新时期城市安全风险防控实践探析——以成都为例

随着我国加快从"乡村社会"迈向"城市社会",城市安全问题成为了新时期亟待解答的"国家命题",分析了城市化与城市风险相关问题,提出了适合成都的安全风险预防指标体系,并以"技术防控"开发建设城市安全监测预警系统,以"标准防控"推动企业和公共领域安全管理标准化,以"群众防控"依托安全社区为载体,构建基层社区公共安全体系,为我国城市安全风险防控体系建设提供了宝贵经验和有益启示。     

巢湖流域河流鱼类群落的时空分布

基于2013年4月和10月对巢湖流域66个河道样点的调查数据,初步研究了巢湖流域河流鱼类群落的时空变化特征。主要研究结果显示,鱼类多样性无显著性的水系间、生态分区间的变化,但随季节和河流级别显著变化:10月份的个体数显著高于4月份,2级河流的物种数和个体数均显著大于1级、3级和4级河流。鱼类群落结构的季节动态显著,随生态分区显著变化,但不受水系、河流级别的显著影响。在二级生态分区水平上,仅西南森林生态亚区的鱼类群落结构与其他5个生态亚区的显著差异;宽鳍鱲、吻虾虎鱼等在西南森林生态亚区具有更高多度,而鲫、鰐、鲤等物种在其他生态亚区多度更高。     

川南山地林分变化对土壤物理性质和抗蚀性的影响

以川南天然林(TRL)及其转变成的毛竹林(MZL)、檫木林(CML)、柳杉林(LSL)、杉木林(SML)和水杉林(SSL)为对象,研究不同林分土壤物理性质和抗蚀性差异,以主成分分析法(ZCFM)和隶属函数法(LSHM)分别计算的土壤抗蚀性综合值Ⅰ(KSX-Ⅰ)和Ⅱ(KSX-Ⅱ)评价林分变化对土壤抗蚀性的影响,探索简便易行的土壤抗蚀性综合评价方法。结果表明,天然林转变为人工林后土壤物理性质和抗蚀性变差,呈现出有机质和0.25 mm水稳性团聚体含量、水稳性团聚体平均重量直径、团聚度、孔隙度及物理稳定性指数降低,而结构体破坏率、不稳定团粒指数、容重、分散率及侵蚀系数增加。各林分土壤KSX-Ⅰ和KSX-Ⅱ均呈现出TRLCMLSSLLSLMZLSML的规律变化。土壤抗蚀性指标间相关性均达到显著(p0.05)水平;土壤KSX-Ⅰ和KSX-Ⅱ之间呈显著相关关系(p0.05),且两者均与各抗蚀性指标间呈显著相关(p0.05)。说明天然林植被变化后会使土壤抗蚀性降低,影响原有植被水土保持功能,应该加强天然林及其生态功能保护;ZCFM和LSHM均可作为计算土壤抗蚀性综合值的有效方法,但考虑到计算过程的难易度,后者更简便易行。结果为土壤抗蚀性综合评价新方法的建立提供了参考。     

运动消耗对草鱼幼鱼游泳能力的影响

以草鱼幼鱼（体长80~97 cm，体重96~134 g）为研究对象，采用实验室专利装置研究了不同运动消耗状态下的草鱼幼鱼游泳能力。结果表明：在正常状态下草鱼幼鱼的临界游泳速度[WTBX]（Ucrit）为711±060 BL/s，耗氧率（MO2）与流速（U）方程拟合为MO2=4705+419U123，耗氧率随着流速的增大而增大，且草鱼的有氧运动效率较高。在4种运动消耗状态（06Ucrit、08Ucrit、10Ucrit、12Ucrit）流速下运动1 h草鱼的消耗后临界游泳速度（Upcrit）分别为：725±135、633±06、626±08、560±04 BL/s，临界游泳速度随着前期消耗流速的增大而减小，相应的耗氧率方程拟合为：MO2=38269+465U144，MO2=44526+4223U146，MO2=46611+4790U149，MO2=60034+3883U151。运动消耗会导致草鱼的有氧运动效率降低，同时随着运动消耗速度的增加有氧运动效率随之降低。研究结果认为在设计以草鱼为主要过鱼对象的过鱼设施时，鱼道内的流速不应大于08Ucrit，以使鱼类顺利通过。针对不同过鱼对象游泳特性进行设计的鱼道能够提高鱼类通过鱼道的效率     

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     

Development and Testing of 2D Finite Difference Model in Open Channels

This study develops a depth-averaged two-dimensional (2D) numerical model using a finite difference method (FDM) on a staggered grid. The governing equations were solved using the Marker and Cell method that was developed at the Los Alamos laboratories by Harlow and Welch in 1965. In the paper, an explicit FDM was used to solve the governing equations. A first-order approximation was used for the temporal derivative. Second-order central difference approximations were used for space discretization. The time step is limited by the Courant–Friedrichs–Lewy (CFL) condition. The time step used in this study depends on the grid spacing and velocity components in the x- and y-directions. The study is divided into two steps: the first step is to develop a depth-averaged 2D numerical model to simulate the flow process. The second constructs a module to calculate the bed load transport and simulate the river morphology in the areas that have steep slopes, torrents, and mountain rivers. Developed model was applied to the artificial channel and a flood event in the Asungjun River section of the mountainous Yangyang Namdae River (South Korea). General simulation results showed that the developed model was in good agreement with the observed data.     

The evolution of pollution profile and health risk assessment for three groups SVOCs pollutants along with Beijiang River,China

Three important groups of semi-volatile organic compounds (SVOCs), polycyclic aromatic hydrocarbons (PAHs), organic chlorinated pesticides (OCPs) and phthalate esters (PAEs), were produced by various human activities and entered the water body. In this study, the pollution profiles of three species including 16 PAHs, 20 OCPs and 15 PAEs in water along the Beijiang River, China were investigated. The concentrations of Σ₁₆PAHs in the dissolved and particulate phases were obtained as 69–1.5 × 10² ng L^?1 and 2.3 × 10³–8.6 × 10⁴ ng g^?1, respectively. The levels of Σ₂₀OCPs were 23–66 ng L^?1 (dissolved phase) and 19–1.7 × 10³ ng g^?1 (particulate phase). Nevertheless, higher levels of PAEs were found both in the dissolved and particulate phases due to abuse use of plastic products. Furthermore, non-cancer and cancer risks caused by these SVOCs through the ingestion absorption and dermal absorption were also assessed. There was no non-cancer risk existed through two kinds of exposure of them at current levels, whereas certain cancer risk existed through dermal absorption of PAHs in the particulate phase in some sampling sites. The results will show scientific insights into the evaluation of the status of combined pollution in river basins, and the determination of strategies for incident control and pollutant remediation.     

模拟降雨径流作用下红壤坡面侵蚀水动力学机制

土壤侵蚀过程受控于侵蚀外营力和土壤抗侵蚀性能,深入理解坡面流水动力学特性及其侵蚀动力是研究土壤侵蚀动力学机制的基础。利用可变坡土槽,通过不同雨强(60、90和120 mm/h)和径流冲刷(10、15和20 L/min)组合模拟试验,研究了第四纪黏土红壤坡面水流的水动力学特征参数及其与土壤侵蚀量间的关系。结果显示:降雨和径流冲刷影响了坡面产流产沙过程和坡面流水力学特性,其中平均流速v、平均水深h、雷诺数Re和水流功率ω均随降雨强度和上方来水流量的增加而增大,相对水深曼宁糙率n/h则减小,其水力学他参数(弗如德数Fr、阻力系数f和水流剪切力τ)变化规律不明显。坡面水流平均速度取值范围为0.21~0.45 m/s,平均水深取值范围为5.6~9.4 mm,在试验条件下红壤坡面侵蚀水流流态大部分均处于"紊流-急流区"。不论从径流角度看或是从泥沙角度分析,由相对水深和曼宁糙率系数两种水动力因子共同组成的复合水动力特征参数-相对水深曼宁糙率,是表征不同上方来水流量和降雨强度条件下第四纪粘土红壤坡面侵蚀特征的水动力参数。     

Microbial community composition and electricity generation in cattle manure slurry treatment using microbial fuel cells: effects of inoculum addition

Environmental Science and Pollution Research - Microbial fuel cell (MFC) is a sustainable technology to treat cattle manure slurry (CMS) for converting chemical energy to bioelectricity. In this...     

Changes in motorcycle-related injuries and deaths after mandatory motorcycle helmet law in a district of Vietnam

Objective: Our study measured the change in head injuries and deaths among motorcycle users in Cu Chi district, a suburban district of Ho Chi Minh City.

Methods: Hospital records for road traffic injuries (RTIs) were collected from the Cu Chi Trauma Centre and motorcycle-related death records were obtained from mortality registries in commune health offices. Head injury severity was categorized using the Abbreviated Injury Score (AIS). Rate ratios (RRs) were used to compare rates pre- and post-law (2005/2006–2009/2010). Cu Chi's population, stratified by year, age, and sex, was used as the denominator.

Results: Of records identifying the transportation mode at the time of injury, motorcyclists accounted for most injuries (3,035, 87%) and deaths (238, 90%). Head injuries accounted for 70% of motorcycle-related hospitalizations. Helmet use was not recorded in any death records and not in 97% of medical records. Males accounted for most injuries (73%) and deaths (88%). The median age was 28 years and 32 years for injuries and deaths, respectively. Compared to the pre-law period, rates of motorcycle injuries (RR = 0.53; 95% confidence interval [CI], 0.49–0.58), head injuries (RR = 0.35; 95% CI, 0.31–0.39), severe head injuries (RR = 0.47; 95% CI, 0.34–0.63), and deaths (RR = 0.69; 95% CI, 0.53–0.89) significantly decreased in the post-law period.

Conclusions: Rates of head injuries and deaths among motorcycle riders decreased significantly after implementation of the mandatory helmet law in Vietnam. To further examine the impact of the motorcycle helmet law, including compliance and helmet quality, further emphasis should be placed on gathering helmet use data from injured motorcyclists.