Effect of algal flocculation on dissolved organic matters using cationic starch modified soils

Modified soils(MSs) are being increasingly used as geo-engineering materials for the sedimentation removal of cyanobacterial blooms. Cationic starch(CS) has been tested as an effective soil modifier, but little is known about its potential impacts on the treated water.This study investigated dissolved organic matters in the bloom water after algal removal using cationic starch modified soils(CS-MSs). Results showed that the dissolved organic carbon(DOC) could be decreased by CS-MS flocculation and the use of higher charge density CS yielded a greater DOC reduction. When CS with the charge density of 0.052, 0.102 and0.293 meq/g were used, DOC was decreased from 3.4 to 3.0, 2.3 and 1.7 mg/L, respectively.The excitation–emission matrix fluorescence spectroscopy and UV254 analysis indicated that CS-MS exhibits an ability to remove some soluble organics, which contributed to the DOC reduction. However, the use of low charge density CS posed a potential risk of DOC increase due to the high CS loading for effective algal removal. When CS with the charge density of 0.044 meq/g was used, DOC was increased from 3.4 to 3.9 mg/L. This study suggested, when CS-MS is used for cyanobacterial bloom removal, the content of dissolved organic matters in the treated water can be controlled by optimizing the charge density of CS. For the settled organic matters, other measures(e.g., capping treatments using oxygen loaded materials) should be jointly applied after algal flocculation.     

贵州省主要森林类型土壤有机碳密度特征及其影响因素

森林土壤有机碳是全球土壤有机碳库的重要组成部分,研究森林土壤有机碳对于减缓大气中CO2浓度持续升高具有重要的意义。本研究采用野外调查和室内分析相结合的方法,以贵州桦木、栎类、柏木、云南松、杉木、马尾松、华山松等7种主要森林类型为主要对象,分析贵州主要森林类型土壤有机碳密度特征,探讨不同植被类型和环境因子对其的影响。结果表明:(1)贵州森林土壤有机碳密度约为180.62Mg/hm2,高于同纬度地区江西省森林土壤平均有机碳密度102.1Mg/hm2,表现出贵州森林土壤具有较高的固碳能力;(2)不同森林类型土壤有机碳密度变化范围为:114.52~388.29Mg/hm2,且差异显著(P0.05)。各种森林类型土壤有机碳密度大小为:华山松林杉木林柏木林栎类林马尾松林桦木林云南松林;(3)不同植被类型下各层土壤有机碳密度大小均以表层土壤为最大,且随土壤深度增加而降低;(4)在立地条件上,贵州森林土壤有机碳密度与海拔显著相关,与坡度、经度、纬度相关关系均不显著。     

Grassland Bird Responses to Land Management in the Largest Remaining Tallgrass Prairie

Abstract: Extensive habitat loss and changing agricultural practices have caused widespread declines in grassland birds throughout North America. The Flint Hills of Kansas and Oklahoma—the largest remaining tallgrass prairie—is important for grassland bird conservation despite supporting a major cattle industry. In 2004 and 2005, we assessed the community, population, and demographic responses of grassland birds to the predominant management practices (grazing, burning, and haying) of the region, including grasslands restored under the Conservation Reserve Program (CRP). We targeted 3 species at the core of this avian community: the Dickcissel (Spiza americana), Grasshopper Sparrow (Ammodramus savannarum), and Eastern Meadowlark (Sturnella magna). Bird diversity was higher in native prairie hayfields and grazed pastures than CRP fields, which were dominated by Dickcissels. Although Dickcissel density was highest in CRP, their nest success was highest and nest parasitism by Brown‐headed Cowbirds (Moluthrus ater) lowest in unburned hayfields (in 2004). Conversely, Grasshopper Sparrow density was highest in grazed pastures, but their nest success was lowest in these pastures and highest in burned hayfields, where cowbird parasitism was also lowest (in 2004). Management did not influence density and nest survival of Eastern Meadowlarks, which were uniformly low across the region. Nest success was extremely low (5–12%) for all 3 species in 2005, perhaps because of a record spring drought. Although the CRP has benefited grassland birds in agricultural landscapes, these areas may have lower habitat value in the context of native prairie. Hayfields may provide beneficial habitat for some grassland birds in the Flint Hills because they are mowed later in the breeding season than elsewhere in the Midwest. Widespread grazing and annual burning have homogenized habitat—and thus grassland‐bird responses—across the Flint Hills. Diversification of management practices could increase habitat heterogeneity and enhance the conservation potential of the Flint Hills for grassland birds.     

Potential Misuse of Avian Density as a Conservation Metric

Abstract: Effective conservation metrics are needed to evaluate the success of management in a rapidly changing world. Reproductive rates and densities of breeding birds (as a surrogate for reproductive rate) have been used to indicate the quality of avian breeding habitat, but the underlying assumptions of these metrics rarely have been examined. When birds are attracted to breeding areas in part by the presence of conspecifics and when breeding in groups influences predation rates, the effectiveness of density and reproductive rate as indicators of habitat quality is reduced. It is beneficial to clearly distinguish between individual‐ and population‐level processes when evaluating habitat quality. We use the term reproductive rate to refer to both levels and further distinguish among levels by using the terms per capita fecundity (number of female offspring per female per year, individual level) and population growth rate (the product of density and per capita fecundity, population level). We predicted how density and reproductive rate interact over time under density‐independent and density‐dependent scenarios, assuming the ideal free distribution model of how birds settle in breeding habitats. We predicted population density of small populations would be correlated positively with both per capita fecundity and population growth rate due to the Allee effect. For populations in the density‐dependent growth phase, we predicted no relation between density and per capita fecundity (because individuals in all patches will equilibrate to the same success rate) and a positive relation between density and population growth rate. Several ecological theories collectively suggest that positive correlations between density and per capita fecundity would be difficult to detect. We constructed a decision tree to guide interpretation of positive, neutral, nonlinear, and negative relations between density and reproductive rates at individual and population levels.     

冷凝膜油气回收技术在轻质油汽车装车中的应用

介绍了油气回收技术的基本原理,着重介绍了冷凝膜回收工艺技术的特点,及冷凝膜回收装置在中国石化青岛石油化工有限责任公司轻质油汽车装车的应用情况,分析了存在的问题及改进建议。     

Assessing the strength of climate and land-use influences on montane epiphyte communities

Epiphytes, air plants that are structurally dependent on trees, are a keystone group in tropical forests; they support the food and habitat needs of animals and influence water and nutrient cycles. They reach peak diversity in humid montane forests. Climate predictions for Central American mountains include increased temperatures, altered precipitation seasonality, and increased cloud base heights, all of which may challenge epiphytes. Although remaining montane forests are highly fragmented, many tropical agricultural systems include trees that host epiphytes, allowing epiphyte communities to persist even in landscapes with lower forest connectivity. I used structural equations models to test the relative effects of climate, land use, tree characteristics, and biotic interactions on vascular epiphyte diversity with data from 31 shade coffee farms and 2 protected forests in northern Nicaragua. I also tested substrate preferences of common species with randomization tests. Tree size, tree diversity, and climate all affected epiphyte richness, but the effect of climate was almost entirely mediated by bryophyte cover. Bryophytes showed strong sensitivity to mean annual temperature and insolation. Many ferns and some orchids were positively associated with bryophyte mats, whereas bromeliads tended to establish among lichen or on bare bark. The tight relationships between bryophytes and climate and between bryophytes and vascular epiphytes indicated that relatively small climate changes could result in rapid, cascading losses of montane epiphyte communities. Currently, shade coffee farms can support high bryophyte cover and diverse vascular epiphyte assemblages when larger, older trees are present. Agroforests serve as valuable reservoirs for epiphyte biodiversity and may be important early-warning systems as the climate changes.     

人员密度和出口宽度的不确定性对疏散行动时间的影响

基于Kikuji Togawa所提出的常用人员疏散行动时间经验公式，使用拉丁超立方抽样法，研究房间人员密度和出口宽度的不确定性对疏散行动时间的影响。得出二者服从均匀分布和正态分布条件下，疏散行动时间的概率密度直方图和累积概率曲线。结果表明，人员密度和出口宽度的不同分布形式对疏散行动时间都有显著影响，二者服从正态分布时，计算得到的疏散行动时间范围比服从均匀分布小，且较为集中。而服从均匀分布时，计算得到的疏散行动时间在其范围内则较为均匀、分散。在小概率0～0．1区间范围内，人员密度和出口宽度服从正态分布时，计算得到的疏散行动时间累计概率值明显较均匀分布小，说明二者服从正态分布得到的疏散行动时间值偏于保守。二者均为不确定参数时，假定人员密度服从均匀分布，出口宽度服从正态分布时计算得出的疏散行动时间值偏于保守。     

多维旋度大循环经济圈发展模式研究——产业集群视角下以黑龙江省为例

为了定量分析省域空间特征区域间的经济增长关系,通过引入场论理论框架,结合集聚经济学和传统空间区域划分理论观点,提出多维旋度大循环经济圈发展模型。定义资金通量经济场,以资金通量流速和资金通量密度为主要测度指标来衡量特征区域的经济学指标。以黑龙江省大循环经济圈发展模式的建设构思检验模型的合理性,并由此得出黑龙江省实现经济再增长的关键问题是要处理好农林产业、能源产业、其他新兴服务产业同外贸产业之间相互触发、互为依存的激励关系。     

Extinguishment of hydrogen laminar diffusion flames by water vapor in a cup burner apparatus

Transient computations with full hydrogen chemistry were performed to reveal the flame structure and extinguishment process of co-flow, hydrogen diffusion flame suppressed by water vapor. As the concentration of water vapor was increased, the flame detached away from the burner brim and formed an edge flame at the flame base. Water vapor showed larger chemical inhibition effect than nitrogen when extinguishing hydrogen flame, which was attributed to its enhanced third body effect in the reaction H + O₂ + M = HO₂ + M. The minimum extinguishing concentration (MEC) of water vapor and nitrogen was predicted by Senecal formula and perfectly stirred reactor (PSR) model respectively. The MECs predicted by PSR model agree with the MECs calculated by Fluent, which shows that 1) the flame extinction is controlled by the flame base, and 2) radiation absorption is negligible. The measured MECs are in a reasonable agreement with the values calculated by Fluent, which demonstrates the accuracy of the CFD model. A simple model was used to investigate the relative importance of extinguishing mechanisms of water vapor. The results show that in a co-flow configuration the thermal cooling and chemical inhibition effect are the main extinguishing mechanisms in suppressing hydrogen diffusion cup burner flame.     

浅述汽车加油站油气回收系统监测研究

加油站油气回收系统是由卸油油气回收系统、汽油密闭储存、加油油气回收系统、在线监测系统和油气排放处理装置组成。该系统的作用是将加油站在卸油、储油和加油过程中产生的油气,通过密闭收集、储存和送入油罐汽车的罐内,运送到储油库集中回收变成汽油,以达到在汽车加油、油料储运过程中油汽不外泄,不污染周边环境的目的。根据中华人民共和国《加油站大气污染物排放标准》(GB 20952-2007)中第六条的规定,长三角地区的改造项目应在2010年1月1日进行,因此对加油站油气回收系统的监测显得十分紧迫。