Metal Interactions in carcinogenesis†

Mixed exposures to a number of metallic compounds may give rise to a carcinogenic response in humans.

An interaction between occupational exposure to arsenic and cigarette smoking has been documented epidemiologically. A multiplicative effect was indicated concerning the occurrence of lung cancer when both of the exposures were present. Several experimental studies have been reported in the literature concerning interactions between benzo(a)pyrene and Fe₂O₃ as well as some other metallic compounds like Ni₃S₂, PbO, MgO and TiO₂ in relation to respiratory carcinogenicity. There is also limited evidence of a positive interaction between arsenic trioxide and benzo(a)pyrene. Particles containing V and Ni were obtained from the flue gases of power plants burning heavy fuel oil. Such particles were not carcinogenic themselves but enhanced the carcinogenicity of benzo(a)pyrene even more efficiently than Fe₂O₃.

Increased dietary selenium intakes can decrease the carcinogenicity of several organic carcinogens in animals and dietary zinc can effectuate both enhancement and inhibition of carcinogenicity depending on dietary concentration.     

欧洲地表酸化水体恢复--未来展望

到目前为止,有关欧洲地表酸化水体大范围化学恢复的文献层出不穷,而有关生物恢复的报道并不多见.建立在现今欧洲排放减少计划之上的模型研究表明,化学恢复仍将继续.而影响恢复进程的诸多不确定性因素主要包括:未来生态系统内氮的可能行为和气候变化的影响.下列4个与气候变化相关的因子可能对未来恢复进程产生影响:①海水盐分入侵事件爆发频率和强度增加;②干旱发生频率和强度上升;③有机碳交换周期加快;④硝化作用增强.目前降低水体酸化程度的国际性协作是成功的,但是未来还有大量问题需要解决,也会遇到许多困难.对未来硫、氮排放减少后以及气候变化背景下酸化地表水体的水化学和水生生物变化需要继续监测.     

Hydrogeochemical comparison and effects of overlapping redox zones on groundwater arsenic near the Western (Bhagirathi sub-basin, India) and Eastern (Meghna sub-basin, Bangladesh) margins of the Bengal Basin

Although arsenic (As) contamination of groundwater in the Bengal Basin has received wide attention over the past decade, comparative studies of hydrogeochemistry in geologically different sub-basins within the basin have been lacking. Groundwater samples were collected from sub-basins in the western margin (River Bhagirathi sub-basin, Nadia, India; 90 samples) and eastern margin (River Meghna sub-basin; Brahmanbaria, Bangladesh; 35 samples) of the Bengal Basin. Groundwater in the western site (Nadia) has mostly Ca-HCO(3) water while that in the eastern site (Brahmanbaria) is much more variable consisting of at least six different facies. The two sites show differences in major and minor solute trends indicating varying pathways of hydrogeochemical evolution However, both sites have similar reducing, postoxic environments (p(e): +5 to -2) with high concentrations of dissolved organic carbon, indicating dominantly metal-reducing processes and similarity in As mobilization mechanism. The trends of various redox-sensitive solutes (e.g. As, CH(4), Fe, Mn, NO(3)(-), NH(4)(+), SO(4)(2-)) indicate overlapping redox zones, leading to partial redox equilibrium conditions where As, once liberated from source minerals, would tend to remain in solution because of the complex interplay among the electron acceptors.     

Characterization of land-based sources of pollution in Jobos Bay,Puerto Rico: status of heavy metal concentration in bed sediment

As part of an assessment of land-based sources of pollution in Jobos Bay, Puerto Rico, sediment samples were collected at 43 sites to characterize concentrations of a suite of pollutants, including metals. Fifteen major and trace metals (Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn Ni, Pb, Sb, Se, Sn, and Zn) were measured along with total organic carbon and grain size in surficial sediments. For most metals, maximum concentrations were seen in the eastern bay; however, values were still within concentration ranges found in other estuarine systems. In contrast, silver was higher in the western region. In general, metal distribution in the bay was positively correlated with grain size. Additionally, correlations between Al and other metals suggest natural sources for metals. The data presented here suggest that, although the Jobos Bay watershed contains both urban centers along with industrial and agricultural developments, anthropogenic inputs of metals may be negligible.     

酸化湖泊水生生物恢复的理论框架构建

在欧洲和北美广大地区,随着大气硫沉降的减少,地表水体酸度正在逐渐降低,但是对水质改善的生态响应过程却依然扑朔迷离.有些湖泊和河流的生物正在恢复,有些水体的生物并没有得到恢复.为理解这些生物响应的差异,有利于酸雨问题的有效管理,我们需要对下面2个问题有清晰的认识:①生物群落恢复所必须经历的生态步骤;②倘若恢复受阻,从哪里着手对恢复进程实施干预,如何干预.本文通过构建一套理论框架来回答上述问题.第一层框架是基于生态学考虑而构建的,通过决策树来反映生态恢复进程中必须经历的若干步骤,步骤之间则通过管理工具或对瓶颈的响应来连接.水质不佳,移生生物供给不足以建群,以及群落水平上对恢复动态变化的阻碍等等都可能成为恢复的瓶颈所在.第二层框架则是基于管理层次来构建的,为了克服瓶颈,框架指明从哪里着手对恢复进程实施干预,为建模来进一步将框架具体化,需要做哪些研究.一旦我们可以用模型来预测酸化水体生态恢复的速率和程度,对硫排放减少带来的效益评价就变得简单起来.而这些模型的构建需要充分认识恢复进程中的生态步骤.本文提出的理论框架将有助于我们朝这个目标迈进.     

LCA of environmental and socio-economic impacts related to wood energy production in alpine conditions: Valle di Fiemme (Italy)

An extended Life Cycle Assessment (LCA) is performed for evaluating the impacts of a woody biomass supply chain for heating plants in the alpine region. Three main aspects of sustainability are assessed: greenhouse gas emissions, represented by global warming potential (GWP) impact category, costs and direct employment potential. We investigate a whole tree system (innovative logging system) where the harvest of logging residues is integrated into the harvest of conventional wood products. The case study is performed in Valle di Fiemme in Trentino region (North Italy) and includes theoretical and practical elements. The system boundary is the alpine forest fuel system, from logging operations at the forest stand to combustion of woody biofuels at the heating plant. The functional unit is 1 m³ solid over bark of woody biomass, delivered to the district heating plant in Cavalese (Trento). The relative sustainability of traditional and innovative systems is compared and energy use is estimated. Results show that the overall GWP and costs are about 13 kg CO_2equivalent and 42 euro per functional unit respectively for the innovative system. Along the product supply chain, chipping contributes the greatest share of GWP and energy use, while extraction by yarder has the highest financial costs. The GWP is reduced by 2.3 ton CO_2equivalent when bioenergy substitutes fuel oil and 1.7 ton CO_2equivalent when it substitutes natural gas. The sensitivity analysis illustrates that variations in fuel consumption and hourly rates of costs have a great influence on chipping operation and extraction by cable yarder concerning GWP and financial analysis, respectively. This is confirmed by sensitivity analysis. Better technologies, the use of biofuels along the product supply chain and more efficient systems might reduce these impacts. Replacing the traditional system with the innovative one reduces emissions and costs. A low energy input ratio is required for harvesting logging residues. The direct employment potential is a conflicting aspect and needs further investigations.     

Assessment of coastal storm impacts on contaminant body burdens of oysters collected from the gulf of Mexico

This study evaluated changes in oyster tissue contaminant levels following North Atlantic tropical cyclones to determine if changes in contaminant concentrations were predictable. The basis for this study was analysis of coastal chemical contaminant data from the National Oceanic and Atmospheric Administration's (NOAA) National Status and Trends Mussel Watch Program and NOAA's National Weather Service storm track data. The tendency for contaminant (metals and organic compounds) body burdens to increase or decrease in oyster tissue after a storm was assessed using contingency and correspondence analyses. Post-storm contaminant levels in oysters revealed a consistent pattern of distribution, which could be described as follows: (1) most of the organic contaminants stay within their long-term concentration ranges, (2) very few organic contaminants decreased, and (3) metals overwhelmingly tend to increase.     

Estimation and validation of PM2.5/PM10 exhaust and non-exhaust emission factors for practical street pollution modelling

In order to carry out efficient traffic and air quality management, validated models and PM emission estimates are needed. This paper compares current available emission factor estimates for PM₁₀ and PM_2.5 from emission databases and different emission models, and validates these against eight high quality street pollution measurements in Denmark, Sweden, Germany, Finland and Austria.The data sets show large variation of the PM concentration and emission factors with season and with location. Consistently at all roads the PM₁₀ and PM_2.5 emission factors are lower in the summer month than the rest of the year. For example, PM₁₀ emission factors are in average 5–45% lower during the month 6–10 compared to the annual average.The range of observed total emission factors (including non-exhaust emissions) for the different sites during summer conditions are 80–130 mg km⁻¹ for PM₁₀, 30–60 mg km⁻¹ for PM_2.5 and 20–50 mg km⁻¹ for the exhaust emissions.We present two different strategies regarding modelling of PM emissions: (1) For Nordic conditions with strong seasonal variations due to studded tyres and the use of sand/salt as anti-skid treatment a time varying emission model is needed. An empirical model accounting for these Nordic conditions was previously developed in Sweden. (2) For other roads with a less pronounced seasonal variation (e.g. in Denmark, Germany, Austria) methods using a constant emission factor maybe appropriate. Two models are presented here.Further, we apply the different emission models to data sets outside the original countries. For example, we apply the “Swedish” model for two streets without studded tyre usage and the “German” model for Nordic data sets. The “Swedish” empirical model performs best for streets with studded tyre use, but was not able to improve the correlation versus measurements in comparison to using constant emission factors for the Danish side. The “German” method performed well for the streets without clear seasonal variation and reproduces the summer conditions for streets with pronounced seasonal variation. However, the seasonal variation of PM emission factors can be important even for countries not using studded tyres, e.g. in areas with cold weather and snow events using sand and de-icing materials. Here a constant emission factor probably will under-estimate the 90-percentiles and therefore a time varying emission model need to be used or developed for such areas.All emission factor models consistently indicate that a large part (about 50–85% depending on the location) of the total PM₁₀ emissions originates from non-exhaust emissions. This implies that reduction measures for the exhaust part of the vehicle emissions will only have a limited effect on ambient PM₁₀ levels.     

Electricity demand in a changing climate

Our interest is in electricity demand and the temperature aspects of climate change. Electricity consumption is of interest both from the perspectives of adaptation to climate change and emission reductions. We study the relationship between European electricity consumption and outdoor temperature and other variables, using a panel data set of 31 countries. Apart from providing a rare quantitative window into adaptation, the study contributes demand system parameters with respect to price and income. The results suggest that weather has a statistically significant effect on electricity demand, with effects that are of plausible magnitude. In a simulation of climate change for the next 100 years—other factors held constant—we find that the demand for heating will decrease in Northern Europe while the demand for cooling will increase in Southern Europe. In countries like Cyprus, Greece, Italy, Malta, Spain, and Turkey the net effect of increased cooling outweighs decreased heating consumption whereas in most of Europe the opposite holds. The largest estimated partial impact is 20%, which predicted increase in adaptive consumption for Turkey and decrease in adaptive consumption for Latvia. Estimated elasticities with respect to income and price are 0.8 and minus 0.2 respectively: plausible in the light of the literature. As a discussion item, we add that electricity consumption changes due to temperature change likely will be small compared to those due to other factors, such as changes in income, demography and technology. The study does not include effects of climate change other than through electricity consumption.