Dynamic behaviour of 137Cs contamination in trees of the Briansk region, Russia

Seven trees were felled in the Briansk region in 1997. The trees were sectioned for sampling, both at different heights and according to year rings, and samples were analysed for content of 137Cs. In general, the specific activity of 137Cs was much higher in the fresh parts of the three (needles, leaves and twigs) than in the core wood. The year ring study showed that 137Cs had penetrated deeply in to the trunk, and no peak was detectable in the year ring corresponding to the Chernobyl accident in 1986. The specific activity in the trunk wood had a maximum at the height corresponding to the growth years at approximately 1986. Neutron activation analysis was used to analyse for stable Cs. The results showed that the relationship between concentrations of 137Cs and stable caesium is much higher in the newer parts of growing trees than in the older parts. Together with a tendency of inward migration this leads to a preliminary conclusion that the 137Cs activity will continue to accumulate in the core wood.     

Historical changes in lead concentrations in tree-rings of sycamore,oak and Scots pine in north-west England

Lead concentrations in tree rings of sycamore (Acer pseudoplatanus L.), oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.) sampled at a parkland in north-west England were measured in wood formed since the mid-1800s. Concentrations of Pb in Scots pine and oak peaked in wood formed between 1900 and 1940, most likely because of Pb accumulation in heartwood, indicating that oak and Scots pine are unsuitable for monitoring temporal changes in Pb deposition at the study site. In contrast, Pb concentrations in sycamore, a species that has similar heartwood and sapwood chemistry, were relatively constant in wood formed between the mid-1800s and 1950. Lead concentrations decreased steadily in sycamore tree rings formed after the 1950s, and decreased more abruptly in wood formed after 1985. This sharp decrease in wood Pb cannot be due to decreases in soil Pb concentration. Stable Pb isotope analysis was used to further investigate Pb patterns in sycamore wood. Excess 206Pb/207Pb ratios in tree-rings of sycamore were relatively constant, approximately 1.17, in wood formed prior to the 1930s, but decreased steadily thereafter reaching a minimum value of approximately 1.16 in wood formed between 1975 and 1985 after which time 206Pb/207Pb ratios increased. This pattern is consistent with changes in Pb isotope ratios measured in peat, sediment and aerosol samples in the UK. However, the magnitude of the decrease in 206Pb/207Pb (largely due to gasoline Pb) is considerably lower than in other studies and our estimates indicate that less than 20% of the total Pb in sycamore wood measured since the mid-1800s is derived from gasoline emissions. A more likely explanation for the pattern of Pb observed in sycamore tree rings is that soil Pb accumulates within rings of the diffuse porous wood over a number of years. Such uptake patterns would result in lower Pb concentrations in the outer (more recently formed) tree rings, which coincide with recent reductions in Pb deposition in the UK. Overall, this study indicates that tree ring chemistry is unsuitable for monitoring historical changes in Pb deposition at the study site.     

Analytical electron microscopy of combustion particles: a comparison of vehicle exhaust and residential wood smoke

Particulate matter has been associated with a number of adverse health effects. Since combustion particles from vehicle exhaust and wood smoke are common constituents of ambient air, the morphology and elemental composition of particles from these two sources were analysed and compared using single particle analysis. Ambient air particles were collected in locations dominated by vehicle exhaust or residential wood smoke. To verify the source contributions to the ambient air samples, particles were collected directly from the combustion sources. All particulate samples were analysed on carbon extraction replica by transmission electron microscopy (TEM) and X-ray microanalysis (XRMA). The particles were classified into four groups based on morphology and elemental composition. Carbon aggregates were the only particles identified to originate from combustion sources and accounted for more than 88% of the particle numbers in the ambient air samples from both sources. The carbon aggregates were therefore further analysed with respect to morphology and elemental composition on germanium extraction replica. Carbon aggregates from vehicle exhaust were characterised by higher levels of Si and Ca compared to wood smoke aggregates that contained higher levels of K. The S content in aggregates from both sources was probably caused by interaction with gases in the air. Furthermore, the diameters of primary particles from vehicle exhaust were significantly smaller (27+/-7 nm) than the diameters for wood smoke (38+/-11 nm). The observed differences in elemental profiles and primary particle diameters for vehicle exhaust and wood smoke may influence the health effects caused by these particles.     

Tree rings as Pb pollution archives? A comparison of 206Pb/207Pb isotope ratios in pine and other environmental media

Tree rings, if validated as an environmental archive for pollution, would provide a convenient, geographically widespread archive for studying the temporal and spatial distribution of atmospheric pollutants. We collected tree-ring records from Scots pine (Pinus sylvestris L.), ranging in age from 100 to 300 years and from one spruce (Picea abies), from sites in southern and northern Sweden and analyzed their stable lead isotopic composition (206Pb/207Pb). These results are compared to the Pb isotopic composition in soil profiles from each of the sites and temporal changes in the 206Pb/207Pb ratio in peat and lake sediment deposits in Sweden. The mineral soils at each site are characterized by high 206Pb/207Pb ratios (> 1.35), while the ratios in the mor layer are low (1.14-1.16) and characterized by atmospheric lead pollution. The 206Pb/207Pb ratios of the tree rings, typically approximately 1.18-1.20, indicate a significant (10-30%) contribution of Pb derived from the underlying mineral soil. While peat and lake sediment records show that the 206Pb/207Pb ratio of atmospheric deposition has varied over time, with a pronounced trough between approximately 1930 and 1990, the tree rings show no similar trend. Further comparison of published Pb isotope data from other tree-ring records with time series from peat bogs and herbarium samples also shows poor agreement, and indicates that tree rings always contain a mixture of pollution Pb and Pb from the underlying mineral soil. The majority of Pb in the wood is derived from atmospheric pollution either directly, through aerial interception, or indirectly, through uptake from the large pool of accumulated pollution Pb in the soil. Since the Pb isotope ratios of the wood indicate that some natural Pb is taken up into the tree, then it must also be concluded that some fraction of the pollution Pb in the wood is likewise taken up from the forest soil. Based on the Pb isotope analyses, we can only conclude that dendrochemical records are not useful in temporal studies of metal pollution.     

Simulation of tunnel fires using a zone model

The use of a fire zone model for simulating tunnel fires is reported in this paper. The zone model CFAST version 2.0 was selected as the fire simulator. Numerical experiments were performed in an arbitrary tunnel by considering it as a single compartment, a two-room structure and a three-room structure. Five fires that would have a high likelihood of occurring in a tunnel were considered. They were caused by burning wood cribs, a passenger train, a subway coach, a truck, and a school bus. Results are also compared with another zone model, CCFM.VENTS, and those predicted from a self-developed fire field model for studying the aerodynamic and smoke movement in a tunnel. Further, experimental data collected in a smaller tunnel from an abandoned copper mine in Norway was used to justify the prediction.     

Distribution and mobility of chromium, copper, and arsenic in soils collected near CCA-treated wood structures in Korea

Chromated copper arsenate (CCA) is currently the most commonly used wood preservative in Korea. Questions, however, have been raised regarding the potential environmental impacts of metal leaching from CCA-treated wood to soil. Although a number of researchers from other countries have reported that chromium, copper, and arsenic do leach from CCA-treated wood over time, to date few field studies have been performed on those metals in soils adjacent to CCA-treated wood structures in Korea. The present study was conducted to determine the lateral and vertical distributions and accumulation of chromium, copper, and arsenic in soils collected from CCA-treated wood structures. A total of fifty-five composite soil samples were collected from four CCA-treated wood structures of approximately one year in age. The samples were analyzed for physicochemical properties as well as for the total chromium, copper, and arsenic concentrations. The chromium, copper, and arsenic concentrations in soil samples adjacent to the structures were as high as 79.0, 98.9, and 128 mg/kg, respectively, compared to background soil samples (48.2, 26.9, and 6.27 mg/kg, respectively). Arsenic was more mobile in soil than chromium and copper. The concentration gradient of arsenic in soil was observed only to the depth of approximately 5 cm in one year of outdoor exposure, whereas chromium and copper apparently remained near the surface (approximately less than 1 cm) after their release. Future efforts should be made to observe seasonal impacts on the release of metals and incorporate metal speciation into determining more detailed mobility and distribution.     

木粉含量对PE-WPCs射流等离子体处理时效性的影响

采用空气射流等离子放电技术对木粉/聚乙烯复合材料(PE-WPCs)进行表面处理,以改善其胶接性能,通过接触角和胶接强度测试、傅里叶红外光谱(FTIR)和X射线光电子能谱(XPS)方法等分析研究了木粉含量对PE-WPCs等离子体处理时效性的影响.结果表明:经射流等离子体处理后,PE-WPCs表面产生了含氧极性基团,表面接触角减小,胶接强度明显提高;随着放置时间的延长,处理后PE-WPCs表面极性基团数量减少,表面接触角增大,胶接强度略有下降,表现出一定的处理时效性;PE-WPCs木粉含量越高,处理时效性越小;尽管存在时效性,但处理后PE-WPCs的胶接强度仍远高于未处理PE-WPCs.     

Accumulation of heavy metals in circumpolar willow ptarmigan (Lagopus l. lagopus) populations

A circumpolar survey of heavy metals in willow ptarmigan liver and kidney revealed considerable variations in Cd content in Canada and Scandinavia. The Cd content in central Canada was comparable with that in Scandinavia and Russia, at least for kidney. However, in both liver and kidney the median for Canada as a whole was much higher than in the other countries. Some Canadian locations had exceptionally high levels, several birds having >50 mg kg(-1) in liver and >400 mg kg(-1) in kidney. In Norway, the Cd content was highest in central mountain areas in south Norway and inland locations in the two northernmost counties. Five locations in central and north Norway showed mean Cd levels in kidney above 100 mg kg(-1). It is difficult to evaluate regional differences in Sweden, but most locations had the same Cd level as moderately contaminated locations in Norway. Cd levels in Russia were comparable to moderately contaminated locations in the other countries. Due to a high intake of willow, naturally rich in Cd, direct comparison of the Cd level in willow ptarmigan from different locations cannot reveal the effects of long-range pollution. The Pb concentration in willow ptarmigan kidney and liver varied significantly in Norway and Canada, but not in Sweden and Russia. Levels in Sweden and Russia were comparable to those in Canada and low levels in Norway. The highest median value from all locations within countries was found in Norway, both in liver and kidney. The highest Pb content was found in south Norway, indicating an effect of long-range pollution in willow ptarmigan. The level in western Canada was significantly higher than in central Canada. The Hg content in liver varied significantly from one location to another in all the countries and in kidney everywhere except Sweden. In Scandinavia, there is no distinct regional pattern. Canada had a significantly higher Hg level in central than western regions in both tissues the opposite of that found for Cd and Pb. Cu and Zn showed significant variations from one location to another in liver and kidney in Canada and Norway, but only in kidney in samples from Sweden. Comparison between western and central Canada revealed a significant difference for Cu in liver, samples from central Canada having more. There are no significant differences from one country to another, but some localities in Canada seem to have higher Cu concentrations in kidney than are found in Scandinavia and Russia.     

Combining hygrothermal and corrosion models to predict corrosion of metal fasteners embedded in wood

A combined heat, moisture, and corrosion model is presented and used to simulate the corrosion of metal fasteners embedded in solid wood exposed to the exterior environment. First, the moisture content and temperature at the wood/fastener interface is determined at each time step. Then, the amount of corrosion is determined spatially using an empirical corrosion rate model and the inputs of the first step. The result is a corrosion profile along the length of the fastener generated by summing the corrosion depths determined at each time step. We apply the combined model to predict the annual corrosion depth along a metal fastener in wood decks situated in nine different US cities. Corrosion profiles are found to exhibit the same general shape independently of climatic load, with the largest amount of corrosion occurring at 1–5 mm from the wood surface with corrosion depths ranging from 5 μm in Phoenix, Arizona to 45 μm in Hilo, Hawaii. Corrosion is confined to the first 7–20 mm of the fastener below the wood surface. By varying the climatic loads, we find that although there is a definite relation between total annual rain and total annual corrosion, under the same rain loads corrosion is higher for a climate with more evenly distributed rain events. The proposed combined model is able to capture corrosion behavior under varying loading. A sensitivity analysis gives guidelines for future corrosion modeling work for fasteners in wood.     

挪威海底公路隧道经验——施工、运行、费用和维护

根据2002年关于挪威海底公路隧道的一论文集(挪威公路管理局公路技术部编辑,题目为"论文集98——挪威海底公路隧道",将详细阐述挪威海底隧道的施工建造等经验。挪威第一条海底公路隧道是在1983年通车的,随后建成了另外24条海底公路隧道,至今共有25条海底公路隧道建成通车,总长度达100km。几条新的海底公路隧道目前正在建设中,还有几条则在规划当中,其中最长将达24km。大多数条海底公路隧道是单洞双线,但是当坡度大于6%时,有些隧道就增加一条线。海底公路隧道都位于沿海岸线的干线公路上,以代替原有的繁忙的轮渡,并建立大陆与当地之间的无轮渡连接。据此,主要介绍这些隧道工程中得到的经验,总的来说,海底公路隧道的建设费用逐渐降低,但是各工程间差异很大,各个隧道的运行和维护的费用也相差悬殊,再投资和设备花费也特别高。经验表明,随着渗水量逐年减少,因而抽出渗透水的要求也降低了。介绍了1996年前17条海底隧道中发生的事故和火灾,对19起造成人身伤害的事故进行了分析。其事故发生率极低,只有0.09(每年每一百万车辆每公里发生的事故次数),最高的事发率是在陡坡的年平均日通车量(AADT)低于1500的隧道中。挪威海底隧道中只发生过3起火灾事故,低于交通事故率10%,而这项研究只包括了17条隧道中发生的19起事故。     

Arsenic in tree rings at a highly contaminated site

Arsenic concentrations were measured in annual rings, pith, bark, and leaves of five tree species (four genera) from a site highly contaminated with As in Vineland, New Jersey, and two nearby uncontaminated areas. The highest As concentrations were found in bark (0.68+/-0.89 mg/kg, n=16) and leaves (1.9+/-1.8 mg/kg, n=4) from the contaminated area. Tree-ring As levels from the contaminated area (0.28+/-0.15 mg/kg, n=32) were low but still considerably higher than those from the control areas (0.06+/-0.06 mg/kg, n=30). There is a generally positive relationship between soil and tree-ring As levels. The overall low uptake of As by trees contrasts with that of P, a chemical analog for As(V) in aerated soils. Much higher P concentration in sapwood than in heartwood indicates that P is exported into more recently formed wood during the conversion from sapwood to heartwood; this again is drastically different than the behavior of As which is present in sapwood and heartwood at comparable levels. Variable sapwood As concentrations observed in detailed radial profiles of tree-ring chemistry of a pine and an oak from the contaminated site suggest that As is most likely transported among multiple rings within the sapwood. Therefore, tree species for which sapwood is thin (e.g., oak as in this study) should be preferred for reconstructing the history of contamination of a site. Due to the possibility of lateral translocation between growth rings, further studies are necessary to understand within-tree As transport and storage before dendrochemistry can be confidently accepted for such applications.     

Estimation of the mass-balance of selected metals in four sanitary landfills in Western Norway, with emphasis on the heavy metal content of the deposited waste and the leachate

A worst-case simulation of the mass-balance for metals in the waste deposited during 1 year and the levels of cadmium (Cd), lead (Pb), mercury (Hg), chromium (Cr) and iron (Fe) in the leachate was calculated for four sanitary landfills in Western Norway. Estimates of the levels of metal content in mixed municipal solid waste (MSW) were found by using recent literature values calculated in a mass-balance study at a Norwegian waste incinerator plant. Leachate from the landfills were sampled and analyzed monthly during 1 year, and from these measurements the total annual discharge of the selected metals through the leachate was determined. The levels of the measured heavy metals in the leachate were low. For Cd less than 0.06%, for Pb less than 0.01% and for Hg less than 0.02% of the estimated year's deposited mass of metals were leached from the landfills during the year of investigation. The high retention of these metals are most likely due to sulfide precipitation, but also due to the immobile condition of the metals in their original deposited solid state (plastics, ceramics, etc.). The percentage of Cr leached was relatively higher, but less than 1.0% per year. The mass balance of Fe suggests that this element is more mobile under the prevailing conditions. The percentage of Fe leached varied and was estimated to be between 1.9% and 18%. The present study clearly supports the theory that MSW only to a small extent will lead to discharge of metals if deposited at well-constructed sanitary landfills with top layers.     

Part Hare, Part Tortoise – Explaining patterns in Norwegian public utilities reforms 1990–2010

In this article we compare four Norwegian public utilities sectors: the electricity industry, the e-com industry, the railway and the postal service. All sectors have been subject to public policy reforms since the 1980s, though reform content and degree varies. In the electricity industry Norway is a liberalization forerunner - a virtual reform “hare”, to borrow from Olsen’s (1996) Aesop’s fable metaphor. In other network industries such as the railway Norway is a reform “tortoise”. We seek to answer the question: How and why has governance of the four industries been reformed? We explore four possible explanations for similarities and differences across sectors: technological change, market conditions, agency and European Union (EU) regulation. We cannot identify a national model for reforms across these sectors. We find single factors standing out in the explanation of the reforms in the various sectors. The puzzle is that it is different factors in different sectors.     

Dislodgeable copper,chromium and arsenic from CCA-treated wood surfaces

Chromated copper arsenate (CCA) is commonly used to preserve wood, but its use poses risk of arsenic exposure. In order to evaluate the extent of exposure to As from physical contact with CCA-treated wood, dislodgeable As from treated wood surfaces (as well as Cu and Cr) was determined as a function of weathering time using dampened polyester wipe materials. Six sets of 2.5-m-long CCA-treated boards, three-four boards per set, were purchased from lumber yards and cut into 30- or 60-cm coupons. A total of 44 such coupons were placed outdoors and the dislodgeable CCA components from the surfaces of the wooden coupons were periodically determined over a 1- or 2-year period by a systematic wipe method followed by nitric acid extraction of the CCA components from the cloth. In all 316 samples, appreciable amounts of the three elements, Cu, Cr and As, were detected. The amounts of surface-dislodgeable As, the most potentially hazardous element and the one of major concern in this study, varied from 5 to 122 microg/100 cm(2) with an average value of 37+/-22 microg/100 cm(2). There was considerable variation in As dislodged among coupons, boards, sets and time. Test coupons that tended to release relatively higher (or lower amounts) over time initially, continued to do so over time. However, the amounts of arsenic dislodged over time did not follow a simple pattern. While the As dislodged tended to decrease with time during the first year, it approached the initial value or increased somewhat during the second year, presumably due to surface rejuvenation effects caused by erosion and weathering. When all the data were normalized to the initial values, no trend emerged, as indicated by the average normalized value of 1.0+/-0.4 for As dislodged over time. Apparently, on installations constructed with CCA-treated wood, arsenic may remain available for a number of years.     

Simulating the effects of fuel type and geometry on post-flashover fire temperatures

This paper discusses the effect of fuel type and geometry on predicted compartment temperatures derived from computer modelling of post-flashover compartment fires. Many previous studies have investigated post-flashover fires with either wood crib or liquid pool fuels, but very few analytical or experimental studies have considered realistic wood-based fuels with different ratios of surface area to volume, combined with plastic-based fuels. A simple single zone fire model was used to calculate the temperatures in post-flashover compartment fires. The program includes a catalogue of furniture items, each with fuel mass loss rate evaluated on the basis of a constant regression rate on all exposed surfaces. The program also includes a pool-burning model and considers wood fuels and thermoplastic fuels burning together inside a compartment. Use of the model shows that the total fuels load alone is not sufficient to characterise a post-flashover fire. The fire temperature is highly dependent on the fuel type and geometry. For given ventilation and total fuel load, the resulting temperature depends greatly on the average thickness of the wood fuels and the presence of thermoplastic fuels. The ratio of the available fuel surface area to the ventilation opening is particularly important. Several fire scenarios involving different fuel types and characteristics are simulated and compared with Eurocode parametric fires.     

Quantification and speciation of mercury in soils from the Tripuí Ecological Station, Minas Gerais, Brazil

Contents of total mercury, organic carbon, total sulfur, iron, aluminum and grain size and clay mineralogy were used along with Pearson's correlation and Hg thermal desorption technique to investigate the presence, distribution and binding behavior of Hg in soils from three depths from the Tripuí Ecological Station, located near Ouro Preto, Minas Gerais State, Brazil. The soils studied had predominantly medium and fine sand texture (0.59-0.062 mm), acid character and Hg contents ranging from 0.09 to 1.23 microg/g. The granulometric distribution revealed that Hg is associated with coarse sand (2-0.59 mm) and silt and clay (<0.062 mm) and presents similar Hg concentrations in both fractions. Mercury distribution in soil profiles showed that Hg was homogeneously distributed throughout the depths at most sites. Hg thermal desorption curves show that mercury occurs not only as Hg2+ predominantly bound to organic components in most of the samples, but also in the form of cinnabar in some. Pearson's correlation confirmed that mercury is associated with organic matter and sulfur and possibly with sulfur-bearing organic matter in most samples.     

Influence of temperature on fixation of copper–ethanolamine-based wood preservatives

Market share of copper–ethanolamine-based wood preservatives is increasing in the past decade; despite of the fact that copper fixation is still not comparable to fixation of copper–chromium-based ones. One of the reasons for increased emissions originates in ethanolamine. Ethanolamine excesses depolymerizes lignin macromolecule, what consequence in higher leaching rates. In order to eliminate this negative influence of ethanolamine, Norway spruce wood blocks were impregnated with three different copper–ethanolamine solutions of three concentrations. After impregnation, specimens were dried at four different temperatures (25, 50, 75 and 103 °C) and, afterwards, leached according to the modified ENV 1250 procedure. The results showed that increased temperatures during fixation did not decrease but increased copper leaching. It is presumed that the main reason for observed fact is ethanolamine, which did not evaporate from wood. Unfortunately, increased temperatures dramatically increase lignin depolymerization, as well as copper leaching.     

Modeling pyrolysis of wet wood under external heat flux

Experiments on the thermal decomposition of wet wood in air were carried out in this work. The samples (typically 100×100 mm exposed surface, 15 mm thick) of several species with moisture content from 5% to 30% were subjected to a uniform heat flux 20–70 kW m⁻². A one-dimensional pyrolysis model is proposed to examine the influence of heat flux, species and moisture content on the process of thermal decomposition of wet wood. Temperature profiles at different points and solid conversion are calculated and compared with experimental data. There is good agreement between the experimental and calculated results.     

Influence of wood species,treatment method and biocides concentration on leaching of copper–ethanolamine preservatives

Cu–ethanolamine-based preservatives are currently the most important alternatives for classical chromated-copper formulation. However, emissions of Cu from wood impregnated with copper–ethanolamine-based preservatives are still higher compared to emissions from wood preserved with copper–chromium based preservatives. In order to elucidate leaching of copper from specimens treated (brushed, soaked or vacuum-impregnated) with different copper–ethanolamine containing biocides of two different concentrations the following research on specimens made of Norway spruce (Picea abies), Scotch pine (Pinus sylvestris) and Beech (Fagus sylvatica) were performed. The results showed that leaching is significantly affected by the wood species used. The lowest leaching rates were determined in specimens made of spruce, while the highest ones were determined in beech wood. Concentration of active ingredient influences the Cu fixation as well. Unfortunately, ethanolamine at higher concentration causes depolymerisation of lignin macromolecules, which results in increased copper leaching.     

Role of inland water sediments as sinks for anthropogenic sulfur

The accumulation of sulfur in the sediments of lakes and reservoirs has been estimated to be about 0.7 and 8.0 million tonnes per year respectively. Such a sink thus accounts for about 10% of the sulfur released annually from fossil fuel combustion and for a significant fraction of the “missing” sulfur in the current global budgets. The recent increases in the sulfur contents of inland water sediments (about 3-fold in the Great Lakes ecosystems, for example) have been attributed to the increased pollution of water bodies with sulfur.