Degradation of volatile chlorinated aliphatic priority pollutants in groundwater

The known degradation products and degradative pathways involving selected volatile aliphatic chlorinated hydrocarbons in soil-groundwater systems are summarized. Current data indicate that the most commonly found products of microbial degradation of these compounds come from reductive dehalogenation, while nonmicrobial degradations tend to involve hydrolysis and/or oxidation. However, conclusions must be regarded as tentative, since most of the available studies have involved model systems and extrapolations, rather than direct studies of compounds in groundwater systems. Other potentially complicating factors, such as mobility and volatilization, are mentioned. Current knowledge is discussed in the context of data that would be desirable to obtain in future studies.     

Study of total organic halogen as a means to detect groundwater contamination

Total organic halogen (TOX) was evaluated as a means to detect contamination of groundwater by halogenated organics. Groundwater samples from monitoring wells at 10 Canadian landfill sites were analyzed for carbon adsorbable TOX, total organic carbon and volatile organics. Low concentrations of TOX (range, ND-44; median 8 μg Cl L^?1) were found at nine sites, and elevated TOX levels (?2072 μg Cl L^?1) at the tenth site. This latter site was studied in greater detail, and TOX and GC-MS analyses were carried out for volatile, base neutral, and acid extractable fractions of the water in six monitoring wells at this site. The TOX and GC-MS techniques were found to provide complementary information. GC-MS analysis detected high concentrations of 1,2-dichloroethylene, trichloroethylene, toluene, and ethylbenzene in some of the wells. TOX measurements, however, indicated the presence of halogenated contaminants in the base-neutral and acid extractable fractions, which had not been detected by GC-MS.     

灵活就业人员参加失业保险问题的探讨

随着灵活就业人员的大量出现，他们的社会保障问题已经成为一个新的社会问题。而现行失业保险政策并不适应灵活就业多样化的特点和多层次的需要，灵活就业人员没有被纳入失业保险覆盖范围，因此设计一套更能适应当前形势的合理的、高效的社会保障措施已经迫在眉睫。     

中小型电厂脱硫改造工程应考虑的几个问题

中小型电厂脱硫改造工程过程中应考虑的诸如场地的约束、脱硫对锅炉引风系统阻力的影响、脱硫对除尘器影响、脱硫对设备运行腐蚀及脱硫副产品的处理等问题及解决方案.     

西藏尼洋河区域宜垦荒地资源开发研究

尼洋河区域在藏东南社会、经济总格局中占有极为重要的中心地位,是西藏自治区重点开发区域之一。针对区域宜垦荒地资源总量较大、总体质量较高、开发难度较低的突出特点,并结合农村经济薄弱、资源严重闲置等实际,提出了宜垦荒地资源开发原则、开发构想和以商品畜牧业及果品业为主的开发方向。     

Modelling collective foraging by means of individual behaviour rules in honey-bees

An individual-oriented model is constructed which simulates the collective foraging behaviour of a colony of honey-bees, Apis mellifera. Each bee follows the same set of behavioural rules. Each rule consists of a set of conditions followed by the behavioural act to be performed if the conditions are fulfilled. The set of conditions comprises the state of external information available to the bee (e.g. the dancing of other bees) and internal information variables (like memorised location of a food source and homing motivation). The rules are partly observational (i.e. they capture the observable regularities between the present external information and the individual bee's behaviour), and partly involve hypothesised internal-state variables (e.g. abandoning tendency and homing motivation), because no observable (physiological) aspect has as yet been detected in the bee which correlates with changes in the internal motivation. Our aim is to obtain a set of rules that is necessary and sufficient for the generation of the collective foraging behaviour observed in real bees. We simulated an experiment performed by Seeley et al. in which a colony of honey-bees chooses between two nectar sources of different profitabilities which are switched at intervals. A good fit between observed and simulated collective forager patterns was obtained when the model included rules in which the bees (1) relied on the information acquired from previous flights to a source (e.g. profitability and time of day when the source was found), (2) used positional information obtained by attending recruitment dances and (3) did not abandon a (temporarily) deteriorated source too fast or too slowly. The significance of the following issues is discussed: the role of internal and external information, source profitability, the spatial precision of the dance communication, the ability to search for a source after the source position has been transmitted, the tendency to abandon a deteriorated source, and the concepts of scout, recruit, (un)employed forager, and foraging history. Received: 26 January 1998 / Accepted after revision: 16 May 1998     

Evaluation of solid sorbents for sampling aliphatic and aromatic nitro compounds in work-room air

Amberlite XAD-2 and XAD-7 porous polymers were evaluated for the solid sampling of aliphatic and aromatic nitro compounds in work-room air. With the use of solvent desorption, XAD-2 gave 80–100% recovery of nitroaromatics, and XAD-7 85–100% recovery of nitroaliphatics. The compounds studied were nitromethane, nitroethane, 2-nitropropane, nitrobenzene, $\text{m}$-dinitrobenzene and 2,4,6-trinitrotoluene. All six compounds gave very poor recoveries from activated charcoal.     

Acid deposition and watershed characteristics in relation to lake chemistry in northeastern Minnesota

The relationship between lake sensitivity to atmospheric acidic inputs and the neutralization capacity of watersheds is examined for 267 lakes in northeastern Minnesota. Three water chemistry/sensitivity measures (color, sulfate, and alkalinity) are correlated with variables representative of precipitation and sulfate inputs, hydrology, and the acid neutralization capacity of various watershed components. An ordinal scale for ranking bedrock and surficial deposit neutralization capacity is presented. The watershed variables found to account for the largest percentages of the variability in measured color, sulfate, and alkalinity levels are determined. Color is strongly related to the presence of peat or marsh and hydrologic renewal time, whereas sulfate is primarily related to atmospheric deposition, evaporative concentration, bedrock type, and the presence of coniferous forest. Variation in alkalinity is the most difficult of the water chemistry measures to explain; for headwater lakes, atmospheric sulfate input, water renewal time, the presence of deciduous forest, and the weatherability of underlying bedrock determine much of its variability. The results illustrate important averaging properties of watersheds from small headwater systems to large drainages and the difficulty in obtaining correlations for some water quality measures (e.g., alkalinity) when some variables, such as soils and land cover, are available only as large-area averages.     

深入调查研究 把握主要矛盾 努力开创防震减灾工作新局面

在“九五”期间 ,江苏省地震局深入调查研究 ,把握主要矛盾 ,深化各项改革 ,狠抓实事实办 ,强化政府行政职能 ,加强宣传力度 ,加强地方地震机构建设 ,注重规划和计划的制订与实施 ,不断理顺拨款渠道 ,健全地方财政对地震事业投入的预算体制 ,健全行政规章、规范管理行为 ,加强法规建设、强化法制管理。经努力 ,各项工作取得了明显成效 ,1 996～ 1 999年 ,全局各类经费总来源为前 4年的 3 1倍 ;地震监测系统的数字化、通讯系统的计算机网络化、分析预报系统的应急决策指挥系统现代化建设取得明显进展。地震监测预报工作为保障全省经济建设顺利进行 ,维护社会稳定作出重要贡献。全局职工的住房得到明显改善 ,4年中在宁职工人均增加住房面积约 2 0m2 。人均总收入也较从前有大幅度提高。新建园艺绿地面积约 4 0 0 0m2 。工作体会主要是 ,领导班子同心协力是搞好工作的关键 ,广大职工的积极性是搞好工作的基础 ,各级领导坚持“两手抓”是搞好工作的根本 ,领导干部始终不懈地讲学习、讲政治、讲正气是搞好工作的前提