pH Units Research Articles

Methylene glycol-sulfite pH-clocks for the time-programming of soft materials: advantages, limitations, and yet unexplored opportunities.

Coupling nonlinear reaction networks with soft matter building blocks holds great potential for the design of life-mimicking, time-programmable dissipative self-assembly systems. In this regard, clock reactions are especially useful triggers since they allow to autonomously generate in situ chemical stimuli such as pH changes. The methylene glycol-sulfite (MGS) is a well-known acid-to-base pH-clock reaction which is able to produce sharp and intense pH jumps (up to 5 pH units) after a reliable, yet relatively short (tens of seconds rather than minutes), induction time. Here, after an introductory discussion on the main chemical aspects of MGS and MGS-based systems, their applications for the time-programming of soft matter will be showcased - from micelles, vesicles, and droplets to supramolecular aggregates, polymers and gels. Hopefully, this will help attracting more attention and foster research on the broader field of materials programming with chemical reaction networks.

PH-responsive i-motif-conjugated nanoparticles for MRI analysis.

Gadolinium (Gd)-based contrast agents (CAs) are widely used to enhance anatomical details in magnetic resonance imaging (MRI). Significant research has expanded the field of CAs into bioresponsive CAs by modulating the signal to image and monitor biochemical processes, such as pH. In this work, we introduce the modular, dynamic actuation mechanism of DNA-based nanostructures as a new way to modulate the MRI signal based on the rotational correlation time, τR. We combined a pH-responsive oligonucleotide (i-motif) and a clinical standard CA (Gd-DOTA) to develop a pH-responsive MRI CA. The i-motif folds into a quadruplex under acidic conditions and was incorporated onto gold nanoparticles (iM-GNP) to achieve increased relaxivity, r1, compared to the unbound i-motif. In vitro, iM-GNP resulted in a significant increase in r1 over a decreasing pH range (7.5-4.5) with a calculated pKa = 5.88 ± 0.01 and a 16.7% change per 0.1 pH unit. In comparison, a control CA with a non-responsive DNA strand (T33-GNP) did not show a significant change in r1 over the same pH range. The iM-GNP was further evaluated in 20% human serum and demonstrated a 28.14 ± 11.2% increase in signal from neutral pH to acidic pH. This approach paves a path for novel programmable, dynamic DNA-based complexes for τR-modulated bioresponsive MRI CAs.

A "dual-key-and-lock" DNA nanodevice enables spatially controlled multimodal imaging and combined cancer therapy.

DNA-based theragnostic platforms have attracted more and more attention, while their applications are still impeded by nonspecific interference and insufficient therapeutic efficacy. Herein, we fabricate an integrated "dual-key-and-lock" DNA nanodevice (DKL-DND) which is composed of the inner Dox/Hairpin/Aptazyme-Au@Ag@Au probes and the outer metal-organic frameworks loaded with Fuel strand. Once internalized into human breast cancer cells (MCF-7), the DKL-DND is activated by cascaded endogenous stimuli (acidic pH in the lysosome and high expression of ATP in the cytoplasm), leading to spatially controlled optical/magnetic resonance multimodal imaging and gene/chemo/small molecule combined cancer therapy. By engineering pH and ATP-responsive units as cascaded locks on the DKL-DND, the operating status of the nanodevice and accessibility of encapsulated anti-tumour drugs can be precisely regulated in the specified physiological states, avoiding the premature activation and release during assembly and delivery. Both in vitro and in vivo assessments demonstrate that the DKL-DND with excellent stimuli-responsive ability, biocompatibility, stability and accumulation behaviour was capable of simultaneously affording accurate tumour diagnosis and efficient tumour growth inhibition. This integrated DKL-DND exhibits great promise in constructing self-adaptive nanodevices for multimodal imaging-guided combination therapy.

Structural Impact of N-terminal Pyroglutamate in an Amyloid-β(3-42) Fibril Probed by Solid-State NMR Spectroscopy.

Extracellular amyloid-β (Aβ) plaques, primarily formed by Aβ(1-40) and Aβ(1-42) fibrils, are a hallmark of Alzheimer's disease. The Aβ peptide can undergo a high variety of different post-translational modifications including formation of a pyroglutamate (pGlu, pE) at N-terminal Glu3 or Glu11 of truncated Aβ(3-x) or Aβ(11-x), respectively. Here we studied structural similarities and differences between pEAβ(3-42) and LS-shaped Aβ(1-42) fibrils grown under identical conditions (pH 2) using solid-state NMR spectroscopy. We show that the central region of pEAβ(3-42) fibrils including the turn region around V24 is almost identical to Aβ(1-42) showing similar β-strands also at the N-terminus. The missing N-terminal residues D1-A2 along with pE3 formation in pEAβ(3-42) preclude a salt bridge between K28-D1' as in Aβ(1-42) fibrils. G37 and G38 act as highly sensitive internal sensors for the modified N-terminus, which remains rigid over ~five pH units.

Influence of perennial grasses usage duration on fertility of irtysk oma meadow-black earth soil

Studies were carried out in order to establish the in uence of legume- cereal grass mixtures on the fertility indicators of irrigated meadow- chernozem soil, depending on the duration of their cultivation in grain- grass crop rotation. Two factors were studied in the experiment: A - grass mixture: 1) awnless brome + alfalfa 6 years old, 2) awnless brome + eastern goat’s rue + eastern goat’s rue 12 years old, 3) awnless brome + eastern goat’s rue 21 years old; B - mineral fertilizers: 1) without fertilizers. Nitrogen fertilizers were applied for each of the two mowings, and phosphorus fertilizers were applied as reserves. The dependence of the amount of agronomically valuable aggregates and their resistance to water erosion action on the age of legume-bluegrass grass mixtures was revealed. With an increase in the age of herbs, the number of these aggregates in the soil layer 0…20 cm increased from 48 % under the grass mixture of 6 years of life to 69 % under the grass mixture of 12 years, reaching 79 % under the grass mixture of 21 years of life. When introducing nitrogen-phosphorus fertilizers, a decrease in fractions of agronomically valuable aggregates under the grass stand of 12 and 21 years of life was established by 7…9 % in relation to options without fertilizers. With the increase in the age of grass stand, the content of humus and humic acids in its composition, exchange cations and the reaction of the medium did not change significantly, to a greater extent the changes are associated with the influence of mineral fertilizers. The amount of humus under the herbs in the soil layer 0…20 cm was high and reached 6.7…7.1 % in fertilized versions and 7.5…7.8 % in versions without fertilizers. In the composition of humus, the share of humic acid carbon accounted for from 1.9…2.4 to 2.6…2.7 %, respectively, options. The reaction of the medium in the test variants varied from 5.8 to 6.8 units of pH the aqueous suspension. In the composition of exchangeable cations, calcium accounted for 70 to 87 %. In the experimental variants without fertilizers, the content of mobile phosphorus (according to Chirikov) in the soil was 55…90 mg/ kg; when applying fertilizers, its amount increased by 68…95 mg/kg in a layer of 0…20 cm and by 40 …70 mg/kg in a layer of 20…40 cm. Indicators of the chemical and physicochemical properties of the soil reached optimal parameters after 6 years of cultivating the legume-poa grass mixture, so further use (12 and 21 years) of the soil under grass is not practical.

Forty years of ocean acidification observations (1983–2023) in the Sargasso Sea at the Bermuda Atlantic Time-series Study site

Ocean physical and biogeochemical conditions are rapidly changing over time. Forty years of observations from 1983 to 2023 collected at the Bermuda Atlantic Time-series Study (BATS) site near Bermuda in the North Atlantic Ocean shows continuing trends of surface warming, increase in salinity, loss of dissolved oxygen (DO), increase in carbon dioxide (CO2), and ocean acidification (OA) effects. Over this period, the ocean has warmed by about +1°C, increased in salinity by +0.136, and lost DO by 12.5 µmol kg−1 or ~6%. Since the 1980s, ocean dissolved inorganic carbon (DIC), total alkalinity (TA), a tracer of anthropogenic CO2 (CTrOCA), and fugacities/partial pressures of CO2 (i.e., fCO2 and pCO2) have continued to increase substantially, with no evidence of a reduction in the rates of change over time. Contemporaneously, ocean pH has decreased by ~0.1 pH units [with ocean acidity (i.e., H+) increasing by >30%], and the saturation states of calcium carbonate minerals (Ωcalcite and Ωaragonite) have decreased. These OA indicators show that the chemical conditions for calcification have become less favorable over the past 40 years. Updating of data and trends at the BATS site show how ocean chemistry of the 2020s is now outside the range observed in the 1980s, and how essential these data are for predicting the response of ocean chemistry and marine ecosystems to future shifting earth and ocean conditions.

EXPERIMENTAL CULTIVATION OF SEAWEED ON THE COAST OF COX’S BAZAR, BANGLADESH: IDENTIFYING THE EFFECTS OF ENVIRONMENTAL PARAMETERS ON SEAWEED GROWTH

The current study was carried out at Rezu Khal to determine the ideal area for seaweed farming. Additionally, this investigation uncovered species of commercially productive and lucrative seaweed. Temperature, salinity, pH, dissolved oxygen (DO), conductivity, and Formazin Nephelometric Units (FNU) of surface water ranged from 20.9 to 26.2°C, 24 to 26.2‰, 6.45 to 8.5, 92 to 105%, 33,256 to 64,267 µS/cm, and 11.1 to 42.8, respectively. Phosphate-phosphorus concentrations in surface water were 2.6–7.6 mg/L, 0.04–0.12 mg/L for nitrate-nitrogen, 0.002–0.04 mg/L for nitrite-nitrogen, 0.15–0.83 mg/L for silica, and 0.13–0.28 mg/L for ammonia. Three seaweed species (Gracilaria lemaneiformis, Hypnea musciformes, and Sargassum oligocystum) were cultivated in the selected areas. Two methods (net and long-line) were used for the culture. In this study, 15–20 kg of G. lemaneiformis were harvested every 15 days using the net method. H. musciformes gained 4 to 12 kg every 15 days. Although S. oligocystum thrived nicely, it was challenging to maintain its viability. The findings of this study indicate that seaweed farming is feasible and coastal residents may participate in seasonal income-generating endeavours in coastal waters.

Influence of Diatomite, Zeolite and Bentonite Clay on Agrochemical Indicators Sod-Podzolic Soil and Yield Agricultural Crops

In three-year microfield experiments on sod-podzolic light loam soil, the effect of reclamation doses (3, 6 and 12 t/ha) of siliceous rocks (diatomite, zeolite and bentonite clay) on the main agrochemical properties of the soil and crop productivity in the grain link of the crop rotation of winter wheat-spring barley-seed peas was studied. Among other positive effects, a significant effect of diatomite was found in reducing the concentration of exchangeable forms of aluminum in the soil (by 0.11 mg-eq/100 g), increasing the content of exchangeable forms of magnesium (by 0.33 mg-eq/100 g) and phosphates of soil solution (by 225%). Against the background of the influence of diatoms, barley gave the greatest increase in grain yield (by 38%) and straw (by 29%). The most significant effect of zeolite was revealed in a decrease in the actual, metabolic and hydrolytic acidity of the soil (a decrease of 1.11, 0.48 pH units and 0.33 mg-eq/100 g), as well as the concentration of exchange compounds of calcium (an increase of 17.7 mg-eq/100 g), magnesium (by 12.0 mg-eq/100 g) and potassium (by 46%). The introduction of zeolite rock contributed to the greatest increase in the yield of grain (by 32%) and straw (by 23%) of barley. The most significant influence of bentonite clay was established on the indicators of actual soil acidity (their decrease by 0.65 pH units), the content of exchangeable aluminum (decrease by 0.19 mg-eq /100 g) and phosphates of soil solution (increase by 175%). The introduction of clay contributed to the formation of the greatest increase in grain yield (by 33%) and straw (by 19%) of seed peas.

Transport of Anthropogenic Carbon From the Antarctic Shelf to Deep Southern Ocean Triggers Acidification

AbstractFlow of dense shelf water provide an efficient mechanism for pumping CO2 to the deep ocean along the continental shelf slope, particularly around the Antarctic bottom water (AABW) formation areas where much of the global bottom water is formed. However, the contribution of the formation of AABW to sequestering anthropogenic carbon (Cant) and its consequences remain unclear. Here, we show prominent transport of Cant (25.0 ± 4.7 Tg C yr−1) into the deep ocean (>2,000 m) in four AABW formation regions around Antarctica based on an integrated observational data set (1974–2018). This maintains a lower Cant in the upper waters than that of other open oceans to sustain a stronger CO2 uptake capacity (16.9 ± 3.8 Tg C yr−1). Nevertheless, the accumulation of Cant can further trigger acidification of AABW at a rate of −0.0006 ± 0.0001 pH unit yr−1. Our findings elucidate the prominent role of AABW in controlling the Southern Ocean carbon uptake and storage to mitigate climate change, whereas its side effects (e.g., acidification) could also spread to other ocean basins via the global ocean conveyor belt.

PH dependence of brown-carbon optical properties in cloud water

Abstract. Light-absorbing organic species present in aerosols, collectively called brown carbon (BrC), have important but highly uncertain effects on climate. Clouds likely represent a significant medium for secondary BrC production and for bleaching reactions, though the relative importance of the formation and loss processes in clouds is unknown at present. The acidity (or pH) of atmospheric particles and clouds affects the optical properties of BrC and bleaching rates. Given the wide variability of pH in the atmosphere (pH in particles and clouds ranges from −1 to 8), the optical properties of BrC and its bleaching behavior are expected to vary significantly, and the link between pH and BrC is yet another uncertainty in attempts to constrain its climate forcing effects. In this work, we characterize the pH dependence of BrC optical properties – including light absorption at 365 nm (Abs365), the mass absorption coefficient (MAC365), and the absorption Ångström exponent (AAE) – in bulk cloud water sampled from the summit of Whiteface Mountain, NY. In all samples (n=17), Abs365 and MAC365 increased linearly with increasing pH, highlighting the importance of reporting pH in studies of BrC in aqueous media. There was strong variability in the sensitivity of Abs365 to pH, with normalized slopes that ranged from 5.1 % to 17.2 % per pH unit. The normalized slope decreased strongly with increasing cloud water [K+], suggesting that the non-biomass-burning BrC has optical properties that are more sensitive to pH than BrC associated with biomass burning. AAE also showed a distinct pH dependence as it was relatively flat between pH 1.5–5 and then decreased significantly above pH 5. The cloud water composition was used to inform thermodynamic predictions of aerosol pH upwind and/or downwind of Whiteface Mountain and the subsequent changes in BrC optical properties. Overall, these results show that, in addition to secondary BrC production, photobleaching, and the altitudinal distribution, the climate forcing of BrC is quite strongly affected by its pH-dependent absorption.

PROGRESSIVE MUSCLE HYPOXIA RESEARCH: COULD PHARMACOLOGICAL AGENTS BE USED TO LIMIT REPERFUSION INJURY AT THE TIME OF FASCIOTOMY TO TREAT ACUTE COMPARTMENT SYNDROME?

AbstractBackgroundProgressive muscle ischaemia results in reduced aerobic respiration and increased anaerobic respiration, as cells attempt to survive in a hypoxic environment. Acute compartment syndrome (ACS) is a progressive form of muscle ischaemia that is a surgical emergency resulting in the production of Lactic acid by cells through anaerobic respiration. Our previous research has shown that it is possible to measure H+ ions concentration (pH) as a measure of progressive muscle ischaemia (in vivo) and hypoxia (in vitro). Our aim was to correlate intramuscular pH readings and cell viability techniques with the intramuscular concentration of key metabolic biomarkers [adenosine triphosphate (ATP), Phosphocreatine (PCr), lactate and pyruvate], to assess overall cell health in a hypoxic tissue model.MethodsNine euthanised Wistar rats were used in a non-circulatory model. A pH catheter was used to measure real-time pH levels from one of the exposed gluteus medius muscles, while muscle biopsies were taken from the contralateral gluteus medius at the start of the experiment and subsequently at every 0.1 of a pH unit decline. The metabolic biomarkers were extracted from the snap frozen muscle biopsies and analyzed with standard fluorimetric method. Another set of biopsies were stained with Hoechst 33342, Ethidium homodimer-1 and Calcein am and imaged with a Zeiss LSM880 confocal microscope.ResultsOur study shows that the direct pH electrode readings decrease with time and took an average of 69 minutes to drop to a pH of 6.0. The concentrations of ATP, pyruvate and PCr declined over time, and the concentration of lactate increased over time. At pH 6.0, both ATP and PCr concentrations had decreased by 20% and pyruvate has decreased by 50%, whereas lactate had increased 6-fold. The majority of cells were still viable at a pH of 6.0, suggesting that skeletal muscle cells are remarkably robust to hypoxic insult, although this was a hypoxic model where reperfusion was not possible.ConclusionsOur research suggests that histologically, skeletal muscle cells are remarkably robust to hypoxic insult despite the reduction in the total adenine nucleotide pool, but this may not reflect the full extent of cell injury and quite possibly irreversible injury. The timely restoration of blood flow in theory should halt the hypoxic insult, but late reperfusion results in cellular dysfunction and cell death due to localised free radical formation. Further research investigating the effects of reperfusion in vivo are warranted, as this may identify an optimal time for using pharmacological agents to limit reperfusion injury, around the time of fasciotomy to treat acute compartment syndrome.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

PROGRESSIVE MUSCLE HYPOXIA RESEARCH: A MODIFIED METHOD FOR ASSESSING CELL VIABILITY IN SKELETAL MUSCLE BIOPSIES USING VITALITY DYES AND CONFOCAL MICROSCOPY

AbstractObjectivesAcute compartment syndrome (ACS) is a progressive form of muscle ischaemia that is a surgical emergency and can have detrimental outcomes for patients if not treated optimally. The current problem is that there is no clear diagnostic threshold for ACS or guidance as to when fasciotomies should be performed. A new diagnostic method(s) is necessary to provide real-time information about the extent of muscle ischaemia in ACS. Given that lactic acid is produced by cells through anaerobic respiration, it may be possible to measure H+ ion concentration and to use this as a measure of ischaemia within muscle. Although we are familiar with the key biochemical metabolites involved in ischaemia; and the use of viability dyes in cell culture to distinguish between living or dead cells is well recognised; research has not been undertaken to correlate the biochemical and histological findings of ischaemia in skeletal muscle biopsies. Our primary aim was to investigate the potential for viability dyes to be used on live skeletal muscle biopsies (explants). Our secondary aim was to correlate the intramuscular pH readings with muscle biopsy viability.MethodsNine euthanised Wistar rats were used. A pH catheter was inserted into one exposed gluteus medius muscles to record real-time pH levels and muscle biopsies were taken from the contralateral gluteus medius at the start of experiment and subsequently at every 0.1 of pH unit drop. Prior to muscle biopsy, the surface of the gluteus medius was painted with a layer of 50µmol/l Brilliant blue FCF solution to facilitate biopsy orientation. A 4mm punch biopsy tool was used to take biopsies. Each muscle biopsy was placed in a base mould filled with 4% ultra-low melting point agarose. The agarose embedded tissue block was sectioned to generate 400 micron thick tissue slices with a vibratome. The tissue slices were then placed in the staining solution with Hoechst 33342, Ethidium homodimer-1 and Calcein am. The tissue slices were imaged with Zeiss LSM880 confocal microscope's Z stack function. A dead muscle control was created by adding TritonX-100 to other tissue slices. For quantitative analyses, the images were analysed in Image J using the selection tool. This permitted individual cells to be identified and the mean grey value of each channel to be defined. Using the dead control, we were able to identify the threshold value for living cells using the Calcein AM channel.ResultsViability dyes, used primarily for cell cultures, can be used with skeletal muscle explants. Our study also showed that despite a significant reduction in tissue pH concentration over time, that almost 100% of muscle cells were still viable at pH 6.0, suggesting that skeletal muscle cells are robust to hypoxic insult in the absence of reperfusion.ConclusionsViability dyes can be used on skeletal muscle biopsies. Further research investigating the likely associations between direct measured pH using a pH catheter, the concentrations of key cellular metabolic markers, and muscle tissue histology using vitality dyes in response to ischaemia, rather than hypoxia, is warranted.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Acidification Of Northeastern USA Lakes From Rising Anthropogenic‐Sourced Atmospheric Carbon Dioxide and Its Effects on Aluminum Speciation

AbstractThe impact of rising atmospheric CO2 (pCO2atm) from anthropogenic activities on pH, dissolved inorganic carbon, carbonate mineral saturation, and aluminum (Al) speciation is evaluated for 18 northeastern USA lakes using polythermal, sliding activity reaction path models. pCO2atm was forced using two scenarios from the IPCC's Sixth Assessment Report in which pCO2atm attains either 600 or 1,100 ppm in 2,100. Results suggest pH will decrease 0.15 and 0.32 pH units, will decrease 24% and 49%, and Ωaragonite will decrease 21% and 45%, respectively. These changes are of the same magnitude as those expected for the oceans. The effects of rising pCO2atm on sub‐lethal 20% effect concentrations (i.e., EC20) of Al for brook trout (Salvelinus fontinalis) are evaluated with the biotic ligand model, which indicates Al toxicity effects will increase as pH decreases. These changes could reverse gains in water quality and fisheries health achieved since implementation of the Clean Air Act.

Photographic characterisation of acidification-induced larval malformations in the European lobster Homarus gammarus (Linnaeus, 1758) (Decapoda: Astacidea: Nephropidae)

Abstract Occurrence of developmental malformations is of interest since they potentially influence organismal performance and fitness. We report an increased incidence (⁓ 46 fold) of physical malformations in the larvae of the American lobster Homarus Gammarus (Linnaeus, 1758) in response to seawater acidification (–0.58 pH units relative to nominal pH 8.0). We observed three malformations under the influence of seawater acidification previously undescribed in lobster larvae: a flared carapace, twisted tail, and cross claw. Larvae reared under seawater acidification exhibit significantly lower survivorship (by ⁓14%) and the occurrence of a malformation decreases survivorship (12.7%). Larvae with four types of malformations did not progress through development to reach post-larval stages. Namely, these malformations were a flared carapace, curled carapace, twisted tail, and cross claw. Results from this study provide photographic documentation of various lobster larval malformations that ultimately affect individual success and can be applied for quality-control in hatcheries.

Simulated warming decreases acidity of forest topsoil under Norway spruce (Picea abies (L.) H.Karst.) stands in the Western Carpathians

Global warming is affecting the montane forests of the temperate zone, causing a number of changes in all elements of the ecosystem, including the soil. Norway spruce forests, weakened by ongoing decay over several decades, are likely particularly sensitive to climate-induced changes. The response of soil cation exchange capacity components of spruce stands to warming is not well understood. We have assumed that warming will cause significant changes in pH, disrupting ion-exchange relationships in the soil. To the best of our knowledge, the present study is the first devoted to examining the mechanisms of soil pH change in temperate forest under the influence of warming. The forest in-situ experiment, simulating the soil warming for 578 days, was performed. Laboratory analyses included measurements of pH, and concentrations of carbon and exchangeable forms of calcium, potassium, magnesium, sodium, and aluminum. Shortly after the beginning of simulated warming (84 days), we observed a significant increase in the pH of the topsoil horizons. On average, in the warmed organic (O) horizon, the pH increased by 0.21, and in the mineral (A) horizon by 0.29 pH units. Based on previous studies, the pH increase was most likely triggered by an increase in ammonium-nitrogen content in the warmed soil. Using the Henderson–Hasselbalch equation to model the pH revealed that, in the O horizon, the pH increase is a result of the presence of weaker organic acids, less able to release hydrogen ions during dissociation. In the A horizon, the increase in pH was explained by an increase in abundance of aluminum ions, probably migrating upward from deeper soil layers. We consider that the ion-exchange mechanisms described here will contribute to an improved understanding of the complex processes of spruce forest dieback in the context of climate warming.

Influence of slurry acidification with H2SO4 on soil pH, N, P, S, and C dynamics: Incubation experiment

Acidifying slurry with sulfuric acid (H2SO4) is practiced in some countries for reducing ammonia (NH3) emissions during slurry storage and spreading to land. However, knowledge on how the application of acidified slurry affects soil health and nutrient cycling is lacking. This is particularly important since acidification with H2SO4 can substitute a sulfur (S) mineral fertilizer to increasingly S-deficient agricultural soils. We hypothesized that (ⅰ) slurry acidification would decrease the soil pH over a prolonged period, and as a result (ⅱ) would increase the extractable N, P, C and S concentrations, (ⅲ) and decrease greenhouse gas emissions. By using laboratory mesocosms, the nutrient (C, N, P and S) dynamics were monitored in an arable sandy clay loam soil receiving acidified and non-acidified cattle slurry in a 2-month incubation. Estimations of greenhouse gas emissions (CO2, CH4, N2O), soil-pore- water components (NO3−, NH4+, PO43−, SO42−, DOC, DON, pH) were performed on static mesocosms. In addition, a parallel set of mesocosms were used for soil extractions using distilled water and 0.5 M K2SO4. There were six treatments: (1) soil (control), (2) soil + slurry, (3) soil + acidified slurry (with H2SO4, pH =5.5), (4) soil + HCl, (5) soil + K2SO4, and (6) soil + K2SO4 + H2SO4. Our results showed that over the incubation, slurry acidification reduced soil pH by at least 0.4 units. Water soluble PO43−-P concentration was also reduced, whilst extractable DOC and NO3—N concentrations were increased; the latter as a result of stimulated N mineralization in the acidification treatments (3, 4 and 6). Differences in water soluble SO42- -S concentrations per treatment were not significant over time.Slurry acidification did not significantly affect N2O emissions but decreased net CO2 and CH4 emissions leading to an overall reduction in the soil's total greenhouse gas footprint (expressed as CO2e). We conclude that application of acidified slurry to soil can reduce soil pH by at least 0.4 pH units for up to 2-months before it is buffered back to the pH level of the soil that received the non-acidified slurry. In addition to increasing organic N mineralization with limited impacts on P and S dynamics of the soil and the slurry.

Dual-Lifetime Referencing (t-DLR) Optical Fiber Fluorescent pH Sensor for Microenvironments.

The pH behavior in the μm to cm thick diffusion boundary layer (DBL) surrounding many aquatic species is dependent on light-controlled metabolic activities. This DBL microenvironment exhibits different pH behavior to bulk seawater, which can reduce the exposure of calcifying species to ocean acidification conditions. A low-cost time-domain dual-lifetime referencing (t-DLR) interrogation system and an optical fiber fluorescent pH sensor were developed for pH measurements in the DBL interface. The pH sensor utilized dual-layer sol-gel coatings of pH-sensitive iminocoumarin and pH-insensitive Ru(dpp)3-PAN. The sensor has a dynamic range of 7.41 (±0.20) to 9.42 ± 0.23 pH units (95% CI, T = 20 °C, S = 35), a response time (t90) of 29 to 100 s, and minimal salinity dependency. The pH sensor has a precision of approximately 0.02 pHT units, which meets the Global Ocean Acidification Observing Network (GOA-ON) "weather" measurement quality guideline. The suitability of the t-DLR optical fiber pH sensor was demonstrated through real-time measurements in the DBL of green seaweed Ulva sp. This research highlights the practicability of optical fiber pH sensors by demonstrating real-time pH measurements of metabolic-induced pH changes.

Impact of pH on Gas-Particle Partitioning of Semi-Volatile Organics in Multicomponent Aerosol.

The partitioning of semivolatile organic compounds (SVOCs) between the condensed and gas phases can have significant implications for the properties of aerosol particles. In addition to affecting size and composition, this partitioning can alter radiative properties and impact cloud activation processes. We present measurements and model predictions on how activity and pH influence the evaporation of SVOCs from particles to the gas phase, specifically investigating aqueous inorganic particles containing dicarboxylic acids (DCAs). The aerosols are studied at the single-particle level by using optical trapping and cavity-enhanced Raman spectroscopy. Optical resonances in the spectra enable precise size tracking, while vibrational bands allow real-time monitoring of pH. Results are compared to a Maxwell-type model that accounts for volatile and nonvolatile solutes in aqueous droplets that are held at a constant relative humidity. The aerosol inorganic-organic mixture functional group activity coefficients thermodynamic model and Debye-Hückel theory are both used to calculate the activities of the species present in the droplet. For DCAs, we find that the evaporation rate is highly sensitive to the particle pH. For acidity changes of approximately 1.5 pH units, we observe a shift from a volatile system to one that is completely nonvolatile. We also observe that the pH itself is not constant during evaporation; it increases as DCAs evaporate, slowing the rate of evaporation until it eventually ceases. Whether a DCA evaporates or remains a stable component of the droplet is determined by the difference between the lowest pKa of the DCA and the pH of the droplet.

Impacts of Long-Term Exposure to Ocean Acidification and Warming on Three-Spined Stickleback (Gasterosteus aculeatus) Growth and Reproduction

The warming and acidification of surface waters as predicted by the IPCC leads aquatic species to face major multifaceted changes in their environment. Although teleosts have efficient regulatory systems to cope with these changes, such changes clearly have the potential to impact their physiological functions. Hence, it is crucial to estimate the ability of teleost fishes to cope with multi-stresses to predict how they will deal with future environments. In this context, we investigated the joint effect of warming and acidification on three-spined stickleback (Gasterosteus aculeatus) from the juvenile stage to adulthood, focusing on parameters linked to growth, sexual maturation, and reproduction. Juvenile sticklebacks were split in 2 climate scenarios: a “Current” scenario corresponding to the current seasonal physico-chemical parameters of the water of the “Rade de Brest” in France, and a “RCP8.5” scenario with a warming of 3 °C and an acidification of 0.4 pH units. After 7 months, fish in the RCP8.5 scenario reached the same size and mass as those in the Current scenario, but they needed greater amounts of food to reach satiety. Furthermore, the mortality rate over the experiment was higher in the RCP8.5 scenario. Muscle lipid content, an indicator of energy reserves, was lower in females in the RCP8.5 scenario, suggesting an increased need for energy to maintain homeostasis and other physiological functions or a divergence in energy allocation strategy. Moreover, females exhibited lower sexual maturation and egg quality under the RCP8.5 scenario, which could have contributed to the lower fertilisation rate observed. Males were more resilient to the RCP8.5 scenario, exhibiting only a trend for lower kidney somatic index scores. Altogether, these results suggest a delay and/or an inhibition of gametogenesis and maturation in fish in warmed and acidified waters. The analysis of blood sex steroid concentrations, brain gene expression profiles, and physiological indexes did not allow us to discriminate between a delay and an inhibition of maturation in the RCP8.5 scenario. Overall, these findings clearly indicate that there is a long-term global impact of combined acidification and warming on the mortality and reproductive performance of three-spined stickleback.

Exploring the ITO/PET Extended-Gate Field-Effect Transistor (EGFET) for pH Sensing.

In this project we investigated the extended-gate field-effect transistor (EGFET) structure used with ITO (Indium Tin Oxide)/PET (Polyethylene Terephthalate) sensitive films acting as the extended-gate part of an EGFET obtained from a combination of FETs from the CD4007 chip. We tested the device as a pH sensor by immersing the ITO/PET electrode in several chemical solutions of acidic and basic nature, including hydrogen peroxide, acetic acid, sulfuric acid, and ammonium hydroxide, at different concentrations. Using a Tektronix 4200A sourcemeter, we plotted the current-voltage (I-V) characteristics for the different chemical solutions, and we established a correlation to the pH changes. Results from the plotted I-V characteristics show a great dependance of the drain current (ID) on solution concentration. Furthermore, we measured the pH of each of the used solutions, and we established a relationship between the drain current and the pH value. Our results show a consistent decrease in the current with an increase in the pH value, although with different rates depending on the solution. The device showed high voltage sensitivity at 0.23 V per pH unit when tested in sulfuric acid.