湖泊富营养化评价的S型曲线通用表示式

在适当设定富营养化指标的“本底”值情况下 ,当指标值用对应于“本底”值的相对值表示时 ,可采用 S型曲线描述湖泊富营养化发展程度 ,从而公式中的参数可视为与指标特性无关 ,采用遗传算法对公式中的参数优化 ,得到对多项指标通用的富营养化程度的指数计算公式 ,并用广义对比因子赋权新方法计算富营养化综合指数。该评价方法物理意义明确 ,计算简单 ,使用方便 ,具有可比性和通用性     

煤矿巷道中低浓度甲烷微生物降解效能实验研究

为了研究煤矿低浓度甲烷微生物降解效能,富集、纯化分离并初步鉴定出可以甲烷作为唯一碳源的高效降解甲烷的好氧型微生物。生理生化实验表明,该菌符合甲烷氧化菌的典型特征。自主设计了模拟巷道中低浓度甲烷微生物降解实验分析系统。实验结果表明,在风速为0.5~1.0 m/s,甲烷体积分数为1%~5%范围内,随着甲烷体积分数的增加,甲烷的降解效果越明显,然而风速越大越不利于甲烷的降解,经过50 min的降解,甲烷体积分数由最高的5%最低降至1.43%;二氧化碳体积分数可由初始的0.031%最大升高到0.075%。实验还发现消耗的甲烷和生成的二氧化碳并非符合1∶1的比例。     

敞开式TBM施工隧道粉尘扩散及除尘系统研究

TBM掘进过程中产生大量粉尘，为了掌握粉尘的分布规律并优化除尘系统，以敞开式TBM为例，采用数值计算方法研究不同除尘风管位置，不同除尘风速和不同掘进面产尘量下的洞内粉尘浓度分布规律。研究结果表明:敞开式TBM隧道施工过程中，掘进面至除尘风管区域质量粉尘浓度较高，在除尘风管口后方区域下降到 2 mg/m3以下；除尘风管布置在距掘进面30 m位置处时，洞内沿程粉尘含量相对较大，除尘风管布置在距掘进面20 m位置处时洞内沿程及TBM支护区域粉尘含量相对较小；排风风速为15 m/s时，敞开式TBM支护区域粉尘质量浓度最小，排风风速为30 m/s时，该区域粉尘质量浓度最大；掘进面产尘量越大，洞内沿程及敞开式TBM支护区域粉尘质量浓度越大，不同产尘量下洞内粉尘浓度均在除尘风管后方达到规范限值以下。     

空气幕对抑制收费亭内污染物侵入作用的数值模拟

针对高速公路收费亭内空气质量差、污染严重的问题,为改善收费亭内工作环境、保障作业人员的身体健康,采用空气幕隔断方式抑制污染物进入亭内.运用Airpak软件对空气幕不同送风速度和送风角度下的抑制效果进行数值模拟,计算结果表明:空气幕可以有效抑制污染物侵入收费亭内;竖直向下送风时,随着送风速度的增加,抑制效果有所增加,当送...     

浅谈V型滤池的工艺设计

介绍了V型滤池工艺特点,总结了V型滤池的工艺设计、施工安装和生产管理工作体会.     

Radiological monitoring: terrestrial natural radionuclides in Kinta District,Perak, Malaysia

Natural background gamma radiation and radioactivity concentrations were investigated from 2003 to 2005 in Kinta District, Perak, Malaysia. Sample locations were distant from any ‘amang’ processing plants. The external gamma dose rates ranged from 39 to 1039 nGy h⁻¹. The mean external gamma dose rate was 222 ± 191 nGy h⁻¹. Small areas of relatively enhanced activity were located having external gamma dose rates of up to 1039 ± 104 nGy h⁻¹. The activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K were analyzed by using a high-resolution co-axial HPGe detector system. The activity concentration ranges were 12–426 Bq kg⁻¹ for ²³⁸U, 19–1377 Bq kg⁻¹ for ²³²Th and <19–2204 Bq kg⁻¹ for ⁴⁰ K. Based on the radioactivity levels determined, the gamma-absorbed dose rates in air at 1 m above the ground were calculated. The calculated dose rates and measured dose rates had a good correlation coefficient, R of 0.94. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the gamma-absorbed dose rate and the mean population weighted dose rate were calculated. An isodose map for the Kinta District was also produced.     

Variation in indoor levels of polycyclic aromatic hydrocarbons from burning various biomass types in the traditional grass-roofed households in Western Kenya

Biomass burning as fuel in the traditional grass-roofed rural households of Western Province of Kenya in open fire places, in poorly ventilated conditions, lead to accumulation of soot under the roofs. This study characterized and quantified the polycyclic aromatic hydrocarbons (PAHs) in accumulated soot in these households and determined the variation in PAHs concentrations with fuel biomass type. Soot samples collected from the households were extracted, cleaned and analysed by gas chromatography. The PAHs were identified using retention times, verified by gas chromatographic mass spectral analysis and quantified from peak area responses using the internal standard method. The PAHs levels significantly varied (P ≤ 0.05) with biomass type in the order: dung ≥ indigenous trees ≥ exotic trees ≥ shrubs and crop residues. Use of dung and wood from indigenous trees as fuel should be discouraged since they are higher emitters (P ≤ 0.05) of carcinogenic PAHs.     

Changes in cell-type composition in digestive gland of slugs and its influence in biomarkers following transplantation between a relatively unpolluted and a chronically metal-polluted site

Changes in cell-type composition (CCTC) is a general phenomenon that takes place in the digestive gland epithelium of stressed molluscs. The aim of the present work was to determine whether CCTC is a reversible process in the digestive gland of sentinel slugs chronically exposed to metal pollution and how CCTC affects metal accumulation parameters and different cell and tissue biomarkers of exposure and effect. Slugs (Arion ater) from an abandoned zinc mine were transferred to a relatively unpolluted site and the other way around for 3, 10 and 28 d. The volume density of black silver deposits (Vv_BSD) after autometallography, and metallothionein (MT) levels were used as biomarkers of exposure to metals and CCTC and lysosomal responses were selected as effect biomarkers. Results indicated that slugs were sensitive to recent metal pollution; however, slugs chronically exposed to metals presented some characteristic features and were less responsive to pollution cessation without signs of CCTC reversal.     

Assessment of Changes in Stream and Riparian Conditions of the Marys River Basin,Nevada1

Abstract: Stream and riparian managers must effectively allocate limited financial and personnel resources to monitor and manage riparian ecosystems. They need to use management strategies and monitoring methods that are compatible with their objectives and the response potential of each stream reach. Our objective is to help others set realistic management objectives by comparing results from different methods used to document riparian recovery across a diversity of stream types. The Bureau of Land Management Elko Field Office, Nevada, used stream survey, riparian proper functioning condition (PFC) assessment, repeat photographic analysis, and stream and ecological classification to study 10 streams within the Marys River watershed of northeast Nevada during all or parts of 20 years. Most riparian areas improved significantly from 1979 to 1992‐1993 and then additionally by 1997‐2000. Improvements were observed in riparian and habitat condition indices, bank cover, and stability, pool quality, bank angle, and depth of undercut bank. Interpretation of repeat photography generally confirmed results from stream survey and should be part of long‐term riparian monitoring. More attributes of Rosgen stream types C and E improved than of types B and F. A and Gc streams did not show significant improvement. Alluvial draws and alluvial valleys improved in more ways than V‐erosional canyons and especially V‐depositional canyons. Stream survey data could not be substituted for riparian PFC assessment. Riparian PFC assessments help interpret other data.