溴掺杂TiO_2光催化剂的制备与性能研究

以KBr和Ti(SO4)2为原料,通过水热法制备了高催化活性的溴掺杂纳米TiO2(Br-TiO2)光催化剂,利用XRD、XPS、TEM、BET和UV-Vis DRS等测试手段对其进行了表征。通过苯酚降解实验评价了Br-TiO2的光催化活性。结果表明,700℃焙烧、溴与钛的摩尔比为0.35∶1时,Br-TiO2具有最佳光催化活性。该催化剂为晶体发育完整的锐钛矿相TiO2,粒径平均大小为50 nm,比表面积为16.81 m2/g,在紫外区的吸收得到加强,光催化能力优于Degussa P-25。确定了降解苯酚的最佳条件:催化剂投加量为0.5 g/L,苯酚初始浓度为10 mg/L,pH值为6.0。     

基于随机化Pushover的结构整体抗震可靠度参数分析

为了研究使用随机化Pushover方法进行RC框架结构整体抗震可靠度计算过程中相关参数的适应性,使用Matlab调用SAP2000编制出基于随机化Pushover的结构整体抗震可靠度程序,以一榀11层RC框架结构为例,通过该程序统计出不同参数下结构最大层间位移角的分布情况及整体失效概率,并以大样本实际地震波进行时程分析所统计出的相应结果为基准进行对比。结果表明,在常规参数设置下随机化Pushover方法统计出的最大层间位移角分布情况和结构整体失效概率与大样本时程分析结果有较大差异,然后提出了一种修正方式,有效地减小了两者的差异,并以某算例验证了该修正方式的适用性。     

The littoral zone in the Three Gorges Reservoir, China: challenges and opportunities

For flood control purpose, the water level of the Three Gorges Reservoir (TGR) varies significantly. The annual reservoir surface elevation amplitude is about 30 m behind the dam. Filling of the reservoir has created about 349 km² of newly flooded riparian zone. The average flooding period lasts for more than 6 months, from mid-October to late April. The dam and its associated reservoir provide flood control, power generation, and navigation, but there are also many environmental challenges. The littoral zone is the important part of the TGR, once its eco-health and stability are damaged,which will directly endanger the ecological safety of the whole reservoir area and even the Yangtze River Basin. So, understanding the great ecological opportunities which are hidden in littoral zone of TGR (LZTGR) and putting forward approaches to solve the environmental problems are very important. LZTGR involves a wide field of problems, such as the landslides, potential water pollution, soil erosion, biodiversity loss, land cover changes, and other issues. The Three Gorges dam (TGD) is a major trigger of environmental change in the Yangtze River. The landslides, water quality, soil erosion, loss of biodiversity, dam operation, and challenge for land use are closely interrelated across spatial and temporal scales. Therefore, the ecological and environmental impacts caused by TGD are necessarily complex and uncertain. LZTGR is not only a great environmental challenge but also an ecological opportunity for us. In fact, LZTGR is an important structural unit of TGR ecosystem and has special ecosystem services function. Vegetation growing in LZTGR is therefore a valuable resource due to accumulation of carbon and nutrients. Everyone thinks that the ecological approach to the problem is needed. If properly designed, dike–pond systems, littoral woods systems, and re-created waterfowl habitats will have the capacity to capture nutrients from uplands and obstruct soil erosion. Ecological engineering approaches can therefore reduce environmental impacts of LZTGR and optimize ecological services. In view of the current situation and existing ecological problems of LZTGR, according to function demands such as environmental purification, biodiversity conservation, and vegetation carbon sink enhancement, we should explore the eco-friendly utilization mode of resources in LZTGR. Ecological engineering approaches might minimize the impacts or optimize the ecological services. Natural regeneration and ecological restoration in LZTGR are valuable for soil erosion decrease, pollutant purification, biodiversity conservation, carbon sink increase, and ecosystem health maintenance in TGR.     

Spatial distribution and ecological risk assessment of heavy metals in surface sediments from a typical plateau lake wetland, China

Surface sediment (0-15 cm) samples were collected from 31 different grid points throughout the Yilong Lake in April 2004. Samples were subjected to a total digestion technique and analyzed for As, Cd, Cr, Pb, Ni, Cu, and Zn in order to study spatial distribution characteristics based on Kriging method and assess their ecological risks posed by these heavy metals. Results showed that the mean concentrations of these heavy metals were lower than potential effect levels. Patches of higher heavy metal concentrations occurred in the inflow area of the Cheng River and northeast area nearby the road and railway. The higher concentrations of As and Cr also appeared in the east area (lake outlet), while the patches of lower concentrations were uniformly distributed at the southwest corner between Luosewan and Xiaoguoxi. The heavy metal loads such as As, Cd and Pb might come from the common sources due to industrial sewage and traffic pollution, while higher concentrations of Ni, Cr, and Zn in these sediments were dominated by parent rocks. However, Cu originated from both sources. Sediments with respect to As, Cd and Cu were grouped below the effect range low (ERL) at all sites, and with respect to Cr and Pb were grouped into the range from ERL to the effect range median (ERM) at more than 50% of sampling sites. The mean heavy metal toxic units in the Yilong Lake decreased following the order Pb > Cr > As > Ni > Zn > Cd > Cu, with higher contributions to the sum of toxic units of Pb, Cr and As.     

Predicting China's cultivated land resources and supporting capacity in the twenty-first century

In recent years, China's cultivated land has been shrinking, a change which has become one of the potential challenges to national sustainable development and global food security. In our research, we have predicted China's cultivated land resources for the next 50 years, based on scrutiny of systematic data and analyses of the loss of cultivated land. We have also designed an indicator of cultivated land equivalent per capita (CLEPC) to assess the capacity of cultivated land to support our population. The results show that China's cultivated land will decline to a minimum of 113.31 million ha between 2001–2010, while cultivated land per capita will decline from 0.101 ha to 0.083 ha. After 2010, the area of cultivated land will begin to increase slowly to 118.98 million ha in 2050. However, cultivated land per capita will still decline to 0.079 ha between 2010–2030; after 2030, it will start to increase and reach 0.085 ha in 2050. In contrast to the total area and per capita area of cultivated land, the CLEPC will remain at 0.101 ha between 2001–2010, and then increase to 0.156 ha in 2050. Overall, there will be increasing stress on China's cultivated land during the next two or three decades. Although the supporting capacity of cultivated land may not decline obviously with improvement in agricultural technology and infrastructure, China has to make great efforts to reduce the loss of cultivated land and to improve its productivity to ensure food security in the near future.     

水环境质量模糊综合评价中的一些问题探讨

水环境质量评价,对于正确了解水环境现状,合理利用与开发水环境资源,科学预测未来水环境变化趋势具有重要意义.建立在模糊集合论基础上的模糊综合评价法是评价水环境质量的一种新方法.与常规评价方法相比,模糊综合评价方法有其突出的优点,因此,日益受到环境评价工作者的重视.国内已有工作发表.我们就水环境质量评价的特点与模糊综合评价方法中的一些问题进行探讨.     

我国山岭公路汽车CO、HCs和NOx排放系数

在１５６０ｍ 长的甘肃七道梁山岭公路隧道内设监测点,对进入隧道内汽车排出的污染物浓度、交通量、车种以及气象条件进行采样分析、计数、分类和观测．根据在隧道内实测数据,用建立的隧道空气质量方程计算出我国高海拔山岭公路汽车单车ＣＯ、ＨＣｓ和ＮＯ_x 排放系数分别为４１．８６１±２６．１０１、５．３６７±３．１５８和３．８８３±１．９４３ｇ／（ｋｍ ·ｖｅｈ）．与国外成果相比,我国山岭公路汽车ＣＯ和ＨＣｓ排放系数明显高于国外发达国家汽车的排放水平,而ＮＯ_x 排放量低于一些发达国家     

HSY算法在水质模型参数识别中的应用探讨

参数识别是水质模拟中的技术核心，数据稀缺是水质模型经常面临的问题。采用HSY算法可求得模型参数的分布，而不再是一个单一的最优参数，从而在一定程度上避免了由于“最优”参数失真带来的决策风险，本文以南水北调一期工为例，讨论了在稀疏数据条件下如何应用HSY算法识别CSTR水质模型的参数，并对识别的模型参数进行了检验。模型检验采取了2种方法：分别用动态和稳态计算方法得出的参数进行比较；用模拟结果分布于实测值进行比较。结果表明，HSY算法为稀疏数据条件下进行识别、建立数学模型提供了一条有效的途径。     

垃圾渗滤液对潮滩沉积物营养盐污染影响研究

以上海市老港垃扭填埋场附近潮滩为例,研究了垃圾渗滤液的排放对潮滩沉积物营养盐污染负荷的影响,结果表明：由于垃圾渗滤液的排放,潮滩表层沉积物中营养盐N、P的含量显著增加;在向海向上,随距排污口距离的增加表层沉积物中N、P的含量有所降低;受垃圾填埋时间长短的影响。南北线潮滩沉积物中N、P的含量有明显差异,北线沉积物中总无机氮和总无机磷的含量均明显高于南线。柱样沉积物中N、P的含量随深度也呈现一定的变化规律：氨氮含量随深度的增加而增加,总磷含量随深度的增加而减少。