Colloid Concentration Research Articles

Characterization of a novel chitinolytic Serratia marcescens strain TC-1 with broad insecticidal spectrum

The Gram-negative rod-shaped bacterium Serratia marcescens is an opportunistic pathogen of many organisms, including insects. We report the identification and optimal in vitro chitinase production conditions of a novel chitinolytic S. marcescens strain TC-1 isolated from a naturally infected white grub (Anomala corpulenta) collected from a peanut field at Nanyang city, Henan province, China. Strain identification was conducted by morphological, physiological, biochemical and molecular analyses. The amplified 16S rRNA gene of TC-1 showed a similarity greater than 99% with multiple strains of S. marcescens. Based on Neighbor-joining phylogenetic tree analysis of bacterial 16S rRNA gene sequences, TC-1 formed a clade with S. marcescens, clearly separated from other Serratia spp. The strain TC-1 showed larvicidal activities against five insect species (A. corpulenta, Plutella xylostella, Spodoptera exigua, Helicoverpa armigera, Bombyx mori) and the nematode Caenorhabditis elegans, but not against S. litura. The operating parameters of chitinase production by TC-1 were optimized by response surface methodology using a three-factor, three-level Box-Behnken experimental design. The effects of three independent variables i.e. colloidal chitin concentration (7–13 g l−1), incubation time (24–72 h) and incubation temperature (24–32 °C) on chitinase production by TC-1 were investigated. A regression model was proposed to correlate the independent variables for an optimal chitinase activity predicted as 20.946 U ml−1, using a combination of colloidal chitin concentration, incubation time and incubation temperature of 9.06 g l−1, 63.83 h and 28.12 °C, respectively. The latter agreed well with a mean chitinase activity of 20.761 ± 0.102 U ml−1 measured in the culture supernatants of TC-1 grown under similar conditions with a colloidal chitin concentration, incubation time and incubation temperature of 9 g l−1, 64 h and 28 °C, respectively. Our study revealed the S. marcescens strain TC-1 with potential as a biocontrol agent of insect pests and nematodes and demonstrated the proposed regression model's potential to guide chitinase production by this strain.

Morphological and structural characterization of chitin as a substrate for the screening, production, and molecular characterization of chitinase by Bacillus velezensis.

The processing of shellfishery industrial wastes is gaining much interest in recent times due to the presence of valuable components. Chitin is one of the valuable components and is insoluble in most common solvents including water. In this study, a novel gram-positive bacterial strain capable of solubilizing chitin was screened from a prawn shell dumping yard. The chitinolytic activity of the isolated strain was observed through the zone of hydrolysis plate assay. The hyper-producing isolate was identified as Bacillus velezensis through the 16S rRNA sequencing technique. The structural and morphological characterization of raw and colloidal chitin preparation was carried out using FTIR, XRD, and SEM analysis. The residual protein and mineral content, degree of polymerization, and degree of acetylation were reported for both raw and colloidal chitin preparations. There was a linear increase in the chitinase activity with an increase in the colloidal chitin concentration. The maximum activity of chitinase was observed as 38.98 U/mL for the initial colloidal chitin concentration of 1.5%. Supplement of additional carbon sources, viz., glucose and maltose, did not improve the production of chitinase and resulted in a diauxic growth pattern. The maximum chitinase activity was observed to be 33.10 and 30.28 U/mL in the colloidal chitin-containing medium with and without glucose as a secondary carbon source, respectively. Interestingly, the addition of complex nitrogen sources has increased the production of chitinase. A 1.95- and 2.14-fold increase in the enzyme activity was observed with peptone and yeast extract, respectively. The chitinase was confirmed using SDS-PAGE, native PAGE, and zymograms. The optimum pH and temperature for chitinase enzyme activity were found to be 7.0 and 44°C, respectively.

Alkaline aging significantly affects Mn(II) adsorption capacity of polypropylene microplastics in water environments: Critical roles of natural organic matter and colloidal particles

Most microplastic particles may undergo various aging in water environments. In this work, surface physicochemical properties were firstly compared among pristine polypropylene (PP-pris) microplastics, and two aged ones obtained after pretreated with HCl (PP-acid) and NaOH (PP-alka). When compared with PP-pris and PP-acid, PP-alka had a much stronger Mn(II) adsorption capacity. The results regarding the role of natural organic matter and colloidal particle concentrations on adsorption demonstrated that for water solutions either containing kaolin or not, humic acid (HA) had significantly negative influence on Mn(II) adsorption capacity of PP-alka due to their complexation and competition effects, and its negative influence became enhanced with increasing kaolin concentrations. Besides, established conceptual models of adsorption were applied to comprehensively explore adsorption mechanisms of PP-alka for Mn(II) in the coexistence of HA and kaolin. An important suggestion was that in complicated adsorption-reactor system, great numbers of microplastics-kaolin heteroaggregates might be formed via ion bridging of Mn(II) and/or polymer bridging of HA. So these formed aggregates were possible to re-organize themselves, under pre-set vibration-speed conditions, for achieving a more stable structure. As a consequence, Mn(II) adsorption behaviors would be affected by changes in steric-hindrance effects of HA molecules and surface charge distribution of resultant heteroaggregates.

Effect of concentration of silica encapsulated ds-DNA colloidal microparticles on their transport through saturated porous media

We investigated the transport and retention kinetics of silica encapsulated – silica core double stranded DNA particles (SiDNASi) through 15 cm saturated quartz sand columns as a function of a wide range of colloid injection concentrations (C0 = 8.7 ×102 - 6.6 ×108 particles ml−1). The breakthrough curves (BTCs) exhibited an overall 2-log increase of maximum relative effluent concentration with increasing C0. Inverse curve fitting, using HYDRUS1D, demonstrated that a 1-site first order kinetic attachment (katt) and detachment (kdet) model sufficed to explain the C0-dependent SiDNASi retention behaviour. With increasing C0, katt log-linearly decreased, which could be expressed as an overall decrease in the single-collector removal efficiency (ƞ). The decrease in ƞ was likely due to increased electrostatic repulsion between aqueous phase- solid phase colloids, formation of shadow zones downstream of deposited colloids and removal of weakly attached colloids from the solid phase (quartz sand) attributing to increased aqueous phase-solid phase intercolloidal collisions as a function of increasing SiDNASi concentration. Our results implied, firstly, that the aqueous phase colloid concentration should be carefully considered in determining colloidal retention behaviour in saturated porous media. Secondly, colloidal transport and retention dynamics in column studies should not be compared without considering colloid influent concentration. Thirdly, our results implied that the applicability of SiDNASi as a conservative subsurface tracer was restricted, since transport distance and retention was colloid concentration dependent. However, the uniqueness of the DNA sequences in SiDNASi imparts the advantage of concurrent use of multiple SiDNASi for flow tracking or porous media characterization.

Optimization approach for the dilute magnetic polymer-dispersed liquid crystal

A method was investigated to improve the capacitance and electro-optical response of the dilute magnetic polymer-dispersed liquid crystals (PDLC). The proposed magnetic separation treatment further decreased the ion concentration of the liquid crystal colloid while preparing the diluted magnetic PDLC. The microstructure of the optimized diluted magnetic PDLC, including the shape, size, and distribution of the LC droplets, has not changed, but the capacitance and the electro-optical response of the PDLC have been further improved. Usually, increasing the concentration of the magnetic nanoparticles may reduce the ion concentration more, but the performance of PDLC has been a disadvantage. Our presented work shows an additional decrease in the ion concentration by doping the relatively high concentration of the magnetic nanoparticles and the magnetic separation treatment. However, the performance of the diluted magnetic PDLC has improved even more.

Application of temporal moment analysis to interpret colloid and colloid-facilitated solute transport under varying size exclusion and attachment coefficient.

Colloidal particles can attach the contaminants like heavy metals and radionuclides and act as contaminant carriers to provide a faster movement of pollutants through the interconnecting pores of the porous medium. The electrostatic repulsive force between the negatively charged colloids and the solid surface restricts the transport of the mobile colloids to the larger pores of the porous medium and initiates the size exclusion mechanism. The temporal moment analysis is treated as an effective tool to interpret the solute breakthrough curves for analyzing the statistical behavior of the contaminants. In past literature, the temporal moments have not been incorporated with the breakthrough curves of colloids and colloid-facilitated contaminants for statistical interpretation. In this research study, the temporal variations of concentrations of mobile colloids, solute attached to the mobile colloids, and the dissolved solute are obtained numerically in a fully saturated one-dimensional column considering a continuous source for varying size exclusion and colloid attachment coefficient. Utilizing the simulated spatially varying breakthrough curves, the temporal moments are estimated to calculate the mass recovery, average residence time, and the spreading of mobile colloids and dissolved solutes. The temporal moment analysis suggests that the velocity enhancement for higher size exclusion reduces the average residence time of the mobile colloids and the solute adsorbed to the mobile colloids significantly. The mass recovery of mobile colloids and the solute attached to the mobile colloids increases at a specific depth for higher size exclusion. The estimated second central moment attributes that the solute spreading follows the nonlinear trend for low size exclusion. The peaks of the relative concentration of mobile colloids and solute attached to mobile colloids drastically decrease with an increase in attachment coefficient. The peak of the relative concentration of dissolved contaminant enhances with attachment coefficient. The high second temporal moment of the dissolved contaminant at a higher attachment coefficient indicates the slow interaction of dissolved solute and porous medium and that enables a greater spreading of solute through the interconnecting porous medium. The study suggests that the faster movement of mobile colloids and the solute attached to the mobile colloids at higher exclusion imparts a potential risk of groundwater contamination and thorough statistical interpretation is needful to analyze the behavior of colloids and colloid-facilitated contaminants. The research work does not consider the transient flow field and the effect of the presence of air phase in the partially saturated soil column in the groundwater system.

A Moir\xe9 interference pattern formation of magnetic nanoparticles by rotational magnetic field controlled interfacial self-assembly

‘Magic-angled’ structure currently attracts increasing attention from condensed matter physics due to its amazing performance in superconductivity of graphene. The similar pattern formation of nanoparticles will bring about novel physics in nanoscale that causes the next generation nanodevices. However, it remains a challenging task to acquire such patterns by self-assembly process. In this article, we reported a Moiré interference pattern formation of magnetic nanoparticles regulated by a rotational magnetic field. The colloidal concentration, the strength, and the frequency of magnetic field were found to affect the pattern formation. The mechanism lied in a two-step process. First, the magnetic nanoparticles formed bilayers of superlattice driven by hydrophobic interaction of interfacial self-assembly. Then, the bilayers of superlattice yielded asynchronous rotational displacement resulting from the magnetic force so that the Moiré interference pattern of nanoparticles formed. This fabrication methodology based on the field-controlled self-assembly provided a novel and simple means to get ‘magic angled’ structures in nanoscale that will enrich the physical understanding of nanotechnology.

Effects of low molecular weight organic acids on aggregation behavior of biochar colloids at acid and neutral conditions

Low molecular weight organic acids (LMWOAs), as active components in the rhizosphere carbon cycling, may influence the environmental behaviors of biochar colloids. This study selected the pine-wood and wheat-straw biochars (PB and WB) as two typical biochars. The effects of typical LMWOAs (oxalic acid, citric acid, and malic acid) on aggregation kinetics of PB and WB colloids were investigated under pH 4 and 6 conditions. Critical coagulation concentrations (CCCs) of both PB and WB colloids were decreased with the LMWOAs regardless of the types of biochar and the solution pH, and the most significant effect occurred in pH 4 due to more LMWOAs sorption on the biochar colloids. The different types of LMWOAs caused various CCCs changes. For example, the CCC values of PB colloids decreased from 75 mM to 56, 52, and 47 mM in the pH 4 NaCl solutions when 1 mM oxalic acid, citric acid, and malic acid were present in the suspensions, respectively. The chemical structure (functional groups) and molecular weight of LMWOAs, solution pH, and the electrophoretic mobility (EPM) of biochar co-influence the interactions between biochar colloids and LMWOAs, thus affecting the stability of biochar colloids in the presence of LMWOAs. The presence of LMWOAs accelerated the aggregation of colloidal biochar by increasing the interaction of surface bridging bonds (hydrogen bonding) and decreasing the repulsive force between colloidal biochar particles. This study showed that LMWOAs could accelerate the aggregation of biochar colloids in acidic or neutral environments and reduce the mobility of biochar colloids in soil rhizosphere.

Online colloidal particle monitoring for controlled coagulation pretreatment to lower microfiltration membrane fouling at a potable water reuse facility

Fouling of microfiltration (MF)) membranes during water/wastewater treatment is predominantly caused by colloidal particles (size <1 µm) in the feed water. Until recently no online technology was available to directly measure the occurrence of colloidal particles in these waters. This study evaluated the viability of a novel online light scattering technology (Nanoparticle Tracking Analysis) to continuously monitor colloidal particles in the membrane feed water (a secondary-treated wastewater) for targeted removal by injecting coagulant at a dosage proportional to the measured concentration of colloidal particles. A diurnal variation was observed in the colloidal particle concentration in the feed water with the lowest concentration occurring at approximately 6 am and the highest concentration occurring after mid-day. The peak colloidal particle concentrations were 4 to 6 times higher than the lowest concentrations measured on the same day. Bench-scale studies were performed to develop a relationship between colloidal particle concentration and the optimum coagulant dosage required for their removal. Subsequently, a pilot-scale study was performed using two MF pilot units operated in parallel, one receiving targeted coagulant dosing and the other with no coagulant dosing, to demonstrate the effectiveness of targeted coagulant dosing in preventing membrane fouling. The pilot unit that received targeted coagulant dose experienced only 4 to 20% of the transmembrane pressure increase of the increase experienced by the pilot unit that received no coagulant. Evaluation of fouling resistance indicated that targeted coagulation improved flux by predominantly lowering the irreversible fouling. The filtrate water quality measured by colloidal particle concentration, chemical oxygen demand (COD), and turbidity were very similar for the two pilot units. This suggests that although the efficiency of particle and organic materials removal does not change with coagulant addition, the particles filtered by the membrane in the control unit contributed to membrane irreversible fouling, while in the coagulant-treated unit, the coagulated colloidal particles were removed away from the membrane into the backwash stream during the frequent backwash/air scour procedures.

Quantification of protein by acid hydrolysis reveals higher than expected concentrations in red wines: Implications for wine tannin concentration and colloidal stability

Protein is reportedly negligible in most red wines, due to its loss following co-precipitation with phenolic substances. A method for protein quantification in red wine was developed which overcame analytical interference from phenolic substances, based on ethanol precipitation, followed by acid-hydrolysis and amino acid quantification. Protein concentration was surveyed in a range of red wines produced from V. vinifera and interspecific (Vitis spp) hybrids, revealing higher than expected concentrations, ranging from 23 mg/L ± 2.57 to 380 mg/L ± 16. The results showed that tannin extracted from grapes remains soluble in wine in the presence of protein even at high protein (>100 mg/L) and tannin (>500 mg/L) concentrations. As a further consequence of this, the particle size and concentration of colloids within high- and low-protein wines were similar, independent of protein or tannin concentration. Higher wine tannin concentration was also correlated with increased heat stability of wine protein.

Sedimentation of colloidal plate-sphere mixtures and inference of particle characteristics from stacking sequences

We investigate theoretically the effect of gravity on a plate-sphere colloidal mixture by means of an Onsager-like density functional to describe the bulk, and sedimentation path theory to incorporate gravity. We calculate the stacking diagram of the mixture for two sets of buoyant masses and different values of the sample height. Several stacking sequences appear due to the intricate interplay between gravity, the sample height, and bulk phase separation. These include the experimentally observed floating nematic sequence, which consists of a nematic layer sandwiched between two isotropic layers. The values of the thicknesses of the layers in a complex stacking sequence can be used to obtain microscopic information of the mixture. Using the thicknesses of the layers in the floating nematic sequence we are able to infer the values of the buoyant masses from the colloidal concentrations and vice versa. We also predict new phenomena that can be experimentally tested, such as a nontrivial evolution of the stacking sequence by increasing the sample height in which new layers appear either at the top or at the bottom of the sample.

Co-transport of bentonite colloid and U(VI) in particulate granite column: role of colloid concentration, ionic strength, pH and flow rate

Abstract China is considering Beishan granitic formation (Gansu Province, China) as the site for high-level radioactive waste (HLW) repositories. Thus, it is crucial to understand the transport behavior of radionuclide in Beishan granitic media under disposal conditions. In this context, the co-transport of U(VI) (as the representative of radionuclides) and bentonite colloid (BC, from erosion of compacted bentonite) in particulate Beishan granite was studied as a function of important in-situ factors, such as BC concentration, ionic strength, pH and flow rate. We found that the increase of BC concentration (BC = 240–480 mg/L) did not affect the transport of individual BC, whereas it significantly facilitated the transport of U(VI). The increase of ionic strength (I = 0.001–0.01 M NaCl) or decrease of pH (pH = 7.50–5.40) obviously inhibited the BC transport, where these inhibiting effects were relatively slight for the transport of U(VI). The increase of flow rate significantly facilitated both the transport of BC and U(VI). Finally, a two-site kinetic attachment/detachment model was applied to describe the breakthrough curves of individual and co-transport of BC. The experimental and modeling results of this study have a significant implication on the safety assessment of HLW repositories built in granitic formation.

Liquid limit of marine soft clay encountering desalination percolation process

The diffuse double layer (DDL) theory indicated that the liquid limit (LL) of clays decreases based on pore-water salinity during salinization tests conducted in a laboratory. However, LL also decreased based on pore-water salinity when authors conducted geological investigations in the regression depositional zone in Lianyungang city, contradicting the DDL theory. This contradictory finding is inferred due to the coupled effect of salinity leaching and erosion of the colloid during a desalination percolation process. To confirm this hypothesis, 3 model tests of distilled water percolation and seven accelerated percolation tests were designed in this study, and the soil/water characteristics after desalination percolation were determined. The results reveal that the pore-water salinity leaches are combined with the colloidal erosion during the desalination percolation process, leading to the gradual decrease in LL based on the reduction of salinity and suggesting that the dominant effect is the colloidal erosion. At the initial stage of the desalination process, the colloids easily erode from the clay matrix due to the weakened salinity inhibition on the colloid release, leading to the seepage channel expansion, and hence the increase in colloid dimension and concentration in leachates throughout percolation. Based on the further decrease in pore-water salinity, the colloids in the clay matrix continuously release and inversely clog the inner channels of the soils, decreasing the colloid dimension and concentration in leachates. When the percolation process is sufficiently long, all salinity would be leached out from the clay matrix, and only the erosion of the colloid would be identified.

Mobility of polypropylene microplastics in stormwater biofilters under freeze-thaw cycles

Stormwater biofilters naturally experience dry-wet and freeze-thaw cycles, which could remobilize deposited particulate pollutants including microplastics. Yet, the effect of these natural weathering conditions on the mobility of deposited microplastics has not been evaluated. We deposited microplastics on columns packed with sand or a mixture of sand with soil (25% by volume) to simulate biofilter media, subjected them to intermittent infiltration events punctuated by either freeze-thaw cycles or drying cycles. Comparing the vertical distribution of microplastics in biofilters after both treatments, we showed that more than 90% of microplastics were retained within the first 3 cm of filter media, but the distribution in deeper layers varied with media type and treatment conditions. Freeze-thaw cycles were more effective than dry-wet cycles in increasing the downward mobility of deposited microplastics. We attributed these results to the disruption of filter media by expanding ice crystals, which could release deposited colloids and associated microplastics. An increase in natural colloid concentration in the effluent following freeze-thaw treatments confirmed the hypothesis. The results are useful in predicting microplastic transport in the root zone in stormwater biofilters or contaminated land experiencing natural freeze-thaw cycles.

Co-transport and co-release of Eu(III) with bentonite colloids in saturated porous sand columns: Controlling factors and governing mechanisms

Accurate prediction of the colloid-driven transport of radionuclides in porous media is critical for the long-term safety assessment of radioactive waste disposal repository. However, the co-transport and corelease process of radionuclides with colloids have not been well documented, the intrinsic mechanisms for colloids-driven retention/transport of radionuclides are still pending for further discussion. Thus the controlling factors and governing mechanisms of co-transport and co-release behavior of Eu(III) with bentonite colloids (BC) were discussed and quantified by combining laboratory-scale column experiments, colloid filtration theory and advection dispersion equation model. The results showed that the role of colloids in facilitating or retarding the Eu(III) transport in porous media varied with cations concentration, pH, and humic acid (HA). The transport of Eu(III) was facilitated by the dispersed colloids under the low ionic strength and high pH conditions, while was impeded by the aggregated colloids cluster. The enhancement of Eu(III) transport was not monotonically risen with the increase of colloids concentration, the most optimized colloids concentration in facilitating Eu(III) transport was approximately 150 mg L−1. HA showed significant promotion on both Eu(III) and colloid transport because of not only its strong Eu(III) complexion ability but also the increased dispersion of HA-coated colloid particles. The HA and BC displayed a synergistic effect on Eu(III) transport, the co-transport occurred by forming the ternary BC-HA-Eu(III) hybrid. The transport patterns could be simulated well with a two-site model that used the advection dispersion equation by reflecting the blocking effect. The retarded Eu(III) on the stationary phase was released and remobilized by the introduction of colloids, or by a transient reduction in cation concentration. The findings are essential for predicting the geological fate and the migration risk of radionuclides in the repository environment.

Light scattering of colloidal suspensions: formation and stability in bourbon whiskeys

The dilution of whiskey with water can lead to the formation of unwanted haze which is exacerbated at lower temperatures. This phenomenon is well known in the whiskey industry, and it is normal practice to use cold filtration to produce a clear product as well as improve product stability. However, to date, there has been no quantitative characterisation or understanding of the size and concentration of the colloidal particles as a function of whiskey dilution, temperature, and maturation. This report utilises light scattering techniques to characterise the formation of colloids in bourbon whiskeys of different aging periods. Higher water dilution decreased the size of the colloidal particulates and increased their stability. Aged samples (> 36 months) were found to be more stable, having a higher concentration of colloids at lower dilutions. This work demonstrates that dynamic light scattering can be useful for quality control in the spirits industry. © 2022 The Institute of Brewing & Distilling.

Suppression of self-stratification in colloidal mixtures with high Péclet numbers.

The non-equilibrium assembly of bimodal colloids during evaporative processes is an attractive means to achieve gradient or stratified layers in thick films. Here, we show that the stratification of small colloids on top of large is prevented when the viscosity of the continuous aqueous phase is too high. We propose a model where a too narrow width of the gradient in concentration of small colloids suppresses the stratification.

Mechanochemistry Advances High-Performance Perovskite Solar Cells.

A prerequisite for commercializing perovskite photovoltaics is to develop a swift and eco-friendly synthesis route, which guarantees the mass production of halide perovskites in the industry. Herein, a green-solvent-assisted mechanochemical strategy is developed for fast synthesizing a stoichiometric δ-phase formamidinium lead iodide (δ-FAPbI3 ) powder, which serves as a high-purity precursor for perovskite film deposition with low defects. The presynthesized δ-FAPbI3 precursor possesses high concentration of micrometer-sized colloids, which are in favor of preferable crystallization by spontaneous nucleation. The resultant perovskite films own preferred crystal orientations of cubic (100) plane, which is beneficial for superior carrier transport compared to that of the films with isotropic crystal orientations using "mixture of PbI2 and FAI" as precursors. As a result, high-performance perovskite solar cells with a maximum power conversion efficiency of 24.2% are obtained. Moreover, the δ-FAPbI3 powder shows superior storage stability for more than 10 months in ambient environment (40± 10% relative humidity), being conducive to a facile and practical storage for further commercialization.

Effect of the colloidal graphite filler on the properties of electroconductive polyethylene compositions

The effect of colloidal graphite in a polyethylene (PE) matrix on electrical, mechanical, rheological and optical properties of electroconductive compositions has been investigated. PE compositions filled with different amounts of colloidal graphite were prepared, and the effects of fillers on their properties were studied. Electrical volume resistivity dramatically decrees with the increase in the volume content of the electroconductive filler in the PE matrix and can be described by exponential law. The decrease in tensile strength by ∼ 1.2 times and relative elongation by ∼ 5.1 times have been observed. The melt flow index slightly increases with the increase of colloidal graphite concentration in the PE composition by ∼ 1.1 times due to the lubricating effect. Optical microscopic studies have proved that the colloidal graphite exerted not only a direct but also an indirect influence on the electrical volume resistivity and on the mechanical properties of the PE compositions. At lower colloidal graphite contents, the material became more flexible because of the better dispersion of graphite, but at higher colloidal graphite contents the stiffness significantly increased.

A critical review on the occurrence and distribution of the uranium- and thorium-decay nuclides and their effect on the quality of groundwater

This critical review presents the key factors that control the occurrence of natural elements from the uranium- and thorium-decay series, also known as naturally occurring radioactive materials (NORM), including uranium, radium, radon, lead, polonium, and their isotopes in groundwater resources. Given their toxicity and radiation, elevated levels of these nuclides in drinking water pose human health risks, and therefore understanding the occurrence, sources, and factors that control the mobilization of these nuclides from aquifer rocks is critical for better groundwater management and human health protection. The concentrations of these nuclides in groundwater are a function of the groundwater residence time relative to the decay rates of the nuclides, as well as the net balance between nuclides mobilization (dissolution, desorption, recoil) and retention (adsorption, precipitation). This paper explores the factors that control this balance, including the relationships between the elemental chemistry (e.g., solubility and speciation), lithological and hydrogeological factors, groundwater geochemistry (e.g., redox state, pH, ionic strength, ion-pairs availability), and their combined effects and interactions. The various chemical properties of each of the nuclides results in different likelihoods for co-occurrence. For example, the primordial 238U, 222Rn, and, in cases of high colloid concentrations also 210Po, are all more likely to be found in oxic groundwater. In contrast, in reducing aquifers, Ra nuclides, 210Pb, and in absence of high colloid concentrations, 210Po, are more mobile and frequently occur in groundwater. In highly permeable sandstone aquifers that lack sufficient adsorption sites, Ra is often enriched, even in low salinity and oxic groundwater. This paper also highlights the isotope distributions, including those of relatively long-lived nuclides (238U/235U) with abundances that depend on geochemical conditions (e.g., fractionation induced from redox processes), as well as shorter-lived nuclides (234U/238U, 228Ra/226Ra, 224Ra/228Ra, 210Pb/222Rn, 210Po/210Pb) that are strongly influenced by physical (recoil), lithological, and geochemical factors. Special attention is paid in evaluating the ability to use these isotope variations to elucidate the sources of these nuclides in groundwater, mechanisms of their mobilization from the rock matrix (e.g., recoil, ion-exchange), and retention into secondary mineral phases and ion-exchange sites.