碘量法测定溶解氧的取样技巧及改进方法

本文通过周密的设计和反复实验,分别从取样时间、取样位置和取样体积三方面进行了分析,并且从去离子水、地表水和污水进行对比实验数据中得出一个取样的最佳方案,从而对现有碘量法测定溶解氧的分析提出了修改意见。     

增强机组监控技能,确保飞行安全

良好的监控技能对确保飞行安全 ,预防飞行事故发生有十分重要的作用。但由于多方面原因 ,当前的飞行机组监控工作还存在不少问题 ,并成为多起飞行事故主要原因之一。笔者从四方面 ,对民用航空飞行中缺乏良好监控的原因予以分析和说明 :持续有效的监控工作不符合人的本性 ;现行规章制度中未把机组监控技能作为所有机组成员 ,尤其是对辅助操纵者的一项重要任务加以确定 ;现有管理制度与管理观念 ,更多关注行为结果而不是行为发生过程 ;飞行训练中未将其作为重要飞行技能加以训练。笔者强调指出 :采用标准操作程序 ,提高相应飞行阶段的监控技能 ,对不同飞行阶段的工作负荷予以计划和控制、进行工作优先排序 ,加强机组成员间配合 ,在训练中强化监控技能培养等措施 ,有助于改进和增强飞行机组的监控技能 ,确保飞行安全     

WATER QUALITY TRENDS IN LAKE TOHOPEKALIGA,FLORIDA, USA: RESPONSES TO WATERSHED MANAGEMENT1

ABSTRACT: Water quality in eutrophic Lake Tohopekaliga, Florida, improved markedly from 1982 to 1992 as a result of reductions in phosphorus and nitrogen loading to the lake. Annual budgets of water, chloride, phosphorus and nitrogen were constructed for the lake, and indicate it is a sink for phosphorus and a source for nitrogen. Water column concentrations of total phosphorus, soluble reactive phosphorus, total nitrogen, dissolved inorganic nitrogen, and chlorophyll a all declined as external inputs of nutrients decreased. Water column nitrogen: phosphorus ratios have increased, suggesting a probable shift from nitrogen- to phosphorus-limitation. This apparent shift in nutrient limitation status also is supported by comparisons of the mean Trophic State Indices for phosphorus, nitrogen, and chlorophyll a. These improvements in water quality are attributed to the diversion of wastewater treatment plant effluent from the lake, and the increased use of wet retention ponds for stormwater runoff.     

城市扬尘污染现状及防治对策

扬尘是造成城市颗粒物污染严重的主要因素.论述了城市扬尘污染的现状、主要来源及其危害,并针对各种扬尘污染源提出了具体的防治对策。     

沈阳市环境空气质量近10年变化趋势与污染控制对策

论述了近10年沈阳市环境空气质量变化趋势,对环境空气质量进行了空气综合污染指数评价和Spearman秩相关检验评价,并详细地阐明了环境空气污染与全市的能源结构、污染源排放状况和气候、气象条件等因素密切相关,提出解决环境空气污染的控制对策。     

Increasing nitrogen limitation in the Bothnian Sea,potentially caused by inflow of phosphate-rich water from the Baltic Proper

The study showed that the open water of the Bothnian Sea (BS) is likely to have shifted from altering nitrogen and phosphorous limitations of the spring bloom to more nitrogen-limited conditions during the last 20 years. This is affected by the by inflow of phosphate-rich and oxygen-depleted water from depths near the halocline in the northern Baltic Proper, where severe oxygen conditions currently cause extreme phosphate concentrations in the deep water. The change in relation between inorganic nitrogen and phosphorous in the BS occurs first in the deep water and then progresses to the surface water. The change can potentially cause increased production in the BS and more frequent cyanobacterial blooms. There does not appear to be any immediate concern in the short-term perspective for the state of the BS, but a progression of the processes may lead to a more eutrophic state of the BS.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0675-3) contains supplementary material, which is available to authorized users.     

Effects of Atmospheric Nitrogen Deposition on Remote Freshwater Ecosystems

We review known and hypothesized effects of nitrogen (N) deposition owing to human activities on the chemistry, organisms, and ecosystem processes of remote oligotrophic freshwaters. Acidification is the best-known effect of N deposition on water chemistry, but additional effects include increased nutrient availability and alteration of the balance between N and other nutrients. Our synthesis of the literature, framed in a comprehensive model for the effects of N deposition on natural ecosystems, shows that all these effects can reduce biological diversity and alter ecosystem processes in remote freshwaters. N deposition is projected to grow worldwide in the near future and will interact with other global changes. Present effects on these fragile ecosystems may be only early signs of more radical impacts ahead.     

Nutrient stoichiometry in Sphagnum along a nitrogen deposition gradient in highly polluted region of Central-East Europe

We investigated the variation of N:P and N:K ratio in ombrotrophic Sphagnum plants along a gradient of atmospheric N deposition from 1 to 2.5 g m⁻² year⁻¹ in Central-East Europe. The N:P and N:K ratio in Sphagnum capitula increased significantly along the N deposition gradient. Sphagnum species from the Cuspidata section were characterised by significantly lower ratios at low N deposition. When we compared the observed N:P ratios in Sphagnum plants with the values reported in a previous European-wide study, we found a correspondence in nutrient stoichiometry only for a few bogs: higher P concentration in Sphagnum capitula caused a lower N:P ratio in most of the study bogs so that Sphagnum plants still seem N-limited despite their N saturation. Interaction between summer water table decrease and aerial liming of surrounding forests is proposed as an explanation for this discrepancy. Local forestry practice interacting with climate thus alter N:P stoichiometry of Sphagnum along the N deposition gradient.     

The effect of dominance hierarchy on the use of alternative foraging tactics: a phenotype-limited producing-scrounging game

Group living is thought to be advantageous for animals, though it also creates opportunities for exploitation. Using food discovered by others can be described as a producer-scrounger, frequency-dependent game. In the game, scroungers (parasitic individuals) do better than producers (food finders) when scroungers are rare in the group, but they do worse when scroungers are common. When the individuals' payoffs do not depend on their phenotype (i.e. a symmetric game), this strong negative frequency dependence leads to a mixed stable solution where both alternatives obtain equal payoffs. Here, we address the question of how differences in social status in a dominance hierarchy influence the individuals' decision to play producer or scrounger in small foraging groups. We model explicitly the food intake rate of each individual in a dominance-structured foraging group, then calculate the Nash equilibrium for them. Our model predicts that only strong differences in competitive ability will influence the use of producing or scrounging tactics in small foraging groups; dominants will mainly play scrounger and subordinates will mostly use producer. Since the differences in competitive ability of different-ranking individuals likely depend on the economic defendability of food, our model provides a step towards the integration of social foraging and resource defence theories. Received: 30 July 1997 / Accepted after revision: 15 November 1997     

建材陶瓷中的放射性危害与防护

本文探讨当前城市房屋装修所用建筑陶瓷带来的放射性污染,阐述其危害原因,并提出针对建筑陶瓷放射性污染的有效防护措施。