Cd-tolerant arbuscular mycorrhizal (AM) fungi from heavy-metal polluted soils

Spores of arbuscular mycorrhizal (AM) fungi were isolated from two heavy-metal polluted soils in France via trap culture with leek (Allium porrum L.). Preliminary identification showed that the predominant spore type of both cultures (P2 and Cd40) belongs to the Glomus mosseae group. Their sensitivity to cadmium was compared to a laboratory reference strain (G. mosseae) by in vitro germination tests with cadmium nitrate solutions at a range of concentrations (0 to 100 mg L^–1) as well as extracts from a metal-polluted and unpolluted soils. Both cultures of AM fungi from heavy-metal polluted soils were more tolerant to cadmium than the G. mosseae reference strain. The graphically estimated EC₅₀ was 0.8 mg L^–1 Cd (concentration added to the test device) for G. mosseae and 7 mg L^–1 for P2 culture, corresponding to effective Cd concentrations of approximately 50–70 g L^–1 and 200–500 g L^–1, respectively. The extract of the metal-polluted soil P2 decreased germination of spores from the reference G. mosseae but not from P2 culture. However, the extracts of two unpolluted soils with different physico-chemical characteristics did not affect G. mosseae, whereas germination of P2 spores was markedly decreased in the presence of one of the extracts. These results indicate a potential adaptation of AM fungi to elevated metal concentrations in soil. The tested spores may be considered as metal-tolerant ecotypes. Spore germination results in presence of soil extracts show the difficulty of assessing the ecotoxic effect of metals on AM fungi without considering other soil factors that may interfere in spore germination and hyphal extension.     

Heavy metal tolerance and accumulation of Cd, Cr and Ni by Cannabis sativa L.

Experiments in semi-natural conditions were undertaken to assess hemp metal tolerance and its ability to accumulate cadmium, nickel and chromium. Cannabis sativa was grown in two soils, S1 and S2, containing 27, 74, 126 and 82, 115, 139 g g^–1 of Cd, Ni and Cr, respectively. After two months from germination and at ripeness, no significant alteration in plant growth or morphology was detected. On the contrary, a high hemp reactivity to heavy metal stress with an increase in phytochelatin and DNA content was observed during development, suggesting the Cannabis sativa ability to avoid cell damage by activating different molecular mechanisms. Metals were preferentially accumulated in the roots and only partially translocated to the above-ground tissues. The mean shoot Cd content was 14 and 66 g g^–1 for S1 and S2 soil, respectively. Although not negligible concentrations they were about 100 times lower than those calculated for the hyperaccumulator Thlaspi caerulescens. Similarly Ni uptake was limited if compared with that of the Ni-hyperaccumulator Alyssum murale. Chromium uptake was negligible. As expected on the base of the metal concentration detected in ripe plants, no statistically significant variation in soil metal content was detected after one crop of hemp. Nevertheless, a consistent amount (g) of Cd and Ni is expected to be extracted by 1 ha biomass of hemp (about 10 t) per year and along the time a slow restoration of deeper soil portions can be obtained by its wide root system (at least 0,5 m deep). In addition, the possibilities of growing hemp easily in different climates and using its biomass in non-food industries can make heavy metal contaminated soils productive. This means economical advantage along with a better quality of soil.     

Pollution of soil and vegetation in the Thriasian Plain,Greece

Summary The Thriasian Plain near Athens in Greece is a site of concentrated industrial development. Total concentrations of Pb, Cd and extractable SO₄ ^2– in surface soil samples collected from this area, were found to be, respectively, 2–7, 6–34 and 2–20 times higher than those in similar soil samples from parts of the country remote from industrial activity.Total concentrations of Pb, Cd, Zn, Cr and S in samples of olive leaves from the same area were found to be, respectively, 4–40, 3–10, 3–9, 2–6 and 17–21 times higher than those found in samples of olive leaves from rural sites. Leaves of cabbages growing in the area contained between 0.82 and 40 g/g (wet weight) of Pb.Addition of Cd, Ni and Cu to a calcareous potted soil at concentrations of 100, 200 and 200 ppm increased the concentrations of the metals in the needles of Aleppo pine (Pinus halepensis) seedlings to 4.5, 3.5 and 10 ppm, respectively, after 7 months growth in the nursey.     

Phytoavailability of Cd and Zn in soil estimated by stable isotope exchange and chemical extraction

The distribution of labile Cd and Zn in two contrasting soils was investigated using isotopic exchange techniques and chemical extraction procedures. A sewage sludge amended soil from Great Billings (Northampton, UK) and an unamended soil of the Countesswells Association obtained locally (Aberdeen, UK) were used. ¹¹⁴Cd and ⁶⁷Zn isotopes were added to a water suspension of each soil and the labile metal pool (E-value) determined from the isotope dilution. Samples were obtained at 13 time points from 1h to 50 days. For the sewage sludge amended soil, 29 g Cd g^–1 (86% of total) and 806 g Zn g^–1 (65% of total) were labile and for the Countesswells soil the value was 8.6 g Zn g^–1 (13% of total); limits of detection prevented a Cd E-value from being measured in this soil. The size of the labile metal pool was also measured by growing plants for 90 days and determining the isotopic content of the plant tissue (L-value). Thlaspi caerulescensJ. & C. Presl (alpine penny cress), a hyperaccumulator of Zn and Cd, Taraxacum officinale Weber (dandelion) and Hordeum vulgare L. (spring barley) were used. L-values were similar across species and lower than the E-values. On average the L-values were 23±0.8 g Cd g^–1 and 725±14 g Zn g^–1 for the Great Billings soil and 0.29±0.16 g Cd g^–1 and 7.3±0.3 g Zn g^–1 for the Countesswells soil. The extractable metal content of the soils was also quantified by extraction using 0.1 M NaNO₃, 0.01 M CaCl₂, 0.5 M NaOH, 0.43 M CH₃COOH and 0.05 M EDTA at pH 7.0. Between 1.3 and 68% of the total Cd and between 1 and 50% of the total Zn in the Great Billings soil was extracted by these chemicals. For the Countesswells soil, between 6 and 83% of the total Cd and between 0.1 and 7% of the total Zn was extracted. 0.05 M EDTA and 0.43 M CH₃COOH yielded the greatest concentrations for both soils but these were less than the isotopic estimates. On the whole, E-values were numerically closer to the L-values than the chemical extraction values. The use of isotopic exchange provides an alternative estimate of the labile metal pool within soils compared to existing chemical extraction procedures. No evidence was obtained that T. caerulescens is able to access metal within the soil not freely available to the other plants species. This has implications for long term remediation strategies using hyperaccumulating plant species, which are unlikely to have any impact on non-labile Cd and Zn in contaminated soil.     

Ecological study of soil fungi of an agricultural field in Allahabad

Summary The soil fungi from an agricultural field in Allahabad where sugarcane is being grown for many years, have been isolated from various depths during different seasons and were identified. The inter-relations of chemical composition of soil and distribution of fungi is also being shown here.The techniques for the isolation and the study of the fungus flora was that ofGoddard modified bySaksena &Mehrotra. Soil samples were examined from 1–6 depths in three seasons of the year and were mechanically and chemically analysed.For the isolation, soil dilution plate method, a modification ofMenzies' method, direct method ofWaksman, Rossi Cholodny Burried slide technique, and screened immersion plate method, were followed Fifty five different species of microfungi belonging to Phycomycetes, Ascomycetes and Fungi — Imperfecti were isolated and identified. The moisture contents, hydrogen-ion concentrations, carbon, nitrogen, phosphorus, calcium, magnesium and iron, etc., of the soil samples from 1–6 inches depths, were also studied.Out of these 12 species covering 9 genera belonged to the Phycomycetes, nine genera of Ascomycetes and nine genera of Fungi Imperfecti were recorded.P. multicolor Grigorieva-Monoilova &Poradielova, andP. roqueforti Thom.,Gliocladium vermoesoni (Biourge)Thom. andMasoniella grisea (Smith)Smith were recorded for the first time from Indian Soil. A new varietyChaetominum nigricolor Ames var.simplex was also isolated.     

Thermal niche for in situ seed germination by Mediterranean mountain streams: model prediction and validation for Rhamnus persicifolia seeds

Background and Aims

Mediterranean mountain species face exacting ecological conditions of rainy, cold winters and arid, hot summers, which affect seed germination phenology. In this study, a soil heat sum model was used to predict field emergence of Rhamnus persicifolia, an endemic tree species living at the edge of mountain streams of central eastern Sardinia.

Methods

Seeds were incubated in the light at a range of temperatures (10–25 and 25/10 °C) after different periods (up to 3 months) of cold stratification at 5 °C. Base temperatures (T_b), and thermal times for 50 % germination (θ₅₀) were calculated. Seeds were also buried in the soil in two natural populations (Rio Correboi and Rio Olai), both underneath and outside the tree canopy, and exhumed at regular intervals. Soil temperatures were recorded using data loggers and soil heat sum (°Cd) was calculated on the basis of the estimated T_b and soil temperatures.

Key Results

Cold stratification released physiological dormancy (PD), increasing final germination and widening the range of germination temperatures, indicative of a Type 2 non-deep PD. T_b was reduced from 10·5 °C for non-stratified seeds to 2·7 °C for seeds cold stratified for 3 months. The best thermal time model was obtained by fitting probit germination against log °Cd. θ₅₀ was 2·6 log °Cd for untreated seeds and 2·17–2·19 log °Cd for stratified seeds. When θ₅₀ values were integrated with soil heat sum estimates, field emergence was predicted from March to April and confirmed through field observations.

Conclusions

T_b and θ₅₀ values facilitated model development of the thermal niche for in situ germination of R. persicifolia. These experimental approaches may be applied to model the natural regeneration patterns of other species growing on Mediterranean mountain waterways and of physiologically dormant species, with overwintering cold stratification requirement and spring germination.     

Evaluation of powdered pine bark for control ofMeloidogyne arenaria andHeterodera glycines on soybean

Commercially avaiable pine bark nuggets (composted) and fresh pine bark were ground into powders and added at rates of 0 to 50 g kg^–1 to field soil infested withMeloidogyne arenaria andHeterodera glycines. The treated soil was maintained moist in the greenhouse for 2 weeks, sampled, and planted with Davis soybean (Glycine max.). Eight weeks after planting, numbers ofM. arenaria andH. glycines in soil decreased with increasing amounts of composted or fresh pine bark. No juveniles were present in soil treated with 5% pine bark. The number of galls and cysts g^–1 root decreased in proportion to the amount of pine bark added to soil. Gall and cyst formation was completely eliminated at the 5% rate. Numbers of saprophagous nematodes were highest in soil with 4–5% pine bark. The activity of several soil enzymes was correlated with the addition of both composted and fresh pine bark. Fresh pine bark powder caused an increase in soil enzyme activity compared to composted pine bark, but did not provide consistent control of gall and cyst formation.Journal Series No. 18-933579 Alabama Agricultural Experiment Station     

Effects of outbreak of the train millipede Parafontaria laminata armigera Verhoeff (Diplopoda: Xystodesmidae) on litter decomposition in a natural beech forest in Central Japan. 1. Density and biomass of soil invertebrates

Soil invertebrates were studied to determine the animals important in litter decomposition and soil formation in a natural forest of Fagus crenata Blume mixed with Quercus mongolica var. grosseserrata Rehd. et Wils., where outbreak of the adult train millipede, Parafontaria laminata armigera Verhoeff was recorded in 1980. The density and biomass of soil invertebrates, and their distribution in soil, were surveyed largely by hand sorting and also using Tullgren and Baermann apparatuses. The densities of soil macroinvertebrates were 10²–10³ individuals/m². Diplopoda was the most abundant among them, 87.3% of which was the train millipede. The total biomass in wet weight of soil macro-invertebrates was 34.9–70.5g/m² in 1980–1981, when the millipede was pre-adult or adult, and it decreased to 3.5–6.7g/m² in 1982–1984, when it was young. The density of soil invertebrates extracted by apparatuses was 10⁴–10⁶ individuals/m². The total biomass of these was estimated to be 5.8–10.8g/m². The majority of soil invertebrates lived in the A₀ horizon, whereas the train millipede lived in soil of the A₁+A₂ horizon. These results suggest that the train millipede is one of the most important soil invertebrates affecting soil properties. For evaluating the importance of the species, more than 8 years survey of hand-sorting together with the Tullgren apparatus was necessary, as the train millipede grew synchronously and had an 8-year life span and young stages of 1.5–3.5mm long.     

Brevibacillus brevis Isolated from Cadmium- or Zinc-Contaminated Soils Improves in Vitro Spore Germination and Growth of Glomus mosseae under High Cd or Zn Concentrations

In this study we investigated the saprophyte growth of two arbuscular–mycorrhizal fungi (Glomus mosseae isolate) under increasing Cd or Zn levels and the influence of a selected bacterial strain of Brevibacillus brevis. Microorganisms here assayed were isolated from Cd or Zn polluted soils. B. brevis increased the presymbiotic growth (germination rate growth and mycelial development) of Glomus mosseae. Spore germination and mycelial development of both G. mosseae isolate were reduced as much as the amount of Cd or Zn increased in the growth medium. In medium supplemented with 20 μg Cd mL⁻¹, the spore germination was only 12% after 20 days of incubation, but the coinoculation with B. brevis increased this value to 40% after only 15 days. The addition of 20 μg Cd mL⁻¹ to the growth medium drastically inhibited hyphal development, but the presence of the bacterium increased hyphal growth of G. mosseae from 195% (without Cd) until 254% (with 20 μg Cd mL⁻¹). The corresponding bacterial effect increasing micelial growth ranged from 125% (without Zn) to 232% (200 μg Zn mL⁻¹) in the case of G. mosseae isolated from Zn-polluted soil. Mycelial growth under 5 μg Cd mL⁻¹ (without bacterium) was similarly reduced from that produced at 15 μg Cd mL⁻¹ in the presence of the bacteria. As well, 50 μg Zn mL⁻¹ (without bacterium) reduced hyphal growth as much as 200 μg Zn mL⁻¹ did in the presence of B. brevis. The bacterial effect on the saprophytic growth of G. mosseae in absence of metal may be due to the involvement of indole acetic acid (IAA) produced by these bacteria. The Cd bioaccumulation ability exhibited (76%) by Cd-adapted B. brevis reduced the Cd damage on G. mosseae in Cd-contaminated medium. These capabilities of B. brevis isolates partially alleviate the inhibitory effects of Cd or Zn on the axenic growth of G. mosseae.     

Accumulation of cadmium by immobilizedZoogloea ramigera 115

Summary Zoogloea ramigera 115 was immobilized into beads of calcium-alginate and placed into batch air-bubbled column reactors. In the absence of any added nutrients the immobilized bacterium adsorbed Cd from solutions containing levels of 2 and 20 g ml^–1 per day, over a period of 21 and 20 days, respectively. Adsorption of Cd from solutions containing 20 g ml^–1 Cd was better than 90% for 16 days. Beads treated with Cd at 2 g ml^–1 never adsorbed less than 95% of the metal. Alginate adsorbed Cd as well, but inclusion of cells changed the effectiveness of adsorption. Of a 250 g ml^–1 Cd solution, alginate adsorbed 70.4% Cd in 60 min whereas alginate plus cells adsorbed 90.5% in the same time span. Temperature had no effect on adsorption by immobilized cells at levels of 2 and 10 g ml^–1 Cd. However at higher concentrations, binding was enhanced as temperature increased.Z. ramigera beads were stable during all treatments and for prolonged periods of time (21 days).     

Comments on “Seed germination as a thermobiological problem” (A reply)

Summary The criticisms formulated by J. E. Philipp against my former article [Labouriau LG (1978) Radiat Environ Biophys 15: 345–366] are analysed and answered, in connection with1. the applicability of the activation-energy approach to the kinetics of seed germination,2. the use of curvilinearversus rectilinear Arrhenius plots,3. with the interpretation of3.1. the extreme temperature cardinal points,3.2. of the thermodynamic parameters of the activation of germination, and3.3. of the informational entropy of the distributions of isothermal germination times.Discussion about the Paper Seed Germination as a Thermobiological Problem by L. G. Labouriau Radiation and Environmental Biophysics 15:345–366 (1978)     

Geochemical aspects of aluminium in forest soils in Galicia (N.W. Spain)

The aqueous speciation of Al was studied in acid forest soils in N.W. Spain. Aluminum concentrations were 10–70 mol L^–1, with variable proportions oflabile, nonlabile, andacid-soluble Al. Almost all thelabile Al was found complexed with F^–, Al³⁺ concentrations being low. The importance of organic matter was seen in the formation of Al-organic complexes in the solid soil fraction and the presence of aqueous alumino-organic complexes in superficial horizons (umbric epipedons) rich in organic matter.     

Utilisation of soil organic P by agroforestry and crop species in the field,western Kenya

A field experiment in western Kenya assessed whether the agroforestry species Tithonia diversifolia (Hemsley) A. Gray, Tephrosia vogelii Hook f., Crotalaria grahamiana Wight & Arn. and Sesbania sesban (L) Merill. had access to forms of soil P unavailable to maize, and the consequences of this for sustainable management of biomass transfer. The species were grown in rows at high planting density to ensure the soil under rows was thoroughly permeated by roots. Soil samples taken from beneath rows were compared to controls, which included a bulk soil monolith enclosed by iron sheets within the tithonia plot, continuous maize, and bare fallow plots. Three separate plant biomass samples and soil samples were taken at 6-month intervals, over a period of 18 months. The agroforestry species produced mainly leaf biomass in the first 6 months but stem growth dominated thereafter. Consequently, litterfall was greatest early in the experiment (0–6 months) and declined with continued growth. Soil pH increased by up to 1 unit (from pH 4.85) and available P increased by up to 38% (1 g P g^–1) in agroforestry plots where biomass was conserved on the field. In contrast, in plots where biomass was removed, P availability decreased by up to 15%. Coincident with the declines in litterfall, pH decreased by up to 0.26 pH units, plant available P decreased by between 0.27 and 0.72 g g^–1 and P_o concentration decreased by between 8 and 35 g g^–1 in the agroforestry plots. Declines in P_o were related to phosphatase activity (R²=0.65, P<0.05), which was greater under agroforestry species (0.40–0.50 nmol MUB s^–1 g^–1) than maize (0.28 nmol MUB s^–1 g^–1) or the bare fallow (0.25 nmol MUB s^–1 g^–1). Management of tithonia for biomass transfer, decreased available soil P by 0.70 g g^–1 and P_o by 22.82 g g^–1. In this study, tithonia acquired P_o that was unavailable to maize. However, it is apparent that continuous cutting and removal of biomass would lead to rapid depletion of P stored in organic forms.     

Effects of Cd and Zn on the development of annual xylem rings of young Norway spruce (Picea abies) plants

Three-year-old spruce (Picea abies) saplings were planted and cultivated for 2 years in pots with 3 1 substrate, consisting of a homogenized mixture of sand, peat and forest soil with a high organic content (volume ratio 11.52). This substrate was amended with 10–180 mol Cd [kg soil dry weight (DW)]^–1, 50–7500 mol Zn (kg soil DW)^–1 (determined with 1 M ammonium acetate extracts) or combinations of both elements. Annual xylem growth rings in stems of plants treated with 50 mol Cd (kg soil DW)^–1 or 7500 mol Zn (kg soil DW)^–1 were significantly narrower than in control plants. Growth reductions were more pronounced in the second year of the experiment. The contents of Cd and Zn in stem wood and needles were positively correlated with the substrate concentrations. The Mg contents of the spruce needles were inversely correlated with soil concentrations of Cd and Zn. Root development was impeded at moderate concentrations of Cd (50 mol kg^–1) or Zn (1000 mol kg^–1) in the substrate. The adverse effects of potentially toxic trace elements, like Cd or Zn, on xylem growth of spruce plants are discussed with regard to possible growth reductions in forest trees under field conditions.     

Effect of soil compaction on root growth and uptake of phosphorus

Summary Zea mays L. andLolium rigidum Gaud. were grown for 18 and 33 days respectively in pots containing three layers of soil each weighing 1 kg. The top and bottom layers were 100 mm deep and they had a bulk density of 1200 kg m^–3, while the central layer of soil was compacted to one of 12 bulk densities between 1200 and 1750 kg m^–3. The soil was labelled with³²P and³³P so that the contribution of the different layers of soil to the phosphorus content of the plant tops could be determined. Soil water potential was maintained between –20 and –100 kPa.Total dry weight of the plant tops and total root length were slightly affected by compaction of the soil, but root distribution was greatly altered. Compaction decreased root length in the compacted soil but increased root length in the overlying soil. Where bulk density was 1550 kg m^–3, root length in the compacted soil was about 0.5 of the maximum. At that density, the penetrometer resistance of the soil was 1.25 and 5.0 MPa and air porosity was 0.05 and 0.14 at water potentials of –20 and –100 kPa respectively, and daytime oxygen concentrations in the soil atmosphere at time of harvest were about 0.1 m³m^–3. Roots failed to grow completely through the compacted layer of soil at bulk densities 1550 kg m^–3. No differences were detected in the abilities of the two species to penetrate compacted soil.Ryegrass absorbed about twice as much phosphorus from uncompacted soil per unit length of root as did maize. Uptake of phosphorus from each layer of soil was related to the length of root in that layer, but differences in uptake between layers existed. Phosphorus uptake per unit length of root was higher from compacted than from uncompacted soil, particularly in the case of ryegrass at bulk densities of 1300–1500 kg m^–3.     

Microbial immobilization of cadmium released from CdO in the soil

The effect of microorganisms on the fate of Cd introduced into the soil as cadmium oxide (CdO) was investigated. Cadmium oxide (875 µg Cd per gram of soil) was added to -irradiated (sterile) and non-sterile soils. The soils were incubated for 90 days at 18 °C under aerobic conditions with moisture kept at 60% of water-holding capacity. Half of the samples in each treatment were supplemented with starch (0.5%, w/w) in order to stimulate microbial growth in the non-sterile soil. After various time intervals (7- or 10-day), soil samples from each treatment were extracted with deionized distilled water (ratio 1:40) or 0.25 M CaCl₂ (ratio 1:5). The results indicated that during the incubation period the amount of Cd extracted from the non-sterile soil with either solvent was markedly lower than that extracted from the -irradiated sterile control. The addition of starch to the non-sterile soil reduced the concentration of Cd in the 0.25 M CaCl₂ extracts without affecting the Cd-content in the water extracts. Short-term experiments in which Cd was added to the soil as a solution of Cd(NO₃)₂ indicated that irradiation did not affect the sorption of Cd to the soil. The addition of bacterial mass (1 mg of dry weight g^–1 soil) decreased the amount of Cd extracted with water as well as that extracted with 0.25 M CaCl₂. Under sterile conditions the solubility of CdO in soil extracts was higher than in the other extractants. The addition of glucose (0.5%, w/w) or a glucose/starch mixture (0.5%, w/w of each) to the sterile soil increased the amount of extractable Cd after a short incubation (18 h at 18 °C). The obtained results suggest that primarily physicochemical reactions are involved in dissolving CdO in the soil but that microbial activity may be responsible for the immobilization of the released metal.     

Effect of 2-hydroxybenzoate on the rate of naphthalene mineralization in soil

The effect of 2-hydroxybenzoate (2-OHB, salicylate) on the mineralization rate of [¹⁴C]naphthalene, the population density of naphthalene-degrading bacteria, and the concentration of genes encoding for naphthalene dioxygenase in a soil bacterial community was investigated. Six different concentrations of 2-OHB (10, 20, 50, 100, 150 and 200 g g^–1 soil) were tested in 100-g portions of soil. The addition of 10, 20 or 50 g 2-OHB g^–1 soil produced a general increase in total soil bacterial population density, whereas the addition of 100 g or 200 g 2-OHB g^–1 soil specifically increased the proportion of naphthalene degraders relative to the total population. The addition of 50 g 2-OHB g^–1 soil produced a fourfold increase (the maximum observed) in the rate of naphthalene mineralization relative to the rate in unamended soil. The concentration of 2-OHB ( 100 g/g) added to soil correlated with the population density of naphthalene degraders (r=0.961). Addition of up to 200 g 2-OHB g^–1 correlated with the abundance of DNA sequences homologous to known naphthalene dioxygenase genes (nahAB) (r=0.958). However, mineralization of [¹⁴C]naphthalene was stimulated significantly only by the addition of 50 g 2-OHB g^–1 soil. Results of the mineralization experiments were supported by the detection of nahAB mRNA extracted directly from soil. The specificity of the effect of 2-OHB on naphthalene biodegradation was confirmed in a control experiment using equivalent concentrations of 4-OHB which repressed naphthalene mineralization by about 50%. Addition of ammonium nitrate to the soil also increased the rate of naphthalene mineralization. Ammonium nitrate added together with 2-OHB reduced the mineralization enhancement effect of either compound alone. The study confirmed that specific induction of biodegradative genes can enhance chemical pollutant removal in situ. Correspondence to: O. A. Ogunseitan     

Metabolic responses of microbiota to diesel fuel addition in vegetated soil

The effects of trees and contamination on microbial metabolic activity, especially that of hydrocarbon degrading bacteria, were compared during phytoremediation to find which conditions increase diesel fuel removal. Diesel fuel utilisation, microbial extracellular enzyme activities and utilisation of Biolog ECO plate carbon sources by soil bacteria were determined during phytoremediation experiments consisting of two separate diesel applications. Diesel fuel removal after 28 days of second diesel application was 20–30% more than after the first application 1 year earlier. Soil microbiota utilised 26–31 of the 31 Biolog ECO plate carbon sources. Carbon source utilisation profiles indicated minor differences in microbiota in soil vegetated with pine compared to microbiota in soil vegetated with poplar. The potential maximum rates of aminopeptidase activity were 10–10² M AMC/h/g dry soil prior to and after second diesel application, except 14days after the second diesel addition, where the rates were at the scale of 10³M AMC/h/g dry soil. The potential maximum rates of esterase activity were 10³–10⁴M MUF/h/g dry soil. The presence of plants did not influence the activity of esterases. The utilisation of diesel by soil bacteria in Biolog MT2 plate assay was higher in contaminated soil, especially when vegetated, than in uncontaminated soil, measured both as lag times and maximum specific utilisation rates. MT2 plate assay detected the biological response after diesel fuel addition better than general activity methods.     

Some aspects of the chemistry of lithium in soils

Summary A method for the determination of exchangeable lithium using 0.5M NH₄Cl is described. The range of exchangeable Li in the fifty Papua New Guinea (PNG) soils analyzed was 0.002 to 0.409 gg^–1 in contrast to five Australian soils which ranged from 0.032 to 0.830 gg^–1. The PNG soils were divided into hill and alluvial soils with average exchangeable Li contents of 0.062 and 0.263 gg^–1 respectively. No significant correlation between total and exchangeable Li was found in either group of soils althoughr=0.67 for the comined data and was significant at the 5% level. From the analysis of three profiles exchangeable Li was found to be at least twice as high (0.27 gg^–1) in surface soils as in subsurface samples (0.10 gg^–1). The average value of the deeper subsoil samples was 0.18 ppm.R mode cluster analysis of the data for village garden soils collected on a sampling grid showed that exchangeable Li was more strongly assoicated with Ca and Mg than with pH, 0.05M EDTA soluble Zn, 0.5M NaHCO₃ soluble P or exchangeable Na and K. Computer constructed isographs using the analyses of grid samples from a garden illustrated the association between Li, Ca and Mg and the inverse association with Na.The correlation coefficient between Ca and Li in the ash of three food plants (Gnetum gnemon, Hibiscus abelmoschus andStenochlaena plustris) while not significant on an individual basis, was significant when the data was combined suggesting that the association between these elements in the soil may reflect an association in the ash returned to the soil when the garden was cleared. The correlation coefficient between soil exchangeable Li and Li in plant ash was positive, but not significant.Adsorption experiments over a five-day period demonstrated that Li was strongly adsorbed from solution. On average 63–75% of the adsorbed Li was fixed in a form which was not exchangeable with 0.5M NH₄Cl or soluble in 0.05M EDTA.     

Fate and effects of cadmium in an experimental marine ecosystem

Two recirculated marine seawater systems (capacities: 150 and 300 l) were used for the study on cadmium accumulation of biological filter sludge, by the musselMytilus edulis and the plaicePleuronectes platessa for a period of up to 300 days. In the contaminated system Cd concentrations varied from 2.5 to 7.0 g/l with a mean of 4.6±1.15 g/l (control: 1.04±0.46 g/l). Accumulation of Cd by the filter sludge from the control system as well as from the contaminated system was significant. Mean concentrations of control-and contaminated sludge over the experimental period were 2.01±0.86 ng Cd/mg dry wt and 9.98±3.55 ng Cd/mg dry wt respectively. Accumulation of Cd byM. edulis both in the control and in the contaminated system was considerable. After 163 days of exposure the whole body burden of mussels rose from 0.3 ng Cd/mg dry wt to around 10 ng Cd/mg dry wt in the controls and to 70 ng Cd/mg dry wt in the contaminated systems. Accumulation of Cd byP. platessa was analysed in backbone, fins, gills, liver, muscle (fillet), otolith and skin (dorsal and ventral) over a period of 280 days. Elevated Cd contents of livers from control specimens were noticed after 200 days and reached 1.75 ng Cd/mg dry wt in liver. There was considerable accumulation in the liver (maximum values: 3.0 ng Cd/mg dry wt) and gills (6.0 ng Cd/mg dry wt) of specimens from the contaminated system, Cd contents of plaice exposed for identical periods of time were very variable. Growth of plaice living in the contaminated system was at times significantly slower than that of the control group. Of the three biological objects tested-filter sludge,M. edulis, P. platessa—the mussel seemed to be the most sensitive indicator of elevated Cd-concentrations, while the reaction of the plaice was slow and less distinct.