Ageing of added copper in bentonite without and with humic acid

Abstract

The ageing of metals in soils plays an important role in assessing ecological risk and soil quality criteria, it therefore is necessary to understand the ageing processes. Using a sequential extraction procedure and a parabolic diffusion equation, the ageing of added copper(Cu) in bentonite without and with humic acid (HA) was investigated as a function of incubation time over one year. At the same time, the effect of pH on Cu ageing in bentonite with HA was also studied. The most labile Cu fractions (water-soluble Cu, Cu extracted by NH₄NO₃ and EDTA) gradually transformed into less extractable forms. The modelled diffusion equation suggested that the ageing processes were controlled by surface nucleation/precipitation and diffusion. In the presence of HA, the contribution from surface nuclea-tion/precipitation increased significantly, whereas that from diffusion decreased, this indicated the addition of HA significantly enhanced the short-term ageing by complexation with Cu ions, but strongly inhibited the further diffusion of Cu ions into interlayer of bentonite during long-term ageing owing to the more stable complexes formed on solid surface. With increasing pH in bentonite with HA, the apparent diffusion rate coefficient (D/r²) increased greatly, which showed that during long-term ageing pH played an important role in reducing the extractability as a result of the significant increase in residual Cu (RES-Cu), the most inert fraction, due to micropore diffusion.     

Radiation therapy for the management of painful bone metastases: Results from a randomized trial

AimThe aim of this study was to compare the effectiveness of two radiotherapy schedules in patients with bone metastases.BackgroundWe analyzed the need for re-irradiation, rates of pain control, pathological fractures, and functionality in patients randomized to single-fraction (8 Gy 1×) or multiple-fraction radiotherapy (3 Gy 10×) with at least 12 months follow-up, during five years. The hypothesis was that the two radiotherapy schedules are equally effective.Materials and methodsNinety patients with painful skeletal metastases were randomized to receive single fraction (8 Gy) or multiple fraction (3 Gy 10×) radiotherapy.ResultsIn the single-fraction group, seven pathological fractures occurred (15.5%) versus two (4.4%) in the multiple-fraction group. There was no statistically significant difference between the time it took to suffer a pathological fracture in both groups (p = 0.099). Patients in the single-fraction group received twelve re-irradiations (26.6%), four in the multiple-fraction group (8.8%), with no significant difference between time elapsed before the first re-irradiation (p = 0.438).ConclusionThis study shows no difference between the two groups for the majority of patients with painful bone metastases. Patients were followed up during five years, and the trial showed no disadvantage for 8 Gy 1× compared to 3 Gy 10×. Despite the fact that the pathological fracture rate is 3.75 times higher in the single-fraction group, this schedule is considered more convenient for patients and more cost-effective for radiotherapy departments.     

Nitrogen deposition promotes the production of new fungal residues but retards the decomposition of old residues in forest soil fractions

Atmospheric nitrogen (N) deposition has frequently been observed to increase soil carbon (C) storage in forests, but the underlying mechanisms still remain unclear. Changes in microbial community composition and substrate use are hypothesized to be one of the key mechanisms affected by N inputs. Here, we investigated the effects of N deposition on amino sugars, which are used as biomarkers for fungal‐ and bacterial‐derived microbial residues in soil. We made use of a 4‐year combined CO₂ enrichment and N deposition experiment in model forest ecosystems, providing a distinct ¹³C signal for ‘new’ and ‘old’ C in soil organic matter and microbial residues measured in density and particle‐size fractions of soils. Our hypothesis was that N deposition decreases the amount of fungal residues in soils, with the new microbial residues being more strongly affected than old residues. The soil fractionation showed that organic matter and microbial residues are mainly stabilized by association with soil minerals in the heavy and fine fractions. Moreover, the bacterial residues are relatively enriched at mineral surfaces compared to fungal residues. The ¹³C tracing indicated a greater formation of fungal residues compared to bacterial residues after 4 years of experiment. In contradiction to our hypotheses, N deposition significantly increased the amount of new fungal residues in bulk soil and decreased the decomposition of old microbial residues associated with soil minerals. The preservation of old microbial residues could be due to decreased N limitation of microorganisms and therefore a reduced dependence on organic N sources. This mechanism might be especially important in fine heavy fractions with low C/N ratios, where microbial residues are effectively protected from decomposition by association with soil minerals.     

Carbon sequestration potential of soils in southeast Germany derived from stable soil organic carbon saturation

Sequestration of atmospheric carbon (C) in soils through improved management of forest and agricultural land is considered to have high potential for global CO₂ mitigation. However, the potential of soils to sequester soil organic carbon (SOC) in a stable form, which is limited by the stabilization of SOC against microbial mineralization, is largely unknown. In this study, we estimated the C sequestration potential of soils in southeast Germany by calculating the potential SOC saturation of silt and clay particles according to Hassink [Plant and Soil 191 (1997) 77] on the basis of 516 soil profiles. The determination of the current SOC content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long‐term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional SOC. A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. A high proportion of sites with a high degree of apparent oversaturation revealed that in acidic, coarse‐textured soils the relation to silt and clay is not suitable to estimate the stable C saturation. A strong correlation of the C saturation deficit with temperature and precipitation allowed a spatial estimation of the C sequestration potential for Bavaria. In total, about 395 Mt CO₂‐equivalents could theoretically be stored in A horizons of cultivated soils – four times the annual emission of greenhouse gases in Bavaria. Although achieving the entire estimated C storage capacity is unrealistic, improved management of cultivated land could contribute significantly to CO₂ mitigation. Moreover, increasing SOC stocks have additional benefits with respect to enhanced soil fertility and agricultural productivity.     

Stable isotope analysis as a tool to monitor dietary trends in little penguins Eudyptula minor

Long‐term dietary monitoring of seabirds can be used to relate population fluctuations to at‐sea events. Stomach flushing is a conventional dietary monitoring technique, but has a number of disadvantages. Stable isotope analysis (SIA) is a less invasive method that provides unbiased dietary information over a longer period. We evaluated stable isotope analysis as a potential tool for monitoring long‐term little penguin Eudyptula minor diet. We determined diet composition during the chick feeding stage using stomach flushing and SIA at three separate colonies, using spatial variation in diet as a surrogate for potential temporal variation. Bayesian isotopic mixing models were generated for blood and feathers to evaluate their ability to discriminate broad‐scale (fish, squid, crustaceans) and fine‐scale (individual prey species) diet composition. Differences in stable carbon and nitrogen isotope ratios were found between colonies: broad‐scale isotopic mixing models predicted different proportional contributions of broad taxa (fish, cephalopod, crustacean) to diet than was indicated by stomach samples, reflecting the bias incurred by one‐off stomach contents analysis. Fine‐scale isotopic mixing models predicted proportional contributions of prey items with less certainty. Blood isotopic mixing models had narrower confidence intervals than models for feathers, but trends in δ¹⁵N for feathers mirrored those for blood. Our results suggest that relying on stomach contents analysis to detect shifts in prey consumption in little penguins could be very misleading, resulting in a less‐than‐complete idea of total prey consumption. SIA of little penguin tissues could be used to monitor dietary shifts across dissimilar taxa that may affect population numbers, but would fail to detect shifts between fish species.     

The alternative respiratory pathway mediates carboxylate synthesis in white lupin cluster roots under phosphorus deprivation

Plant adaptations associated with a high efficiency of phosphorus (P) acquisition can be used to increase productivity and sustainability in a world with a growing population and decreasing rock phosphate reserves. White lupin (Lupinus albus) produces cluster roots that release carboxylates to efficiently mobilize P from P‐sorbing soils. It has been hypothesized that an increase in the activity of the alternative oxidase (AOX) would allow for the mitochondrial oxidation of NAD(P)H produced during citrate synthesis in cluster roots at a developmental stage when there is a low demand for ATP. We used the oxygen‐isotope fractionation technique to study the in vivo respiratory activities of the cytochrome oxidase pathway (COP) and the alternative oxidase pathway (AOP) in different root sections of white lupins grown hydroponically with and without P. In parallel, AOX protein levels and internal carboxylate concentrations were determined in cluster and non‐cluster roots. Higher in vivo AOP activity was measured in cluster roots when malate and citrate concentrations were also high, thus confirming our hypothesis. AOX protein levels were not always correlated with in vivo AOP activity, suggesting post‐translational regulation of AOX.     

Bioavailability of Metals in Soil and Health Risk Assessment for Populations Near an Indian Chromite Mine Area

Soils contaminated with toxic metals may be environmental hazards and sources of exposure to human population. Soils in mining areas are among the most heavily contaminated by metals from the mining activity. This study was focused on metals of interest in bioavailability studies using single and sequential extraction methods. Results of geochemical fractionation suggest that changes in soil characteristics may enhance the mobilization of Cu, Cr, Zn, and Al. The observed metals’ availability pattern was Cr > Cu > Zn > Al. However, the pattern of total contents of metals in soils was Al > Cr > Zn > Cu. Risks to human adults and children from selected metals through soil ingestion was assessed in terms of incremental lifetime average daily dose (LADD), hazard quotient (HQ), and hazard index (HI). The estimated LADDs and HI were within acceptable reference doses and less than 1, respectively, indicating low risk to human populations from the studied metals through soil ingestion in the studied mine area. The generated data may be useful in remediation of contaminated soils with metals.     

Stable Isotope Evidence of Puma concolor (Felidae) Feeding Patterns in Agricultural Landscapes in Southeastern Brazil

We evaluated puma (Puma concolor) feeding patterns in southeastern Brazilian agricultural landscapes using carbon and nitrogen stable isotope analyses of hair collected from fecal samples (N = 64). We classified the samples into three groups: feeding patterns based on forest remnants, on the agricultural matrix or both. We observed a predominance of consumption of C₃ prey (~47% of individuals) in the area with the highest proportion of forest coverage. Conversely, C₄ prey were highly consumed (~40% of individuals) where the agricultural matrix was predominant. The δ¹³C values for pumas in both areas indicated that their food resources come from both forest remnants and the agricultural matrix and that some individuals preferentially consumed C₄ prey, indicating that food resources from the agricultural matrix make up most of their diet (~46% of prey individuals). The wide range of puma's δ¹⁵N values in both areas indicated a diet based on different types of prey. However, the C₄ group had higher values, indicating that both pumas and their prey feed on enriched resources from the agricultural matrix. The results confirm the high behavioral plasticity of pumas in using highly anthropogenic habitats. The stable isotope analyses conducted in this study yielded new information on large carnivore trophic ecology that might be useful in the development of new conservation strategies in disturbed areas.     

Identification of metabolites from liquid chromatography–coulometric array detection profiling: Gas chromatography–mass spectrometry and refractionation provide essential information orthogonal to LC–MS/microNMR

Liquid chromatography–coulometric array detection (LC–EC) is a sensitive, quantitative, and robust metabolomics profiling tool that complements the commonly used mass spectrometry (MS) and nuclear magnetic resonance (NMR)-based approaches. However, LC–EC provides little structural information. We recently demonstrated a workflow for the structural characterization of metabolites detected by LC–EC profiling combined with LC–electrospray ionization (ESI)–MS and microNMR. This methodology is now extended to include (i) gas chromatography (GC)–electron ionization (EI)–MS analysis to fill structural gaps left by LC–ESI–MS and NMR and (ii) secondary fractionation of LC-collected fractions containing multiple coeluting analytes. GC–EI–MS spectra have more informative fragment ions that are reproducible for database searches. Secondary fractionation provides enhanced metabolite characterization by reducing spectral overlap in NMR and ion suppression in LC–ESI–MS. The need for these additional methods in the analysis of the broad chemical classes and concentration ranges found in plasma is illustrated with discussion of four specific examples: (i) characterization of compounds for which one or more of the detectors is insensitive (e.g., positional isomers in LC–MS, the direct detection of carboxylic groups and sulfonic groups in ¹H NMR, or nonvolatile species in GC–MS), (ii) detection of labile compounds, (iii) resolution of closely eluting and/or coeluting compounds, and (iv) the capability to harness structural similarities common in many biologically related, LC–EC-detectable compounds.