Exponential Collapse of Benthic Depurative Capacity in A Eutrophic Tropical Marine Ecosystem: A Threshold Response to Organic Nitrogen Loading

Microbial decomposition of particulate organic matter in sediments can substantially modulate eutrophication of nearshore marine environments. Flux budgets for nitrogen compounds and quantification of rates of microbial transformation can provide important information on the process of eutrophication. This survey documents sediment nitrogen budgets for a eutrophic nearshore marine environment at La Parguera on southwest coast of Puerto Rico, including consideration of the organic fraction in addition to microbial transformations.

Sediments of the inshore channel at La Parguera denote the input of heavy organic loads with low redox potentials and high ammonium contents. Benthic fluxes of dissolved organic nitrogen are below those recorded for ammonium. These observations suggest that nearshore tropical sediments subject to heavy nitrogen loads act as a sink for organic nitrogen and that ammonification is a key process in the release of nitrogen from sediments to the water column. Nitrification and denitrification rates are low overall and inversely related to the redox potential. Depuration of excess nitrogen through denitrification is ineffective in these sediments. in contrast to more robust temperate environments, our work demonstrates that tropical marine systems are particularly susceptible to eutrophication given their limited capacity for depuration of excess nitrogen.     

Metal speciation in sediments of polluted and non‐polluted lakes

A five‐step extraction procedure for metal speciation studies (copper, lead, nickel, manganese and zinc) was applied to the analysis of lake sediments characterised by different environmental features. A different partition of metals into the several metal forms was observed. Both the metal fraction sorbed or co‐precipitated on hydrous Mn‐oxides (especially lead and zinc) and that bound to organic matter (especially copper) are high in some samples. A prevalently anthropogenic origin of these metals may be hypothesised on the basis of existing knowledge of the equilibrium and change phenomena occurring among water, particulate and sediments. Conversely, the non‐solubilised forms of metals are abundant in the sediments of lakes that are certainly not polluted. The concentration of manganese is very high in the sediments of Antarctic lakes; sequential extractions show its lithogenic origin. In conclusion, a knowledge of the different types of metal associations in sediments and their percentage can facilitate understanding of both natural and anthropogenic metal enrichment of aquatic systems.     

有机肥施用对珠三角菜地土壤磷污染风险的初步研究

通过田间小区试验研究有机肥施用量对菜心产量、土壤磷形态的影响,分析土壤磷形态之间的相关性,评估菜地红壤磷污染风险。结果表明,有机肥施用并未提高菜心的产量和生物量,而超过一定使用量之后,反而降低菜心产量和生物量;土壤无机磷形态以Fe-P和Al-P为主,占土壤无机磷质量分数的90%以上。有机肥施用提高土壤各形态无机磷的质量分数,且有机肥用量越高,土壤Fe-P、Al-P、Ca-P和O-P质量分数越高。有机肥过量施用显著提高土壤速效磷和水溶性磷质量分数;分别对Olsen-P和CaCl2-P与各形态磷进行逐步回归分析,只有Olsen-P和CaCl2-P与Ca-P具有线性关系（p〈0.05）,方程为Y1=36.95＋0.622 1X,Y2=-0.102 5＋0.048 6X。表明施用有机肥下,Ca-P是菜地土壤有效磷的最直接来源,可以作为红壤磷污染风险评价指标。     

A meta‐analysis of the interrelationships between employee lateness,absenteeism, and turnover: Implications for models of withdrawal behavior

We meta‐analyzed the correlations between voluntary employee lateness, absenteeism, and turnover to (i) provide the most comprehensive estimates to date of the interrelationships between these withdrawal behaviors; (ii) test the viability of a withdrawal construct; and (iii) evaluate the evidence for competing models of the relationships between withdrawal behaviors (i.e., alternate forms, compensatory forms, independent forms, progression of withdrawal, and spillover model). Corrected correlations were .26 between lateness and absenteeism, .25 between absenteeism and turnover, and .01 between lateness and turnover. These correlations were even smaller in recent studies that had been carried out since the previous meta‐analyses of these relationships 15–20 years ago. The small‐to‐moderate intercorrelations are not supportive of a withdrawal construct that includes lateness, absenteeism, and turnover. These intercorrelations also rule out many of the competing models of the relationships between withdrawal behaviors, as many of the models assume all relationships will be positive, null, or negative. On the basis of path analyses using meta‐analytic data, the progression of withdrawal model garnered the most support. This suggests that lateness may moderately predict absenteeism and absenteeism may moderately predict turnover. Copyright © 2011 John Wiley & Sons, Ltd.     

液相有机热载体锅炉安装监检中常见的问题

对液相有机热载体锅炉安装监检中常见问题进行了分析,并有针对性地提出了相应的解决办法。     

基于可拓层次分析法的铁矿危险性评价研究

我国铁矿伤亡事故后果比较严重,重特大事故时有发生。基于可拓层次分析法(EAHP),结合可拓工程方法,在物元模型理论的基础上建立了铁矿危险性评价的物元模型,聘请5位专家对铁矿危险性的评价指标体系的10项指标进行评价,利用层次分析法确定各评价指标的权重,并对大红山铁矿的危险性进行评价,得出危险性等级为危险性较小、安全性较好,也说明了该铁矿需要进一步采取安全措施,加强安全管理,提高其安全程度,从而避免事故的发生,该方法为铁矿危险性评价提供了一条新的方法和手段。     

膜-生物反应器中溶解性有机物的三维荧光分析

采用三维荧光技术研究了膜-生物反应器(MBR)处理生活污水过程及膜污染物中溶解性有机物(DOM)的变化,并与传统的厌氧/缺氧/好氧(AAO)活性污泥工艺进行了对比.结果表明,生活污水DOM中主要的荧光物质有类蛋白质(荧光峰A和B)及类腐殖质(荧光峰C),经MBR处理后,荧光峰的强度降低了16%~35%,同时类蛋白质的结构也发生了变化.与好氧段滤液相比,溶解性膜污染物中类腐殖质含量较低,主要的荧光物质为分子量较小、共轭性较弱的类蛋白质.AAO工艺中厌氧段加强了对荧光峰A和C的去除,处理过程中类蛋白质结构的变化与MBR工艺有显著不同.     

硝酸改性活性炭对渗滤液中小分子有机物的吸附性能

以硝酸为改性剂,分别采用浸渍和浸渍-高温热处理方法对活性炭进行了改性.低温氮吸附结果表明,活性炭表面积和微孔体积在浸渍后都变小,再经过高温热处理后则都变大.酸碱滴定显示,改性后活性炭表面酸性都增大,其中浸渍的酸性最大.对填埋场渗滤液中小分子有机物进行了等温线和动力学吸附实验,结果发现改性后活性炭对有机物的吸附量增加;硝酸浸渍活性炭吸附速率降低,而浸渍-高温热处理则使吸附速率明显加快.针对渗滤液中小分子有机物,硝酸浸渍-高温热处理的活性炭吸附效果最好,吸附量最大,吸附速率最快.     

A physical-microbial food web coupled model to study the evolution of the ecological functioning of a new reservoir after its flooding (Sep,Puy de Dôme)

The aim of this paper is to understand the temporal changes in planktonic populations and to highlight some important factors that control the biological functioning and evolution of a recently flooded reservoir, the Sep reservoir (Massif Central, France). To achieve this objective, a 1D vertical coupled physical–biological model was used and developed. It couples relevant physical processes (dispersion, advection and convection) with biological processes taking into account the complexity of interactions within the microbial food web, including the conventional grazing food chain with a microbial loop.