass spectrometer based temperature-programmed desorption/time-of-flight spectroscopy, and photoelectron spectroscopy in combination with theoretical calculations, will be described. Both methanol and water can be photocatalytically oxidized at Ti5cs, producing adsorbed formaldehyde and gaseous •OH radicals, respectively, under ultraviolet (UV) light irradiation. The photocatalytic activity shows salient adsorption structure including adsorption site (terminal/bridging), adsorption state (molecular/dissociative) and adsorption configuration (monomer/cluster) dependence, which comes from the ability to generate terminal anions which are capable of capturing photogenerated holes and exhibit superior photocatalytic activity over their parent molecules. These studies reveal the origin of the correlation between photocatalytic activity and adsorption structure of CH3OH and H2O on TiO2 surfaces and suggest that the simple criteria widely used to analyze the feasibility of charge transfer, i.e., the relative position of the band edges and the molecular orbitals of adsorbates, should be replaced by the change of Gibbs free energy of the charge trapping reaction from the thermodynamic point of view. These results contribute to the fundamental understanding of photocatalysis. Based on our research, future state-resolved and time-resolved studies can provide deeper insight into the charge and energy transfer and transient intermediate species, which will benefit the depiction of the overall photocatalytic reactions, for example, the photocatalyzed oxygen evolution reaction from water.

Synthesis of a hydrological, water chemistry, and contaminants research program in the Peace-Athabasca Delta (Canada) to inform long-term monitoring of shallow lakes

In a multistressor world, evidence-based stewardship of aquatic ecosystems requires long-term monitoring data to understand the timing and magnitude of environmental change and potential causes. At the Peace-Athabasca Delta (PAD; northeastern Alberta, Canada), concern for aquatic ecosystem degradation has triggered renewed and urgent calls by Indigenous, national, and international governance bodies for implementation of a long-term lake monitoring program capable of tracking changes in hydrological conditions and contaminant deposition attributable to major energy projects located upstream, climate change, and other unnatural and natural processes. Challenges imposed by the delta's size, hydrological complexity, inaccessibility of lakes, and other factors, however, have long impeded implementation of a delta-wide lake monitoring program. To address this pressing need, here we review and synthesize results obtained during 7 years (2015–2021) of intensive, multifaceted research at 60 shallow lakes spanning the delta's broad hydroecological gradients to inform an integrated hydrology, water chemistry, and contaminants monitoring program. The research involved systematic, repeated measurements of water isotope composition, water depth variation, water chemistry and turbidity, and metal(loid) concentrations in lake surface sediment and periphytic biofilm. Results reveal marked spatial and temporal variation of hydrological processes and their affects on lake water balance and depth, strong association between hydrological processes and lake water chemistry, and that concentrations of nickel and vanadium (key oil sands indicators) remain within the range of natural variation. Correspondence of generalized additive model trendlines for isotope-derived lake evaporation-to-inflow ratios and water chemistry with climate indices (Pacific Decadal Oscillation, Oceanic Niño Index) demonstrates the sensitivity, and predictability, of lake ecosystem processes in the delta to large-scale climatic patterns. We provide recommendations for field sampling, sample analysis, data display, and integration of information for ongoing monitoring at the PAD. These approaches are readily transferable to other complex landscapes with abundant shallow waterbodies threatened by multiple stressors that may alter hydrological regimes and contaminant delivery.

Hydrochemical characterization and sustainability assessment of Ismailia canal water, Eastern Nile Delta, Egypt: implications for human health and environmental safety

Surface freshwater systems globally face severe stresses due to overpopulation and associated waste. The Ismailia Canal, a crucial freshwater source in the eastern Nile Delta, Egypt, serves multiple purposes and is endangered by various environmental activities. This study characterizes the canal’s water using physicochemical parameters to evaluate its suitability for different uses. Water samples were collected twice in winter and summer seasons of the year 2018 from eight sites distributed along the course of Ismailia Canal. A comprehensive chemical analysis of the samples was carried out. Water chemistry was graphically and statistically assessed. Water qualities were evaluated using WHO guidelines, water quality index (WQI), Pollution indices of metals (PIm) and long- and short-term effect of trace elements on irrigation. Results show that the water is slightly alkaline and moderately hard, with higher salinity in winter than summer. Major cations and anions are higher in winter, whereas NO₃ is higher in summer. The canal water is primarily of the Ca(Mg)-HCO₃ type, influenced mainly by rock-water interactions. While most physicochemical parameters meet drinking water standards, Al, Sb, As, Cd, Fe, Pb, and Tl exceed limits, with significant impacts from Al and Tl year-round, and seasonal impacts from As, Pb, Cd, and Fe. For irrigation, water quality is generally unaffected in winter, but Mo and Se have slight impacts in summer for long-term use. This research is vital for informing sustainable water management practices, which are crucial for Egypt’s research initiatives, economic stability, and environmental sustainability.

Resilience of Phytoplankton and Microzooplankton Communities under Ocean Alkalinity Enhancement in the Oligotrophic Ocean.

Ocean alkalinity enhancement (OAE) is currently discussed as a potential negative emission technology to sequester atmospheric carbon dioxide in seawater. Yet, its potential risks or cobenefits for marine ecosystems are still mostly unknown, thus hampering its evaluation for large-scale application. Here, we assessed the impacts OAE may have on plankton communities, focusing on phytoplankton and microzooplankton. In a mesocosm study in the oligotrophic subtropical North Atlantic, we investigated the response of a natural plankton community to CO2-equilibrated OAE across a gradient from ambient alkalinity (2400 μmol kg-1) to double (4800 μmol kg-1). Abundance and biomass of phytoplankton and microzooplankton were insensitive to OAE across all size classes (pico, nano and micro), nutritional modes (autotrophic, mixotrophic and heterotrophic) and taxonomic groups (cyanobacteria, diatoms, haptophytes, dinoflagellates, and ciliates). Consequently, plankton communities under OAE maintained their natural chlorophyll a levels, size structure, taxonomic composition and biodiversity. These findings suggest a high tolerance of phytoplankton and microzooplankton to CO2-equilibrated OAE in the oligotrophic ocean. However, alternative application schemes involving more drastic perturbations in water chemistry and nutrient-rich ecosystems require further investigation. Nevertheless, our study on idealized OAE will help develop an environmentally safe operating space for this climate change mitigation solution.

Seasonality and Predictability of Hydrometeorological and Water Chemistry Indicators in Three Coastal Forested Watersheds

Forests are recognized for sustaining good water chemistry within landscapes. This study focuses on the water chemistry parameters and their hydrological predictability and seasonality (as a component of predictability) in watersheds of varying scales, with and without human (forest management) activities on them, using Colwell indicators for data collected during 2011–2019. The research was conducted in three forested watersheds located at the US Forest Service Santee Experimental Forest in South Carolina USA. The analysis revealed statistically significant (α = 0.05) differences between seasons for stream flow, water table elevation (WTE), and all water chemistry indicators in the examined watersheds for the post-Hurricane Joaquin period (2015–2019), compared to the 2011–2014 period. WTE and flow were identified as having the greatest influence on nitrogen concentrations. During extreme precipitations events, such as hurricanes or tropical storms, increases in WTE and flow led to a decrease in the concentrations of total dissolved nitrogen (TDN), NH4-N, and NO3-N+NO2-N, likely due to dilution. Colwell indicators demonstrated higher predictability (P) for most hydrologic and water chemistry indicators in the 2011–2014 period compared to 2015–2019, indicating an increase in the seasonality component compared to constancy (C), with a larger decrease in C/P for 2015–2019 compared to 2011–2014. The analysis further highlighted the influence of extreme hydrometeorological events on the changing predictability of hydrology and water chemistry indicators in forested streams. The results demonstrate the influence of hurricanes on hydrological behavior in forested watersheds and, thus, the seasonality and predictability of water chemistry variables within and emanating out of the watershed, potentially influencing the downstream ecosystem. The findings of this study can inform forest watershed management in response to natural or anthropogenic disturbances.

Testing floc settling velocity models in rivers and freshwater wetlands

Abstract. Flocculation controls mud sedimentation and organic carbon burial rates by increasing mud settling velocity. However, calibration and validation of floc settling velocity models in freshwater are lacking. We used a camera, in situ laser diffraction particle sizing, and suspended sediment concentration–depth profiles to measure flocs in Wax Lake Delta, Louisiana. We developed a new workflow that combines our multiple floc data sources to distinguish between flocs and unflocculated sediment and measure floc attributes that were previously difficult to constrain. Sediment finer than ∼10 to 55 µm was flocculated with median floc diameter of 30 to 90 µm, bulk solid fraction of 0.05 to 0.3, fractal dimension of ∼2.1, and floc settling velocity of ∼0.1 to 1 mm s−1, with little variation along water depth. Results are consistent with a semi-empirical model indicating that sediment concentration and mineralogy, organics, water chemistry, and, above all, turbulence control floc settling velocity. Effective primary particle diameter is ∼2 µm, about 2 to 6 times smaller than the median primary particle diameter, and is better described using a fractal theory. Flow through the floc increases settling velocity by an average factor of 2 and up to a factor of 7 and can be described by a modified permeability model that accounts for the effect of many primary particle sizes on flow paths. These findings help explain discrepancies between observations and an explicit settling model based on Stokes' law that depends on floc diameter, permeability, and fractal properties.

Implications of climate change on freshwater ecosystems and their biodiversity

Global warming is a phenomenon whereby the planet's exposure to the sun's radiation worsens from the high emission of gasses believed to trap heat within the atmosphere. Carbon dioxide (CO2) is the leading greenhouse gas majorly responsible for global warming and other related issues and is a danger to global society. This one has a particular role in portraying the key importance of the shifting climate that invariably influences water supply and agricultural production. Global warming presents complex challenges to aquatic organisms and stocks and other natural aquatic life resources. This study examines how freshwater and marine species are affected by climate change in aquatic habitats. Aquatic species' metabolism, growth, reproduction, and dispersal are all impacted by rising temperatures and altered water chemistry brought on by increased greenhouse gas emissions, especially CO2. The goal is to pinpoint the ecosystems and vulnerable species that are most impacted by these changes and suggest flexible management techniques. The suggested remedies center on creating sustainable conservation strategies that lessen the effects of climate change on aquatic biodiversity and increase these ecosystems' resilience. The socio-economic interdependencies between water and climate change impact agricultural and water resources, and the pressures exerted on water bodies and water supply landscapes. Another area is related to alterations in the physical and chemical properties of the water, such as the temperature, which is a well-known effect of climate change: 'This causes abnormalities in the metabolism and physiology of aquatic species.' These alterations flow through the chain and regime of growth, reproduction, feeding habits and distribution, migration, and mass of fish and other creatures in the water system. However, the long-term effect of climate variation and climate change on freshwater ecosystems requires much scientific investigation to address challenges in aquatic ecosystem conservation and sustainability. This being the case, adaptive management solutions that address the interrelated impacts of climate change have to be applied and implemented to reduce vulnerability in aquatic ecosystems worldwide.

Taking Application Rates With a Grain of Salt: Uncovering the Impact of Road De‐Icing Salt on Freshwaters of a Mountain Catchment in the Italian Alps

ABSTRACTWhile application of salt for de‐icing purposes has been extensively studied in urban areas of North America, little attention has been paid to it in Europe, particularly in mountain areas. Here, after assessment of baseline salinity, and through applying different approaches (i.e., univariate statistical techniques, Multivariate Regression Trees, multivariate regressions), we investigated the potential changes in water chemistry and benthic macroinvertebrate community structure caused by the application of de‐icing salt over an entire winter season, in a mountain catchment located in the Italian Alps (N 46°, E 11°). Concurrently, we tested and compared the application of three different benthic macroinvertebrate indices used to assess salinisation impacts. Overall, we identified a constant level of baseline salinity across a 13‐year period, accompanied by a strong seasonality factor. Despite an application rate comparable to those of large North American cities, macroinvertebrate communities showed little evidence of change. However, chemical ions whose concentrations are known to be influenced by de‐icing salt (e.g., Na+, Cl−) were identified as the structuring drivers of the macroinvertebrate communities, thus suggesting that the studied riverine environment show a high potential for change in relation to salinity. In conclusion, we caution against the simple evaluation of application rates to assess the risk/level of salinisation within a catchment, and encourage further specific analysis and study of salinisation in mountain areas: they appear as sensitive habitats to potential variations in salinity, and stressors such as increased urbanisation and climate change will further exacerbate the risk of increasing salinisation in mountain freshwaters.

On the Relationship between Water Adsorption and Surface Chemistry in Soda-lime Silicate Glasses.

Understanding how the surface structure affects the bioactivity and degradation rate of the glass is one of the primary challenges in developing new bioactive materials. Here, classical and reactive molecular dynamics simulations are used to investigate the relationship between local surface chemistry and local adsorption energies of water on three soda-lime silicate glasses. The compositions of the glasses, (SiO2)65-x(CaO)35(Na2O)x with x=5, 10, and 15, were chosen for their bioactive properties. Analysis of the glass surface structure, compared to the bulk structure, showed that the surface is rich in modifiers and non-bridging oxygen atoms, which were correlated with local adsorption energies. The reactivity of the glasses is found to increase with higher Na2O content, attributed to elevated Na cations and undercoordinated species at the glass surfaces. The current work provides insights into the relationship between the surface structure, chemistry, and properties in these bioactive glasses and offers a step toward their rational design.

Hydrological processes in the Aksu River source region during the intense ablation period based on water chemistry and isotopes

Hydrological processes in the Aksu River source region during the intense ablation period based on water chemistry and isotopes

Cover Feature: Water Chemistry at the Nanoscale: Clues for Resolving the “Water Paradox” Underlying the Emergence of Life (ChemistryEurope 6/2024)

Cover Feature: Water Chemistry at the Nanoscale: Clues for Resolving the “Water Paradox” Underlying the Emergence of Life (ChemistryEurope 6/2024)

Photocatalyzed oxidation of water on oxygen pretreated rutile TiO2(110)

The oxygen evolution reaction (OER) is the bottleneck in the overall photocatalytic splitting of water. The active sites (terminal titanium or bridging oxygen) and active species (molecular or dissociative water) of the initial step of the photocatalyzed OER on the prototypical photocatalyst TiO2, remain debatable. Herein, the photocatalytic chemistry of monolayer water on oxygen-pretreated TiO2(110) (o-TiO2(110)) and reduced TiO2(110) (r-TiO2(110)) surfaces initiated by 400 nm light illumination was investigated by time-dependent two-photon photoemission spectroscopy (TD-2PPE). The photoinduced reduction of the H2O/o-TiO2(110) interface rather than the H2O/r-TiO2(110) interface was detected by TD-2PPE. The difference in 2PPE originated from the presence of the terminal hydroxyl anions (OHt¯) on H2O/o-TiO2(110), as identified by X-ray photoelectron spectroscopy and temperature-programmed desorption. Therefore, the evolution of the electronic structure of H2O/o-TiO2(110) was attributed to the photocatalyzed oxidation of the terminal hydroxyl anions, which most likely formed gaseous •OH radicals, reducing the interface. This work suggested that the oxidation of hydroxyl anions on top of the terminal titanium ions on TiO2, which were excluded previously in solution, need to be considered in the mechanistic studies of the photocatalyzed OER.

Rapid subsidence as a driver of phosphate deposition in the later Ordovician: Case study from the Alabama Appalachians

An increase in accumulation of phosphate-enriched sediment occurred in several areas of Earth's oceans during the later Ordovician, suggesting that some fundamental change (s) in seawater and/or pore water chemistry were taking place, either syndepositionally or during early diagenesis. One hypothesis is that widespread cooling of the water column led to this increase, but another is that the increase could have been forced primarily by changes in seawater chemistry that accompanied an influx of siliciclastic sediments associated with tectonically driven subsidence. Here, we report on findings from study of the upper ~30 m of the >200 m of Middle and Late Ordovician strata exposed near Tidwell Hollow, Blount County, Alabama, and what the results suggest about the competing hypotheses. This Ordovician sequence, deposited along the southeastern margin of Laurentia during the initial (Blountian) stage of the Taconic Orogeny, records the transition from a restricted peritidal carbonate shelf environment (the “Black River lithofacies”) into a more normal marine carbonate environment (the “Trenton lithofacies”). In particular, the younger carbonate strata are notable for their measurably higher amounts of secondary phosphate minerals. This stratigraphic interval is also well-constrained chronostratigraphically by the presence of the Deicke and Millbrig K-bentonite beds (altered volcanic tephra layers), thus it is ideal for a focused geochemical, petrographic, and stratigraphic investigation of the increased phosphate content of a specific Upper Ordovician sequence. Analyses of bulk rock samples and of extracted collophane grains (via x-ray fluorescence, XRF, and in-situ laser ablation inductively coupled plasma mass spectrometer, ICPMS) suggest that phosphogenesis in these strata was episodic rather than slow and steady, with a depositional pattern of abrupt increases followed by abrupt declines. Observed trace element changes in the 12 m to 18 m sample interval include the occurrence of elevated Th/U ratios (maximum of 5.7) accompanied by Y/Ho ratios that range from 27 (base) to 51 (top). We attribute these changes to increasing silicate influx into the basin and an accompanying increase in available Fe, which would preferentially scavenge MREEs and then release them to the pore waters leading to MREE enrichment, which we also observe in this interval. In a rapidly subsiding basin, MREE enrichment could have resulted from initial restriction of bottom water circulation followed by gradually more open marine conditions. Some allochems and textures that are more characteristic of the older Black River lithofacies than the younger Trenton lithofacies (e.g. framework grains of calcareous green algae and Type 1 and Type 2 oncoids, fenestral lime mudstones, and associated small framestones of Tetradium sp. buildups) persist in relative abundance upsection into the ~10 m interval of strata above the Millbrig K-bentonite Bed, and this persistence supports the hypothesis that the Trenton transgression was not initially accompanied by widespread cooling of the Laurentian epicontinental sea. Instead, we propose that variable weathering rates, turbidity, and nutrient supply accompanied by relatively rapid subsidence could have governed the observed variability in phosphate deposition and elemental abundances in these sediments, and that this subsidence of the Laurentian margin could have been the driver of an uptick in phosphate deposition during the later Ordovician here, and perhaps at other locations as well where subsidence was occurring, given that increased phosphate deposition is a globally recognized and globally significant change in many Upper Ordovician sequences beyond eastern Laurentia.

Guidance on aqueous matrices for evaluating novel precipitants and adsorbents for phosphorus removal and recovery

Phosphorus (P) removal from water and recovery into useable forms is a critical component of creating a sustainable P cycle, although mature technologies for P removal and recovery are still lacking. The goal of this paper was to advance the testing of novel materials for P removal and recovery from water by providing guidance on the development of more realistic aqueous matrices used during materials development. Literature reports of “new” materials to remove P from water are often difficult to compare in terms of performance because authors use a myriad of water chemistries containing P concentrations, pH, and competing ions. Moreover, many tests are conducted in simplified matrices that do not reflect conditions in real systems. To address this critical gap, the research herein developed a systematic approach of identifying aqueous matrices relevant to P recovery, including key components in the aqueous matrices having the greatest influence on the mechanisms of P removal with emphasis on phosphate precipitation and phosphate adsorption, and providing guidelines on relevant “recipes” for aqueous solutions for testing novel materials. Key components in the aqueous matrices included hydrogen ion (i.e., pH), multivalent metal cations, and dissolved organic matter due to their influence on phosphate precipitation and adsorption mechanisms. Recipes for buffer solution and synthetic groundwater, surface water, anaerobic digestate, and stored urine are discussed in the context of P removal and recovery processes. Wherein the adoption of standard matrices in other fields have permitted direct comparison of processes or materials, it is anticipated that adoption of relevant aqueous matrix recipes for P removal and recovery will improve the ability to directly compare novel materials and processes.

Analyzing the State of Phosphate Water Chemistries in High-Pressure Drum Boilers

Analyzing the State of Phosphate Water Chemistries in High-Pressure Drum Boilers

Rapid Eutrophication of a Clearwater Lake: Trends and Potential Causes Inferred From Phosphorus Mass Balance Analyses.

Many clearwater lakes increasingly show symptoms of eutrophication, but the underlying causes are largely unknown. We combined long-term water chemistry data, multi-year sediment trap measurements, sediment analyses and simple mass balance models to elucidate potential causes of eutrophication of a deep temperate clearwater lake, where total phosphorus (TP) concentrations quadrupled within a decade, accompanied by expanding hypolimnetic anoxia. Discrepancies between modeled and empirically determined P inputs suggest that the observed sharp rise in TP was driven by internal processes. The magnitude of seasonal variation in TP greatly increased at the same time, both in surface and deep water, partly decoupled from deep water oxygen conditions. A positive correlation between annual P loss from the upper water column and hypolimnetic P accumulation could hint at a short-circuited P cycle involving lateral TP transport from shallow-water zones and deposition and release from sediments in deep water. This hypothesis is also supported by P budgets for the upper 20 m during stable summer stratification, suggesting that sediments in shallow lake areas acted as a P net source until 2018. These changes are potentially related to shifts in submerged macrophytes from wintergreen charophyte meadows (Nitellopsis obtusa) to annual free-floating hornwort (Ceratophyllum demersum) and to increased sulfide formation, promoting iron fixation in the sediments. Iron bound to sulfur is unavailable for binding P, resulting in a positive feedback between P release in shallow lake areas, primary productivity, macrophyte community structure and redox-dependent sediment biogeochemistry. Overall, our results suggest that relationships more complex than the commonly invoked increase in internal P release under increasingly anoxic conditions can drive rapid lake eutrophication. Since the proportion of littoral areas is typically large even in deep stratified lakes, littoral processes may contribute more frequently to the rapid lake eutrophication trends observed around the world than is currently recognized.