Organic matter stabilization in soil microaggregates: implications from spatial heterogeneity of organic carbon contents and carbon forms

This study investigates the spatial distribution of organic carbon (C) in free stable microaggregates (20–250 μm; not encapsulated within macroaggregates) from one Inceptisol and two Oxisols in relation to current theories of the mechanisms of their formation. Two-dimensional micro- and nano-scale observations using synchrotron-based Fourier-transform infrared (FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy yielded maps of the distribution of C amounts and chemical forms. Carbon deposits were unevenly distributed within microaggregates and did not show any discernable gradients between interior and exterior of aggregates. Rather, C deposits appeared to be patchy within the microaggregates. In contrast to the random location of C, there were micron-scale patterns in the spatial distribution of aliphatic C–H (2922 cm⁻¹), aromatic C=C and N–H (1589 cm⁻¹) and polysaccharide C–O (1035 cm⁻¹). Aliphatic C forms and the ratio of aliphatic C/aromatic C were positively correlated (r ² of 0.66–0.75 and 0.27–0.59, respectively) to the amount of O–H on kaolinite surfaces (3695 cm⁻¹), pointing at a strong role for organo-mineral interactions in C stabilization within microaggregates and at a possible role for molecules containing aliphatic C-H groups in such interactions. This empirical relationship was supported by nanometer-scale observations using NEXAFS which showed that the organic matter in coatings on mineral surfaces had more aliphatic and carboxylic C with spectral characteristics resembling microbial metabolites than the organic matter of the entire microaggregate. Our observations thus support models of C stabilization in which the initially dominant process is adsorption of organics on mineral surfaces rather than occlusion of organic debris by adhering clay particles.     

Applications of chemically defined diets to the solution of nutrition problems

Summary Chemically defined amino acid diets have been developed for most laboratory and meat-producing animal species as well as for humans. In many cases, growth performance of animals fed these diets equals that obtained with standard intact-protein diets. The pattern of both essential and nonessential amino acids is critical to obtaining excellent voluntary food intake. Other factors such as carbohydrate and fat type and level, acid-base balance (i.e., cation-anion ratio), and texture are important to the success of purified diets. Chemically defined diets provide amino acids, mineral elements and vitamins in forms that are maximally bioavailable. Also, virtually any nutrient can be manipulated at will for studies of a) requirements, b) bioavailability, c) factors affecting requirements and bioavailability, d) nutrient-nutrient interrelationships, e) nutrientdrug or nutrient-toxin interrelationships, f) absorption phenomena and g) efficiency and priority aspects of nutrient utilization. Requirements for essential nutrients are generally lower with purified diets than for practical diets because the nutrients in the former are more bioavailable, but also because purified diets generally lack antagonizing factors such as phytate and soluble fiber. That chemically defined diets for pigs, rats and dogs yield such excellent rates of growth suggests that a specific peptide requirement many not exist for these species. Also, this suggests that all known nutrients necessary for maximal growth must be present in the diet. Whether additional nutrients, or different levels, may be necessary for optimal health and immunocompetency, or for maximal life span, needs further study.Text of an invited paper presented at the 2nd International Congress on Amino Acids and Analogues, Vienna, Austria. August 8, 1991.     

Application of the PM6 method to modeling the solid state

The applicability of the recently developed PM6 method for modeling various properties of a wide range of organic and inorganic crystalline solids has been investigated. Although the geometries of most systems examined were reproduced with good accuracy, severe errors were found in the predicted structures of a small number of solids. The origin of these errors was investigated, and a strategy for improving the method proposed. Figure Detail of Structure of Dihydrogen Phosphate in KH₂PO₄ (upper pair) and in (CH₃)₄NH₂PO₄. (Footnote): X-ray structures on left, PM6 structure on right. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

湖北白龙洞遗址骨化石表面的黑色膜壳状物质

本文采用扫描电镜/能谱、X-射线衍射、红外光谱分析等不同检测方法,对湖北郧西县白龙洞红色黏土地层中出土的骨化石表面黑色膜壳状物质进行检测分析。分析结果为骨化石表面黑色膜壳层中含有碳羟磷灰石[Ca10(PO4)3(CO3)3(OH)2]、方解石(CaCO3),以及菱铁矿(FeCO3)、赤铁矿(Fe2O3)、磷铁矿[Fe25(PO4)14(OH)24]等。其中显色物相主要为菱铁矿、赤铁矿与磷铁矿的共生沉积物。菱铁矿、赤铁矿与磷铁矿三者共生, 使骨化石表面膜壳状矿物质层整体颜色呈现为黑色。该层黑色膜壳状矿物质层的形成原因, 与化石周围土壤中的CO32-和Fe有关。该层黑色膜壳状矿物质的存在, 对红色黏土中骨化石长期保存有一定保护作用, 它能阻隔和减轻埋藏环境中酸性腐蚀、地层挤压等自然原因对化石标本造成破坏, 因此也使骨化石能够保存得较为完整。     

Bone and faecal minerals and scanning electron microscopic assessments of femur in rats fed phytic acid extract from sweet potato (<Emphasis Type="Italic">Ipomoea batatas</Emphasis>)

Phytic acid was extracted from sweet potato (Ipomoea batatas) and fed to Wistar rats with or without zinc for 3 weeks. Animals were then sacrificed and bone and faecal minerals were assessed. The ultra-structure of the bones was examined via scanning electron microscopy. Phytic acid extract or commercial phytic acid supplemented diets (D + Zn + PE or D + PE) displayed reduced bone calcium levels (101.27 ± 59.11 and 119.27 ± 45.36 g/kg) compared to the other test groups. Similarly, reduced calcium were observed in the control groups (D + Zn and D) fed formulated diets with or without zinc supplementation (213.14 ± 15.31 and 210 ± 6.88 g/kg) compared to the other test groups. The group fed supplemented commercial phytic acid diet (D + CP) demonstrated the lowest femur magnesium (3.72 ± 0.13 g/kg) while the group fed phytic acid extract supplementation (D + PE) recorded the highest level (4.84 ± 0.26 g/kg) amongst the groups. Femur iron was highest in the group fed commercial phytic acid supplemented diet (D + CP −115.74 ± 2.41 g/kg) compared to the other groups. Faecal magnesium levels were significantly higher in the two test groups fed phytic acid extract with or without zinc (D + Zn + PE or D + PE) compared to all other groups. All the groups which had phytic acid supplemented diets had significantly thinner bone in the trabecular region, compared to the groups fed formulated diet or zinc supplemented formulated diet (D or D + Zn). These observations suggest that the consumption of foods high in phytic acid may contribute to a reduction in the minerals available for essential metabolic processes in rats.     

Competition for minerals between Acanthocephalus lucii and its definitive host perch (Perca fluviatilis)

Concentrations of various essential and toxic elements (Ba, Ca, Co, Cu, Fe, Mg, Mn, Sr, Zn and Al, Ag, Cd, Cr, Ni, Pb, Tl) were analysed by inductively coupled plasma mass spectrometry in the acanthocephalan Acanthocephalus lucii and in different tissues of its host Perca fluviatilis. Nearly all the elements were found in significantly higher concentrations in the acanthocephalan than in the host tissues. Spearman correlation analysis revealed several strong inter-element associations within the organs of perch and within the parasites. Furthermore, statistical analysis revealed different competitive interactions. The concentrations of several essential elements (Ba, Ca, Fe, Mn, Sr and Zn) within the parasites decreased with an increasing number or weight of worms inside the intestine of the host. Additionally, the levels of some elements in the perch liver were negatively correlated with the weight of A. lucii in the intestine. Thus, it emerged that not only is there competition for essential elements between acanthocephalans inside the gut but there is also competition for these elements between the host and its parasites.     

Life cycle assessment in the minerals and metals sector: a critical review of selected issues and challenges

Background, aim and scope

The mining sector provides materials that are essential elements in a wide range of goods and services, which create value by meeting human needs. Mining and processing activities are an integral part of most complex material cycles so that the application of life cycle assessment (LCA) to minerals and metals has therefore gained prominence. In the past decade, increased use of LCA in the mineral and metal sector has advanced the scientific knowledge through the development of scientifically valid life cycle inventory databases. Though scientifically valid, LCA still needs to depend on several technical assumptions. In particular, measuring the environmental burden issues related to abiotic resource depletion, land use impacts and open-loop recycling within the LCA are widely debated issues. Also, incorporating spatial and temporal sensitivities in LCA, to make it a consistent scientific tool, is yet to be resolved. This article discusses existing LCA methods and proposed models on different issues in relation to minerals and metals sector.

Main features

A critical review was conducted of existing LCA methods in the minerals and metals sector in relation to allocation issues related to indicators of land use impacts, abiotic resource depletion, allocation in open-loop recycling and the system expansions and accounting of spatial and temporal dimension in LCA practice.

Results

Evolving a holistic view about these contentious issues will be presented with view for future LCA research in the minerals and metals industry. This extensive literature search uncovers many of the issues that require immediate attention from the LCA scientific community.

Discussion

The methodological drawbacks, mainly problems with inconsistencies in LCA results for the same situation under different assumptions and issues related to data quality, are considered to be the shortcomings of current LCA. In the minerals and metals sector, it is important to increase the objectivity of LCA by way of fixing those uncertainties, for example, in the LCA of the minerals and metals sector, whether the land use has to be considered in detail or at a coarse level. In regard to abiotic resource characterisation, the weighting and time scales to be considered become a very critical issue of judgement. And, in the case of open-loop recycling, which model will best satisfy all the stake holders? How the temporal and spatial dimensions should be incorporated into LCA is one of the biggest challenges ahead of all those who are concerned. Addressing these issues shall enable LCA to be used as a policy tool in environmental decision-making. There has been enormous debate with respect to on land use impacts, abiotic resource depletion, open-loop recycling and spatial and temporal dimensions, and these debates remain unresolved. Discussions aimed at bringing consensus amongst all the stake holders involved in LCA (i.e. industry, academia, consulting organisations and government) will be presented and discussed. In addition, a commentary of different points of view on these issues will be presented.

Conclusions

This review shall bring into perspective some of those contentious issues that are widely debated by many researchers. The possible future directions proposed by researchers across the globe shall be presented. Finally, authors conclude with their views on the prospects of LCA for future research endeavours.

Recommendations and outlook

Specific LCA issues of minerals and metals need to be investigated further to gain more understanding. To facilitate the future use of LCA as a policy tool in the minerals and metals sector, it is important to increase the objectivity with more scientific validity. Therefore, it is essential that the issues discussed in this paper are addressed to a great detail.     

Molecular cloning,characterization and mRNA expression of selenium-dependent glutathione peroxidase from abalone Haliotis discus hannai Ino in response to dietary selenium,zinc and iron

A novel selenium-dependent glutathione peroxidase (Se-GPX) was cloned from abalone Haliotis discus hannai Ino (HdhGPx) by homology cloning with degenerate primers and RACE techniques. The full length of HdhGPx cDNA was 963 bp with a 669 bp open reading frame (ORF) encoding 222 amino acids and a 101 bp eukaryotic selenocysteine insertion sequence (SECIS) in 3′ untranslated region (UTR). It was showed that HdhGPx has a characteristic codon at ²³⁵TGA²³⁷ that corresponds to selenocysteine (SeC) as U₇₂. Sequence characterization revealed that HdhGPx contains a characteristic GPx signature motif 2 (₉₆LGLPCNQF₁₀₃), an active site motif (₁₇₉WNFEKF₁₈₄). In addition, two potential N-glycosylation sites (₁₁₂NGTE₁₁₅ and ₁₃₂NLTQ₁₃₅) were identified in HdhGPx. 3D modeling analysis showed that the overall structure of HdhGPx monomer had more similarity to human GPx3 than human GPx1. Relatively higher-level mRNA expression was detected in hepatopancreas, mantle and gonad by real-time PCR assays. The relative expression levels of HdhGPx mRNA in hepatopancreas and haemocytes were detected by real-time PCR in abalone fed with nine different diets containing graded levels of selenium (0.15, 1.32 and 48.7 mg kg^− 1), zinc (6.69, 33.85 and 710.63 mg kg^− 1) and iron (29.17, 65.7 and 1267.2 mg kg^− 1) for 20 weeks, respectively. The results showed that the expressions of HdhGPx mRNA were statistically higher at adequate dietary selenium (1.32 mg kg^− 1), zinc (33.85 mg kg^− 1) and iron (65.7 mg kg^− 1) than those in low dietary minerals, respectively. But HdhGPx mRNA expression levels were down-regulated by high contents of dietary selenium (48.7 mg kg^− 1), zinc (710.63 mg kg^− 1) and iron (1267.2 mg kg^− 1), respectively. These results indicated that adequate dietary minerals could increase the mRNA expression of HdhGPx, and then to increase the total antioxidant capacities in abalone.     

Mineral and trace element research in goats: A review

The long term studies with dairy goats on the effects of deficient semisynthetic feeding rations in one of 16 elements as reported in the annual proceedings of the Workshops on Minerals and Trace Elements and the International Trace Element Symposia by the University of Jena, Germany, since 1975 until today were reviewed. The development of the complex semisynthetic ration system was particularly important as it enabled to produce significant deficiencies of single elements in long term replicated studies and their interactions with other elements. The studies focused mainly on determining deficiency levels for each of the 16 elements, identifying deficiency symptoms and reasons for them, and establishing evidence for essentiality of the elements according to 7 criteria. Large amounts of analytical data were accumulated showing the changes in organ and tissue contents of the elements under study at normal and deficient levels, and their relation to impaired reproductive efficiency, growth, milk production, health, and mortality of goats and their kids. Histological sections of organs also showed their ultrastructural changes due to the elemental deficiencies. Most element deficiencies caused reproductive failures, reduced growth and milk production, but high mortality, while the control goats thrived on their semisynthetic but sufficient ration, attesting to its completely correct biological value. The identification of the reliable “indicator” organs and tissues for the diagnosis and detection of deficiency status of the specific elements in goats is of particular value to veterinary medicine and animal nutrition.