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991.
This paper reports a template-free method to synthesize a series of inorganic hollow spheres (IHSs) including Cu-1, Cu-2, Ni-1, Ni-2 based on mineralization reactions at water/“water-brother” interfaces. “Water-brother” was defined as a solvent which is miscible with water, such as ethanol and acetone. The water/“water-brother” interfaces are very different from water/oil interfaces. The “water-brother” solvent will usually form a homogenous phase with water. Interestingly, in our method, these interfaces can be formed, observed and utilized to synthesize hollow spheres. Utilizing the unique porous properties of the spheres, their potential application in water treatment was demonstrated by using Cu-1 IHSs as Fenton-like reagents for adsorption and decomposition of Congo Red from aqueous solution. The final adsorption equilibrium was achieved after 30 min with the maximum adsorption capacity of 86.1 mg/g, and 97.3% removal of the dye in 80 min after adsorption equilibrium. The IHSs can be reused as least 5 times after treatment by NaOH. This method is facile and suitable for large-scale production, and shows great potential for watertreatment. 相似文献
992.
Wenming Dong Jiamin Wan Tetsu K. Tokunag Benjamin Gilbert Kenneth H. Williams 《环境科学学报(英文版)》2017,29(7):24-32
In order to understand the transport and humification processes of dissolved organic matter(DOM) within sediments of a semi-arid floodplain at Rifle,Colorado,fluorescence excitation–emission matrix(EEM) spectroscopy,humification index(HIX) and specific UV absorbance(SUVA) at 254 nm were applied for characterizing depth and seasonal variations of DOM composition.Results revealed that late spring snowmelt leached relatively fresh DOM from plant residue and soil organic matter down into the deeper vadose zone(VZ).More humified DOM is preferentially adsorbed by upper VZ sediments,while non-or lesshumified DOM was transported into the deeper VZ.Interestingly,DOM at all depths undergoes rapid biological humification process evidenced by the products of microbial by-product-like(i.e.,tyrosine-like and tryptophan-like) matter in late spring and early summer,particularly in the deeper VZ,resulting in more humified DOM(e.g.,fulvic-acid-like and humic-acid-like substances) at the end of year.This indicates that DOM transport is dominated by spring snowmelt,and DOM humification is controlled by microbial degradation,with seasonal variations.It is expected that these relatively simple spectroscopic measurements(e.g.,EEM spectroscopy,HIX and SUVA) applied to depth-and temporally-distributed pore-water samples can provide useful insights into transport and humification of DOM in other subsurface environments as well. 相似文献
993.
为了模拟河流水生态系统演变,探讨热带河流浮游植物和浮游动物生物量在流量影响下的沿程变化规律,在求解河流二维浅水方程的基础上,考虑浮游动物、浮游植物、悬浮碎屑、无机氮、无机磷等输运和演变子模型以及各子模型间的耦合作用机制,构建水生态动力数学模型,并将该模型应用于我国热带河流—海南南渡江下游龙塘坝至入海口段(长约28 km).数学模型采用ADI-QUICK格式差分方法对水动力学方程和对流扩散方程进行离散求解,进而驱动各类生物变量输运和演化.通过对河流水面线高程、营养盐含量、浮游生物生物量模拟值与实测值加以对比进行验证.实证结果表明,在生态参数合理率定前提下,忽略河流流量的时间变化,采用丰水期、平水期和枯水期工况下的代表流量加以概化,数值模拟仍能获得局部河段浮游生物生物量模拟值与实测值整体相符合的结果.浮游植物和浮游动物生物量均沿水流方向逐渐降低,但随流量的增大整体上呈降低趋势,丰水期上游浮游生物生物量为下游的1.6倍,枯水期达到9.3倍.受海水入侵、沿程污染排放等因素的影响,枯水期浮游生物生物量模拟值与实测值的偏差远大于丰水期.枯水期河道浮游植物和浮游动物生物量模拟值的最大值分别为77.71和38.56 mmol/m3(均以C计),约为丰水期的3.8倍,说明枯水期水质富营养化风险远高于丰水期. 相似文献
994.
17α-Ethynylestradiol(EE2) in natural waters may cause adverse effects on organisms due to its high estrogenic potency. Laboratory studies were performed to study the effects of a local humic acid(LHA), fulvic acid(LFA) and Aldrich humic acid(AHA) on the photochemical behavior and estrogenic potency of EE2. Here photolytic experiments demonstrated that pure aqueous EE2 could undergo direct and self-sensitized photodegradation at a global rate of 0.0068 hr~(-1).Photodegradation rate of EE2 in 5.0 mg/L dissolved humic substances(DHS) was determined to be 0.0274, 0.0296 and 0.0254 hr~(-1) for LHA, LFA and AHA, respectively. Reactive oxygen species(ROS) and triplet dissolved humic substances(~3DHS*) scavenging experiments indicated that the promotion effect of DHS on EE2 photodegradation was mainly aroused by the reactions of HOU(35%–50%),~1O_2(10%) andDHS*(22%–34%). However, the photodegradation of EE2 could also be inhibited when DHS exceeded the threshold of 10 mg/L. Three hydroxylation products of EE2 were identified using GC–MS and their formation pathways were also proposed. In vitro estrogenicity tests showed that EE2 was transformed into chemicals without estrogenic potency. These findings could extend our knowledge on the photochemical behaviors of steroid estrogens in sunlit natural waters. 相似文献
995.
996.
建立了便携式GC-MS快速测定固定污染源废气中挥发性卤代烃方法,26种卤代烃内标定量工作曲线的相关系数r≥0.985,线性关系良好;精密度好,相对标准偏差2.33%~18.1%;准确度高,加标回收率为101%~134%;方法检出限为0.002 ppm~0.016 ppm.在实际现场监测固定污染源中挥发性卤代烃时,使用便携式GC-MS的速查(Survey)功能初步判断样品浓度,确定稀释倍数,并验证了气袋和玻璃注射器采样对挥发性卤代烃测定结果无显著性差异. 相似文献
997.
998.
为解决纳米零价金属在水中暴露出的极易聚集与氧化的问题,本研究使用铜作为纳米零价铁(NZVI)的复合金属,制得纳米Fe/Cu双金属,并用羧甲基纤维素钠(CMC)对其包覆改性.使用扫描电子显微镜、X射线衍射以及氮气吸附/脱附等温线对改性前后的双金属进行表征.结果表明,改性之后的材料具有更大的尺寸以及比表面积,且抗氧化性得到显著增强.材料的沉降实验以及对2,4-二氯苯酚(2,4-DCP)降解实验的结果揭示,CMC的包覆比对改性后双金属的分散性与反应活性影响较大.当包覆比为80%时,双金属的分散稳定性最强,释放的活性位点个数最多,表现为最高的反应活性.此时脱氯效率达到90.3%,且脱氯过程和产物发生明显改变. 相似文献
999.
A large female spider, Nephila jurassica, was described from Middle Jurassic strata of north-east China and placed in the modern genus Nephila (family Nephilidae) on the basis of many morphological similarities, but, as with many ancient fossils, the single specimen lacked synapomorphies of the family (Selden et al. 2011). In order to test the placement within the nephilid phylogenetic tree, Kuntner et al. (2013) calibrated the molecular phylogeny using N. jurassica in three different scenarios based on inferred mitochondrial substitution rates. They concluded that N. jurassica fitted better as a stem orbicularian than a nephilid. Now, a giant male spider has been discovered at the same locality that yielded N. jurassica. The two sexes are considered conspecific based on their similar morphological features, size, and provenance. The male cannot be accommodated in Nephilidae because of its pedipalp morphology, so the new genus Mongolarachne and family Mongolarachnidae are erected for the species. Comparison with possibly related families show that Mongolarachnidae is most likely on the orbicularian stem, close to other cribellate orbicularians (e.g., Deinopoidea), which suggests a greater diversity of cribellate orbicularians during the Middle Jurassic. 相似文献
1000.
温州城市降雨径流中BOD5和COD污染特征及其初始冲刷效应 总被引:2,自引:1,他引:1
为研究温州降雨径流污染情况,监测了温州2个采样区4场较为典型的降雨过程,测定了不同下垫面径流中BOD5和COD的浓度,并且计算出污染物的EMC值、M(V)曲线和BOD5/COD值等.结果表明,温州城市降雨径流中BOD5和COD的含量分别介于ND~69.21 mg.L-1和ND~636 mg.L-1之间,不同城市下垫面径流中BOD5和COD的含量均随着降雨历时的延长而呈下降趋势,处理初期径流水样对减少耗氧性有机污染具有重要意义.从COD和BOD5的EMC值来判断,部分城市下垫面降雨径流中污染物浓度超出地表五类水标准,甚至高于污水排放二级标准,此类降雨径流若直接入河将对下级受纳水体造成耗氧性有机污染的压力.根据M(V)累积曲线判断,COD初期冲刷效应在城市降雨径流中是较为普遍的,城市降雨径流中的BOD5表现出与COD类似的初始冲刷情况,该结果亦表明径流初期耗氧性有机污染严重.城市降雨径流中COD和BOD5的浓度受下垫面类型和降雨条件的影响,而BOD5/COD指标的变化特征则指出生物降解是削减有机污染负荷的有效途径之一,但不同下垫面径流有机污染的治理工作应采用不同的最佳管理方案(BMPs). 相似文献