Comparison of life-history parameters and effectiveness in competition with Moina macrocopa between two Keratella tropica morphs     

《Limnologica》2020

Competition and predation are the two major biotic interactions in zooplankton community. Various rotifer species exhibit polymorphism in lorica and spine morphology in the presence of predators and competitors, which effectively increases their defence competition capacity. This study compared life-history parameters between long-spined morph (LSM) and short-spined morph (SSM) of Keratella tropica at three temperatures. The results showed that both morphs showed significantly higher intrinsic rate of population increase at 25 °C than those at 20 °C and 30 °C. The intrinsic rate of population increase was significantly lower in LSM than SSM at 25 °C and 30 °C, and the net reproductive rate was significantly lower in LSM than SSM at 30 °C. These results suggested that K. tropica had cost on development of long spines, which, however, was dependent on temperature. Moreover, the competition outcome of LSM and SSM with Moina macrocopa were investigated at three densities of Scenedesmus obliquus (0.5 × 10⁶, 1.0 × 10⁶ and 2.0 × 10⁶ cells/mL) and three initial densities of M. macrocopa (0.1, 0.3 and 0.9 ind./mL), revealing that both LSM and SSM populations decreased significantly at all tested algal densities and Moina levels. LSM showed higher population growth rate than SSM at lower algal density (0.5 × 10⁶ cells/mL) and higher Moina densities (0.3 and 0.9 ind./mL), which suggested that LSM could be more effective to defend M. macrocopa. Three-way analysis of variance showed no significant effects of algal density on population growth rate of K. tropica, but interaction between algal density and M. macrocopa density significantly affected its population growth rate.  相似文献   

Cover crops and precipitation influence soluble reactive phosphorus losses via tile drain discharge in an agricultural watershed     

Matt T. Trentman  Jennifer L. Tank  Todd V. Royer  Shannon L. Speir  Ursula H. Mahl  Lienne R. Sethna 《水文研究》2020,34(23):4446-4458

Subsurface tile drainage speeds water removal from agricultural fields that are historically prone to flooding. While managed drainage systems improve crop yields, they can also contribute tothe eutrophication of downstream ecosystems, as tile-drained systems are conduits for nutrients to adjacent waterways. The changing climate of the Midwestern US has already altered precipitation regimes which will likely continue into the future, with unknown effects on tile drain water and nutrient loss to waterways. Adding vegetative cover (i.e., as winter cover crops) is one approach that can retain water and nutrients on fields to minimize export via tile drains. In the current study, we evaluate the effect of cover crops on tile drain discharge and soluble reactive phosphorus (SRP) loads using bi-monthly measurements from 43 unique tile outlets draining fields with or without cover crops in two watersheds in northern Indiana. Using four water years of data (n = 844 measurements), we examined the role of short-term antecedent precipitation conditions and variation in soil biogeochemistry in mediating the effect of cover crops on tile drain flow and SRP loads. We observed significant effects of cover crops on both tile drain discharge and SRP loads, but these results were season and watershed specific. Cover crop effects were identified only in spring, where their presence reduced tile drain discharge in both watersheds and SRP loads in one watershed. Varying effects on SRP loads between watersheds were attributed to different soil biogeochemical characteristics, where soils with lower bioavailable P and higher P sorption capacity were less likely to have a cover crop effect. Antecedent precipitation was important in spring, and cover crop differences were still evident during periods of wet and dry antecedent precipitation conditions. Overall, we show that cover crops have the potential to significantly decrease spring tile drain P export, and these effects are resilient to a wide range of precipitation conditions.  相似文献   

中国泥炭矿成矿规律与开发利用   总被引：1，自引：0，他引：1  

饶娇萍  贾沁贤  王登红  刘丽君  代鸿章  郭唯明 《地质学报》2020,94(1):192-203

泥炭是具有重要意义的新兴产业矿产，是传统矿产向新兴产业矿产“华丽转身”的典型。全球泥炭资源的总量约为5000亿吨，我国的泥炭资源总量仅为124. 96亿吨，资源量较为丰富，质量中等，但需要量在上升。我国泥炭的分布具有普遍性和不均匀性，成矿时代为第四纪(全新世)，更早的泥炭多已经历成煤的早期阶段而转变为褐煤。我国的泥炭矿床类型主要以富营养草本泥炭为主，木本为辅，藓类泥炭次之。本文在对1988年全国泥炭报告中罗列的5719处泥炭矿产地进行梳理的基础上，总结其成矿规律，根据资源规模厘定出5个大型矿集区，7个中小型矿集区，3个大型预测区，为泥炭勘查工作提供依据。离最近一次全国泥炭资源调查已30年，多处泥炭地由于全球气候变化、城市化发展等原因而消失，非常有必要重新评估。需要强调的是，泥炭的用途已经不再是“燃料”矿产，不再主要用于取暖，而在节能环保、生物等战略性新兴产业中发挥特殊作用，故应该从生态文明建设、碳汇、环境保护、生物技术等角度创新定位其功能和用途。鉴于泥炭的新用途及其利用趋势，《中国矿产地质志》编委会建议将其定位为非金属矿产而非“能源”矿产，据此提出开发利用建议。  相似文献   

中蒙边界地区汇水域沉积物69种元素的背景值     

刘汉粮  聂兰仕  SHOJIN Davaa  王学求  迟清华 《地学前缘》2020,27(3):202-221

中蒙边界地区成矿地质条件优越,是世界上重要的金属成矿省和全球3大斑岩型铜(金、钼)成矿带之一,资源潜力巨大。中蒙合作1∶100万地球化学填图采集了海量的地球化学数据,为研究该地区元素分散富集、成矿趋势、资源评价和环境变化提供基础数据,为“一带一路”资源布局提供决策依据。以X±3S为临界值一次性剔除离群值后的数据集的中位值作为背景值的估计值,计算了中蒙边界地区12个Ⅱ级构造单元和5个Ⅱ级成矿省的汇水域沉积物69种元素背景值,探讨了中蒙边界地区汇水域沉积物69种元素背景值的区域分布规律和特征。研究表明不同的地质背景导致元素的地球化学分布模式不同,不同构造单元具有显著差异的元素地球化学特征,元素的海量聚集为大型矿床的形成提供了充足的元素供给,形成特定的地球化学省。这些背景值为进一步深入开发利用中蒙边界地球化学填图数据提供了可供对比的基础数据。  相似文献   

On the morphology of radial sand ridges     

Weina Zhang  Xiaohe Zhang  Huiming Huang  Yigang Wang  Sergio Fagherazzi 《地球表面变化过程与地形》2020,45(11):2613-2630

We use a hydrodynamic model applied to an idealized fan-shaped basin to explore the morphology and dynamics of radial sand ridges in a convergent coastal system. A positive morphological feedback between channel incision and flow redistribution is responsible for the formation of the channel-ridge pattern. The selection mechanism of bottom wavelength is associated with flow concentration in the deeper part of the channels. Our results are compared to sediment and hydraulic dynamics in the radial sand ridges (RSRs) in China. In a convergent, sloping basin the tangentially averaged tidal velocity peaks at 47 km from the apex. This distance is similar to the arc distance, 62 km, where the RSRs are most incised. An offshore shift in tidal phase results in stronger flows near the north coastline, explaining the presence of asymmetric channel patterns. A numerical stability analysis indicates that small radial oscillations with a wavelength of 10° to 15° maximize the velocity in the troughs. This oscillation wavelength also emerges in the RSRs, which display a peak in spectral energy at a radial wavelength between 25° to 37.5°. High-resolution numerical simulations in the RSRs confirm that flow concentration occurs in the deeper part of the channels, keeping them flushed. We therefore conclude that the RSRs display morphometric characteristics similar to other tidal incisions, like tidal inlets and intertidal channels. This result further supports the dominant role of tidal prism and related peak velocities in incising coastal landscapes. © 2020 John Wiley & Sons, Ltd.  相似文献   

波浪作用下沉积物中氮、磷释放速率的试验研究     

张严严  房文艳  许国辉  任宇鹏  许兴北 《中国海洋大学学报(自然科学版)》2020,50(4):102-110

湖泊或海湾中的沉积物吸附氮(N)、磷(P)等元素所形成的沉积层成为水体富营养化的內源。在波浪作用下,尤其是强浪作用下,沉积物中的N、P会通过内源释放作用大量进入水体中。本文在自制的U型水槽中开展实验,采用不同水头差来模拟波浪的循环荷载作用,研究了沉积层中的N、P在静置固结状态(Ⅰ)、加波未液化状态(Ⅱ)、加波液化状态(Ⅲ)下的释放规律,并给出该试验条件下的沉积物释放速率的拟合方程。试验结果表明:沉积物中总氮(TN)和溶解性总氮(TDN)的释放速率会随着水动力作用的增强而增加;总磷(TP)、溶解性总磷(TDP)和活性磷酸盐(SRP)的释放速率也随着水动力作用增强而增加,但水体中悬浮物(SS)含量过高会限制其释放速率。  相似文献   

车辆碾压作用下戈壁地表起尘浓度   总被引：1，自引：1，他引：0  

孟小楠  严平  王振亭  董苗  王勇 《中国沙漠》2019,39(1):80-87

通过野外观测车辆碾压作用下戈壁地表PM₁₀释放浓度，探讨其主要影响因素。针对戈壁区砾石、砂砾、砂质和砂土4种路面类型，应用TSI粉尘仪多次重复观测车辆碾压产生的PM₁₀浓度，进而阐明碾压次数、车速和地表水分等因素对起尘浓度的影响。结果表明：4种路面的平均起尘浓度依次为5.339、9.089、16.944、50.251 mg·m^-3，是自然状态下的5~50倍；起尘浓度随碾压次数增多而增大，其中砂土路情况下的增长最显著；随土层厚度的增大呈现出幂函数的增长趋势；降雨后路面起尘浓度显著减小，且降雨量会影响降雨后起尘浓度的变化趋势。最后提出了针对性的建议和措施以减弱车辆碾压导致的戈壁地表起尘。  相似文献   

臭氧及臭氧类高级氧化技术降解甲基对硫磷的效能          下载免费PDF全文

林存旺  许珊珊  项丰云  章小芳 《海洋开发与管理》2018,35(9):94-99

文章研究了臭氧及臭氧类高级氧化技术(AOPs-O3)在不同pH条件下降解甲基对硫磷(MP)的效能。结果表明,在pH 3~10的条件下(反应过程控制pH),单独臭氧化5min即可完全降解MP,但不同pH下化学耗氧量(COD)和有机磷的释放率差异明显。在pH为3.3,7.5和9.4的条件下单独臭氧30min后COD的去除率分别为55.17%,89.64%和93.10%,有机磷的释放率分别为16.33%,95.00%和99.99%。考虑酸性条件下可以规避碳酸盐的负面影响(特别是高浓度废水),利用O3/H2O2/Ti(IV)在pH 3.3条件下处理MP溶液,COD去除率和有机磷释放率分别达到89.64%和81.57%。相对法计算求得MP与O3和羟基自由基(·OH)的速率常数分别为31.98L·(mol·s)-1和7.488×109 L·(mol·s)-1。活性污泥法的测试结果表明,MP经O3/Ti(IV)/H2O2(pH=3.3)和O3(pH=9.4)可提升含MP废水的可生化性,但与培养液体系相比仍具有一定的毒性。  相似文献   

KK型管节点应力集中系数几何敏感性分析     

林海花  孙承猛  石强 《海洋工程》2020,38(6):142-150

KK型管节点是自升式平台桁架式桩腿中的一种管节点，其应力集中系数是影响桩腿疲劳寿命的重要参数。应力集中系数与管节点的几何形式密切相关，为分析KK型管节点应力集中系数对几何参数的敏感性，利用ANSYS软件对某KK型管节点进行几何参数化建模，利用有限元数值模拟方法对各工况下的热点应力进行分析，并分别计算各相应工况下的名义应力，然后将热点应力与名义应力相比得到不同几何参数下的热点应力集中系数。对计算结果进行整理分析，得到了KK型管节点应力集中系数对无量纲几何参数的敏感性规律。结果表明，应力集中系数与撑杆受力状态、管节点结构形式有关，在满足结构布置、建造工艺和其他安全性指标的前提下，分析结果能够为KK型管节点的结构设计和疲劳分析提供技术支撑。  相似文献   

长白山天池火山天文峰期黄色浮岩成因研究     

潘波  程滔  徐丹  刘松军 《岩石学报》2020,36(7):2067-2080

长白山天池火口北侧天文峰之上,一套醒目的黄色浮岩引起广泛的关注,其颜色成因问题更是讨论的热点。本文通过野外地质调查、显微形貌和地球化学分析等方法,探索了黄色浮岩的颜色成因问题,并对此次喷发活动(天文峰期喷发)有了更进一步的认识。黄色浮岩与其下部灰白色浮岩应为同一期喷发所形成,两者成分一致且特征相似。黄色浮岩初始颜色为灰白色,后期受所处环境(降水丰富)与本身气孔特征的影响,浮岩内发生了元素析出和元素沉淀的过程。首先,浮岩内Si与H2O结合形成弱硅酸(H2Si O3),而大气中CO2与H2O结合形成弱碳酸(H2CO3),在弱酸环境下火山玻璃逐渐析出Si、K、Al、Ca和Fe等阳离子,而析出的元素易溶于水的部分被流水带走,难溶于水的Fe与Al富集并粘附在火山玻璃壁上,同时由于Fe可与H2O络合形成黄色的Fe的水合物(Fe2O3·n H2O),而Al与H2O络合形成凝胶状白色水合物(Al2O3·n H2O),两者混合形成了黄色胶状物粘附在火山玻璃壁上,改变了浮岩原本的灰白色,形成了黄色浮岩。因此,天文峰期浮岩的黄色是由于后期风化淋滤作用所造成,属于次生色。本研究提高了对火山喷发堆积物风化淋滤作用过程的认识,也为其他地区相似颜色变化问题的讨论提供了借鉴。  相似文献