Ionic Mass Balance Research Articles

Impact of biomass burning and non-exhaust vehicle emissions on PM10 levels in a mid-size non-industrial western Iberian city

PM10 aerosol was measured during one semester, simultaneously, at a roadside (RS) and an urban background (UB) location in Coimbra, Portugal. On average, the mass concentrations were 36% higher at the RS, compared to UB. Application of Positive Matrix Factorisation (PMF) and Ionic Mass Balance (IMB) methodologies permitted to source apportion the aerosol mass. During the cold season, biomass burning was a prevalent particulate matter source at both urban locations, contributing with up to 30% of PM10. At the RS, vehicle non-exhaust emissions (brake, tyre and road dust) doubled exhaust emissions by combustion engines, accounting for 18–19% of PM10. Unreacted and reacted sea salt was an important fraction of PM10, principally during the warm season, when it composed approximately 25% of the aerosol. Secondary pollution by ammonium salts and carbonaceous matter was important across the seasons, especially at the UB location, where they dominated the particulate mass.

The comparative study for scale inhibition on surface of RO membranes in wastewater reclamation: CO2 purging versus three different antiscalants

The application of reverse osmosis (RO) membrane in wastewater reclamation is emerged as a potential technology. As far as the operational conditions are concerned, inorganic fouling is a major challenge for membrane treatment systems. At present various antiscalants and chemicals are commercially available for scale inhibition on the surface of membrane. In an earlier study we found that CO2 can effectively inhibit scale growth on the surface of RO membrane in wastewater reclamation. On the basis of previous study, the scale inhibiting efficiency of CO2 was compared with three commercially available antiscalants. The RO system was operated at constant applied pressure with four different scale inhibition methods including CO2, Flocon 260, Flocon 300 and Kuriverter N-500. The permeate flux decline was considered as an indication of scale growth on the membrane surface. The percent salt rejection and ionic mass balance was used to determine the scaling behavior of the RO modules. Membrane autopsy was done to determine the effect of CO2 and antiscalants on the membrane structure. The experimental data revealed that CO2 can effectively inhibit scale growth as compared with all of three antiscalants. However, the Flocon 260 was found better than other two antiscalants.

Carbon dioxide flux in the ablation area of Koxkar glacier, western Tien Shan, China

AbstractAccelerating loss of glacial mass caused by rising global temperatures has significant implications. The global cycle of the greenhouse gas CO2 is also associated with mineral weathering and glaciation. In glaciated areas, most estimates of atmospheric CO2 consumption are confined to chemical ionic mass balance or analog modeling methods. We applied the gradient method to the surface of Koxkar glacier, western Tien Shan, China, for a 5 month period during 2012. The overall net glacier-system CO2 exchange (NGE) rate was measured as -0.05 and -0.07mmol m–2 s–1 for regions of exposed ice and supraglacial moraine, respectively. This suggests that atmospheric CO2 drawdown may occur during ice melting because of consumption of H+ by CO2 hydrolysis that occurs in solutions. Using the degree-day model to calculate glacier ablation in bare-ice regions and considering characteristics of the NGE rate in the supraglacial debris region with the support of GIS, the daily NGE rate was estimated to be -1.23 ± 0.17μmmol m–2 d–1 between Julian days 125 and 268 of 2012. These findings present a new approach for modeling the dynamics of glacial CO2 sinks undergoing melting, and develop an understanding of the mechanism of atmospheric CO2 exchange.

Hemodialysis in Chronic Kidney Disease - Balancing Fluid and Salt on the Inflammation Tightrope

Haemodialysis (HD) is a well-established, longstanding, and life-saving treatment for patients with chronic kidney disease (CKD) or acute kidney injury (AKI). However, side-effects of HD in CKD patients are numerous and remain problematic. Amongst others, CKD patients are susceptible to short-term effects caused by abnormalities in water and electrolyte balance and long-term effects related to sustained inflammation short-term side-effects of HD such as errors in sodium content of dialysate could readily be overcome by correct baseline labelling of dialysates and the ongoing rigorous implementation of safety procedures by staff nurses and physicians. The proper implementation of biofeedback systems, with tight safety alarm limits and conductivity based detection systems including the analysis of ionic mass balance could have prevented the shortfalls described. Long-term untoward effects of HD are mainly due to sustained inflammation and are correlated with higher morbidity and mortality. Unfortunately, the pathophysiologic mechanisms that underpin the inflammatory processes induced by HD remain poorly understood or incompletely unravelled. Within the wide array of inflammatory (inter)actions, cytokines are undoubtedly key players but interesting biomarkers (e.g. follistatin) and pathways (e.g. erythropoietin hyporesponsiveness) have come into play. Therapeutic interventions in differing fields such as vascular access, avoidance of intra-dialytic hypotension and pharmacologic interventions with statins, angiotensin II receptor antagonists or vitamine D supplementation may be of significance. However, confirmatory trials investigating of all these promising therapies are, as yet, lacking. The impact of the dialysis technique itself should not be underestimated.

Use of Online Conductivity Monitoring to Study Sodium Mass Balance in Chronic Haemodialysis Patients: Prospects for Treatment Individualisation

Background: Failure to achieve isonatric haemodialysis (HD) drives an expansion of extracellular volume leading to increased interdialytic weight gain (IDWG). This may be a causative factor in the development of HD-induced cardiac injury. We examined total and diffusive sodium mass balance during HD. Methods: 24 chronic HD patients using a fixed 140 mmol/l sodium concentration were studied over 4 weeks. Dialysate and plasma conductivity and ionic mass balance (IMB) were recorded. IMB estimates total ionic transfer across the HD membrane. Results: Mean total IMB was 338 mmol indicating net sodium removal. Intrapatient variability was less than interpatient variability (coefficient of variation = 42 vs. 26%, respectively). The diffusive component of ionic mass balance (IMB_diff) was 97 ± 18 mmol approximating 29% (±22–36) of total sodium removal. IMB_diff also correlated with both plasma conductivity and predialysis plasma sodium (r² = 0.82 and 0.6, respectively; p < 0.0001) as well as the reduction in plasma conductivity and plasma sodium during HD (r² = 0.7 and 0.5, respectively; p < 0.0001). Conclusion: HD against a fixed dialysate sodium concentration of 140 mmol/l results in a wide range of sodium removal with a mean of 29% removed by diffusion. Online conductivity monitoring can be utilized as part of a variety of strategies to enable the delivery of individualised and isonatric HD. Further study is required to explore the utility of such strategies which may be crucial in reducing IDWG and HD-induced cardiac injury.

Variations in Predialytic Plasma Conductivity in Dialysis Patients: Effect on Ionic Mass Balance and Blood Pressure

In this study, variations in plasma conductivity (PC), as a surrogate marker of plasma sodium, as well as its relation with intradialytic ionic mass balance (IMB) and blood pressure were assessed in 73 patients. Plasma conductivity and IMB were retrieved on a treatment to treatment basis during a 6-month period. Dialysate sodium concentration was 140 mmol/L. A total of 4070 treatments were analyzed. Mean coefficient of variation for predialytic PC was 1.3%, and mean intraindividual range in predialytic PC measurements during the 6-month follow-up period was 0.9 mS/cm (plasma sodium ∼ 9 mmol/L). Predialytic PC was related to both diffusive and total IMB (r = 0.91, p < 0.001; and r = 0.35, p < 0.01). The average diffusive IMB over a 6-month period was negative in 33% of patients, and the average PC increased during dialysis in 14% of patients. Averaged predialytic PC was significantly related to systolic blood pressure (r = 0.35; p < 0.01), whereas within patients, predialytic systolic blood pressure was significantly different between treatments with the lowest and highest predialytic PC (139 ± 24 vs. 147 ± 21 mm Hg; p < 0.05). In conclusion, depending on PC, diffusive ionic transfer from dialysate to patient may occur in a significant percentage of patients using a dialysate sodium concentration of 140 mmol/L. Variations in PC are related to blood pressure, which might suggest a volume-independent effect of sodium.

Lowering Postdialysis Plasma Sodium (Conductivity) to Increase Sodium Removal in Volume-Expanded Hemodialysis Patients: A Pilot Study Using a Biofeedback Software System

Extracellular fluid expansion is common in hemodialysis patients. Aggressive fluid removal may lead to intradialytic complications. High dialysate sodium concentrations may lessen complications, but may increase extracellular volume. We hypothesized that decreasing plasma sodium concentration during dialysis will increase sodium removal and decrease extracellular volume. Pilot clinical trial. 16 patients with end-stage kidney disease treated using thrice-weekly hemodialysis at a university teaching hospital hemodialysis unit. Stepwise decrease in postdialysis plasma sodium level (calculated as end-of-session plasma conductivity) over 4 phases effected by dialysate conductivity measurement cells and a biofeedback software system (Diacontrol; Hospal, www.hospal.it) that allowed alteration of dialysate inlet conductivity and calculation of plasma conductivity. Decrease in postdialysis plasma sodium (conductivity) levels, sodium removal, redistribution of body water, and effect of these on interdialytic weight gain and blood pressure. Plasma sodium and conductivity values (the latter measured in millisiemens per centimeter); ionic mass balance (sodium removal); bioelectrical impedance analysis measurements of body-water compartments and phase angle; interdialytic weight gain; and blood pressure. Plasma sodium concentrations at the end of dialysis were decreased from 137.8 (phase 1) to 135.6 mmol/L (phase 4) and end-of-session plasma conductivity values were decreased from 14.0 (phase 1) to 13.5 mS/cm (phase 4; all mean values). Ionic mass balance increased from 383 to 480 mmol. Extracellular water was significantly decreased, phase angle was increased, and blood pressure and interdialytic weight gain were decreased. Plasma sodium levels correlated significantly with plasma conductivity; thus, changes in postdialysis plasma sodium levels can be inferred from changes in end-of-session plasma conductivity values. Small number of patients. No information for dietary sodium intake. To decrease extracellular volume, it may be necessary to add diffusive to convective sodium losses.

Conductivity pulses needed for Diascan® measurements: does it cause sodium burden?

Sir, Recent, New techniques based on conductivity measurement enable physicians to evaluate the adequacy of haemodialysis dose (HDD) on all haemodialysis treatments by on-line monitoring of Kt/V. Ionic dialysance (Diascan® Hospal-Gambro, Mirandola, Italy) is a parameter calculated from the dialysate conductivity at the dialyser inlet and outlet. Every half hour, the inlet dialysate conductivity increases by 1 ms/cm during 5 min, while the outlet dialysate conductivity-cell measures the effect of this increase. The calculated ion transfer across the membrane (largely sodium) is almost equivalent to urea transfer and therefore ionic dialysance reflects the urea clearance. This method has been shown to have a good correlation with Kt/V measured by the mathematical urea equations in several studies [1–4]. However, some investigators suggest that during the conductivity pulse of 5 min, significant amounts of sodium may be transferred into the patient [5]. In our centre, we studied that effect. Diascan® also measures ionic mass balance (IMB) and plasma conductivity (PC) that are likely to represent sodium balance and plasma sodium, respectively (plasma sodium in mmol/l ≈ plasma conductivity in ms/ cm × 10). This is performed by constant measurements of the conductivity in the dialysate inlet and outlet, according to the formulas where Qdin and Qdout are dialysate flow at, respectively, inlet and outlet, Cdin and Cdout are dialysate conductivity at, respectively, inlet and outlet and D is ionic dialysance, and A positive IMB means sodium removal from the patient. A negative IMB means sodium transport to the patient. In patients with zero inter-diaytic weight gain, IMB was measured in 200 isovolaemic haemodialysis sessions by Diascan®, 137 sessions were performed with four to eight conductivity pulses. A total of 63 sessions was performed with only one conductivity pulse. The results showed a highly significant correlation between pre-dialytic plasma conductivity and IMB (Spearman rank rs = 0.902, P < 0.005), in agreement with previous studies [6]. There was no correlation between IMB and the number of conductivity pulses (Spearman rank rs = 0.02, P = 0.328) (Figure ​(Figure11). Fig. 1 Correlation between IMB during isovolaemic haemodialysis and number of conductivity pulses. In conclusion, Diascan® is a useful tool to assess HDD without evidence of an increased sodium load related to the conductivity pulses during haemodialysis treatment. Conflict of interest statement. None declared.

The effect of sodium profiling and feedback technologies on plasma conductivity and ionic mass balance: a study in hypotension-prone dialysis patients

Sodium profiling improves haemodynamic tolerance in haemodialysis (HD) patients but may also influence sodium homeostasis. Changes in blood volume and plasma conductivity (PC) during HD can be modelled by feedback technology, but their effects on sodium homeostasis are not widely studied. This randomized crossover study compared PC and ionic mass balance (IMB) as surrogate markers of sodium balance between standard HD [dialysate conductivity (DC) 14.0 mS/cm], sodium profiling (DC 15.0-->14.0 mS/cm), blood volume (BV)-controlled and PC-controlled feedback (target: post-HD PC: 14.0 mS/cm) in 10 HD patients with frequent hypotension. 440 treatments were studied. Pre-dialytic PC was significantly higher during SP (14.4+/-0.2 mS/cm) compared to standard HD (14.2+/-0.3 mS/cm), and was not different between the other manoeuvres: PC-controlled (14.1+/-0.3 mS/cm), and BV-controlled feedback (14.2+/-0.2 mS/cm). Except for the first treatment, during which IMB was lower during the sodium profile, IMB did not differ significantly between the various manoeuvres and was strongly dependent upon ultrafiltration volume and the difference between pre-dialytic PC and DC. Symptomatic hypotensive episodes occurred least frequently during BV-controlled feedback (8%) compared to the other manoeuvres (standard HD, 16%; sodium profile, 14%; PC-controlled feedback, 17%), but differences were not significant. Inter-dialytic weight gain and pre-dialytic systolic blood pressure did not differ. Pre-dialytic PC increased during the sodium profile, and did not differ between BV- or PC-controlled feedback compared to standard HD. Thus, it appears that both BV- and PC-controlled feedback can be safely prescribed without substantial salt- and water-loading, at least in the short term. Analysis of IMB is useful to assess differences in sodium balance between single treatment sessions but appears of less value in a steady-state situation.

Online Conductivity Monitoring: Validation and Usefulness in a Clinical Trial of Reduced Dialysate Conductivity

Relatively low dialysate conductivity (Cndi) may improve outcomes by reducing the overall sodium burden in dialysis patients. Excess sodium removal, however, could lead to hemodynamic instability. We performed a randomized controlled trial of reduction of Cndi. For the study, 28 patients were randomized to maintenance of Cndi at 13.6 mS/cm (equivalent to 135 mmol/L of Na+) or serial reduction of Cndi in steps of 0.2 mS/cm, guided by symptoms and blood pressure. Sodium removal estimated from pre- and postplasma concentrations correlated well with removal measured by conductivity monitoring as ionic mass balance (R2 0.66, p < 0.0001). Of the 16 patients randomized to reduction of Cndi, 6 achieved Cndi 13.4 mS/cm, 6 achieved 13.2 mS/cm, and 4 achieved 13.0 mS/cm. No episodes of disequilibrium occurred. Interdialytic weight gain was reduced from 2.34 +/- 0.10 kg to 1.57 +/- 0.11 kg (p < 0.0001). Predialysis systolic blood pressure fell from 144 +/- 3 mm Hg to 137 +/- 4 mm Hg (p < 0.05). The reduction in convective sodium removal was balanced by an increase in diffusive sodium removal (95 +/- 9 mmol cf. 175 +/- 14 mmol, p < 0.0001). Reduction in Cndi monitored by IMB is safe and practical and leads to improved interdialytic weight gains and blood pressure control, while avoiding excessive sodium removal.

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.

Qualification of an electro-deionization module via experimental design and ion-chromatographic studies

To meet the needs of the laboratory-water market, a modified electro-deionization (EDI) module has been developed to produce Type 2 purified water. An EDI module consists of desalting and concentrating fluidic compartments that are both filled with anion and cation ion-exchange resins; an anode and a cathode electrode are at opposite ends. In the design in this research, the anode electrode is segmented into three parts and individual dc amperages are applied to each segment; the cathode electrode is a single common electrode. Critical to the performance and longevity of this type of EDI module are: (1) the optimization of the applied dc amperages and (2) the ionic mass balance (i.e., the concentrations of specific and total ions of the RO feedwater to the module compared to the concentrations in the water exiting the module via the desalting and concentrating compartments). To determine a suitable current for each electrode pair, a full-factorial experimental design was developed and employed. For the application of this combination of amperages, the critical parameter of specific-ion mass balance was determined using ion-chromatographic measurements.

Qualification of an electro-deionization module via experimental design and ion-chromatographic studies

To meet the needs of the laboratory-water market, a modified electro-deionization (EDI) module has been developed to produce Type 2 purified water. An EDI module consists of desalting and concentrating fluidic compartments that are both filled with anion and cation ion-exchange resins; an anode and a cathode electrode are at opposite ends. In the design in this research, the anode electrode is segmented into three parts and individual dc amperages are applied to each segment; the cathode electrode is a single common electrode. Critical to the performance and longevity of this type of EDI module are: (1) the optimization of the applied dc amperages and (2) the ionic mass balance (i.e., the concentrations of specific and total ions of the RO feedwater to the module compared to the concentrations in the water exiting the module via the desalting and concentrating compartments). To determine a suitable current for each electrode pair, a full-factorial experimental design was developed and employed. For the application of this combination of amperages, the critical parameter of specific-ion mass balance was determined using ion-chromatographic measurements.

Ionic mass balance and blood volume preservation during a high, standard, and individualized dialysate sodium concentration.

Although a higher dialysate sodium concentration (DNa) is frequently used to improve haemodynamic stability during haemodialysis, few studies have compared ionic mass balance (IMB) during different DNa. Moreover, DNa is usually a standard prescription, whereas inter-individual pre-dialytic serum sodium levels may differ widely. The aims of the study were to assess IMB and the decline in blood volume (DeltaBV) during isovolaemic HD as well as during HD combined with ultrafiltration (UF) during DNa [140], DNa [144], and an individualized DNa [ind], in which DNa is equal to pre-HD plasma conductivity x 10. IMB and plasma conductivity were assessed by on-line conductivity measurements (Diascan; Hospal) in 13 HD patients. After 1 h of isovolaemic HD, measurements were continued during UF+HD until dry weight. DeltaBV was assessed by an optical method (Hemoscan). During isovolaemic HD with DNa [140] and [144], Pre-Na was significantly related to IMB (r=0.83 and r=0.61; P<0.05). Diffusive Na flux into the patient occurred when the difference between DNa and pre-dialytic serum sodium was larger than 5 mmol/l. During UF+HD, IMB was 318+/-166 mmol during DNa [140], 277+/-116 mmol during DNa [ind], and 239+/-111 during DNa [144] (mean+/-SD; P<0.05 compared with the other treatment modalities) whereas DeltaBV did not differ significantly. In the five patients with a pre-dialytic sodium concentration below 140 mmol/l, ionic removal was significantly higher during DNa [ind] (324+/-87) compared with DNa [140] (228+/-127 mmol; P<0.05) without a significant difference in DeltaBV (-9.7+/-1.6 vs -7.8+/-2.3%). A large difference in IMB was observed between DNa 144 and DNa 140, without a significant difference in DeltaBV. In patients with low pre-dialytic serum sodium levels, diffusive ionic influx from the dialysate into the patient may occur. In patients with low pre-dialytic sodium levels, DNa [ind] leads to an enhanced ionic removal compared with DNa [140] without large differences in DeltaBV.

The kinetics of the dissolution of chalcocite in alkaline cyanide solution

A kinetic study of the dissolution of chalcocite in an alkaline cyanide solution indicates that the reaction is first order with respect to surface area and free cyanide ion concentration, and inversely proportional to the sulfide ion concentration to approximately the 0.1 power. The experimental rate constant is approximately 7.5 × 10−5 (mole Cu1+/ min) ([S−2]0.1/[CN1−]/cm2/l at 25°C. The activation energy of 2.5 kcal/mole indicates rate control by diffusion through a limiting boundary layer. The concentrations of the important ions in the cyanide solutions are obtained by solving the ionic equilibria and mass balance equations for the system.