Changes in gill histology of fathead minnows and yellow perch transferred to soft water or acidified soft water with particular reference to chloride cells

Summary Fathead minnows, Pimephales promelas, and yellow perch, Perca flavescens, were transferred from moderately soft Lake Superior water (hardness 45mg/l as CaCO₃) to very soft diluted Lake Superior water (hardness 4.5mg/l). Sulfuric acid was added in some treatments by means of a multichannel diluter. In very soft water, chloride cells proliferated in the gills, especially in the epithelium of the secondary lamellae. When exposed to acid, chloride cells were damaged and less abundant in the secondary lamellae, and blood osmolality was reduced at pH 5.0 (x = 188 mOsm/kg, 9 days exposure; normal 280 mOsm/kg) for the minnows and pH 4.1 (x = 218 mOsm/kg, 58 days exposure; normal 329 mOsm/kg) for the perch. Certain chloride cells which form gland-like clusters in the primary lamellae of perch gills showed little damage even at pH 4.1. The present study supports the view that chloride cells proliferate in very soft fresh water to help maintain ionic balances, and that damage to these cells in acidified soft water may be related to diminished ionoregulatory capacity. The greater acid tolerance of chloride cells of, and the higher blood osmolality maintained by, perch could help to explain the greater tolerance of this species to low pH. In some cases, a species' ability to acclimate to very soft water and acidified soft water may depend upon the number, distribution, and physiology of its chloride cells.     

水分梯度下胡杨荒漠河岸林种内竞争及空间格局变化特征

为查明塔里木河下游不同水分梯度下胡杨种内竞争以及空间分布格局的变化规律,在塔里木河下游阿拉干断面选取3条样带,每条样带内依照水分梯度布设3个样方,采用Hegyi单木竞争模型与点格局等分析方法,探究了水分梯度下胡杨林种内竞争及空间格局变化特征。结果表明：1)塔里木河下游胡杨的最适竞争范围为10m; 2)胡杨竞争指数与胸径服从幂函数关系(P<0.001),胡杨竞争指数随对象木胸径的增加而逐渐减小,当对象木胸径达到20cm以上时,其竞争指数逐渐稳定,且维持在较低水平;3)随水分梯度的降低,胡杨林分竞争指数呈下降趋势;4)在塔里木河下游,胡杨空间格局主要为聚集分布,随空间尺度的增加,胡杨逐渐趋向于随机分布;5)随水分梯度的降低,胡杨空间格局由聚集分布逐渐转变为随机分布。水分是决定极端干旱区荒漠植被空间分布与结构的主要因子;在胡杨林分管理中,应充分考虑胡杨的种内竞争、空间格局及其与水分梯度之间关系,为塔里木河下游胡杨林的保护与更新提供科学依据。     

青弋江流域大型底栖动物群落结构及水质评价

研究河流大型底栖动物群落结构特征及水环境质量对水生态的保护与修复具有重要意义。以青弋江流域为研究对象,于2020年9月进行了大型底栖动物及水体理化因子的调查,采用相对重要性指数、生物多样性指数及Jaccard相似性系数分析了大型底栖动物群落结构特征,运用丰度/生物量比较曲线法及冗余分析法探究了底栖动物群落受到的干扰程度及其主要影响环境因子,最后利用水生态环境质量综合指数对河流水质进行评价。研究结果表明：(1)共采集鉴定大型底栖动物61种,隶属于3门6纲17目,平均丰度为265.9个/m~2,平均生物量41.6 g/m~2。相对重要性指数分析显示,日本沼虾(Macrobrachium nipponensis)、中国圆田螺(Cipangopaludina chinensis)、羽摇蚊(Chironomus plumosus)及扁蜉(Ecdyrus)为群落中的主要优势种。(2)由群落相似性分析知,Jaccard相似性系数较低,调查点位之间存在较强的空间异质性。(3)冗余分析表明,电导率、氨氮浓度及流速是影响底栖动物群落结构的主要环境因子。(4)生物指数分析结果显示该流域水质为轻度污染或中度污...     

Overcoming Microstructural Limitations in Water Processed Organic Solar Cells by Engineering Customized Nanoparticulate Inks

The application of conjugated polymer and fullerene water‐based nanoparticles (NP) as ecofriendly inks for organic photovoltaics (OPVs) is reported. A low bandgap polymer diketopyrrolopyrrole–quinquethiophene (PDPP5T‐2) and the methanofullerene PC₇₁BM are processed into three types of nanoparticles: pristine fullerene NPs, pristine polymer NPs, and mixed polymer:fullerene NPs, allowing the formation of bulk heterojunction (BHJ) composites with different domain sizes. Mild thermal annealing is required to melt the nanospheres and enable the formation of interconnected pathways within mixed phases. This BHJ is accompanied by a shrinkage of film, whereas the more compact layers show enhanced mobility. Consistently reduced recombination and better performance are found for mixed NP, containing both, the polymer and the fullerene within a single NP. The optimized solar cell processed by ultrasmall NPs delivers a power conversion efficiency of about 3.4%. This is among the highest values reported for aqueous processed OPVs but still lacks performance compared to those being processed from halogenated solvents. Incomplete crystallization is identified as the main root for reduced efficiency. It is nevertheless believed that postprocessing does not cut attraction from printing aqueous organic NP inks as a trendsetting strategy for the reliable and ecofriendly production of organic solar cells.     

长期灌溉施肥对半干旱区褐土氮、磷和钾库的影响Ⅱ.对褐土农田土壤钾库的影响

采用二次通用旋转组合设计 ,在辽西半干旱区褐土上进行了长期田间试验 ,研究不同的灌水、施氮、施磷和施秸秆水平对土壤钾含量的影响。结果表明 ,土壤全钾含量随着氮、磷和秸秆施用量的增加而增加 ,随着灌水量的增加而降低 ,其中 ,施磷对土壤全钾含量的增加效果最明显 ,其次是施秸秆量。土壤速效钾含量随着灌水和氮、磷施用量的增加而降低 ,随着秸秆施用量的增加而增加 ,其中 ,施秸秆对土壤的速效钾含量影响最明显 ,其次是施用磷肥的影响。另外 ,施肥和灌水在提高土壤全钾含量的同时可能使速效钾含量降低 ,两者的变化表现为一定的负相关。     

BTEX的环境质量标准研究进展

苯系物(BTEX)是苯(benzene)、甲苯(toluene)、乙苯(ethylbenzen)和二甲苯的3种同分异构体(o-,m-,p-xylene)的统称。由于其广泛存在于大气、水和土壤等环境介质中,并对相应的生态系统和人类健康造成威胁,引起了有关部门的高度重视。本文综述了BTEX的环境质量标准研究,通过介绍美国环保局、澳大利亚和加拿大等发达国家以及世界卫生组织、欧盟等国际组织关于BTEX的室内空气、地表水和土壤环境质量标准,并与我国对应标准进行比较,指出我国环境质量标准中存在的一些问题和不足。最后,对今后我国BTEX环境基准的系统研究提出建议。     

经济杀菌灭藻剂OACL控制工业循环水中有害微生物的研究

研究了经济杀菌灭藻剂OACL对异氧菌、硫酸盐还原菌和铁细菌的杀菌作用。结果表明,在实验室条件下,其杀菌率平均为99％以上,在pH5和pH7时分别为97.8％和88％。而在现场投药试验条件下为92％以上。可以认为,OACL是一种新型的、经济的高效杀菌灭藻剂。     

Responses of riparian trees to interannual variation in ground water depth in a semi-arid river basin

We investigated the physiological and growth responses of native (Populus fremontii S. Wats. and Salix gooddingii Ball) and exotic (Tamarix chinensis Lour.) riparian trees to ground water availability at the free‐flowing Hassayampa River, Arizona, during dry (1997) and wet (1998) years. In the drier year, all species experienced considerable water stress, as evidenced by low shoot water potentials, low leaf gas exchange rates and large amounts of canopy dieback. These parameters were significantly related to depth of ground water (DGW) in the native species, but not in T. chinensis, in 1997. Canopy dieback was greater in the native species than in T. chinensis when ground water was deep in 1997, and dieback increased rapidly at DGW > 2·5–3·0 m for the native species. Analysis of combined data from wet and dry years for T. chinensis tentatively suggests a similar physiological sensitivity to water availability and a similar DGW threshold for canopy dieback. In 1998, shoot water potential and leaf gas exchange rates were higher and canopy dieback was lower for all species because of increased water availability. However, T. chinensis showed a much larger increase in leaf gas exchange rates in the wet year than the native species. High leaf gas exchange rates, growth when water is abundant, drought tolerance and the maintenance of a viable canopy under dry conditions are characteristics that help explain the ability of T. chinensis to thrive in riparian ecosystems in the south‐western United States.     

氮、磷、钾营养对冬小麦光合作用及水分利用的影响

在中国科学院封丘农业生态实验站长期肥料实验的基础上,选择氮磷(T1)、氮钾(T2)、磷钾(T3)和氮磷钾(T4)4个肥料处理,以不施肥为对照(CK),研究了长期施用氮、磷、钾肥对小麦抽穗期和灌浆期净光合速率(Pn)、蒸腾速率(Tr)和水分利用效率(WUE)日变化的影响.结果表明:小麦抽穗期和灌浆期T4处理的Pn日变化值显著高于CK,其他处理与CK未达到显著性差异,各处理Pn日积累量大小为T4＞T1＞T2＞T3＞CK;缺氮、缺磷和缺钾均降低了叶片Pn,影响大小依次为缺氮＞缺磷＞缺钾;小麦抽穗期和灌浆期Tr日变化曲线呈单峰型,处理间日变化值差异不显著;缺氮、缺磷和缺钾均降低了叶片WUE,抽穗期,T1、T4处理的WUE日变化值显著高于CK,而T3、T2与CK差异不显著,说明缺氮、缺磷对WUE的影响最大,灌浆期,T4处理的WUE日变化值显著高于CK;不同肥料处理仅改变了小麦光合日变化的幅度,而未改变其变化规律,氮、磷、钾复合施肥有效地提高了小麦的光合生产和水分利用效率.     

Simple method for developing percentile growth curves for height and weight

The present paper demonstrates the ease of use of method I by Preece and Baine ([1978] Ann Hum Biol 5:1-24) in generating smoothed growth curves for both height and weight. Using the National Center for Health Statistics (NCHS) growth curve data, smoothed curves were developed and compared to those produced using the least-squares-cubic-spline method. Based on the lower sum of squares and better fit of shape as indicated by residual examination, it was concluded that the method I curve fitting procedure by Preece and Baine ([1978] Ann Hum Biol 5:1-24) fit centile growth curves for height and weight in 2-18-year-old male and female children as well as, if not better than, the least-squares-cubic-spline method used in developing the 1979 NCHS growth curves. Further, as this paper demonstrates, smoothed curves can be generated on a desktop computer using readily available software (the SOLVER function within Microsoft EXCEL).