Precipitation Systems Research Articles

The precipitation distribution set by eddy fluxes: the case of boreal winter

The latitudinal precipitation distribution shows a secondary peak in midlatitudes and a minimum in the subtropics. This minimum is widely attributed to the descending branch of the Eulerian Hadley cell. This study however shows that the precipitation distribution aligns more closely with the transformed Eulerian mean (TEM) vertical motion. In Northern Hemisphere winter, maximum TEM descent (ascent) and precipitation minimum (maximum) are collocated at ~20°N (~40°N). The subtropical descent is mostly driven by the meridional flux of zonal momentum by large-scale eddies, while the midlatitude ascent is driven by the meridional flux of heat by the eddies. When the poleward eddy momentum flux is sufficiently strong, however, the secondary precipitation peak shifts to 60°N corresponding to the location of the TEM ascent driven by the eddy momentum flux. Moisture supply for the precipitation is aided by evaporation which is enhanced where the TEM descending branch brings down dry air from the upper troposphere/lower stratosphere. This picture is reminiscent of dry air intrusions in synoptic meteorology, suggesting that the descending branch may embody a zonal mean expression of dry air intrusions. Moist air rises following the TEM ascending branch, suggesting that the ascending branch may be interpreted as a zonal mean expression of warm conveyor belts. This study thus offers a large-scale dynamics perspective of the synoptic description of precipitation systems. The findings here also suggest that future changes in the eddy momentum flux, which is poorly understood, could play a pivotal role in determining the future precipitation distribution.

In Situ X-ray Photoelectron Spectroscopy (XPS) Demonstrated Graphdiyne (g-CnH2n–2) Based GDY-CuI/NiV-LDH Double S-Scheme Heterojunction for Efficient Photocatalytic Hydrogen Evolution

As a new two-dimensional layered carbon material, graphdiyne (GDY) is widely used in various fields because of its excellent electrical conductivity and tunable electronic structure. In this work, graphdiyne, a two-dimensional layered carbon material, is prepared by an alkyl terminal coupling method using Cu+ as a catalyst. Nickel–vanadium hydro calcite (NiV-LDH) is anchored on the surface of GDY-CuI bya solvothermal method to form a double S-scheme heterojunction photocatalytic hydrogen precipitation system. The double S-scheme heterojunction suppressed the electron–hole recombination in the composite catalyst, which greatly improved the transfer rate of photogenerated carriers. Meanwhile, a tight and unique interface is formed in the composite, which not only accelerates the separation and transfer of electron holes but also improves the catalytic stability of the composite. H2 (73.65 μmol) is produced in 5 h in triethanolamine solution, which is 4.1 and 3.7 times higher than those with NiV-LDH and NiV-LDH/CuI. Twenty-five hour cycling experiments demonstrated the catalytic stability of the materials. This work provides an effective strategy for the rational construction and application of graphdiyne group hetero structures in the field of photocatalytic hydrogen evolution.

Climatology and changes in internal intensity distributions of global precipitation systems over 2001–2020 based on IMERG

The internal intensity distributions of precipitation systems are closely related to precipitation dynamics. Understanding its climatology and changing characteristics is important for comprehending climate change, enhancing atmospheric model, and obtaining accurate hydrologic responses. However, due to the various limitations of precipitation observations, the internal intensity distributions of global precipitation systems have not been thoroughly investigated. This study uses the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) data during 2001–2020 to investigate the internal intensity distributions of global precipitation systems, by analyzing the climatology and changes in the radial intensity distributions and the core-region intensity of precipitation systems. The results indicate that precipitation systems with larger spatial sizes tend to have higher intensity. Small- and medium-size precipitation systems exhibit the most obvious changes in the inner regions of precipitation systems, with higher intensity during 2001–2010 than 2011–2020. The large-size precipitation systems have slightly higher intensity at each radius of the systems during 2011–2020. Upon further investigation of the core-region intensity of precipitation systems, the small- and medium-size precipitation systems both exhibit significant decreases during 2001–2020 with trends at −1.13 and −2 mm/h per century, respectively. The large-size precipitation systems exhibit nonsignificant increasing trends during 2001–2020. The results also show regional differences, with decreased core-region intensity over most tropical regions and increased core-region intensity over most subtropical regions. This study provides an alternative perspective on the climatology and changing features of precipitation from the system view, and the results revealed could have significant implications on global climate change.

Novel Biorefinery Approach for Phycocyanin Extraction and Purification and Biocrude Production from Arthrospira platensis.

A new biorefinery from Arthrospira platensis was proposed to obtain phycocyanin (PC) and a biocrude by hydrothermal liquefaction (HTL). PC is a high-added-value phycobiliprotein widely used as a food colorant and in the nutraceutical and pharmaceutical industries. However, the use of conventional solvents in the extraction process and the purity grade of the extract are shortcomings in bioproduct production. PC was extracted using a reusable ionic liquid [EMIM][EtSO4], achieving a PC purity of the lowest commercial grade. Therefore, two downstream processes were applied: (1) dialysis + precipitation and (2) aqueous two-phase system (ATPS) + dialysis + precipitation. After the second purification process, the PC purity increased remarkably to reach the analytical grade for pharmaceutical and nutraceutical applications. The waste biomass (WB) obtained in the PC extraction was valorized by hydrothermal liquefaction (HTL) to produce a biocrude. The biocrude yield and composition remarkably enhanced using isopropanol at 350 °C as a cosolvent.

Vertical Motions Forced by Small-Scale Terrain and Cloud Microphysical Response in Extratropical Precipitation Systems

Abstract Airborne vertically profiling Doppler radar data and output from a ∼1-km-grid-resolution numerical simulation are used to examine how relatively small-scale terrain ridges (∼10–25 km apart and ∼0.5–1.0 km above the surrounding valleys) impact cross-mountain flow, cloud processes, and surface precipitation in deep stratiform precipitation systems. The radar data were collected along fixed flight tracks aligned with the wind, about 100 km long between the Snake River Plain and the Idaho Central Mountains, as part of the 2017 Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment (SNOWIE). Data from repeat flight legs are composited in order to suppress transient features and retain the effect of the underlying terrain. Simulations closely match observed series of terrain-driven deep gravity waves, although the simulated wave amplitude is slightly exaggerated. The deep waves produce pockets of supercooled liquid water in the otherwise ice-dominated clouds (confirmed by flight-level observations and the model) and distort radar-derived hydrometeor trajectories. Snow particles aloft encounter several wave updrafts and downdrafts before reaching the ground. No significant wavelike modulation of radar reflectivity or model ice water content occurs. The model does indicate substantial localized precipitation enhancement (1.8–3.0 times higher than the mean) peaking just downwind of individual ridges, especially those ridges with the most intense wave updrafts, on account of shallow pockets of high liquid water content on the upwind side, leading to the growth of snow and graupel, falling out mostly downwind of the crest. Radar reflectivity values near the surface are complicated by snowmelt, but suggest a more modest enhancement downwind of individual ridges. Significance Statement Mountains in the midlatitude belt and elsewhere receive more precipitation than the surrounding lowlands. The mountain terrain often is complex, and it remains unclear exactly where this precipitation enhancement occurs, because weather radars are challenged by beam blockage and the gauge network is too sparse to capture the precipitation heterogeneity over complex terrain. This study uses airborne profiling radar and high-resolution numerical simulations for four winter storms over a series of ridges in Idaho. One key finding is that while instantaneous airborne radar transects of the cross-mountain flow, vertical drafts, and reflectivity contain much transient small-scale information, time-averaged transects look very much like the model transects. The model indicates substantial surface precipitation enhancement over terrain, peaking over and just downwind of individual ridges. Radar observations suggest less enhancement, but the radar-based assessment is uncertain. The second key conclusion is that, even though orographic gravity waves are felt all the way up into the upper troposphere, the orographic precipitation enhancement is due to processes very close to the terrain.

Can Differently Stabilized Silver Nanoparticles Modify Calcium Phosphate Precipitation?

Calcium phosphates (CaPs) composites with silver nanoparticles (AgNPs) attract attention as a possible alternative to conventional approaches to combating orthopedic implant-associated infections. Although precipitation of calcium phosphates at room temperatures was pointed out as an advantageous method for the preparation of various CaP-based biomaterials, to the best of our knowledge, no such study exists for the preparation of CaPs/AgNP composites. Motivated by this lack of data in this study we investigated the influence of AgNPs stabilized with citrate (cit-AgNPs), poly(vinylpyrrolidone) (PVP-AgNPs), and sodium bis(2-ethylhexyl) sulfosuccinate (AOT-AgNPs) in the concentration range 5-25 mg dm-3 on the precipitation of CaPs. The first solid phase to precipitate in the investigated precipitation system was amorphous calcium phosphate (ACP). The effect of AgNPs on ACP stability was significant only in the presence of the highest concentration of AOT-AgNPs. However, in all precipitation systems containing AgNPs, the morphology of ACP was affected, as gel-like precipitates formed in addition to the typical chain-like aggregates of spherical particles. The exact effect depended on the type of AgNPs. After 60 min of reaction time, a mixture of calcium-deficient hydroxyapatite (CaDHA) and a smaller amount of octacalcium phosphate (OCP) formed. PXRD and EPR data point out that the amount of formed OCP decreases with increasing AgNPs concentration. The obtained results showed that AgNPs can modify the precipitation of CaPs and that CaPs properties can be fine-tuned by the choice of stabilizing agent. Furthermore, it was shown that precipitation can be used as a simple and fast method for CaP/AgNPs composites preparation which is of special interest for biomaterials preparation.

Diurnal cycle of precipitation over the southeastern Tibetan Plateau and surrounding regions: Insights from intensity–frequency structure

AbstractBesides the respective importance of the frequency, intensity and diurnal cycle of precipitation, the diurnal cycle of intensity–frequency structure could reveal more physical details about the evolution process of precipitation systems. Here, an objective method to quantitatively depict the diurnal cycle of intensity–frequency structure of precipitation is proposed, and applied to complex terrains of the southeastern Tibetan Plateau (TP) and its surroundings. Results show the diurnal cycle of precipitation over the high terrain has a unimodal night peak, while low terrain with a frequency‐dominated night peak and an intensity‐dominated afternoon peak. Both weak and intense precipitation are more frequent at night than those in the afternoon over unimodal regions compared to bimodal regions. Further analysis reveals different diurnal evolution process of intensity–frequency structure within unimodal and bimodal regions, respectively, which reflects different spatiotemporal traits and evolution process of precipitation. Among unimodal regions, the elevated southeastern TP is featured by the synchronous decrease in both weak and intense precipitation from the night peak to the afternoon minimum. While the decrease of total precipitation in regions with lower terrain is dominated by the decrease of intense precipitation, but with an increase in weak precipitation simultaneously. Regarding bimodal regions, the intense precipitation over southern Hengduan Mountains has a more prominent role in leading the diurnal cycle of precipitation amount, compared with that over the southeastern Yungui Plateau. The proposed method provides a new perspective with more physical details to investigate precipitation characteristics in complex terrains, which could be further used to reasonably evaluate and improve the performance of numerical models.

Diverging identifications of extreme precipitation events from satellite observations and reanalysis products: A global perspective based on an object-tracking method

Extreme precipitation can trigger various natural hazards, causing catastrophic losses worldwide. As global warming accelerates, it is widely acknowledged that extreme precipitation will become more frequent and intense, calling for more accurate historical and projected precipitation estimation. Identifying extreme precipitation events is understudied particularly on the global scale, given that most studies only focus on pixel-by-pixel characteristics while ignoring the space-time continuity and evolution of extreme events. This study utilizes an object-based tracking method to track the precipitation system objects in time, extracting spatiotemporal attributes of precipitation events and investigates variable definitions of extremes for a better understanding of the performance of existing precipitation datasets. Five satellite and two reanalysis precipitation products (IMERG, GSMaP, PERSIANN-CCS, TRMM 3B42, CMORPH, ERA5, and ERA-Interim) are involved to investigate (1) the difference and similarity of those datasets in depicting the global pattern of extreme precipitation, (2) the impact of various definitions of extreme events, and (3) the trend of global extreme precipitation events. Results show that the object-based method can capture the motion of precipitation events. Different extreme definitions have a large impact on the distribution, trend, and features of extreme precipitation. The inter-comparison of extreme precipitation events from different products shows low correlation, indicating that accurately capturing the evolution of extreme events is still challenging. Reanalysis product-based analysis shows variable trends (magnitudes and signs) based on different attributes of precipitation objects and notable scale effect. Satellite precipitation products exhibit distinct inter-annual variability which could affect their hydrometeorological applications. In summary, this study leverages the object-based tracking method for comprehensive extreme precipitation analysis from the multi-dataset, multi-scale, and multi-definition perspectives, which can advance the understanding of the status and trend of global extreme precipitation.

Impact of changes in refractive indices of secondary organic aerosols on precipitation over China during 1980–2019

Secondary organic aerosols (SOAs), which include both colorless and colored carbonaceous aerosols, represent a major type of aerosol globally. Previous studies have reported that colored aerosols drive the well-known precipitation changes over southern China called the south-flood north-drought (SFND). Considering the highest concentration of SOA in China, SOAs can cause fluctuations in the precipitation system over China. However, studies on the climatic effects of SOAs over East Asia are scarce owing to the chemical complexity of SOAs and high computational cost. Therefore, to investigate the effect of SOAs on the precipitation change over China, we implemented an SOA scheme using empirical parameters in the chemistry-climate model. We performed a control and two sensitivity simulations depending on the difference in refractive indices of SOAs to elucidate the effects of light absorption by SOAs on precipitation. Our results suggest that strong light absorption by SOAs strengthens the convective precipitation over southern China following the enhancement of atmospheric stability with a secondary circulation effect. However, the surface temperature changes caused by SOAs shift the jet core if weak light absorption by SOAs is assumed, causing a strong downdraft in the mid-troposphere and decreasing humidity over south-eastern China. Therefore, precipitation was significantly reduced over southern China. Our results show that light-absorbing SOAs have had a significant impact on precipitation in southern China for the past few decades. Furthermore, the apparent difference in mechanisms of precipitation change between strong and weak light absorption by SOAs suggests the importance of choosing suitable refractive indices for SOAs in the climate–atmospheric chemistry model.

Subseasonal Variations of Convective and Microphysical Characteristics of Extreme Precipitation Over the Pearl River Delta at Monsoon Coast

AbstractThe large‐scale flows and rainfall pattern change markedly with the progression of the summer monsoon, but how the convective and microphysical characteristics of monsoon extreme precipitation vary subseasonally remains elusive. This study compares 16,844 extreme precipitation features (EPFs) among the pre‐monsoon, active‐monsoon, post‐monsoon periods, and tropical cyclone (TC) days using multisource data including dual‐polarimetric radar observations over the Pearl River Delta in South China. Results indicate that the environmental dynamics and thermodynamics significantly influence the EPFs' convective and microphysical properties. Despite the similar environmental conditions such as abundant moisture and moderate to large convective available potential energy (CAPE) under which the EPFs occur, differences among the four periods are noticed. During the pre‐monsoon period, precipitation systems are the largest in area but their EPFs are the least frequent and have the lowest raindrop concentration, likely due to the colder and drier environment with large vertical wind shear (VWS). The onset of the summer monsoon increases both the frequency and the convective intensity of EPFs, leading to an increase in raindrop size, which is consistent with the substantial increases of CAPE and moisture during the active‐monsoon period. The EPFs share similar convective intensity and raindrop size distribution (RSD) between the post‐monsoon and the active‐monsoon periods, although the post‐monsoon EPFs are slightly less frequent and have a smaller horizontal scale related to the reduced 0–6‐km VWS. Interestingly, EPFs associated with TCs have the weakest convective intensity but the most active warm‐rain processes with the RSD being closer to the maritime regime.

Mapping the representativeness of precipitation measurements in Mainland China

Meteorological observations provide essential data for weather forecasting and climate change studies. Whether the measured data can accurately support such applications closely relates to the representativeness of the data collected, which depends on both the scale of observation and the density of the measurement network. Precipitation presents in the form of events and is discontinuous both in time and space. Gauge observations of precipitation could provide fundamental data but have difficulty quantitatively assessing precipitation system scale. Therefore, assessments on the representativeness of precipitation at synoptic and climatological scales remain needed. Here, we show the first high-resolution map of the representativeness of precipitation over Mainland China based on the latest satellite data. Our results show that the daily precipitation spatial consistency is the highest in eastern China and lowest on the Tibetan Plateau. However, the pattern of the monthly spatial consistency is different and is the highest over Northeast China Plain, the Loess Plateau, and the Middle–Lower Yangtze Plain. Compared to the density of rain gauges, we find that the current national station network with ∼2400 stations still has difficulty supporting synoptic studies in western China. However, for climate change studies based on monthly data, the density of the national reference climatological station network is sufficient, except in the western Tibetan Plateau and deserts with no available stations. For climatological studies, the quality of precipitation gauge observations is more important than its spatial density. Our results could provide great practical significance for considering the layout of rain gauges.

Coprecipitation Synthesis of Large-Pore-Volume γ-Alumina Nanofibers by Two Serial Membrane Dispersion Microreactors with a Circulating Continuous Phase

A coprecipitation method was developed for the synthesis of fibrous γ-alumina using serial membrane dispersion microreactors with a circulating continuous phase and high concentrations of NaAlO2 and Al2(SO4)3 as reactants. Owing to the ultra-high mixing intensity and reduction of supersaturation due to the large circular phase ratio, a large pore volume and specific surface area and an extremely narrow pore diameter distribution were realized using the high-concentration and high-viscosity precipitation system. The influence of the phase ratio, dispersion order of reactants, Al2(SO4)3 residence time, and the precipitation reaction pH and time were investigated, and the nanofiber formation mechanism was explored employing theoretical calculations. By controlling the Al2(SO4)3 residence time of 3 s, phase ratio of 16, and pH of 8.0, γ-Al2O3 nanofibers with a pore volume of 1.36 cm3/g, a specific surface area of 376 m2/g, and a length/diameter ratio in the range of 30–54 were obtained without any organic reagents. This study provides an economical and readily scalable method for the synthesis of fibrous γ-Al2O3 with excellent pore properties and a large specific surface area, which can potentially be applied as an excellent catalyst support for diesel and bio-oil hydrogenation.

Induced-charge electroosmosis for rapid mixing of reactive precipitation systems to obtain small and uniform particles

The control of product quality in precipitation systems is often difficult due to high supersaturation levels and fast kinetics. Rapid and uniform mixing of fluids is required to minimize supersaturation gradients before the onset of nucleation. This study proposes an active mixing platform utilizing induced-charge electroosmosis (ICEO) to better control crystal quality attributes such as the size distribution. The mixing performance of the ICEO-based micromixer is characterized through experiments as a function of the solution properties and the electric field parameters such as phase angle, frequency, and voltage. Optimal mixing is achieved at lower conductivities when the phase difference is 180°. Furthermore, computational fluid dynamics simulations demonstrate that uniform supersaturation is achieved at shorter mixing lengths of the device along with a narrower residence time distribution in the presence of ICEO. Additionally, the performance of the ICEO-based crystallizer is demonstrated for the reactive precipitation of silver chloride particles and carbamazepine-succinic acid cocrystals. The application of ICEO leads to the production of smaller silver chloride particles with a narrower size distribution and an improved yield for cocrystallization compared to cases without ICEO. The ICEO-based micromixer characterized in this work is generally attractive for the continuous production of particles through reactive precipitation with stringent requirements on product uniformity and yield.

FPCI and SPCI Are Proposed to Distinguish the Frontal and Saturated Precipitation Systems Based on FY-4A

Infrared (IR) observations from geostationary satellites have been widely used in estimating the precipitation with high spatiotemporal resolutions. Currently, it is acknowledged that single-channel IR observations are capable to extract the properties of cloud tops, while are insufficient for deeper vertical information. However, based on developments of multispectral IR imagers onboard geostationary satellites, distinguishing different precipitation regions with different vertical structures becomes possible, which has not been fully explored yet. Therefore, combining FY-4A/AGRI and GPM/DPR, we innovatively proposed Frontal Precipitation Cloud Index (FPCI) and Saturated Precipitation Cloud Index (SPCI) for IR signals by exploiting the characteristic responses of channel combinations to different precipitation systems. It is proved that multispectral IR observations are capable of responding to certain precipitation systems with different vertical structures. Meanwhile, IR imagers onboard geostationary satellites have significant advantages on tracking developing processes of precipitation systems with high spatiotemporal resolutions than microwave detectors onboard low-earth-orbit satellites. In addition, this study is beneficial for impelling IR precipitation estimation to consider more radiation-based physical theory, especially for FY-4A official precipitation product.

The Investigation of the Mechanical Properties of EICP-Treated Sand Specimens Prepared by a Double-Reservoir Injection System for Uniform Precipitation of Carbonate via Triaxial Tests

Abstract The injection condition of enzymatic-induced carbonate precipitation (EICP) grouting for uniform precipitation and the mechanical properties of EICP-treated soil specimens were investigated in this study. Urease derived from yellow soybeans was used as the catalyst for the precipitation of the carbonate instead of the expensive purified urease commonly used. The uniformity of the calcium carbonate distribution was investigated by measuring the calcium carbonate content at various locations within the EICP-treated soil specimens through the soil column injection tests. The results showed that the uniformity of the calcium carbonate distribution depends on the reservoir system for the storage of the injection solutions and the injection volume that is associated with the colloidal transport of urease. Based on the proposed injection method, the EICP-treated soil specimens were prepared for two soil types and a series of consolidated undrained triaxial compression tests were conducted to investigate the mechanical properties. It was confirmed that the undrained shear behavior of the EICP-treated sand specimens shows more softening behavior. In addition, the use of a high molarity urea-CaCl2 solution resulted in pronounced reinforcing effects on the strength, which included both the peak and residual strength and the stiffness. The effects of the confining pressure and the soil types on the strength and stiffness were also investigated.

Thresholds of Instability: Precipitation, Landslides, and Early Warning Systems in Brazil

Thresholds of Instability: Precipitation, Landslides, and Early Warning Systems in Brazil

Spatiotemporal difference of leachate production and its impact on the development and dynamics of LCS clogging

Due to the complexity of industrial solid waste, heavy metals and organics can be enriched in leachate. While leachate is difficult to handle, it can also cause clog of the leachate collection system (LCS), increasing the risk of leakage. Therefore, it is necessary to study the clogging process of LCS in industrial solid waste landfills (ISWLs). In this study, the prediction of the clogging process and hydraulic conductivity evolution of the LCS in ISWL were carried out through laboratory experiments and model simulations. The results show that the LCS of ISWLs in China faces severe clogging challenges. First, the rate of clogging is inversely proportional to the rate of leachate production. Then, it was found that the main influencing factor was infiltration conditions (precipitation and capping systems). Under accelerated infiltration conditions, the time for complete clogging of the leachate drainage pipes was shortened from the initial 26–735 years to 11–315 years. The time to complete LCS clogging was shortened from the initial 78–2205 years to 32–945 years. In addition, the acceleration of the clogging process was fully consistent with the increase in leachate production. In particular, when the net infiltration volume increases from 0 to 50 mm, the clogging process is significantly accelerated. After greater than 50 mm, the effect on the clogging process gradually decreases. This provides a reliable theoretical basis for accurately predicting the clogging process of LCS.

Impact of Assimilating Radar Data with 3D Thermodynamic Fields in an Ensemble Kalman Filter: Proof of Concept and Feasibility

Abstract This study examined the impact of assimilating 3D temperature and water vapor information in addition to radar observations in a multiscale weather system. A frontal system with extremely heavy rainfall over northern Taiwan was selected. Using the WRF–LETKF Radar Assimilation System, we performed three sets of observing system simulation experiments to assimilate radar observations with or without thermodynamic variables obtained using different methods. First, assimilating the radar data for 2 h showed better structure and short-term forecast than 1 h. Second, we assimilated radar data and thermodynamic variables from a perfect model simulation. The results of the analysis revealed that when a precipitation position error occurred in the background field, assimilating thermodynamic information with the radar data could correct the dynamic structure and shorten the spinup assimilation period, resulting in substantial improvements to the quantitative precipitation forecast. Third, we applied a thermodynamics retrieval algorithm for a feasibility study. With a warm and wet bias of the retrieved fields, assimilating the temperature data had significant impact on the midlevel of stratiform areas and the forecast of the heavy rainfall was consequently improved. Assimilating the water vapor information helped reconstruct the range and intensity of the cold pool, but the improvement of rainfall forecast was limited. The optimal results of analysis and short-term forecast were achieved when both retrieved temperature and water vapor fields were assimilated. In conclusion, assimilating thermodynamic variables in the precipitation system is feasible for shortening the spinup period of data assimilation and improving the analysis and short-term forecast.

Efficient and green water softening by integrating electrochemically accelerated precipitation and microfiltration with membrane cleaning by periodically anodic polarization

• An efficient and reagent-free EAPS-MF system was developed for water softening. • A hydrophilic PTFE membrane was used as the separation medium in electrolysis cell. • The Ti microfilter with membrane cleaning by anodic polarization was used for CaCO 3 interception. • CaCO 3 precipitation rate was 349 g h −1 m −2 at 100 A m −2 with energy consumption of 1.88 kWh kg −1 . Although the electrochemical water softening in the divided cell has been proven capable of avoiding the requirement of high working electrode surface area, its industrial application is seriously constrained by the fouling of the ion exchange membrane and the lack of an environmentally friendly liquid–solid separation method. In this study, an energy-efficient and reagent-free electrochemically accelerated precipitation and microfiltration combined system (EAPS-MF) was developed for water softening. In typical operation mode A, the electrolysis cell divided by a polytetrafluoroethylene microfiltration membrane (PMM), allowing for the simultaneous production of alkaline and acidic effluents. The alkaline effluent was fed directly into the crystallizer for the formation of CaCO 3 crystals, which were intercepted by a Ti tubular microfilter. The filtrate was then blended with acidic effluent to further reduce water scaling potential by removing the residual alkalinity. In this system, the precipitation rate raised from 97.5 to 348.8 gCaCO 3 h −1 m −2 by elevating current density from 20 to 100 A m −2 , accompanying the increased specific energy consumption from 0.68 to 1.88 kWh (kgCaCO 3 ) −1 or from 0.044 to 0.44 kWh m −3 water treated. The Ti tubular membrane fouling was mainly caused by the accumulation of CaCO 3 cake on its surface, which existed in the predominant type of calcite and marginal type of vaterite. Interestingly, the fouled Ti tubular membrane could be recovered completely within 5 min just by periodically anodic polarization at a current density of 200 A m −2 without production of wasted cleaning brine. Generally, the established EAPS-MF system exhibited significant prospects in promoting the applications of the electrochemical softening process in diverse industrial areas.

Origin and Composition of Exosomes as Crucial Factors in Designing Drug Delivery Systems

Exosomes are a subpopulation of extravascular vesicles with a diameter of 30–150 nm. They are cellular-communication mediators, often reaching very distant organism tissues. Information is transferred by exosomal cargo, composed of a wide variety of macromolecules such as nucleic acids, proteins, and lipids. Exosomes possess natural specific cell targeting properties that are desirable in designing targeted macromolecules (DNA and RNA) and drug delivery systems (doxorubicin, paclitaxel, and taxol). In this context, exosomes can be defined as bio-derived drug transporting and protecting devices for the treatment of bacterial (toxoplasmosis and salmonellosis), viral (AIDS and hepatitis B), and cancer (lung, pancreatic, colon, brain, and breast) diseases. Extensive research proves that exosomes’ natural cargo can double-act, both increasing and decreasing the disease severity. In this case, the exosomes need to be prepared, namely, their origin and their cargo need to be screened and known. Thus, appropriate methods for intact and price-effective exosome isolation are needed with further exosome properties description. Among many utilized isolation methods, the most common are ultracentrifugation, polymer-based precipitation, and affinity precipitation-isolation systems, but novel microfluidic methods compromising high efficacy and purity are being developed. In this review, we state the current knowledge and trends in exosome-based drug delivery systems.