高龄化背景下农村高龄老年群体养护困境分析

伴随着人口老龄化的不断加剧,我国社会高龄化趋势日益明显.农村社会保障制度水平较低、农村高龄老人基本没有经济收入和农村高龄“空巢老人”迅速增加等问题的出现,使得农村高龄老人面临严峻的养护困境.通过初步研究,认为其原因主要集中于家庭保障功能的弱化、社会保障制度责任缺失和机构养老机构发展缓慢等方面.单方面依靠社会保险、救助等手段的效果是有限的,农村高龄老人养护问题已成为亟待社会共同努力解决的问题.     

Preferential flow and aging of NAPL in the unsaturated soil zone of a hazardous waste site: implications for contaminant transport

Flow of non‐aqueous phase liquids (NAPL) in the unsaturated zone is thought to be driven by gravity with a dominant vertical flow direction, and lateral spreading to be limited to the gradient of the relative permeabilities. The effect of soil profile build‐up, preferential flow, aging, and groundwater level fluctuations is mostly neglected. The objective of our study was to check the effects of such processes on the fate of NAPL in the unsaturated soil zone. At a hazardous waste site, we conducted a field survey of the unsaturated soil zone and monitored the groundwater for a two year period. We conducted spatially resolved and depth dependent soil sampling and analysis and the evaluation of former ram and core drilling protocols. The samples were analyzed for the 16 EPA PAH and alkanes with GC‐MS and GC‐FID. ¹³C‐NMR spectroscopy was used to assess structural changes of the NAPL phase. Flow of bulk NAPL along macropores and along preferential permeability structures, like sedimentation discontinuities, are the dominant transport pathways which cause large lateral spreading beyond those expected by the relative permeability gradient. Accumulation of NAPL was found at locations with abrupt textural changes and within the zone of capillary rise. Aging of NAPL results in the depletion in soluble and volatile compounds but also in oxidation and polymerization. It increases the chemical diversity and decreases the mobility of the NAPL. Thus, NAPL flow ceases much earlier than expected from the capillary forces. As chemical transformation is restricted to the NAPL water/air interface, a skin‐like thin film is formed which encapsulates and preserves the bulk NAPL from further hardening, limiting contaminant mass transfer from the NAPL to the aqueous phase.     

Soil organic matter beyond molecular structure Part II: Amorphous nature and physical aging

Glassy, rubbery, and crystalline phases are representatives of supramolecular structures which strongly differ in order, density, and other characteristics. In this contribution, the amorphous nature of soil organic matter (SOM) is reviewed with respect to the glassy/rubbery model, glass transition mechanisms, interactions of SOM with water, and physical aging. Glass‐transition behavior and physical aging are inherent properties of amorphous solids, and numerous spectroscopic investigations give insights into different domain mobilities of humic substances (HS). The correlation between sorption nonlinearity and glassiness of polymers and HS supports a relation between sorption and amorphicity in Aldrich humic acid. Further evidence is still required for the transfer to soil HS and SOM. Sorption and differential scanning calorimetry (DSC) data suggest a correlation between aromaticity and glassiness in HS, and the available data do currently not allow to decide unambiguously between specific sorption and hole filling as explanation. This needs to be verified in future research. Although parts of the investigations have up to now only been conducted with humic substances, the collectivity of available data give strong support for the glassy/rubbery conception of SOM. They clearly indicate that amorphous characteristics cannot be excluded in SOM. This is further supported by the observation of different types of glass‐transition behavior in samples of whole humous soil. In addition to classical glass transitions in water‐free soil samples, water surprisingly acts in an antagonistic way as short‐term plasticizer and long‐term antiplasticizer in a second, nonclassical transition type. Latter is closely connected with physico‐chemical interactions with water and suggests water bridges between structural elements of SOM (HBCL‐model). The gradual increase of T_g* in SOM indicates physico‐chemical aging processes, which are not restricted to polymers. They may be responsible for contaminant aging, changes in surface properties and increased soil compaction in agricultural soils.     

青榨槭种子老化特性的研究

研究青榨槭种子人工老化的特性,分析人工老化过程中不同老化条件对青榨槭种子活力的影响,同时探讨聚乙二醇处理对老化处理种子活力的影响。结果表明,随着温度的提高,青榨槭种子发芽率和发芽指数的变化呈现下降趋势,40℃时最高。PEG浓度为20%时,对老化处理的青榨槭种子修复效果最好,而激素对人工老化种子处理的效果不如用PEG引发处理的效果好。     

农业人口结构变动特征及其对乡村振兴的政策启示——基于安徽省农业普查数据的分析

利用2006—2016年农业普查数据分析了安徽省农业人口结构变动特征及其面临的突出困境。研究表明,从数量结构来看,安徽作为农业人口大省的属性没有根本性改变,农业人口分布显示出“北密南稀”;从性别结构来看,农村妇女非农化进程加快,越来越多的农村妇女脱离农业进入非农部门,农业女性化现象并不明显;从年龄结构来看,农业劳动力老龄化正在加深,农村人口老化与农业人口老化问题并存;从素质结构来看,农业劳动力受教育水平提升极为缓慢,整体处于小学和初中水平;从流动结构来看,农业发展对剩余劳动力的挤出效应以及城镇化、工业化的劳动力吸纳效应将持续发挥。鉴于此,在全面推进乡村振兴中,一要树立农业劳动力安全观,积极应对农业农村人口快速老龄化;二要加速启动农民职业化工程,培育新型职业农民;三要改变农业生产的组织经营方式,提高土地集中率、提高机械化水平;四要加大农业社会化和农村数字化建设,让更多主体参与农业农村现代化。     

宁夏贺兰山东麓老龄葡萄园土壤真菌群落结构分析

【目的】对宁夏贺兰山东麓老龄葡萄园土壤真菌群落物种组成及多样性进行研究,明析老龄葡萄园葡萄根际土壤真菌群落特征,为老龄葡萄园的科学管护和可持续发展提供依据。【方法】采集宁夏贺兰山东麓种植20年葡萄园不同土层（0～20,20～40和40～60 cm）的根际土壤（分别记为CS20、CS40和CS60）与非根际土壤（分别记为NCS20、NCS40和NCS60）,采用CTAB法提取土壤基因组DNA,对内转录区间（ITS1-ITS2）扩增后进行高通量测序,测定土壤真菌群落组成和物种多样性,分析土壤真菌群落结构的变化特征。【结果】群落分布丰富度指数（Chao1和ACE）分析表明,根际土壤中的真菌群落丰富度均高于非根际土壤,且二者存在显著差异（P＜0.05）;群落分布多样性指数（Shannon）分析表明,在0～20 cm土层根际与非根际土壤间多样性存在显著性差异（P＜0.05）,其余土层二者差异不显著。葡萄根际土壤与非根际土壤真菌分属17门、47纲、109目、211科、346属,门水平上优势真菌为子囊菌门（Ascomycota）、被孢霉菌门（Mortierellomycota）和担子菌门（Basidiomycota）,平均相对丰度分别为51.04%,5.68%和4.89%。在属分类水平上,根际土壤中新丛赤壳菌属（Neonectria）、Dactylonectria属、小球腔菌属(Leptosphaeria)、假裸球囊菌属(Pseudogymnoascus)真菌的平均相对丰度分别是非根际土壤的174.5,122.2,156.0和133.3倍,而非根际土壤中镰刀菌属（Fusarium）、青霉菌属（Penicillium）、Zopfiella属真菌是根际土壤的4.4,77.8和277.0倍。Weighted Unifrac距离指标分析表明,根际土壤各土层间（CS20、CS40和CS60）物种多样性差异较小,而非根际土壤各土层间（NCS20、NCS40和NCS60）物种多样性差异较大。【结论】宁夏贺兰山东麓老龄葡萄园葡萄根际土壤真菌群落分布丰富度较非根际土壤有所增加,真菌优势物种富集,根际土壤垂直土层间物种多样性差异减小,不利于维持根际土壤真菌群落的微生态平衡;病原菌Dactylonectria属和新丛赤壳菌属相对丰度增加,而镰刀菌属相对丰度降低,葡萄植株患病机率增大。     

部分玉米自交系根际线虫群体数量与玉米早衰病相关性研究

1999－2000年对10个玉米自交系早衰病与根际线虫群体变化的相关性进行了系统研究，结果表明：玉米自交系早衰病的发生和根际线虫的群体变化具有一定关系，玉米根际存在大量的线虫，其中重要的植物内寄生线虫－－短体线虫的种群数量与玉米早衰病的群体数量与玉米早衰病的发生呈正相关，其中543和嫩297两个感病自交系根际短体线虫出现的频率较高，而玉米根际的取食真菌和细菌的腐生线虫的群体数量与玉米早衰病的发生呈负相关。     

Effect of accelerated aging on maize, sorghum, and sorghum meal

Accelerated aging at 50 °C significantly affected the physical and chemical properties of sorghum and maize. Aging caused associations between starch granules, protein matrix, and cell walls. During aging, floury areas of the endosperm became more corneous; as the endosperm hardened, strong associations between starch and protein developed, causing the endosperm to fracture through endosperm cells instead of along cell walls, which is common for non-aged maize. Aging significantly decreased the pasting viscosity of starch, molecular solubility at 85 °C and the molecular weight of solubilized starch. Solubility of albumins and globulins decreased while solubility of proteins extracted by a reducing agent and/or in alkaline pH increased during aging. Decreased solubility and functionality of starch and protein in aged grain appear to be due to protein oxidation.     

宰后盆骨吊挂方式及成熟时间对黄牛牛肉品质的影响

为研究宰后盆骨吊挂技术对中国黄牛牛肉品质的影响,该试验选取12头品种、年龄和活体质量相近的鲁西黄牛杂交西门塔尔牛,屠宰后左半胴体采用跟腱吊挂,右半胴体采用盆骨吊挂。分别成熟1、4、7、14和21 d后测定pH值、汁液损失率、蒸煮损失率、肉色、剪切力、肌节长度等指标。研究发现,和传统跟腱吊挂相比,盆骨吊挂能够显著降低肉牛背最长肌宰后7 d之内的剪切力值,并使背最长肌宰后14 d的剪切力值50.71 N低于跟腱吊挂宰后21d的剪切力值58.48 N,此外,盆骨吊挂可以显著增加肌节长度,增值为0.44μm,使牛肉的汁液损失由5.44%降低到4.29%。因此,盆骨吊挂技术具有工业化推广的价值,可以达到快速提高牛肉嫩度,减少牛肉成熟时间的目的。     

种子老化机理的研究进展

介绍了国内外有关于种子老化的一些研究进展,主要对老化造成的种子生理、生化、遗传等方面的影响进行了概述。