Spatial trends and impairment assessment of mercury in sport fish in the Sacramento–San Joaquin Delta watershed

A three-year study was conducted to examine mercury in sport fish from the Sacramento–San Joaquin Delta. More than 4000 fish from 31 species were collected and analyzed for total mercury in individual muscle filets. Largemouth bass and striped bass were the most contaminated, averaging 0.40 μg/g, while redear sunfish, bluegill and rainbow trout exhibited the lowest (<0.15 μg/g) concentrations. Spatial variation in mercury was evaluated with an analysis of covariance model, which accounted for variability due to fish size and regional hydrology. Significant regional differences in mercury were apparent in size-standardized largemouth bass, with concentrations on the Cosumnes and Mokelumne rivers significantly higher than the central and western Delta. Significant prey–predator mercury correlations were also apparent, which may explain a significant proportion of the spatial variation in the watershed.     

Molecular characterization of copper in soils using X-ray absorption spectroscopy

Bioavailability of Cu in the soil is a function of its speciation. In this paper we investigated Cu speciation in six soils using X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and synchrotron-based micro X-ray fluorescence (μ-XRF). The XANES and EXAFS spectra in all of the soils were the same. μ-XRF results indicated that the majority of the Cu particles in the soils were not associated with calcium carbonates, Fe oxides, or Cu sulfates. Principal component analysis and target transform of the XANES and EXAFS spectra suggested that Cu adsorbed on humic acid (HA) was an acceptable match. Thus it appears that Cu in all of the soils is primarily associated with soil organic matter (SOM). Theoretical fitting of the molecular structure in the soil EXAFS spectra revealed that the Cu in the soils existed as Cu atoms bound in a bidentate complex to O or N functional groups.     

Can pine needles indicate trends in the air pollution levels at remote sites?

Data from ten years of integrated monitoring were used here to evaluate whether pine needles are a feasible tool for an assessment of long-term trends of the atmospheric contamination. Pine needles collected once a year were compared to high volume air samples collected for 24 h, every 7 days, and passive air samples integrated over 28-day periods. Results showed the same concentration patterns of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) captured in needles and high volume samples. Passive air samplers were less efficient in sampling the particle-bound compounds. Theoretical air volume equivalent to each needle sample (V_EQ) was calculated as a ratio of the needle concentration over the mean air concentration. Results indicated different equivalent volumes for PAHs and organochlorines, possibly due to the faster degradation rates of PAHs in needles. The most important finding is that in the long term a needle monitoring gives very similar information on temporal trends of the atmospheric pollution as does a high volume air monitoring.     

长江（万州段）水体溶解性有机物的荧光光谱分析

按照河床形态、水文条件、排污口分布、支流状况等特点从长江万州段及长江支流苎溪河选取8个断面进行采样,对水样中溶解性有机物（DOM）的荧光光谱特征进行了分析和研究。利用日立F 4500荧光分光光度计对长江水、普通自来水和纯水在紫外光激励下产生的荧光光谱及其特性进行了比较研究。同时,研究了不同水样、不同取样点的水体DOM的荧光特性和三维荧光光谱图。结果表明：长江水在波长290 nm左右的紫外光激励下能产生较强的荧光。荧光峰是350~550 nm 范围的宽谱峰,荧光峰值波长在450 nm左右。但是不同取样点水样的荧光峰强度明显有差异,在4号、5号、2号取样点的水样荧光强度明显高于其他取样点,这与采样点附近污染源排放有明显的关系。该研究方法可作为鉴别水质污染的一种有效的手段.     

城市景观生态网络规划的空间模式应用探讨

城市景观生态网络空间模式研究是生态城市和景观规划设计现今研究的重要领域之一,目的在于依据景观生态网络模式的应用建立起生态城市规划建设的基本框架和技术途径。在探讨城市景观生态系统特征和城市景观生态网络结构的基础上,总结景观生态网络空间模式并重点分析了水景树的空间生态模式、森林 道路 住宅复合网络模式、平原城市农田 灌木丛 河流交叉网络模式、岛屿城市的绿地 道路生态网络模式4种城市景观生态网络典型模式的图示特征及其生态意义。依此为理论指导基础,以都江堰为例,在继承都江堰大地景观格局并结合都江堰市灾后重建需求的前提下,研究都江堰市城市景观生态格局和生态过程,探讨在不同尺度和不同维度上运用4种网络图示进行都江堰城市景观生态网络优化调整的空间模式和对策。(1)依据“水景树图式”优化调整纵向维度景观生态格局;(2)依据“森林 道路 住宅”和“农田 灌木丛 河流”网络调整横向维度景观生态格局;(3)依据岛屿城市的“绿地 道路”景观生态网络调整城市组团景观生态格局.     

Fractionation of Cd,Cr, Pb and Ni in roadside soils of Uyo,Niger Delta Region: Nigeria using the optimized BCR sequential extraction technique

The optimized BCR sequential extraction procedure was applied to nine roadside soil samples for the determination of Cd, Cr, Pb and Ni. The extractable metals were isolated into three operationally defined fractions viz: acid extractable, reducible and oxidizable. The residue was treated with aqua regia solution. Metal analysis was done using flame atomic absorption spectrophotometry with air–acetylene flame. Results obtained showed the concentrations of the metals as relative abundance in the mobile phases of the samples (based on the sum of the first three fractions) are in the following order: Cd(91.9) > Pb(82.8) > Ni(49.5) > Cr(39.0). The most non-mobilizable metals were Cr and Ni which are generally lithogenic, associated with the silicate matrix, and the order is as follows: Cr(61.0) > Ni(50.5) > Pb(17.2) > Cd(8.1). The recovery of all the metals expressed as the ratio of total metal concentration to fractional sum of the optimized BCR sequential extraction procedure was of the order: Cr(95.6) > Pb(95.0) > Ni(94.8) > Cd(92.4).     

线路交换开关级联失效的评估

本文主要针对信号线路交换网络设计中的失效问题展开讨论,对输出信号在传输网络中失效性进行了评估,根据失效评估在设备可靠性设计方面做了相应的考虑。     

Trophic structure of ecosystems and ecotoxicology of soil organisms

Studies on the ecotoxicology of soil organisms have led to the revision of views on the trophic structure of ecosystems. It was found that the microbial link is obligatory and controls the migration of toxicants and their effects in the food chain. Differences in effects are accounted for by both the physiological stability of organisms and their affliation with relatively independent and biogeochemically closed ecosystems differing in their spatiotemporal scales. The latter form a hierarchical three-level structure: ecosystems of unicellular organisms—ecosystems of small multicellular organisms—the ecosystem of large multicellular organisms, or of biogeocenosis. Trophic networks within the structure are united by ecosystemophagy as the type of feeding of large multicellular organisms, and this accounts for the importance of the latter as indicators of long-term changes in a biogeocenosis.     

基于神经网络模型的房屋震害易损性估计方法

结构易损性分析是震害预测工作中的一个重要环节.本文提出了一种基于人工神经网络模型的房屋震害易损性估计方法,文中以多层砖房结构的建筑为例,给出了易损性估计神经网络模型的输入向量设计方案和具有输出约束控制的BP神经网络模型.     

生命线系统的震害耦联

在震害分析时,弧立地评价一个生命线系统的功能,不考虑与其它生命线系统间的耦联关系,可能会低估地震造成的损失。将地理信息系统（ＧＩＳ）与现有的震害预测方法结合起来,有利于推动新方法的研究。本文在ＧＩＳ环境下定义了网络失效率,提出了一种考虑不同生命线系统之间耦联关系的震害分析方法,给出了一个算例,并建议了相应的生产能力相关的震后应急抢修决策方案。