Phase Partitioning Research Articles

Unveiling the effect of Hf-(Mo,W) addition on the coarsening, agglomeration, and dissolution behaviour of γ'-Ni3Al precipitates in model Ni-based superalloys

In compositional design of Ni-based superalloys, atomic size of alloying elements appears as the primary factor affecting alloy strengthening. Depending on atomic size, the phase partitioning preferences of alloying elements not only control the coarsening and dissolution characteristics of γ' precipitates, but also govern their morphological development upon aging. The current study, therefore, investigates the influence of larger atomic radius X = Hf element addition and its co-additions with smaller atomic radii refractory X = Mo(W) elements on the microstructural and mechanical properties of model Ni80Al15Hf5 and Ni80Al15Hf2.5Mo(W)2.5 superalloys. Accordingly, it is concluded that the replacement of 2.5 at% X = Hf addition with the same amount of X = Mo(W) additions reduces and increases γ' participation tendency of X = Hf and X = Mo(W) elements, respectively. Agreeing with classical Lifshitz-Slyozov-Wagner (LSW) kinetics, γ'-Ni3Al-Hf-W precipitates coarsen at a slower rate compared to their γ'-Ni3Al-Hf-Mo counterparts, both begin to agglomerate at longer aging times, i.e., 256 h. On the other hand, readily coarsened, aligned, and agglomerated γ'-Ni3Al-Hf precipitates start to dissolve in γ matrix after 16 h, which hence disobey LSW theory. Most probably, higher γ'/γ interfacial energy contribution of faster-diffusivity X = Hf element leads to this three-step temporal evolution of γ'-Ni3Al-Hf precipitates, i.e., (i) coarsening, (ii) alignment/agglomeration, and (iii) dissolution, to occur much earlier and accelerates the strength degradation. Conversely, X = Hf-W co-addition, which causes better mechanical strength than both X = Hf and X = Hf-Mo additions, reduces the degree of strength worsening possibly due to the beneficial contributions of X = W element at γ'/γ interfaces.

Field gas huff-n-puff for enhancing oil recovery in Eagle Ford shales – Effect of reservoir rock and crude properties

• A unique experimental design for investigating oil extraction from shales by huff-n-puff process. • Utilization of field gas as a solvent for enhancing shale oil production. • Oil extraction efficiency could decrease with gas-oil ratio despite increasing rock porosity. • Oil viscosity strongly influences produced oil composition and recovery factor. Field gas huff-n-puff has a great potential for enhancing oil recovery in shale reservoirs that suffer from dramatic production decline. However, most previous studies have focused on CO 2 huff-n-puff, and a simplified injection hydrocarbon gas composition has been commonly used in nearly all experimental works. This work is a continuation of our previous study on the field gas huff-n-puff process for enhancing oil production from Eagle Ford shales with a focus on the impact of reservoir rock (porosity, permeability, and S 1 content) and crude oil properties (viscosity, density, composition). A unique huff-n-puff process was designed to investigate the characteristics of oil production during soaking and pressure depletion. The efficiency of oil extraction as well as the associated production mechanisms were evaluated based on the ultimate recovery factor and properties of produced oil. Huff-n-puff experiments were conducted on reservoir core plugs with distinct reservoir properties (i.e., porosity, permeability, and S 1 contents). It was found that an increase in Gas Research Institute (GRI) porosity from 4.3% to 12.9% could improve the oil recovery factor from 49.0% to 62.8%. However, such a trend was not observed in the huff-n-puff experiments with a higher OOIP where an increase of GRI porosity from 5.6% to 12% led to a decrease in recovery factor by 24.7%. This remarkable finding could be related to the decrease of gas-oil ratio as OOIP increased at a constant injected mass of gas. It was also found that the average URF decreased from 63.0% to 38.3% with an increase in oil viscosity from 3.56 to 9.59 cp, which could be attributed to the reduced diffusive mass transfer and phase partitioning of components from injection gas and resident oil. This work has advanced our understanding of how rock and oil properties affect oil the efficiency of oil extraction by cyclic gas injection in Eagle Ford shales. It also supports the development of reservoir screening criteria for a preliminary assessment of the suitability of an unconventional reservoir for this EOR method. Finally, the results present a unique high quality data set for further modelling work.

Influence of dissolved organic carbon on multimedia distribution and toxicity of fipronil and its transformation products in lotic waterways

Environmental fate and ecological impacts of fipronil and its transformation products (FIPs) in aquatic environment have caused worldwide attention, however, the influence of dissolved organic carbon (DOC) on multimedia distribution, bioavailability, and toxicity of FIPs in field waterways was largely unknown. Here, we collected 11 companion water and sediment samples along a lotic stream in Guangzhou, South China. FIPs were ubiquitous with total water concentrations ranging from 1.22 to 43.2 ng/L (14.8 ± 12.9 ng/L) and fipronil sulfone was predominant in both water and sediment. More than 70% of FIPs in aqueous phase were bound to DOC and the KDOC values of FIPs were approximately 1–2 orders of magnitude higher than Kd-s/KOC, emphasizing the significance of DOC in phase partitioning and transport of FIPs in aquatic environment. Water and sediment samples were more toxic to Chironomus dilutus than Hyallela azteca, and FIPs (especially fipronil sulfone) pronouncedly contributed toxicity to C. dilutus. Toxic units (TU) based on freely dissolved concentrations in water determined by solid phase microextraction significantly improved toxicity estimation of FIPs to the invertebrates compared to TUs based on aqueous concentrations. The present study highlights the significance of DOC association on fate and ecological risk of hydrophobic insecticides in lotic ecosystem.

Two liquid phase partitioning bioreactor system for toxicant free water production from phthalates contaminated aqueous medium

Biodegradation of DMP (dimethyl phthalate) and DEP (diethyl phthalate) is a global environmental concern due to their endocrine disrupting nature. In the present study, biodegradation of DEP as the single substrate and a mixture of DMP and DEP as dual substrates were examined in a two-phase partitioning bioreactor (TPPB) using Cellulosimicrobium funkei. The TPPB system was run under batch and fed-batch modes of operation at different initial concentrations of DEP and mixture of DMP and DEP. Under the batch mode of operation, 93% degradation was achieved by C. funkei within 60 h with 38.75 mgL−1h−1 degradation rate. In the fed-batch system, complete degradation was observed up to 3500 mg/L total initial concentration of the phthalates (1500 mg/L DEP and 2000 mg/L DMP) within 24h. Phytotoxicity assessment of the treated water by seed germination and brine shrimp lethality assays revealed a germination index value of 86.17 and 13.33% brine shrimp mortality. Overall, this study revealed a very good potential of the TPPB system for detoxification of endocrine disrupting chemicals in the environment.

The effect of mixed micelle formation on the dynamics of phase partitioning for a polydisperse ethoxylated nonionic surfactant

AbstractMixed surfactants are common in practical applications, and their behaviors are often observed to deviate from the behaviors of pure surfactants with similar average properties in striking, and sometimes unexpected ways. The focus of this work was on exploring the role of mixed micelle formation in a mixed ethoxylated nonionic surfactant on the dynamics of partitioning between immiscible phases. The work examined partitioning of an ethoxylated nonylphenol surfactant between water and tetrachloroethylene (PCE) in a stagnant system at two different phase volume ratios. A model describing partitioning rate was developed and calibrated to experimental data, and then used to predict the long‐term dynamic approach to equilibrium in mixed and pure systems. The work suggests that micelle formation slows partitioning time by limiting the concentration of monomers in water; in pure systems, time to approach equilibrium increases with increasing concentration, but then reaches a maximum. However, in mixed systems, time to approach equilibrium continues to increase with increasing concentration over the physically‐possible concentration range. For the mixed system studied here, partitioning could be expected to take two orders of magnitude longer at very high concentrations than a similar pure system. Because of the similarity of the mathematics, this result might be expected for any monomer‐driven interaction, such as adsorption or interfacial tension reduction.

Phase partition and KPI‐related process monitoring for batch processes using a novel canonical correlation analysis strategy

AbstractKey performance indicators (KPI)‐related process monitoring has been of great significance to ensure product quality and economic benefits for batch processes. Considering that different phases exhibit different characteristics, one of the key issues is how to partition the whole batch process into different phases and characterize them separately by multiple phase models. In order to model and monitor batch processes more accurately and efficiently, a novel canonical correlation analysis (CCA) strategy is proposed in this paper. The phase partition algorithm is designed based on the joint canonical variable matrix (JCVM). Different from previous methods, it considers the time sequence of operation phases and can distinguish the phase switches from dynamics anomalies. Using this algorithm, phases are separated in order from a KPI‐related perspective, revealing high correlation among variables. After phase partition, a novel multi‐phase local neighbourhood standardization CAA (MPLNSCCA) method focusing on KPI is set up for online monitoring, which could further address the misclassification problems. The advantages of the proposed method are illustrated by two case studies, a penicillin simulation platform and an industrial application of Escherichia coli fermentation, respectively.

Physico-chemical parameters of phase separation of the mixture of BSA and triton X 100 in aqueous solutions of monohydroxy compounds

Clouding behavior and thermodynamic properties for the TX 100 + BSA mixture were investigated in aqueous and aq. alcoholic media. In an aqueous environment, the values of cloud point (CP), at which a clear solution becomes cloudy, for TX 100 decreases with augmentation of the concentration of BSA. The reverse result was obtained in the aq. alcoholic media. In this study, we have used ethanol (EtOH), 1-propanol (1-PrOH), and 2-butanol (2-BuOH) as alcohols. The changes of CP values in alcoholic media have been obtained in the following order: CPH2O+EtOH > CPH2O+2−BuOH > CPH2O+1−PrOH. The standard free energy (∆Gco), standard enthalpy (∆Hco), and standard entropy (∆Sco) changes of clouding were derived at CP. The ΔGc0 values of TX 100 + BSA decreases in the aqueous and alcoholic media with increasing the concentration of BSA and alcohol. This process becomes endothermic in the aq. alcoholic media. Different thermodynamic properties of transfer and entropy-enthalpy compensation parameters for the phase partitioning of the TX 100 + BSA mixture have been calculated and assessed properly.

Multivalent interactions between molecular components involved in fast endophilin mediated endocytosis drive protein phase separation

A specific group of transmembrane receptors, including the β1-adrenergic receptor (β1-AR), is internalized through a non-clathrin pathway known as Fast Endophilin Mediated Endocytosis (FEME). A key question is: how does the endocytic machinery assemble and how is it modulated by activated receptors during FEME. Here we show that endophilin, a major regulator of FEME, undergoes a phase transition into liquid-like condensates, which facilitates the formation of multi-protein assemblies by enabling the phase partitioning of endophilin binding proteins. The phase transition can be triggered by specific multivalent binding partners of endophilin in the FEME pathway such as the third intracellular loop (TIL) of the β1-AR, and the C-terminal domain of lamellipodin (LPD). Other endocytic accessory proteins can either partition into, or target interfacial regions of, these condensate droplets, and LPD also phase separates with the actin polymerase VASP. On the membrane, TIL promotes protein clustering in the presence of endophilin and LPD C-terminal domain. Our results demonstrate how the multivalent interactions between endophilin, LPD, and TIL regulate protein assembly formation on the membrane, providing mechanistic insights into the priming and initiation steps of FEME.

Deep eutectic solvents based biorefining of Value-added chemicals from the diatom Thalassiosira andamanica at room temperature

The extraction and biorefining of value-added chemicals from bioresources using green solvents are among the key agenda of the circular bioeconomy. Herein we have developed a deep eutectic solvent (DESs) based biorefining approach for clean separation and purification of value-added Fucoxanthin, Chlorophyll, and Biosilica from a diatom microalgae, Thalassiosira andamanica. Several hydrophilic/hydrophobic (DESs) based on quaternary ammonium salt as hydrogen bond acceptor and organic acids and alcohols as hydrogen bond donors were synthesized and tested for microalgae biomass dissolution and biorefining via the phase partitioning method. In an optimized process, ∼30 wt% of fresh weight diatom could be dissolved in hydrophilic DESs at room temperature, followed by a record extraction of 19.93 mg/g of Fucoxanthin via phase partitioning, with a 53 % increase in yield and an 81 % increase in selectivity over conventional solvents. 1H NMR, FTIR, LCMS, UV, and HPLC techniques were used to characterize the extracted Fucoxanthin. Subsequently, a hydrophobic DES was added to the remaining hydrophilic DESs and residual biomass and Chlorophyll were extracted into the upper hydrophobic DES layer and Biosilica (80 mg/g) was recovered by simple centrifugation. Extracted Biosilica showed an excellent adsorption capacity of 224.71 mg/g for the removal of methylene blue (MB) dye from water (94.3% up to 88.8 % after 4th consecutive steps). Whereas Chlorophyll extracted in the hydrophobic DES phase exhibited excellent photostability (6 folds greater than conventional solvent) indicating the efficacy of DESs as photoprotector for light-sensitive pigments. This is the first report wherein besides an extractant DES also acted as a good photostabilizer. Additionally, we have replaced the acid-based extraction method for Biosilica with non-toxic DESs.

Estimating remobilization of potentially toxic elements in soil and road dust of an industrialized urban environment.

The mobility of potentially toxic elements (PTEs) is of paramount concern in urban settings, particularly those affected by industrial activities. Here, contaminated soils and road dusts of the medium-size, industrialized city of Volos, Central Greece, were subjected to single-step extractions (0.43M HNO3 and 0.5M HCl) and the modified BCR sequential extraction procedure. This approach will allow for a better understanding of the geochemical phase partitioning of PTEs and associated risks in urban environmental matrices. Based on single extraction procedures, Pb and Zn exhibited the highest remobilization potential. Of the non-residual phases, the reducible was the most important for Pb, and the oxidizable for Cu and Zn in both media. On the other hand, mobility of Ni, Cr, and Fe was low, as inferred by their dominance into the residual fraction. Interestingly, we found a significant increase of the residual fraction in the road dust samples compared to soils. Carbonate content and organic matter controlled the extractabilities of PTEs in the soil samples. By contrast, for the road dust, magnetic susceptibility exerted the main control on the geochemical partitioning of PTEs. We suggest that anthropogenic particles emitted by heavy industries reside in the residual fraction of the SEP, raising concerns about the assessment of this fraction in terms of origin of PTEs and potential environmental risks. Conclusively, the application of sequential extraction procedures should be complemented with source identification of PTEs with the aim to better estimate the remobilization of PHEs in soil and road dust influenced by industrial emissions.

Liquid Phase Partitioning in Virus Replication: Observations and Opportunities.

Viruses frequently carry out replication in specialized compartments within cells. The effect of these structures on virus replication is poorly understood. Recent research supports phase separation as a foundational principle for organization of cellular components with the potential to influence viral replication. In this review, phase separation is described in the context of formation of viral replication centers, with an emphasis on the nonsegmented negative-strand RNA viruses. Consideration is given to the interplay between phase separation and the critical processes of viral transcription and genome replication, and the role of these regions in pathogen-host interactions is discussed. Finally, critical questions that must be addressed to fully understand how phase separation influences viral replication and the viral life cycle are presented, along with information about new approaches that could be used to make important breakthroughs in this emerging field.

Effects of hydroxyapatite addition on corrosion behavior and in-vitro bioactivity of Ti-10Mo matrix biocomposite

Ti-10Mo/HA (hydroxyapatite) biocomposites were prepared by powder metallurgy. The electrochemical corrosion behavior and in-vitro bioactivity were investigated in this study. After addition of HA, the results of the electrochemical tests show that the corrosion resistance of the composites decrease. The non-uniform distribution of β phase region (Mo rich) and partition effect of pores lead to the inhomogeneity and discontinuity of oxide films on the surface of titanium alloy matrix. The introduction of O and incomplete diffusion of Mo make much more α-Ti reserved, which is inferior to β-Ti in terms of the corrosion resistance. Besides, the large and interconnected pores in the composites may cause the crevice corrosion. With addition of HA, the increased ceramic phases and micropores improve the bioactivity obviously. After soaking in SBF for 7 d, a lot of spherical apatite was deposited on the surface of Ti-10Mo/HA composite, while the modified Ti-10Mo alloy was partially covered by several apatite particles. The ceramic phases and micropores enhance the surface energy of the composites, and the wettability is improved, which is conducive to apatite deposition and cell adhesion, but unfavorable to the corrosion resistance. So that the HA content should be controlled in a reasonable range according to the performance requirements of the composites.

The Ice Particle and Aggregate Simulator (IPAS). Part III: Verification and Analysis of Ice–Aggregate and Aggregate–Aggregate Collection for Microphysical Parameterization

Abstract The Ice Particle and Aggregate Simulator (IPAS) is used to theoretically represent the aggregation process of ice crystals. Aggregates have a variety of formations based on initial ice particle size, shape, and falling orientation, all of which influence water phase partitioning. Aggregate dimensional properties and density changes are calculated for monomer–monomer (MON–MON), monomer–aggregate (MON–AGG), and aggregate–aggregate (AGG–AGG) collection to be used by ice-microphysical models for improvement in aggregation parameterizations. Aggregates are chosen from a database of 9 744 000 preformed combinations to be further collected (see Part II). AGG–AGG collection results in more extreme and a smaller range of aggregate aspect ratios than MON–AGG collection. A majority of aggregates are closer to prolate than oblate spheroids, regardless of collection type, except for quasi-horizontally oriented particles that have extreme aspect ratios to begin with. MON–AGG collection frequently results in an increase in density upon collection, whereas MON–MON and AGG–AGG collection almost always result in particle density decreases, with extreme reductions near 99% for MON–MON collection. MON–MON collection results in the greatest decreases in density but then quickly becomes unaffected by the addition of more monomers due to inherent size differences between monomers and aggregates. Finally, a holistic analysis to in situ observations of cloud particle images is presented. IPAS 2D aspect ratios surround a median value of 0.6 and closely follow that of previous studies while varying by no more than ≈12% on average from observed aggregates.

Effect of ion partitioning on an oscillatory electro-osmotic flow on solute transport process of fractional Jeffrey fluid through polyelectrolyte-coated nanopore with reversible wall reaction

The ion-partitioning effects on solute transport phenomena of time-periodic electro-osmotic flow in fractional Jeffrey fluid are investigated through a polyelectrolyte layer (PEL)-coated conical nanopore within a reactive wall whose ends are connected with two large reservoirs. By considering the ion-partitioning effects, analytical solutions for the induced potential and the axial velocity are presented, respectively, from the modified Poisson–Boltzmann equation and the Cauchy momentum equation with the proper constitutive equation of the fractional Jeffrey fluid model in the exterior and interior of the PEL. The analytic solution of the convection–diffusion for solute transport is established in the entire domain. The influence of the oscillating Reynolds number Rew, permittivity ratio εr between two mediums, relaxation time λ1ω, retardation time λ2ω, phase partitioning coefficient σp, PEL fixed charge density qfix, Debye–Hückel parameter κa, and softness parameter λs are investigated in this study. Asymptotic solution for the axial velocity was also presented for low-oscillating Reynolds numbers and validated. The maximum axial velocity occurs when the permittivity between the PEL and electrolyte is the same for all models. The volumetric flow rate decreases with the increase in the PEL thickness, positive PEL charge density, and softness parameter in our study. The volume flow rate of the Newtonian fluid increased 24.07% for Maxwell fluid (λ1ω=5, α = 1) and 11.56% for Jeffrey fluid (λ1ω=5, λ1ω=1, α = 1, and β=0.5), when κa=25, Rew = 10, qfix = 5, d = 0.2, εr=0.6, and λs=1.0. The mass transport rate increases with relaxation time, tidal displacement, and permittivity ratio between these layers.

Henry's Law Constants and Indoor Partitioning of Microbial Volatile Organic Compounds.

Microbial volatile organic compounds (MVOCs) play an essential role in many environmental fields, such as indoor air quality. Long-term exposure to odorous and toxic MVOCs can negatively affect the health of occupants. Recently, the involvement of surface reservoirs in indoor chemistry has been realized, which signifies the importance of the phase partitioning of volatile organic pollutants. However, reliable partition coefficients of many MVOCs are currently lacking. Equilibrium partition coefficients, such as Henry's law constant, H, are crucial for understanding the environmental behavior of chemicals. This study aims to experimentally determine the H values and their temperature dependence for key MVOCs under temperature relevant to the indoor environment. The H values were determined with the inert gas-stripping (IGS) method and variable phase ratio headspace (VPR-HS) technique. A two-dimensional partitioning model was applied to predict the indoor phase distribution of MVOCs and potential exposure pathways to the residences. The findings show that the MVOCs are likely distributed between the gas and weakly polar (e.g., organic-rich) reservoirs indoors. Temperature and the volume of reservoirs can sensitively affect indoor partitioning. Our results give a more comprehensive view of indoor chemical partitioning and exposure.

Purification of Polyphenol Oxidase from Tea Leaf by Three Phase Partitioning and Enzymatic Properties

Purification of Polyphenol Oxidase from Tea Leaf by Three Phase Partitioning and Enzymatic Properties

Hydrogen chloride (HCl) at ground sites during CalNex 2010 and insight into its thermodynamic properties.

Gas phase hydrogen chloride (HCl) was measured at Pasadena and San Joaquin Valley (SJV) ground sites in California during May and June 2010 as part of the CalNex study. Observed mixing ratios were on average 0.83 ppbv at Pasadena, ranging from below detection limit (0.055 ppbv) to 5.95 ppbv, and were on average 0.084 ppbv at SJV with a maximum value of 0.776 ppbv. At both sites, HCl levels were highest during midday and shared similar diurnal variations with HNO3. Coupled phase partitioning behavior was found between HCl/Cl- and HNO3/NO3 - using thermodynamic modelling and observations. Regional modeling of Cl- and HCl using CMAQ captures some of the observed relationships but underestimates measurements by a factor of 5 or more. Chloride in the 2.5-10 μm size range in Pasadena was sometimes higher than sea salt abundances, based on co-measured Na+, implying that sources other than sea salt are important. The acid-displacement of HCl/Cl- by HNO3/NO3 - (phase partitioning of semi-volatile acids) observed at the SJV site can only be explained by aqueous phase reaction despite low RH conditions and suggests the temperature dependence of HCl phase partitioning behavior was strongly impacted by the activity coefficient changes under relevant aerosol conditions (e.g., high ionic strength). Despite the influence from activity coefficients, the gas-particle system was found to be well constrained by other stronger buffers and charge balance so that HCl and Cl- concentrations were reproduced well by thermodynamic models.

Integrated green one-step strategy for concurrent recovery of phycobiliproteins and polyunsaturated fatty acids from wet Porphyridium biomass

A novel and green one-step simultaneous extraction process of phycobiliproteins and polyunsaturated fatty acids (PUFAs) from wet Porphyridium biomass has been done and optimized by using three phase partitioning (TPP) process. Results showed that the coupling of ammonium sulfate and protein buoyancy-promoting t-butanol afforded the best TPP to extract phycobiliproteins and PUFAs in term of the extraction performance and cost-effectiveness. TPP process gave the best capability to simultaneously extract Porphyridium-derived phycobiliproteins and PUFAs in 20% ammonium sulfate, 0.5% biomass, and 1:0.5 slurry to t-butanol ratio at 100 rpm and 20 °C for 10 min of extraction time. Moreover, the established TPP system achieved excellent reproducibility in the extraction of Porphyridium biomass from different sources (Porphyridium cruentum and P. purpureum); and was successfully implemented in pilot-scale (20-L), indicating its industrial potential as a promising integrated approach to comprehensively exploit Porphyridium as a renewable bioresource for high-value bioproducts.

Acidity of Size-Resolved Sea-Salt Aerosol in a Coastal Urban Area: Comparison of Existing and New Approaches

Aging of sea-salt aerosol and the corresponding phase partitioning behavior of HCl/Cl– were monitored and studied in the Halifax Fog and Air Quality Study (HaliFAQS) field campaign in Canada in the early summer of 2019. Ionic chemical composition of ambient aerosol from total suspended particles (TSPs) to 10 nm was sampled and measured into 14 size ranges, which showed that aerosol at the sampling location was mainly composed of sea-salt constituents with little influence from anthropogenic emissions of secondary inorganic precursors. The size-resolved pH of aged sea-salt aerosol was calculated by Extended Aerosol Inorganic Model (E-AIM) IV and a newly derived method based on the measurement of NH3/NH4+ and HNO3/NO3– or HCl/Cl– coupled phase partitioning behavior. The latter pH calculation method does not require information about the aerosol liquid water content or complete water-soluble ion measurement, compensating for the role of oxidized organics to influence the proton activity. In comparison, E-AIM calculation requires the input of all major hygroscopic species. The size-resolved pH calculated by E-AIM IV generally agrees with the one calculated by NH3–HCl coupled phase partitioning. The sensitivities of HCl and HNO3 phase partitioning to aerosol pH are studied with both observational data and conceptual modeling, which gives evidence that the phase partitioning of HCl is more sensitive and therefore more reflective of aerosol pH changes than HNO3 in sea-salt dominated atmospheres where particles typically have pH > 3. The higher concentration and more reliable measurement also make HCl a more suitable choice to track pH changes in this study.

Understanding the Extratropical Liquid Water Path Feedback in Mixed-Phase Clouds with an Idealized Global Climate Model

AbstractA negative shortwave cloud feedback associated with higher extratropical liquid water content in mixed-phase clouds is a common feature of global warming simulations, and multiple mechanisms have been hypothesized. A set of process-level experiments performed with an idealized global climate model (a dynamical core with passive water and cloud tracers and full Rotstayn–Klein single-moment microphysics) show that the common picture of the liquid water path (LWP) feedback in mixed-phase clouds being controlled by the amount of ice susceptible to phase change is not robust. Dynamic condensate processes—rather than static phase partitioning—directly change with warming, with varied impacts on liquid and ice amounts. Here, three principal mechanisms are responsible for the LWP response, namely higher adiabatic cloud water content, weaker liquid-to-ice conversion through the Bergeron–Findeisen process, and faster melting of ice and snow to rain. Only melting is accompanied by a substantial loss of ice, while the adiabatic cloud water content increase gives rise to a net increase in ice water path (IWP) such that total cloud water also increases without an accompanying decrease in precipitation efficiency. Perturbed parameter experiments with a wide range of climatological LWP and IWP demonstrate a strong dependence of the LWP feedback on the climatological LWP and independence from the climatological IWP and supercooled liquid fraction. This idealized setup allows for a clean isolation of mechanisms and paints a more nuanced picture of the extratropical mixed-phase cloud water feedback than simple phase change.