水温分层对香溪河库湾浮游植物功能群季节演替的影响

三峡水库水环境问题近年来引起社会广泛关注，以浮游植物功能群为基础，通过对2010年1~12月香溪河库湾水温、浮游植物等进行跟踪监测，探究支流库湾浮游植物群落结构演替趋势及其影响因子。结果表明：香溪河库湾2010年共出现18个浮游植物功能群，其中B、X1、P、Y、X2、D、LO、J、MP、G是代表性功能群；水温分层的季节性发育和消失是浮游植物群落结构演替的主要影响因素；冬季以耐受水温及光照限制的CS/S策略藻种为主；春季弱分层时，CR/R策略藻种适宜生长；夏季汛期时，呈现CR/R/C/CS多种策略藻种混生格局，强分层时，适宜稳定生境的S型策略藻种占据优势；秋季分层被打破，群落结构演替为耐受频繁波动环境的R型群落格局占优势     

Impact of chemical leaching on permeability and cadmium removal from fine-grained soils

The aim of this study was to investigate the influence of chemical leaching on permeability and Cd removal from fine-grained polluted soils. Column leaching experiments were conducted using two types of soils (i.e., artificially Cd-polluted loam and historically polluted silty loam). Chemical agents of CaCl₂, FeCl₃, citric acid, EDTA, rhamnolipid, and deionized water were used to leach Cd from the soils. Results showed that organic agents reduced permeability of both soils, and FeCl₃ reduced permeability of loam soil, compared with inorganic agents and deionized water. Entrapment and deposition of colloids generated from the organic agents and FeCl₃ treatments reduced the soil permeability. The peak Cd effluence from the artificially polluted loam columns was retarded. For the artificially polluted soils treated with EDTA and the historically polluted soils with FeCl₃, Cd precipitates were observed at the bottom after chemical leaching. When Cd was associated with large colloid particles, the reduction of soil permeability caused Cd accumulation in deeper soil. In addition, the slow process of disintegration of soil clay during chemical leaching might result in the retardation of peak Cd effluence. These results suggest the need for caution when using chemical-leaching agents for Cd removal in fine-grained soils.

     

石油炼制项目竣工环保验收监测检查常见问题

根据建设项目竣工环境保护验收监测相关标准规范要求和实践经验,总结了石油炼制项目竣工环境保护验收监测实践工作中的若干常见问题。根据石油炼制项目污染物来源和特点,分析了加热炉废气监测、恶臭VOCs治理、含油污水监测、防渗措施和地下水监测以及污水处理"三泥"(含油污泥、气浮浮渣、剩余的废活性污泥)和碱渣处置等常见重点难点问题,在此基础上提出了一些对策和建议,为今后开展验收监测检查工作提供借鉴。     

基于IFS-动态加权的地下综合体深基坑施工风险评价

为控制地下综合体深基坑施工风险,提出了一种基于直觉模糊集(IFS)-动态加权的风险评价方法.从地质条件、建筑环境、岩土设计、施工方案和偶然风险5个方面分析地下综合体深基坑施工风险因素,构建了综合风险评价指标体系.采取施工风险5级划分方法,利用IFS理论确定指标风险;以偏大型正态加权函数确定指标权重,得到系统综合风险.以西安市某地下综合体深基坑施工实际为背景,进行方法应用.结果表明,该西安市地下综合体深基坑施工系统风险等级为显著风险.其中,指标"邻近建筑""地下管网"的风险等级为高度风险,"道路交通""基坑边坡稳定性""降排水实施"为显著风险,对此提出了相应的安全措施.     

Estimating and comparing greenhouse gas emissions with their uncertainties using different methods: A case study for an energy supply utility

Energy supply utilities release significant amounts of greenhouse gases (GHGs) into the atmosphere. It is essential to accurately estimate GHG emissions with their uncertainties, for reducing GHG emissions and mitigating climate change. GHG emissions can be calculated by an activity-based method (i.e., fuel consumption) and continuous emission measurement (CEM). In this study, GHG emissions such as CO₂, CH₄, and N₂O are estimated for a heat generation utility, which uses bituminous coal as fuel, by applying both the activity-based method and CEM. CO₂ emissions by the activity-based method are 12–19% less than that by the CEM, while N₂O and CH₄ emissions by the activity-based method are two orders of magnitude and 60% less than those by the CEM, respectively. Comparing GHG emissions (as CO₂ equivalent) from both methods, total GHG emissions by the activity-based methods are 12–27% lower than that by the CEM, as CO₂ and N₂O emissions are lower than those by the CEM. Results from uncertainty estimation show that uncertainties in the GHG emissions by the activity-based methods range from 3.4% to about 20%, from 67% to 900%, and from about 70% to about 200% for CO₂, N₂O, and CH₄, respectively, while uncertainties in the GHG emissions by the CEM range from 4% to 4.5%. For the activity-based methods, an uncertainty in the Intergovernmental Panel on Climate Change (IPCC) default net calorific value (NCV) is the major uncertainty contributor to CO₂ emissions, while an uncertainty in the IPCC default emission factor is the major uncertainty contributor to CH₄ and N₂O emissions. For the CEM, an uncertainty in volumetric flow measurement, especially for the distribution of the volumetric flow rate in a stack, is the major uncertainty contributor to all GHG emissions, while uncertainties in concentration measurements contribute a little to uncertainties in the GHG emissions.

Implications:Energy supply utilities contribute a significant portion of the global greenhouse gas (GHG) emissions. It is important to accurately estimate GHG emissions with their uncertainties for reducing GHG emissions and mitigating climate change. GHG emissions can be estimated by an activity-based method and by continuous emission measurement (CEM), yet little study has been done to calculate GHG emissions with uncertainty analysis. This study estimates GHG emissions and their uncertainties, and also identifies major uncertainty contributors for each method.     

Influence of filtration velocity on DON variation in BAF for micropolluted surface water treatment

Biological aerated filters (BAFs) are widely used for the treatment of micropolluted surface water. However, the biological process produces dissolved organic nitrogen (DON), which, as precursors of nitrogenous disinfection by-products, pose potential threats to drinking water safety. Therefore, to control DON in BAF effluent, it is necessary to study the influence of BAF operation parameters on DON production. In this study, the influence of filtration velocity in a BAF on DON production was investigated. Under different filtration velocity (0.5, 2, and 4 m/h) conditions, profiles of DON concentrations along the media layer were measured. The profile at a filtration velocity of 0.5 m/h showed a decreasing trend, and the ones under filtration velocities of 2 and 4 m/h fluctuated in a small range (from 0.1 to 0.4 mg/L). Moreover, the relatively high filtration velocities of 2 and 4 m/h resulted in a lower level of DON concentration. Additionally, 3D excitation-emission matrix fluorescence spectroscopy was used to characterize DON. It is found that the patterns of DON at a relatively high filtration velocity condition (4 m/h) were obviously different from the ones under low filtration velocity conditions (0.5 and 2 m/h).     

Investigation of titanium liquid/gas diffusion layers in proton exchange membrane electrolyzer cells

In a proton exchange membrane electrolyzer cell (PEMEC), liquid/gas diffusion layer (LGDL) is expected to transport electrons, heat, and reactants/products to and from the catalyst layer with minimum voltage, current, thermal, interfacial, and fluidic losses. In addition, carbon materials, which are typically used in PEM fuel cells (PEMFCs), are unsuitable in PEMECs due to the high ohmic potential and highly oxidative environment of the oxygen electrode. In this study, a set of titanium gas diffusion layers with different thicknesses and porosities are designed and examined coupled with the development of a robust titanium bipolar plate. It has been found that the performance of electrolyzer improves along with a decrease in thickness or porosity of the anode LGDL of titanium woven meshes. The ohmic resistance of anode LGDL and contact resistance between anode LGDL and the anode catalyst play dominant roles in electrolyzer performance, and better performance can be obtained by reducing ohmic resistance. Thin titanium LGDLs with straight-through pores and optimal pore morphologies are recommended for the future developments of low-cost LGDLs with minimum ohmic/transport losses.     

GIS罐体内部异物清理机器人的研发与应用

针对气体绝缘金属封闭开关设备( gas insulated switchgear, GIS)内部异物颗粒引起设备内部电场畸变,从而造成设备闪络故障问题,通过对异物颗粒的产生原因及影响因素进行分析,研制了一种GIS罐体内部异物颗粒清理机器人,实现了GIS设备内部可视化异物清理功能。应用结果表明:机器人检测不仅提高了750kV GIS内部缺陷检查的效率,而且保证了检测人员的安全,为GIS状态检修提供了有效技术支持。     

锐钛矿-金红石混合晶型TiO2降解气相苯

用溶胶-凝胶法并通过控制煅烧温度合成不同晶相比的混合晶型纳米TiO_2,在紫外光光照下降解气相苯。考察了苯初始质量浓度、紫外灯光照强度和催化剂加入量对苯去除率的影响;探究了光催化降解气相苯的动力学特征。结果表明:450℃煅烧制备的催化剂降解苯效率最高,此催化剂金红石相质量分数为6.30%;在苯初始质量浓度为74.39 mg/m~3、催化剂加入量为7 g、光照强度为2.18 klux的最佳条件下反应84 min,苯去除率达99.73%;光催化降解率与光照强度之间符合0.5级动力学特征;当催化剂加入量为3 g时,单位时间单位质量催化剂降解苯的质量最多;苯的光催化降解反应均符合一级动力学方程。