不同灌溉方式下设施土壤硝态氮的积累特征及其环境影响

以不同灌溉方式下设施土壤及番茄为研究对象,采用田间试验与室内分析相结合的方法,对连年采用沟灌、滴灌和渗灌灌溉方式的设施土壤硝态氮、全盐含量、pH及番茄果实硝酸盐含量、水分生产效率进行了研究。结果表明:三种灌溉方式土壤硝态氮、全盐含量均呈现出明显的表聚现象,0~20 cm土层范围内,滴灌处理硝态氮含量和全盐含量明显低于沟灌和渗灌处理;不同灌溉方式土壤的pH值均随着土层加深而升高,在0~30 cm土层范围,土壤pH值滴灌高于沟灌,沟灌高于渗灌。沟灌和渗灌番茄果实硝酸盐含量显著高于滴灌,沟灌和渗灌番茄果实硝酸盐含量差异不显著;渗灌和滴灌水分生产效率明显高于沟灌。土壤硝态氮含量与土壤pH值呈极显著负相关,与全盐含量呈极显著正相关。总之,设施土壤硝态氮积累与土壤全盐含量、pH值、番茄果实硝酸盐含量关系密切;与沟灌和渗灌相比,滴灌更有利于抑制土壤退化。     

连续流Biohydrogenbacterium R3sp. nov.菌株糖蜜废水发酵产氢能力分析

以从连续流搅拌槽式反应器(CSTR)内的活性污泥中分离出的高效厌氧产氢菌Biohydrogenbacterium R3 sp.nov.为发酵产氢微生物,糖蜜废水为发酵底物,试验分析了连续流发酵法R3菌株的产氢效能.结果表明:在温度36℃、水力停留时间6h、进水COD在2 600～4 440 mg/L范围内变化,CSTR...     

玉米秸秆发酵产氢条件优化及其产氢特性研究

在批式培养试验中,以牛粪堆肥为天然产氢菌源,以酸解玉米秸秆为底物,通过厌氧发酵生产氢气。利用二因素三水平设计正交实验,考察了初始pH值和初始底物浓度对酸解玉米秸秆发酵产氢的影响,并系统研究了其发酵产氢特性。在初始pH 6.0、底物浓度10g/L的产氢条件下,酸解秸秆的最大产氢量和最大产氢速率分别为265.5mL/(g·TS)和7.9mL/h。通过扫描电子显微镜(SEM)对秸秆形貌进行分析,发现稀酸水解作用可以破坏秸秆的微结构,在发酵产氢过程中混合微生物可直接降解纤维素产氢。     

Distribution of hydrogen in the near surface of Mars: evidence for subsurface ice deposits

Using the Gamma-Ray Spectrometer on the Mars Odyssey, we have identified two regions near the poles that are enriched in hydrogen. The data indicate the presence of a subsurface layer enriched in hydrogen overlain by a hydrogen-poor layer. The thickness of the upper layer decreases with decreasing distance to the pole, ranging from a column density of about 150 grams per square centimeter at -42 degrees latitude to about 40 grams per square centimeter at -77 degrees. The hydrogen-rich regions correlate with regions of predicted ice stability. We suggest that the host of the hydrogen in the subsurface layer is ice, which constitutes 35 +/- 15% of the layer by weight.     

Spatial variability of soil properties in red soil and its implications for site-specific fertilizer management

Assessing spatial variability and mapping of soil properties constitute important prerequisites for soil and crop management in agricultural areas. To explore the relationship between soil spatial variability and land management, 256 samples were randomly collected at two depths(surface layer 0–20 cm and subsurface layer 20–40 cm) under different land use types and soil parent materials in Yujiang County, Jiangxi Province, a red soil region of China. The pH, soil organic matter(SOM), total nitrogen(TN), cation exchange capacity(CEC), and base saturation(BS) of the soil samples were examined and mapped. The results indicated that soils in Yujiang were acidified, with an average pH of 4.87(4.03–6.46) in the surface layer and 4.99(4.03–6.24) in the subsurface layer. SOM and TN were significantly higher in the surface layer(27.6 and 1.50 g kg~(–1), respectively) than in the subsurface layer(12.1 and 0.70 g kg~(–1), respectively), while both CEC and BS were low(9.0 and 8.0 cmol kg~(–1), 29 and 38% for surface and subsurface layers, respectively). Paddy soil had higher pH(mean 4.99) than upland and forest soils, while soil derived from river alluvial deposits(RAD) had higher pH(mean 5.05) than the other three parent materials in both layers. Geostatistical analysis revealed that the best fit models were exponential for pH and TN, and spherical for BS in both layers, while spherical and Gaussian were the best fitted for SOM and CEC in the surface and subsurface layers. Spatial dependency varied from weak to strong for the different soil properties in both soil layers. The maps produced by selecting the best predictive variables showed that SOM, TN, and CEC had moderate levels in most parts of the study area. This study highlights the importance of site-specific agricultural management and suggests guidelines for appropriate land management decisions.     

pH对肌原纤维蛋白及其热诱导凝胶非共价键作用力与结构的影响

【目的】研究pH对鸡肉肌原纤维蛋白热诱导凝胶非共价键作用力和结构的影响,揭示凝胶非共价键作用力与结构之间的关系。【方法】活AA鸡宰杀,提取鸡胸肉肌原纤维蛋白,配制不同pH(5.0、5.5、6.0、6.5、7.0)的肌原纤维蛋白溶液并制成热诱导凝胶,运用Zeta电位仪测定肌原纤维蛋白凝胶分子表面的电位值来表征静电相互作用;利用拉曼光谱仪测定肌原纤维蛋白凝胶I760/I1003反映疏水相互作用变化,I850/I830反映凝胶氢键变化,并通过分析酰胺带I最大峰的波数计算蛋白和凝胶的二级结构含量;用粒度仪测定肌原纤维蛋白粒径大小和分布情况;用扫描电镜观察凝胶微观结构。【结果】pH由7.0降至5.0,肌原纤维蛋白热诱导凝胶的Zeta电位值从-17.87显著变化到-0.263(P0.05),表明肌原纤维蛋白凝胶分子表面所带负电荷急剧减少,静电斥力显著减弱;归一化强度I760/I1003比值由0.86逐渐增大到0.927,表明肌原纤维蛋白中色氨酸包埋程度增加,凝胶分子间的疏水相互作用增强;归一化强度I850/I830比值从1.039减小至0.987,表明肌原纤维蛋白酪氨酸残基苯环上-OH与水分子生成的氢键逐渐减少、与蛋白质上其他基团生成的氢键逐渐增加,即蛋白分子间的氢键作用增强,蛋白与水的作用减弱。pH由7.0降至6.5,肌原纤维蛋白热诱导凝胶的α-螺旋含量从59.96%降低到55.24%(P0.05),β-折叠含量从15.83%显著增加到19.44%(P0.05),β-转角和无规则卷曲含量都显著增加(P0.05);pH在6.5—6.0时,各种结构含量变化都不显著(P0.05);pH在6.0—5.0时,肌原纤维蛋白热诱导凝胶的α-螺旋含量从51.61%降低到16.76%(P0.05),β-折叠含量从22.23%显著增加到48.93%(P0.05),β-转角和无规则卷曲含量都显著增加(P0.05)。随着pH降低,肌原纤维蛋白α-螺旋的含量逐渐降低,而β-折叠、β-转角和无规则卷曲含量都显著增加(P0.05)。pH在7.0—5.0时,肌原纤维蛋白粒径大小逐渐增大,D_(10)从13.4μm上升到48.4μm,D_(50)从38μm上升到253μm,D_(90)从236μm上升到805μm。pH 7.0时形成的凝胶微观结构有序,孔径最大;随着pH减小,凝胶微观结构有序程度降低,孔径变小;pH 5.0时形成的凝胶微观结构无序、孔径最小。pH与凝胶静电相互作用、疏水相互作用极显著负相关(P0.01),与氢键、α-螺旋含量显著正相关(P0.05),与β-折叠含量显著负相关(P0.05),这表明pH显著影响静电斥力、疏水相互作用、分子间氢键和二级结构含量。静电相互作用、疏水相互作用、氢键与蛋白凝胶二级结构都显著相关(P0.05),表明非共价键作用力显著影响二级结构。【结论】肌原纤维蛋白凝胶非共价键作用力、二级结构和微观结构与pH密切相关;pH从7.0降到5.0,静电斥力减小、疏水相互作用增大、分子间氢键增大,是α-螺旋含量减小、β-折叠含量增多以及凝胶微观结构变得无序、孔径减小的原因。     

Long-term ecosystem stress: the effects of years of experimental acidification on a small lake

Experimental acidification of a small lake from an original pH value of 6.8 to 5.0 over an 8-year period caused a number of dramatic changes in the lake's food web. Changes in phytoplankton species, cessation of fish reproduction, disappearance of the benthic crustaceans, and appearance of filamentous algae in the littoral zone were consistent with deductions from synoptic surveys of lakes in regions of high acid deposition. Contrary to what had been expected from synoptic surveys, acidification of Lake 223 did not cause decreases in primary production, rates of decomposition, or nutrient concentrations. Key organisms in the food web leading to lake trout, including Mysis relicta and Pimephales promelas, were eliminated from the lake at pH values as high as 5.8, an indication that irreversible stresses on aquatic ecosystems occur earlier in the acidification process than was heretofore believed. These changes are caused by hydrogen ion alone, and not by the secondary effect of aluminum toxicity. Since no species of fish reproduced at pH values below 5.4, the lake would become fishless within about a decade on the basis of the natural mortalities of the most long-lived species.     

Autoionization in liquid water

The dissociation of a water molecule in liquid water is the fundamental event in acid-base chemistry, determining the pH of water. Because of the short time scales and microscopic length scales involved, the dynamics of this autoionization have not been directly probed by experiment. Here, the autoionization mechanism is revealed by sampling and analyzing ab initio molecular dynamics trajectories. We identify the rare fluctuations in solvation energies that destabilize an oxygen-hydrogen bond. Through the transfer of protons along a hydrogen bond "wire," the nascent ions separate by three or more neighbors. If the hydrogen bond wire connecting the two ions is subsequently broken, a metastable charge-separated state is visited. The ions may then diffuse to large separations. If, however, the hydrogen bond wire remains unbroken, the ions recombine rapidly. Because of their concomitant large electric fields, the transient ionic species produced in this case may provide an experimentally detectable signal of the dynamics we report.     

秸秆发酵产氢菌系的筛选及菌系功能强化研究

采用连续稀释法从牛粪堆肥中筛选到一个可以较好的降解秸秆产氢的菌系CYY,该菌系的最适生长温度为37℃,最适pH为8.5,在秸秆培养基中,氢气产量为90 mL·L-1 culture。采用改良的Hungate厌氧滚管法,从菌系CYY中筛选到一株降解秸秆产氢效果较好的纯菌CYY-9,此菌为杆菌,最适生长温度为37℃,最适pH为8.5,利用秸秆产氢量为86 mL·L-1culture。将菌株CYY-9以一定比例添加到菌系CYY中,研究发现:当菌系培养到40 h左右时,以4%的比例接种菌株CYY-9,菌系的产氢能力最强,产氢量达到103 mL·L-1 culture,与原有菌系相比,产氢量增长了12.9%,秸秆降解率增长了49.2%,达到了对菌系生物强化的目的。     

影响产氢发酵细菌B49产氢的部分因子研究

采用间歇培养实验,研究了部分因子碳源葡萄糖、氮源、菌龄、温度及pH值对产氢发酵细菌新菌种B49(Hydrogen-producingBacterialB49,AF481148inEMBL,简写HPBB49)生物产氢的影响。试验结果表明,以葡萄糖为碳源,其浓度10g.L-1时,HPBB49的葡萄糖利用率为100%,氢气产率为1.69molH2.mol-1葡萄糖;HPBB49不能利用无机氮源,有机氮是HPBB49生长、产氢的适宜氮源;菌龄影响HPBB49的产氢;B49产氢量随细菌生长OD值的增加而增加;HPBB49生长和产氢适宜温度均为35℃;B49最适生长的pH值约为4.5,最适产氢的pH值约为4.0。     

Volatile-rich lunar soil: evidence of possible cometary impact

A subsurface Apollo 16 soil, 61221, is much richer in volatile compounds than soils from any other locations or sites as shown by thermal analysis-gas release measurements. A weight loss of 0.03 percent during the interval 175 degrees to 350 degrees C was associated with the release of water, carbon dioxide, methane, hydrogen cyanide, hydrogen, and minor amounts of hydrocarbons and other species. These volatile components may have been brought to this site by a comet, which may have formed North Ray crater.     

pH对羔羊背最长肌肌原纤维蛋白热诱导凝胶的影响

【目的】研究pH对无角陶赛特×小尾寒羊F1代羔羊背最长肌肌原纤维蛋白热诱导凝胶硬度、保水性及微观结构的影响,分析凝胶形成过程中作用力的变化,初步揭示pH对羔羊肉热诱导凝胶形成的影响机制。【方法】以不同pH下肌原纤维蛋白热诱导凝胶的硬度、保水性为指标,确定典型pH（5.0、6.0、7.5）,并分析该典型pH下肌原纤维蛋白热诱导过程中的化学作用力、热稳定性变化,以及凝胶微细结构的差异。【结果】3个典型pH下羔羊背最长肌肌原纤维蛋白热诱导凝胶表现出不同的凝胶特性：pH 5.0时,凝胶的保水性最差、微观结构杂乱无序;pH 6.0时,凝胶硬度最低;pH 7.5时,凝胶的保水性、硬度最大且具有致密有序的微观结构。形成凝胶的主要作用力为疏水相互作用,但pH对离子键、氢键具有较大影响,不同pH下凝胶的形成机制存在差异。【结论】pH可通过影响体系的化学作用力,改变蛋白质之间以及蛋白质与水之间的相互作用,形成具有不同保水性、质构特性和微观结构特性的凝胶。     

NH4^＋浓度对有机废水厌氧发酵产氢的影响

[目的]利用人工有机蔗糖废水通过厌氧发酵产氢气,考察水体中NH4＋浓度（0～8 000 mg/L）对厌氧发酵产氢的影响。[方法]分析废水中糖降解速率,比产氢率和产氢率。[结果]结果表明当NH4＋浓度在1 200～2 400 mg/L时,对微生物的厌氧发酵产氢是有利的,但当NH4＋浓度大于4 800 mg/L时,对厌氧发酵产氢有明显的抑制作用,其中对其发酵液相产物也有明显的影响。     

不同耕作方式对紫色土侵蚀及磷素流失的影响

【目的】研究川中丘陵区紫色土零散坡耕地在玉米成熟期由降雨引发的水土流失及磷素流失特征,为该区坡耕地养分流失预测评价、防治以及协调区域土地管理,改善生态环境提供理论依据。【方法】采用人工模拟降雨和微小区试验相结合的方法,在玉米成熟期,对平作、顺坡垄作及横坡垄作3种耕作方式的地块进行人工降雨,降雨强度为1.7 mm•min-1,历时40 min。研究人工降雨对地表侵蚀、壤中流量及其磷素流失的影响。【结果】顺坡垄作地表侵蚀量及磷素流失量均最大,其壤中流及磷素流失最小;横坡垄作地表侵蚀量及磷素流失量最小,而壤中流损失较大。不同耕作方式下壤中流总量虽然较地表径流少,但是其磷素含量却很高,总磷浓度均达到了0.2 mg•L-1,约为地表径流的1.3倍。【结论】紫色土零散坡耕地不易采用顺坡垄作,横坡垄作能很好的控制土壤侵蚀,但在日常耕作管理中需注意对垄的修复保护。在整个侵蚀过程中3种耕作方式的径流损失及磷素流失均以地表损失为主,径流中磷素以可溶性磷流失为主。     

链霉菌S024所产生的抗菌活性物质的研究

[目的]为更好满足放线菌对农业生产发展的要求。[方法]从土壤中分离到一批放线菌,从中筛选出1株高活性菌株S024,对其产生的抗生素进行初步研究。[结果]该菌株产生的抗生素抑菌谱广,尤其对小麦纹枯病,小麦根腐病等真菌病害有很好的防治效果。对酸碱稳定,在pH值3.0~9.0中间稳定。温度耐受性较强,在适宜pH条件下,100℃处理0.5 h,其活性基本不变。[结论]对抗生素性质初步分析表明该抗生素为一种水溶性、强极性抗生素,根据性质推断此抗生素属于氨基糖苷类的抗生素。     

Charge transfer equilibria between diamond and an aqueous oxygen electrochemical redox couple

Undoped, high-quality diamond is, under almost all circumstances, one of the best insulators known. However, diamond covered with chemically bound hydrogen shows a pronounced conductivity when exposed to air. This conductivity arises from positive-charge carriers (holes) and is confined to a narrow near-surface region. Although several explanations have been proposed, none has received wide acceptance, and the mechanism remains controversial. Here, we report the interactions of hydrogen-terminated, macroscopic diamonds and diamond powders with aqueous solutions of controlled pH and oxygen concentration. We show that electrons transfer between the diamond and an electrochemical reduction/oxidation couple involving oxygen. This charge transfer is responsible for the surface conductivity and also influences contact angles and zeta potentials. The effect is not confined to diamond and may play a previously unrecognized role in other disparate systems.     

生防木霉菌Tr11菌株适宜生长条件研究

对木霉菌菌株Tr11室内菌丝生长、产孢的适宜条件进行了研究,结果表明:Tr11菌株在PDA培养基上生长最好,产孢最多;25℃下菌丝生长最快,15~30℃下均可大量产孢;黑暗可促进菌丝生长,但有无光照对孢子产生影响不明显;果糖是菌丝生长最好的碳源,乳糖是Tr11菌株产孢的最佳碳源;蛋白胨、硫酸铵是有利于菌丝生长和产孢的有机氮源;微量元素中Ca、Cu对菌丝生长及产孢都有一定的促进作用;pH值5最适宜菌丝生长,pH值6~8适宜产孢。     

Buying in: the influence of interactions at farmers’ markets

Many consumers are motivated to attend Farmers’ Markets (FMs) because of the opportunity to purchase fresh and local products. The subsequent interactions at FMs provide an important pathway for the direct exchange of information. While previous research suggests that people value local food and the FM shopping experience and that purchasing directly from producers can lead to transformative learning, little is known about exactly how the shopping experience at FMs can influence consumer purchasing behavior. This study examines the extent of and mechanism for such “influencing.” Using data from surveys, observations, and interviews gathered at six FMs, we analyze the interactions between consumers and vendors, including the motivations and values of both parties. We explore the question, “How do farmers’ markets facilitate change in consumer purchasing behavior?” We propose that the dynamic of change in consumer purchasing behavior at FMs takes root in the exchange of information between consumers and vendors during interactions. Our results suggest that there are three specific characteristics shared by FM consumers and vendors that lead to these meaningful interactions at FMs: symmetry of motivations to attend FMs, shared values, and mutual dependence on interactions. Then, when a consumer learns new information from a FM vendor during an interaction, the consumer is more likely to make a change in their immediate purchase. Information about the products for sale and the modes of production of those items can especially impact consumers’ immediate purchases at FMs. We found that FM interactions can also impact long-term purchasing behavior, such as purchasing more organic or locally produced foods. Our results suggest that FM interactions may have significant implications for consumer health, local economies, and the environment.     

地下滴灌及其在烤烟灌溉中的应用分析

地下滴灌是具有巨大潜力的节水工程技术,是将毛管埋于地下,通过出水口将水或水肥的混合液送到作物根区土壤中,再借助毛细管作用或重力作用将水分扩散到根系层供作物吸收利用,目前已在多种植物中得到应用,取得了较好的效果,但其在烤烟上的应用较少.为此,综述了国内外地下滴灌的发展现状和应用特点,分析了地下滴灌技术在烤烟生产应用的必要性和可行性,并对其应用提出几点建议.     

猪粪厌氧发酵联产氢气和甲烷的能源转换效率研究

[目的]探讨猪粪厌氧发酵先产氢气后产甲烷的能源转换效率,以期提高传统厌氧发酵的能源转换效率。[方法]将发酵料液的p H调节至4.5~5.5,首先进行厌氧发酵产氢气,产氢结束后将产氢发酵液的p H调节至6.5~7.5进行厌氧发酵产甲烷。[结果]猪粪厌氧发酵联产氢气和甲烷的产能效率为44.06%,明显高于猪粪单独厌氧发酵产氢的产能效率(14.43%)以及猪粪单独厌氧发酵产甲烷的产能效率(32.80%)。[结论]厌氧发酵联产氢气和甲烷能有效提升传统厌氧发酵产能效率。