Response of methane emission to invasion of Spartina alterniflora and exogenous N deposition in the coastal salt marsh

Spartina alterniflora exhibits great invading potential in the coastal marsh ecosystems. Also, nitrogen (N) deposition shows an apparent increase in the east of China. To evaluate CH₄ emissions in the coastal marsh as affected by the invasion of S. alterniflora and N deposition, we measured CH₄ emission from brackish marsh mesocosms vegetated with S. alterniflora and a native plant, Suaeda salsa, and fertilized with exogenous N at the rates of 0 and 2.7 g N m^?2, respectively. Dissolved porewater CH₄ concentration and redox potentials in soils as well as aboveground biomass and stem density of plants were also monitored. The averaged rate of CH₄ emission during the growing season in the S. alterniflora and S. salsa mesocosms without N application was 0.88 and 0.54 mg CH₄ m^?2 h^?1, respectively, suggesting that S. alterniflora plants significantly increased CH₄ emission mainly because of higher plant biomass rather than stem density compared to S. salsa, which delivered more substrates to the soil for methanogenesis. Exogenous N input dramatically stimulated CH₄ emission by 71.7% in the S. alterniflora mesocosm. This increase was attributable to enhancement in biomass and particularly stem density of S. alterniflora driven by N application, which transported greater photosynthesis products than oxygen into soils for CH₄ production and provided more pathways for CH₄ emission. In contrast, there was no significant effect of N fertilization on CH₄ emission in the S. salsa mesocosm. Although N fertilization significantly stimulated CH₄ production by increasing S. salsa biomass, no significant increase in stem density was observed. This fact, along with the low gas transport capacity of S. salsa, failed to efficiently transport CH₄ from wetlands into the atmosphere. Thus we argue that the stimulatory or inhibitory effect of N fertilization on CH₄ emission from wetlands might depend on the gas transport capacity of plants and their relative contribution to substrates for CH₄ production and oxygen for CH₄ oxidation in soil.     

Impact of permanent inundation on methane emissions from a Spartina alterniflora coastal salt marsh

To understand the effect of water level on CH₄ emissions from an invasive Spartina alterniflora coastal brackish marsh, we measured CH₄ emissions from intermittently and permanently (5 cm water depth) inundated mesocosms with or without N fertilizer added at a rate of 2.7 g N m^?2. Dissolved CH₄ concentrations in porewater and vertically-profiled sediment redox potential were measured, as were aboveground biomass and stem density of S. alterniflora. Mean CH₄ fluxes during the growing season in permanently inundated mesocosms without and with N fertilizer were 1.03 and 1.73 mg CH₄ m^?2 h^?1, respectively, which were significantly higher than in the intermittently inundated mesocosms. This response indicates that prolonged submergence of sediment, up to a water depth of 5 cm, stimulated CH₄ release. Inundation did not greatly affect aboveground biomass and stem density, but did significantly reduce redox potential in sediment, which in turn stimulated CH₄ production and increased the CH₄ concentration of porewater, resulting in higher CH₄ emission in the mesocosm. Our data showed that the stimulatory effect of shallow, permanent inundation on CH₄ emission in S. alterniflora marsh sediment was due primarily to an improved methanogenic environment rather than an increase in plant-derived substrates and/or the number of gas emission pathways through the plant’s aerenchymal system.     

高价铬及双酚A在铁-乳酸体系中的同时光处理

研究了Fe(Ⅲ)-乳酸配合物体系同时对Cr(Ⅵ)的光还原及双酚A(BPA)的光氧化处理,考察了光源、初始pH值、Fe(Ⅲ)、乳酸盐、Cr(Ⅵ)及BPA初始浓度等因素对Cr(Ⅵ)及BPA光处理效率的影响。结果表明:光照条件下,铁-乳酸配合物能有效实现对六价铬及BPA的同时光处理。同一体系中,Cr(Ⅵ)的光还原快于BPA的光氧化,Fe(Ⅲ)初始浓度的增加可同时提高Cr(Ⅵ)的光还原效率和BPA的光氧化效率;Fe(Ⅲ)-乳酸盐配合物光解产生的Fe(Ⅱ)是Cr(Ⅵ)的主要还原剂,其次级光反应中产生的.OH是BPA的氧化剂。     

微波强化氧化处理垃圾渗滤液工艺研究

考察了最优作用方式下单独微波、单独氧化剂以及两者的结合工艺对垃圾渗滤液的处理效果。单独微波工艺在功率为700 W,辐射10 min,COD、氨氮、磷和色度去除率分别为37.66%、96.14%、40%和80%,BOD5/COD由0.16增加到0.43。渗滤液先微波再氧化,氨氮去除率增加显著,节省了氧化剂用量。微波后渗滤液在pH=5,T=50℃,NaClO=24 mL/L时COD、氨氮、磷和色度去除率分别为98.63%、99.67%、97.25%和98%,BOD5/COD=0.8。总处理效率:微波-NaClO微波-Fenton微波-KMnO4微波-H2O2,微波-Fenton处理效率低于微波-NaClO主要取决微波后滤液中小表观分子质量增加导致氧化剂的混凝作用减弱,其次受反应后pH值变化的影响。     

板框压滤机内酒精污泥过滤脱水特性

采用螺杆泵输送和板框过滤机压滤的方法对酒精污泥进行机械脱水,研究了絮凝剂(聚丙烯酰胺PAM)添加量、污泥的进口湿含量、螺杆泵转速、过滤介质和过滤时间对污泥过滤特性的影响,并对滤饼吹气压榨进一步脱水。实验表明,在PAM添加量wPAM=3 kg/(t干污泥),污泥的进口湿含量x0=95%,螺杆泵转速n=180 r/min,过滤时间t=2.5 h并进行吹气压榨可将污泥的湿含量降至69.91%。     

A High‐Resolution National‐Scale Hydrologic Forecast System from a Global Ensemble Land Surface Model

Warning systems with the ability to predict floods several days in advance have the potential to benefit tens of millions of people. Accordingly, large‐scale streamflow prediction systems such as the Advanced Hydrologic Prediction Service or the Global Flood Awareness System are limited to coarse resolutions. This article presents a method for routing global runoff ensemble forecasts and global historical runoff generated by the European Centre for Medium‐Range Weather Forecasts model using the Routing Application for Parallel computatIon of Discharge to produce high spatial resolution 15‐day stream forecasts, approximate recurrence intervals, and warning points at locations where streamflow is predicted to exceed the recurrence interval thresholds. The processing method involves distributing the computations using computer clusters to facilitate processing of large watersheds with high‐density stream networks. In addition, the Streamflow Prediction Tool web application was developed for visualizing analyzed results at both the regional level and at the reach level of high‐density stream networks. The application formed part of the base hydrologic forecasting service available to the National Flood Interoperability Experiment and can potentially transform the nation's forecast ability by incorporating ensemble predictions at the nearly 2.7 million reaches of the National Hydrography Plus Version 2 Dataset into the national forecasting system.     

局部风机停运时空冷机组凝汽器性能试验研究

针对影响空冷凝汽器性能考核试验结果真实可靠性的相关因素,以德国VGB-R131 Me试验导则为基准,对大唐国际宁夏大坝发电有限责任公司600 MW直接空冷机组配套的SPX公司空冷凝汽器的性能考核试验结果进行分析,提出了在局部风机停运情况下试验的数据处理方法和修正方法,并就性能评价系数、设计风机消耗功率及真空系统严密性对试验结果的影响进行了探讨。试验结果表明:该方法解决了局部风机停运时传统方法计算修正系数所带来的评价系数和物理过程相悖问题,保证了试验结果的真实可靠性。     

电连接器可靠性试验夹具的设计方法研究

文章简要阐述了电连接试验测试夹具的种类及其使用必要性,对电连接器电气参数测试夹具和力学振动夹具这两种夹具的设计原则、参数确定和试验验证等方面进行了重点阐述,并给出力学振动夹具的验证方法和验证指标。     

利用固控设备处理石油钻井废液的探讨

针对目前油田钻井废液原地固化处理技术易产生新废物、无法循环再利用、占用土地资源、无法根本消除环境风险等问题,按照工业生态理论的指导思想,提出了利用固控设备对钻井废液进行固液物理分离的技术,即对钻井所产生的岩屑、泥饼、清洗水、泥浆等污染物进行密闭循环处理,达到废物循环利用、控制产建投资的目的,这对从源头上控制钻井废液污染所产生的环境风险具有一定的积极意义,尤其对水资源缺乏、生态环境脆弱、成本控制压力较大的生产区具有较好的应用前景。