微尺度重金属土壤化学研究进展与展望

土壤重金属污染是我国面临的重要生态环境问题,有效管控与修复重金属污染土壤有必要弄清重金属与土壤固相组分的作用机制。土壤组成多样、结构复杂、空间异质,加之土壤团聚体粒径大小不一,形成微观结构和表面性质各异的土壤微域,控制着重金属的形态转化及生物有效性。因此,深入认识微尺度的重金属土壤化学对于预测和管控土壤重金属环境化学行为至关重要。同步辐射X射线微探针(Microprobe)、X射线扫描透射显微术(STXM)及纳米二次离子质谱技术(Nano SIMS)等技术具有微纳米级空间分辨率,为在环境意义尺度上探究微尺度重金属土壤化学提供了独特的支撑平台。本文从环境土壤化学发展历程及当前发展瓶颈、现代微尺度分析技术及其在微尺度重金属土壤化学中的应用进展等方面综述,并对该领域未来的发展进行了展望。     

Reconstruction of Pinus Sylvestris knots using measurable log features in the Swedish Pine Stem Bank

Abstract

The objective of this study was to develop a method for reconstruction of parametrically described whorls and knots from data possible to extract from industrial scanning of logs, using X-ray scanners. The method was conceived using the logs in the Swedish Pine Stem Bank as a foundation, and was based on a few predictor features extracted from these logs; namely whorl volume, distance between whorls and distance between pith and surface. These features were not measured in images but calculated from existing parameterised knots. Simulated test sawing shows that the reconstruction method results in a representative model of the knot structure in the log, when considering the grade distribution of the sawn timber produced by the simulation program. The results of this study could, for instance, be used for improved online quality predictions at sawmills. One step in this direction is to use industrial X-ray data to enlarge the amount of log data available for sawing simulation research. Future work can, therefore, focus on developing a practical application of the results presented here.     

湖南省邓恩桉与柳桉高产纤维材引种培育研究进展

中国大多数桉树资源主要集中在较为温暖的沿海地区.目前在湖南和江西等华南和中南省份较为冷凉的内陆地区,通过选择一些合适的耐寒桉树品种,种植了一些规模不大的桉树人工示范林,这些示范林显示出了较好的适应性与丰产性.这些较为冷凉的内陆地区有着立地条件较为优越的适合人工林发展的广大林地.对于较冷地区,尤其是湖南省来说,通过分析所...     

甘蔗新品种“海大28号”的选育及其繁殖推广

甘蔗新品种“海大28号”是广东海洋大学农业生物技术研究所甘蔗研究室从母本为Co419、父本为Cp49／50的杂交种子播种育苗，按甘蔗育种程序逐级试验筛选获得的优良单系90／158，经采用^60Coγ射线对90／158单系梢部苗的单芽和茎梢幼嫩组织诱导的愈伤组织进行辐射处理改良而育成甘蔗新品种。多年试验结果表明，该品种具有高产、高纤维分、高糖、耐旱、抗虫、抗寒的糖能兼用的甘蔗新品种，适合广东、广西、云南、海南等蔗区地力中等或中等以上的旱坡地及水旱田推广种植。     

Physical aspects of the biopolymer matrix in wheat bran and its dissected layers

The objectives of this work were to 1) determine the physical structure of untreated wheat bran and the differences in physical structure between its dissected layers; 2) evaluate how bran hydration affected bran crystallinity and polymer order; and 3) determine how enzymatic treatment of wheat bran affected its physical structure. For the first time, X-ray diffraction (XRD), small angle X-ray scattering (SAXS), solid-state ¹³C cross-polarization magic-angle spinning nuclear magnetic resonance (¹³C CP/MAS NMR), and polarized light microscopy with a waveplate were used to study the physical structure of wheat bran and its dissected layers. The XRD and solid-state ¹³C CP/MAS NMR both confirmed the presence of crystalline cellulose in untreated bran, enzymatically treated bran, and dissected bran layers. The outer pericarp had the highest crystallinity of the dissected bran layers and showed negative birefringence. The aleurone layer was low in cellulose content and completely amorphous, yet the cell walls in the aleurone layer showed strong positive birefringence. The treatment of destarched and deproteinated bran with the Updegraff reagent removed amorphous material, leaving its crystalline cellulose structure intact. Hydration of the outer pericarp increased its crystallinity index and CP/MAS NMR resonance intensity, which indicated a possible increase in polymer order. The SAXS also confirmed that cell wall polymers, possibly aggregated cellulose microfibrils, increased in order as a result of hydration.     

Study of the microstructure of durum wheat endosperm using X-ray micro-computed tomography

Durum wheat grains are used for producing food, such as pasta or couscous. The grain mechanical properties which are linked to its internal micro-structure (i.e. endosperm porosity) are known to determine its ability to produce semolina during milling. The proportion of grains having porous endosperm in a batch appears therefore as a critical quality factor for the durum wheat value chain. Our objective was to investigate the ability of X-ray micro-tomography (μCT) method to describe the porous or vitreous counterpart structures in the endosperm of durum wheat grains. We selected two different durum wheat samples displaying vitreous or partially porous endosperms. The grains were analyzed using μCT at two pixel sizes (1 μm or 7 μm). The μCT data collected at 7 μm pixel size were used for qualitative classification of grains according to apparent distribution curve of the porosity parameters. Analysis of μCT images at 1 μm pixel size allowed us to propose pore size classification in the vitreous and porous parts of the endosperm in three durum wheat grain. Results are used to better describe the durum-wheat endosperm microstructure, but requires long scanning periods.     

Modification of physicochemical properties and in vitro digestibility of wheat flour through superheated steam processing

Native and moistened wheat flours (moisture contents were 13.5 and 27.0%, respectively) were treated with superheated steam (SS) at different temperatures (140 and 170 °C) and times (1, 2 and 4 min). Their physicochemical and digestive properties were analyzed. For native flour, SS treatment altered the starch molecular structure and behavior slightly. While for moistened flour, crystalline degree, gelatinization enthalpy, amylose leaching (AML) and falling number significantly decreased, but thermal transition temperatures increased with the rise of treating severity. Clumping of starch granules, aggregation of proteins and formation of amylose-lipid complexes occurred in both native and moistened flours. Broader pasting temperature ranges and higher viscosities were found on SS-modified flours. Additionally, SS treatment on moistened flours increased resistant and slowly digestible starch contents. In general, SS treatment induced changes in starch molecular structure and reactions among flour components leading to more stable structures, thus affecting their pasting behavior, thermal properties and in vitro digestion.     

Mutual influence of copper and paraquat on their adsorption in soil

Paraquat and copper (Cu) are commonly used and detected in soil.Therefore,it is important to understand their mobility in the environment.In this study,the competitive effects of paraquat and Cu on their adsorption in five representative Chinese soils were investigated using batch adsorption equilibrium experiments and spectroscopic analysis.The results showed that the adsorption of paraquat in soil varied with soil type and was positively correlated with both soil cation exchange capacity and o...     

Effect of support medium,hydraulic loading rate and plant density on water quality and growth of halophytes in marine aquaponic systems

The development of marine intensive land‐based aquaculture systems has been limited due to the absence of methods to manage saline wastewater. Aquaponic systems, although commonly applied to freshwater aquaculture, can potentially manage nutrient wastes while providing a secondary product. The aim of this study was to evaluate both the capacity for water treatment and the production requirements of two saltwater‐tolerant plant species (Sesuvium portulacastrum and Batis maritima) when grown hydroponically in a marine aquaponic system. The presence of plants was found to significantly contribute to nitrate removal, such that mean nitrate concentrations were 10.1 ± 5.4 and 12.1 ± 6.1 mg/L NO₃^?‐N in planted and unplanted treatments respectively. The use of coconut fibre as a planting medium also significantly contributed to nitrate removal, such that mean nitrate concentrations were 9.78 ± 5.4 and 12.4 ± 6.0 mg/L NO₃^?‐N in coconut fibre and expanded clay treatments respectively. Daily nitrogen removal was greatest in the coconut fibre/plants treatment, ranging from ?18% to 67%. Hydraulic loading rate, plant species and plant density did not significantly affect water quality or plant growth. The low flow/saltwort/low density treatment had the greatest mean daily nitrogen removal, ranging from 25% to 172%. The results indicate that the main nitrogen removal mechanisms were simultaneous nitrification–denitrification in the hydroponic plant beds and nitrogen removal through plant growth. This study demonstrates that marine aquaponics could be an effective way to manage nutrient removal in marine land‐based aquaculture systems.     

江蓠提胶废渣制备不溶性膳食纤维工艺研究

以江蓠提胶废渣为原料,进行酶法制备不溶性膳食纤维(IDF)优化工艺研究试验。分别通过体系的酶量、酶解温度和酶解时间的单因素试验及这3个因素的正交试验,研究其对不溶性膳食纤维含量的影响,获得其最佳的制备工艺为:料液质量比1∶8,复合蛋白酶0.4%(质量分数),pH值9,40℃水解3 h,洗涤至中性后,60℃恒温干燥。该工艺制备的产品得率48.8%,不溶性膳食纤维含量(干基)高达93.61%(质量分数),粗蛋白质0.70%,粗脂肪0.87%,持水力与膨胀力分别为5.05 g/g和6.47 mL/g,高于西方国家小麦麸皮膳食纤维标准。可望使江蓠提胶废渣变废为宝,开发成为膳食纤维功能食品。