Sediment nutrient flux in a coastal lake impacted by diverted Mississippi River water

The internal nutrient load from bottom sediment to the water column of a Louisiana Barataria Basin lake (Lake Cataouatche) receiving diverted Mississippi River water was determined. Dissolved reactive phosphorus (DRP), ammonium (NH₄-N) and nitrate (NO₃-N) flux from sediment to water column were measured. The DRP flux averaged-0.22 mg m^-2 d^-1 under aerobic water column conditions, as compared with that 3.29 mg m^-2 d^-1 under anaerobic conditions. The average NH₄-N released under anaerobic conditions (1.42 mg m^-2 d^-1) was significantly greater than rates under aerobic conditions (-0.02 mg m^-2 d^-1), indicating a strong relationship between nutrient flux and oxygen availability in the water column. The average NO₃-N flux was 2.13 mg m^-2 d^-1 under aerobic conditions as compared with-0.24 mg m^-2 d^-1 under anaerobic conditions in the sediment-water column. When the water column maintained under anaerobic conditions was switched to aerobic conditions, the DRP, NH₄-N, and NO₃-N concentrations in overlying water decreased rapidly over a short period of time. The mean annual internal DRP and NH₄-N load from the sediment to the overlying water was estimated to be 69.26 and 29.9 tonnes (Mg) yr^-1 respectively, which represents a significant portion of the total nutrient load to the Lake. Results demonstrate that the internal flux of nutrients from sediments can contribute a significant portion of the total nutrient load to the water column and should be considered in decisions on impact of nutrient in diverted Mississippi River on water quality of Barataria Basin.     

A mathematical model to estimate errors associated with closed flux chambers

Errors associated with the closed flux chamber technique, used to measure surface emissions from landfills, were investigated by using a combination of numerical modeling and laboratory studies. A transient-state, advective–dispersive–reactive model was developed and used in conjunction with its steady-state version to quantify the errors associated with closed flux chambers. In developing the model, all four major gases, CH₄, O₂, CO₂, and N₂, and the oxidation of CH₄ to CO₂ were considered. Laboratory experiments were conducted on a monolayered as well as a two-layered landfill cover system to calibrate and verify the model. The model was used to develop a plot of the percentage errors associated with closed flux chambers of different dimensions and surface flux rates.     

高炉洗气含氰废水除氰方法研究—气化分离与富集

本文用ＣＯ２气体气体化分离含氰废水中的氰，用乙醛等醛类吸收富集挥发出来的氰化氢而使氰以回收利用。气化分离除氰后，水中残余氰的浓度小于０．５ｐｐｍ。对醛类与ＨＣＮ反应的动力学和热力学性质的研究和吸收试验表明，乙醛等低分子醛能快速和完全地吸收气化分离出的ＨＣＮ，并得到α－羟基腈、羟基酸及其盐等系列产品。     

消化/剩余污泥水分扩散通量的研究

在传递理论的基础上,研究了干燥温度、污泥厚度及其种类3个主要因素对污泥水分扩散的影响,干燥温度设为30℃、40℃和50℃,污泥厚度设为1.3 cm、2.6 cm和3.9 cm,分别考察了消化和剩余两种污泥的干燥性能。利用实验数据获得两种污泥的有效质扩散系数,采用因次分析法建立了它们的水分扩散通量的准则关系式,通过实验研究两种污泥的水分扩散通量随干基含湿量的变化规律,并获得了两种污泥的水分扩散通量的经验公式。实验结果显示3.9 cm厚的消化污泥在40℃条件下的干燥效果最好。     

流速仪法测定废水流量有关问题的探讨

对流速仪法的测量要求、点位选择、测速垂线的布设及影响因素、如何消除测量中由于人为因素造成的系统误差、提高测量结果的准确度等问题进行了分析探讨。     

漏磁探伤设备在油田油管杆修复检测中的应用

介绍了漏磁探伤设备在孤东采油厂管、杆修复检测中的应用现状,针对探伤检测中存在的问题,提出了相应的对策,提高了探伤检测效果。     

低热通量条件下消防员防护服装热防护性能的测试

本文讨论了低热通量条件下消防员防护服装热防护性能的测试原理和测试步骤。通过测试。分析了低热通量条件下消防员防护服装热防护性能的各种影响因素。     

燃油流量对防火试验火焰特征的影响

为了研究燃油流量对防火试验火焰特征的影响,为防火试验方案的设计提供参考和指导,采用Ansys Fluent软件对NexGen燃烧器进行三维定常数值模拟,分析了不同燃油流量条件下的火焰特征。结果表明:燃油流量对火焰最高温度和火焰形状几乎没有影响,但对火焰长度、监测面上温度分布、7个测量点的平均温度和热流密度有很大影响,通过分析各燃油流量条件下的火焰特征,发现当空气流量为35.8 g/s时,燃油流量在2.0~2.11 g/s——即余气系数为1.15~1.22时,能够用于防火试验。     

A Relaxed Eddy Accumulation System for the Automated Measurement of Atmospheric Ammonia Fluxes

A continuous relaxed eddy accumulation system ispresented for the automated measurement of surface/atmosphere exchange fluxes of atmospheric ammonia (NH₃) at a single height. The new system features sampling by parallel plate denuder inlets, online chemical analysis using the conductivity cell of a commercially available NH₃ analyzer and online flux calculation. The effective detection limit of the system for air concentrations is 0.2 g m^-3 and it is estimated to resolve fluxes > ± 20 ng m^-2 s^-1, depending on the NH₃ concentration and turbulence. The performance of the system was tested in two measurement campaigns above agricultural grassland, in which it was compared with a 3-point continuous gradient system. During the first campaign, after urea application of 47 kg N ha^-1 in autumn, the REA system derived fluxes which were on average twice as large as the gradient fluxes, while concentrations agreed closely (on average within 4%). Possible reasons include differences in the footprint and an over-correction of the gradient flux in stable conditions. Due to wet and cold conditions, only 0.3% of the fertilizer N was volatilized as NH₃ during the first week. Results from the deployment of an improved system are presented for a summer day, 6 days after fertilization with calcium ammonium nitrate. The agreement of both concentrations (on average within 13%) and fluxes (26%) was very encouraging and similar to the agreement found between two state-of-the-art gradient systems with online analysis.