三峡水库及香溪河库湾理化特征的比较研究

根据2003年6月三峡水库初期蓄水后对香溪河库湾的常规监测,对该水域的理化特征及其动态进行了分析,并与三峡水库库首的数据进行了比较研究。结果显示库湾TN、NO3-N浓度要显著低于库首,前者两周年平均值为1.29mg/L,0.88mg/L,后者两周年平均值为1.62mg/L,1.22mg/L。而PO4-P则是库湾显著高于库首,并且在7—9月库首的TP/PO4-P有显著提高。结果同时表明库首的水土流失较严重,而库湾则有较好的水土保持。最后对TSIM的计算结果表明,由于TP、TN都处于高水平,库首呈现中营养化(TSIM>37),而库湾则呈现严重富营养化(TSIM>53)。     

水质对东江流域附生硅藻群落的影响

运用相关分析(CA),典型对应分析(CCA),加权平均分析(WA)研究了影响东江流域附生硅藻的主要水质因子及对应的最适生态范围。CA显示,13项水质指标中溶解氧(Dissolved Oxygen,DO)、氨氮(NH4-N)、亚硝氮(NO2-N)、氯化物(Cl)、五日生化需氧量(BOD5)、磷酸盐(PO4-P)与其它指标间的相关性较强(P0.05),其余指标间相关性较低(P0.05)。以相关性较弱的p H、电导率(Cond.)、硅酸盐(Si O2)、总磷(TP)、总氮(TN)、硝氮(NO3-N)、化学需氧量(CODKMn O4)进行CCA分析,排序显示影响附生硅藻的水质因子依次为Cond.、NO3-N、CODKMn O4、TP、TN,对应的生态最适范围分别为39.20—642.00μs/cm、0.46—2.77mg/L、1.0—5.5mg/L、0.02—0.64mg/L、0.48—3.43mg/L。研究表明,Cond、NO3-N、CODKMn O4、TP、TN是影响东江附生硅藻分布的主要水质因子,Cyclostephanos invisitatus、Gomphonema olivaceum、Nitzschia acicularis、N.capitellata、N.intermedia可以指示东江较高的电导率,Aulacoseira ambigua、A.lirata、Cyclotella meneghiniana、Cyclostephanos invisitatus、Eunotia minor、Nitzschia acicularis、N.Clausii、Pinnularia subcapitata是东江TN、TP污染的指示种。Nitzschia acicularis对TN、TP的耐受性最高,Navicula eidrigiana对TN、TP敏感性最强。     

杭州西湖北里湖沉积物氮磷内源静态释放的季节变化及通量估算

通过采集北里湖不同季节的柱状芯样,在实验室静态模拟沉积物氨氮(NH+4-N)和可溶解性磷酸盐(PO3-4-P)的释放,同时研究了沉积物间隙水中NH+4-N及PO3-4-P的垂直分布特征.结果表明,沉积物间隙水NH+4-N随深度的增加有上升的趋势,PO3-4-P随深度的增加呈先升后降的趋势.氮、磷营养盐在沉积物—水界面均存在浓度梯度,表明存在自间隙水向上覆水扩散的趋势.沉积物NH+4-N在春季、夏季、秋季、冬季的释放速率分别为0.074 mg·m-2· d-1、0.340mg· m-2· d-1、0.087 mg· m-2· d-1、0.0004 mg·m-2·d-1,pO3-4-P的释放速率则分别为0.340 mg·m-2·d-1、0.518 mg·m-2·d-1、0.094 mg·m-2·d-1、-0.037 mg· m-2·d-1.不同采样点表现出明显的季节和空间差异性,释放速率表现为夏季＞春季、秋季＞冬季.根据静态模拟出的不同季节下内源氮、磷释放速率计算,全湖内源氮、磷营养盐的贡献分别为0.0037、0.0057t/a.该研究可为北里湖富营养化及内源污染的治理提供基础数据.     

珠江口及毗邻海域营养盐对浮游植物生长的影响

基于2006年7月(夏季),10月(秋季)和2007年3月(春季)的现场调查数据,对珠江口及毗邻海域中的营养盐和叶绿素a等环境生态因子的时空分布特性进行了对比分析,研究了氮磷比与叶绿素a含量和种群多样性之间的联系,探讨了该海域营养盐对于浮游植物生长的影响。结果表明:(1)研究海域营养盐表现出较强的季节和空间差异性,总氮(TN)和总磷(TP)浓度均值春季(1.545 mg/L、0.056 mg/L)和夏季(1.570 mg/L、0.058 mg/L)均大于秋季(1.442 mg/L、0.034 mg/L),且春夏季浓度空间差异更明显。(2)调查期间海域营养盐含量超标现象突出,夏季尤为明显。无机氮(DIN)总体均值0.99 mg/L,超四类海水标准限值1倍,活性磷酸盐(PO4-P)总体均值0.021 mg/L,DIN∶PO4-P平均值为130;叶绿素a浓度与营养盐、p H、温度有较显著的相关性。(3)叶绿素a浓度较高的站位,具有较高的DIN∶PO4-P值,但浮游植物多样性指数偏低,优势种明显,主要为中肋骨条藻。氮磷比的改变会影响不同生长特性的浮游植物间的竞争和种群结构的改变;今后海洋污染治理中,在控制氮、磷污染时要注意氮磷比的改变可能造成的浮游生态影响。     

连续可调式沉水植物网床对河道水质的修复

在太湖贡湖水源保护区陆域的一条长约200 m的污染河道内构建了一系列连续可调式沉水植物网床,形成了以菊花草、苦草、伊乐藻、轮叶黑藻和菹草等沉水植物构成的水生植物群落;跟踪监测了总氮(TN)、铵态氮(NH4 +-N)、亚硝态氮(NO2--N)、硝态氮(NO3--N)、总磷(TP)和磷酸盐(PO43--P)等水质指标,分析沉水植物网床引导沉水植被恢复对污染河道的水质修复效果.结果表明:沉水植被网床构建后,水体透明度显著升高,由修复前的0.5m提高到1.7 ～1.8 m;在沉水植被网床构建后的第5天和第20天,TN和TP的削减率分别为35.6％、66.3％和29.4％、63.2％;5个月后,修复河道水体内NH4+-N、NO2--N、NO3--N、TN、PO43--p和TP的浓度比对照组显著降低,削减率分别达到92.4％、76.8％、72.7％、73.9％、90.5％和92.0％.由连续可调式沉水植被网床引导恢复的水生植物群落可用于河道,特别是陆域浅水污染水体的生态修复.     

不同近地表土壤水文条件下雨滴打击对黑土坡面养分流失的影响

目前,土壤水分饱和和壤中流条件下,雨滴打击对养分流失的影响尚不清楚.通过3个近地表土壤水文条件(自由入渗、土壤水分饱和与壤中流)下,土槽上方架设与不架设尼龙纱网模拟降雨对比试验,研究雨滴打击对黑土坡面侵蚀过程及NO3-N、NH4-N与PO4-P随径流和侵蚀泥沙迁移的影响.结果表明,纱网覆盖消除雨滴打击后坡面侵蚀量和泥沙浓度分别减少59.4％-71.6％和57.3％ -73.0％,不同水文条件下减少量的排序为:自由入渗＞壤中流＞土壤水分饱和.消除雨滴打击后养分随径流流失的减少仅在自由入渗条件下体现较明显,该水文条件下NO3-N、NH4-N与PO4-P流失分别减少33.3％、23.1％和40.7％;3种水文条件下,消除雨滴打击均明显减少养分随泥沙的流失,其中自由人渗条件下减少效果最明显,该水文条件下,NO3-N和NH4-N流失分别减少20.9％ -54.9％和25.0％ -62.3％,而PO4-P流失减少在74.6％以上.雨滴打击增大了NO3-N的淋失,但对NH4-N与PO4-P的淋失几乎无影响.消除雨滴打击后,自由人渗条件下养分的等效径流迁移深度减少26.7％-42.6％,而土壤水分饱和与壤中流条件下基本无变化.以上研究结果为有效防治坡面土壤侵蚀和农业非点源污染提供科学理论依据,尤其是在壤中流出现的地方.     

三峡水库蓄水前后香溪河氮磷污染状况研究

分别于三峡水库蓄水前的上世纪1996—1997年及蓄水后的2004年采集了香溪河水样及沉积物样,研究了蓄水前后香溪河氮磷的污染状况。结果表明,蓄水前上游总磷浓度低于0.05mg/L,下游在0.22—0.34mg/L之间,其浓度与生活污水及工业废水排放有关;总氮浓度变化不大,在0.7—1.1mg/L之间。蓄水后磷、氮浓度明显升高,但总磷在回水区由于沉降作用反而低于蓄水前。蓄水后下游氮磷比普遍高于10,加之水流变缓,使香溪河库湾发生“水华”的可能性增加。香溪河沉积物磷污染严重,总磷含量高达1221mg/kg,主要以无机磷污染为主。三峡水库蓄水后,对上游库湾水环境的不利影响已开始显现出来,必须采取有效措施,防止水环境的恶化。     

反硝化除磷菌筛选及其特性研究

【目的】研究反硝化除磷菌特性。【方法】通过微生物筛选和生物学特性研究方法,从对虾养殖池塘中筛选出多株可在有氧条件下同时具有反硝化除磷功能的菌种。【结果】菌株LY-1可在18 h内将初始量为10 mg/L的亚硝酸盐氮降低至0.04 mg/L,PO43?-P降低至0.05 mg/L。在DO浓度为5.0?5.9 mg/L时,该菌反硝化除磷率近100%。试验选取具有反硝化除磷功能的枯草芽孢杆菌为阳性对照菌,大肠杆菌为阴性对照菌,比较研究了菌株LY-1在不同pH、温度、盐度、PO43?-P浓度、亚硝酸盐浓度时反硝化除磷的强弱,在pH为5?9范围时,该菌亚硝酸盐氮去除率近99%,PO43?-P去除率86%;温度为30°C时,该菌反硝化除磷率近100%;盐度为5‰?15‰、PO43?-P浓度为10 mg/L、亚硝酸盐氮浓度为20 mg/L时,该菌亚硝酸盐氮和PO43?-P去除率均可达99%。【结论】菌株LY-1反硝化除磷性能显著高于对照菌(P<0.05)。通过菌株LY-1形态学观察、生理生化及16S rRNA基因序列分析,初步鉴定为蜡样芽孢杆菌(Bacillus cereus)。     

大亚湾大鹏澳水域春季浮游植物优势种的演替

根据2002年4月28日～5月27日大亚湾大鹏澳内每日采样的现场连续观测资料,使用主分量分析方法和多元回归方法,分析浮游植物优势种类之间的关系及影响其生长与演替的主要理化因子,建立春季浮游植物优势种类的演替模型。模型表明,中肋骨条藻和柔弱菱形藻之间为竞争关系;与浮游植物(以硅藻为主)生长密切相关的理化因子为温度(T)、溶解氧饱和度(DOsat)、铵氮(NH4-N)、亚硝酸氮(NO2-N)、磷酸盐(PO4-P)、硅酸盐(SiO3-Si)。影响中肋骨条藻的理化因子还有盐度(S)和氮磷比值(NO3／PO4)。并根据优势种类发生演替期间的环境变化(降雨),分析了浮游植物优势种由中肋骨条藻演替为柔弱菱形藻的过程。     

真江蓠(Gracilaria verrucosa)对网箱养殖海区的生态修复及生态养殖匹配模式

2006年8～9月,在浙江象山港花鲈(Lateolabrax japonicus)养殖网箱中吊养真江蓠(Gracilaria verrucosa)对网箱养殖造成的水体富营养化进行生态修复研究.通过45d内的平面监测、定点跟踪监测和断面监测,结果表明:该网箱养殖区水体呈严重富营养化状态,营养状态指数(E)为32.00,其营养盐分布由高浓度的中心区向周围150m非养殖水域扩散;真江蓠对养殖区的富营养化海水具有较好的修复效果:江蓠生态修复区及其相邻网箱中水体PO4-P、NO2-N、NH4-N和NO3-N含量显著低于非修复区(P＜0.01),修复区海水PO4-P、NO2-N、NH4-N和NO3-N浓度比非修复区分别降低22%～58%、24%～48%、22%～61%和24%～47%.养殖真江蓠45d后,修复区水体DO浓度和透明度显著高于非修复区(P＜0.05),DO平均提高28%,透明度平均提高30%;而修复区水体Chl-a浓度显著低于非修复区(P＜0.05),平均降低49%.通过建立基于N平衡的鱼藻生态养殖模式,每收获1kg花鲈至少需要匹配江蓠4.7 kg wet wt才可实现对鱼类排放N的完全吸收.因此网箱内栽培江蓠的混合生态养殖模式,可平衡因经济动物养殖所带来的额外营养负荷,有利于实现动物养殖环境的自我修复.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.