Environmental fate of the triazole fungicide propiconazole in a rice-paddy-soil lysimeter

Environmental fate of the triazole fungicide propiconazole, 1-[[2(2,4-dichlorophenyl)-4-propyl-1,3-diox olane-2-yl]methyl]1H-1,2,4-triazole, in soil was investigated using lysimeters simulating a rice-paddy-soil conditions. Two lysimeters composed of different soil types, a sandy loam (lysimeter A) and silty clay (lysimeter B), were used. Propiconazole (Tilt 250^R EC) plus [U-¹⁴C]-propiconazole was applied over a two-year period to the soil surface of the lysimeters. Propiconazole fate in the lysimeters was assessed by measuring total radioactivity in the leachate, evolved ¹⁴CO₂, and ¹⁴C-residues in the soil and rice plants. The amounts of applied ¹⁴C in the leachate from lysimeter A were 4.4 and 5.2% in the first and second year, respectively. A background level of (0.00005% of applied) ¹⁴C in the leachate from lysimeter B was detected, suggesting negligible movement of the fungicide to groundwater in the silty clay soil. The amount of ¹⁴CO₂ evolved from lysimeter A accounted for 7.8 and 12.2% of applied ¹⁴C in the first and second year, respectively, whereas those from lysimeter B were 5.7 and 7.1%. Total ¹⁴C detected in the rice plants grown in lysimeter A were 7.3 and 9.8% of applied ¹⁴C in the first and second year, respectively, which compared to 3.0 and 7.6% in lysimeter B. Most of the applied ¹⁴C was detected in the top 10 cm soil layer, suggesting that propiconazole remains close to the soil surface after application in soil. Degradation products of propiconazole identified in the lysimeter soils were 1-[[2(2,4-dichlorophenyl)-2-(1,2,4-triazole -1-yl) ketone (DP-1), 1-(2,4-dichlorophenyl)-2-(1,2,4-triazole-1- yl) ethanol (DP-2) and 1-[[2(2,4-dichlorophenyl)-4-hydroxypropyl-1,3-dioxolane-2-yl]methyl]1H-1,2,4-triazole (DP-3 and DP-4).     

Fate of Mycobacterium avium subsp. paratuberculosis after application of contaminated dairy cattle manure to agricultural soils

Details regarding the fate of Mycobacterium avium subsp. paratuberculosis (basonym, Mycobacterium paratuberculosis) after manure application on grassland are unknown. To evaluate this, intact soil columns were collected in plastic pipes (lysimeters) and placed under controlled conditions to test the effect of a loamy or sandy soil composition and the amount of rainfall on the fate of M. paratuberculosis applied to the soil surface with manure slurry. The experiment was organized as a randomized design with two factors and three replicates. M. paratuberculosis-contaminated manure was spread on the top of the 90-cm soil columns. After weekly simulated rainfall applications, water drainage samples (leachates) were collected from the base of each lysimeter and cultured for M. paratuberculosis using Bactec MGIT ParaTB medium and supplements. Grass was harvested, quantified, and tested from each lysimeter soil surface. The identity of all probable M. paratuberculosis isolates was confirmed by PCR for IS900 and F57 genetic elements. There was a lag time of 2 months after each treatment before M. paratuberculosis was found in leachates. The greatest proportions of M. paratuberculosis-positive leachates were from sandy-soil lysimeters in the manure-treated group receiving the equivalent of 1,000 mm annual rainfall. Under the higher rainfall regimen (2,000 mm/year), M. paratuberculosis was detected more often from lysimeters with loamy soil than sandy soil. Among all lysimeters, M. paratuberculosis was detected more often in grass clippings than in lysimeter leachates. At the end of the trial, lysimeters were disassembled and soil cultured at different depths, and we found that M. paratuberculosis was recovered only from the uppermost levels of the soil columns in the treated group. Factors associated with M. paratuberculosis presence in leachates were soil type and soil pH (P < 0.05). For M. paratuberculosis presence in grass clippings, only manure application showed a significant association (P < 0.05). From these findings we conclude that this pathogen tends to move slowly through soils (faster through sandy soil) and tends to remain on grass and in the upper layers of pasture soil, representing a clear infection hazard for grazing livestock and a potential for the contamination of runoff after heavy rains.     

Column Leaching Using Dry Soil to Estimate Solid-Solution Partitioning Observed in Zero-Tension Lysimeters. 1. Method Development

In order to understand the reactions taking place between the soil solid phase and the soil solution, we require knowledge of the chemistry of the soil solution as it occurs in the field. This knowledge allows us to conduct experiments with environmentally relevant concentrations of macro and microelements in solution. Zero-tension lysimeters directly sample the mobile fraction of soil solutions. Unfortunately, they are expensive to sample and require long equilibration periods. Other solution extraction methods do not provide solutions similar in concentration to lysimeters, either because they sample a different fraction of the soil solution or due to the impacts of the sampling process. The processes that produce lysimeter solutions cannot be emulated; however, to estimate lysimeter solution chemistry, we developed a standard protocol to produce solutions that resemble lysimeter solutions from podzolic soils using air-dried samples. We washed air-dried soil columns sequentially with de-ionized water until the electrical conductivity (EC) of the leachates stabilized and then leached the columns using an environmentally relevant concentration of a weak salt solution. We hypothesize that the stabilization point of the EC of the soil solution is indicative of the point at which soluble salts and organic material precipitated during sampling and storage are removed from the soil surface. Solutions produced by leaching, once the EC of wash solutions had stabilized, were comparable to lysimeter solutions from the area where samples were collected with respect to the concentrations of divalent cations, pH, EC and DOC.     

A highly conductive drainage extension to control the lower boundary condition of lysimeters

Lysimeters are used to study and monitor water, fertilizers, salts and other contaminants and are particularly valuable in transpiration and evapotranspiration research. Saturation at the soil bottom boundary in a lysimeter is inherent to its design. A drainage extension made of porous media with high hydraulic conductivity and substantial water holding capacity was devised to extend the lysimeter in order to produce soil moisture conditions mimicking those in the field. Design criteria that assure equal discharge in the soil and in the highly conductive drain (HCD) were established and formulated. Desired matric head at the lysimeter base is determined by HCD extension length. Its value can be manipulated and can range between saturation and the soil's field capacity. Conditions where the HCD is not limiting to flow are obtained through selection of the appropriate cross sectional area ratio between the soil in the lysimeter and the HCD. The validity of these criteria was confirmed with 200 l working lysimeters in the field, with and without plants, and with detailed flow tests utilizing smaller (15 l) lysimeters. Comparison of computed and measured matric head and leachate volume indicates that the proposed method can serve to maintain conditions similar to those in the field.     

Column Leaching using Dry Soil to Estimate Solid-Solution Partitioning Observed in Zero-Tension Lysimeters. 2. Trace Metals

The fundamental questions revolving around research into trace metals in soils are how much, and in what form, do metals exist in soil solutions. The mobile phase of soil solutions can be sampled by lysimeters, but cannot be consistently and accurately reproduced in laboratory extractions. We used a column leaching method developed specifically to produce solutions that were similar to those of lysimeters from northern forest podzolic soils. We hoped to yield reasonable estimates of the partitioning of Cd, Cu, Ni, Pb and Zn between the solid and solution phases observed in the field. The column leaching method produced solutions that were similar to lysimeter solutions in the concentrations of metals in solution. Partitioning coefficients (log K_d) calculated from average lysimeters solution concentrations ranged from 2.8 to 3.9 for Cd, 3.5 to 4.2 for Cu, 3.1 to 4.3 for Ni, 3.9 to 5.1 for Pb and 2.8 to 3.6 for Zn. Laboratory extractions produced very similar log K_d values ranging from 3.4 to 3.9 for Cd, 3.4 to 3.9 for Cu, 3.4 to 4.1 for Ni, 4.1 to 5.2 for Pb and 3.2 to 3.5 for Zn. According to a semi-mechanistic regression model based on observed lysimeter concentrations, the metal concentrations in solution were appropriate relative to known factors that influence metal partitioning in soils: pH and the concentrations of total metals and dissolved organic carbon. Partitioning coefficients based on laboratory extractions in the literature were on average an order of magnitude greater than those observed in lysimeters. When compared to the results of other laboratory extractions, the proposed extraction procedure appeared to be an effective method to estimate the chemistry of soil solutions in the field.     

Studies on the Survival and Fate of Enteroviruses in an Experimental Model of a Municipal Solid Waste Landfill and Leachate

In laboratory scale municipal solid waste lysimeters containing simulated refuse, and seeded with either laboratory or field strains of poliovirus type 1 and echovirus type 7, viruses were not detected in the lysimeter leachate produced over a 4-month period. In addition, viruses were detected in the lysimeter refuse contents after termination of lysimeter operation. These results appeared to be due to virus retention in the lysimeter caused by virus adsorption and virus inactivation. Evidence for virus inactivation was provided by the results of experiments on virus inactivation in composite leachate samples. Evidence for virus adsorption was supported by the rapid adsorption of viruses to various municipal solid waste components in the presence of a salt similar in composition to the major inorganic salts of leachates.     

Land use and hydrologic flowpaths interact to affect dissolved organic matter and nitrate dynamics

The transport and transformation of dissolved organic matter (DOM) and dissolved inorganic nitrogen (DIN) through the soil profile impact down-gradient ecosystems and are increasingly recognized as important factors affecting the balance between accumulation and mineralization of subsoil organic matter. Using zero tension and tension lysimeters at three soil depths (20, 40, 60 cm) in paired forest and maize/soybean land uses, we compared dissolved organic C (DOC), dissolved organic N (DON) and DIN concentrations as well as DOM properties including hydrophilic-C (HPI-C), UV absorption (SUVA₂₅₄), humification index and C/N ratio. Soil moisture data collected at lysimeter locations suggest zero tension lysimeters sampled relatively rapid hydrologic flowpaths that included downward saturated flow through the soil matrix and/or rapid macropore flow that is not in equilibrium with bulk soil solution whereas tension lysimeters sampled relatively immobile soil matrix solution during unsaturated conditions. The effect of land use on DOC and DON concentrations was largely limited to the most shallow (20 cm) sampling depth where DOC concentrations were greater in the forest (only zero tension lysimeters) and DON concentrations were greater in the cropland (both lysimeter types). In contrast to DOC and DON concentrations, the effect of land use on DOM properties persisted to the deepest sampling depth (60 cm), suggesting that DOM in the cropland was more decomposed regardless of lysimeter type. DOC concentrations and DOM properties differed between lysimeter types only in the forest at 20 cm where soil solutions collected with zero tension lysimeters had greater DOC concentrations, greater SUVA₂₅₄, greater humification index and lower HPI-C. Our data highlight the importance of considering DOM quality in addition to DOC quantity, and indicate long-term cultivation reduced the delivery of relatively less decomposed DOM to all soil depths.     

Assessing the performance of a cold region evapotranspiration landfill cover using lysimetry and electrical resistivity tomography

In order to test the efficacy ofa cold-region evapotranspiration (ET) landfill cover against a conventional compacted clay (CCL) landfill cover, two pilot scale covers were constructed in side-by-side basin lysimeters (20m x 10m x 2m) at a site in Anchorage, Alaska. The primary basis of comparison between the two lysimeters was the percolation of moisture from the bottom of each lysimeter. Between 30 April 2005 and 16 May 2006, 51.5 mm of water percolated from the ET lysimeter, compared to 50.6 mm for the the CCL lysimeter. This difference was not found to be significant at the 95% confidence level. As part of the project, electrical resistivity tomography (ERT) was utilized to measure and map soil moisture in ET lysimeter cross sections. The ERT-generated cross sections were found to accurately predict the onset and duration of lysimeter percolation. Moreover, ERT-generated soil moisture values demonstrated a strong linear relationship to lysimeter percolation rates (R-Squared = 0.92). Consequently, ERT is proposed as a reliable tool for assessing the function of field scale ET covers in the absence of drainage measurement devices.     

An Intermediate-Scale Lysimeter Facility for Subsurface Bioremediation Research

A lysimeter facility at Oak Ridge National Laboratory, originally constructed to investigate leaching from low-level radioactive waste, was converted for use as an intermediate-scale facility for subsurface bioremediation research. The six experimental lysimeters are 2.5 m diameter by 4 m deep. The number and size of the lysimeters allow for replicate experiments and extensive sampling of the soil under controlled conditions. The facility provided containment of the contaminated soil, leachate, and microorganisms; positive control of the water table within the lysimeter; the ability to aerate the subsurface; multiple means of adding nutrients, electron acceptors, and electron donors to the subsurface; instrumentation for monitoring oxygen level, temperature, and moisture level; and means for obtaining samples of groundwater, soil, and liquid and gas samples from the soil pores. The flexibility of the facility allows for simulation of a wide range of subsurface bioremediation technologies. Startup and operational procedures and the advantages and disadvantages of the lysimeter facility are discussed. The facility is currently available to the bioremediation research community.     

Mercury translocation in and evaporation from soil. III. quantification of evaporation of mercury from podzolized soil profiles treated with Hg Cl

Mercury evaporation from undisturbed iron‐humus podzol lysimeters was measured over 3 months after treatment with HgCl₂ spiked with radioactive ²⁰³Hg. The relative evaporation rate from HgCl₂ treated soils followed the sum of two exponential functions. Because evaporation asymptotically approaches zero with time, the integral of the fit curve represents the evaporative loss in percent of atmospheric deposition. For the soil investigated, about 5% of atmospheric Hg deposition was reemitted into the atmosphere. It is hypothesized that mercury evaporation can decrease the leaching of mercury in and from soil significantly; this effect is probably increasing with decreasing rain acidity or soil acidity. Mercury deposited as soluble salt remains susceptible to reemission to air for 300 d after incorporation into the soil matrix. Indications are found that Hg evaporation from soils in geological background areas predominantly derives from recent atmospheric Hg deposition and not from geological sources.     

Multi-Species Ecotoxicity Assessment of Petroleum-Contaminated Soil

In 1992, a study was begun to compare the effect of landfarming vs. natural attenuation on the restoration of soil that had been contaminated with crude oil. Each of three lysimeters was filled with a sandy loam topsoil, and crude oil was applied to two of the lysimeters. One of the contaminated lysimeters was tilled, watered, and received a one-time application of fertilizer (N, P, K). No amendments were added to the second contaminated lysimeter, and the third was left uncontaminated. The lysimeters were monitored for 6 months and then left unattended. In 1995 and again in 1997 we sampled these lysimeters to evaluate the long-term effects of contamination and bioremediation. In 1995 we found marked effects on soil chemistry, bacterial, fungal, nematode, and plant populations and a higher rate of bioremediation in the fertilized-contaminated lysimeter (Lawlor et al., 1997). Data from 1997 and previously unreported data from 1995 are the subject of the current report. In 1997, low densities of hydrocarbon-degrading bacteria were found in all the lysimeters and little loss of TPH from the two contaminated lysimeters, suggesting a decreased rate of bioremediation. Nevertheless, there were increases in diversity and number of functional groups of bacteria, nematodes, and native plant species. However, molecular analyses revealed marked differences remained in the composition of dominant eubacterial species, and tests of soybeans indicated field conditions remained unsuitable for these plants.     

Aluminium salts accelerate peroxidation of membrane lipids stimulated by iron salts

Aluminium salts do not themselves stimulate peroxidation of ox-brain phospholipid liposomes, but they greatly accelerate the peroxidation induced by iron(II) salts at acidic pH values. This effect of Al(III) is not seen at pH 7.4, perhaps because Al(III) salts form insoluble complexes at this pH in aqueous solution. Peroxidation of liposomes in the presence of Al(III) and Fe(II) salts is inhibited by the chelating agent desferrioxamine, and by EDTA and diethylenetriaminepentaacetic acid at concentrations greater than those of Fe(II) salt. Aluminium salts slightly stimulate the peroxidation of peroxide-depleted linolenic acid micelles, but they do not accelerate the peroxidation induced by addition of iron(II) salts to the micelles at acidic pH. Aluminium salts accelerate the peroxidation observed when human erythrocytes are treated with hydrogen peroxide at pH 7.4. Desferrioxamine decreases the peroxidation. We suggest that Al(III) ions produce an alteration in membrane structure that facilitates lipid peroxidation, and that the increased formation of fluorescent age pigments in the nervous system of patients exposed to toxic amounts of Al(III) may be related to this phenomenon. The ability of desferal to bind both iron (III) and aluminium(III) salts and to inhibit lipid peroxidation makes it an especially useful chelating agent in the treatment of 'aluminium overload'.     

What limits the distributions of coastally restricted terrestrial invertebrates? The case of coastal landhoppers (Crustacea: Amphipoda: Talitridae) in southern Tasmania

Aim A number of terrestrial invertebrates are known to have distributions limited to the immediate coastal zone, but the factors controlling their distributions are not well understood. This study was planned to correlate the distribution of a coastal terrestrial amphipod, Austrotroides maritimus Friend 1987, which is only found within 100 m of the high tide mark, with soil characteristics and salt deposition. Location South Cape Rivulet Bay on the south coast of Tasmania (146°47′ E, 43°36′ S). Methods Abundance of the amphipods was examined at four sites c. 200 m apart that varied in their exposure to onshore westerly winds. At each site four replicate transect lines were established 3 m apart, with pitfall traps set at 2‐m intervals. The lines were at right angles to the high water mark and extended beyond the inland limit of A. maritimus. Amphipods were trapped at three times of the year, in winter, spring and summer (1993–94), and the sodium content, organic content and moisture content of the soil at each trap site were measured. The sodium content of rain falling on the transects, was also measured, and lysimeters were used to assess the concentration of sodium in water penetrating the soil profile. Results The inland penetration of A. maritimus varied between 18 and 44 m from the seaward edge of woody terrestrial vegetation (itself <10 m horizontally from the high tide mark). Inland penetration increased from west to east around the bay, following an apparent gradient of increased exposure to onshore winds. At the most easterly and apparently most exposed site, however, the species penetrated only 18 m, but this site differed markedly from the others in its topography, caused by erosion of the dunes, with an 8‐m cliff at its seaward end. The soils at this site were also unusually clayey and waterlogged. Amphipod abundance did not correlate strongly with any of the soil parameters. The salt content of rainfall generally declined inland, as did the concentration of lysimeter leachate, but the inland declines were not all smooth, and both rainfall and lysimeter leachate concentration showed some tendency to increase inland at the most sheltered site. Main conclusions Austrotroides maritimus is strongly restricted to the immediate coastal zone. The extent of its inland penetration correlates with exposure to onshore winds, and circumstantial evidence supports the hypothesis that this may be due to differences in the amount of salts deposited.     

Treating Soil Solution Samplers To Prevent Microbial Removal of Analytes

Soil microorganisms colonizing soil water sampling devices (lysimeters) reduced concentrations of biodegradable organic chemicals, including 2,4-dichlorophenoxyacetic acid methyl ester, alachlor, methyl m-chlorobenzoate, and metolachlor as water entered through porous ceramic cups. In some cases, losses exceeded 99%. Additions of either a biocide (sodium hypochlorite) or a bacteriostat (copper salt) prevented microbial activity so that concentrations of test chemicals inside lysimeters equaled those outside. Field studies further indicated that treating lysimeters with a copper salt effectively prevented microbial activity. Thus, chemically treating soil water samplers could improve the accuracy of soil water data for a wide variety of analytes, including environmentally important organics, such as pesticides and industrial wastes, and inorganics, such as ammonia and nitrate.     

Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation

Potentially toxic chemicals are routinely applied to land to meet growing demands on waste management and food production, but the fate of these chemicals is often not well understood. Here we demonstrate an integrated field lysimetry and porewater sampling method for evaluating the mobility of chemicals applied to soils and established vegetation. Lysimeters, open columns made of metal or plastic, are driven into bareground or vegetated soils. Porewater samplers, which are commercially available and use vacuum to collect percolating soil water, are installed at predetermined depths within the lysimeters. At prearranged times following chemical application to experimental plots, porewater is collected, and lysimeters, containing soil and vegetation, are exhumed. By analyzing chemical concentrations in the lysimeter soil, vegetation, and porewater, downward leaching rates, soil retention capacities, and plant uptake for the chemical of interest may be quantified. Because field lysimetry and porewater sampling are conducted under natural environmental conditions and with minimal soil disturbance, derived results project real-case scenarios and provide valuable information for chemical management. As chemicals are increasingly applied to land worldwide, the described techniques may be utilized to determine whether applied chemicals pose adverse effects to human health or the environment.     

Microelement composition of plants grown with low to high levels of sulfur applied to calcareous soil in a glasshouse

Summary PI54619-5-1 soybeans (Glycine max L.), which are very susceptible to Fe deficiency, were grown for 24 days in calcareous (10%) Hacienda loam soil with different levels of S each with and without 2 ppm Fe added as FeEDDHA (ferric ethylenediamine di (o-hydroxyphenylacetic acid). The S application rates ranged from sufficient to neutralize about 15% to more than all of the CaCO₃ present if the S were all oxidized. The soil pH values at harvest time ranged from 7.4 to 6.0. The highest S rate was 10% by weight of soil and it overcame Fe deficiency without FeEDDHA. The S treatments resulted in increased concentrations of Fe and other metals in leaves, but the FeEDDHA treatments increased yields more than did S. At the lower levels of S, the effects of S and FeEDDHA on Fe concentrations in leaves were additive, but not at the highest level of S. The FeEDDHA overcame much of the effect that S had on increasing Mn concentrations in leaves. It had a similar effect, particularly at the low S levels, on Zn, Cu, Al, B, and Ni concentrations in leaves. A level of S sufficient to neutralize only 15% of the CaCO₃ of the soil increased leaf concentrations of Fe, Mn, Zn, Cu, Al, B, Ni, Si, and P. The effect for Zn, Cu, and Al appreared maximum at this level. A combination of the1/2% S and the FeEDDHA resulted in the most favorable micronutrient balance. Bush beans (Phaseolus vulgaris L. var. Improved Tendergreen) grown in calcareous soil with S insufficient to neutralize all the CaCO₃ had increased Mn, Ni, and Mo and decreased Ba levels in leaves. CaSO₄ as a source of S did not have the same effects as elemental S.     

Analysing the role of soil properties, initial biomass and ozone on observed plant growth variability in a lysimeter study

This simulation study is based on a lysimeter experiment with juvenile beech trees (Fagus sylvatica L.) which were grown under ambient or doubled ambient atmospheric ozone concentrations. The aim of the study was to analyze the role of differences in soil properties, differences in initial biomass and ozone impacts on observed plant growth variability at the eight lysimeters of this experiment. For this purpose, we established a new simulation model based on the model system Expert-N by coupling soil water and nitrogen transport models with the plant growth model PLATHO, which was already tested and applied for juvenile beech. In order to parameterize the soil model, for all lysimeters soil hydraulic parameters as well as carbon and nitrogen stocks were measured. Simulation results reveal that the observed decreased growth rates under elevated ozone are due to ozone impacts on plant growth, whereas the high plant growth variability between lysimeters is to a major part the consequence of differences in soil hydraulic properties. Differences in initial biomass are of minor importance to explain plant growth variability in this experiment.     

Toxicity and bioaccumulation of iron in soil microalgae

Microalgae are extensively used in the remediation of heavy metals like iron. However, factors like toxicity, bioavailability and iron speciation play a major role in its removal by microalgae. Thus, in this study, toxicity of three different iron salts (FeSO₄, FeCl₃ and Fe(NO₃)₃) was evaluated towards three soil microalgal isolates, Chlorella sp. MM3, Chlamydomonas sp. MM7 and Chlorococcum sp. MM11. Interestingly, all the three iron salts gave different EC50 concentrations; however, ferric nitrate was found to be significantly more toxic followed by ferrous sulphate and ferric chloride. The EC₅₀ analysis revealed that Chlorella sp. was significantly resistant to iron compared to other microalgae. However, almost 900 μg g^?1 iron was accumulated by Chlamydomonas sp. grown with 12 mg L^?1 ferric nitrate as an iron source when compared to other algae and iron salts. The time-course bioaccumulation confirmed that all the three microalgae adsorb the ferric salts such as ferric nitrate and ferric chloride more rapidly than ferrous salt, whereas intracellular accumulation was found to be rapid for ferrous salts. However, the amount of iron accumulated or adsorbed by algae, irrespective of species, from ferrous sulphate medium is comparatively lower than ferric chloride and ferric nitrate medium. The Fourier transform infrared spectroscopy (FTIR) analysis shows that the oxygen atom and P?=?O group of polysaccharides present in the cell wall of algae played a major role in the bioaccumulation of iron ions by algae.     

Metal-Binding Characteristics of the Gamma-Glutamyl Capsular Polymer of Bacillus licheniformis ATCC 9945

The metal-binding affinity of the anionic poly-gamma-d-glutamyl capsule of Bacillus licheniformis was investigated by using Na, Mg, Al, Ca, Cr, Mn, Fe, Ni, and Cu. Purified capsule was suspended in various concentrations of the chloride salts of the various metals, and after dialysis the bound metals were analyzed either by graphite furnace atomic absorption spectroscopy or by inductively coupled plasma-mass spectrometry. Exposure of purified capsule to excess concentrations of Na revealed it to contain 8.2 mumol of anionic sites per mg on the basis of Na binding. This was confirmed by titration of the capsule with HCl and NaOH. Other metal ions were then added in ionic concentrations equivalent to 25, 50, 75, 100, 200, and 400% of the available anionic sites. The binding characteristics varied with the metal being investigated. Addition of Cu, Al, Cr, or Fe induced flocculation. These metal ions showed the greatest affinity for B. licheniformis capsule in competitive-binding experiments. Flocculation was not seen with the addition of other metal ions. With the exception of Ni and Fe all capsule-metal-binding sites readily saturated. Ni had low affinity for the polymer, and its binding was increased at high metal concentrations. Fe binding resulted in the development of rust-colored ferrihydrite which itself could bind additional metal. Metal-binding characteristics of B. licheniformis capsule appear to be influenced by the chemical and physical properties of both the capsule and the metal ions.     

Geochemistry of recent marine sediments in the Bardawil lagoon,northern Sinai,Egypt

The concentrations of major (Al, Fe, Mg, Ti, K and Na) and minor (Ba, Sr, V, Cu, Mn, Cr, Ni, Zn, Pb and Mo) elements as well as carbonate, organic carbon and total nitrogen have been determined in surface sediments collected at 12 stations from the Bardawil lagoon. The aim of the study was to characterize the geochemistry of the sediments in three different environments, the lagoon, the salt pans and the inlet between the lagoon and the Mediterranean Sea. Higher CaCO₃ percentage (53.5–70.5%) were found in the salt pans where biogenic calcareous components and carbonate rock fragments were found in sufficient quantities in the sediment fractions. Based on high C/N ratios, the organic carbon fraction of the Bardawil lagoon surface sediments is clearly dominated by terrigenous material. The distribution of Al, Fe, Mg and Ti are essentially controlled by the mineralogy of the sediments. The ratios of Ba, Sr, Cu, Mn, Pb and Mo to Al are all high in the salt pans and reflect changes in mineralogy and sediment texture.