Ba Removal Research Articles

Seawater barium and sulfide removal improved marine habitability for the Cambrian Explosion of early animals.

An increase in atmospheric pO2 has been proposed as a trigger for the Cambrian Explosion at ∼539-514Ma but the mechanistic linkage remains unclear. To gain insights into marine habitability for the Cambrian Explosion, we analysed excess Ba contents (Baexcess) and isotope compositions (δ138Baexcess) of ∼521-Myr-old metalliferous black shales in South China. The δ138Baexcess values vary within a large range and show a negative logarithmic correlation with Baexcess, suggesting a major (>99%) drawdown of oceanic Ba inventory via barite precipitation. Spatial variations in Baexcess and δ138Baexcess indicate that Ba removal was driven by sulfate availability that was ultimately derived from the upwelling of deep seawaters. Global oceanic oxygenation across the Ediacaran-Cambrian transition may have increased the sulfate reservoir via oxidation of sulfide and concurrently decreased the Ba reservoir by barite precipitation. The removal of both H2S and Ba that are deleterious to animals could have improved marine habitability for early animals.

Trace elements in the water column of high-altitude Pyrenean lakes: Impact of local weathering and long-range atmospheric input

High altitude (alpine) lakes are efficient sentinels of environmental processes, including local pollution and long-range atmospheric transfer, because these lakes are highly vulnerable to ongoing climate changes and increasing anthropogenic pressure. Towards improving the knowledge of trace element geochemistry in the water column of alpine lakes, we assessed 64 physico-chemical parameters, including macro- and micronutrients, major and trace element concentrations in the water column of 18 lakes in the Pyrenees, located along the border between France and Spain.Lake depth, morphology, retention time and watershed rock lithology did not exhibit sizable impact on major and trace element concentrations in the water column. However, acidic (pH = 4.7 ± 0.2) lakes were distinctly different from circumneutral lakes (pH = 6.8 ± 0.5) as they exhibited >10 times higher concentrations of SO42− and trace metals (Fe, Mn, Zn, Cd, Pb, Co, Ni, Be, Al, Ga and REEs). While some of these elements clearly mark the presence of sulphide-rich minerals within the watershed (Fe, Zn, Cd and Pb), the increased mobility of lithogenic elements (Be, Al, Ga and REEs) in acidic lakes may reflect the leaching of these elements from silicate dust derived from atmospheric deposits or surrounding granites. At the same time, compared to circumneutral lakes, acidic lake water displayed lower concentrations of dissolved oxyanions (As, Mo, V, B and W) and elevated SO42− concentrations. The latter could lead to efficient Ba removal from the water column. The exploitation of metal ores within the watershed of three lakes clearly impacted high Zn and Cd concentrations observed in their water column, despite two of these lakes not being acidic. We conclude that local impacts have a greater effect on the water column than long-range atmospheric inputs and that dissolved trace element concentration measurements can be used for revealing sulphide-rich minerals or acid mine drainage within the lakes’ watershed.

Impacts of oak-focused silvicultural treatments on the regeneration layer nine years posttreatment in a productive mixed-oak southern Appalachian forest

Oaks (Quercus spp.) are foundational species in forests and woodlands in the eastern USA. An oak regeneration bottleneck has occurred throughout its range in recent decades, and refining silvicultural treatments to localized conditions has become a focus in addressing this problem. This study was developed to determine species regeneration dynamics among oak and oak competitors on productive sites in response to silvicultural treatments in oak-dominated southern Appalachian mountain forests. The treatments were: an oak shelterwood treatment (25–30% basal area [BA]) reduction through midstory removal with herbicides); a prescribed fire treatment (two, late-dormant season prescribed fires occurring over a 9-yr period); a shelterwood and burn treatment (one, late-dormant season prescribed fire 3–5 yr following 30–40% BA removal); and an unmanaged control. To determine treatment impacts on the regeneration layer, changes in relative and absolute importance values and stems ha-1 (germinants up to stems ≤ 4.9 cm diameter at breast height [DBH]) were calculated at the species group and individual species level 0 and 9 yr postinitial treatment. The greatest relative increases in importance values were 1,401% and 2,995% for the red oak group and yellow-poplar (Liriodendron tulipifera), respectively, in the shelterwood and burn (SWB). Changes in all species groups were predominantly influenced by the smallest size-class (< 0.6 m tall), with the exception of northern red oak (Q. rubra) and yellow-poplar in the SWB. The SWB significantly reduced importance values of all shade-tolerant species groups and was the only treatment to decrease red maple (Acer rubrum) importance value and density over the study duration. The prescribed fire (RXF) treatment increased the red oak group importance value, while simultaneously decreasing yellow-poplar's importance value and increasing red maple's importance value. Changes in the red oak group in the SWB and the RXF were driven by northern red oak. Treatments did not significantly change the importance value of the white oak group. The SWB was the only treatment to significantly decrease overstory BA. The RXF and SWB treatments improved the competitive status of only some oak species, but modifications to these treatments might result in better control of yellow-poplar and red maple competition, further improving oak's competitive status. Although the SWB resulted in modest recruitment of northern red oak saplings, all treatments appear in need of additional follow-up vegetation control to further improve the competitiveness and recruitment of oak into large size-classes.

Equilibrium barium isotope fractionation between minerals and aqueous solution from first-principles calculations

Barium isotopes could be a novel tracer in low-temperature geochemical processes such as the Ba cycle in rivers and oceans. Equilibrium Ba isotope fractionation between Ba-hosting minerals and aqueous solution is of great importance for the applications of Ba isotopes in geochemistry, but it remains poorly constrained. In this study, we performed first-principles calculations based on the density functional theory (DFT) to determine the equilibrium Ba isotope fractionation between minerals and aqueous solution (103lnαmineral-Ba_aq of 137Ba/134Ba). The structural properties of aqueous Ba2+ are well predicted by the first-principles molecular dynamics (FPMD) simulation and 121 snapshots are extracted from FPMD trajectories to estimate the reduced partition function ratio (β factor or 103lnβ of 137Ba/134Ba) of aqueous Ba2+. The 103lnβ decreases in the sequence of aragonite > calcite > aqueous Ba2+ ∼ witherite > barite. The β factor is dominantly determined by the force constant, which is affected by both the average BaO bond length and the coordination number.Our results show that 103lnαaragonite-Ba_aq and 103lnαwitherite-Ba_aq are 0.36‰ and −0.02‰ at 300 K, respectively, consistent with results of experimental studies at equilibrium. The depletion of heavy Ba isotopes observed in natural corals relative to seawater suggests that kinetic effects play an important role in Ba isotope fractionation during coral growth. The 103lnαbarite-Ba_aq is only −0.17‰ at 300 K, indicating limited Ba isotope fractionation caused by the Ba removal stemmed from inorganic barite precipitation. Overall, the equilibrium Ba isotope fractionation factors between minerals and aqueous Ba2+ calculated in this study provide a guideline for the applications of Ba isotopes in low-temperature geochemistry.

A new chemical separation procedure for the determination of rare earth elements and yttrium abundances in carbonates by ICP-MS

The determination of rare earth elements (REEs) and Y in carbonates can be complicated by low REE abundances and the presence of significant amounts of Ba resulting in problematic interferences when analysed by ICP-MS. We describe here a novel ion-exchange method using the DGA resin (TODGA), combined with addition of a Tm spike, which allows the separation of the REEs+Y as a whole prior to analysis using an Element XR ICP-MS. This method was validated with results obtained on three different reference carbonate materials (CAL-S, JLs-1 and BEAN, an in-house standard), yielding reproducibility levels better than 3% (RSD) in most cases. This new separation scheme is particularly well suited for carbonate samples having very low REE contents, but could be equally applied to various rock types and organic-rich sample matrices whenever quantitative Ba removal is required.

Barium removal by photocatalytic process: An alternative for water treatment

This study describes the application of TiO2 in different forms (anatase, P25, TiO2 commercial), ZnO and Nb2O5 for barium ions (Ba(II)) reduction by photocatalysis process. Specific surface area (B.E.T method), X-ray diffraction and photo-acoustic spectroscopy techniques were applied for the catalysts characterization. The parameters studied in the reaction were: presence of additives, pH, amount of catalyst, effect of inorganic compounds, adsorption, photolysis, type of catalyst, additives and the time of contact of the additive/catalyst. No significant reduction in the Ba(II) concentration was observed in absence of additive, however a reduction higher than 50% was observed in the presence of addictive after 120 min of reaction time. Moreover, the effect of Cl− ions, generally present in natural waters, indicated an increase in the Ba(II) reduction time. The adsorption and photolysis tests were not efficient in the Ba(II) removal. However, the contact time between the additive (formic acid) and the catalyst, before the photocatalytic process, showed an improvement in the catalytic activity for all catalysts studied. Therefore, the photocatalysis tests indicated that the catalysts that showed the highest efficiency in the Ba(II) removal were anatase, P25 and ZnO, respectively. The maximum percentage of Ba(II) removal was obtained using anatase as catalyst and at optimized conditions Ba(II) removal was higher than 99% were obtained a reaction time of 90 min.

Barium stable isotopes in the global ocean: Tracer of Ba inputs and utilization

Barium has been used as a biogeochemical tracer for alkalinity, productivity, and riverine inputs in the ocean, but its oceanic cycle remains poorly constrained. Barium stable isotope measurements may improve the use of Ba as a tracer and better constrain the cycling of Ba, but data are only available in limited regions of the oceans. In this study, we present dissolved seawater Ba isotopic compositions in a sample collection spanning the North Atlantic, South Atlantic, North Pacific and Southern Oceans. Compiled global upper-ocean [Ba] data show a relatively constant [Ba] (35–45 nM) in the near-surface waters throughout the global ocean, with the exception of areas near river inputs or strong upwelling. The relatively uniform distribution of [Ba] in the upper ocean seawater indicates that Ba removal is slow relative to supply and mixing, and implies that near-surface Ba isotope values are controlled by basin-scale balances rather than by regional or short-term processes. Seawater Ba isotopic compositions show a large variation of δ138/134Ba values ranging from 0.24 to 0.65‰, and a tight relationship with [Ba]. This global relationship can be simply modelled assuming a primary deep Southern Ocean source for Ba to yield a maximum isotope fractionation of α=1.00058±0.00010 (α=Baseawater138/134/Baparticle138/134). This suggested isotope fractionation during Ba removal from seawater is larger than implied by laboratory measurement during barite formation, suggesting additional fractionating phases or a two-stage fractionation process. Riverine input from the Rio de la Plata to the South Atlantic has a signature of δ138/134Ba=−0.06–0.11‰, which is too light to explain the heavy values (>0.58‰) observed in the surface open ocean. Globally, the Ba isotope composition of the upper ocean waters is correlated with the fraction of Ba utilization at the basin scale (which varies from <15 to 70% at sites studied here). In the deep Atlantic Ocean, distinct δ138/134Ba signals in the northern-sourced (≈0.45‰) and the southern-sourced water (≈0.25‰) trace mixing and allow identification of non-conservative behaviour of Ba, reflecting additional inputs or sinks of Ba during transport (most likely addition from sediment or hydrothermal). Ba isotopes may be useful to trace such inputs in the present and past ocean.

Trembling aspen (Populus tremuloides Michx.) volume growth in the boreal mixedwood: Effect of partial harvesting, tree social status, and neighborhood competition

Variable retention harvesting, with a focus on maintaining biological legacies on managed landscapes, has been practised in the trembling aspen (Populus tremuloides Michx.) dominated boreal mixedwood forests for about two decades. However, little attention has actually been given to the growth response of aspen to partial harvesting. This is the first study to report on tree-level volume growth response of aspen after partial or variable retention harvesting in the Canadian boreal forest. During the winter of 1998–1999, an uncut control, clearcut and two partial harvesting treatments – 1/3 partial cut (1/3PC, 33% BA removal using low thin); 2/3 partial cut (2/3PC, 61% BA removal using high thin) – were applied in 75year old aspen-dominated mixedwood stands in a complete randomized block design. Twelve years after treatment application, 27 dominant and 27 co-dominant trees were collected from unharvested controls and the two partial cut treatments for stem analysis. Annual volume increment (AVI) of individual stems was analyzed as a function of treatment, tree social status, pre-treatment growth, time since treatment application (1–12years) and neighborhood competition. The latter was estimated using a variety of neighborhood competition indices (NCI). There was no evidence of initial growth stagnation after partial harvesting applications. Only the most severe treatment of partial harvesting (2/3 PC) resulted in an increase in volume increment relative to trees in control stands. Annual increase in volume in the 2/3 partial cut was 25.6% higher than controls over 12years. AVI of dominant trees was higher by 16.2dm3yr−1 than that of co-dominants and was proportional to pre-treatment volume growth. No interaction between treatment and social status or pre-treatment growth was observed. The overall results indicate that competition for resources in these stands is essentially size symmetrical. These results should contribute to the development of silviculture prescriptions that aim to maintain both stand productivity and biological legacies.

A magnesium hydroxide preconcentration/matrix reduction method for the analysis of rare earth elements in water samples using laser ablation inductively coupled plasma mass spectrometry

This paper describes a simple method for simultaneous preconcentration and matrix reduction during the analysis of rare earth elements (REEs) in water samples through laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS). From a systematic investigation of the co-precipitation of REEs using magnesium hydroxide, we optimized the effects of several parameters – the pH, the amount of magnesium, the shaking time, the efficiency of Ba removal, and the sample matrix – to ensure quantitative recoveries. We employed repetitive laser ablation to remove the dried-droplet samples from the filter medium and introduce them into the ICP–MS system for determinations of REEs. The enrichment factors ranged from 8 to 88. The detection limit, at an enrichment factor of 32, ranged from 0.03 to 0.20 pg mL −1. The relative standard deviations for the determination of REEs at a concentration of 1 ng mL −1 when processing 40 mL sample solution were 2.0–4.8%. We applied this method to the satisfactory determination of REEs in lake water and synthetic seawater samples.

Patterns of basal area increment, mortality and recruitment were related to logging intensity in subtropical rainforest in Australia over 35 years

Eight silvicultural treatments were applied to a subtropical rainforest site in Wiangarie State Forest, northern NSW, in the mid 1960s. Tree growth in the plots and ingrowth into the >10 cm diameter at reference height (DRH) category was measured over 35 years. The average basal area in three unlogged plots was 51.5 m 2/ha. The basal areas after logging in the silviculturally-treated plots ranged from 58 to 12 m 2 representing reductions between 26 and 77%. Increment in the basal area over a wide range of treatments averaged about 0.5 m 2 per year after a period of reduced basal area due to post-logging mortality. Basal area had returned to similar levels in the unlogged plots in the less intense treatments after 35 years. The time taken for the patterns of mortality, recruitment and growth to return to levels similar to the unlogged controls was related to the intensity of logging. Recruitment generally increased as the retained basal area decreased. Post-logging mortality increased as the retained basal area decreased except in the two heaviest treatments. Very low intensity (BA removal) treatments had a relatively short-lived and minor effect on stand dynamics. Intense treatments were not necessary to achieve higher growth rates although the duration of increased growth was related to the intensity of treatment. In heavier treatments follow-up operations are needed to prevent stands from being dominated by lianas and early successional species, to the exclusion of the primary rainforest species.

Ba and Co Removal from Water by Elution Through Fixed Beds of Phillipsite- and/or Chabazite-Rich Tuffs

The possibility of using phillipsite- and chabazite-rich tuffs as cation exchangers in the process of barium and cobalt removal from wastewaters was evaluated. Accordingly, fixed beds of phillipsite-rich Neapolitan yellow tuff grains and of chabazite-rich Orvieto-Bagnoregio ignimbrite grains were prepared. After exchanging them in Na+ form, the relevant breakthrough curves were determined at room temperature, using 100 mg/L solutions for each cation. Some characteristic dynamic parameters were calculated from these curves, such as length of mass transfer zone, ion exchange capacity in dynamic conditions, dynamic selectivity and efficiency of the process, obtaining information on the conditions under which the process should be carried out. The data collected evidenced the good selectivity of both Na-exchanged zeolites for Ba and the poor selectivity for Co, confirming the results previously obtained in equilibrium conditions. The difficulty of eluting barium from the tuff beds during regeneration suggested a profitable employment of Italian phillipsite- and/or chabazite-rich tuffs in discontinuous processes, which are especially useful in the treatment of nuclear power plant wastes, in which the zeolitic sludge generated from Ba removal is usually stabilized–solidified in a cement matrix.

Fruit and Hormones Influence Flowering of Apple. II. Effects of Hormones

Combination postbloom sprays of BA at 50 mg·liter-1 and daminozide at 2000 mg·liter-1 were made to limbs of `Early McIntosh' apple (Malus domestics Borkh.) where all of the flowers were either removed before full bloom or allowed to remain. BA and fruit removal increased return bloom, whereas daminozide bad no effect. No treatment had a consistent effect on spur leaf area. Repeat sprays of GA4+7 to `Delicious' apple trees at full bloom (FB) +5, FB + 14, and FB +22 days reduced appendage development and flower bud formation on spurs. One spray of GAd+7 at 150 mg·liter-1 at FB +42 days reduced appendage formation and the percentage of flowering spurs but not as effectively as earlier repeat sprays of GA4+7 at 50 mg·liter-1 When BA at 150 mg·liter-1 was combined with the GA at FB +42 days, appendage formation was increased but the reduction in flowering was not reversed. One BA spray at 50 mg·liter-1 at FB +22 days to `McIntosh' trees increased the number of appendages formed in spurs, but return bloom was not influenced. Chemical names used: (N -phenylmethyl) -1 H -purine-6-amine (BA); butanedioic acid mono (2, 2-dimethylhydrazide) (daminozide); gibberellins A4 and A7 (GA4+7).

Inhibition of increased potassium permeability following fertilization of the echinoderm embryo: Its relationship to the initiation of protein synthesis and potassium exchangeability

Addition of 10 m M Ba to suspensions of single-cell embryos of the echnioderm Lytechinus results in a depolarization of membrane potential, an increase in membrane resistance, and a reduction of the unidirectional efflux rate coefficient for potassium. All these effects are consistent with a decrease in membrane permeability to potassium ion ( P K). Determination of P K in the presence of Ba indicates a 3- to 5-fold decrease in its magnitude as compared to Ba free cells. Ba at concentrations of 0.5 m M or less has no significant effect on P K. Its effect is maximal at approximately 10 m M, and it is completely reversible upon Ba removal. Eggs fertilized and maintained in 10 m M Ba do not undergo the 3- to 4-fold increase in P K which follows fertilization but rather, they maintain values for P K equivalent to or less than those found in the unfertilized egg. This allows one to evaluate the relationship of the normal increase in P K to the increase in the exchangeability of intracellular K and the onset of protein synthesis, both of which occur shortly after fertilization. The results indicate that the onset of protein synthesis and the increased exchange of intracellular K are events which are independent of the increase in P K. Neither is significantly altered by Ba suppression of the P K increase. The results also indicate that active K transport and amino acid transport are unaffected by maintenance of a low P K. Furthermore, inhibition of protein synthesis (greater than 95% with 10 −4 M emetine) does not prevent the increased exchange of intracellular K or the increase in P K. Active K transport and amino acid transport are also unaffected.