Vallisneria natans decomposition rates and associated macroinvertebrates,microbes and microalgae along a vertical depth gradient in an urban lake (Nanhu Lake,China)

Knowledge on aquatic macrophyte decomposition has well developed, yet the decomposition and associated biotic factors along a vertical gradient in waters remain less examined. Here, we used Vallianeria natans leaves to investigate the decomposition rate and associated decomposers and microalgae at different vertical depths, by placing V. natans leaves into litterbags (0.5 and 5?mm meshes) and incubating them at the air–water interface (AW), sediment-water (SW) interface, and 10?cm (B10) or 20?cm (B20) burial in sediment over 60 days in a littoral zone of lake. Decomposition rates decreased with increased depths in each mesh size, with significant differences among and between AW (0.028?d^?1), SW (0.022?d^?1), B10 (0.014?d^?1) and B20 (0.011?d^?1) treatments in 0.5?mm litterbags and no significant difference between B10 (0.027?d^?1) and B20 (0.025?d^?1) in 5?mm litterbags. The average contribution of macroinvertebrates to biomass loss was highest in B20 (44.66%), lowest in AW (22.66%) and midst in both SW (25.35%) and B10 (38.78%), and was much less than that of both microbes and microalgae at each location. We show the importance of macroinvertebrates, microbes and microalgae in mediating macrophyte decomposition rate in response to different vertical locations in freshwaters.     

煤对CO2，N2和CH4的吸附速率经验公式与异同性研究*

为了解决吸附速率拟合公式缺乏而解吸经验公式众多的问题，通过替换解吸参数、定性和对比分析各经验公式对煤吸附CO₂，N₂，CH₄吸附速率的适用性，选取4种不同煤质的煤样在0.5，1.0和2.0 MPa下进行定温吸附实验，分析压力和煤质对吸附速率的影响规律。研究结果表明:时间函数式对3种气体在不同压力和煤质下的吸附速率拟合效果最佳；压力和煤质对3种气体吸附速率的影响既存在共性又具有差异性，气体吸附速率与压力符合指数函数关系，与挥发分呈现出二次函数关系，并且压力升高会导致最低吸附速率趋向于较高变质程度煤样；CH₄和N₂的吸附速率随压力升高而升高，而CO₂的吸附速率因煤样而不同，且在同压下，不同气体的最高和最低吸附速率煤样的变质程度也不同。     

基于响应曲面法的遗煤自燃分析与研究*

为研究高瓦斯易自燃煤层不同供风量、高抽巷抽采流量、低抽巷抽采流量3因素对采空区自燃“三带”分布影响规律，选取阳煤五矿8406工作面为研究对象，在数值模拟研究基础上，采用Design Expert软件进行Box Behnken试验设计，构建采空区氧化升温带宽度在3因素、3水平条件下的二次回归响应曲面模型，并对不同条件下采空区氧化升温带宽度进行预测与分析。结果表明:二次回归方程P值为0.001 6，预测模型显著，模型的失拟项为0.606 3，不显著，回归方程具有统计学意义；当供风量为1 500~2 000 m3/min，低抽流量为450~650 m3/min，高抽流量为100~200 m3/min时，对氧化升温带宽度一次项重要度排序为C（高抽巷抽采流量）>A（供风量）>B（低抽巷抽采流量），二次项重要度排序为AC（供风量和高抽巷抽采流量）>AB（供风量和低抽巷抽采流量）>BC（低抽巷抽采流量和高抽巷抽采流量），且AB,AC,BC之间均无交互作用。     

屏蔽服冷却系统对人体表面温度影响的研究*

为科学有效地论证多种方式组合的冷却屏蔽服在不同环境条件下对人体表面温度控制的效果，需要对冷却系统及人体敏感部位发热量进行客观评估。通过对5名健康男性的高温测试，探究人体在不同环境温度下体表温度的变化，得出胸部、背部及额头为热量最高部位，并构建以“人体-降温屏蔽服-外界环境”为主体的冷却系统数值模型，对不同环境中的屏蔽服冷却效果展开研究，分析穿戴冷却屏蔽服时人体躯干部分的温度分布及影响。结果表明:在屏蔽服中靠近胸部、背部部位引入相变材料和风扇，均可帮助人体降低体温，提高舒适度。     

Experimental research of LNG accidental underwater release and combustion behavior

Evaluating potential hazards caused by accidental LNG release from underwater pipelines or vessels is a significant consideration in marine transportation safety. The aim of this study was to capture the dynamic behavior of LNG jet released under water and to analyze its vapor dispersion characteristics and combustion characteristics on the water surface during different release scenarios. Controlled experiments were conducted where LNG was jet released from a cryogenic storage tank. The dynamic process of LNG being jet released from orifices of different sizes and shapes, as well as the rising plume structure, were captured by a high-speed camera. The leakage flow rate and pipeline pressure were recorded by a flow meter and pressure gauge, respectively. The concentration distribution that emanated from the water surface was measured utilizing methane sensors in different positions with various wind speeds. The flame combustion characteristics of LNG vapor clouds, which immediately ignited upon the enclosed water tank, were also recorded. Additionally, the mass burning rate of the flame on the water surface was evaluated, and a new correlation between the ratio of flame length and width was established. The results indicated a large dimensionless heat release rate (Q*) and a continuous release flow rate in a limited burning area. This study could provide greater understanding of the mechanisms of LNG release and combustion behavior under water.     

An experimental study on the burning rate of a continuously released n-heptane spill fire on an open water surface

Spill fires are common during oil product storage and transportation after a loss of containment. Since the burning fuel is moving and the fuel depth is quite shallow, the burning rate in a spill fire is different from that of a pool fire with a static burning zone. Unlike pool fires, which have been studied for decades and have well-established correlations for burning rate, research on spill fires is inadequate. In this paper, continuously released n-heptane spill fire experiments were conducted on open water surfaces with varying fuel discharge rates. The pool diameters were measured, and the spill fire burning rates were estimated based on a dynamic balance between fuel supply and combustion. The burning rates in n-heptane pool fires from the literature were reviewed and compared with the estimated burning rates in spill fires of the same dimension. The spill fire burning rate was found to be close to that in a pool fire during the initial burning phase but lower than that in a bulk burning pool fire and that in a “fuel-level-controlled” pool fire. The distinction between the burning rates of spill fires and pool fires is explained by the heat balance analysis of the fuel layer. A model for the spill fire burning rate was proposed accordingly. The results calculated with the presented model are closer to the measured data than those calculated with pool fire models.     

Pool evaporation: Experimental tests at medium-scale with gasoline

Pool evaporation is a major source of flammable vapour clouds. Predicting the evaporation rate of a liquid hydrocarbon pool is therefore a key issue of dispersion modelling for safety concerns. This paper presents small- and medium-scale experiments of pool evaporation carried out with liquid hydrocarbons (pentane, heptane), hydrocarbon “gasoline-like” mixtures and gasoline. Liquid mass loss was measured and the evaporation rate deduced with its evolution in time. Other observations are highlighted, regarding the evolution of liquid temperatures, mixture compositions, and scale effects like the influence of pool length on surface evaporation rate. Comparisons with well-known correlations are then shown. The authors finally suggest a new semi-empirical correlation with a set of parameters fitted on the performed experiments.     

Estimating the normal background rate of species extinction

A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100–1000 times pre‐human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard‐bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversification—the difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over‐ and under‐estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre‐human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05–0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher. Estimación de la Tasa Normal de Extinción de Especies     

巢湖低温高效聚磷菌的筛选及其特性

采用低温富集培养及混合平板分离技术,从巢湖底泥中分离筛选得到2株在低温下仍具有较高效能的菌株D3、D6,经过厌氧/好氧交替培养,2种菌株在低温下(8℃)的除磷率均达到80%以上。在低温下,研究了p H、微量元素对2株菌株生长及除磷率的影响,实验结果表明,2株菌都具有广泛的温度适应性,适宜其生长和除磷的p H为中性偏碱,微量元素的缺乏对2株菌株的生长和除磷效果有不同程度的不良影响。染色观察显示,厌氧培养时菌体内聚羟基丁酸(PHB)颗粒明显增多,转为好氧培养后异染颗粒增多,为典型的聚磷菌特征。经鉴定,2株菌均属假单胞菌属。     

活性炭涂层电极电容去离子的性能

采用活性炭涂层电极构建电容去离子吸附装置,以氯化钠模拟含盐原水,研究电压、流量、进水浓度等操作参数对活性炭涂层电极脱盐效率和能耗的影响。实验结果表明,去除率和比吸附量随着电压的增大而增加,且比能耗随之增大。流速越小,出水的浓度越低,当对出水的浓度要求较高时,宜采用小流速。当进水浓度低于活性炭涂层电极的饱和吸附量时,比吸附量随着进水浓度呈线性增加;当达到饱和吸附量时,比吸附量不会随进水浓度的增大而发生改变;比能耗随着进水浓度的增加而降低。