Mmol Zn Research Articles

Adsorption characteristics of metal ions by CO 2-fixing Chlorella sp. HA-1

Single and binary metal systems were employed to investigate the removal characteristics of Pb 2+, Cu 2+, Cd 2+, and Zn 2+ by Chlorella sp. HA-1 that were isolated from a CO 2 fixation process. Adsorption test of single metal systems showed that the maximum metal uptakes were 0.767 mmol Pb 2+, 0.450 mmol Cd 2+, 0.334 mmol Cu 2+ and 0.389 mmol Zn 2+ per gram of dry cell. In the binary metal systems, the metal ions on Chlorella sp. HA-1 were adsorbed selectively according to their adsorption characteristics. Pb 2+ ions significantly inhibited the adsorption of Cu 2+, Zn 2+, and Cd 2+ ions, while Cu 2+ ions decreased remarkably the metal uptake of Cd 2+ and Zn 2+ ions. The relative adsorption between Cd 2+ and Zn 2+ ions was reduced similarly by the presence of the other metal ions.

Cd AND Zn TOLERANCE AND ACCUMULATION BY SEDUM JINIANUM IN EAST CHINA

Field survey, hydroponic culture, and pot experiments were carried out to examine and characterize cadmium (Cd) and zinc (Zn) uptake and accumulation by Sedum jinianum, a plant species native to China. Shoot Cd and Zn concentrations in S. jinianum growing on a lead/Zn mine area reached 103–478 and 4165–8349 mg kg−1 (DM), respectively. The shoot Cd concentration increased with the increasing Cd supply, peaking at 5083 mg kg−1 (DM) when grown in nutrient at a concentration of 100 μmol L−1 for 32 d, and decreased as the solution concentration increased from 200 to 400 μmol L−1. The shoot-to-root ratio of plant Cd concentrations was > 1 when grown in solution Cd concentrations ≤ 200 μmol L−1. Foliar, stem, and root Zn concentrations increased linearly with the increasing Zn level from 1 to 9600 μmol L−1. The Zn concentrations in various plant parts decreased in the order roots > stem > leaves, with maximum concentrations of 19.3, 33.8, and 46.1 g kg−1 (DM), respectively, when plants were grown at 9600 μmol Zn L−1 for 32 d. Shoot Cd concentrations reached 16.4 and 79.8 mg kg−1 (DM) when plants were grown in the pots of soil with Cd levels of 2.4 mg kg−1 and 9.2 mg kg−1, respectively. At soil Zn levels of 619 and 4082 mg kg−1, shoot Zn concentrations reached 1560 and 15,558 mg kg−1 (DM), respectively. The results indicate that S. jinianum is a Cd hyperaccumulator with a high capacity to accumulate Zn in the shoots.

A Zinc(II)/Poly(γ‐glutamic acid) Complex as an Oral Therapeutic for the Treatment of Type‐2 Diabetic KKAy Mice

In developing new insulin-mimetic zinc(II) complexes with various ligands including a biodegradable polymer, we prepared and characterized a Zn(gamma-pga) complex in solution as well as in solid, and investigated its in vitro insulin-mimetic activity and in vivo antidiabetic effect in type-2 diabetic KKA(y) mice. The in vitro insulin-mimetic activity of the Zn(gamma-pga) complex was considerable better than that of ZnSO(4). The Zn(gamma-pga) complex normalized the hyperglycemia in KKA(y) mice within 21 d when administrated orally at doses of 10-20 mg (0.15-0.31 mmol) Zn per kg body mass for 30 d. In addition, the impaired glucose tolerance, elevated HbA(1c) levels and metabolic syndromes were significantly improved in Zn(gamma-pga)-treated KKA(y) mice relative to those administrated with saline and ZnSO(4).

Removal of zinc ions from a soil component Na-feldspar by a rhamnolipid biosurfactant

In this study, a microbial surfactant, rhamnolipid, was investigated for its potential to enhance recovery of Zn(II) from Na-feldspar as soil component. The effects of rhamnolipid concentration, pH, and initial Zn(II) ion concentration on the removal of Zn(II) ions from Na-feldspar by rhamnolipid biosurfactant were investigated. As the concentration of Zn(II) ions in solution was increased from 0.47 to 4.08 mM, Zn(II) ions sorption to Na-feldspar decreased from 67.74 to 19.47%. As the concentration of rhamnolipid was increased from 12.5 to 100 mM, the optimum desorption efficiency of zinc ions from Na-feldspar was obtained at 25 mM rhamnolipid concentration and determined as 85.29% at 0.99 mM initial Zn(II) ion concentration in solution (1.73 mmol Zn(II)/kg Na-feldspar). To determine the effect of pH on the desorption efficiency of Zn(II) ions, pH was varied between 5.0 and 7.6. The optimum pH was obtained at 6.8 and the desorption efficency was determined as 83.87% at 0.91 mM initial Zn(II) ion concentration in solution (1.58 mmol Zn(II)/kg Na-feldspar) and 25 mM rhamnolipid concentration. As the concentration of Zn(II) loaded to Na-feldspar was increased from 1.07 to 2.49 mmol Zn(II)/kg Na-feldspar, the maximum Zn(II) desorption efficiency was 98.83% at 2.19 mmol Zn(II)/kg Na-feldspar and at 25 mM rhamnolipid concentration and pH 6.8.

Evaluation of Cellulose Xanthate-Metal-Tetracycline Complexes as a Polymeric Antibacterial Agent with Prolonged Antibacterial Activity

Cellulose xanthate-metal-tetracycline complexes (MCX-metal-Tc) were prepared and evaluated as a controlled release system for the antibiotics. Microcrystallized cellulose was chemically modified to cellulose xanthate (MCX). The amount of metal bound to MCX was 0.36 mmol Cu(II)/g MCX and 0.26 mmol Zn(II)/g MCX. Tetracycline (Tc) bound to MCX-metal chelates was 0.08 mmol/g MCX-Cu(II) and 0.04 mmol/g MCX-Zn(II). The Tc release from MCX-metal-Tc was greatly sustained compared with that from a mixture of cellulose/metal/Tc. Furthermore, MCX-metal-Tc manifested antibacterial activity that lasted for 7–22 days. These results suggest that MCX-metal-Tc is a polymeric antibacterial agent with prolonged antibacterial activity.

Root Exudates, Rhizosphere Zn Fractions, and Zn Accumulation of Ryegrass at Different Soil Zn Levels

A glasshouse experiment was conducted using a root-bag technique to study the root exudates, rhizosphere Zn fractions, and Zn concentrations and accumulations of two ryegrass cultivars ( Lolium perenne L. cvs. Airs and Tede) at different soil Zn levels (0, 2, 4, 8, and 16 mmol kg −1 soil). Results indicated that plant growth of the two cultivars was not advérsely affected at soil Zn level ≤ 8 mmol kg −1. Plants accumulated more Zn as soil Zn levels increased, and Zn concentrations of shoots were about 540 μg g −1 in Aris and 583.9 μg g −1 in Tede in response to 16 mmol Zn kg −1 soil. Zn ratios of shoots to roots across the soil Zn levels were higher in Tede than in Airs, corresponding with higher rhizosphere available Zn fractions (exchangeable, bound to manganese oxides, and bound to organic matter) in Airs than in Tede. Low-molecular-weight (LMW) organic acids (oxalic, tartaric, malic, and succinic acids) and amino acids (proline, threonine, glutamic acid, and aspartic acid, etc.) were detected in root exudates, and the concentrations of LMW organic acids and amino acids increased with addition of 4 mmol Zn kg −1 soil compared with zero Zn addition. Higher rhizosphere concentrations of oxalic acid, glutamic acid, alanine, phenylalanine, leucine, and proline in Tede than in Airs likely resulted in increased Zn uptake from the soil by Tede than by Airs. The results suggested that genotypic differences in Zn accumulations were mainly because of different root exudates and rhizosphere Zn fractions.

A [meso‐Tetrakis(4‐sulfonatophenyl)porphyrinato]zinc(II) Complex As an Oral Therapeutic for the Treatment of Type 2 Diabetic KKAy Mice

We prepared and characterized [meso-tetrakis(4-sulfonatophenyl)porphyrinato]zinc(II) ([Zn(tpps)]), and investigated its in vitro insulin-mimetic activity and in vivo hypoglycemic effect in type 2 diabetic KKA(y) mice. The results were compared with those of previously proposed insulin-mimetic zinc(II) complexes and zinc sulfate (ZnSO(4)). The in vitro insulin-mimetic activity of [Zn(tpps)] was considerably better than that of bis(allixinato)zinc(II) ([Zn(alx)(2)]), bis(maltolato)zinc(II) ([Zn(mal)(2)]), bis(2-aminomethylpyridinato)zinc(II) ([Zn(2-ampy)(2)](2+)), and ZnSO(4). In particular, the order of in vitro insulin-mimetic activity of the complexes was determined to be: [Zn(tpps)]>[Zn(alx)(2)]>[Zn(mal)(2)]>[Zn(2-ampy)](2+)>ZnSO(4). [Zn(tpps)] normalized the hyperglycemia of KKA(y) mice within 21 days when administered orally at doses of 10-20 mg (0.15-0.31 mmol) Zn per kg body mass for 28 days. In addition, metabolic syndromes such as insulin resistance, the degree of renal disturbance, and the degree of liver disturbance were significantly improved in [Zn(tpps)]-treated KKA(y) mice relative to those administered with saline and ZnSO(4). The improvement in diabetes was validated by the results of oral glucose-tolerance tests and the decrease in the HbA(1c) level observed. In contrast, ZnSO(4) and the ligand H(2)tpps did not lower the elevated blood glucose level under the same experimental conditions. Based on these observations, [Zn(tpps)] is proposed to be the first orally active zinc(II)-porphyrin complex for the efficacious treatment of not only type 2 diabetes but also metabolic syndromes in animals.

Zn Accumulation and Subcellular Distribution in the Zn Hyperaccumulator Sedum alfredii Hance

ABSTRACT Zn accumulation and subcellular distribution in leaves of the hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of Sedum alfredii Hance were studied using radiotracer and gradient centrifugation techniques. Leaf Zn accumulation in the HE of S. alfredii was 18.5-26.7 times greater than that in the NHE when the plants were grown at 1-500 μmol Zn L −1 . Leaf section uptake of 65 Zn was highly dependent on external Zn levels. Greater 65 Zn uptake in HE was noted only at external Zn levels ≥100 μmol L −1 . Zinc subcellular distribution in the leaves of the two ecotypes of S. alfredii was: cell wall > soluble fraction > cell organelle. However, more Zn was distributed to the leaf cell wall and soluble fractions for HE than for NHE. In the leaf of HE, 91%–94% of the Zn was found in the cell walls and the soluble fraction and only 6%–9% Zn was distributed in the cell organelle fraction. For NHE, about 20%–26% Zn was recovered in the cell organelle fraction. In stems, Zn distribution to the cell wall fraction was approximately two fold greater in the HE than that in the NHE. For the hyperaccumulating ecotype of S. alfredii , the cell wall and the vacuole played a very important role in Zn tolerance and hyperaccumulation.

Long‐term exposure to elevated zinc concentrations induced structural changes and zinc tolerance of the nitrifying community in soil

A series of long-term Zn-contaminated soils was sampled around a galvanized pylon. The potential nitrification rate (PNR) was unaffected by the soil total Zn concentrations up to 25 mmol Zn kg(-1) whereas spiking the uncontaminated control soil with ZnCl(2) to identical total concentrations completely eliminated nitrification. The larger sensitivity of the PNR to spiked ZnCl(2) than to the Zn added in the field was equally found when relating the PNR to the Zn concentrations in the pore water of these soils, suggesting differences in Zn tolerance of the nitrifying communities. Zinc tolerance in the long-term Zn-contaminated soil was demonstrated by showing that (i) the nitrifying community of long-term Zn-contaminated soil samples was less sensitive to Zn than that of the uncontaminated control soil when both communities were inoculated in sterile ZnCl(2)-contaminated soil samples, and, that (ii) addition of ZnCl(2) to the long-term Zn-contaminated soil samples affected nitrification less than equal additions of ZnCl(2) to uncontaminated control samples. Denaturing gradient gel electrophoresis fingerprinting of polymerase chain reaction amplified 16SrRNA gene fragments of ammonia-oxidizing bacteria showed that the community structure in uncontaminated and long-term contaminated soil samples was different and could be related to soil Zn concentrations.

Tolerance and biosorption of copper and zinc byPseudomonas putidaCZ1 isolated from metal-polluted soil

A strain of Pseudomonas sp. CZ1, which was isolated from the rhizosphere of Elsholtzia splendens obtained from the heavy-metal-contaminated soil in the north-central region of the Zhejiang province of China, has been studied for tolerance to copper (Cu) and zinc (Zn) and its capacities for biosorption of these metals. Based on 16S ribosomal DNA sequencing, the microorganism was closely related to Pseudomonas putida. It exhibited high minimal inhibitory concentration values (about 3 mmol Cu.L-1 and 5 mmol Zn.L-1) for metals and antibiotic resistance to ampicillin but not to kanamycin. Based on the results of heavy metal toxicity screening, inhibitory concentrations in solid media were lower than those in liquid media. Moreover, it was found that the toxicity of Cu was higher than that of Zn. Pseudomonas putida CZ1 was capable of removing about 87.2% of Cu and 99.8% of Zn during the active growth cycle, with specific biosorption capacities of 24.2 and 26.0 mg x L-1, respectively. Although at low concentrations, Cu and Zn slightly damage the surface of some cells, P. putida demonstrated high capacities for biosorption of Cu and Zn. Since P. putida CZ1 could grow in the presence of significant concentrations of metals and because of its high metal uptake capacity in aerobic conditions, this bacterium may be potentially applicable in bioreactors or in situ bioremediation of heavy-metal-contaminated aqueous or soil systems.

Effects of cadmium, zinc and nitrogen status on non-protein thiols in the macroalgae Enteromorpha spp. from the Scheldt Estuary (SW Netherlands, Belgium) and Thermaikos Gulf (N Aegean Sea, Greece)

Enteromorpha prolifera (Scheldt Estuary) and E. linza (Thermaikos Gulf) were incubated at three salinities with 100 and 200microgL(-1)Cd and Zn. The objective was to measure effects of Cd, Zn and nitrogen (N) status on the pools of metal-binding non-protein thiols: glutathione and phytochelatins, (gamma-glutamyl-cysteinyl)(n)-glycine (PC). In E. linza, ammonium pools were higher, but amino acid pools, total N and protein contents were lower than in E. prolifera. Reduced glutathione (GSH) pools were positively correlated with free glutamate and protein contents. In E. linza GSH pools increased and the ratio of reduced to oxidized glutathione (GSH:(GSH+0.5GSSG)), an indicator of oxidative stress, decreased with Cd contents, indicating Cd-induced glutathione oxidation. Total glutathione pools (reduced plus oxidized) ranged from 16nmolSgdwt(-1) in controls (at 0.5micromolCdgdwt(-1)) to 179nmolSgdwt(-1) (at 1.9micromolCdgdwt(-1)) at the highest cadmium dosage. Cadmium stimulated PC synthesis in E. prolifera which suggests that in N-rich algae, glutathione pools were high enough for PC synthesis. In both species GSH and protein increased with Zn contents, whereas GSH:(GSH+0.5GSSG) decreased, which would indicate Zn-induced oxidative stress; in E. linza, at the highest salinity the glutathione redox ratio decreased from 0.61 (at 2.9micromolZngdwt(-1)) to 0.26 (at 4.9nmolSgdwt(-1)) (at 0.5molCdgdwt(-1)). PCs were not synthesized in response to Zn, which may have resulted in Zn-induced GSH oxidation. The presence of both oxidative effects (Cd, Zn) and detoxification (Cd) could be identified by observing the responses of glutathione and PC pools to metal stress.

Biosorption of heavy metal ions on immobilized white-rot fungus Trametes versicolor

Trametes versicolor mycelia were immobilized in carboxymethylcellulose, CMC, beads via entrapment, and the bead containing immobilized fungus spores were incubated at 30 °C for 3 days to attain uniform growth on the bead surface. After incubation, the live and heat inactivated immobilized fungus on the CMC beads were used for the biosorption of Cu 2+, Pb 2+ and Zn 2+ ions. Plain CMC beads were used as a control system. The biosorption of Cu 2+, Pb 2+ and Zn 2+ ions by the CMC and both live and inactivated immobilized preparations increased as the initial concentration of Cu 2+, Pb 2+ and Zn 2+ ions in the medium increased. The maximum biosorption capacities for both immobilized live and heat inactivated Trametes versicolor were 1.51 and 1.84 mmol Cu 2+, 0.85 and 1.11 mmol Pb 2+ and 1.33 and 1.67 mmol Zn 2+ per g of dry biosorbents, respectively. Biosorption equilibrium was established in about 1.0 h and the equilibrium was well described by Langmuir and Freundlich isotherms. A temperature change in the range of 15–45 °C did not affect the biosorption capacity. The affect of pH was also investigated and the maximum adsorption of Cu 2+, Pb 2+ and Zn 2+ ions on the CMC and both live and inactivated immobilized fungal biomass was observed between pH 4.0 and 6.0. The CMC beads with the immobilized fungus can be regenerated using 10 mM HCl, with up to 97% recovery of the metal ions; the biosorbents reused up to five biosorption–desorption cycles without any major loss in the biosorption capacity.

Development and characterization of simulant pancreatic islets

Insulin is stored in pancreatic islets as a zinc–insulin complex, and stimulating the islets results in the release of insulin and zinc. Simulant pancreatic islet beads have been developed using agarose beads (50–250 μm diameter) derivatized with iminodiacetic acid that have been loaded with zinc. A qualitative comparison of the simulant beads with pancreatic islets has been made by staining with dithizone and a zinc-binding fluorescent dye, TSQ. The binding capacity of simulant beads was determined to be 34 μmol Zn 2+/g of dried beads using anodic stripping voltammetry. Hydrochloric acid was used to release zinc from beads to mimic the secretion of insulin from pancreatic islets and a release profile was established. The simulant beads can be used to optimize the islet isolation process and reduce the use of real islets in method development.

Mineral elements and phytase activity in Pisum sativum grown at different Zn supply levels in the greenhouse

Pisum sativum cv ‘Phenomen’ was grown at 1.4–18.0 mmol Zn acetate kg −1 dry soil for 12 and 21 days in a greenhouse to examine the impact of Zn. Results showed that the mineral element status and inter-element relationships were altered even at or below soil and plant Zn levels considered toxic (200–500 mg kg −1 soil and 500 mg kg −1 plant dwt). Cotyledons accumulated Zn, and the overall loss of cotyledon reserve materials and that of K were reduced, but remobilisation of Mg, Ca, Cu, and Mn was enhanced. In vivo total phytase activity correlated negatively with cotyledon dry weight, and N content, but positively with seedling growth. In vitro phytase activity declined at and after day 9, which may point to an age-related factor enhanced by Zn. In the 21-day-old plants, root dry weights were less affected than those of shoots, which were reduced at 3.2 mmol Zn kg −1 and higher soil Zn levels. The N and K concentrations of both shoots and roots, that of P in the roots, and that of Fe in the shoots decreased. Soil Zn reduced the total N, K, P, and Fe contents of entire plants without the shoot-root partitioning being altered, which was concluded to point to direct or indirect effect by Zn on element acquisition. The fraction of shoot Zn decreased with rising soil Zn level. A number of correlations between growth parameters and elements and at inter-element level were altered or inversed, including those of Na and Mn, which were suggested to point to altered or enhanced role for some elements.

Copper and zinc content of periphyton from two rivers as a function of dissolved metal concentration

Measuring the metal content of periphyton is a means of evaluating the state of metal contamination in the environment with respect to levels of metals and their bioavailability. The aim of this study was to identify relationships between the dissolved metal concentrations and the total or intracellular metal concentrations in the periphyton from two rivers. Metal levels at non-contaminated sites were comparable in both rivers (0.07 – 0.71 μmol Cu g–1 dw and 0.22 – 4.36 μmol Zn g–1 dw). The metal content of periphyton from three sites of the Birs River was generally reflective of the dissolved Cu and Zn concentrations in the water. In contrast, metal content in periphyton from two sites of the Thur River did not reflect the dissolved metal concentrations in the water, probably due to speciation effects. Nonexchangeable (intracellular) metal determined after washing of periphyton samples with EDTA was variable and unpredictable when considering total metal content only. The different relationships in the two rivers between the metal contents in periphyton and the dissolved concentrations indicate the influence of speciation on adsorption and bioavailability. Results are discussed in respect to the significance of metal content as a tool for evaluating metal bioavailability.

Combination toxicology of metal-enriched soils: physiological responses of a Zn- and Cd-resistant ecotype of Silene vulgaris on polymetallic soils

Plants of an ecotype of Silene vulgaris (Caryophyllaceae) originating from a Cd-Pb-Zn mine at Plombière (Belgium) were grown on 15 polymetallic soils for a full life-cycle to investigate physiological responses which can help explain previously reported disorders in plants. The degree of regulation of the metal concentration in the young seedlings was a very reliable indicator of the subsequent plant performance. Uptake of Zn could be regulated up to 200 nmol water-soluble Zn g −1 dry soil without surpassing 7 μmol Zn g −1 dry leaf tissue supporting the hypothesis of a high regulating potential of Zn-resistant ecotypes. As soon as a certain ecotype-specific threshold was surpassed the Zn concentration in all plant tissues strongly increased. The Cu concentration in roots and shoots had no threshold and showed the tendency to increase near linearly with the external Cu soil concentration. Similar behaviours were found for Cd, Mn and Pb. The metal concentration of seeds was the lowest of all plant parts; nevertheless it increased linearly with increasing concentration of Fe and Zn in the soil. From visible symptoms the degree of chlorosis was positively related with the concentration of Zn, but not with that of Cu, and interrelated with Fe availability. High cyanidin concentrations in leaves were not indicating a surplus of heavy metals, but deficiency in phosphorus and to a lesser degree in nitrogen. Phytochelatins (PCs) were only present in measurable amounts in leaves of plants grown on soils rich in Cu; but PCs amounts in the early vegetative phase could not be related to vegetative and seed biomass at the reproductive stage. Therefore, it is concluded that PCs are a less reliable indicator of metal toxicity during a full life-cycle than the metal concentration of young seedlings.

Life-cycle phases of a zinc- and cadmium-resistant ecotype of Silene vulgaris in risk assessment of polymetallic mine soils

Short-term exposure of plants to heavy metals is often used for risk assessment of metal-enriched soils (OECD guideline 208) without considering the reliability of the assessment for long-term exposure, i.e. for the completion of a plant's life-cycle. In the present study with 15 orogenic soils three phases of the life-cycle of a Zn–Cd-resistant ecotype of Silene vulgaris were studied to improve risk assessment of metal-enriched soils. The first phase, i.e. emergence of seedlings was not related to the water-soluble or total metal concentration of the soils. Seedling mortality was low as long as the water-soluble metal concentration did not surpass 0.15 μmol Zn and 0.04 μmol Cu g −1 dry soil. Curtailment of the life-cycle prior to flowering, i.e. the vegetative growth as second phase, occurred on those soils where roots and shoots were heavily enriched by Zn already in the seedling phase. In the third phase, i.e. the generative phase, time to flowering and yield differences between orogenic soils were substantial, but soil metal concentrations could not be directly related to timing of reproduction or biomass. Ranking of data showed a high inconsistency of the responses to metal exposure during the first phases of the life-cycle. It is concluded that total plant mass and seed mass are the only realistic endpoints of life-cycle bioassays in risk assessment as long as ranks are inconsistent between two successive early phases of the life-cycle.

Physiological and morphological traits associated with zinc efficiency in Exacum

Interspecific hybrids of Exacum exhibit variation in the expression of zinc efficiency. This research investigated the genetic basis for this variation and evaluated a series of physiological and morphological traits for their association with zinc efficiency. Chi-square analyses of self-pollinated progeny from both zinc-efficient and zinc-inefficient parents indicate a significant genetic component. One hundred percent of the progeny from the inefficient parent were classified as inefficient, while the progeny from the efficient parent segregated 32% inefficient to 68% efficient. Six plants from each phenotypic class (efficient and inefficient) of the efficient parent were utilized in analyses of plant traits. Statistically significant associations were identified between the zinc-efficient phenotype and μmol Zn uptake mg-1 root, root-to-shoot ratio, specific root length, μmol Zn uptake cm-2 root surface area, and Zn uptake cm-1 root length. No association was identified between zinc-efficient phenotype and root diameter, transpiration rate, or H+ production. Zinc uptake cm-1 root length had the greatest association with the zinc-efficiency phenotype and was able to discriminate the two phenotypic classes. We suggest that Zn uptake cm-1 root length is the most significant factor explaining the variation between the zinc-efficient and zinc-inefficient phenotypes in Exacum.

Copper and zinc adsorption by sewage sludge‐treated soil in southern Spain

Heavy metal accumulation in soil due to the application of sewage sludge may induce changes in its ionic retention capacity. In this work, sludge application effects on copper (Cu) and zinc (Zn) adsorption by the surface horizon of a calcareous soil in Southern Spain have been studied. Sludge from the urban waste water treatment plant in Cordoba was applied at rates of 0,40, and 80 Mg sludge ha‐1 for two consecutive years. Despite the low metal content of this sludge and the high amount of organic matter added, a decrease in the soil adsorption levels for both Cu and Zn was detected in the sludged samples. Differences were observed, though, in the behavior of each metal, relative to the main adsorption mechanism involved. Copper adsorption was related to carbonate surfaces in soil. Values up to 400 mmol adsorbed Cu kg‐1 soil were obtained for the three treatments, in equilibrium with 13.6, 16.7, and 17.4 mmol Cu m‐3 in solution for 0, 40, and 80 Mg sludge ha‐1, respectively, the first year, and 13.9, 21.2, and 52.2 mmol Cu m‐3 in solution the second year. However, an increase of soil Cu availability is not likely to arise during or after continuous application of these sludge doses, due to the high calcium carbonate content of this soil. In the case of Zn, adsorption took place in CEC sites, with values up to 40 mmol adsorbed Zn kg‐1 soil in the 0 and 80 Mg sludge ha‐1 samples, in equilibrium with 158.3 and 164.5 mmol Zn m3 in solution, respectively the first year, and 196.1 and 505.8 mmol Zn m3 in solution the second year, whereas in the 40 Mg sludge ha‐1 samples adsorption was below 25 mmol Zn kg‐1 soil, in equilibrium with 171.1 mmol Zn m3 in solution the first year, and 231.0 mmol Zn m‐3 the second year. As soil CEC values and its organic matter content are positively related, Zn availability in this soil could be expected to increase after the cessation of sludge applications, due to the mineralization of the organic matter added.

Trace element supplementation modulates pulmonary infection rates after major burns: a double-blind, placebo-controlled trial

Infections remain the leading cause of death after major burns. Trace elements are involved in immunity and burn patients suffer acute trace element depletion after injury. In a previous nonrandomized study, trace element supplementation was associated with increased leukocyte counts and shortened hospital stays. This randomized, placebo-controlled trial studied clinical and immune effects of trace element supplements. Twenty patients, aged 40 ± 16 y (- ± SD), burned on 48 ± 17% of their body surfaces, were studied for 30 d after injury. They consumed either standard trace element intakes plus supplements (40.4 μmol Cu, 2.9 μmol Se, and 406 μmol Zn; group TE) or standard trace element intakes plus placebo (20 μmol Cu, 0.4 μmol Se, and 100 μmol Zn; group C) for 8 d. Demographic data were similar for both groups. Mean plasma copper and zinc concentrations were below normal until days 20 and 15, respectively (NS). Plasma selenium remained normal for group TE but decreased for group C (P < 0.05 on days 1 and 5). Total leukocyte counts tended to be higher in group TE because of higher neutrophil counts. Proliferation to mitogens was depressed compared with healthy control subjects (NS). The number of infections per patient was significantly (P < 0.05) lower in group TE (1.9 ± 0.9) than in group C (3.1 ± 1.1) because of fewer pulmonary infections. Early trace element supplementation appears beneficial after major burns; it was associated with a significant decrease in the number of bronchopneumonia infections and with a shorter hospital stay when data were normalized for burn size. Am J Clin Nutr 1998;68:365–71.