Mixing Intensity Research Articles

Influence of mixing conditions on coagulant recovery efficiency and quality

Abstract In this work, the influence of mixing conditions on aluminium recovery from alum sludge and on the recovered coagulant (RC) quality was investigated using acidic treatment. The response surface methodology with a Face Centred Design was used to evaluate the effects of velocity gradient and mixing time on aluminium recovery efficiency, and on the chemical oxygen demand (COD), total suspended solids (TSS) and total phosphorus contents of the RC. No significant effects of both mixing intensity and mixing time on aluminium recovery efficiency were observed; however, these factors significantly affected the quality of the RC in terms of COD, TSS and total phosphorus. The higher velocity gradient increased COD and TSS and the longer mixing time increased phosphorus and TSS in the RC. Operational conditions velocity gradient = 100 s−1 and mixing time = 5 minutes) for aluminium recovery were suggested on economic basis. At these conditions, the RC presented the lowest values of TSS and total phosphorus (100 mg L−1 and 7.0 mg P L−1, respectively), and the following other characteristics: 1,001 mg Al L−1; 384 mg Fe L−1; 1100 mg COD L−1.

On the Optimal Choice of Type of Combustion Chamber for the Initiation of Gas Detonation

A numerical simulation of continuous gas detonation in the combustion chamber based on the Navier-Stokes equations, taking into account turbulence and diffusion of substances, is carried out. A comparative analysis of the efficiency of detonation combustion of fuel depending on the geometric parameters of the chambers is performed. Three possible camera types are considered. Fuel and oxidizer were fed separately into the chambers through nozzles at a certain angle to the chamber surface. The detonation process was largely determined by the intensity of the turbulent mixing of reagents (hydrogen and oxygen). Calculations show that the type of camera with a flat radial geometry is the most optimal to establish a stable detonation regime.

Granular Carbon Adsorbent Based on Soot and Synthetic Pitch

A method for producing granular carbon adsorbent by stirring a suspension of soot in a solution of naphthalene (in heptane) in the presence of sulfuric acid was proposed. Experimental research together with mathematical processing of the results made it possible to propose a mechanism for the formation of spherical carbon granules from soot and naphthalene: in the course of intense mixing in the presence of concentrated sulfuric acid, a binder material was formed from naphthalene, and it was adsorbed on the surface of soot particles. The resulting particles with a thin layer of binding material on their surface stuck together in the field of centrifugal forces to form larger particles, which ultimately acquired a spherical shape and had a size of up to 5 mm. A comparison of the resulting carbon granules (from soot and synthetic pitch) with granules preparedby mixing soot and petroleum pitch showed that the proposed adsorbent had specific surface area and mechanical strength greater by factors of 1.5–2.

A multi-stage enhanced flocculation reactor for the treatment of simulated shale gas hydraulic fracturing flowback fluid: Effect of aspect ratios for the intense mixing section

Flocculation is a significant process in treating shale gas hydraulic fracturing flowback fluids. To achieve a high removal rate of pollutant, a range of multi-stage enhanced flocculation reactors that incorporated sequential intense, moderate, and weak mixing sections along the flow direction were devised, in which the aspect ratios (ARs) in the intense mixing section were varied. The results of the computer simulation indicated that the reactor with AR of 3.5 exhibited a gradual decrease in velocity and energy along the flow direction, and the flow field distribution is highly uniform and symmetrical. The generated flow field promoted the formation of small flocs in the intense mixing section and facilitated the collision of small flocs in the moderate mixing section, while preventing the fragmentation of flocs in the weak mixing section, therefore resulting in the generation of large and compact flocs. Moreover, the generated flocs demonstrated a good resistance to shear and oscillation, facilitating their separation from the simulated flowback fluids. The obtained reactor achieved remarkable removal efficiencies of 80.15 % for COD and 89.06 % for turbidity. Furthermore, when treating bentonite suspension, the multi-stage flocculation reactor achieved a turbidity removal rate of 99.34 % with a processing time of only 2.38 min and a settling time of just 20 min. This demonstrated the broad applicability of this reactor to various types of wastewater. This work provides valuable insights into the design of efficient flocculation reactors by integrating multiple mixing intensities within a reactor.

Effects of Mixing at Pore Intersections on Large‐Scale Dissolution Patterns and Solute Transport

AbstractThe flow‐induced dissolution of porous rocks governs many important subsurface processes and applications. Solute mixing, which determines pore‐scale concentration fields, is a key process that affects dissolution. Despite its importance, the effects of pore‐scale mixing on large‐scale dissolution patterns have not been investigated. Here, we use a pore network model to elucidate the mixing effects on macroscopic dissolution patterns and solute transport. We consider two mixing rules at pore intersections that represent two end members in terms of the mixing intensity. We observe that the mixing effect on dissolution is the strongest at moderate Damköhler number, when the reactive and advective time scales are comparable. This is the regime where wormholes spontaneously appear. Incomplete mixing is shown to enhance flow focusing at the tips of the dissolution channels, which results in thinner wormholes and shorter breakthrough times. These effects on passive solute transport are evident independent of initial network heterogeneity.

Diffusion instability in three-component gas mixtures containing greenhouse gas

The work discusses the influence of pressure and composition of a ternary gas mixture on the possibility of the occurrence of convective instability under isothermal conditions due to differences in the diffusion abilities of the components. The change in “diffusion – concentration gravitational convection” regimes in isothermal ternary gas mixtures CH4 + R12 – Ar, N2 + R12 – n-C4H10 was experimentally studied. It has been shown that instability in the systems under study can occur at a certain content of the component with the highest molecular weight in the mixture. Its further increment in the initial composition of the mixture leads to the emergence of convective flows and an increase in the intensity of mixing. Experiments have confirmed that pressure also determines the transition from a diffusion state to a convective one. A growth in pressure contributes to an increase in the intensity of convective mixing. For a flat vertical channel at certain values of composition and pressure, nonmonotonic concentration distributions causing a significantly nonlinear density distribution with an extremum, which is unusual from the point of view of diffusion, were recorded. The regions of stable and unstable behavior of the system for a wide range of mixture composition and pressure are studied in terms of Rayleigh numbers. The location of the areas where diffusion and instability occur is compared with the results of the experiments.

Desmoid-type fibromatosis of neck masquerading as nerve sheath tumors: two case reports

BackgroundDesmoid fibromatosis (DF) is an atypical, non-malignant tumor known for its distinctive feature of exhibiting an intermediate biological behavior that falls between benign fibrous lesions and fibrosarcoma. The article aimed to outline the imaging characteristics of desmoid fibromatosis and distinguish it from its similar counterpart, nerve sheath tumors.ResultsHere, we present two cases of desmoid fibromatosis whose imaging findings mimic nerve sheath tumors. The patients presented with neck swelling and radiating pain. Both cases were biopsy-proven. Imaging features characteristic of these lesions include elongated shape, split-fat sign, and fascial tail sign with mixed signal intensity on T1WIs and T2WIs depending upon the collagen content of the lesion.ConclusionsMRI is the best diagnostic modality for differentiating fibromatosis from nerve sheath tumors. Surgery continues to be the primary approach for treating these growths, but in some cases, chemoradiation is employed to achieve improved control rates. The presence of intralesional low-intensity bands in T2WIs is a characteristic feature of fibromatosis. Given its local aggressiveness and propensity for recurrence, the use of multiple imaging modalities is essential for providing informed guidance on outcomes and treatment strategies.

A 3D homogeneous microreactor with high mixing intensity at wide Re range for MOF preparation and POCT application

Most microreactors can only work under high Re or extremely low Re conditions to obtain enough mixing efficiency, the inefficient reaction intensity undoubtedly limits its application scenarios. In this study, a novel 3D homogeneous microreactor (3D-HM) was reported that demonstrate a strong mixing intensity over a wide range of Re conditions. The 3D geometries of shunt and lateral secondary flow structure were optimized in details, and then were added to the Zigzag mixing channel to promote mixing index (MI) (over 94 % from Re = 0–10, and more than 98 % for Re > 10). Compared with the traditional T-shaped, Split and Recombine micromixer, a shorter mixing distance (Lmix) and mixing time (τmix) were needed to realize fully mixing. The 3D-HM was used for the preparation of Zeolitic imidazolate framework (ZIF-8), the particle size, yield and drug loading capacity of ZIF-8 prepared using the 3D-HM under a milder Re conditions were better than those prepared by traditional and existing microfluidic methods under a harsh Re conditions. The promotion to diffusion mixing with 3D-HM channel was then verified using the enzymatic catalytic reaction driven by syringe pump at low Re and capillary pump, respectively. Enzyme and substrates in the laminar flow in the 3D-HM are more likely to bind each other than that in the T-shaped diffusion mixing. In addition, the laminar diffusion mixing process was scaled up by microfluidic channel design, so that the results of enzymic catalytic reaction was visualized for Point-of-care Testing (POCT) application. The MI, Lmix and τmix directly determine the homogeneous microreaction intensity. The proposal of the 3D-HM may provide more possibilities for the application of micromixing-based reactors.

Impact of critical eddy diffusivity on seasonal bloom dynamics of Phytoplankton in a global set of aquatic environments

The intensity of eddy diffusivity and the spatial average of water velocity at the depths of the water column in oceans and lakes play a fundamental role in phytoplankton production and phytoplankton and zooplankton biomass, and community composition. The critical depth and intensity of turbulent mixing within the water column profoundly affect phytoplankton biomass, which depends on the sinking characteristic of planktonic algal species. We propose an Nutrient-Phytoplankton-Zooplankton (NPZ) model in 3D space with light and nutrient-limited growth in a micro-scale ecological study. To incorporate micro-scale observation of phytoplankton intermittency in bloom mechanism in stationary as well as oceanic turbulent flows, a moment closure method has been applied in this study. Experimental observations imply that an increase in turbulence is sometimes ecologically advantageous for non-motile planktonic algae. How do we ensure whether there will be a bloom cycle or whether there can be any bloom at all when the existing phytoplankton group is buoyant, heavier, motile, or non-motile? To address these questions, we have explored the effects of critical depth, the intensity of eddy diffusivity, spatial average of water velocity, on the concentration as well as horizontal and vertical distribution of phytoplankton and zooplankton biomass using a mathematical model and moment closure technique. We quantify a critical threshold value of eddy diffusivity and the spatial average of water velocity and observe the corresponding changes in the phytoplankton bloom dynamics. Our results highlight the importance of eddy diffusivity and the spatial average of water velocity on seasonal bloom dynamics and also mimic different real-life bloom scenarios in Mikawa Bay (Japan), Tokyo Bay (Japan), Arakawa River (Japan), the Baltic Sea, the North Atlantic Ocean, Gulf Alaska, the North Arabian Sea, the Cantabrian Sea, Lake Nieuwe Meer (Netherlands) and several shallower lakes.

Validity Test of an Alternative Method of Quantitative Pain Assessment (MAPKN) in Assessing Intensity of Nociceptive Pain, Mixed Pain, and Neuropathic Pain

Pain is a health problem phenomenon that most often brings patients to see a doctor. Pain intensity is the most often domain which assessed in clinical and research settings. Loeser suggests that four elements need to be considered when evaluating patients with pain. Based on the biopsychosocial approach and the concept of pain from Loeser, a pain assessment was made and called "Alternative Method of Quantitative Pain Assessment (MAPKN)". This study was conducted on 415 pain patients consisting of 163 nociceptive pain, 119 mixed pain, and 133 neuropathic pain. In the nociceptive pain group, MAPKN showed sensitivity 92.59%, specificity 96.43%, AUC 0,959 and a p value <0.001. In the mixed pain group, MAPKN showed sensitivity 98.17%, specificity 80.00%, AUC 0,836 and a p -value of 0.001. In the neuropathic pain group, MAPKN showed sensitivity 92.06%, specificity of 85.71%, AUC 0,951 and a p<0.001. The AUC value of 0.959 (96%) indicates that the diagnostic value of the MAPKN score in assessing pain intensity in the nociceptive pain group is excellent (>90%-100%). AUC value of 0.836 (83%) indicates that the diagnostic value of the MAPKN score in assessing pain intensity in the mixed pain group is good (> 80%-90%). The AUC value of 0.951 (95%) indicates that the diagnostic value of the MAPKN score in assessing pain intensity in the neuropathic pain group is excellent (>90%-100%). This is in accordance with research conducted by Eka Pranata 2004 that MAPKN has strong discriminant validity in assessing pain intensity. MAPKN is valid and has excellent diagnostic value in assessing nociceptive and neuropathic pain intensity, MAPKN is valid and has good diagnostic value in assessing mixed pain intensity.

Improved XFEM for 3D interfacial crack modeling

The conventional extended finite element method (XFEM) usually suffers from the crack tip enrichment for removing the blending elements. This may be inconvenient when treating the three dimensional (3D) and curved crack modeling since the crack tip enrichment is usually defined in the local coordinate system depending on the crack front. To avoid these shortcomings of the XFEM, an improved enrichment scheme is proposed for the 3D interfacial crack modeling. The proposed enrichment scheme removes the crack tip enrichment and two weight functions are introduced to capture the strong and weak discontinuities in the element including the crack front. The new enrichment scheme has advantages for the 3D curved interfacial cracks since all the enrichment functions are defined in the global system and it is unnecessary to introduce additional coordinate systems. Several benchmark problems including the mixed mode stress intensity factors (SIFs), anti-plane load and curved cracks are analyzed by the proposed method with the local refinement technology. Numerical results demonstrate that the proposed method can obtain accurate 3D energy release rate and SIFs. In addition, the proposed method enhances the applications of XFEM and has the potential abilities to the multiple-fields coupling and interfacial crack growth phenomena due to the fact that compatible enrichment functions are utilized.

Residence time distribution of an offshore floating photobioreactor under hydrodynamic sloshing effect

Sloshing is the movement of fluid in a partially filled vessel subjected to external motions. Although sloshing causes intense forces and instability to floating structures, the internal motion of liquid caused by external forces might be useful for devices that require mixing. For offshore floating photobioreactors, sloshing induced by external ocean wave forces are desirable, as the movement of liquid is able to bring about mixing and mass transfer for the nutrients and gas in the microalgae culture. The objective of this study is to investigate the correlation between the regular wave-induced sloshing of different motions (surge, heave, and pitch) on the mixing behaviour of the novel offshore floating photobioreactor designed to utilize the ocean surface waves for the effects of mixing. To determine the residence time distribution (RTD) of the stagnant volume of the photobioreactor, dissolved solids were injected into the system. The concentration of dissolved solids was measured using a total dissolve solid (TDS) sensor. The mixing caused by sloshing motion had the highest intensity during pitching motion. A homogenous solution was formed just after 65.9 s for the filling ratio of 30 %, with the rotation angle of 8 degrees and frequency of 0.21 Hz. Thus, wave-induced sloshing is able to generate intense mixing to the medium during pitching motion but still has non-ideal behaviours, such as bypass and dead zones during horizontal and vertical motion.

The flame structure and combustion dynamics in a steam diluted H2/Air micromix flame

The OH* chemiluminescence is used to investigate experimentally the effects of nozzle diameter (d), steam dilution ratio (D) and equivalence ratio (φ) on flame structure and combustion dynamics in a steam diluted H2/air micromix burner. Two flame types, anchored and lifted, are found. The OH* signal for the anchored flame primarily presents in flame shear layer zone (SLZ), while that for the lifted flame mainly appears in the flame central recirculation zone (CRZ) and flame tail zone (FTZ). The increase of the velocity of hydrogen (as the D decreasing or the φ increasing) would change anchored flame to lifted flame. The Power Spectral Density (PSD) analysis shows that changing from anchored to lifted flame would result a high OH* fluctuation frequency, which shows the same trend as the decrease of d. The Dynamic Mode Decomposition (DMD) analysis shows that the distribution of dominant mode is similar to the distribution of OH* signal. The SLZ is the primary oscillation zone for anchored flame and the CRZ for lifted flame. The anchored flame is more stabler comparing to the lifted one, and the lifted flame should be avoided in practical burners. Besides, the high mixing intensity of fuel and oxidizer is beneficial to the stability of micromix flame.

Evaluating the aeration efficiency of hydraulic flume on photo-oxidative disinfection of wastewater

Photosensitized oxidation has been considered to offer better disinfection mechanism under natural sunlight and the efficiency of its inactivation pathway depends on the concentration of dissolving oxygen, the solar irradiance, and the reactive nature of the liquid. This study aimed to evaluate the hydraulic mixer's aeration performance during photo-oxidation treatment. A hydraulic jump was created to aerate the sewage prior to its passage into a reactor, and the amount of dissolved oxygen generated was measured. The effect of mixing intensity on sunlight inactivation of faecal coliforms in a reactor was investigated for 60 min using velocity gradients of 520 s−1, 640 s−1, 720 s−1 and 960 s−1 produced under flow rates of 3 L min−1, 5 L min−1 and 7 L min−1 and 10 L min−1 respectively. The photo-oxidation kinetics of faecal coliform contained in settled and raw sewage samples were also studied under two dark control tests (static and dynamic tests) and a light test. The system achieved a 2.0–2.34 log reduction of faecal coliforms and dissolved oxygen was within the range of 1.9 mg L−1 - 3.0 mg L−1. In the dynamic control test, the inactivation rate constant of bacteria indicated a reduction of 1.11 log (92%) for settled sewage and 1.0 log (90%) for raw sewage. The coliform inactivation rate constant, due to the combined effect of turbulent mixing speed and dark inactivation rate constant, was 2.3 h−1, and the solar irradiance inactivation rate constant was 2.4 h−1. These results have demonstrated that induced aeration is an economically friendly approach to enhance wastewater treatment in developing nations with long sunshine hours.

Effects of subgrid‐scale turbulence parametrization on the representation of clear‐air turbulence using kilometre‐ to hectometre‐scale numerical simulations

A turbulence event arising in a jet exit region above the Belgium–Luxembourg area, determined from airliner in‐situ measurements, is reproduced using the meteorological models Application de la Recherche à l'Opérationnel à Méso‐Echelle (AROME) and Meso‐NH at horizontal resolutions of 1.3 km and 260 m. The behaviour of the subgrid turbulence scheme at 1.3 km and its sensitivity to various parameters are analysed, with results being evaluated using measurements. An increase of the vertical resolution around the tropopause levels with m is shown to greatly enhance the turbulence representation. The use of a non‐local formulation of the mixing length in the current parametrization at 1.3 km allows reproduction of a turbulence signal in agreement with the observations. On the contrary, the use of a fully three‐dimensional formulation has no impact on the simulation at this resolution (1.3 km). Using the 260 m runs, this turbulence event is linked to hydrodynamical wind shear instabilities characterized by horizontal wavelength of 4.5 km, sub‐resolved at the operational resolution. At these small grid‐size scales, turbulence evolution and equation budgets reflect an equilibrium between dynamical production and turbulence dissipation, and highlight the importance of horizontal gradients. Subgrid turbulence intensities are assessed to be underestimated by the current parametrization at 1.3 km when compared with this high‐resolution reference simulation. Finally, different tests on the turbulence parametrization illustrate a transfer between resolved and subgrid kinetic energy in the model. This transfer stresses the importance of a trade‐off between mixing intensity and the representation of wind at resolved scales for the upper troposphere.

A young Female of Cowden Syndrome Presenting with Lhermitte- Duclos Disease: A Case Study

Cowden Syndrome (CS) is a rare autosomal dominant inherited genetic disorder due to germline mutations in the phosphatase and tensing homologue (PTEN) tumor suppressor gene in chromosome 10 characterized by multiple hamartomata’s lesions of ectodermal, mesodermal and endodermal origin. Lhermitte-Duclos Disease (LDD), or dysplastic gangliocytoma, which is a benign hamartomata’s condition involving the cerebellum with less than 300 cases reported in the literature. Previous studies suggest an association between CS and LDD. We present here a case of a 28-year female patient presented at the emergency department of our hospital with severe headache associated with vertigo, vomiting & cerebellar ataxia. Papilledema was noted on fundoscopy. Non-attenuating hypodense mass lesion in posterior fossa was found in CT scan. MRI scan T1WI film revealed mixed intensity posterior fossa lesion and T2WI film revealed inhomogeneous hyperintense lesion with almost preserved cerebellar cortical striations. USG revealed numerous polyps in the gallbladder with cholelithiasis. Her facial skin has extensive trichilemmoma. Her symptoms improved after excision of posterior fossa lesion through suboccipital craniectomy and histopathology revealed dysplastic cerebellar gangliocytoma i.e., Lhermitte-Duclos disease. Using the Cleveland Clinic Adult Clinical Scoring for PTEN Testing, the patient had an 82-98% chance for a PTEN gene mutation. Finally, she along with her family was adequately counseled and was advised for regular screening and monitoring. Bang. J Neurosurgery 2022; 12(1): 41-46

Numerical Analysis of Fracture Behavior of Functionally Graded Materials using 3D-XFEM

Abstract This paper presents the numerical evaluation of mixed stress intensity factors (SIFs) and non-singular terms of William's series (T-stress) of functionally graded materials (FGMs) using three-dimensional extended finite element method (3D-XFEM). Four-point bending specimen with crack perpendicular to material gradation have been used in this investigation in order to study the effect of some parameters (crack position, crack size, specimen thickness) on the failure of FGMs materials. The fracture parameters (KI KII, phase angle ψ and T-stress) obtained by the present simulation are compared with available experimental and numerical results. An excellent correlation was found of the 3D-XFEM simulations with those available in the literature. From the numerical results, a fitting procedure is performed in order to propose an analytical formulation and subsequently are validated against the 3D-XFEM results.

Diapycnal Mixing and Double Diffusion over the Continental Slope in the Northern Sea of Japan in the Warm Half-Year

This study investigates double diffusion processes responsible for diapycnal mixing in the Primorye current in the northern Sea of Japan. The results of processing and analysis of a long time series of data from regular Aqualog-profiler measurements of thermohaline characteristics and current velocity over the continental slope between the horizons of 60 and 420 m from April to October 2015. Using the Osborne-Cox parameterization (1972) and Gregg’s (1989) parameterization, we estimated heat and salt diffusivities, as well as the buoyancy flux. To reveal the processes of double diffusion, the Turner angle was estimated. We estimated contributions of diffusive convection and salt fingers into the buoyancy flux. Due to double diffusion, the intense vertical mixing covered the layer from 80 to 170 m. From mid-spring to early May, diffusive convection penetrated to a horizon of 250 m, and then a process like salt fingers played a leading role. Shear instability caused by the weakly nonlinear interaction of internal waves prevailed in the underlying layers.

Land-use pattern and landscape structure impact butterfly diversity and abundance in organic agroecosystems

ContextAgricultural intensification and land-use patterns impact biodiversity and reduce ecosystem functions. Organic farming is often seen as a more biodiversity friendly way of farming. However, not all organic farming is equally supportive for biodiversity, structural diversity of the farms has a great impact and the often high intertwinement of organic and conventional farmland causes spill-over problems.ObjectiveOn organic farmland in central Italy, we analysed butterfly diversity and community structures in different land-use categories across a heterogeneous landscape. We aim to analyse the impact of the different land-use structures such as hedges and forest edges on this farmland, as well as the influence of adjoining conventionally farmed areas.MethodsWe studied butterflies on organic farmland including olive and hazelnut plantations, as well as meadows and fallow land, surrounded by hedges and forests. Hereby we considered the effects of land-use on the studied site and the adjoining land, e.g., semi-natural habitats (as hedges or forest edges), organic or conventional farmland. We counted butterflies along line transects and recorded habitat parameters for each transect. All encountered butterflies were classified according their ecological demands, behaviour, and life-history.ResultsWe found highest mean butterfly species richness in fallow land and lowest in hazelnut plantations. Species community structures differed hardly between plantations and meadows, but considerably compared to fallow land. Butterfly abundances are reduced for olive plantations adjacent to agricultural fields treated with pesticides, compared to such surrounded by organic fields. Habitat para-meters such as the number of flowering plant species and shade impact butterfly diversity and abundance. Forest edges producing considerable shadow to the transects had a significantly negative effect on diversity and abundance, while the influence of hedges was positive.ConclusionsBased on our findings, we conclude that also organic farmland has different degrees of biodiversity depending on a variety of land-use pattern. In particular, habitat heterogeneity and a high diversity of flowers positively influence butterfly diversity. The intensive mixing of organic and conventional agriculture must be seen critical for conservation as negative effects might spill over to organic fields, but might be compensable by landscape structures like hedges.

Impact of vertical stratification on the 2020 spring bloom in the Yellow Sea

The Yellow Sea is one of the world’s most abundant marine resources, providing food and economic benefits to the Korean and Chinese populations. In spring 2020, a decrease in the intensity of phytoplankton bloom was observed. While one study attributed this decline to a decrease in nutrient associated with the COVID-19 pandemic, our previous research proposed weakened thermal stratification accompanied by a surface cooling anomaly as the cause. However, the relationship between the marine environment and ecosystem has not been fully elucidated. Using observations and marine physical-biogeochemical model data, we identified the weakened stratification as a critical factor for suppressing the 2020 spring bloom. Intense vertical mixing hindered the accumulation of nutrient and chlorophyll-a concentrations within the euphotic zone, resulting in a diminished phytoplankton bloom. In contrast, reduced nitrate and phosphate concentrations in 2020 were insignificant compared to those in 2017–2019, despite the notable decline in PM2.5 in March 2020 due to COVID-19. In April 2020, nutrient levels fell within the range of interannual variability based on long-term observations, reflecting a negligible effect on the spring phytoplankton bloom. Our findings provide insight into the importance of marine physical factors on the phytoplankton biomass in the Yellow Sea.