基于三角模糊数的清河沉积物重金属评价

为全面了解北京清河沉积物重金属的空间分布及污染水平,在清河采集8个沉积物样品,测定w(As)、w(Cd)、w(Cr)、w(Cu)、w(Pb)、w(Zn),并利用基于三角模糊数的地累积指数模糊评价模型对北京清河沉积物的重金属污染进行评价. 结果表明:北京清河沉积物中w(As)、w(Cd)、w(Cr)、w(Cu)、w(Pb)、w(Zn)的平均值分别为43.18、1.20、70.70、49.62、38.59和297.36 mg/kg,不同重金属在各采样点间的分布差异较大,6种重金属的污染程度表现为As>Cd>Zn>Cu>Pb>Cr. 对于大部分采样点,基于三角模糊数的不确定性评价结果与常规评价结果保持一致,均显示清河沉积物重金属污染程度较低. 然而,QH6采样点(立水桥)As常规评价结果为偏中度污染,不确定性评价结果为中度污染;QH5采样点(清河大桥)Cd和Zn在常规评价结果为轻度污染,而不确定性评价结果为偏中度污染;QH8采样点(入温榆河口)Cd和Zn常规评价结果分别为轻度污染和偏中度污染,不确定性评价的结果则显示为偏中度和中度污染. 不确定性评价方法采用重金属质量分数区间值,而常规评价则采用重金属质量分数的单一值;不确定性评价通过计算隶属度确定污染等级,在接近分级界限时,不确定性评价和常规评价结果之间出现差异.      

Origins and scales of hypoxia on the Louisiana shelf: Importance of seasonal plankton dynamics and river nutrients and discharge

Management plans for the Mississippi River Basin call for reductions in nutrient concentrations up to 40% or more to reduce hypoxia in the Gulf of Mexico (GOM), while at the same time the government is considering new farm subsidies to promote development of biofuels from corn. Thus there are possibilities of both increasing and decreasing river nutrients depending on national priorities. River flow rates which also influence the extent of hypoxia on the shelf may be altered by global climate change. We have therefore developed a series of simulations to forecast ecosystem response to alterations in nutrient loading and river flow. We simulate ecosystem response and hypoxia events using a linked model consisting of multiple phytoplankton groups competing for nitrogen, phosphorus and light, zooplankton grazing that is influenced by prey edibility and stoichiometry, sub-pycnocline water-column metabolism that is influenced by sinking fecal pellets and algal cells, and multi-element sediment diagenesis. This model formulation depicts four areas of increasing salinity moving westward away from the Mississippi River point of discharge, where the surface mixed layer, four bottom layers and underlying sediments are represented in each area. The model supports the contention that a 40% decrease in river nutrient will substantially reduce the duration and areal extent of hypoxia on the shelf. But it also suggests that in low and middle salinity areas the hypoxia response is saturated with respect to nutrients, and that in high salinity regions small increases in nutrient and river flow will have disproportionally large effects on GOM hypoxia. The model simulations also suggest that river discharge is a stronger factor influencing hypoxia than river nutrients in the Mississippi River plume. Finally, the model simulations suggest that primary production in the low salinity regions is light limited while primary production in the higher salinity zones is phosphate limited during the May to October period when hypoxia is prevalent in the Mississippi River plume.     

Modeling the refuge effect of submerged macrophytes in ecological dynamics of shallow lakes: A new model of fish functional response

Submerged macrophytes often provide refuge for zooplankton from fish predation in temperate and subtropical shallow lakes. However, since the relationship between submerged macrophyte abundance and its refuge effect has not been well established, the refuge effect is difficult to be simulated. In this paper, we constructed mathematical models to describe the refuge effect of submerged macrophytes on fish foraging activities and ecological dynamics of shallow lakes based on the previous studies. We clarified the underlying behavioral mechanisms of the observed functional responses through analyses of the fish foraging behavior, extracted the affected variables related to the refuge effect, formulized the relationship between the affected variables and submerged vegetation density, and determined parameter values with a compensative procedure. Calibration and validation results indicated that the new functional response model was successful to simulate the refuge effect on interfering with fish foraging behavior. Moreover, the model was cooperated into a minimal ecological model for shallow lakes. Modeling results showed that the model was able to simulate the refuge effect in ecological dynamics, and made the ecological model produce significantly different results from those with the existing functional response models.     

环境自动监测站固定式辐射监测仪性能测试与评价

参考计量技术规范《固定式环境γ辐射空气比释动能(率)仪现场校准规范》(JJF 1733—2018),对辐射环境空气自动监测站78台高气压电离室开展辐射特性测试。现场校准方面,仅88%的电离室满足1±0.2的响应范围要求;78台电离室的重复性均不超过1%,响应的非线性均不超过6.5%,符合规范要求。针对电离室开展辐射性能测试,发现电离室在9.0×10^-2~1.0×10⁹ μGy/h范围内的响应均不超过1±0.2;电离室对164 keV以上的光子的能量响应趋于1.0,对60 keV以下的光子无响应能力,而当光子能量在60~164 keV范围内时,响应曲线会因γ光子与电离室内部惰性气体的光电效应出现"鼓包";电离室不具备对核临界事故脉冲辐射的监测与警示能力;电离室能够在2 s内给出测量范围内的准确示值,但在分段电压的交界处,响应时间会延长至180~360 s;电离室的响应受环境温度、湿度变化的影响大小不足±0.01,表明电离室的环境适应性优良。     

BOD快速测定方法研究进展

综述BOD快速测定方法,快速测定方法包括高温法、相关系数法和生物传感器法。重点论述生物传感器法,讨论生物传感器的工作原理、微生物膜所使用的微生物、传感器的响应方式、影响生物传感器法的因素、该法测试样品所需的时间以及生物传感器法所存在的问题。最后对BOD快速测定方法进行了展望。     

基于模糊TOPSIS的道路危险货物运输企业安全评价方法

为了评估道路危险货物运输企业安全性水平,降低危险货物运输风险概率,围绕道路危险货物运输企业安全性评价的重要性,提出一种适用于模糊不确定环境的道路危险货物运输企业安全性评价方法。首先,从人-机-组织综合角度建立道路危险货物运输企业安全性评价指标体系;其次,组合运用模糊决策理论、群体决策和TOPSIS方法提出道路危险货物运输企业安全性评价方法框架;最后以南京市5家道路危险货物运输企业的安全性评价为例进行方法验证。     

石油工程技术服务企业海外项目风险评价研究

石油工程技术服务企业海外项目是企业寻求自身发展,保持和提高经济效益的重要组成。综合采用专家咨询法和因果分析图方法识别出石油工程技术服务企业海外项目存在的市场风险、经济风险、政治风险、技术风险、自然风险、管理风险等6种风险。构建包含上述6个准则21个指标的风险评价指标体系,应用层次分析(AHP)法确定指标权重,应用模糊综合评价方法构建石油工程技术服务企业海外项目风险评价模型。运用构建的指标体系与评价模型对某石油钻探公司格鲁吉亚共和国第12区块风险进行评价实证。     

消防第一出动时间的频次分布规律研究

消防队接到火警后第一出动力量及时到达火场展开灭火救援,对有效控制火灾、减少人员伤亡和财产损失有着重要的意义。第一出动时间直接反映了城市灭火救援专业力量的出动响应水平。采用SPSS软件对1995-2003年日本全国城市火灾数据进行分析,发现第一出动时间的频次符合对数正态分布;与部分中国城市火灾统计数据对比后,表明后者符合同样的规律。中国数据对数正态分布的期望值为4.9分钟,其物理意义为消防力量第一出动时间的平均值,与我国消防条例对城镇消防站设置的基本原则相符。     

岩溶山区不同土地利用方式下土壤质量指标响应

探讨了岩溶山区不同土地利用方式与土壤质量指标之间的响应关系.对重庆市北碚岩溶山区土壤肥力指标进行主因子分析的结果表明,原有22个土壤质量指标可归为4 类,分别以有机质,有效含水量,通气孔隙度,细菌、真菌数量百分比为代表,这4类因子基本反映了土壤质量随土地利用变化的综合变化状况.通径分析表明,不同土地利用方式下土壤持水性能主要与有机质、＞0.25 mm水稳性团聚体有关,二者的效应均大于黏粒.在土地利用方式变化过程中,土壤质量变化体现在有机质含量、土壤供持水能力、土壤结构状况和土壤微生物特性的变化上.     

爆炸荷载作用下砌体结构响应的有限元分析

对墙体模型进行简化,用单个混凝土砖块宽度的墙来代替所要分析的整面墙,并采用有限元分析软件LS-DYNA对砌体墙的破坏模式进行数值模拟分析。LS-DYNA的数值模拟结果显示,混凝土砌体墙在不同爆炸荷载作用下会发生不同程度的破坏,破坏的产生首先从墙体中部开始;随着爆炸荷载峰值的提高,砌体墙的破坏逐渐由中间向两端发展,当爆炸荷载峰值压力达到0.36 MPa及以上时,墙体会发生破坏,有块体飞出,并在重力作用下发生倒塌。数值模拟的结果与文献提供的试验结果比较吻合。