单层带支撑异形柱框架的高温性能研究

针对单层异形柱框架,通过高温数值分析,考察了支撑设置和受火位置对结构高温变形及内力的影响。研究结果表明:对于单层多跨异形柱框架,当只有一端有支撑跨时,会在一定程度上增大另一端的边节点水平位移和边柱侧向变形,对结构整体抗火不利;当左、右两端均有支撑跨时,非支撑跨在火灾作用下的梁轴力比很大,升温后期可能因梁跨中竖向位移急剧增大而发生破坏。基于上述研究结果,给出了4类单层带支撑异形柱框架火灾行为的初步判定方法。     

长江口滨岸带生态环境质量评价指标体系与评价模型

基于生态系统理论,构建了由社会、经济、自然环境、自然灾害4个子系统和7个二级指标及29个三级指标组成的长江口滨岸带生态环境质量评价指标体系;以信息熵理论为基础建立了客观确定指标权重的综合信息熵模型法,并以层次分析法和综合信息熵模型法相结合确定评价指标权重值;采用灰色关联综合评价模型对上海滨岸带生态环境质量进行评价。对上海滨岸带宝山、浦东、南汇、奉贤、金山和崇明岸段1999~2003年5年间生态环境质量的时空变化特征和分级规律的研究表明：宝山滨岸带生态环境质量1999~2000年为较差,2001~2003年为中等;浦东、奉贤、南汇和金山生态环境质量一直处于中等水平;崇明生态环境质量1999、2000年为良,而2001~2003年为中。     

天津滨海新区环境状况分析及对策建议

天津市滨海新区包括塘沽、汉沽、大港、开发区、保税区、是近年天津最大的经济增长点,是全市经济发展的新龙头。本文依据近年环境的监测结果,分析了滨海新区的环境现状和主要环境问题,在此基础上提出了实现了新区社会、经济发展与环境,资源保护相协调,走可持续发展之路的对策建议。     

氧化聚合型包覆技术（OTC）在热带海洋大气环境螺栓中的应用

目的 研究氧化聚合型技术(OTC)在热带海洋大气环境中对高强螺栓的防护效果。方法 在三亚大气腐蚀试验站开展OTC包覆和未保护的高强螺栓6 a的大气曝晒试验,通过扫描电镜(SEM)、X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)和激光共聚焦显微镜(LSCM)开展腐蚀形貌和成分分析,通过质量损失试验考察OTC包覆和未保护的高强螺栓的腐蚀行为。结果 未经保护的螺栓表面生成大量棕红色的腐蚀产物,XRD分析表明,其主要成分为α-Fe OOH、β-Fe OOH、γ-Fe OOH、Fe3O4和Fe₂O₃等,其中β-Fe OOH晶体结构中含有Cl–,会加速基体腐蚀。经LSCM分析,螺栓垫片整体呈全面腐蚀状态,但同时发生局部腐蚀,最深的点蚀坑达120μm以上。经OTC技术保护的高强螺栓,仅在底部出现少量棕色物质,大部分仍呈现原有的黑色基体表面,OTC包覆螺栓6 a的腐蚀速率约为未保护螺栓的腐蚀速率1/15,OTC包覆垫片表面未出现明显腐蚀。结论 氧化聚合型包覆技术显著降低了高强螺栓的腐蚀速率,具有优良的耐腐蚀性能,在热带海洋大气环境对高强螺栓起到良好的长...     

辽东湾沿岸贝类和环境中的粪大肠菌和细菌总数

对辽东湾沿岸海域几种主要经济贝类体内及其生存环境中的粪大肠菌群和细菌总数进行了调查与研究。结果表明,贝类中粪大肠菌群超标率为53.8%;表层海水中超标率为46.2%;表层沉积物中超标率为12.5%。各种样品中细菌总数的检出结果也表明,该沿岸海域环境和贝类受到了一定的有机污染影响。     

养鸡场空气微生物污染及工人呼吸暴露风险

动物养殖场是空气环境微生物污染的重要来源,然而目前关于养殖场空气中微生物污染特征的时间规律少有报道.针对以上情况,以蛋鸡场为例,采用16S rRNA基因扩增子测序分别对养殖场空气和粪便环境中细菌分布特点及呼吸暴露展开为期80余周的研究.结果表明,空气和粪便样本中16S rRNA含量范围分别在6.08×10⁵ ~4.90×10⁶ copies·m^-3和4.27×10⁸ ~1.15×10¹⁰ copies·g^-1之间.空气中细菌浓度的平均值在冬季显著高于夏季,而生物多样性则呈现相反趋势.蛋鸡场空气与粪便中的优势细菌门均为厚壁菌门（Firmicutes）.在所调查时间内,空气中前3个优势菌属的种类较为稳定,依次为乳杆菌属（Lactobacillus）、拟杆菌属（Bacteroides）和栖粪杆菌属（Faecalibacterium）,而粪便中优势菌属则随养殖时间的增加波动较大.空气和动物粪便中细菌和致病菌群落结构的相关性均不显著,但不同介质中两种目标微生物的含量均显著相关.粪便中细菌的气溶胶化指数随养殖时间的增加而呈上升趋势,而致病菌趋势相反.其中,瘤胃菌科torques属（[Ruminococcus]_torques_group）、拟杆菌属（Bacteroides）和栖粪杆菌属（Faecalibacterium）为最易发生气溶胶化的前3个致病菌属.养鸡场工人的细菌呼吸暴露具有季节性差异,其中细菌和致病菌摄入量的平均值分别为2.54×10⁷ copies·d^-1和2.87×10⁵ copies·d^-1.研究结果将为系统评估养殖场空气微生物的污染特征和潜在健康风险,对以及制定相应的职业暴露行业标准和防控措施提供科学依据.     

木麻黄沿海防护林土壤呼吸动态及其关键影响因子

以中国亚热带木麻黄沿海防护林为研究对象,利用LI-8100土壤呼吸自动观测系统,对木麻黄人工林生态系统的土壤呼吸特征进行了监测.结果表明,不同林龄木麻黄林地土壤呼吸日动态均呈双峰变化曲线,8:00~10:00和14:00~16:00出现峰值,最小值出现在20:00~22:00;季节动态均呈单峰曲线,最大值出现在6~7月份,最小值则出现在12~1月份.土壤温度和水分对土壤呼吸的季节变化存在显著影响,并有明显的交互作用,进行单因素方差分析发现,土壤呼吸季节变化与5cm土温存在着较好的指数相关关系(P成林>幼林;随着林龄的增大,土壤呼吸对土壤温度和土壤水分的敏感性增强.     

Soil lead (Pb) in residential transects through Lubbock,Texas: a preliminary assessment

Residential lead (Pb) contamination, resulting from decades-long use of leaded gasoline and lead-based paint, is likely to be present in soils in most urban areas. A screening level sampling effort demonstrated that Lubbock, Texas, USA, like other cities of its age and size, has areas of elevated soil Pb. This effort was based on soil sampling performed on residential, commercial and thoroughfare properties. The focus of this study was to investigate that component of soil contamination due to combustion of leaded gasoline. Soils were collected from the 1–2 cm surface layer from street-side property borders, well away from buildings that might lead to soil contamination from leaded paint chips. All samples were analyzed for Pb after a 1 M HNO₃ mild extraction to determine the amount of bioavailable Pb. Two of three transects through the city demonstrated significant trends of decreasing Pb concentrations with distance from the city center, paralleling a decrease in developed property age. Peak soil Pb concentrations outside city development was 4.9 ± 0.6 mg/kg while the median concentration for the city was 35.4 mg/kg. Peak soil Pb concentrations in the city center ranged from 90.0 to 174.0 mg/kg and decreased exponentially to 6.0–9.0 mg/kg at the furthest terminus of the residential transects.     

Factors affecting the quantitative uncertainty of the estimated short-term intake. Part II—Practical examples

ABSTRACT

The effects of the spread of residue concentrations in the samples derived from the selected supervised trials and the number of trials were studied on the magnitude and uncertainty of the short-term dietary intakes calculated with the proposed new procedure (IESTI_p) and that one used currently by the FAO (Food and Agriculture Organization) and WHO (World Health Organization) Joint meeting on Pesticide Residues (JMPR) (IESTI_c). The residue data of 10 pesticides were obtained from supervised trials conducted on apples and pears. The methods described in Part I were used for the calculations of the uncertainty. The results indicate that the ratio of IESTI_P to IESTI_c (φ_IESTI) is directly proportional to the ratio of the estimated maximum residue level (MRL), recommended by the JMPR; to the highest residue (HR) observed in supervised trials, and it may have a wide range depending on the particular conditions. The φ_IESTI becomes greater with the increase of the difference between the mrl or maximum residue limit (MRL, established by the Codex Alimentarius Commission, CAC) and HR, and becomes smaller if the difference between the large portion (LP) and unit mass (U) decreases. The φ_IESTI ranged between 2 and 5.1 in the 16 cases examined indicating that the IESTI_p calculation method leads to higher intake estimates. The ratio of CV_IESTIp and CV_IESTIc ranged typically between 0.62 and 1.71. It rapidly increased up to 12 trials. For a larger number of trials, the ratio remained practically constant (1.69–1.71). The processing factor (PF) equally affects the MRL and HR values, therefore, it will not practically influence the φ_IESTI. The uncertainty of the estimated median residues depends on the spread and number of values in the residue datasets, which affects the uncertainty of the conversion factor (CF) and subsequently the uncertainty of the estimated IESTI_p. Residue values obtained from minimum nine independent trials are required for the correct calculation of the 95% confidence intervals of the calculated median residues. The uncertainty of the analytical results directly affects the median, HR values and indirectly the calculated mrl and the MRL derived from it. Therefore, it should also be considered for the calculation of the combined uncertainty of the conversion factors. For the correct interpretation of the results of dietary exposure calculations, the upper 95% confidence limit of the short-term intake should also be considered. However, it is not the current practice of regulatory agencies or JMPR.