Colloids In Natural Waters Research Articles

Quantification of ZnO nanoparticles and other Zn containing colloids in natural waters using a high sensitivity single particle ICP-MS

Inductively coupled plasma mass spectrometry in single particle mode (SP-ICP-MS) is becoming a powerful tool of choice for the quantification and characterization of metallic nanoparticles (NP) at very low concentrations. Nonetheless, this technique has relatively high size detection limits for highly soluble nanoparticles (e.g. ZnO, CuO) or NP that are measured in the presence of high background concentrations of dissolved metal. In order to evaluate whether SP-ICP-MS could be used to measure a soluble NP under environmentally relevant conditions, an ion-exchange column (IEC) was coupled to a highly-sensitive sector-field ICP-MS (IEC-SP-ICP-MS) and then used to detect both spiked ZnO NP and natural Zn containing colloids in natural waters. The use of an ion exchange column, short dwell times (50 µs) and a high sensitivity instrument gave size detection limits for the measurement of ZnO NP of ca. 8.2 nm in pure water, 14.3 nm in a river water and 17.7 nm in a rainwater. IEC-SP-ICP-MS measured ca. 4.4 × 105 mL−1 zinc containing particles in a river water sample and ca. 1.0 × 105 mL−1 particles in a local rainwater.

Technology of drinking water preparation using the reactor - clarifier

Siberian surface water and groundwater are characterized by low temperatures for a long year period. Many groundwater sources’ organic composition are formed of soil and peat humus, marsh feeding of rivers, decomposition of plankton, higher water, and soil grass in reservoirs and lakes. Organic colloids in natural waters and in humic substances give the color of water. It’s yellowish coloration of varying intensity. Thus, the Om River’s water color in the city of Kuibyshev in the Novosibirsk Region is 500 degrees with feculence of less than 3 mg/l. A number of underground water sources also have an increased content of organic contaminants caused by peat bogs at great depths and high water colority with low turbidity. For example, the water color is up to 1500 degrees in the Namtsy village of the SAHA-Yakutia Republic. In addition, underground water and, to a greater extent, surface water are often characterized by a high content of iron (up to 20 mg/l), manganese (up to 4 mg/l), and other impurities of natural and anthropogenic origin. Iron and manganese are in natural waters in the form of mineral or organic complex compounds of humic or some fatty acids. In the second case, these waters are with increased oxidizability and rather aggressive nature. In particular, the iron content is 3 mg/l, manganese is 1 mg/l, the permanganate oxidizability is 50 mg/l in the water of the Om River.

原子間力顕微鏡と透過型電子顕微鏡を用いた天然水中のコロイド分析 –山形・新潟県境金丸地区の例–

原子間力顕微鏡と透過型電子顕微鏡を用いた天然水中のコロイド分析 –山形・新潟県境金丸地区の例–

Iron-rich colloids as carriers of phosphorus in streams: A field-flow fractionation study

Colloidal phosphorus (P) may represent an important fraction of the P in natural waters, but these colloids remain poorly characterized. In this work, we demonstrate the applicability of asymmetric flow field-flow fractionation (AF4) coupled to high resolution ICP-MS for the characterization of low concentrations of P-bearing colloids. Colloids from five streams draining catchments with contrasting properties were characterized by AF4-ICP-MS and by membrane filtration. All streams contain free humic substances (2–3 nm) and Fe-bearing colloids (3–1200 nm). Two soft water streams contain primary Fe oxyhydroxide-humic nanoparticles (3–6 nm) and aggregates thereof (up to 150 nm). In contrast, three harder water streams contain larger aggregates (40–1200 nm) which consist of diverse associations between Fe oxyhydroxides, humic substances, clay minerals, and possibly ferric phosphate minerals. Despite the diversity of colloids encountered in these contrasting streams, P is in most of the samples predominantly associated with Fe-bearing colloids (mostly Fe oxyhydroxides) at molar P:Fe ratios between 0.02 and 1.5. The molar P:Fe ratio of the waters explains the partitioning of P between colloids and truly dissolved species. Waters with a high P:Fe ratio predominantly contain truly dissolved species because the Fe-rich colloids are saturated with P, whereas waters with a low P:Fe ratio mostly contain colloidal P species. Overall, AF4-ICP-MS is a suitable technique to characterize the diverse P-binding colloids in natural waters. Such colloids may increase the mobility or decrease the bioavailability of P, and they therefore need to be considered when addressing the transport and environmental effects of P in catchments.

Size-fractionation of groundwater arsenic in alluvial aquifers of West Bengal, India: The role of organic and inorganic colloids

Dissolved organic carbon (DOC) and Fe mineral phases are known to influence the mobility of arsenic (As) in groundwater. Arsenic can be associated with colloidal particles containing organic matter and Fe. Currently, no data is available on the dissolved phase/colloidal association of As in groundwater of alluvial aquifers in West Bengal, India. This study investigated the fractional distribution of As (and other metals/metalloids) among the particulate, colloidal and dissolved phases in groundwater to decipher controlling behavior of organic and inorganic colloids on As mobility. The result shows that 83–94% of As remained in the ‘truly dissolved’ phases (i.e., <0.05μm size). Strong positive correlation between Fe and As (r2 between 0.65 and 0.94) is mainly observed in the larger (i.e., >0.05μm size) colloidal particles, which indicates the close association of As with larger Fe-rich inorganic colloids. In smaller (i.e., <0.05μm size) colloidal particles strong positive correlation is observed between As and DOC (r2=0.85), which highlights the close association of As with smaller organic colloids. As(III) is mainly associated with larger inorganic colloids, whereas, As(V) is associated with smaller organic/organometallic colloids. Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy confirm the association of As with DOC and Fe mineral phases suggesting the formation of dissolved organo-Fe complexes and colloidal organo-Fe oxide phases. Attenuated total reflectance-Fourier transform infrared spectroscopy further confirms the formation of As–Fe–NOM organometallic colloids, however, a detailed study of these types of colloids in natural waters is necessary to underpin their controlling behavior.

A Non-Perturbing Scheme for the Mineralogical Characterization and Quantification of Inorganic Colloids in Natural Waters

Although the role played by inorganic colloids in natural waters depends on their composition as well as on their size, the characterization of submicron particles has rarely gone beyond describing the morphology and identifying some of the most abundant particles. The process of quantification has been hampered by a lack of suitable analytical methods. This study demonstrates that it is possible to identify and quantify inorganic particles in the colloidal size range by applying a straightforward methodology based on a well-proved, quantitative, and nonperturbing method of sample preparation (direct centrifugation of the samples on transmission electron microscopy grids) in conjunction with particle analysis using widely available techniques: transmission electron microscopy, energy dispersive X-ray spectroscopy (EDS), and selected area electron diffraction (SAED). The method has successfully been applied to six water samples from basins of contrasting geological characteristics. The method has the advantage of minimizing sample modifications by allowing on site sample preparation, using standard equipment, and it is not particularly time-consuming. Notably, the combination of EDS and SAED information makes it possible to characterize and quantify the most abundant components of the colloidal pool in the majority of the aquatic systems: the different types of aluminosilicates.

Flocculation morphology: effect of particulate shape and coagulant species on flocculation

Flocculation morphology is a new concept that investigates the morphological characteristics of colloidal particles and coagulants in water during the flocculation process, and the influence that these characteristics have on flocculation process efficiency. This paper is a summary of advances in research on this topic over several years. Morphological characteristics of colloids in natural waters and different kinds of hydrolysed coagulants are investigated, and their effect on colloid stability, flocculation kinetics and efficiency is analysed. It is confirmed that the traditional theory has some deviations in coagulation of nonspherical particles, and these deviations are revised by the flocculation morphology model. Flocculation morphology can not only promote research about flocculation theory, but also instruct the production, application and flocculation control. It can be foreseen that more progress will be made in research and application of flocculation morphology in the near future.

Influence of natural organic matter and ionic composition on the kinetics and structure of hematite colloid aggregation: implications to iron depletion in estuaries.

The stability and aggregation behavior of iron oxide colloids in natural waters play an important role in controlling the fate, transport, and bioavailability of trace metals. Time-resolved dynamic light scattering experiments were carried out in a study of the aggregation kinetics and aggregate structure of natural organic matter (NOM) coated hematite colloids and bare hematite colloids. The aggregation behavior was examined over a range of solution chemistries, by adjusting the concentration of the supporting electrolyte-NaCl, CaCl2, or simulated seawater. With the solution pH adjusted so that NOM-coated and bare hematite colloids were at the same zeta potential, we observed a significant difference in colloid stability which results from the stability imparted to the colloids by the adsorbed NOM macromolecules. This enhanced stability of NOM-coated hematite colloids was not observed with CaCl2. Aggregate form expressed as fractal dimension was determined for both NOM-coated and bare hematite aggregates in both NaCl and CaCl2. The fractal dimensions of aggregates formed in the diffusion-limited regime indicate slightly more loosely packed aggregates for bare hematite than theory predicts. For NOM-coated hematite, a small decrease in fractal dimension was observed when the solution composition changed from NaCl to CaCl2. For systems in the reaction-limited regime, the measured fractal dimensions agreed with those in the literature. Colloid aggregation was also studied in synthetic seawater, a mixed cation system to simulate estuarine mixing. Those results describe the important phenomena of iron oxide aggregation and sedimentation in estuaries. When compared to field data from the Mullica Estuary, U.S.A., it is shown that collision efficiency is a good predictor of the iron removal in this natural system.

Natural Waters and Water Technology, EuroConference on Colloids in Natural Waters

Natural Waters and Water Technology, EuroConference on Colloids in Natural Waters

Filtration artifacts caused by overloading membrane filters.

The conventional practice of using 0.45 or 0.40 microm membranes to distinguish between the particulate and dissolved phases in natural waters neglects the importance of colloids. Many of the colloids in natural waters pass through 0.45 or 0.40 microm membranes, but a significant fraction at the upper end of the colloidal particle size range is retained. Membrane clogging during filtration decreases the effective pore size and can cause the retention of increasing amounts of colloids. This filtration artifact can cause serious errors in sampling and in assigning trace metals to various particle size classes. We evaluated the effect of membrane loading for two common membrane types (0.45 microm Millipore Durapore and 0.40 microm Nuclepore) on the retention of colloidal Fe, Al, Mn, and OM in three Connecticut rivers. In addition, we used a 1.0 microm Nuclepore membrane to estimate the amount of colloids in the 0.40-1.0 microm size fraction that are retained by membranes during conventional filtration. All samples were collected with clean techniques, and all filtrations were carried out in a class 100 clean room. A peristaltic pump, set at an initial flow rate of 120 mL/min, was used to pump samples through 47 mm diameter inline Teflon filter holders. Back pressure and flow rate were monitored during filtration, and both are good indicators for the onset of membrane clogging. The results show a consistent correlation between increasing back pressure and decreasing concentration of colloidal Fe and sometimes Al, Mn, and OM in the filtrate for all membrane types. Although the shape of the loading-retention curves varied dramatically by site and by membrane type, the essential relationship between back pressure, flow rate, and filtration artifacts during membrane clogging remained the same.

New Directions towards the Understanding of Physico-Chemical Processes in Aquatic Systems

Some applications of Analytical Electron Microscopies (AEM) for the characterization of colloids in natural waters are presented. These techniques go much beyond the basic level of morphological observation and render possible to gain detailed physico-chemical information difficult to obtain by conventional analytical methods. Hence, AEM appear as a challenging necessity for understanding the colloid-mediated transport of toxics in the environment.

Physicochemical and microbial preservation of colloid characteristics of natural water samples. I: Experimental conditions

Physical and chemical characterization of colloids in natural waters is a major issue to understand the mechanism of circulation of pollutants in natural waters. Although many researchers are interested in colloid interactions, they are not yet well understood, and little is known on the appropriate experimental conditions needed to perform reliable and environmentally significant analysis. The following study is dedicated to the development of well-controlled analytical conditions. It is shown that drastic degradation of the water sample can happen during sample handling, if experimental conditions are inappropriate. The study also points out that multidisciplinary cooperation is necessary in the study of environmental problems. This paper is split in two parts for editorial reasons. The first part of this series reports experimental conditions, used to follow colloid stability reported in the second part of the series.

Formation and stability of iron(II) oxidation products under natural concentrations of dissolved silica

Model solutions were used to evaluate the effect of dissolved silica on the mineralogy and stability of Fe(II) oxidation products. Mineralogy was evaluated with scanning electron microscopy (SEM) and X-ray diffraction. Stability was evaluated by measuring the decrease in turbidity of colloidal suspensions with time. At Si Fe molar ratios of 0.1 or less, oxidation of Fe(II) produced lepidocrocite, a moderately crystalline oxide that settled rapidly out of solution. At Si Fe molar ratios of 0.36 or higher, ferrihydrite formed from the oxidation of Fe(II). The ferrihydrite consisted of 0.1 μm spherical particles that were poorly crystalline and increasingly stable with higher Si Fe molar ratios. The ferrihydrite was similar in structure and composition to Fe oxide colloids isolated from two natural samples: (1) a reduced groundwater sample that was allowed to oxidize in the laboratory and (2) the colloidal particles in the < 1.0 μm size class of surface water samples from the Tualatin River watershed in northwest Oregon. The similarity of the natural and synthetic colloids is evidence that Fe oxide colloids in natural waters can result from the oxidation of Fe(II) and that dissolved silica may contribute to the stability of the colloids.

Aluminium(III)–pyrocatechol violet equilibria: a potentiometric study

The equilibrium reactions between aluminium(III) and the dye pyrocatechol violet {2-[(3,4-dihydroxyphenyl)(3-hydroxy-4-oxocyclohexa-2,5-dien-1-ylidene)methyl]benzenesulfonic acid, H4L} have been studied by potentiometric titration in aqueous solution, I= 0.10 mol dm–3 K(Cl), 25.0 °C. Equilibrium constants long βpqr for the reactions pH++qAl3++rH3L–⇌ H+pAl3+q(H3L–)rp+3q–r were determined, as were the dye deprotonation constants, log β–n,0,1(n= 1–3). The dye displayed both quinonoid and 1,2-dihydroxyaryl binding. The data were interpreted in terms of a series of complexes [Al(H2L)n](3 – 2n)+(quinonoid binding) forming at –log h < 4.5, where h is the free hydrogen-ion concentration, whereas at high –log h values the 1,2-dihydroxyaryl complexes [Al(HL)nL3 –n](n–9)+(n= 1–3) form. Mixed-site binding occurred at intermediate –log h values. Calculations confirmed that –log h= 5.6–6.5 is optimum for spectrophotometric measurements, with a 1 : 2 complex dominating in this range. Modelling calculations indicated that the presence of gibbsite colloids in natural waters could lead to a significant error in the determination of Al3+.

Applicability of photon correlation spectroscopy for measurement of concentration and size distribution of colloids in natural waters

The suitability of proton correlation spectrosocpy (PCS) for the determination of concentration and size distribution of colloidal matter was tested in a surface water and in a deep groundwater. Well-defined colloids (sizes predominately in the range 50–500 nm) of α-Fe2O3, γ-Al(OH)3, SiO2, kaolinite, illite and humic acid in aqueous solutions were used as references for calibration of the PCS-instrument (signal vs. concentration). The intensity of the scattered light was dependent on the composition of the colloid. The concentration ranges, where a quantitative determination of the colloid could be achieved, were 0.03–2 mg/1, 0.1–2 mg/1, 0.1–7 mg/1, 0.5–10 mg/1, 0.5–50 mg/1 and 0.5–75 mg/1 for α-Fe2O3, γ-Al(OH)3, SiO2, kaolinite, illite and humic acid, respectively (in homogeneous systems). The colloidal populations in the surface waters (inlet and outlet of a lake) had a size distribution in the range 100–500 nm. The measured count rates were around 330 kcps and 30 kcps at the inlet and outlet, respectively, which correspond to totally 2.8 mg/1 and 0.9 mg/1 of colloidal matter according to gravimetric determinations (collected on clogged 0.015 μm filters). Comparisons of concentrations estimated from measurements of reference colloids with PCS and gravimetric determinations of the colloidal showed that a combination of the two methods would be needed. The measurements of a deep groundwater were performed on-line and in situ with a PCS technique. The content of colloidal matter in the groundwater was below the detection limit for the PCS-equipment, which corresponds to a concentration not above 0.5 mg/1 and probably below 0.1 mg/1 in the present system. The feasibility and advantages of using PCS for non-disturbing size characterisation and concentration measurements of colloids in aquatic systems have been demonstrated, as well as some limitations of the method.

Factors controlling the stability of submicron colloids in natural waters

Particles are ubiquitous in all natural systems and play an important role in the control and fate of nutrients and pollutants. Submicron particles are especially important because they have large specific surface areas and high surface free energies which facilitate sorption of significant quantities of substances. Currently, only limited information is available on particle number and size distributions of natural submicron particles, owing to the significant problems involved in their experimental determination. In the present paper, existing data are discussed and compared with theoretical predictions based on a classical coagulation/sedimentation model where the kinetics of coagulation is described by Smoluchowski's equations and sedimentation is characterized by Stokes' law. Model predictions agree well with reported particle behaviour for particles larger than 100 nm. While classical theory does not explain the presence of colloids smaller than 100 nm in surface waters, the existence of such small colloids, embedded in large organic matrices, has been observed recently by high resolution transmission electron microscopy. Improvements in the measurement techniques available as well as development of the necessary theory to describe these organic/inorganic associations would be most welcome.

Determination of radionuclides associated with colloids in natural waters

Due to the interaction with components present in natural waters, radionuclides may be present in different physico-chemical forms, varying in size, charge and density. The distribution pattern will influence the transport, mobility and biological uptake of the radionuclides. Size fractionation based on hollow fiber is useful for the determination of the size distribution pattern of radionuclides in natural waters. Furthermore, a continuous mixing and separation system has been developed for the investigation of the association of radionuclides with naturally occurring colloids. Results based on radionuclides in waste water from the Forsmark nuclear power plant, Sweden, will illustrate the potential usefulness of the technique.

A review of light-scattering techniques for the study of colloids in natural waters

In order to understand the movement of colloidal materials in natural waters, we first need to have a means of quantifying their physical characteristics. This paper reviews three techniques which utilize light-scattering phenomena to measure the translational diffusion coefficient, the rotational diffusion coefficient, and the electrophoretic mobility of colloids suspended in water. Primary emphasis is to provide sufficient theoretical detail so that hydrologists can evaluate the utility of photon correlation spectrometry, electrophoretic light scattering, and electric birefringence analysis.