Concentrations Of Ionic Species Research Articles

Bioavailability and Toxicity of Heavy Metals in the Presence of Natural Organic Matter

The effect of humic acids (HA) on the toxicity of copper, zinc and lead was investigated in this study, using the photobacterium Vibrio fischeri (Microtox test) as a test organism. The metal species and the complexation capacity of HA were predicted using model WinHumicV for speciation modeling. The toxicities of copper and lead were generally comparable, while the toxicity of zinc was lower than the ones of the other two method. The toxicity of copper decreased with the addition of HA, while the toxicity of zinc remained almost constant. The complexation of Zn with HA was low. Thus the presence of HA did not significantly influence the toxicity of Zn. For Cu and Zn, the free metal ion species showed to be basically responsible for the toxicity of these metals, while for Pb the chlorocomplexes and Pb-HA complexes contributed to the toxicity of Pb, indicating that the toxicity of heavy metals depends not only on the free metal ion species concentration but on different metal species that may be bioavailable.

Semi-mechanistic Partial Buffer Approach to Modeling pH, the Buffer Properties, and the Distribution of Ionic Species in Complex Solutions

In many biological science and food processing applications, it is very important to control or modify pH. However, the complex, unknown composition of biological media and foods often limits the utility of purely theoretical approaches to modeling pH and calculating the distributions of ionizable species. This paper provides general formulas and efficient algorithms for predicting the pH, titration, ionic species concentrations, buffer capacity, and ionic strength of buffer solutions containing both defined and undefined components. A flexible, semi-mechanistic, partial buffering (SMPB) approach is presented that uses local polynomial regression to model the buffering influence of complex or undefined components in a solution, while identified components of known concentration are modeled using expressions based on extensions of the standard acid-base theory. The SMPB method is implemented in a freeware package, (pH)Tools, for use with Matlab. We validated the predictive accuracy of these methods by using strong acid titrations of cucumber slurries to predict the amount of a weak acid required to adjust pH to selected target values.

Seven-year trend and the time and seasonal dependence of fog water collected near an industrialized area in Japan

Fog chemistry was studied for 7 years (April 1997 to March 2004) at Mt. Rokko (altitude 931 m) in Kobe, Japan. Sample collection was carried out at a mountainous site close to a highly industrialized area. Almost no increasing trend was observed in the liquid water content (LWC) and in the concentrations of ion species over the study period. The frequency of fog occurrence was high in summer, with fog occurring more frequently at night. The LWC was large at night and a time dependence was observed in the ion species concentrations: NH 4 + and non-sea-salt-(nss-)Ca 2+ concentrations were higher during the day than at night, although only a small time dependence was observed for NO 3 − and nss-SO 4 2− concentrations. The differences in the time dependence of NO 3 −, nss-SO 4 2−, NH 4 + and nss-Ca 2+ concentrations were attributed to the time dependence of the H + concentration in that the H + concentration during the day was lower than that at night. A significant difference in the concentrations of ion species between ambient air and fog water was observed in components composed of fine particles, while no significant difference was seen in components composed of coarse particles.

Characteristic study of ionic species in nano, ultrafine, fine and coarse particle size mode at a traffic sampling site

A micro-orifice uniform deposit impactor (MOUDI) and a nano-MOUDI were used to measure the atmospheric coarse (PM2.5-10), fine (PM2.5), ultrafine (PM0.056-1) and nano (<0.056 microm) particle concentrations at a traffic sampling site in central Taiwan during the winter period from November 2004 to January 2005. Meanwhile, concentrations of major ionic species (Cl-, NO3-, SO(2-)4, NH4+, Na+, K+, Ca2+ and Mg2+) were also extracted from various particle size modes (nano, ultrafine, fine and coarse) and analysed by ion chromatography (DIONEX-100). The mass size distribution of ambient suspended particles exhibited two modes. The size ranges of the particles at these two particle size modes were between 1.0 and 1.8 microm and 3.2 and 5.6 microm, respectively. The average mass media aerodynamic diameter (MMAD) of suspended particles was 0.99 microm in this study. In addition, statistical methods, such as correlation coefficient and principal component analysis, were also used to identify the possible pollutant source for various particles size modes (nano, ultrafine, fine and coarse) during the winter months at a traffic sampling site in central Taiwan.

Comparison of PM2.5 and PM10 in A Suburban Area in Korea During April, 2003

Airborne particulate matter (PM) concentrations were measured in Iksan, a suburban area in South Korea during April, 2003. PM2.5 (particles with an aerodynamic diameter less than 2.5 μm) and PM10 (particles with an aerodynamic diameter less than 10 μm) samples were collected, and the chemical characteristics of particles were examined for diurnal patterns, yellow dust/rainfall influences, and scavenging effects. Average concentrations of PM2.5 and PM10 mass measured were 37.3 ± 16.2 μg m−3 and 60.8 ± 29.5 μg m−3, respectively. The sum of ionic chemical species concentrations for PM2.5 and PM10 was 16.9 ± 7.3 and 23.1 ± 10.1 μg/m3, respectively. A significant reduction in PM mass concentrations during rainfall days was observed for coarse mode (PM2.5 − 10) particles, but less reduction was found for fine (PM2.5) mass concentration. SO42−, NH4+, and K+ predominated in fine particulate mode, NO3− and Cl− predominated in fine particle mode and coarse particle mode, but Na+, Mg2+, and Ca2+ mostly existed in coarse mode. The high concentration of ammonium due to local emissions and long-range transport neutralized sulfate and nitrate to ammonium sulfate and ammonium nitrate, which were major forms of airborne PM in Iksan. Average mass concentrations of PM10 in daytime and at night were 57.6 and 70.0 μg m−3, and those of PM2.5 were 35.4 and 42.5 μg m−3, respectively. NO3− and Cl− in both PM2.5 and PM10 were about double at night than in the daytime, while the rest of the chemical species were equal or a little higher at night than in the daytime. The results suggest the formation of ammonium nitrate and chloride when high ammonia concentration and low air temperature are allowed. Backward air trajectory analyses showed that air masses arriving at the site during yellow dust period were transported from arid Chinese regions, which resulted in high concentrations of airborne PM mass concentrations. In the meantime, air mass trajectories during a rainfall period were mostly from the Pacific Ocean or the East China Sea, along with a relatively low PM concentration.

Concentrations of ambient air particulates (TSP, PM 2.5 and PM 2.5–10) and ionic species at offshore areas near Taiwan Strait

The concentrations of total suspended particulate (TSP), fine particles PM 2.5 (with aerodynamic diameter <2.5 μm), coarse particles PM 2.5–10 (with aerodynamic diameter 2.5–10 μm,), and water-soluble inorganic ions were studied at two offshore sampling sites, Taichung Harbor (TH) and Wuci Traffic (WT), near Taiwan Strait in central Taiwan during March 2004 to January 2005. Statistical analyses were also carried out to estimate the possible sources of particulate pollution. Experimental results showed that the average mass concentrations of TSP, PM 2.5 and PM 2.5–10 at TH and WT sampling sites were 154.54 ± 31.45 and 113.59 ± 31.94 μg m −3, 54.03 ± 16.92 and 42.76 ± 12.52 μg m −3, and 30.31 ± 9.79 and 24.16 ± 7.27 μg m −3, respectively. The dominant inorganic ions at two sampling sites were SO 4 2−, NO 3 −, and NH 4 + for TSP and PM 2.5, but that were Ca 2+, Cl −, and Na + for PM 2.5–10. The concentrations of most particulates and inorganic ions were higher in winter at both two sampling sites, and were higher at TH than WT sampling site in each season. From statistical analysis, air-slake of crust surface, sea-salt aerosols, agriculture activities, coal combustion, and mobile vehicles were the possible emission sources of particulate pollution at TH and WT sampling sites.

Monitoring of Fogwater Chemistry in the Gulf Coast Urban Industrial Corridor: Baton Rouge (Louisiana)

Seventeen fog events were sampled in Baton Rouge, Louisiana during 2002-2004 as part of characterizing wet deposition by fogwater in the heavily industrialized corridor along the Louisiana Gulf Coast in the United States. These samples were analyzed for chemical characteristics such as pH, conductivity, total organic and inorganic carbon, total metals and the principal ion concentrations. The dominant ionic species in all samples were NH4+, NO3-, Cl- and SO4(2-). The pH of the fogwater sampled had a mean value of 6.7 with two cases of acidic pH of 4.7. Rainwater and fogwater pH were similar in this region. The acidity of fogwater was a result of NO3- but partly offset by high NH4+. The measured gaseous SO2 accounted for a small percentage of the observed sulfate concentration, indicating additional gas-to-particle conversion of SO2 to sulfate in fogwater. The gaseous NOx accounted for most of the dissolved nitrate and nitrite concentration in fogwater. The high chloride concentration was attributable to the degradation of chlorinated organics in the atmosphere. The metal composition was traced directly to soil-derived aerosol precursors in the air. The major metals observed in fogwater were Na, K, Ca, Fe, Al, Mg and Zn. Of these Na, K, Ca and Mg were predominant with mean concentrations > 100 microM. Al, Fe and Zn were present in the samples, at mean concentrations < 100 microM. Small concentrations of Mn (7.8 microM), Cu (2 microM), Pb (0.07 microM) and As (0.32 microM) were also observed in the fogwaters, and these were shown to result from particulates (PM2.5) in the atmosphere. The contribution to both ions and metals from the marine sources in the Louisiana Gulf Coast was minimal. The concentrations of all principal ionic species and metals in fogwater were 1-2 orders of magnitude larger than in rainwater. Several linear alkane organic compounds were observed in the fogwater, representing the contributions from petroleum products at concentrations far exceeding their aqueous solubility. A pesticide (atrazine) was also observed in fogwater, representing the contribution from the agricultural activities nearby.

The bias-assisted HF CVD nucleation of diamond: Investigations on the substrate temperature and the filaments location

Diamond films were deposited on Si (100) substrates by a direct current and hot filaments-assisted CVD technique at different substrate-to-filaments distances and nucleation temperatures. The nucleation temperature in the range of 600–850 °C has negligible influence on the diamond nucleation density and the film quality. Conversely, the nucleation density is closely related to the distance between the filaments and the substrate during the nucleation step. This distance can be optimized to yield a high nucleation rate with good film quality. At too low distance, intense secondary nucleation takes place whereas at too high distance, poor nucleation occurs due to a decreasing ion-promoted nucleation process. The filaments-to-substrate distance governs through intense electron emission the concentration of ion species above the substrate and thus, to a certain extent, governs the nucleation rate.

Observational and modeling studies of chemical species concentrations as a function of raindrop size

The Guttalgor method has been used to determine the chemical species concentrations in size-selected raindrops in nine rain events at Hong Kong from 1999 to 2001. The curve (concentration against raindrop radius) patterns for all the species are similar but depend on the starting time of sampling within a rain event. In these plots, the maximum concentration occurs at the same range of droplet radius, irrespective of the species, and this indicates the importance of coalescence and breakup processes. The maximum is located at a smaller droplet radius than was found in previous studies in Germany. All results show almost constant concentrations with size for large raindrops, and these indicate the in-cloud contributions. The pH of raindrops of similar size is linearly correlated with a function of the sulfate, nitrate, acetate, formate, calcium and ammonium ion species concentrations. Within a single raindrop, chloride depletion is not significant, and sulfate, ammonium and hydrogen ions are found in ratios compatible with the precursor solid-phase mixture of ammonium sulfate and ammonium bisulphate. When simulated by a below-cloud model, good agreement between the modeled and measured sodium and sulfate concentrations has been found. Below-cloud sulfur dioxide scavenging contributes at most 60% of the sulfate concentration in a single raindrop.

Modeling the Precipitation of l-Glutamic Acid via Acidification of Monosodium Glutamate

A new insight for quantitative determination of the complex interaction of kinetics of reactive crystallization is gained by a study of the acidification of monosodium glutamate with hydrochloric acid in a semi-batch reactor. The dynamic equilibrium of the l-glutamic acid ions, their simultaneous presence in the solution, and the effect on the crystal size and size distribution are simulated using a mathematical model based on integration of the population balance equation with the crystallization kinetics and thermodynamics of the process. The model includes equations of chemical reactions, pH, nucleation, size-independent growth, and population balance. This allows a precise determination of the driving force for the reactive crystallization and the parameters of the nucleation and crystal growth rate expressions. The model considers the effect of the controlling parameters such as the rate of addition of the acid and the initial concentrations of ionic species and can be used to predict the concentrati...

Idiopathic urinary stone disease: possible polygenic aetiological factors

About 12% of men and 5% of women of Western European descent develop at least one urinary stone during their lifetime. The incidence is somewhat less in individuals of sub-Saharan African or Asian descent, although there is a high incidence in the Middle Eastern countries. Calcium oxalate is a major constituent of about 70% of these stones. They are of multifactorial origin, with both genetic and environmental factors involved. The genetic factors influence different components of a highly complex system whereby calcium oxalate, which has a very low solubility in water, remains in solution. When the system is perturbed, the calcium oxalate crystallizes, the crystals aggregate and stones form. The genetic factors operate through mechanisms that are less obvious than the environmental ones such as the patient's state of hydration and dietary effects on the concentrations of the relevant ionic species. It is now generally accepted that the crystallization process begins in the distal ducts of the kidney by adhesion of calcium and oxalate to the epithelial surfaces of the tubule cells and their internalization. The calcium oxalate crystal becomes detached, with some incorporated organic materials forming a microlith. This process of microlith formation could arise either because of genetically determined alterations in the surface properties of the cells, or in the composition and/or concentration of substances in the urine that inhibit crystal nucleation and/or aggregation. The microliths pass through the collecting tubules more slowly than calcium oxalate in simple physical solution, aggregating until they reach the pelvicalycial system, where they grow into stones and pass down the ureters. It has been suggested that a shift in the crystal form from the mono-hydrate to the di-hydrate form reduces the likelihood of such adhesion, and that molecular inhibitors of crystallization operate by favouring the dihydrate form.1 Calcium oxalate urolithiasis had, … Address correspondence to Dr R.W.E. Watts, Renal Section, Division of Medicine, Imperial College, London, Hammersmith Campus, Du Cane Road, London W12 0NN

Experimental study and numerical estimation of current changes in electroosmotically pumped microfluidic devices

Electroosmotic flow (EOF) was investigated in microfabricated fluidic devices using the current monitoring technique. Current changes ranging from 50 to 130 pA/s were detected. These observations indicate that in microfluidic devices with small reservoir volumes, electrolysis of water influences the fluid transport, giving rise to changes in pH and increase in concentration of ionic species in the fluidic system. As a result of the electrolysis and associated increment in ion concentration, the thickness of the Debye layer and surface potential vary, affecting the overall migration behavior of the solution. The magnitude of EOF and the electrophoretic properties of molecules can no longer be treated as constant/invariant. These temporal anomalies are undesirable during analytical separations and in fluid control applications. A numerical analysis of the impact of the continuous ionic strength increase on the EOF dynamics is presented using well-established conduction and EOF theories. The numerical results are found to be in good agreement with the observed current changes. These results indicate that to improve assay reproducibility, monitoring the electric current is an effective tool to determine whether electrolytic reactions are taking place. Our work also serves to test the numerical accuracy of EOF theories and models.

Source contributions to fine particulate matter in an urban atmosphere

This paper proposes a practical method for estimating source attribution by using a three-step methodology. The main objective of this study is to explore the use of the three-step methodology for quantifying the source impacts of 24-h PM 2.5 particles at an urban site in Seoul, Korea. 12-h PM 2.5 samples were collected and analyzed for their elemental composition by ICP-AES/ICP-MS/AAS to generate the source composition profiles. In order to assess the daily average PM 2.5 source impacts, 24-h PM 2.5 and polycyclic aromatic hydrocarbons (PAH) ambient samples were simultaneously collected at the same site. The PM 2.5 particle samples were then analyzed for trace elements. Ionic and carbonaceous species concentrations were measured by ICP-AES/ICP-MS/AAS, IC, and a selective thermal MnO 2 oxidation method. The 12-h PM 2.5 chemical data was used to estimate possible source signatures using the principal component analysis (PCA) and the absolute principal component scores method followed by the multiple linear regression analysis. The 24-h PM 2.5 source categories were extracted with a combination of PM 2.5 and some PAH chemical data using the PCA, and their quantitative source contributions were estimated by chemical mass balance (CMB) receptor model using the estimated source profiles and those in the literature. The results of PM 2.5 source apportionment using the 12-h derived source composition profiles show that the CMB performance indices; χ 2, R 2, and percent of mass accounted for are 2.3%, 0.97%, and 100.7%, which are within the target range specified. According to the average PM 2.5 source contribution estimate results, motor vehicle exhaust was the major contributor at the sampling site, contributing 26% on average of measured PM 2.5 mass (41.8 μg m −3), followed by secondary sulfate (23%) and nitrate (16%), refuse incineration (15%), soil dust (13%), field burning (4%), oil combustion (2.7%), and marine aerosol (1.3%). It can be concluded that quantitative source attribution to PM 2.5 in an urban area where source profiles have not been developed can be estimated using the proposed three-step methodology approach.

Modeling ion and fluid transport in unsaturated cement systems in isothermal conditions

A description of ionic transport in unsaturated porous materials due to gradients in the electro–chemical potential and the moisture content is developed by averaging the relevant microscopic transport equations over a representative volume element. The complete set of equations consists of time-dependent equations for both the concentration of ionic species within the pore solution and the moisture content within the pore space. The electrostatic interactions are assumed to occur instantaneously, and the resulting electrical potential satisfies Poisson's equation. Using the homogenization technique, moisture transport due to both the liquid and vapor phases is shown to obey Richards' equation, and a precise definition of the moisture content is found. The final transport equations contain transport coefficients that can be unambiguously related to experimental quantities. The approach has the advantage of making the distinction between microscopic and bulk quantities explicit.

Ion species mix measurements in DIII-D and International Thermonuclear Experimental Reactor using ion–ion hybrid layer reflectometry

A superheterodyne reflectometer can provide a direct and inexpensive measurement of the concentrations of ion species with different charge to mass ratios. The ion–ion hybrid cutoff frequency is uniquely determined by the cyclotron frequencies and concentrations of the different species. The phase of a ∼20 MHz wave that travels from a launching antenna on the low-field side of a tokamak, reflects off the cutoff layer, then travels to a receiving antenna provides a direct measure of the species mix. Hydrogen concentrations between 3% and 67% are measured in DIII-D using this technique. In theory, the technique can measure the spatial profile of the tritium concentration in the International Thermonuclear Experimental Reactor. Possible practical difficulties include attenuation of the wave in the evanescent layer near the antenna.

Aerosol composition and its sources at the King Sejong Station, Antarctic peninsula

The annual cycles of major metals and ions in suspended particulate matters (SPM) have been investigated at a costal site of the Antarctic Peninsula in order to elucidate temporal variations as well as major source processes responsible for their formation. The measurements had been performed from January 2000 to December 2001 at the Korean Antarctic research station, ‘King Sejong’ (62°13′ S, 58°47′ W). The observed time series of important aerosol components showed clear seasonal variation patterns, while the mean elemental concentrations (e.g., 1875 (Al), 10.3 (Ba), 0.3 (Bi), 1.3 (Cd), 1.7 pg m−3 (Co)) were generally compatible with those reported previously. The presence of high EF values with respect to both mean crustal and seawater composition (such as Bi, Cd, Cr, Cu, Ni, V, and Zn), however, suggests a possibly important role of anthropogenic processes in this remote site. In contrast, the concentrations of ionic species were not clearly distinguishable from those of other Antarctic sites; but the consideration of ionic mass balance between cations and anions pointed out the uniqueness of their source/sink processes in the study area. The major source processes of those aerosol components were also investigated using a series of statistical analyses. The overall results of our study indicated the dominance of several processes (or sources) such as sea-salt emission, secondary aerosol formation, and anthropogenic pollution from both local and distant sources.

Investigation of chemical effects on the performance of flow-through dialysis applied to the determination of ionic species

In this paper, the influence of chemical variables on the mass transfer kinetics of ionic species under dynamic conditions in flow-through sandwich-type dialysers is thoroughly investigated. Although the driving force of the mass transport is the existence of a concentration gradient between the two phases separated by a semi-permeable membrane, it has been demonstrated that the chemical composition of both donor and acceptor solutions in terms of concentration and kind of ionic compounds has a significant influence on the mass transfer efficiency. The Donnan effect on passive dialysis and the fast migration of ions concomitantly present with the target species improved the transfer of the analyte ion in the membrane separation process. Thus, for the determination of low molecular weight anions, the addition of cationic species with high transport index, such as oxonium ion, to the donor stream, or multicharged ions (e.g. Al 3+) to the recipient stream, enhanced the dialysis yields more than 62% with respect to the use of water as acceptor and sample medium. As a consequence of the dependence of the dialysis rate on the composition of the sample matrix, different diffusate concentrations were encountered for the same input concentration of analyte when prepared in different electrolytic media. In order to balance the chemical potential on the donor side, the ionic strength for both standards and sample solutions should be carefully adjusted via incorporation of a modifier stream in the flow manifold (e.g. 1.0 mol l −1 KNO 3 or 0.5 mol l −1 H 2SO 4) as demonstrated in the bulk of the text. Appropriate buffering of the recipient solution was equally effective. Furthermore, these strategies were found suitable to overcome the lack of linearity observed by several researchers in in-line dialytic processes at low concentrations of ionic species caused by polar interactions with the membrane surface. Chloride was selected as a model of target species for assessing the effect of chemical variables on the mass transfer rate in flow-through parallel-plate dialyser units. The spectrophotometric detection scheme for chloride, implemented in a secondary flow configuration, is based on the displacement reaction of thiocyanate from the corresponding mercury salt in the presence of iron(III).

Approximate Expression for the Critical Coagulation Concentration of a General Electrolyte Solution

The critical coagulation concentration of a colloidal dispersion for the case of a general electrolyte solution is estimated under the conditions of constant surface potential. By combination of the Langmuir approximation and the Debye−Huckel approximation, explicit expressions for the electrical potential, the osmotic pressure, and the electrical energy are derived, and the results are used to estimate the critical coagulation concentration of ionic species. The influence of the valence of ionic species on this concentration is discussed. We show that the Schultz−Hardy rule is invalid, in general, and that the effect of co-ions can be too large to be ignored.

Poly(ethylene oxide)–polyurethane/poly(acrylonitrile) semi-interpenetrating polymer networks for solid polymer electrolytes: vibrational spectroscopic studies in support of electrical behavior

Studies on solid polymer electrolyte systems based on semi-interpenetrating polymer networks of poly(ethylene oxide)–polyurethane and poly(acrylonitrile) (PEO–PU/PAN) doped with lithium trifluoromethanesulfonate (LiCF 3SO 3) is reported. Room temperature FT-IR analysis indicates a salt solvation process that occurs predominantly in the polyether segments of the semi-IPNs and incorporation of salt is also seen to favor a morphological change in the matrix with a transition from semi-crystalline to amorphous phase. From the relative band areas a critical concentration ( C c) of salt can be identified where concentration of ionic species, morphology and amount of transient crosslinks is optimal to impart maximum conductivity, which is in agreement with the room temperature conductivity results. Thermal analysis of the semi-IPN lends further support to this observation. The temperature dependence of conductivity is found to follow the Arrhenius behavior at low temperatures (∼ upto 328 K) and VTF dependence at higher temperatures. This crossover in temperature dependent conductivity is attributed to the change in the phase morphology of the semi-IPNs beyond the crystalline melting temperature ( T m1) of the polyether segments.

Surface Film Resistance As An Environmental Sensor

Although not the only reason that electronics fail, environmental corrosion is the principal reason in the majority of cases. Therefore an elementary approach to controlling the corrosion of electronic parts is to controlthe environment. The combination of relative humidity (RH) and deposited ionic species cause corrosion damage as well as current leakage on insufficiently protected parts of integrated circuits. An analysis based on mixed potential theory illustrates that the surface film resistance between anodic and cathodic sites has a major influence on the corrosion current. Surface film resistance depends on both the concentration of ionic species and on the thickness of an adsorbed moisture layer, which is a function of relative humidity. The presence of one without the other prevents significant corrosion current from flowing. Electrochemical impedance spectroscopy results indicated that the modulus of impedance at 100 kHz is a meaningful measure of the solution resistance between surface electrodes. Measurements of surface film resistance could be used in an environmental control system by indicating conditions where leakage current is significant and/or the periods of time where corrosion current is significant, i.e. as a time-of-corrosion sensor.