137Cs示踪技术在滦河源区栗钙土风蚀速率估算中的应用

对采集于滦河源区3个栗钙土剖面中的27个土层样品的pH、有机碳含量、碳酸钙含量、密度及质地进行了化验分析,运用ADCOM100超低本底γ谱仪测定了土壤样品1377Cs的比活度.结果表明,自然栗钙土以及被风蚀土壤剖面中137Cs比活度随深度呈指数递减式分布,其最大渗透深度可达约30cm;利用137Cs示踪技术估算的研究区土壤风蚀速率在0.1842cm·a-1和0.2897cm·a-1之间;栗钙土不同粒径土壤颗粒中137Cs的比活度差异显著,即细粒(粒径≤0.10mm的极细砂、粉粒和黏粒)中137Cs比活度大于细砂(0.10～0.25mm)中137Cs比活度大于粗粒(0.25～2.00mm的中砂、粗砂和极粗砂)中137Cs比活度.可见,运用137Cs示踪法可以定量估算区域土壤风蚀速率,但需综合考虑137s在土壤中的分布、土壤有机质含量和质地等因素,以使其结果将更为准确.     

Strontium isotope constraints on the seasonal variation of the provenance of base cations in rain water at Kawakami, Central Japan

The ⁸⁷Sr/⁸⁶Sr ratios in monthly precipitation in the forested basin at Kawakami, central Japan, varied seasonally from 0.709 to 0.711 in spring to as low as 0.7062 ± 0.0004 in autumn over nine years from 1987 to 1995. The seasonal variation can be explained in terms of the mixing of three sources of Sr: sea salt (⁸⁷Sr/⁸⁶Sr 0.70917), soluble eolian minerals originating from deserts in continental Asia ( 0.711), and biogenic materials growing on soils derived from the volcanic rock substrates in the vicinity ( 0.706). It is estimated that the contribution of sea-salt Sr into the Kawakami rain Sr is relatively constant (10 ± 5%) and that more than half of the Sr is of biogenic origin throughout the year except during spring rains when 50% of the Sr is due to the dissolution of Ca-minerals from Asian dusts. The dominant contribution of eolian components to spring rains is consistent with the high concentration of ³H, which is typical of air masses from Asia.     

环境光强对糯玉米籽粒主要品质成分的影响

作物生长发育期间的环境光强是影响作物品质的主要因素之一。为了解不同环境光强对鲜食型糯玉米籽粒品质的影响,以香白糯(Xiangbainuo)为材料,采用人工遮光的方法模拟不同的环境光强,在糯玉米籽粒灌浆期间测定其籽粒粗蛋白、淀粉、脂肪、水分含量的变化规律和收获时籽粒的氨基酸总量及氨基酸各组分含量。结果表明,遮光没有明显改变糯玉米灌浆期间籽粒中主要品质成分的变化趋势,但对主要品质成分所占质量分数的影响很大。弱光(40%全光照)与自然光照(100%全光照)相比,糯玉米授粉后30d时,其籽粒中粗蛋白和淀粉的质量分数分别增加1.56和3.5个百分点,脂肪减少了1.5个百分点;自然光照条件下糯玉米籽粒的含水量每天以1.31%的速率减少,其脱水速率高于弱光下糯玉米籽粒脱水速率0.17个百分点。收获时,40%全光照条件下糯玉米籽粒中粗蛋白质量分数、氨基酸总量和赖氨酸质量分数高于自然光照和80%全光照时的质量分数,而糯玉米籽粒的百粒干质量显著降低。     

Steady Shallow-Water Current and Solute Transport around a Semi-Conical Headland

Laboratory experiments have been carried out to investigate the effects of a sloping wall headland on the flow characteristics and the associated concentration distributions from a point source around the headland. A semi-conical headland with a slope of 1:2 was set up in a flow basin, 4.8 m long and 3.8 m wide. In this paper, the experimental results of a steady shallow-water current are reported. Three dimensional flow velocities in the basin were measured using Sontek-ADV instrument. The dye concentration levels in the basin were measured by two fluorometers. The experimental results showed a large-scale re-circulation region behind the semi-conical headland. The peak turbulence energy, at about 53% of the local kinetic flow energy, coincides with the region of high velocity gradient. Significant vertical flows were observed around the area near the downhill slope of the headland, with a maximum ratio of vertical to horizontal velocities being about 22%. Such relatively significant vertical scouring velocities, coupled with strong turbulence energy and high horizontal velocity gradients in the same region, could cause severe bed erosion. The experimental results have also been compared with the predicted results of a depth-averaged numerical model. The predicted eddy structure and the concentration distribution in the re-circulation area were found to compare favourably with the experimental results. However, the discrepancies in the flow velocities and the concentration levels near the headland were apparent. It was observed that the dye concentration continued to spread in the cross-stream direction after passing the headland, whereas only a limited extent of the lateral spreading was predicted by the numerical model further downstream of the headland.     

离体培养植物细胞的表面与细胞粘连

对离体培养的胡萝卜（Ｄａｕｃｕｓｃａｒｏｔａ）细胞和普通烟草（Ｎｉｃｏｔｉａｎａｔａｂａｃｕｍ）细胞的表面进行了扫描电镜观察．观察表明，细胞的自由表面上有很多疣突和纤丝．疣突的大小不同、形状各异，主要含果胶质；有些细胞表面出现小坑，坑中集中有许多微小颗粒．疣突相互可融合成更大的疣突或连成桥；纤丝常与疣突结合．纤丝－纤丝的交织，纤丝－疣突的交联，及疣突－疣突的融合，在细胞壁外表面构成交织的网络．同种细胞之间及异种细胞之间均可通过纤丝、疣突的交织融合而粘连．疣突分布不均一，且与细胞的分散性有关．与疏松烟草愈伤组织比较，致密烟草愈伤组织细胞的自由表面上疣突显著较多．在分化再生时，烟草愈伤组织首先致密变绿，然后才见到芽的分化及植株再生．对疣突出现、壁物质沉积与细胞粘连、细胞分化、形态建成几者之间的关系进行了讨论．     

同位素示踪法研究有机污染物在模拟水生生态系统中的行为

应用同位素示踪技术，研究了模拟水生生态系统中三氯苯、邻苯二甲酸正丁酯，２，４，６－三氯酚－＾１４Ｃ的分布、迁移、转化行为。实验周期后，水中污染物浓度分别降低了８９％，８０％，９５％以上，三氯苯在底泥和浮游生物中有积累。测定了标记物在水、悬浮物、＾１４ＣＯ２吸收溶液，ＸＡＤ－２树脂上的放射性强度。假设水中标记物的降解遵循一级速率过程，２４ｄ后，水中２，４，６－三氯酚－＾１４Ｃ浓度已降为原来浓度的５％     

垃圾渗液中有机污染物初探

采用ＧＣ－ＭＳ法对垃圾渗液中的有机物组成进行了分析。结果表明，垃圾渗液中含有多环芳烃，直链烷烃、邻苯二甲酸酯类等有机污染物和致癌物。     

石家庄市冬季一次重污染过程分析与反馈效应研究

为深入探究高ρ（PM_2.5）地区重污染过程的发展变化规律,以石家庄市一次重污染过程（2017年1月13-20日）为例,结合空气质量监测数据、PM_2.5组分测试数据、气象观测资料,从重污染发展阶段（简称"P1阶段"）、维持阶段（简称"P2阶段"）和清除阶段（简称"P3阶段"）分析PM_2.5及其化学组分的变化特征、气象条件和高低空天气形势演变特征,并利用WRF-Chem模型定量研究重污染过程气溶胶反馈效应对典型气象要素的影响.结果表明:①此次重污染过程属于逐步累积增长、快速清除型,在P2阶段ρ（PM_2.5）平均值为241.0 μg/m3,最大值为367.5 μg/m3.②P1和P2阶段高低空大气环流配置稳定,大气边界层高度范围为620.6~712.2 m,风速范围为1.3~2.5 m/s,相对湿度范围为60%~80%.③P2阶段SOR（硫氧化率）和NOR（氮氧化率）均为0.3,ρ（SNA）（SNA为SO₄2-、NO₃-和NH₄+的统称）为128.8 μg/m3,占ρ（PM_2.5）的56.2%;OM[有机质,ρ（OM）=ρ（POA）+ρ（SOA）,其中,POA为一次有机气溶胶,SOA为二次有机气溶胶]是除SNA以外的第二大组分,在P1和P3阶段ρ（POA）大于ρ（SOA）,而在P2阶段ρ（SOA）与ρ（POA）相等,均为28.0 μg/m3,表明在重污染过程中二次污染严重;整个污染过程ρ（NO₃-）/ρ（SO₄2-）为1.0,表明石家庄市移动源和固定源对ρ（PM_2.5）贡献相当.④WRF-Chem模型模拟结果表明,太阳辐射量、温度和大气边界层高度受气溶胶反馈效应的影响在P2阶段的下降量分别为75.1 W/m2、2.7℃和109.9 m,比P1阶段分别高33.6%、91.4%和18.6%,比P3阶段分别高147.0%、305.3%和24.1%.研究显示,此次静稳天气下的重污染过程二次污染严重,气溶胶反馈效应整体使得太阳辐射量、温度和大气边界层高度均向不利于污染扩散的趋势发展,造成石家庄市的ρ（PM_2.5）进一步增加.      

Molecular characterization of root exudates using Fourier transform ion cyclotron resonance mass spectrometry

The release of root exudates (REs) provides an important source of soil organic carbon. This work revealed the molecular composition of REs of different plant species including alfalfa (Medicago sativa L.), bean (Phaseolus vulgaris L.), barley (Hordeum vulgare L.), maize (Zea mays), wheat (Triticum aestivum L.), ryegrass (Lolium perenne L.) and pumpkin (Cucurbita maxima) using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The combination of positive ion mode (+ESI) and negative ion mode (-ESI) increased the number of the molecules detected by ESI FT-ICR MS, and a total of 8758 molecules were identified across all the samples. In detail, lipids and proteins and unsaturated hydrocarbons were more easily detected in +ESI mode, while aromatic compounds with high O/C were readily ionized in -ESI mode, and only 38% of the total assigned formulas were shared by -ESI and +ESI modes. Multivariate statistical analysis of the formulas indicated that the close related plants species secreted REs with similar molecular components. Moreover, the unsaturation degree and nitrogen content were the two key parameters able to distinguish the similarities and differences of molecular components of REs between plant species. The results provided a feasible analysis method for characterization of the molecular components of REs and for the first time characterized the molecular components of REs of a variety of plant species using ESI FT-ICR MS.     

京津冀典型城市一次重污染过程特征及边界层结构变化对其影响

为探究典型重污染过程的污染特征与大气边界层结构演变规律,基于PM_2.5采样数据、气象观测数据及WRF-Chem模式,以北京市和石家庄市2016年12月27日—2017年1月10日一次重污染过程为研究对象,对气象要素、PM_2.5化学组分、天气背景场、边界层结构演变特征,以及大气边界层结构变化对ρ(PM_2.5)及其主要化学组分的影响进行分析.结果表明:①研究期间,北京市和石家庄市ρ(PM_2.5)分别为(165.63±110.89)(247.67±95.22)μg/m3,石家庄市污染程度高于北京市;高空纬向环流和地面弱高压控制的天气背景场,低于1.75 m/s的风速以及超过75%的相对湿度是造成北京市与石家庄市重污染的不利气象条件.②重污染时段北京市与石家庄市SNA(SO₄2-、NO₃-、NH₄+三者的统称)与碳质组分(OC、EC)占比之和超过76%,是PM_2.5中的两大主要组分;重污染时段ρ(SNA)占比明显上升,北京市与石家庄市ρ(SNA)占比由非重污染时段的42.23%、45.93%分别升至重污染时段的58.87%、59.62%;北京市与石家庄市ρ(OC)/ρ(EC)分别为5.13、3.51,表明在重污染时段两城市存在明显的二次有机气溶胶污染.③WRF-Chem模式模拟结果表明,PM_2.5污染严重时北京市与石家庄市在300~500 m处均出现明显的逆温,垂直风场主要表现为低层偏南风顺时针向上切变为偏西风,切变高度在400~1 000 m,逆温层结与明显垂直风切变的边界层特征共同抑制了污染物的湍流与扩散.④北京市与石家庄市重污染时段的PBLH(Planetary Boundary Layer Height,大气边界层高度)日均值与非重污染时段相比分别下降了202、128 m,PBLH每下降100 m,北京市与石家庄市ρ(PM_2.5)分别上升18.81、29.85 μg/m3,PBLH下降是导致两城市ρ(PM_2.5)快速上升的重要因素.北京市与石家庄市的PBLH与PM_2.5组分质量浓度之间的相关性不同,北京市PBLH与ρ(SNA)的相关性高于与碳质组分质量浓度的相关性,石家庄市PBLH与ρ(EC)相关性最高,表明此次重污染过程中北京市PM_2.5污染特征以二次形成为主,而石家庄市以一次排放为主.研究显示,北京市与石家庄市此次重污染过程与大气边界层结构变化密切相关.