碳纳米管预沉积改性膜的污染机理研究

为探究碳纳米管(Carbon Nanotubes,CNTs)预沉积改性膜的污染机理,本研究使用正压过滤法将CNTs预沉积在3种孔径的有机膜(20 kDa聚醚砜膜、0.01 μm和0.1 μm聚偏二氟乙烯膜)表面,研究了CNTs预沉积改性膜过滤3种典型污染物(牛血清蛋白、腐殖酸、海藻酸钠)过程中的膜污染情况.根据比通量、Hermia模型和传统滤饼过滤模型,对恒压死端过滤3种典型污染物过程中的污染机理进行了系统评价.结果表明,20 kDa PES膜和0.01 μm PVDF膜表面预沉积CNTs改性后,过滤3种典型膜污染物质时的膜污染情况都得到了一定程度的缓解.20 kDa PES膜表面预沉积CNTs后过滤HA初期为完全孔堵塞与滤饼过滤相结合的复合污染机理,最终转变为滤饼过滤;过滤SA的污染机理为完全孔堵塞与滤饼过滤相结合的复合污染机理.0.01 μm PVDF膜表面沉积CNTs改性后过滤HA初期的污染机理为膜孔堵塞与滤饼过滤相结合的复合污染机理,然后经过向滤饼过滤转变的过渡阶段,最终形成滤饼过滤,且随着CNTs沉积量的增加,过渡阶段持续时间延长.0.1 μm PVDF膜表面预沉积CNTs后过滤3种污染物,均未能缓解膜污染,膜污染机理不受CNTs沉积改性的影响,其过滤BSA和HA的污染机理为膜孔堵塞,过滤SA过程的污染机理符合滤饼过滤.     

Revealing life‐history traits by contrasting genetic estimations with predictions of effective population size

Effective population size, a central concept in conservation biology, is now routinely estimated from genetic surveys and can also be theoretically predicted from demographic, life‐history, and mating‐system data. By evaluating the consistency of theoretical predictions with empirically estimated effective size, insights can be gained regarding life‐history characteristics and the relative impact of different life‐history traits on genetic drift. These insights can be used to design and inform management strategies aimed at increasing effective population size. We demonstrated this approach by addressing the conservation of a reintroduced population of Asiatic wild ass (Equus hemionus). We estimated the variance effective size (N_ev) from genetic data () and formulated predictions for the impacts on N_ev of demography, polygyny, female variance in lifetime reproductive success (RS), and heritability of female RS. By contrasting the genetic estimation with theoretical predictions, we found that polygyny was the strongest factor affecting genetic drift because only when accounting for polygyny were predictions consistent with the genetically measured N_ev. The comparison of effective‐size estimation and predictions indicated that 10.6% of the males mated per generation when heritability of female RS was unaccounted for (polygyny responsible for 81% decrease in N_ev) and 19.5% mated when female RS was accounted for (polygyny responsible for 67% decrease in N_ev). Heritability of female RS also affected N_ev; (heritability responsible for 41% decrease in N_ev). The low effective size is of concern, and we suggest that management actions focus on factors identified as strongly affecting , namely, increasing the availability of artificial water sources to increase number of dominant males contributing to the gene pool. This approach, evaluating life‐history hypotheses in light of their impact on effective population size, and contrasting predictions with genetic measurements, is a general, applicable strategy that can be used to inform conservation practice.     

Characterization of bacterial communities during persistent fog and haze events in the Qingdao coastal region

• Light haze had little effect on bacterial communities. • Fog and heavy haze had significant effects on these communities. • Air pollution exerted a greater influence than particle size on bacterial community. Here, we report the characteristics of bacterial communities in aerosols with different particle sizes during two persistent fog and haze events in December of 2015 and 2016 in Qingdao, China. In the early stage of pollution, the accumulation of PM_2.5 led to the accumulation of microorganisms, thus increasing the bacterial richness and diversity of fine particle sizes. With the persistence and aggravation of pollution, the toxic effect was strengthened, and the bacterial richness and diversity of each particle size decreased. When the particle concentration was highest, the richness and diversity were low for each particle size. Light haze had little influence on bacterial communities. The occurrence of highly polluted humid weather and heavy haze resulted in significant changes in bacterial community diversity, composition and structure, and air pollution exerted a greater influence than particle size on bacterial community structure. During persistent fog and haze events, with the increase of pollutants, bacteria associated with each particle size may be extensively involved in aerosol chemistry, but the degree of participation varies, which requires further study.     

Combined effects of life-history traits and human impact on extinction risk of freshwater megafauna

Megafauna species are intrinsically vulnerable to human impact. Freshwater megafauna (i.e., freshwater animals ≥30 kg, including fishes, mammals, reptiles, and amphibians) are subject to intensive and increasing threats. Thirty-four species are listed as critically endangered on the International Union for Conservation of Nature (IUCN). Red List of Threatened Species, the assessments for which are an important basis for conservation actions but remain incomplete for 49 (24%) freshwater megafauna species. Consequently, the window of opportunity for protecting these species could be missed. Identifying the factors that predispose freshwater megafauna to extinction can help predict their extinction risk and facilitate more effective and proactive conservation actions. Thus, we collated 8 life-history traits for 206 freshwater megafauna species. We used generalized linear mixed models to examine the relationships between extinction risk based on the IUCN Red List categories and the combined effect of multiple traits, as well as the effect of human impact on these relationships for 157 classified species. The most parsimonious model included human impact and traits related to species’ recovery potential including life span, age at maturity, and fecundity. Applying the most parsimonious model to 49 unclassified species predicted that 17 of them are threatened. Accounting for model predictions together with IUCN Red List assessments, 50% of all freshwater megafauna species are considered threatened. The Amazon and Yangtze basins emerged as global diversity hotspots of threatened freshwater megafauna, in addition to existing hotspots, including the Ganges-Brahmaputra and Mekong basins and the Caspian Sea region. Assessment and monitoring of those species predicted to be threatened are needed, especially in the Amazon and Yangtze basins. Investigation of life-history traits and trends in population and distribution, regulation of overexploitation, maintaining river connectivity, implementing protected areas focusing on freshwater ecosystems, and integrated basin management are required to protect threatened freshwater megafauna in diversity hotspots.     

受限空间开口对细水雾灭火有效性影响实验研究

为了探讨开口的位置与尺寸对受限空间内的细水雾灭火有效性的影响,设计了一个尺寸为1.2 m×1.2 m×1.2 m的特殊受限空间模拟实验台,开展了一系列细水雾灭火对比实验,测量了烟气温度以及灭火时间等实验参数,通过改变实验燃料、火源功率、开口尺寸、开口位置等因素来研究开口对特殊受限空间内细水雾灭火有效性的影响规律。结果表明:在特殊受限空间内,相同条件下,开口位置由下至上,细水雾抑制火灾有效性由低至高;开口尺寸由大至小,细水雾抑制火灾有效性由高至低。当开口尺寸足够小以后,细水雾抑制火灾有效性反而会逐渐增强。     

窄脉冲电晕放电烟气脱硫产物粒径分析的实验研究

为了便于脱硫产物的收集和应用,用沉降法采样,用电子显微镜对产物气溶胶进行粒径分析．实验在窄脉冲电晕放电装置上,模拟含硫烟气在工况条件下（气体流量２ｍ３／ｈ,反应器入口处ＳＯ２浓度２０００ｍｌ／ｍ３,ＳＯ２和ＮＨ３在通道中停留时间为５ｓ以上,温度６０℃、水蒸气体积比７．５％,相对湿度３８．２％）进行．电子显微镜的观测结果显示,脱硫产物粉尘结构疏松,颗粒形状不规则．根据电镜照片的统计结果,得出产物粉尘的数目中位径ＮＭＤ为０．４０μｍ,几何标准偏差σ１＝５．２１;质量中位径ＭＭＤ为２．８２μｍ,几何标准偏差σ２＝１．４３     

负压隔离器内病毒空气传播影响因素的研究

病毒活性及病毒气溶胶粒径是病毒空气传播实验中的重要影响因素.病毒活性主要与环境温湿度有关.为了研究负压隔离器内颗粒粒径的影响因素,测量了实际运行工况下的两种粒径的颗粒浓度,并对不同换气次数、送风温度下颗粒浓度和粒径分布进行数值模拟.结果表明,不同粒径颗粒分布规律趋于一致;增加换气次数会导致气流旋涡区域颗粒浓度升高;随着...     

Individual and collective foraging decisions: a field study of worker recruitment in the gypsy ant <Emphasis Type="Italic">Aphaenogaster senilis</Emphasis>

In social insects, the decision to exploit a food source is made both at the individual (e.g., a worker collecting a food item) and colony level (e.g., several workers communicating the existence of a food patch). In group recruitment, the recruiter lays a temporary chemical trail while returning from the food source to the nest and returns to the food guiding a small group of nestmates. We studied how food characteristics influence the decision-making process of workers changing from individual retrieving to group recruitment in the gypsy ant Aphaenogaster senilis. We offered field colonies three types of prey: crickets (cooperatively transportable), shrimps (non-transportable), and different quantities of sesame seeds (individually transportable). Colonies used group recruitment to collect crickets and shrimps, as well as seeds when they were available in large piles, while small seed piles rarely led to recruitment. Foragers were able to “measure” food characteristics (quality, quantity, transportability), deciding whether or not to recruit, accordingly. Social integration of individual information about food emerged as a colony decision to initiate or to continue recruitment when the food patch was rich. In addition, group recruitment allowed a fast colony response over a wide thermal range (up to 45°C ground temperature). Therefore, by combining both advantages of social foraging (group recruitment) and thermal tolerance, A. senilis accurately exploited different types of food sources which procured an advantage against mass-recruiting and behaviorally dominant species such as Tapinoma nigerrimum and Lasius niger.     

半干旱区春季沙尘气溶胶谱分布的观测研究

为研究半干旱区沙尘细粒子的粒谱特征,利用WPS粒谱仪对内蒙古朱日和地区春季粒径为0.01~10.0mm的沙尘气溶胶进行了40多天的连续观测,得到不同天气条件下的气溶胶谱分布.研究表明,沙尘气溶胶有明显的日分布规律,不同天气背景下的沙尘气溶胶浓度变化特征不同,受气象要素影响较大.非沙尘日和沙尘日均有浓度变化较稳定的粒径段,沙尘日出现稳定粒径段的粒径小于非沙尘日,2种天气背景下的平均谱在0.07~0.20mm;非沙尘日、沙尘日和沙尘时段的气溶胶谱型在0.01~0.1mm、0.1~1.0mm和1.0~10mm 3个粒径段分布明显不同,分别符合对数正态分布、Lorentz分布和负指数分布.     

Particle size distribution and pollutants in road-deposited sediments in different areas of Zhenjiang,China

An understanding of road-deposited sediment (RDS) characteristics on an impervious surface is essential to estimate pollutant washoff characteristics and to minimise the impacts of pollutants on the water environment. A total of 62 RDS samples were collected from four different land-use types (commercial, residential, intense traffic and riverside park) in Zhenjiang City, China. The samples were fractionated into seven grain-size classes and analysed for particle size distribution and concentrations of pollutants. The samples are found to consist predominantly of fine particles (60–80%, <250 μm). The maximum mean concentrations of zinc, lead and copper were 686.93, 589.19 and 158.16 mg/kg, respectively, with the highest metal concentrations found in samples from the intense traffic area. The maximum mean contents of organic matter (12.55%), nitrogen (6.31 mg/g) and phosphorus (5.15 mg/g) were found in samples from the commercial area. The concentrations of heavy metals were highest in the smallest particle size fraction analysed (63 μm). The organic matter and nitrogen content generally increased with decreasing particle sizes in the <500-μm particle size range. The results also revealed that most of the total nitrogen (TN) is attached to the finer sediments and that to effectively reduce TN loads in particulates, treatment facilities must be able to remove the finer particles (down to 125 μm for TN).