Fractionation of Hydrophobic Organic Materials in Surface Microlayers

Organic microlayers occur naturally on the surfaces of most bodies of water. Hydrophobic organic materials such as longchain acids and hydrocarbons are constituents of these surface films and may be essential for their formation. Studies of these microlayer components have been primarily of marine locations, although several reports describing freshwater locations exist. Results of these studies are generally consistent with those of Lake Michigan surface films. Fractionation of fatty acids and alkanes according to differential solubility occurs to some extent but is complicated by other processes. Partitioning between dissolved and particulate phases appears to modify both input and removal effects, and purely physical phenomena such as sinking processes and turbulent mixing are also quite important. Evidence of aquatic, terrigenous, and eolian sources is preserved in microlayer components. Their relative contributions vary considerably but provide more information about surface/subsurface fractionation.     

Models of Particle Dry Deposition to a Lake Surface and Some Effects of Surface Microlayers

A review of the theoretical and empirical information that has been used in modeling dry deposition over water reveals uncertainty up to the order of magnitude level for particles in the important 0.5 to 5 μm range of diameter. Much of this is attributable to uncertainty in identifying the mechanisms controlling this transport. The results do indicate that dry deposition velocities are a function of particle size as well as windspeed, surface roughness, reference height, stability, and possibly relative humidity. Surface microlayers may affect roughness, but they are unlikely to exert significant control over deposition rates except on a very local level. Estimates of potential lake-derived concentrations in air indicate that bubble ejection may prove important in evaluating net atmospheric loading rates for some metallic species and perhaps organic substances as well.     

Trace Metal Mineral Equilibria in Lake Erie Sediments

The thermodynamic tendency of metal phosphate and carbonate mineral phases to precipitate in Lake Erie sediments has been calculated by means of an ion-pair model of the interstitial water chemistry. The calculations suggest that detrital calcite, aragonite, and dolomite should be dissolving in the sediments, but that iron and manganese carbonates should be precipitating. Regenerated phosphate should be reacting with calcium, iron, manganese, and lead to form authigenic mineral phases and be removed from solution. Whitlockite, Ca₃(PO₄)₂, and not hydrozylapatite, Ca₅(PO₄)₃OH, is the predicted primary controlling phase for phosphate, although apatites are supersaturated and may be precipitating. Zinc and cadmium are apparently controlled by other mechanisms, perhaps as sulfide phases, mixed mineral phases, adsorption, and/or ion exchange equilibria.     

Modeling Trace Metals in the Surface Microlayer

Extensive research on marine and freshwater surface microlayers has resulted in significant understanding of the extent, variability, and composition of surface accumulated materials. Various modeling techniques have been used to elucidate the sources, sinks, and concentration-controlling mechanisms of trace metal enrichment in surface microlayers. Among the approaches used have been calculations of enrichments, element ratios and correlations, and use of tracer elements, chemical element balances, and factor analyses. Recently, a mixing model using Pb-210 and Po-210 has been successfully applied to the surface microlayer and appears promising for other element pairs. Competitive complexation and computer simulation models are being used to predict the equilibrium composition of the surface microlayer, and investigations of particle residence time and reactivity are beginning to elucidate kinetic characteristics of surface microlayer processes. Although the significance of surface enrichment of trace metals is not yet understood, current modeling approaches are contributing to the formulation of important questions and answers about surface microlayer processes.     

Atmospheric Role in Trace Metal Exchange at the Air-Water Interface

Trace metals are enriched in the surface flm (SF) in freshwater and marine environments as compared to the bulk water. Contributions to the metal burden of the SF are derived both from atmospheric fallout and in-lake bubble-scavenging processes. A significant fraction of the Cu, Cd, Pb, and Zn in southern Lake Michigan SFs is derived from aerosol deposition. Geochemical analysis of aerosol, SF, and bulk water of Lake Superior strongly suggests that 1) most of the Fe, Mn, Ca, Pb, Cr, Zn, Cd, and Ni in the SF is derived from in-lake processes; and 2) enrichment of Cu, Pb, Zn, and Cd in lake aerosol is partially a result of bubble-bursting at the air-water interface. Estimated metal residence times in the SF may be on the order of minutes. Although the total quantity of metal in the SF represents a negligible fraction of the total water burden, the metal accumulation and enrichment at the air-water interface without geochemical/physical controls (i.e., precipitation, sedimentation) in a biologically-active regime suggests its importance in biotic uptake and possible direct introduction into the food chain.     

Estimation of Trace Metal Storage in Lake St. Clair Post-Settlement Sediments Using Composite Samples

Sediment cores were collected from 36 stations in Lake St. Clair during 1985 by divers. Usually within hours of collection, replicate cores were extruded and sectioned into 1-to 2-cm intervals. One replicate was stored by Canada Centre for Inland Waters personnel for organic contaminant, mercury, and major element analyses. The other replicate was stored by Great Lakes Research Division and Great Lakes Environmental Research Laboratory personnel for Cs-137, Pb-210, grain size, total carbon, and trace metal analyses. In order to estimate the mass of trace metals stored in the lake sediments, equal mass sections of each core were composited. These and individual sections of each core were analyzed and the total mass and anthropogenic mass of each metal in culturally impacted sediments were calculated. Estimated total and anthropogenic masses (metric tons) are: bismuth, 27 and 13; cadmium, 690 and 440; chromium, 5,100 and 1,800; copper, 3,000 and 1,500; nickel, 4,000 and 1,300; lead, 3,200 and 1,500; antimony, 25 and 13; and zinc, 11,000 and 3,300.     

从高背景的常规阳离子中有选择性地去除痕量重金属离子

针对国内各类饮用水体中痕量重金属离子存在于常量的碱金属、碱土金属离子高背景下的污染特点，提出不同于常规离子交换法的用弱碱性阴离子交换树脂去除水中重金属阳离子的表面络合理论，认为重金属离子可以与树脂中的胺基官能团上的氮原子发生表面络合反应，从而达到选择性去除的目的。该工艺具有选择性强，经济方便的优点。     

广州市地表堆积物中重金属含量分析研究

以地表堆积物中的Pb、Zn、Cu、Cd作为重点研究对象,在广州市分三个功能区(工业区、商业区、住宅区)进行地表堆积物样品的采集,从总含量、不同粒径级含量来分析堆积物中重金属的总体特性,并以研究结论为广州城市非点源的防治与管理提供理论依据。     

豫西山前典型地段地表水环境重金属污染评价

对豫西山前地区地表水取样150个,对样品进行As、Hg、Cr~(6+)、Cu、Cd、Zn、Pb等重金属含量分析测试,利用单项污染指数法、超标倍数(P_c)分级、地表水重金属综合累积污染指数、地表水密切值评价法等水体污染评价方法对研究区河流水质进行了分析评价。综合地表水重金属单项超标倍数、重金属综合累积污染指数、密切值等对双桥河污染程度进行评价,得出了密切值与综合累积污染指数的关系;利用综合累积污染指数评价法对各河流进行重金属污染评价得出:弘农涧河大部分河段处于中度以上污染,有些地方达到重度污染;利用超标倍数评价法对各河流进行重金属污染评价得出,各重金属元素的样品超标率As为4.00%、Hg为30.67%、Cu为10.67%、Cd为34.67%、Zn为11.33%、Cd为42.67%,其中Cd超标倍数最高,其次为Pb。     

杭州市内河水网表层沉积物重金属污染生态风险研究

根据2011年杭州市内河水网6条代表性河流表层沉积物4月、7月和10月3次重金属监测数据,运用HANKANSON潜在生态危害指数法,分别以当地背景值和工业化以前全球沉积物金属最高背景值作为参比值,对Cd、Cu、Zn、Pb重金属生态危害的主要贡献因子、不同河道表层沉积物重金属生态危害程度、内河水网表层沉积物重金属总的潜在生态风险水平等进行评价研究,以期引起有关部门的重视.     

Implications of Genome Alterations in Chironomus bernensis Klȍtzli (Diptera) for Assessment of Trace Metal Pollution in Two Bulgarian Rivers

This study assesses the effect of sediment contaminants as indicated by the measurement of trace metal levels in two large Bulgarian rivers (river Maritsa and a tributary and the river Chaya) on the genome of the abundant chironomid species Chironomus bernensis Klȍtzli. Six trace metals: Cd, Cr, Cu, Mn, Pb and Zn were analysed in the sediments plus the overlying water. The polytene chromosomes of C. bernensis were very sensitive to the pollutants on the basis of numerous somatic chromosome alterations. Two biomarkers based on the degree of somatic structural chromosome alterations—the somatic and cytogenetic indices were applied. Both indices are a sensitive and reproducible approach for assessing the genotoxic effect of contaminants in the sediments. The somatic index from the differentially contaminated sites varied from 1.93 to 2.61, indicating the sensitivity of the C. bernensis genome to anthropogenic stress. The cytogenetic index revealed a high level of pollution in the rivers with a score between 0.27 and 0.37 (<0.5 indicates ‘highly polluted’). The genome of C. bernensis responded to the trace metal pollution by the appearance of a ‘B’ chromosome in between 4.4% and 7.1% of the individuals and detected for the first time in this species. Pollution also induced a heterozygous state in one of the Nucleolar Organizers in up to 3% of the sampled populations. The sensitivity of the C. bernensis genome shows that this species is a good candidate for detecting the presence of genotoxic compounds in freshwater and assessing their genotoxic effects. Copyright © 2015 John Wiley & Sons, Ltd.     

Trace Organic Contaminants in the Detroit River

Concentrations of polychlorinated biphenyls (PCBs), polynuclear aromatic hydrocarbons (PNAs), chlorobenzenes (CBs), chlorophenols (CPs), and a number of other organochlorine compounds (OCs) have been determined in the surface microlayer, subsurface water, suspended solids, sediments, and in sediment pore water at 20 sampling stations in the Detroit River. The data are discussed in terms of contaminant sources, pathways, and sinks. Spatial trends within the river and relationships of contaminant groups within and between compartments are described. The results indicate a continuing input of all contaminant groups to the river from a variety of sources, particularly from sewage treatment plant effluents and several tributaries. The contaminant distributions and intercorrelations also indicate that major sources of PCBs, PNAs, OCs, and CBs are concentrated on the westerly river shore, while CPs enter the river mainly from the easterly shore.     

略阳县堆积层滑坡的发育规律研究

以略阳县堆积层滑坡病害为背景,采用现场调查结合理论分析的方法,研究了略阳县堆积层滑坡的发育规律,得到了略阳县堆积层发育滑坡的斜坡坡度、坡高、堆积层滑坡发生的周期。主要集中在略阳县城以北地带和滑坡发生集中地带。为略阳县堆积层滑坡治理提供了依据。更多还原     

Monitoring of Trace Organic Contaminants in Atmospheric Precipitation

The design and use of a year-round sampler for trace organic contaminants in wet precipitation are described. The sampler is electronically controlled and features a 0.25-meter-square stainless steel funnel with a 4-L amber glass bottle. The whole assembly is insulated and equipped with heating elements which permit collection of ice/snow samples. The samples are preserved in situ with methylene chloride and extracted again with methylene chloride in the laboratory. A small network of four sampling stations was established in the Great Lakes basin for the purpose of obtaining a refined estimate of atmospheric loading of trace organic pollutants to the Great Lakes. A total of 93 rain/snow samples was collected from the network during 1986. These samples were analyzed for organochlorine pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons. The most significant organochlorine pesticides found were alpha-HCH, gamma-HCH (lindane), and methoxychlor with concentrations in the range of 7–10 ng/L, 4–5 ng/L, and 2–7 ng/L, respectively. Other organochlorinated pesticides were measured occasionally at sub-nanogram levels. Polychlorinated biphenyls were also widely detected with mean concentrations of 7–10 ng/L. Polycyclic aromatic hydrocarbons were detected in about 50% of the samples. Some of the prevalent polycyclic aromatic hydrocarbons were phenanthrene, methylnapthalene, fluoranthene, and pyrene with mean concentrations of 50–200 ng/L. Deposition of agricultural chemicals (HCHs) was higher in Lake Superior and Huron but precipitation at Lake Erie and Lake Ontario contained more varieties of domestic pesticides.     

循环冷却水系统粘泥成因分析及控制

结合扬子石化公司炼油厂循环冷却水系统的实例,系统地分析了粘泥的成因,认为工艺介质的泄漏是粘泥多的主要原因,其次是絮凝作用.进而提出了相应的控制对策.     

龚嘴水库泥沙淤积现状分析

重点对龚嘴水库1994～2007年间的水库泥沙淤积数量和分布以及泥沙在库床上的纵、横淤积形态进行了分析研究,分析了水库泥沙淤积的影响因素,提出了水库泥沙淤积的主要问题,对进一步搞好水库水沙调度提出了建议.     

苏州轨道交通苏州火车站站结构设计

介绍了苏州轨道交通2号线苏州火车站的结构设计特点,探讨了新型的国铁车站与地铁车站合建时所采用的施工方法、结构方案的合理性,成果对多层轨道交通交汇点设计有参考价值。     

秦巴山区堆积层滑坡易损性评价方法研究

易损性反映了特定社会的人们及其所拥有的财产对自然灾害的承受能力,不同地区的不同承灾体在不同时间里对不同的灾害有不同的易损性特征.通过选取定性评价因子,对易损性进行等级划分,从而做到定性分析;通过对承灾体、时空概率和易损性调查,由引入的易损性指数可以对易损性做到定量分析.最后还提出了易损性的等级划分标准.结论表明:易损性指数是表示各因子在易损性判别中作用大小或强弱的物理量,是一个相对比较的数值,是定性分析的定量表示.     

Accumulation of freshwater red tide in a dam reservoir

The distribution and biomass of Peridinium bipes f. occultatum were observed in the autumns of 1991, 1992 and 1994 at the head of the Shorenji Dam reservoir (Mie prefecture, Japan). Summarizing observations and some other information, we discussed processes related to the accumulation of Peridinium biomass. In the study area, biomass of Peridinium increased at a similar rate to growth day by day, and roughly 2/3 of the daily maximum biomass fluctuated in a given day. The horizontal ‘import’ and ‘export’ of Peridinium biomass by flows mainly change the biomass of red tide at the upstream end of the reservoir. Plow control in the reservoir, as well as growth control, will also be important in suppressing freshwater red tide.