Radiocaesium in an organic soil and the effect of treatment with the fungicide ‘Captan’

Soil fungi accumulate radiocaesium from contaminated soil and it has been hypothesised that this may alter the plant availability and movement of the radionuclide in soil. The effect of twice-monthly addition of an aqueous suspension of the fungicide ‘Captan’ on the changes in a peaty podzol soil at 2 sites, contaminated 2 or 3 years earlier by the injection of ¹³⁴Cs, has been quantified. The sites had different soil acidity and vegetation cover. The less acid soil (pH_water 5.0) had been improved by the addition of lime and fertilizer and was reseeded with grass and clover. The more acid soil (pH_water 3.8) was under hill grasses, herbs and heather. On both sites the addition of fungicide did not alter the amount or concentration of radiocaesium in plant material sampled monthly or the depth distribution of radiocaesium in the soil profile. The concentration of the fungal constituent, ergosterol, in the soil, measured monthly, was unaffected by the fungicide treatment but evidence was obtained from a pot experiment to show that ergosterol decomposes slowly in cold, wet soils. On the more acid soil, two weeks after the last application of fungicide, there was a decline in active fungi as measured by fluorescein diacetate staining. Chloroform fumigation of the more acid soil resulted in a small increase in the amount of ¹³⁴Cs exchangeable with 1 M ammonium acetate. Radiocaesium in seven different fungi grown in pure culture was found to be almost entirely extractable (> 95%) with 1 M ammonium acetate. Another, Amanita rubescens, showed some retention and 88% was extractable. These findings do not preclude the fungal biomass as an important soil component controlling plant availability of radiocaesium from acid, organic soils by maintaining radiocaesium in a biological cycle, but make it unlikely that any fixation by fungi in a chemical sense is involved.     

Species–soil associations, disturbance, and nutrient cycling in an Australian tropical rainforest

Resource availability and disturbance are important factors that shape the composition, structure, and functioning of ecosystems. We investigated the effects of soil fertility and disturbance on plant–soil interactions and nutrient cycling in a diverse tropical rainforest. Our goal was to determine how common soil specialisation is among species and how plant–soil interactions affect ecosystem functioning in the presence of disturbance. Most species (59%) showed significant fidelity to either fertile (basalt) or infertile (schist) soils. Obligate schist specialists (six species) contributed 39 and 37% to total stand-level basal area and aboveground net primary productivity, respectively. High nutrient use efficiency of schist specialists reduced the rates of within-stand nutrient cycling through the production of nutrient-poor plant tissues and litter. Although forests on schist soils had higher basal area and similar rates of productivity to forests on basalt, uptake of Mg, K, P, and N were markedly less on schist than on basalt, particularly after a cyclone disturbance. Stands on schist soils were also less affected by the cyclone and, as a result, contributed less (ca. 50%) Mg, K, P, and N inputs to the forest floor (via litterfall) than stands on basalt soils. System “openness” (i.e. the risk of nutrient loss) from cyclone-affected basalt forests was minimised by high rates of uptake following disturbance and large effective cation exchange capacities of soils. Soil–plant-disturbance interactions are likely to engender different fitness-enhancing strategies on fertile and infertile soils, possibly leading to the development and/or maintenance of diversity in rainforests.     

Soil hydraulic manipulation and organic amendment for the enhancement of selenium volatilization in a soil–pickleweed system

Biological volatilization of selenium (Se) in contaminated areas represents an environmentally friendly phytoremediation approach. Implementation of phytovolatilization technology for the remediation of Se-contaminated soils or sediments is oftentimes limited by its low remediation efficiency under field conditions. This greenhouse study determined the feasibility of manipulating soil organic content and hydraulic conditions in a soil–pickleweed (Salicornia bigelovii) system for the enhancement of Se volatilization. Based on annual shoot biomass production rate under field conditions (approximately 1.5 kg m⁻²), the addition of pickleweed shoot tissues to the soil surface resulted in 2.2-fold more biogenic volatile Se than the control, up to 251.6 ± 140.5 μg m⁻² d⁻¹. Selenium volatilization was significantly reduced at a soil water potential of −25 kPa, but substantially increased after re-irrigation to 0 kPa. In a 42-day experiment, the rate of Se volatilization was significantly correlated with soil water potential (P < 0.0001). Findings from this study demonstrate that Se volatilization be substantially enhanced by amending soil with pickleweed residues and by creating wetting and drying cycles that can be monitored with soil water potential probes in the field.     

Assay of Δ1-piperideine-2-carboxylate and synthesis of l-[14C]pipecolate from dl-[14C]pipecolate

Four assay methods were tested for the measurement of Δ¹-piperideine-2-carboxylate, a proposed alicyclic ketimino acid intermediate in the pathway of lysine metabolism to l-pipecolate, and the product of d-amino acid oxidase on d-pipecolate. The method using Δ¹-piperideine-2-carboxylate reductase from Pseudomonas putida was found to be most sensitive and specific. Measurement of Δ¹-piperideine-2-carboxylate by reduction with NaBH₄ and ninhydrin assay of the resultant pipecolate, by direct acidic ninhydrin assay, and by o-aminobenz-aldehyde assay were less desirable because of lower sensitivity and specificity. Two synthetic methods for preparing l-[¹⁴C]pipecolate from the racemic dl-[¹⁴C]pipecolate were investigated. Incubation of dl-[¹⁴C]pipecolate with a combination of d-amino acid oxidase and Δ¹-piperideine-2-carboxylate reductase or d-amino acid oxidase and NaBH₄ totally inverted the d-isomer to the l-isomer, with $\text{Δ}{}^1\text{-[}{}^{14}\text{C]piperideine-2-carboxylate}$ as an intermediate in each cycle of interconversion. No purification except desalting through a Dowex 50 (H⁺) column was necessary in order to recover l-[¹⁴C]pipecolate in pure form. The yield was 95–97% compared to <50% in the conventional method.     

Incorporation of [14C]glucosamine and [14C]leucine into mouse kidney β-glucuronidase induced by gonadotrophin

Male BALB/C mice were injected intraperitoneally with 2.5 i.u. of gonadotrophin. After the injection, increase of β-glucuronidase activity was first observed in the microsomal fraction. By 36h 45–50% of the total homogenate activity was found in the microsomal fraction compared with 20–25% in the control microsomal fraction. From 36 to 80h not only microsomal β-glucuronidase but also lysosomal β-glucuronidase increased progressively. After 69h stimulation with 2.5 i.u. of gonadotrophin, d-[1-¹⁴C]glucosamine or l-[U-¹⁴C]leucine was injected intraperitoneally. After a further 3h the kidneys were homogenized and five particulate fractions were prepared by differential centrifugation. The β-glucuronidase in the microsomal and lysosomal fractions was released respectively by ultrasonication and by freezing and thawing treatment. The enzyme was purified by organic-solvent precipitation and by sucrose-density-gradient centrifugation. The results demonstrated the incorporation of these two labels into the mouse renal β-glucuronidase. The microsomal β-glucuronidase was much more radioactive than the lysosomal enzyme and approx. 80% of the newly synthesized enzyme appeared in microsomes and approx. 20% of that was found in lysosomes at this period. These results suggest that the mouse renal β-glucuronidase is a glycoprotein and that the newly synthesized enzyme is transported from endoplasmic reticulum to lysosomes.     

Incorporation of label from d-β-hydroxy-[14C]butyrate and [3-14C]acetoacetate into amino acids in rat brain in vivo

The metabolism of ketone bodies by rat brain was studied in vivo. Rats starved for 48h were given either d-beta-hydroxy[3-(14)C]butyrate or [3-(14)C]acetoacetate by intravenous injection and killed after 3 or 10min. Total radioactivity in the acid-soluble material of the brain and the specific radioactivities of the brain amino acids glutamate, glutamine, aspartate and gamma-aminobutyrate were determined. A group of fed animals were also given d-beta-hydroxy[3-(14)C]butyrate. In the brains of all animals (14)C was present in the acid-soluble material and the specific radioactivity of glutamate was greater than that of glutamine.     

Fate and dynamics of recently fixed C in pasture plant–soil system under field conditions

The flow of photosynthetically fixed C from plants to selected soil C pools was studied after ¹³CO₂ pulse labeling of pasture plants under field conditions, dynamics of root-derived C in soil was assessed and turnover times of the soil C pools were estimated. The transport of the fixed C from shoots to the roots and into the soil was very fast. During 27 h, net C belowground allocation reached more than 10% of the fixed C and most of the C was already found in soil. Soil microbial biomass (C_MIC) was the major sink of the fixed C within soil C pools (ca 40–70% of soil ¹³C depending on sampling time). Significant amounts of ¹³C were also found in other labile soil C pools connected with microbial activity, in soluble organic C and C associated with microbial biomass (hot-water extract from the soil residue after chloroform fumigation-extraction) and the ¹³C dynamics of all these pools followed that of the shoots. When the labelling (2 h) finished, the fixed ¹³C was exponentially lost from the plant–soil system. The loss had two phases; the first rapid phase corresponded to the immediate respiration of ¹³C during the first 24 h and the second slower loss was attributable to the turnover of ¹³C assimilated in C_MIC. The corresponding turnover times for C_MIC were 1.1 days and 3.4 days respectively. Such short turnover times are comparable to those measured by growth kinetics after the substrate amendment in other studies, which indicates that microbial growth in the rhizosphere is probably not limited by substrate availability. Our results further confirmed the main role of the soil microbial community in the transformation of recently fixed C, short turnover time of the easily degradable C in the rhizosphere, and its negligible contribution to more stable soil C storage.     

A procedure for the synthesis of p-fluorosulfonyl[14C]-benzoyl-5′-adenosine with [14C] in the benzoyl moiety

Carboxy-p-fluorosulfonyl[¹⁴C]benzoyl-5′-adenosine has been synthesized with the radiolabel ultimately derived from carboxy-p-amino[¹⁴C]benzoic acid by a synthetic route employing four reaction steps. Starting with 1 mmol of p-amino[¹⁴C]benzoic acid, p-fluorosulfonyl[¹⁴C]benzoyl-5′-adenosine is obtained with an overall yield of 25–30%.     

In vitro evaluation of co-exposure of arsenium and an organic nanomaterial (fullerene, C₆₀) in zebrafish hepatocytes

Taking into account the concept of the "Trojan Horse", where contaminants may have its entry into specific organs potentiated by its association with nanomaterials, the aim of this study was to analyze the joint toxic effects induced by an organic nanomaterial, fullerene (C(60)) with the metalloid arsenic (As(III)). Hepatocytes of zebrafish Danio rerio were exposed to As(III) (2.5 or 100 μM), C(60) or As+C(60) for 4h, not altering cells viability. Intracellular reactive oxygen species concentration was reduced in cells exposed only to the C(60) (1mg/L) and in the treatment of 100 μM As(III)+C(60). Co-exposure with C(60) abolished the peak of the antioxidant glutathione (GSH) registered in cells exposed to the lowest As(III) concentration (2.5 μM). A similar result was observed in terms of lipid damage (TBARS). Total antioxidant capacity was significantly higher at both As(III) concentrations co-exposed to C(60) when compared with the control group. Activity of glutathione-S-transferase omega, a limiting enzyme in the methylation pathway of As(III), was reduced in the 100 μM As(III)+C(60) treatment. Cells co-exposed to C(60) had a significantly higher accumulation of As(III), showing a "Trojan Horse" effect which did not result in higher cell toxicity. Instead, co-exposure of As(III) with C(60) showed to reduce cellular injury.     

The effect of chemical fertilizer on soil organic carbon renewal and CO2 emission—a pot experiment with maize

Background and Aims

Previous studies have clearly shown substantial increases of soil organic carbon (SOC) in agricultural soils of Yellow River reaches. Those soils did not receive organic fertilizer input, but did receive chemical fertilizer inputs. Thus, to investigate the hypothesis that the observed SOC increases were driven by chemical fertilizer additions, a maize pot experiment was conducted using a Fluvisol that developed under C₃ vegetation in the Yellow River reaches.

Methods

Using the natural ¹³C abundance method we calculated the SOC renewal ratio (C _renewal), and separated total soil organic carbon (TOC) into maize-derived soil organic carbon (SOC_maize) and original soil organic carbon (SOC_original). Carbon dioxide fluxes and microbial biomass carbon (MBC) were determined by closed chamber method and fumigation-extraction method, respectively. The experiment included five treatments: (1) NPK: application of chemical fertilizer NPK; (2) NP, application of chemical fertilizer NP; (3) PK: application of chemical fertilizer PK; (4) NK, application of chemical fertilizer NK; and (5) CK: unfertilized control.

Results

Fertilization increased maize biomass (including grain, straw and root), TOC, C _renewal, SOC_maize, maize-derived carbon (MDC: including SOC_maize, and root and stubble biomass carbon) and MBC, and these values among the treatments ranked NPK>NP>PK>NK>CK. The C _renewal was 5.54–8.50% across the treatments. Fertilization also increased soil CO₂ emission (including root respiration and SOC_original decomposition), while the SOC_original decomposition during the maize growing season only amounted to 74.0–93.4 and 33.5–46.1% of SOC_maize and MDC among the treatments, respectively. Thus input was larger than export, and led to SOC increase. Maize grain and straw biomass were positively and significantly correlated with soil δ¹³C, TOC, C _renewal, SOC_maize, MDC and MBC.

Conclusions

The study suggests that chemical fertilizer application could increase C _renewal by increasing crop-derived C and accelerating original SOC decomposition, and that as long as a certain level of crop yield or aboveground biomass can be achieved, application of chemical fertilizer alone can maintain or increase SOC level in Fluvisol in the Yellow River reaches.     

Immunotoxic effect of Benzo[α]Pyrene and chrysene in juvenile white shrimp Litopenaeus vannamei

The effects of benzo(a)pyrene (Bap) (0.03, 0.3 and 3 μg L^?1) and chrysene (CHR) (0.3, 2.1 and 14.7 μg L^?1) on the function of the immune system of juvenile white shrimp Litopenaeus vannamei were determined under laboratory conditions. This included the total hemocyte count (THC) in the hemolymph, phagocytic activityand pro-phenoloxidase (pro-PO) activity of the hemocyte, phenoloxidase (PO) activity, α₂-macroglobulin (α₂-M) activity, bacteriolytic activity and antibacterial activity in the hemolymph. The results showed that BaP and CHR could inhibit the immune function of L. vannamei significantly under high concentration BaP and CHR exposure. The results of this study indicated that the immunotoxicity of PAHs in a descending order was BaP>CHR. Moreover, the results indicated the THC in hemolymph, pro-PO activity and phagocytic activity of hemocyte, and bacteriolytic activity in hemolymphcould be used as potentially suitable biomarkersfor early warning indication of PAHs toxicity, this could provide useful information for toxic risk assessment of environmental pollutants.     

Differential effects of veratridine and calcium on the release of [3H]noradrenaline and [14C]α-aminoisobutyrate from rat brain cortex slices

The efflux of [³H]noradrenaline (NA) and of the non transmitter, non metabolizable, amino acid [¹⁴C]α-aminoisobutyrate (AIB), was followed simultaneously from superfused rat brain cortex thin slices, that had been preloaded with those substances. Short (2 min) “pulses” of increasing veratridine concentrations were applied at 10 min intervals. When calcium in the superfusion fluid was 1 mM, [³H]NA efflux increased progressively with pulses of 1, 3, 10 and 30 μM veratridine, but further increase to 100 μM resulted in a decrease of the induced ³H-efflux. Veratridine-enhanced [³H]NA efflux decreased considerably in 0.1 mM calcium and was virtually suppressed when no calcium was added to the superfusion fluid. In 1 mM calcium, the efflux of [¹⁴C] AIB was increased progressively by pulses of 10, 30 and 100 μM veratridine, but no increase in efflux was seen with 1 or 3 μM drug. In 0.1 mM, or without added calcium, the induced efflux of [¹⁴C]AIB was markedly increased. Similar findings were seen when a long (10 min) pulse of 10 μM veratridine was given. After such long pulses there was a rapid return of AIB efflux to pre-veratridine levels if calcium was 1 mM, but in the absence of added calcium, the return to baseline levels of both [³H]NA and, especially, that of [¹⁴C]AIB efflux, was greatly impaired. The veratridine enhanced efflux of both NA and AIB was entirely blocked by 1 μM tetrodotoxin.     

Changes in soil organic carbon and total nitrogen after 28 years grassland afforestation: effects of tree species, slope position, and soil order

The effect of conversion of grassland to woodland on organic carbon (OC) and total nitrogen (TN) has significance for global change, land resource use and ecosystem management. However, these effects are always variable. Here, we show results of a study in an arid area in China on profile distribution of OC and TN in soils covered by two different woody tree canopies and outer canopy space (grassland between woody plant canopies). The soils were at various slope positions (upper, middle and lower slopes) for Chinese pine (Pinus tabulaeformis) and Korshrinsk peashrub (Caragana korshinskii) lands, and of different soil orders (Castanozems, Skeletal, Loessial and Aeolian soils). The objectives were to relate the effects of land use change on OC and TN to slope position and soil order. Soil OC and TN were significantly larger at Korshrinsk peashrub slope locations than at Chinese pine slope locations. Soil OC and TN were small at the lower slope position for Korshrinsk peashrub, however, they were largest at the middle slope for Chinese pine. Korshrinsk peashrub always increased soil OC and TN under brush canopy at the three slope positions, while Chinese pine increased them at lower slopes and decreased them at upper slopes. For the soil types, OC and TN in Korshrinsk peashrub land were in the order of Castanozems > Skeletal > Loessial > Aeolian soils. Korshrinsk peashrub also increased OC and TN under brush canopy in the four soils. Our results indicated that soil OC and TN in canopy soils differed greatly from associated values in the outer canopy soils, and the effects of grassland afforestation varied significantly with tree species, slope position, and soil type. Therefore, we suggest that differentiating such factors can be an effective approach for explaining variances in OC and N changes caused by land use conversion.     

Black carrot polyphenols: effect of processing,storage and digestion—an overview

Black carrots represent a valuable source of polyphenols, in particular anthocyanins and phenolic acids, and has attracted the attention of the scientific community especially due to the unique profile of anthocyanin compounds, which are well distinguished for their role in health promotion and prevention of chronic diseases. Black carrots are often not consumed as such, instead they are processed into other products. In general, processed products of black carrot are stored for long term and the polyphenols are susceptible to degradation during storage. In addition, it is also important to determine how the digestion process affects polyphenols as this will, in turn, affect their bioavailability. Accordingly, the potential health-promoting effects of black carrot polyphenols depend on their processing history and their stability during storage as well as their absorption in the gastrointestinal tract. In this perspective, this review provides an overview of the findings on the effects of processing, storage and digestion on black carrot polyphenols.     

The effect of counterion,water concentration,and stirring on the stability of subtilisin BPN′ in organic solvents

The stability of subtilisin BPN′ in organic solvents or cosolvent/water mixtures was studied as a function of the type and concentration of counterion at the time of freeze-drying, water concentration, and stirring speed/method. It was found that the enzyme is stabilized by high concentrations of counterion, at least at very high cosolvent concentrations. The type of counterion also has a remarkable impact on the enzyme stability; at high concentrations of DMF (dimethylformamide), multivalent counterions with low solubility in organic solvents are far superior to monovalent, soluble ones. Sodium citrate is the best salt tested in terms of enzyme stability, increasing the half life of the enzyme better than a millionfold over Tris in 99% DMF. The stability of the enzyme was found to have a complex dependence on the amount of water in the DMF. Enzyme lyophilized from the sodium phosphate displays a stability minimum at about 90% DMF, while enzyme lyophilized from Tris becomes increasingly unstable from 30% to 99% DMF, without inflection. Vigorous stirring with a magnetic stir bar, which broke apart the enzyme particles, was found to be extremely deleterious to enzyme stability, while swirling the enzyme with a wrist-action stirrer, which did not grind the enzyme particles, had no effect. Explanations for this are discussed.     

Variance components of the respiration rate and chemical characteristics of soil organic layers in Niepołomice Forest, Poland

Respiration rates and chemical characteristics of soil organic layers were measured at 40 experimental plots, 5 sampling sites per plot, in a moderately polluted Niepoomice Forest, S. Poland. The respiration rate was positively related to pH, water content and concentrations of Ca and K, and negatively to N_tot, Zn and Pb (p < 0.001 for all variables). No significant correlation was found between the respiration rate and Na, Cu or Cd (p > 0.25 in all cases). The regression model explained 73% of the total variance. Analysis of variance components revealed that ca. 35% of the total variance in the respiration rate can be explained by the vegetation types covering the area: oak-hornbeam vs. pine-oak forests. The next 40% was explained by the variability between sampling plots and the remaining 25% by within-plot variability among sampling sites. Similar results were obtained for water content. The variance in pH was split 30%:39%:31% between vegetation types:plots:sampling sites. No variance in Ca and Na was explained by the forest type, and approximately half of the variance was due to between-plot and half to within-plot variability. In contrast, potassium concentration differed between forest types (58% variance explained), more than 25% of total variance was due to between-plot variability and only 15% due to within-plot variability. For Zn the results were 1%, 66% and 33%, for Cu 0%, 38% and 62%, for Pb 48%, 18% and 34%, and for Cd 0%, 33% and 67%, respectively. The study clearly shows (1) substantial variance in some soil characteristics between sampling sites and (2) a different split of variance among spatial scales for different soil characteristics.     

Disposition of [4-14C]oestradiol-l7β in the isolated perfused brain of the rat

[4-¹⁴C] Oestradiol-17β was perfused through isolated brains of male and ovariectomized female rats. Two different perfusion media were used. The uptake of oestradiol-17β was higher in female brains, the highest concentrations being found in the hypophysis and hypothalamus. Oestradiol-17β was metabolized to a greater extent by female brains, the most important metabolite being oestrone. Additionally, 2-hydroxyoestradiol-17β, 6ζ-hydroxyoestradiol-17β, and 7α-hydroxyoestradiol-17β were found; 7α-hydroxyoestrone and another polar metabolite could not be definitely identified. Quantitatively, 2-hydroxylation was no more important than hydroxylation at C atom 6 or 7.