沙蚕生物扰动对河口沉积物中菲释放的影响

生物扰动是一个重要沉积物-水界面过程,影响沉积物中污染物的归趋.为了探究生物扰动对沉积物中多环芳烃释放的影响.在室内进行30 d的沙蚕生物扰动对河口沉积物中菲释放的影响实验.结果表明,相对于对照,生物扰动提高水体中颗粒态菲达到2.96~10.35倍,溶解态菲为9.55~17.44倍.由此可见,沙蚕的生物扰动极大的促进了沉积物中菲向水体释放.在生物扰动处理中,两种形态的菲所占比例不同,其中溶解态菲占释放总量的80%以上,表明沙蚕的生物扰动主要是提高水体中溶解态菲.由于溶解态菲能被生物所利用,通过食物链威胁人类健康.因此,沙蚕生物扰动造成的沉积物中的污染物释放具有潜在的生态风险.     

Graphene-supported nanoscale zero-valent iron：Removal of phosphorus from aqueous solution and mechanistic study

Excess phosphorus from non-point pollution sources is one of the key factors causing eutrophication in many lakes in China,so finding a cost-effective method to remove phosphorus from non-point pollution sources is very important for the health of the aqueous environment. Graphene was selected to support nanoscale zero-valent iron(nZVI)for phosphorus removal from synthetic rainwater runoff in this article. Compared with nZVI supported on other porous materials,graphene-supported nZVI(G-nZVI) could remove phosphorus more efficiently. The amount of nZVI in G-nZVI was an important factor in the removal of phosphorus by G-nZVI,and G-nZVI with 20 wt.% nZVI(20% G-nZVI)could remove phosphorus most efficiently. The nZVI was very stable and could disperse very well on graphene,as characterized by transmission electron microscopy(TEM) and scanning electron microscopy(SEM). X-ray photoelectron spectroscopy(XPS),Fourier Transform infrared spectroscopy(FT-IR) and Raman spectroscopy were used to elucidate the reaction process,and the results indicated that Fe-O-P was formed after phosphorus was adsorbed by G-nZVI. The results obtained from X-ray diffraction(XRD) indicated that the reaction product between nZVI supported on graphene and phosphorus was Fe3(PO4)2·8H2O(Vivianite). It was confirmed that the specific reaction mechanism for the removal of phosphorus with nZVI or G-nZVI was mainly due to chemical reaction between nZVI and phosphorus.     

Effects of extracellular polymeric substances on aerobic granulation in sequencing batch reactors

The effects of extracellular polymeric substances on aerobic granulation in sequencing batch reactors were investigated by evaluating the content and compositions of extracellular polymeric substances, and the relationship between extracellular polymeric substances composition and surface properties of glucose-fed aerobic granules. The results showed that extracellular polymeric substances could affect surface properties of cells, such as surface charge and hydrophobicity, enhance polymeric interaction and promote aerobic granulation. Moreover, extracellular polymeric substances were produced mainly in the exponential phase, and served as carbon and energy source in starvation phase during granulation process, thus regulating the growth of bacteria in the interior and exterior of granules, and maintaining the integrality of granules.     

1991／1992年世界气象灾害评述

1991/1992年是厄尔尼诺年,也是全球自然灾害频发、重灾事件突出的异常年份。本文对发生在1991/1992年厄尔尼诺事件期间的全球主要气象灾害进行简介和评述。     

楼板对钢筋混凝土框架结构受力性能影响

汶川8级地震震害调查发现,这次地震中现浇钢筋混凝土框架结构多发生"强梁弱柱"型破坏,这与规范中"强柱弱梁"抗震设计原则相悖。为探究其原因,采用ABAQUS软件对钢筋混凝土带楼板框架和空框架结构进行了侧向加载情况的性能分析。通过对比纵向梁端钢筋应力变化和柱端钢筋应力变化,以及分析不同侧向位移对应的楼板钢筋的应力变化情况,指出楼板对梁端抗负弯矩能力的增强有很大贡献。研究了节点类型、楼板钢筋材性、侧向位移、梁高、梁跨和板厚等因素对纵向梁端处楼板有效宽度的影响规律,提出了负弯矩作用下梁端处楼板有效宽度的取值方法。     

突发事件连锁反应的实证研究——以2008年初我国南方冰雪灾害为例

从突发事件连锁反应分析,认为2008年初我国南方的冰雪灾害是由自然灾害引发的连锁反应事件。选择了新浪网冰雪灾害报道专题的近4 000篇报道作为数据源,从时间、空间和事件角度揭示了此次冰雪灾害的演化过程,并分析了事件扩散的原因。     

Effects of perfluorooctanoic acid and perfluorooctane sulfonate on acute toxicity,superoxide dismutase,and cellulase activity in the earthworm <Emphasis Type="Italic">Eisenia fetida</Emphasis>

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are the two best-known perfluorinated chemicals and have received much attention due to their ubiquity in the environment. In the present study, we evaluated the effects of PFOS and PFOA on acute toxicity, superoxide dismutase (SOD), and cellulase activities in Eisenia fetida. The results of acute toxicity testing using a filter paper contact test and a natural field soil test showed that PFOA and PFOS exhibited acute toxicity in earthworms, and the toxic effect of PFOS was greater than that of PFOA. The results also showed that avoidance behavior is a more sensitive and easy operation biomarker than acute toxicity and will give us information for early diagnosis of soil pollution, well before the lethal effect becomes apparent. Subchronic exposure to PFOA or PFOS resulted in changes in SOD and cellulase activities in E. fetida, and SOD activity was more sensitive than cellulase activity during early exposure. Based on these findings, we suggest that avoidance behavior and SOD activity in earthworms are suitable biomarkers for evaluating the toxicity of PFOA- and PFOS-contaminated soils. These results indicate that exposure to PFOA and PFOS has a potential impact on soil animals and their environment.     

Promotional effect of rare earth-doped manganese oxides supported on activated semi-coke for selective catalytic reduction of NO with NH3

Environmental Science and Pollution Research - A composite catalyst for the selective catalytic reduction (SCR) of NOx with NH3 is investigated, in which the rare earth (RE, including La, Ce, Pr,...     

岩质边坡开挖卸荷岩体参数特征分析∗

岩质边坡的开挖卸荷过程直接决定工程施工的安全性,边坡变形特征分析及有效数值模拟方法的选取至关重要。基于卸荷岩体力学理论与方法,开展红砂岩试件的室内常规三轴与三轴卸荷试验,分析其变形特征、卸荷量与变形模量之间的关系以及强度参数的变化规律,结合有限单元法构建考虑卸荷作用的算例模型,探究考虑边坡开挖卸荷作用所引起的应力释放后的岩体劣化分区问题,以及边坡动态开挖卸荷下的变形分析。研究结果表明：①当卸荷量达70% 和临近破坏时,其变形模量分别降低了10% 和50% 左右;②岩样卸荷力学状态下粘聚力有所降低,内摩擦角有所增高;③依据边坡初始应力场与开挖后应力场的对比分析从而确定强、弱卸荷影响区,算例模型表明考虑卸荷作用后水平位移净增量计算结果为不考虑卸荷作用计算结果的4 倍左右,且其分步开挖支护效果显著,计算结果更加符合工程实际。研究成果可对边坡岩体开挖卸荷数值计算提供一定的指导意义。     

多元资源型县域循环型系统构建——以辽宁省灯塔市为例

从经济发展背景与循环经济内涵入手,提出发展循环经济是多元资源型县域的现实选择。以辽宁省灯塔市为例,构建以循环型工业、循环型农业、循环型社会体系为主体的循环经济体系框架,并指出建立工业生态链、引入静脉产业和实现土地资源的有效循环利用是完善循环经济体系的必要内容。