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991.
黄小玲 《湖南环境生物职业技术学院学报》2005,11(1):20-21,24
鸭瘟是对养鸭业危害很大的一种病毒性传染病,具有高度的传染性和致死率.常见有肿头、流泪、体温升高的典型症状以及消化道充血、出血、纤维素性坏死性炎症和肝脏坏死灶、出血等典型病变.本文报告一例鸭瘟病例的发病和诊断. 相似文献
992.
二氧化氯对水中病毒、藻类和浮游动物的失活效果 总被引:13,自引:1,他引:13
本文研究了二氧化氯对水中一些主要病毒、藻类和浮游动物的失活效果,以及在不同消毒剂投量、接触时间和pH值等条件下,二氧化氯(ClO_2)对水体中一些微生物的杀灭和失活效果.与液氯对比的结果表明:ClO_2对藻类失活效果优于或相当于液氯;ClO_2对病毒和浮游动物的失活效果显著优于液氯;ClO_2可在一广泛的pH值范围内杀灭微生物.此外,还从理论上初步探讨了ClO_2对病毒的失活机理.研究结果表明,ClO_2是一种优良的液氯替代消毒剂,这对开展ClO_2的研究及其应用有重要意义. 相似文献
993.
Transport and transformation of sulfur compounds over East Asia during the TRACE-P and ACE-Asia campaigns 总被引:4,自引:0,他引:4
Meigen Zhang Itsushi Uno Yasuhiro Yoshida Yongfu Xu Zifa Wang Hajime Akimoto Timothy Bates Trish Quinn Alan Bandy Byron Blomquist 《Atmospheric environment (Oxford, England : 1994)》2004,38(40):6947
On the basis of the recently estimated emission inventory for East Asia with a resolution of 1×1°, the transport and chemical transformation of sulfur compounds over East Asia during the period of 22 February through 4 May 2001 was investigated by using the Models-3 Community Multi-scale Air Quality (CMAQ) modeling system with meteorological fields calculated by the regional atmospheric modeling system (RAMS). For evaluating the model performance simulated concentrations of sulfur dioxide (SO2) and aerosol sulfate (SO42−) were compared with the observations on the ground level at four remote sites in Japan and on board aircraft and vessel during the transport and chemical evolution over the Pacific and Asian Pacific regional aerosol characterization experiment field campaigns, and it was found that the model reproduces many of the important features in the observations, including horizontal and vertical gradients. The SO2 and SO42− concentrations show pronounced variations in time and space, with SO2 and SO42− behaving differently due to the interplay of chemical conversion, removal and transport processes. Analysis of model results shows that emission was the dominant term in regulating the SO2 spatial distribution, while conversion of SO2 to SO42− in the gas phase and the aqueous phase and wet removal were the primary factors that controlled SO42− amounts. The gas phase and the aqueous phase have the same importance in oxidizing SO2, and about 42% sulfur compounds (25% in SO2) emitted in the model domain was transported out, while about 57% (35% by wet removal processes) was deposited in the domain during the study period. 相似文献
994.
为定量评估突发公共卫生事件下的公交暴露风险,基于公交线网、交通分析区及新型冠状病毒肺炎(COVID-19)疫情信息等多源数据,考虑公交站点、交通分析区及疫情场所3种研究尺度,集成公交网络结构拓扑模型、公交网络中心性模型及核密度分析等空间分析方法,提出公交暴露风险的多尺度辨识方法,并以深圳市为例进行验证。结果表明:公交站点暴露风险在空间上呈现多中心—圈层结构,较高及高暴露风险站点多为交通枢纽、商场等,占比达26.40%;较高及高暴露风险交通分析区主要分布在工业、商业聚集区及居民点密集区,占比达32.84%;较高及高暴露风险疫情场所主要集中在城市核心区域,占比为28.92%。 相似文献
995.
Kouznetsov MY Roodsari R Pachepsky YA Shelton DR Sadeghi AM Shirmohammadi A Starr JL 《Journal of environmental management》2007,84(3):336-346
Hillslope vegetated buffers are recommended to prevent water pollution from agricultural runoff. However, models to predict the efficacy of different grass buffer designs are lacking. The objective of this work was to develop and test a mechanistic model of coupled surface and subsurface flow and transport of bacteria and a conservative tracer on hillslopes. The testing should indicate what level of complexity and observation density might be needed to capture essential processes in the model. We combined the three-dimensional FEMWATER model of saturated-unsaturated subsurface flow with the Saint-Venant model for runoff. The model was tested with data on rainfall-induced fecal coliforms (FC) and bromide (Br) transport from manure applied at vegetated and bare 6-m long plots. The calibration of water retention parameters was unnecessary, and the same manure release parameters could be used both for simulations of Br and FC. Surface straining rates were similar for Br and bacteria. Simulations of Br and FC concentrations were least successful for the funnels closest to the source. This could be related to the finger-like flow of the manure from the strip along the bare slopes, to the transport of Br and FC with manure colloids that became strained at the grass slope, and to the presence of micro-ponds at the grassed slope. The two-dimensional model abstraction of the actual 3D transport worked well for flux-averaged concentrations. The model developed in this work is suitable to simulate surface and subsurface transport of agricultural contaminants on hillslopes and to evaluate efficiency of grass strip buffers, especially when lateral subsurface flow is important. 相似文献
996.
危险品道路运输选线问题分析 总被引:17,自引:6,他引:11
从运输网、运输危险源、影响区域3方面提出了危险品道路运输风险分析的框架.将道路固有特征、气象条件、交通状况和人口密度分布等风险减缓或扩大因素划分为8类,重点讨论了主要路线的自变量和因变量因素.采用双层选线管理模式,深入分析了最小化运输事故概率和暴露人口风险模型.应用权数调整节点标号算法和边线标号算法解决危险品道路运输选线问题.对影响区暴露人口的选取做了深入探讨,考虑了邻接交迭路段暴露人数的误差,对准确计算危险品运输风险有重要价值. 相似文献
997.
Low-permeability, non-reactive barrier walls are often used to contain contaminants in an aquifer. Rates of solute transport through such barriers are typically many orders of magnitude slower than rates through the aquifer. Nevertheless, the success of remedial actions may be sensitive to these low rates of transport. Two numerical simulation methods for representing low-permeability barriers in a finite-difference groundwater-flow and transport model were tested. In the first method, the hydraulic properties of the barrier were represented directly on grid cells and in the second method, the intercell hydraulic-conductance values were adjusted to approximate the reduction in horizontal flow, allowing use of a coarser and computationally efficient grid. The alternative methods were tested and evaluated on the basis of hypothetical test problems and a field case involving tetrachloroethylene (PCE) contamination at a Superfund site in New Hampshire. For all cases, advective transport across the barrier was negligible, but preexisting numerical approaches to calculate dispersion yielded dispersive fluxes that were greater than expected. A transport model (MODFLOW-GWT) was modified to (1) allow different dispersive and diffusive properties to be assigned to the barrier than the adjacent aquifer and (2) more accurately calculate dispersion from concentration gradients and solute fluxes near barriers. The new approach yields reasonable and accurate concentrations for the test cases. 相似文献
998.
999.
Mendoza G Gutierrez L Pozo-Gallardo K Fuentes-Rios D Montory M Urrutia R Barra R 《Environmental science and pollution research international》2006,13(1):67-74
- DOI: http://dx.doi.org/10.1065/espr2006.01.011
Goal, Scope and Background Chile signed the Stockholm Convention, which establishes measures to reduce or eliminate Persistent Organic Pollutants (POPs)
release into the environment, including the prohibition of their use and reduction of secondary products release, as well
as management related with waste treatment. Among POPs, PCBs are a family of 209 compounds that differ in chlorine level and
position. These substances present a wide variability in their physicochemical properties such as vapor pressure, water solubility
and partition coefficients that determine their behavior and mobility within the different environmental compartments. In
Chile, as in other countries, the use of these compounds were and continue to occur in diverse industrial applications such
as dielectric fluid in transformers and condensers, with a use in Chile of approximately 550,000 L. A sampling of bivalves
was performed during the years 2000-2002 in order to obtain information on the spatial distribution of the PCB levels for
the length of the long Chilean coast (180–540 South latitude, 4,200 km), contributing in this way to a better understanding
of the PCB trend and eventual fractionation along latitudinal gradients in Chile, using as the bivalve Perumytilus purpuratus
('Chorito Maico') bioindicator.
Methods The marine bivalves Perumytilus purpuratus were collected in 16 localities in northern and southern Chile. All samples were
lyophilized, and PCBs (51 congeners) were extracted in a Soxhlet system (24 h) with n-hexane. Samples were cleaned in florisil
and analyzed by GC-ECD. Blanks, certified reference materials and standards were processed along with the samples.
Results and Discussion The results obtained for P. purpuratus indicate a congeneric distribution profile associated to a latitudinal gradient, and
the statistical analysis of the congeneric composition of the PCBs indicated five groups in relation to the molecular weight
(number of chlorines), where the lighter congeners were observed in areas corresponding to high latitudes with total PCB values
of 298 ng/g dry weight.
Conclusion P. purpuratus turns out to be a good bioindicator of PCB levels in the coastal areas of Chile due to its wide distribution.
The highest concentrations and the more volatile congeners were found in southern Chile, which could be the result of processes
of long-range transport or illegal discharge occurring in such remote areas. These results confirm previous data from the
International Mussel Watch project ten years ago.
Recommendation and Outlook Future studies are needed to confirm our findings utilizing another environmental matrix such as soil/sediments and air samples. 相似文献
1000.
Congling ShiMaohua Zhong Xingzhong NongLi He Jiehong ShiGuoguan Feng 《Safety Science》2012,50(5):1319-1332
The construction of metro in China is in a period of an unprecedented development in recent years, and the passengers are in high density within the metro during the operation time, the problem of occupant safety in emergencies has attracted more and more attentions. During the design and operation stages, modeling of the metro station evacuation capacity by using the computational models is an effective measure for guaranteeing the metro evacuation safety in the future. In this article, the safety strategy of evacuation in metro stations is first investigated and established, which involves the occupants needed to be evacuated, the evacuation route, and the safety zone. Then, an engineering calculation method for the metro station evacuation time is proposed. Based on the experimental data, simulation of evacuation process in different fire cases is conducted by using an agent-based model, so as to study the features of occupant evacuation behavior, the evacuation time, the passage flow rate, and the strategy of using the escalator as evacuation passage. These conclusions will be helpful for guiding the safe evacuation design of metros in China. 相似文献