Dynamics of phosphorus exchange between sediment and water in a gravel-bed river

ABSTRACT

Phosphorus (P) stores in gravel-bed rivers are released for uptake by periphyton when pH levels exceed 8.5. The Tukituki River has low alkalinity water and frequently experiences periphyton blooms, and daytime pH?>?9 during summer low-flows. We measured dissolved reactive P (DRP) and EPC₀, the water concentration of DRP at which no net release or sorption from the river bed occurs, in sediment samples from the Tukituki River subject to controlled pH levels before (2014) and after (2017) changes to two wastewater discharges that reduced P release to the river by 95%. DRP released from 2014 sediments at pH 8.5–10 were 30?±?10?mg/m³ above background (pH 8) whereas those released from 2017 sediments were 5?±?3?mg/m³ above background. EPC₀ levels in 2014 and 2017 were 11?±?6 and 7?±?2?mg/m³, respectively. Field estimates of released DRP calculated from continuous pH and the Redfield equation suggested that most of the readily available DRP released from sediments at elevated pH is derived from material attached to recently deposited sediment. Subsequently, a reduction in wastewater inputs or agricultural runoff should reduce sediment DRP stores, and hence sediment fluxes, within a few years and mitigate periphyton blooms in addition to directly lowering water column concentrations.     

Lethality of increasing CO2 levels on deep-sea copepods in the western North Pacific

The first CO₂ exposure experiments on several species of pelagic copepods inhabiting surface and deep layers in the western North Pacific were conducted. Living organisms were collected from two layers between the surface and 1,500 m between latitudes of 11 and 44°N, and they were exposed aboard ship to various pCO₂ up to about 98,000 μatm. Mortality of copepods from both shallow and deep layers in subarctic to subtropical regions increased with increasing pCO₂ and exposure time. Deep-living copepods showed higher tolerance to pCO₂ than shallow-living copepods. Furthermore, deep-living copepods from subarctic and transitional regions had higher tolerances than the subtropical copepods. The higher tolerances of the deep-living copepods from subarctic and transitional regions may be due to the adaptation to the natural pCO₂ conditions in the subarctic ocean.     

镁-锌合金成分的容量法测定

通过控制不同的pH值,采用EDTA容量法测定了镁-锌合金成分。结合标准加入法,对合金样品进行了测定,实验结果证实测定方法准确可靠。     

温度、光照和pH之间的相互关系对光合细菌生长的影响

我们于1996年3月至8月，在光合细菌培养期间，对光合细菌培养条件的最适温度、光照和pH进行较系统的研究与观察，发现了温度、光照和pH值同时影响着光合细菌的生长。而且温度、光照、pH值之间是相互制约的，温度与光照的强弱应是对立统一的。总结出光合细菌生长的最适条件应是互应的。经试验得出光合细菌生长的最适条件：（1）温度为15—20℃，光照度为30000—5000Lx，培养基pH为7．0。（2）温度为25—30℃时，光照为3000—500LX，其培养基pH为7．0。     

The uses of value

This paper proposes a new theory of value based on the observation of how people use this term. In everyday life the word value is commonly used to refer equally to what might be regarded as the incommensurable polarity between value as price, and value as priceless, sometimes portrayed as the contrast between value and values. My theory starts from trying to learn how people manage to use value as a means of bridging this divide. As such it opposes itself to ‘bottom-line’ theories of value. These range from vulgarised forms of Marx’s labour theory of value, to the way management consultants tried to impose a universal belief in shareholder value. An example is provided of how such bottom-line thinking undermined a UK government audit called best-value, and is also found in highly reductionist attempts to impose new-age values in management. By contrast, examples are given of how value is created in the process of bridging the divide between value and values, starting from the work of Zelizer and the case of concubines in 5th century BC Athens. Further examples range from the department store John Lewis to the Swedish social democratic state. Finally the application of this theory is considered in relation to a recent attempts to evaluate the impact of the mobile phone on low-income Jamaicans.     

泰山酸雨特征及影响因素分析

利用2006—2015年泰山气象站的降水pH、电导率、降水量和风向风速资料,统计分析了泰山酸雨特征和变化趋势,探讨了降水量和风向风速对酸雨的影响。结果表明,泰山降水年均pH变化范围为4.31～4.99,酸雨发生频率达到69.3%;pH随降水量的增加而趋于5.60（中性）;5月至次年1月的月均pH与月平均过程降水量的变化趋势一致;月均电导率与月平均过程降水量的变化趋势相反。泰山降水期间盛行西南风,在南风和东北风条件下,酸雨出现频率最高且酸性最强,这主要是风速风向因素和人为排放源分布共同导致的。近10 a泰山降水酸性程度有所减弱,酸雨频率明显下降,表明近年来酸雨污染情况有所改善,有利于保护泰山生态环境。     

用赢得值法进行测绘项目进度和费用控制

基于工程项目管理理论,主要探讨了用赢得值法进行测绘项目进度和费用控制的方法,对测绘工程项目进行有效管理,从而实现项目目标,提高项目管理水平。     

硫酸盐热化学还原作用的启动机制研究

硫酸盐热化学还原作用(TSR)是导致高含硫化氢天然气生成和聚集、碳酸岩盐储层酸化和溶蚀的重要因素,是地质盆地内烃-水-岩三者之间的复杂反应。本文利用黄金管热模拟实验,对TSR反应的可能启动机制及控制因素进行了研究。通过不同盐溶液与原油的热解实验,证实了硫酸盐的存在是启动TSR反应的必要因素,MgSO4比CaSO4和Na2SO4更容易启动TSR反应,体系中盐度的增加会加速H2S的生成。实验结果表明,不同水介质条件下,TSR反应的程度与溶液的离子强度呈正相关,弱酸性环境并不足以启动TSR反应;原油中不稳定含硫化合物的含量越高越有利于TSR反应的发生,饱和链烷烃比原油中其它组分更容易引发TSR反应,且大分子烷烃比小分子烷烃更容易被硫酸盐氧化。     

土壤pH值对土壤多环芳烃纵向迁移影响的模拟实验研究

影响土壤多环芳烃(PAHs)纵向迁移行为的环境因素很多。文章以氧化钙和冰乙酸改变采自徐州土壤的pH值水平,人工装填土柱进行纵向淋滤试验,研究pH值对土壤PAHs纵向迁移行为的影响。结果表明,土壤pH值的变化加强了PAHs在土柱中的纵向淋滤能力,表层土壤中的PAHs可迅速向底层转移;不同种类的PAHs淋滤特性表现不同,pH值增加更能增强低环PAHs的迁移淋滤能力,pH值降低则更能促进高环PAHs从土壤表层向深部迅速迁移。