A TREATISE ON THE USE OF EXPECTED VALUES IN WATER RESOURCE PROJECT EVALUATION1

This paper focuses on two factors that influence the acceptability of the expected value criterion as a method of handling risk or uncertainty in decision-making where damages from unusual physical occurrences such as hurricanes or floods must be considered. These are the length of time of project existence and the problem of obtaining accurate estimates of the probability of occurrence for different sizes of natural disasters. The problem of estimating accurate probabilities of occurrence for different sizes of natural disasters is not as great as it might appear and in most situations will not defeat the usefulness of the method. The time span during which the project is expected to exist has greater implications for the usefulness of the expected value approach appears highly applicable. However, it becomes less applicable for projects that are short-term in nature. The basis for distinguishing between short- and long-term projects is presented.     

引信在长期贮存下老化行为的仿真模拟与分析

目的 厘清某型引信在贮存14 a后的失效模式,研究温度周期性交变对引信及其薄弱零件的影响。方法利用ANSYS workbench软件,建立基于时间硬化的蠕变仿真方法。以某型引信为研究对象,开展周期性温度交变的蠕变仿真,根据仿真计算结果和实物的对比分析,找出薄弱零件,分析其老化失效模式。结果 在每个周期内环境温度循环条件下,仿真时长设定为14 a,结果显示,引信整体蠕变应变率超过1%,平均压紧应力下降21%,松弛稳定性变弱,密封性在一定程度上变差。其中,引信电机外壳、电机扇叶、底部线路对接板为薄弱零件,容易发生失效行为。结论 引信贮存在典型西南湿热环境14 a后,周期性温度交变应力将导致引信出现缺陷,缺陷集中在电机外壳、电机扇叶、底部线路对接板处,应重点对这些部位进行防护。     

Assessment of the Usefulness of Semipermeable Membrane Devices for Long-Term Watershed Monitoring in an Urban Slough System

Semipermeable membrane devices (SPMDs) were deployed at eight sites within the Buffalo Slough, near Portland, Oregon, to (1) measure the spatial and seasonal distribution of dissolved polycyclic aromatic hydrocarbon (PAH) and organochlorine (OC) compounds in the slough, (2) assess the usefulness of SPMDs as a tool for investigating and monitoring hydrophobic compounds throughout the Columbia Slough system, and (3) evaluate the utility of SPMDs as a tool for measuring the long-term effects of watershed improvement activities. Data from the SPMDs revealed clear spatial and seasonal differences in water quality within the slough and indicate that for hydrophobic compounds, this time-integrated passive-sampling technique is a useful tool for long-term watershed monitoring. In addition, the data suggest that a spiking rate of 2–5 μg/SPMD of permeability/performance reference compounds, including at least one compound that is not susceptible to photodegradation, may be optimum for the conditions encountered here.     

Environmental bonds and the challenge of long-term carbon sequestration

The potential to capture carbon from industrial sources and dispose of it for the long-term, known as carbon capture and sequestration (CCS), is widely recognized as an important option to reduce atmospheric carbon dioxide emissions. Specifically, CCS has the potential to provide emissions cuts sufficient to stabilize greenhouse gas levels, while still allowing for the continued use of fossil fuels. In addition, CCS is both technologically-feasible and commercially viable compared with alternatives with the same emissions profile. Although the concept appears to be solid from a technical perspective, initial public perceptions of the technology are uncertain. Moreover, little attention has been paid to developing an understanding of the social and political institutional infrastructure necessary to implement CCS projects. In this paper we explore a particularly dicey issue--how to ensure adequate long-term monitoring and maintenance of the carbon sequestration sites. Bonding mechanisms have been suggested as a potential mechanism to reduce these problems (where bonding refers to financial instruments used to ensure regulatory or contractual commitments). Such mechanisms have been successfully applied in a number of settings (e.g., to ensure court appearances, completion of construction projects, and payment of taxes). The paper examines the use of bonding to address environmental problems and looks at its possible application to nascent CCS projects. We also present evidence on the use of bonding for other projects involving deep underground injection of materials for the purpose of long-term storage or disposal.     

长期定位施肥田土壤酶活性的动态变化特征

为探讨长期施肥条件下玉米生育期内土壤酶活性的动态变化及其与土壤肥力的关系,该文对北京褐潮土定位试验田第12年的土壤酶以及土壤养分因子进行了测定和分析.结果表明.土壤过氧化氢酶、磷酸酶在玉米拔节期出现活性高峰.土壤脲酶在玉米拔节期及成熟期出现两个活性高峰,土壤蔗糖酶在整个玉米生育期内活性变化幅度较小.长期施肥能明显提高土壤中蔗糖酶、脲酶、磷酸酶活性,其中有机肥与化肥配施对于增加土壤中蔗糖酶、脲酶、磷酸酶活性尤为显著.长期施肥降低土壤中过氧化氢酶活性.并且以NPK配施有机肥处理的土壤过氧化氢酶活性降低幅度最大.土壤酶之问及其与土壤养分因子之间具有明显相关性,其中蔗糖酶、脲酶及磷酸酶与土壤养分各因子均呈显著或极显著正相关,除碱解氮外,过氧化氢酶与其余各养分因子呈显著或极显著负相关.     

Observed levels and trends of gaseous SO2 and HNO3 at Mt. Waliguan, China: Results from 1997 to 2009

Long-term measurements of SO2 and HNO3,particularly those from the background sites,are rarely reported.We present for the first time the long-term measurements of SO2 and HNO3 at Waliguan(WLG),the only global baseline station in the back-land of the Eurasian Continent.The concentrations of SO2 and HNO3 were observed at WLG from 1997 to 2009.The observed annual mean concentrations of SO2 and HNO3 at WLG were 1.28±0.41 and 0.22±0.19μg/m3,respectively.The HNO3 concentrations were much higher in warmer seasons than in colder seasons,while the SO2 concentrations showed a nearly reversed seasonal pattern.In most months,the concentration of HNO3 was significantly correlated with that of SO2,suggesting that some common factors influence the variations of both gases and the precursors of HNO3 may partially be from the SO2-emitting sources.The SO2 concentration had a very significant(P < 0.0001) decreasing trend(-0.2μg/(m3·yr)) in 1997-2002,but a significant(P < 0.05) increasing trend(+0.06 μg/(m 3 ·yr)) in 2003-2009.The HNO3 concentration showed no statistically significant trend during 1997-2009.While the decrease of SO2 in 1997-2002 agrees with the trend of global SO2 emissions,the increase in 2003-2009 is not consistent with the decreasing trends in many other regions over the world.Trajectory analysis suggests that the airmasses from the northern Qinghai-Tibetan Plateau and the Takla Makan Desert regions contributed significantly to the increasing trends of SO2 and HNO3 at WLG in 2003-2009,with a rate of +0.13μg/(m3·yr) and +0.007μg/(m3·yr),respectively.     

构建农村环境保护长效机制探讨

构建长效机制保护农村环境,是一项庞大而复杂的系统工程,强有力的推进措施是实施这一工程的重要保证。结合农村环境实际状况及环保工作实践,提出推进措施的关键是宣传到位形成共识,问责到住形成合力,投入到位形成平台。并进一步提出宣传的重点是要持续提升农村居民的环保意识,持续凝结农村各界的环保行动共识;问责的重点是要加强政府规划引领,分解落实可考核责任;投入的重点是要多渠道增加经费供给,克服农村环保资金瓶颈;提高科技支撑力度,以科技促环保：     

平衡施肥与秸秆覆盖对紫色土坡耕地养分及其化学计量的影响

为探究长期平衡施肥和秸秆覆盖对紫色土坡耕地土壤养分及其化学计量比的影响,以垫江县长期农田氮磷流失监测点为研究样地,设置3个处理：常规模式（CK）、平衡施肥模式（M1）和平衡施肥+秸秆覆盖模式（M2）,每个处理各设3个重复,共建立9个小区（长7 m×宽3 m）,并于2018、2019和2020年采集土样,研究不同处理下碳（C）、氮（N）、磷（P）和钾（K）含量及其化学计量变化特征.结果表明,2018年不同处理之间K含量差异显著,大小顺序为：CK>M2>M1;2019年不同处理之间硝态氮（NO₃^--N）、铵态氮（NH₄⁺-N）含量差异显著,表现为：M1>M2>CK;其他养分含量在同一年份不同处理之间差异均不显著.不同年份间各处理的土壤C和N含量差异不显著.2018年各处理中K含量均显著高于其他年份,其中,2018年的CK、M1和M2分别比2019年和2020年高78.26%和98.79%,19.13%和35.4%,54.49%和41.76%.P含量在CK和M2处理中均随着年份增大而减小,且2018年分别比2019年高20.29%和10.67%,比2020年高39.68%和17.33%.各处理不同年份间速效钾（AK）含量无显著差异,而NO₃^--N和NH₄⁺-N和速效磷（AP）含量差异显著,且均在2020年最高.土壤C ：P、C ：K、N ：P、N ：K和P ：K在不同年份间都表现出显著差异（P<0.05）.土壤C ：K、N ：K和AN ：AP分别于2018年和2019年在不同施肥模式间差异显著（P<0.05）.土壤C与N及P与K之间呈显著的线性正相关;土壤C ：K与C ：P、N ：K、N ：P和P ：K之间,N ：K与C ：P、P ：K和N ：P之间,N ：P与C ：P之间都呈显著的线性正相关;土壤P与C ：K和N ：K之间呈显著的线性负相关.土壤NO₃^--N与NH₄⁺-N、AN ：AP和AN ：AK之间,NH₄⁺-N与AN ：AP和AN ：AK之间,AP与AK和AP ：AK之间,AN ：AP与AN ：AK之间都呈极显著正相关.研究发现平衡施肥+秸秆覆盖是紫色土坡耕地较为适宜的管理模式.     

长期冻融循环下固化铅锌镉复合重金属污染土抗剪强度及浸出特征研究

为了评估长期冻融循环后(最长90d (次))固化复合重金属污染土的的抗剪强度及浸出特征,采用水泥、生石灰和粉煤灰按比例混合的复合固化剂固化/稳定化铅锌镉复合重金属污染土进行三轴压缩试验及毒性特征浸出程序试验.结果表明,固化污染土体的内摩擦角仅在冻融循环3次内有明显增加,增加率高达96.3%;粘聚力在冻融循环30次内总体趋势不断下降,之后无显著变化,最终下降率达到54.23%;Pb²⁺、Zn²⁺、Cd²⁺浸出浓度与冻融循环次数呈正比;EC值与冻融循环次数在总体上正相关;长期冻融循环作用后浸出液的pH值降低.并通过扫描电子显微镜,进一步探究长期冻融循环下固化污染土抗剪强度及浸出特征的劣化机理,结果显示在冻融循环后期固化土体内生成了大量的延迟钙矾石,这些延迟钙矾石在形成过程中的膨胀作用是引起抗剪强度损失、重金属浸出浓度升高的主要原因.