Elevated CO2 changes the moderate shade tolerance of yellow birch seedlings

To demonstrate the existence of light thresholds in plant growth and to examine the effects of elevated CO2 on the shade tolerance of a tree species, an experiment consisting of a completely randomized design for a total of 96 yellow birch (Betula alleghaniensis Britton) seedlings was conducted with 3 light levels (2.9%, 7.7%, 26.1% of full sunlight)×2 CO2 levels (350 and 700±10 ppm) with 4 replications in a phytotron. The study proved that thresholds exist and they vary in different plant organs. In ambient CO2, the thresholds were 13.3%, 18.7%, 15.0%, 15.2%, and 15.6% of full sunlight for stem, leaf, root, total plant biomass, and the averaged value, respectively. In 700 ppm CO2, the corresponding thresholds were 16.7%, 21.3%, 18.1%, 21.7% and 19.5% for stem, leaf, root, total plant biomass, and the averaged value, respectively. The lowest threshold in the stem is an indicator of the minimal light intensity for regular growth for seedlings of this species. Below this threshold, light-stressful growth occurs. The result of a paired t-test indicated that the thresholds in elevated CO2 were significantly higher than in ambient CO2. This suggests that yellow birch will lose its moderate shade tolerance, evolutionally becoming a shade-intolerant species, and that it may become more difficult to naturally regenerate in the future.     

底泥厌氧环境和光照对菹草萌发和幼苗生理的影响

通过向底泥中投加不同量的蔗糖使其发生厌氧反应以模拟不同程度的底泥厌氧环境，研究这种环境和光照强度对菹草石芽萌发和幼苗生理作用的影响。实验结果表明，底泥厌氧环境能显著降低菹草石芽的最终萌发率，且低光照会加剧这种趋势；尽管低光照不一定会提高最终的萌发率，但对提早石芽的萌发是有利的。在01%蔗糖投加处理中，幼苗的叶绿素和可溶性蛋白含量最高(平均为250和1928 mg/g FW)，其后随投加量的升高而降低，而游离氨基酸的含量却一直呈上升趋势，最高时达到024 mg/g FW ，但低光照却使它下降；可溶性糖含量基本不受底泥厌氧水平的影响，但随着光照减少而降低。随着厌氧水平的增加（从对照到05%蔗糖投加量），菹草的超氧物歧化酶(SOD)活性呈现上升趋势，但在10%蔗糖投加处理中活性降至最低；而过氧化物酶(POD)活性一直处于下降趋势。研究结论是：底泥厌氧对菹草石芽萌发影响显著，这种影响可能比低光照的限制作用还要重要。轻度的厌氧环境反而能促进菹草幼苗的生理代谢，但随厌氧水平的升高对碳氮平衡和其它生理活动产生不利影响。此外，底泥厌氧环境对菹草幼苗的抗氧化系统也有明显刺激作用。     

MACROPHYTE STANDING CROP AND PRIMARY PRODUCTWITY IN SOME FLORIDA SPRING-RUNS1

ABSTRACT: A survey of 31 Florida spring-runs was conducted to estimate their submerged macrophyte standing crop and primary productivity. The standing crops of submerged vegetation were not significantly (p > 0.05) correlated to either total nitrogen (r = 0) or total phosphorus (r =?0.20) concentrations, but standing crops were significantly (p < 0.01) correlated to the percentage of the spring-run's water surface shaded by marginal vegetation (r =?0.76). Maximum daily rates of primary productivity were positively correlated with average submerged macrophyte standing crops (r = 0.81; p < 0.001) and inversely correlated with the degree of shading by marginal vegetation (r =? 0.43; p < 0.05).     

Preparation of floating BiOCl0.6I0.4/ZnO photocatalyst and its inactivation of Microcystis aeruginosa under visible light

Frequent occurrence of harmful algal blooms has already threatened aquatic life and human health. In the present study, floating BiOCl_0.6I_0.4/ZnO photocatalyst was synthesized in situ by water bath method, and and applied in inactivation of Microcystis aeruginosa under visible light. The composition, morphology, chemical states, optical properties of the photocatalyst were also characterized. The results showed that BiOCl_0.6I_0.4 exhibited laminated nanosheet structure with regular shape, and the light response range of the composite BZ/EP-3 (BiOCl_0.6I_0.4/ZnO/EP-3) was tuned from 582 to 638 nm. The results of photocatalytic experiments indicated that BZ/EP-3 composite had stronger photocatalytic activity than a single BiOCl_0.6I_0.4 and ZnO, and the removal rate of chlorophyll a was 89.28% after 6 hr of photocatalytic reaction. The photosynthetic system was destroyed and cell membrane of algae ruptured under photocatalysis, resulting in the decrease of phycobiliprotein components and the release of a large number of ions (K⁺, Ca²⁺ and Mg²⁺). Furthermore, active species trapping experiment determined that holes (h⁺) and superoxide radicals (·O₂⁻) were the main active substance for the inactivation of algae, and the p-n mechanism of photocatalyst was proposed. Overall, BZ/EP-3 showed excellent algal removal ability under visible light, providing fundamental theories for practical algae pollution control.     

O3/UV降解水中的乙酸和硝基苯

利用O3 /UV和O3/H2O2降解了水中的乙酸,结果表明,在相同条件下处理60min后,O3/UV对乙酸的去除率仅比单独臭氧化处理提高了3%,而O3/H2O2在此条件下完全降解乙酸.O3/UV在处理硝基苯过程中却显示较好的氧化降解能力,通过分析表明,硝基苯降解过程中所产生的副产物H2O2对有机物的去除具有很重要的作用.因此,O3/UV氧化降解能力的提高可能有2方面的原因,紫外光对有机物的活化作用;中间产物H2O2催化臭氧分解产生了高活性的羟基自由基. 单独紫外光催化臭氧分解产生羟基自由基的效率极低.     

紫外分光光度法同时定量测定多组分混合物——喹啉 吡啶 吲哚 苯酚

借助ＧＷ—７５１紫外可见分光光度计，采用紫外分光光度法，根据吸光度的加和性，通过解联立方程组对焦化废水中的几种有代表性的有机物喹啉，吡啶，吲哚，苯酚的混合物进行了分析测定，相对误差一般小于１０％。此法的优越性在于不需要任何复杂的分离程序（如萃取，色谱等分离技术）便能直接求得混合物中各组分的含量     

复配絮凝剂在餐饮废水中的应用研究

将聚丙烯酰胺 (PAM)和聚铁 (PFS)进行复配 ,分别以COD值和透光脉动值 (R)为技术指标 ,探讨了在处理餐饮废水过程中各种变化条件对絮凝效果的影响。结果表明 :PAM与PFS有一最佳复配比例 ,COD去除率达 90 %以上 ;在此絮凝剂条件下 ,投加方式、搅拌速度和浓度等对R值都有显著影响。     

载银TiO_2可见光降解活性蓝染料废水研究

以溶胶-凝胶法制备了Ag/TiO2纳米催化剂,以日光色镝灯为光源,研究了活性蓝M-2GE模拟染料废水的可见光降解,考察了不同条件对可见光降解的影响。实验结果表明,该方法制备的TiO2、Ag/TiO2催化剂粒径约20～30nm,主要以锐钛矿相存在;光催化反应的最佳条件为:催化剂载Ag量2%,投加量为2g/L,pH值在2～6;在最佳的反应条件下,活性蓝的脱色率达98%,TOC去除率达70%;在实验的浓度范围内,服从一级反应动力学,随着染料溶液浓度的增大,表观速率常数不断降低。     

紫外线消毒技术在污水处理中的应用

介绍了紫外消毒的机理、影响紫外消毒的因素以及紫外消毒装置的基本结构形式。阐述了紫外消毒的现状和应用前景 ,提出紫外消毒可能取代传统的化学消毒法 ,在污水处理 ,特别是回用水的处理中得到广泛的应用。     

高浓度复合型聚铁硅絮凝剂PFSS和PSFS的形态分布研究

采用紫外分光光度法、逐时络合比色法和红外图谱从不同角度对高浓度聚合硫酸铁硅和聚合硅酸铁的形态分布及转化规律进行了探讨。紫外吸收表明,聚铁硅絮凝剂中主要以Fe(OH)+2、Fe2(OH)4+2等二聚体为主,而且还有三聚体或其他聚合形态的存在;逐时络合分析显示,复合型聚铁硅体系中硅形态以Si(c)为主,铁形态以Fe(a)和Fe(c)为主;红外图谱证实高浓度聚铁硅是以羟桥为主结构连接的高分子复合物,在1100cm-1附近M—OH—M的振动证明有铁羟基及其聚合态存在,且其形态区别于PFS。