Cation Depletion Research Articles

Bioactivity of 1.25CaO · SiO 2 glass: an FTIR and X-ray study on powdered samples

Powdered samples (170–230 mesh) of a glass of composition 1.25CaO · SiO 2 were soaked in a simulated body fluid (SBF). The powders were submitted to Fourier transform infrared transmission spectroscopy as coarse powders (such as drawn out from the SBF) and as fine powders (soaked and subsequently ground). Soaked samples were submitted to differential thermal analysis (DTA) and the crystalline phases formed during heating in the DTA apparatus were identified by means of X-ray diffraction analysis. The method appears to be useful in studying the mechanism of deposition of the hydroxyapatite layer. It is documented, by using the same method, that the mechanism involves the reactions of hydrolysis and successive condensation and repolymerization of the silicate substrate. These reactions are very fast. Extensive Ca 2+ cation depletion occurs, but appears to be slower.

Application of the model fiwald to the Solling spruce site

The physiological model of Norway spruce even-aged stands, fiwald, was applied to the Solling F1 spruce site, based on the data and the scenarios supplied by the Workshop on Comparison of Forest-Soil-Atmosphere Models, Leusden. Several simulation experiments were conducted, including simulation of the development of the F1 stand for the last two decades and analysis of effects of atmospheric deposition, water and nutrient stress. The results emphasize the impact of deposition-driven base cation depletion in mineral soil on tree nutrition. Additionally, a N shortage can be detected. However, the simulations show that stand productivity and growth are mainly limited by base cation deficiency. In the case of N fertilizing the productivity is increased in the first years, but decreases significantly afterwards due to pronounced Mg deficiency and needle loss. The reason for the more prominent Mg deficiency under N fertilizing is the accelerated consumption of the soil Mg resources by the biomass growth. Water stress has, even in drought years, only limited impact on gas exchange and stand growth. In the ‘business as usual’ scenario the stand is able to survive, but the needles show Mg deficiency, the productivity is decreased and the trees are susceptible to changes in the deposition regime. In the ‘improved environment’ scenario the amount of available base cation nutrients increases slowly by supply from silicate weathering and deposition, the nutrient deficiency disappears, and the productivity finally reaches the level of the seventies, though the stand is much older.

Base Cation Depletion and Potential Long-Term Acidification of Norwegian Catchments

Long-term monitoring data from Norwegian catchments show that since the late 1970's, sulfate deposition and runoff sulfate concentrations have declined significantly. However, water quality has not significantly improved, because reductions in runoff sulfate have been matched by equal declines in calcium and magnesium concentrations. Long-term declines in runoff Ca and Mg are most pronounced at catchments subject to highly acidic deposition ; the observed rates of decline are quantitatively consistent with depletion of exchangeable bases by accelerated leaching under high acid loading. Even though water quality has not recovered, reductions in acid deposition have been valuable because they have prevented significant acidification that would otherwise have occurred under constant acid deposition. Ongoing depletion of exchangeable bases from these catchments implies that continued deposition reductions will be needed to avoid further acidification and that recovery from acidification will be slow.

Are ion exchange processes important in controlling the cation chemistry of soil- and runoff waters ?

Soil- and stream water elemental concentrations from a subcatchment in the Lake Gardsjon area have been used to evaluate the importance of ion exchange processes on the transport of cations to aquatic ecosystems. The importance of cation exchange processes in the upper organic and upper B soil horizons was demonstrated using lysimeter water data from a recharge area and soil water flow simulated with SOIL model during winter rain events with high sea-salt concentration. The importance of the hydrological conditions, such as water flow and water pathway, silicate weathering and the ion exchange of Al with H+ on the streambed materials in controlling cation concentrations in soil and stream waters are also discussed. With the SAFE model, the contribution of cations from ion exchange by depletion of base cations from the exchange matrixes compared to from weathering was also assessed. SAFE calculations indicate that the release rate of base cation by ion exchange to runoff water has decreased since 1945 and is very low, approx. 0.1 keq/ha per year, at present time as a result of soil acidification due to S and N inputs.

Modelling geochemistry and Lake pH since glaciation at Lake G�rdsj�n

The soil acidification model SAFE was modified to calculate historical changes in geochemistry and runoff since the last glaciation ended at the Lake Gardsjon F1 catchment 12 000 B.P. Changes in runoff pH and ANC, soil weathering rate, soil mineralogy, soil texture and base saturation was also calculated. The changes in mineralogy compared favorable to data. Modeled historic weathering rates were slightly higher than data suggest, while present weathering rate was somewhat to low, 37 mmolc m–2 yr–1. The weathering rate was very high immediately after the last glaciation, and decreased as the smaller particles were consumed by weathering. The calculated runoff pH follows the pattern of the paleo-inferred pH. SAFE suggests a natural depletion of base cations in the C-layer. (Less)

Can forest-soil liming mitigate acidification of surface waters in Sweden?

Acidification of surface waters and forest soils is severe in large parts of southern Sweden. The shallow groundwaters are also affected. Large scale liming of surface waters and streams is in operation, often combined with wetland liming to limit the effects of acid episodes, e.g. at snow melt. Acid episodes are perhaps the most severe problem in limed surface waters and in many as yet well buffered waters, because of temperature-layered acid inflow, often superficial. As a result of some investigations, a large scale forest liming programme covering 6.500–10.000 km2 was recently suggested. The main objectives of this forest liming programme are to retard cation depletion and to prevent nutrient imbalance and forest decline in acidified areas. This paper deals with the effects of forest soil liming on streams and surface waters. The response of water chemistry is very dependent on hydrological and soil properties. Although pH itself may be little affected by liming, the acidity (or negative ANC) decreases, inorganic Al-species decrease and the Al/BC-ratio increases in the runoff water. Especially interesting is that this is also true during acid episodes. This means that toxicity for acid sensitive biota decreases. These results indicate that large scale liming may have beneficial effects on surface water chemistry. Furthermore, as surface waters are expected to respond to smaller decreases in acid deposition than do forests soils, forest soil liming may allow less frequent liming of lakes. Consequently, forest soil liming in combination with the anticipated emission reductions may have very beneficial results on surface waters in certain areas of Sweden.

Relation between soil age and silicate weathering rates determined from the chemical evolution of a glacial chronosequence

Long-term weathering rates ( RLT ) were determined from base cation depletion in soil profiles developed on six granitic glacial moraines varying in age from 0.4 to ≥297 ka in the Wind River Mountains, Wyoming. Weathering rates were found to decrease with soil age ( t ) according to the power-law equation RLT = 15 ċ t (−0.71) where RLT is in meq ċ m −2 ċ yr −1, and t is in ka. Comparable data from the literature are consistent with this function, and it is similar to power-law equations describing changes in laboratory weathering rates with time. On the basis of our study, we predict that for a catchment unaffected by anthropogenic inputs and in a steady state with respect to the organic and cation exchange pools, RLT should be higher than present-day weathering rates derived from stream fluxes ( RPD ) by a factor of about 3.4.

Depletion of manganese within the secretory pathway inhibits O-linked glycosylation in mammalian cells.

Proteins transiting the secretory pathway are posttranslationally modified by addition of oligosaccharides to asparagine N-linked and serine and threonine O-linked residues. The effects of divalent cation depletion on oligosaccharide processing of erythropoietin (EPO) and macrophage colony stimulating factor (M-CSF) were studied in Chinese hamster ovary cells. Treatment with A23187 did not inhibit M-CSF or EPO secretion but did inhibit addition of complex N-linked and O-linked oligosaccharides to both molecules. Similar results were obtained by treatment with thapsigargin, a potent inhibitor of the Ca(2+)-activated microsomal ATPase, indicating that the effect was due to depletion of divalent cations within the secretory pathway. Whereas addition of extracellular calcium chloride did not reverse the inhibition in complex N-linked and O-linked glycosylation, addition of manganese chloride partially reversed both defects. These results are consistent with a specific manganese requirement within the secretory pathway for the processing of complex N-linked oligosaccharides and the addition of O-linked oligosaccharides. Since there are no known specific inhibitors of O-linked glycosylation, the use of ionophores should significantly facilitate studies on the requirement and role of O-linked oligosaccharides in protein structure and function.

Magnesium deficiency in Douglas-fir and Grand fir growing on a sandy outwash soil amended with sewage sludge

Soil and plant samples were collected from chlorotic plantations of Grand fir (Abies grandis) and Douglas-fir (Pseudotsuga menziesii) in Winter, 1989. The soils had been amended in 1981 with an average of 300 dry Mg ha−1 of municipal sewage sludge. The sludge amendment resulted in an N application rate of approximately 8000 kg ha−1. Foliage analysis indicated a severe Mg deficiency (0.25 g kg−1 in sludge-treated vs. 0.93 g kg−1 in untreated area) might be the cause of chlorosis. No other nutrient showed concentrations in the deficient or toxic ranges. Trace metal levels in foliage were elevated significantly for Ni, Cd and Cr in sludge-treated sites, but not toxic levels. Soil samples taken to a depth of 1.4 m indicated the potential for soil acidification (up to 0.9 pH unit) in soil surface horizons. In addition, exchangeable Ca, Mg and K may have been depleted in surface horizons. Exchangeable Al and Fe were greater in the surface of sludge-treated sites. These observations and the loss of much of the nitrogen added during the sludge amendment indicated that nitrification and cation leaching was likely the mechanism for acidification and depletion of exchangeable cations. Fertilization of the plantation with MgSO4 or dolomitic limestone was carried out in Spring 1990. New foliage collected in June, 1990 was non-chlorotic and significantly higher in Mg concentration than unfertilized foliage (1.1. vs. 0.7 g kg−1, respectively). Results of this study indicate that it is important to assess the potential for initiating a nutrient deficiency due to secondary effects of sludge application in forest systems.

Evidence for three different electrophoretic pathways in yeast mitochondria: Ion specificity and inhibitor sensitivity

We identified three electrophoretic pathways by spectrophotometrically following the swelling of isolated yeast mitochondria: An anion uniport whose activity could only be detected after depletion of divalent cations from the matrix by treatment with 1,10-phenanthroline. This uniport was inhibited by Mg2+ and dicyclohexylcarbodiimide. A K+ (Na+) uniport which was detected only when mitochondria were suspended at low pH and low temperature. This uniport was sensitive to ruthenium red and oleic acid. A K+ selective uniport which was activated by alkaline pH and ATP depletion. This pathway was sensitive to glibenclamide and to various amphiphilic cations. Similarities and differences between these three electrophoretic pathways and the electrophoretic systems described in mammalian and plant mitochondria are discussed.

On the regulation of Na +/H + and K +/H + antiport in yeast mitochondria: Evidence for the absence of an Na +-selective Na +/H + antiporter

Unlike mammalian mitochondria, yeast mitochondria swell spontaneously in both NaOAc and KOAc. This swelling reflects the activity of an electroneutral cation/H + antiport pathway. Transport of neither salt is stimulated by depletion of endogenous divalent cations; however, it can be inhibited by addition of exogenous divalent cations (Mg 2+ IC 50 = 2.08 mM, Ca 2+ IC 50 = 0.82 mM). Transport of both Na + and K + can be completely inhibited by the amphiphilic amines propranolol (IC 50 = 71 μM) and quinine (IC 50 = 199 μM) with indistinguishable IC 50 values. Dicyclohexylcarbodiimide inhibits with a second-order rate constant of 1.6·10 −4 (nmol DCCD/mg) −1 min −1 at 0°C; however, with both Na + and K + inhibition reaches a maximum of about 46%. The remaining transport can still be inhibited by propranolol. Transport of both cations is sensitive to pH; yielding linear Hill plots and Dixon plots with a pIC 50 value of 7.7 for both Na + and K +. These properties are qualitatively the same as those of the non-selective K +/H + antiporter of mammalian mitochondria. However, the remarkable similarity between the data obtained in Na + and K + media suggests that an antiporter akin to the Na +-selective Na +/H + antiporter of mammalian mitochondria, which is inhibited by none of these agents, is absent in yeast. In an attempt to reveal the activity of a propranolol-insensitive Na +-selective antiporter, we compared the rates of Na +/H + and K +/H + antiport in the presence of sufficient propranolol to block the K +/H + antiporter. Between pH 4.6 and 8.8 no difference could be detected. Consequently, we conclude that yeast mitochondria lack the typical Na +-selective Na +/H + antiporter of mammalian mitochondria.

Effects of watershed liming on terrestrial ecosystem processes

Watershed liming has been proposed to mitigate lake acidification and depletion of soil base cations. This paper reviews and synthesizes literature describing the effects of liming on natural terrestrial ecosystems, with a specific emphasis on watershed liming studies. Specifically, we look at the purpose of liming, types of lime, physiological role of calcium, lime effects on soil and belowground processes, and plant response to liming with special attention to growth and tissue chemistry, roots, and plant–plant interactions. Liming increases soil pH and either increases or decreases soil nutrient availability. Liming affects litter decomposition, mineral soil processes, root growth, plant nutrient uptake, and plant productivity. Interspecific plant interactions can be affected after liming. Specific soil and biotic responses depend upon the type and amount of lime applied, the period of observation, soil characteristics, and species composition.Key words: watershed liming, CaCO3, calcite, dolomite, calcium, ecosystem response to liming, wetland liming, forest liming, nutrient availability, soil acidity.

Some effects of 50 years of afforestation on soils in the Kirkton Glen, Balquhidder

Six soil profiles in Kirkton and Monachyle glens have been compared, with the aim of detailing any changes in soil chemistry brought about by forest nutrient uptake. Poorly drained gley soils and freely drained podzol profiles at Kirkton under 50-year-old Scots pine and Sitka spruce, and under clear-felled Sitka and European larch of the same age, were compared with their recently planted (P90) counterparts in Monachyle. Patterns of depletion or repletion of exchangeable cations can be explained in terms of soil hydrogeochemistry.

Role of cations and IgA in saliva-mediated aggregation of Pseudomonas aeruginosa in cystic fibrosis patients.

Oral colonization by Pseudomonas aeruginosa possibly precedes the pulmonary infection process in cystic fibrosis (CF) patients. As bacterial aggregates may play a role in establishment of pulmonary infections, involvement of IgA and cations in CF patient saliva-mediated aggregation of P. aeruginosa was investigated. For colonized patients, P. aeruginosa aggregation correlated with bacterial-specific and total salivary IgA. Cation or IgA depletion reduced P. aeruginosa aggregation by saliva from all patients. However, if cations were removed before IgA, and saliva was then reconstituted with calcium, only colonized patient saliva showed reduced aggregation. Aggregation by IgA-depleted saliva was augmented by reconstituting with original IgA. CF patient saliva-mediated aggregation of P. aeruginosa thus is cation-dependent and enhanced by bacterial-specific IgA. Characterizing the interactions among bacterial aggregating factor(s), cations, and antibodies in CF saliva will help clarify the link between P. aeruginosa oral colonization and pulmonary infections in CF patients.

Acid deposition alters red spruce physiology: laboratory studies support field observations

Two-year-old red spruce (Picearubens Sarg.) seedlings were grown in a poorly buffered soil from a high-elevation site in the Great Smoky Mountains and exposed for 16 weeks to acid mist and rain chemically similar to that occurring at high-elevation sites in the southern Appalachian Mountains. Measurements of seedling growth, root distribution, saturated net photosynthesis, dark respiration, and nutrient content were made to test the hypothesis that acid deposition had caused reductions in the carbon economy noted at high-elevation sites in previous field studies. The role of base cation depletion in these changes was examined by evaluating soil amendments of Ca, Mg, or Ca plus Mg. Acidified rain and mist reduced (i) the apparent carbon economy of foliage, (ii) seedling growth, and (iii) rooting depth in these controlled greenhouse studies. Changes in gas exchange physiology paralleled responses observed for sapling trees in the field with increasing elevation and included both reduced net photosynthesis and increased dark respiration. Calcium deficiency induced by acid deposition is apparently an important mechanism underlying physiological responses of red spruce previously observed in the field. Calcium addition to soil partially reduced the effects of acid deposition, but observed responses suggest that both foliar- and soil-driven reactions are involved. Changes in carbon metabolism associated with reduced Ca availability, when high levels of acid deposition are superimposed on poorly buffered soils, support the inferential association of acid deposition with growth decline of mature red spruce in high-elevation forests of the Appalachian Mountains.

Deoxygenation-induced cation fluxes in sickle cells. III. Cation selectivity and response to pH and membrane potential

Deoxygenation of sickle cells increases membrane permeability to Na, K, and Ca and contributes to cellular cation depletion. This study examines the physiological nature of the pathway that mediates deoxygenation-induced movements of monovalent cations. Deoxygenation-induced Rb influx was a linear function of external Rb concentration, with no evidence of saturation. Activation of the deoxygenation-induced pathway was fostered by alkaline pH (7.5), whereas ion movements via the activated pathway were optimal between pH 6.9 and 7.0 in cells incubated in media in which NO3 replaced Cl to eliminate KCl cotransport. The deoxygenation-induced pathway exhibited no selectivity among the alkali metal cations Li, Na, K, Rb, or Cs, but the monovalent organic cations tetramethylammonium, tetraethylammonium, and N-methylglucamine were excluded. Sickle cells incubated in low-Cl media (external Cl, 40 mM) to depolarize the membrane exhibited increased deoxygenation-induced K efflux and reduced Na influx. Cells treated with valinomycin to hyperpolarize the membrane showed increased deoxygenation-induced Na influx. These characteristics of the deoxygenation-induced transport pathway, linear concentration dependence, lack of cation selectivity, and response to membrane potential, argue against a carrier-mediated mechanism in favor of a diffusional process. The exclusion of small organic cations, however, suggests that factors other than ion size influence deoxygenation-induced permeability.

Cation transport and volume regulation in sickle red blood cells.

Cellular dehydration is one of several pathological features of the sickle cell. Cation depletion is quite severe in certain populations of sickle cells and contributes to the rheological dysfunction that is the root cause of vascular occlusion in this disease. The mechanism of dehydration of sickle cells in vivo has not been ascertained, but three transport pathways may play important roles in this process. These include the deoxygenation-induced pathway that permits passive K+ loss and entry of Na+ and Ca2+; the K(+)-Cl- cotransport pathway, activated by acidification or cell swelling; and the Ca(2+)-activated K+ channel, or Gardos pathway, presumably activated by deoxygenation-induced Ca2+ influx. Recent evidence suggests that these pathways may interact in vivo. Heterogeneity exists among sickle cells as to the rate at which they become dense, suggesting that other factors may affect the activity or interactions of these pathways. Understanding the mechanism of dehydration of sickle cells may provide opportunities for pharmacological manipulation of cell volume to mitigate some of the symptoms of sickle cell disease.

Modelling long-term cation supply in acidified forest stands

A dynamic soil chemistry model was used to explain the observed decrease in soil base saturation between 1949 and 1984 at three stands in southern Sweden. The results show that acid deposition has caused soil acidification. The model, SAFE (Soil Acidification in Forest Ecosystems), includes the fundamental physical processes such as leaching and accumulation, and chemical processes such as cation exchange, mineral weathering, nutrient uptake and solute equilibrium reactions. The sources and sinks of base cations in the soil system were quantified, showing that weathering, deposition of base cations and depletion of exchangeable base cations supply cations to the soil solution in similar amounts in the upper 1 m during the acidification phase. This demonstrates that budget studies alone cannot be used to distinguish between long-term capacity to resist acidification, represented by weathering, from short-term buffering caused by cation exchange.

Processes controlling acid attenuation in the unsaturated zone of a Triassic sandstone aquifer (U.K.), in the absence of carbonate minerals

Continuous core samples were taken through the unsaturated zone at three sites on the outcrop of Permo-Triassic sandstone in the British West Midlands. Sample sites were chosen for lack of recent, direct anthropogenic disturbance, and for differing vegetation: heathland, birch woodland and conifer forest. Interstitial water was extracted and analyzed for 32 major and trace elements. Solid phases were analyzed for exchangeable cations and mineralogy. The rate of recharge calculated using a Cl mass balance method was three times greater below heathland than below afforested sites owing to higher evapotranspiration rates in the woodlands. Carbonate minerals were absent from the unsaturated zone at each site. Soil solutions were acidic and soils at the woodland sites were more acidic (pH 4.0) than those at the heathland site (pH 4.5). Acidic interstitial water solutions were found to up to 5.0 m depth in the unsaturated zone and are partially neutralized by two aluminosilicate mineral reactions in the unsaturated zone: cation exchange and K-feldspar dissolution. The rate at which these acid neutralizing reactions act to neutralize acidity is revealed by the rate of depletion of base cations from the unsaturated zone in recharge solutions; K + (dissolution), Ca +2 + Mg +2 (cation exchange). The total base cation depletion rate was greatest below heathland; this can be attributed mainly to the greater rate of SO 4 assimilation by the woodland biome.

Novel structural patterns in divalent cation-depleted surface layers of Aeromonas salmonicida

The fish pathogen Aeromonas salmonicida possesses a regular surface layer (or A-layer) which is an important virulence determinant. The A-protein, a single bilobed protein organized in a p4 lattice of M4C4 arrangement with two morphological domains, comprises this layer. The role of divalent cations in the A-layer structure was studied to better understand A-protein subunit interactions affecting structural flexibility and function. Divalent cation bridges were found to be involved in the integrity of the A-layer. Two novel A-layer patterns were formed as the result of growth under calcium limitation or by chelation of divalent cations with EDTA or EGTA, thereby constituting the first reported case of formation of distinct regular arrays upon divalent cation depletion. Furthermore, under these conditions A-protein was sometimes released as tetrameric units, rather than in monomeric form. The formation of the two novel patterns is best explained by a sequence of structural rearrangements, following disruption of only one of the two A-layer morphological units, that is, those held together by divalent cation bridges. The free tetrameric units represent four A-protein subunits clustered around the unaffected four-fold axis.