Sediment analysis to support the recent glacial origin of DDT pollution in Lake Iseo (Northern Italy)

In the present study, a depth-related distribution of Persistent Organic Pollutants (POPs) in sediments of Lake Iseo, one of the major southern Alpine Italian lakes, is reported in order to further test the hypothesis of melting Alpine glaciers as a secondary source of contamination. In a previous paper, a “glacier contamination hypothesis” was suggested to explain the unexpected contamination of the biota of Lake Iseo, mainly fed by the Alpine melting ice.The sediment core analyses covered around the last 50 years. The organic matter profile evaluated as a Loss-On-Ignition percentage indicated transition of the basin from an oligotrophic to a mesotrophic status at around the early 1970s, but there was no evidence of the shift to eutrophy in the 1980s. Among DDTs, pp’DDE was the predominant metabolite, accounting on average for 79.4% of the total DDT concentrations and ranging from 6.4 to 447.5 ng g⁻¹ d.w. PCBs ranged from 5.0 to 163.7 ng g⁻¹ d.w. The maximum PCB concentrations were found in sediment layers corresponding to the 1970s when the highest production and use of these compounds occurred in Italy. In contrast, concentrations of DDTs showed a sharp increase from the early 1990s, long after their agricultural use was banned in Italy. This delayed pollution provides support for the hypothesis that the recent retreat of glaciers represents a secondary pollution source for old pesticides that were stored in the ice at the time of their use in agriculture.     

The use of hard- and soft-modelling to predict radiostrontium solid-liquid distribution coefficients in soils

The solid-liquid distribution coefficient (K_d) is the parameter that governs the incorporation of contaminants in soils. Its estimation allows the prediction of the fate of contaminants in the short- and long-term after a contamination event. Here, the K_d of radiostrontium (K_d(Sr)), a radionuclide of significant environmental interest, was predicted by hard models, which are based on knowledge of the mechanisms governing its sorption, and by soft models based on Partial Least Squares (PLS), using a large data set with the main soil parameters. The two approaches were tested and compared for 30 soils in Spain. Correlations between the predicted and experimental values of K_d(Sr) obtained using hard- and soft-modelling showed slopes close to 1 and regression coefficients higher than 0.95, which confirms that both approaches are able to obtain satisfactory estimates for K_d(Sr) from soil parameters.     

空气质量监测系统中浓度换算及相关校准问题的探讨

目前在城市空气质量自动监测系统中,多数使用美国进口仪器由于我国规定的空气质量标准状态与美国规定不同,带来了两国在空气质量监测结果表达上的差异,这种差异表现在污染物浓度的两种表示方法的换算上。对此问题及相关的仪器校准方法进行了讨论,提出了解决方法。     

浅谈总量监测审验

总结了总量监测存在的问题,提出必须加强对总量监测的审验,阐述了总量监测审验的主要内容和操作。     

关于通风消声器评价指标的讨论

介绍了通风消声器的评价指标,对检测数据和检测方法进行了分析,讨论了评价插入损失、阻力系数和再生噪声过程中存在的问题,提出了改进建议,以提高各实验室检测数据的实用性和可比性。     

高速公路汽车防碰撞模型仿真研究

随着高速公路的快速建设,交通事故迅猛增长.保证适当的车辆行驶距离是预防高速公路事故的有效手段.论文根据车辆制动规律和运行状态,得出行车安全距离模型,同时对模型中的参数进行了说明和分析.采用MATLAB软件对高速公路车辆的安全距离模型进行仿真分析,得出安全距离随车速和附着系数的变化规律,寻求既保证车辆安全行驶又不影响道路通行能力的合理的安全距离值,为降低高速事故率提供一定的依据.     

室内窗帘竖直火蔓延特性全尺寸实验研究

窗帘的安装方式对其燃烧特性有重要影响.基于9705全尺寸热释放速率实验平台,针对三种不同材质的典型窗帘试样,进行了全尺寸火灾实验.测量了试样在不同褶皱程度下的火蔓延速率、热释放速率、产生烟气的比消光系数等火灾参数,分析比较其相互关系,实验结果可为室内火灾动力学发展的数值模拟和火灾安全设计提供支撑与指导.     

Quantifying the transfer of radionuclides to food products from domestic farm animals

Databases have been compiled to derive parameter values relevant to the transfer of radionuclides from feedstuffs to domestic animal products to provide a revision to the IAEA Handbook on transfer parameters TRS 364. Significant new data inputs have been incorporated into the databases from an extensive review of Russian language information and inclusion of data published since the early 1990s. Fractional gastrointestinal absorption in adult ruminants presented in the revised handbook are generally similar to those recommended for adult humans by the ICRP. Transfer coefficient values are presented in the handbook for a range of radionuclides to farm animal products. For most animal products, transfer coefficient values for elements additional to those in TRS 364 are provided although many data gaps remain. Transfer coefficients generally vary between species with larger species having lower values than smaller species. It has been suggested that the difference is partly due to the inclusion of dietary dry matter intake in the estimation of transfer coefficient and that whilst dietary intake increases with size nutrient concentrations do not. An alternative approach to quantifying transfer by using concentration ratios (CR), which do not consider dietary intake, has been evaluated. CR values compiled for the handbook vary considerably less between species than transfer coefficient values. The advantage of the CR approach is that values derived for one species could be applied to species for which there are no data. However, transfer coefficients will continue to be used as few studies currently report CR values or give data from which they can be estimated.     

New best estimates for radionuclide solid–liquid distribution coefficients in soils. Part 2. Naturally occurring radionuclides

Predicting the transfer of radionuclides in the environment for normal release, accidental, disposal or remediation scenarios in order to assess exposure requires the availability of an important number of generic parameter values. One of the key parameters in environmental assessment is the solid liquid distribution coefficient, K_d, which is used to predict radionuclide–soil interaction and subsequent radionuclide transport in the soil column. This article presents a review of K_d values for uranium, radium, lead, polonium and thorium based on an extensive literature survey, including recent publications. The K_d estimates were presented per soil groups defined by their texture and organic matter content (Sand, Loam, Clay and Organic), although the texture class seemed not to significantly affect K_d. Where relevant, other K_d classification systems are proposed and correlations with soil parameters are highlighted. The K_d values obtained in this compilation are compared with earlier review data.     

我国能源消费需求的时变弹性分析

为了科学分析相关经济因素变化对我国能源需求的影响效应,本文在提取能源消费需求主要影响因素的基础上,建立了基于Bayesian理论的时变系数回归模型,利用MCMC方法获得了各时变回归系数的估计.同时,利用HP滤波方法,得到了能源消费需求相对于各相关因素弹性系数的趋势及波动情况,并就能源需求对各相关经济因素弹性系数的趋势变动原因进行了分析,结果表明:①在不同的时间段内,能源价格、产业结构、经济增长、全国总人口以及能源消耗结构对能源消费需求的影响强度具有时变效应;②电力价格变动对降低能源消费的作用最为显著,但边际效应在逐年下降;煤炭价格的提高对能源消费的增加具有很大推进作用,但"煤电联动"、能源价格市场化的建设可能进一步抑制能源需求;③城镇化建设进程可进一步优化人口结构、产业结构以及能源消费结构,这将在很大程度上限制能源需求的加速增长.