Threshold pH Value Research Articles

Security-Enhanced 3D Data Encryption Using a Degradable pH-Responsive Hydrogel.

Based on degradable pH-responsive hydrogel, we report on an enhanced three-dimensional data encryption security technique in which a pH value is used for information manipulation. Featuring three types of states upon the pH value variation, namely, shrinkage, expansion and degradation, the hydrogel renders a limited pH value window as the “key” for information decryption. The pH-dependent shrinkage-to-expansion conversion of the hydrogel leads to a threshold pH value for retrieving the recorded data, whilst the degradability of the hydrogel, which can be tuned by adjusting the composition ratio of PEGDA/AAc, gives rise to a second threshold pH value for irreversibly sabotaging the retrieved data. Pre-doping silver ions in the hydrogel facilitates explicit recording and reading of binary data in forms of three-dimensional silver patterns through photoreduction and scattering, respectively, with a femtosecond laser. By accurately matching the vertical spacing of the encoded silver nanopatterns with the diffraction-limited focal depth of the decryption microscope, we can tune the pH value to encrypt and retrieve information recorded in layers and set a critical pH value to smash encoded information, which proves a highly secured 3D data encoding protocol. This strategy can effectively enrich data encryption techniques, vastly enhancing data security within unattained chemical dimensions.

The Impact of Plastic pH on Silicone Elastomer Compression Set

<div class="section abstract"><div class="htmlview paragraph">Sealing applications in electrified vehicle powertrains present a unique set of boundary conditions when contrasted with typical transmission or internal combustion engine applications, including changes in fluidic exposure, operating pressure, temperature profiles, etc. This novel powertrain environment opens the gasket material spectrum to elastomers uncommon in standard powertrain joints, which allows for more optimized, higher-value sealing solutions. However, this also introduces new risks, including the risk of excessive compression set in silicone elastomers due to acidity in adjacent plastics (which can result from shifting to non-halogenated flame retardants from halogenated flame retardants). To understand this phenomenon, compression set testing was conducted with plastic resins ranging from pH = 3.4 to pH = 7.3 and three high-consistency rubber (HCR) silicone elastomers. For each silicone, compression set was plotted linearly against concentration of hydrogen ions ([H+]) in the plastic and plotted exponentially against plastic pH. This produced a regression model relating compression set in the elastomer to acidity of the adjacent plastic. Then, a threshold pH value - after which the plastic begins to significantly increase compression set in the silicone - was determined by overlaying silicone-only compression set results with the silicone + plastic regression model. The resulting threshold value given the associated conditioning was a pH of 4.5 for all three silicone samples tested, indicating that a plastic resin accelerates compression set in the neighboring silicone if the plastic has a pH ≤ 4.5. Studies into the impact of (1) plastic sample form factor (raw material pellets, colorized material pellets, or molded plastic sheets) and (2) time on plastic pH were evaluated; both showed no statistical impact on pH measurements. Overall, this effect is believed to be due to acid-induced cleavage of the siloxane bond, which causes depolymerization in the silicone by breaking the backbone chain, thereby resulting in gasket compression set.</div></div>

Reconfigurable DNA Origami Nanocapsule for pH-Controlled Encapsulation and Display of Cargo.

DNA nanotechnology provides a toolbox for creating custom and precise nanostructures with nanometer-level accuracy. These nano-objects are often static by nature and serve as versatile templates for assembling various molecular components in a user-defined way. In addition to the static structures, the intrinsic programmability of DNA nanostructures allows the design of dynamic devices that can perform predefined tasks when triggered with external stimuli, such as drug delivery vehicles whose cargo display or release can be triggered with a specified physical or chemical cue in the biological environment. Here, we present a DNA origami nanocapsule that can be loaded with cargo and reversibly opened and closed by changing the pH of the surrounding solution. Moreover, the threshold pH value for opening/closing can be rationally designed. We characterize the reversible switching and a rapid opening of “pH-latch”-equipped nanocapsules using Förster resonance energy transfer. Furthermore, we demonstrate the full cycle of capsule loading, encapsulation, and displaying the payload using metal nanoparticles and functional enzymes as cargo mimics at physiologically relevant ion concentrations.

Stable and selective self-assembly of α-lipoic acid on Ge(001) for biomolecule immobilization

We demonstrate a novel method for the stable and selective surface functionalization of germanium (Ge) embedded in silicon dioxide. The Ge(001) surface is functionalized using α-lipoic acid (ALA), which can potentially be utilized for the immobilization of a wide range of biomolecules. We present a detailed pH-dependence study to establish the effect of the incubation pH value on the adsorption layer of the ALA molecules. A threshold pH value for functionalization is identified, dividing the examined pH range into two regions. Below a pH value of 7, the formation of a disordered ALA multilayer is observed, whereas a stable well-ordered ALA mono- to bi-layer on Ge(001) is achieved at higher pH values. Furthermore, we analyze the stability of the ALA layer under ambient conditions, revealing the most stable functionalized Ge(001) surface to effectively resist oxidation for up to one week. Our established functionalization method paves the way towards the successful immobilization of biomolecules in future Ge-based biosensors.

A coordinated sequence of distinct flagellar waveforms enables a sharp flagellar turn mediated by squid sperm pH-taxis

Animal spermatozoa navigate by sensing ambient chemicals to reach the site of fertilization. Generally, such chemicals derive from the female reproductive organs or cells. Exceptionally, squid spermatozoa mutually release and perceive carbon dioxide to form clusters after ejaculation. We previously identified the pH-taxis by which each spermatozoon can execute a sharp turn, but how flagellar dynamics enable this movement remains unknown. Here, we show that initiation of the turn motion requires a swim down a steep proton gradient (a theoretical estimation of ≥0.025 pH/s), crossing a threshold pH value of ~5.5. Time-resolved kinematic analysis revealed that the turn sequence results from the rhythmic exercise of two flagellar motions: a stereotypical flagellar ‘bent-cane’ shape followed by asymmetric wave propagation, which enables a sharp turn in the realm of low Reynolds numbers. This turning episode is terminated by an ‘overshoot’ trajectory that differs from either straight-line motility or turning. As with bidirectional pH-taxes in some bacteria, squid spermatozoa also showed repulsion from strong acid conditions with similar flagellar kinematics as in positive pH-taxis. These findings indicate that squid spermatozoa might have a unique reorientation mechanism, which could be dissimilar to that of classical egg-guided sperm chemotaxis in other marine invertebrates.

Solidification/stabilisation of electric arc furnace waste using low grade MgO

This study aims to evaluate the potential of low grade MgO (LGMgO) for the stabilisation/solidification (S/S) of heavy metals in steel electric arc furnace wastes. Relevant characteristics such as setting time, unconfined compressive strength (UCS) and leaching behaviour assessed by acid neutralisation capacity (ANC), monolithic and granular leaching tests were examined in light of the UK landfill Waste Acceptance Criteria (WAC) for disposal. The results demonstrated that all studied mix designs with Portland cement type 1 (CEM1) and LGMgO, CEM1–LGMgO 1:2 and 1:4 at 40% and 70% waste addition met the WAC requirements by means of UCS, initial and final setting times and consistence. Most of the ANC results met the WAC limits where the threshold pH values without acid additions were stable and between 11.9 and 12.2 at 28d.Granular leaching results indicate fixation of most of the metals at all mix ratios. An optimum ratio was obtained at CEM1–LGMgO 1:4 at 40% waste additions where none of the metals leaching exceeded the WAC limits and hence may be considered for landfill disposal.The monolithic leaching test results showed that LGMgO performed satisfactorily with respect to S/S of Zn, as the metal component present at the highest concentration level in the waste exhibited very little leaching and passed the leaching test requirement at all mix ratios studied. However, its performance with respect to Pb, Cd and Cr was less effective in reducing their leaching suggesting a higher cumulative rate under those leaching regimes.

Increasing Reflux Study Duration Progressively Improves Diagnostic Consistency: A Prospective Study With 96hr Wireless pH Recordings

Introduction Previous studies suggest that prolonged ambulatory reflux monitoring can improve measurement consistency; however, previous reports were not analysed appropriately or adequately powered to determine the impact on key clinical parameters. The aim of this study was to assess measurement consistency for acid exposure time (AET) and symptom association with reflux events used to establish the diagnosis of GORD. Methods Acid reflux (pH) and symptom data were acquired by prolonged, 4 day, wireless pH recording (Bravo, Given Imaging). 163 consecutive patients presenting with predominantly typical reflux symptoms (heartburn, regurgitation) studied 2006–2009 with a record duration of >3.7 days were studied (636 days). Data were exported in XML format, redundant symptom markers were removed in one pass with reflux detection. A cross-validation procedure assessed measurement variability (standard deviation (SD)) and diagnostic consistency of AET, symptom index (SI) and symptom association probability (SAP). The 4-day records were divided into 1-day sections and re-assembled as all possible subsets. Index parameters were computed for all subsets and labelled with a sequence identifier in the database. Bias due to self-referential comparisons was excluded (i.e., day 1 was not compared with day 123) and, also, no comparisons with 4-day results are given. Standard diagnostic thresholds were applied. In addition, the effect of varying threshold pH value used for reflux detection on diagnostic consistency was assessed. Results Measurement variability: There was no change in AET or SI over time; however, SAP increased progressively with study duration. Standard deviation (SD) was higher for 1-day than 3-day records for AET (+50% (confidence interval (CI): 10%…120%)) and SI (+100% (CI 120%…270%)) with no important difference across the observed range. Results for 2 days were intermediate. Similar findings were present for SAP (1 day vs 3 days at 95% SAP (+100% (CI 10%…700%); however, for this parameter measurement variability increased exponentially as SAP approached 100%. Diagnosis: Consistency for GORD diagnosis increased with study duration (table 1) for all parameters studied. Conclusion Increasing the duration of reflux studies progressively improves diagnostic consistency for GORD based on both AET and reflux-symptom association analysis independent of diagnostic threshold applied.

Increasing reflux study duration progressively improves diagnostic consistency: a prospective study with 96 h wireless pH recordings

<h3>Introduction</h3> Previous studies suggest that prolonged ambulatory reflux monitoring can improve measurement consistency; however, previous reports were not analysed appropriately or adequately powered to determine the impact on key clinical parameters. The aim of this study was to assess measurement consistency for acid exposure time (AET) and symptom association with reflux events used to establish the diagnosis of GORD. <h3>Methods</h3> Acid reflux (pH) and symptom data were acquired by prolonged, 4 day, wireless pH recording (Bravo, Given Imaging). 163 consecutive patients presenting with predominantly typical reflux symptoms (heartburn, regurgitation) studied 2006–2009 with a record duration of &gt;3.7 days were studied (636 days). Data were exported in XML format, redundant symptom markers were removed in one pass with reflux detection. A cross-validation procedure assessed measurement variability (standard deviation (SD)) and diagnostic consistency of AET, symptom index (SI) and symptom association probability (SAP). The 4-day records were divided into 1-day sections and re-assembled as all possible subsets. Index parameters were computed for all subsets and labelled with a sequence identifier in the database. Bias due to self-referential comparisons was excluded (i.e., day 1 was not compared with day 123) and, also, no comparisons with 4-day results are given. Standard diagnostic thresholds were applied. In addition, the effect of varying threshold pH value used for reflux detection on diagnostic consistency was assessed. <h3>Results</h3> Measurement variability: There was no change in AET or SI over time; however, SAP increased progressively with study duration. Standard deviation (SD) was higher for 1-day than 3-day records for AET (+50% (confidence interval (CI): 10%…120%)) and SI (+100% (CI 120%…270%)) with no important difference across the observed range. Results for 2 days were intermediate. Similar findings were present for SAP (1 day vs 3 days at 95% SAP (+100% (CI 10%…700%); however, for this parameter measurement variability increased exponentially as SAP approached 100%. Diagnosis: Consistency for GORD diagnosis increased with study duration (table 1) for all parameters studied. <h3>Conclusion</h3> Increasing the duration of reflux studies progressively improves diagnostic consistency for GORD based on both AET and reflux-symptom association analysis independent of diagnostic threshold applied.

Was ist ein „pathologisches” CTG ?

Sub partu foetal heart-rate (FHR) patterns are difficult to evaluate. Until now we have no numerical criteria to reliably define what is a non-reassuring or even a 'pathological' FHR tracing. Computer-aided FHR analysis using the new WAS score offers the unique opportunity to assess numerical boundaries for these definitions. Direct FHR tracings of 475 foetuses, all delivered by the vaginal route, were recorded electronically and the last 30 min of each tracing were used for computation of the WAS score. The WAS score refers to FHR frequency, microfluctuation, and oscillation amplitude per minute. Acid-base and blood-gas analyses were performed in blood of the umbilical artery (UA) and vein (UV) immediately post partum. pH (UA) and the WAS score were correlated (r) and the 4 variables sensitivity, specificity, the false positive rate (FPR) and the false negative rate (FNR) were determined. ROC plots for different threshold pH (UA) values were performed. pH (UA) and the WAS score are normally distributed: mean pH (UA)=7.263+/-0.064 and mean WAS score 2.78+/-0.81, respectively. The correlation coefficient, r amounts to 0.657, P<<10(-4). Using the mean pH (UA) and the mean WAS score leads to a sensitivity and specificity both of 72% with an FPR and FNR both of 28%. Using a WAS score of 1.816 and the threshold pH (UA) of 7.122 sensitivity becomes the first time 100% (FNR=0%) and FPR decreases to 10.7%. These 2 values are chosen to separate a normal (score >1.816) from an abnormal (non-reassuring) CTG (score < or =1.816). According to this definition newborns with a reassuring (normal) FHR tracing (N=417) have a pH (UA)=7.275+/-0.055, pCO (2)=52.3+/-7.9, BE (Ecf,oxy.)=-3.0+/-2.3, sO (2)=24.9+/-12.3 with an acidotic risk (pH (UA) <7.100) of 0% and APGAR 1 min <7=0.96%, respectively. Neonates with an abnormal (non-reassuring) FHR tracing (N=58) present a mean pH (UA)=7.178+/-0.066, pCO (2)=62.6+/-9.6, BE (Ecf,oxy.)=-5.4+/-2.6, sO (2)=18.3+/-12.0 and an acidotic risk of 6.9%. No neonate in this group was severely depressed (APGAR 1 min < or =3). Separation of the true positive (pH (UA) <7.122) from the false positive (pH (UA) > or =7.122) cases yields 10 babies with a mean pH (UA)=7.084+/-0.053, pCO (2)=71.8+/-10.7, BE (Ecf,oxy.)=-8.4+/-2.0, sO (2)=20.2+/-14.5 and an acidotic risk of 44.4%; in this group also not one baby was severely depressed (APGAR 1 min < or =3) but 3 were already moderately affected (<7 after 1 min). No infant scored <7 after 5 min. There must be a lower limit for the definition of a true 'pathological' FHR tracing; this boundary should not be identical with the threshold pH value where hypoxic injuries in term infants usually commence. For FHF this is a WAS score of 0.630 and a threshold pH (UA) of 7.075. Using sensitivity, specificity, FPR and FNR of the FHR sub partu, it is possible to discriminate online a normal (reassuring) from an abnormal (non-reassuring) FHR tracing by a simple computer-aided procedure which we call WAS scoring.

A proton-activated, outwardly rectifying chloride channel in human umbilical vein endothelial cells

Extracellular acidic pH-activated chloride channel I Cl, acid, has been characterized in HEK 293 cells and mammalian cardiac myocytes. This study was designed to characterize I Cl,acid in human umbilical vein endothelial cells(HUVECs). The activation and deactivation of the current rapidly and repeatedly follows the change of the extracellular solution at pH 4.3, with the threshold pH 5.3. In addition, at very positive potentials, the current displays a time-dependent facilitation. pH-response relationship for I Cl,acid revealed that EC 50 is pH 4.764 with a threshold pH value of pH 5.3 and nH of 14.545. The current can be blocked by the Cl − channel inhibitor DIDS (100 μM). In summary, for the first time we report the presence of proton-activated, outwardly rectifying chloride channel in HUVECs. Because an acidic environment can develop in local myocardium under pathological conditions such as myocardial ischemia, I Cl,acid would play a role in regulation of EC function under these pathological conditions.

Exposure assessment of a burning ground for chemical ammunition on the Great War battlefields of Verdun

The destruction of arsenical shells from the 1914/18 war in the vicinity of Verdun (France) during the 1920s resulted in a locally limited but severe soil contamination by arsenic and heavy metals. At the study site, the main part of the contaminant inventory occurs in the upper 20 cm of the topsoil which is essentially composed of combustion residues. Besides, some Cu (cmax.=16,877 mg/kg) and Pb (cmax.=26,398 mg/kg) in this layer, As (cmax.=175,907 mg/kg) and Zn (cmax.=133,237 mg/kg) were detected in very high concentrations. The mobilities of Cu, Mn, Pb and Zn in the soil system were derived from ammonium nitrate eluates. They are strongly influenced by the soil pH and can be described by quadratic regression curves from which threshold pH values were calculated. Below these values more than 10% of the element content was available as mobile species. Within the examined pH range, this method could not be adopted for arsenic, because the mobility of As was only slightly controlled by the soil pH. In the heavily contaminated topsoil, Cu and Pb were fixed by the moderately acidic soil pH which varied from 4.8 to 5.8. No migration to the underlying horizons occurred. A different behavior was observed for As and Zn. The calculated threshold pH of Zn was 5.5, so certain amount of this element was transferred to the subsoil and the leachate (cmax.=350 microg/l). However, a major dispersion of Zn was prevented by a rise of the soil pH in the carbonate-containing subsoil. Elevated concentrations of As were found in all soil horizons up to a depth of 2 m and also in the leachate (cmax.=2377 microg/l). Contrary to Cu, Pb and Zn the mobility of As evidently was less affected by the subsoil. Regarding organic contaminants, nitroaromatic explosives were detected only in minor concentrations in the soil (cmax.=14.7 mg/kg) and the leachate (cmax.=13.5 microg/l). No aromatic organoarsenicals were detected in the soil and the leachate samples. The main hazard of the site is the severe arsenic contamination and the transfer of this carcinogen by leachate, surface runoff and probably by wind. Nevertheless, some studies on the effects of the contaminant inventory on the local vegetation revealed that ammonium nitrate elutable zinc is responsible for the spatial distribution of some tolerant plant species and not arsenic. Previously undetected buried munitions from the former delaboration facility can be an other source of environmental contaminants. This is supported by elevated concentrations of chlorate (cmax.=71 mg/l) and perchlorate (cmax.=0.8 mg/l) detected in the leachate samples. This is the second report about environmental contamination related to post-war ammunition destruction activities along the 1914/18 Western Front.

Influence of solution acidity and CaCl 2 concentration on the removal of heavy metals from metal-contaminated rice soils

Soil washing is considered a useful technique for remediating metal-contaminated soils. This study examined the release edges of Cd, Zn, Ni, Cr, Cu or Pb in two contaminated rice soils from central Taiwan. The concentrations exceeding the trigger levels established by the regulatory agency of Taiwan were Cu, Zn, Ni and Cr for the Ho-Mei soil and Pb for the Nan-Tou soil. Successive extractions with HCl ranging from 0 to 0.2 M showed increased release of the heavy metals with declining pH, and the threshold pH value below which a sharp increase in the releases of the heavy metals was highest for Cd, Zn, and Ni (pH 4.6 to 4.9), intermediate for Pb and Cu (3.1 to 3.8) and lowest for Fe (2.1), Al (2.2) and Cr (1.7) for the soils. The low response slope of Ni and Cr particularly for the rice soils make soil washing with the acid up to the highest concentration used ineffective to reduce their concentrations to below trigger levels. Although soil washing with 0.1 M HCl was moderately effective in reducing Cu, Pb, Zn and Cd, which brought pH of the soils to 1.1 ± 0.1 (S.D.), the concurrent release of large quantities of Fe and Al make this remediation technique undesirable for the rice soils containing high clay. Successive washings with 0.01 M HCl could be considered an alternative as the dissolution of Fe and Al was minimal, and between 46 to 64% of Cd, Zn, and Cu for the Ho-Mei soil and 45% of Pb in the Na-Tou soil were extracted after four successive extractions with this dilute acid solution. The efficacy of Cd extraction improved if CaCl 2 was added to the acid solution. The correlation analysis revealed that Cr extracted was highly correlated ( P < 0.001) with Fe extracted, whereas the Cu, Ni, Zn, Cd or Pb extracted was better correlated ( P < 0.001) with Al than with Fe extracted. It is possible that the past seasonal soil flooding and drainage in the soils for rice production was conducive to incorporating Cr within the structure of Fe oxide, thereby making them extremely insoluble even in 0.2 M HCl solution. The formation of solid solution of Ni with Al oxide was also possible, making it far less extractable than Cd, Zn, Cu, or Pb with the acid concentrations used.

Slimline™ vs Glass

Purpose: This study compared the pH recording accuracy of the Slimline™ antimony pH monitoring system and a conventional glass electrode catheter pH monitoring system during ambulatory conditions. Methods: 18 asymptomatic subjects (13 males, 23–45 y/o) underwent simultaneous pH monitoring using the Slimline™ antimony pH electrode and MIC M3 glass pH electrode pH monitoring systems for 12 hours. The catheters were attached with tape and placed 5 cm above the LES. The subjects consumed 100 cc of orange juice and 100 cc of cranberry juice at 37°C to synchronize the data and measure pH electrode accuracy. After 11 hours the subjects returned to the lab and the catheter was advanced 10cm into the stomach for1 hour. Differences in% time the pH < 4 and number of reflux events were analyzed and compared by manual extraction of the data onto an excel spreadsheet. Agreement between the two systems in recording reflux events was analyzed by observing the point-by point discrepancy of + 0.5 pH units and also by performing a Kappa analysis for pH above and below 4. Results: The correlation between Slimline™ and the Glass MIC M3 catheter was excellent for the total% time pH < 4 (r = 0.84) and there was no statistical difference in the median value measured by the two systems (Slimline™, 2.5%, Glass 1.9%, P = 0.77). The difference in recorded reflux events was also not significantly different between the two systems, with the absolute difference being 23 events (SD, 26.0). Although the point-by-point discrepancy was 28.2% (SD, 17.5%) when using a 0.5pH unit threshold, the agreement in terms of pH events above and below 4 was excellent (Kappa value, 0.89, SD, 0.09). In addition, the in-vivo pH measurement identified two Slimline™ catheters and one glass catheter that were malfunctioning. Conclusions: The antimony Slimline™ pH catheter compares favorably to the Glass MIC M3 pH catheter in terms of measuring standard pH parameters. Although there is substantial point-by-point disagreement, it is typically less than 0.5 pH units and does not substantially alter diagnosis based on a threshold pH value of 4.

Alteration of the growth rate and lag time ofLeuconostoc mesenteroides NRRL-B523

Bacterial profile modification is an important enhanced oil recovery technique used to direct injected water into a reservoir's low permeability zone containing trapped crude oil. During water flooding, the use of bacteria to plug the high permeability water zone and divert flow into the oil-bearing low-permeability zone will have a significant economic impact. However, during the field implementation of bacterial profile modification, the rapid growth of bacteria near the injection well bore may hinder the subsequent injection of growth media so that profile modification of the reservoir occurs only in the immediate vicinity of the well bore. By slowing the growth rate and prolonging the lag phase, the onset of pore-space plugging may be delayed and the biologically active zone extended deep into the reservoir. High substrate loading, high pH values, and the addition of the growth inhibitors sodium dodecylsulfate and sodium benzoate have been used in combination to alter the growth characteristics of Leuconostoc mesenteroides NRRL-B523 grown in batch conditions. The highest sucrose concentration used in these studies, 500 g/L, produced lag times 12-fold greater than the slowest lag times achieved at low sucrose concentrations. When L. mesenteroides was grown in media containing 500 g/L sucrose, an alkaline pH value threshold was found above which bacteria did not grow. At this threshold pH value of 8.1, an average lag time of 200 h was observed. Increasing the concentration of sodium benzoate had no effect on lag time, but reduced the growth rate until the threshold concentration of 0.6%, above which bacteria did not grow. Last, it was found that a solution of 0.075 mM sodium dodecylsulfate in media containing 15 g/L sucrose completely inhibited bacterial growth.

Root system responses of Japanese red cedar saplings to acidic conditions

Stemflow from Japanese red cedar ( Cryptomeria japonica) enters forest soil at a low pH. We evaluated the responses of the root system of Japanese red cedar saplings to acidic conditions, used to simulate this situation, in two different growth media, a brown forest soil (BS) and a Yahagi sand (YS). Soils were acidified by the addition of solutions at pH 2.0, 3.0 and 5.5 (control). Root morphology, root surface area index, root respiration activity and root biomass were measured. In the pH 3.0 treatment, no significant effects were found on the root systems compared with the controls in either soil, except for a slight difference in root-tip diameter in the Yahagi sand. In the pH 2.0 treatment, the surface area index and dry weight ratios of the whole root in the Yahagi sand were significantly lower than those in the other treatments. No significant effects on the whole root were observed in the brown forest soil. These results suggest that detrimental effects of acidic solutions on the root systems would be less significant in brown forest soil, which contains humus, than in the Yahagi sand, which lacks humus. They also suggest that the threshold pH value causing visible morphological changes on the roots of Japanese red cedar saplings falls in the pH range between 2 and 3. White roots in the pH 2.0 treatment had low respiration activity and showed visible morphological changes in both soils. These responses were presumably related to the effects of excess Al in the soil solution. White roots in the pH 2.0 treatment typically produced exodermis. The results suggest that stemflow with a pH of 3.0 has no effects on the root systems of Japanese red cedar, and that the morphology of white roots was adversely affected not by treatment at pH 2.0 but by excess water-soluble Al in the soil.

Total and exchangeable concentrations of heavy metals in soils near Bytom, an area of Pb/Zn mining and smelting in Upper Silesia, Poland

High concentrations of several heavy metals were suspected in soils in an area of some contemporary and extensive historical mining and smelting of Pb and Zn near the town of Bytom. In order to investigate the spatial distribution of heavy metals, 152 soil samples were taken at high sampling density in an area of 14 km 2 on a regular grid as well as along an 11 km transect. The samples were analysed for total Pb, Zn and Cd content by ICP-AES; a selection of samples were also analysed for total As content. Significant levels of contamination were found. Median topsoil concentrations (0–10 cm) for Pb, Cd, Zn and As were 430 μg g −1, 13 μg g −1, 1245 μg g −1 and 35 μg g −1, respectively. The detected levels of Pb, Zn and Cd were mostly in reasonable agreement with findings from a previous low-density study, but As concentrations were up to 6 times higher than had previously been reported for the area. Additional zones of particularly high concentrations could be identified for all 4 elements by this higher-density survey. Contaminant concentrations were generally found to decrease substantially with increasing depth, on average by a factor of 3.5 for Cd, 3.0 for Zn and 2.6 for Pb. However, significant subsoil contamination (40–50 cm) was also detected, in particular for Zn, Pb and As, which appeared to be enriched at depth in certain locations. To assess the potential availability of the metals to plants, the exchangeable fraction (0.5 M MgCl 2) was estimated for Pb, Zn and Cd for 84 samples. Levels were strongly influenced by soil pH and were generally low for Pb (less than 1% of total, max 15.6%), moderate for Zn (less than 10% of total, max 32.4%), and high for Cd (mean 35% of total, max 59.8%). For Zn and Pb, there seemed to be a threshold pH value of about 6, below which a significant increase in the exchangeable fraction was observed. No such threshold value appeared to exist for Cd, which was found to be relatively labile even in slightly alkaline soils (mean of 27.6% exchangeable Cd in pH range 7–8). The detected levels of total metal contamination exceed various national and international thresholds, indicating the need for further investigation and an assessment of the suitability of the land for agricultural use, particularly in view of the high levels of exchangeable Cd.The pattern of spatial variation of the metals in the topsoil indicates that a variety of sources might be responsible for the contamination, historical mining and smelting probably being the most important.

Lethal and sublethal threshold values of aluminium and acidity to pike ( Esox lucius), whitefish ( Coregonus lavaretus pallasi), pike perch ( Stizostedion lucioperca) and roach ( Rutilus rutilus) yolk-sac fry

The newly-hatched fry of four fish species were exposed for 10 days in semistatic tests at pH values of 4.00–6.00 to AI at nominal concentrations of 0–800 μg 1 −1. Test waters were made in lake water (Ca 0.11 mmol 1 −1 by adding H 2SO 4 and Al 2(SO 4) 3. Based on the observations on mortality (LC 50) and swimming activity (EC 50), the four species had the following ranking for their sensitivity to acidity and Al: roach > pike perch > whitefish > pike. At the end of the 10-day test the LC 50 and EC 50 values of Al were identical for the most sensitive species, roach, whereas those for pike and whitefish were significantly different at that time. Al and low pH clearly retarded pike and roach yolk-sac fry growth, which was coincident with a slower absorption of the yolk. Al decreased pike growth at pH values ≤ 5.25 and roach growth even at pH 5.75. In whitefish, which have a small yolk sac; the effects of pH and Al on growth were not so clear. In general, the more Al the water contained, the more toxic was the acidic water. The threshold pH values (lowest pH for survival and safe pH) for the four species were, depending on the Al concentration: pike 4.0–5.3 whitefish 4.5–5.5 pike perch 4.8–5.8 and roach 5.0–6.0.

The effects of pH and soil type on concentrations of zinc, copper and nickel extracted by calcium chloride from sewage sludge-treated soils

The effects of pH on concentrations of zinc, copper and nickel extracted by calcium chloride from a clay loam and two sandy loam soils that had been treated with sewage sludge were studied. Concentrations of all the metals increased rapidly as pH decreased below a threshold value ranging from 6·2 to 7·0 for Zn, 6·2 to 7·2 for Ni and 4·7 to 5·7 for Cu. Both the total concentrations and the threshold pH values were influenced by differences in soil texture and (between the two light-textured soils) by differences in soil cation exchange capacity. The amount of zinc and copper extracted from the mixtures was considerably less than that extracted from the same quantity of sludge alone.

Simulated mobilization of metals from sediments in response to lake acidification

The regeneratable forms of pollutant metals in lake sediments were estimated using different chemical extractants and the effects of lake acidification on the mobilization of such metal fractions studied in laboratory microcosm. The release of each metal was found to increase exponentially below a threshold pH value, which was about 4.0 for Cu, Ni, Zn, Cd and Fe. The data suggest that a large percentage of pollutant metals are mobile as determined by chemical extraction techniques and long-term release experiments.

The relationship of soil ph to aluminum saturation and exchangeable aluminum in ultisols and oxisols

Abstract For soil acidity assessment purposes, the relationship of either percent Al saturation or exchangeable Al to water pH is often misleading for tropical soils. Published data from studies using Ultisols and Oxisols were used to determine whether relationships between Al saturation or exchangeable Al and pH in 1M KCl and pHo are better criteria to assess soil acidity for these variable charge soils. For Ultisols, a highly significant negative relationship (R2 =0.76∗∗) was found between Al saturation and pH in 1M KCl. For Oxisols, soil acidity assessment appears to be better expressed in terms of actual exchangeable Al rather than Al saturation per se. Exchangeable Al correlated best with pHo (R2 = 0.78∗∗). From a practical standpoint, Oxisols with pHo values higher than 4.0 should not contain exchangeable Al which could be detrimental to plant growth. For Ultisols, a threshold pH value in 1M KCl higher than 4.0 should indicate an Al saturation less than 15%. The above relationships appear to take in...