淡水中对紫外光敏感的磷化合物研究简述     

周易勇  付永清  李建秋 《湖泊科学》2000,12(2):178-181

湖泊、沼泽与河流等淡水生态系统中在的一些对紫外光敏感的磷化合物,它们在紫外光（或太阳光）的作用下释放正磷酸根。本文对其形成释放机制、生态学意义以及铁和腐殖质的调节作用等作了扼要的综述。  相似文献   

Agonistic interactions and dominance establishment in three crayfish species non-native to Europe     

《Limnologica》2019

Ecosystems increasingly face concurrent invasions by multiple species, but knowledge about relationships among invasive species is under studied. We examined agonistic encounters among signal crayfish Pacifastacus leniusculus, marbled crayfish Procambarus virginalis, and the common yabby Cherax destructor, none native to Europe, to assess the influence of aggression on their success in a sympatric environment. In interspecific interactions, similar-sized signal crayfish were significantly more likely to initiate aggressive encounters and won significantly more fights against similar-sized opponents. The marbled crayfish was the least aggressive and least successful in agonistic interactions. The mean number of fights, fight duration, and number and duration of low and high intensity fights varied significantly between intra- and inter-specific interactions, tending to be more pronounced in conspecific encounters. We concluded that crayfish species differ in fighting strategies employed during intra- and inter-specific interactions. Of the species evaluated, the signal crayfish shows the highest potential to establish dominance. However, factors such as growth rate, reproductive potential, ecosystem variables, and temperature of habitat may alter the competitiveness of an invader.  相似文献   

Origin and chemical and isotopic evolution of dissolved inorganic carbon (DIC) in groundwater of the Okavango Delta,Botswana     

Rawlings N. Akondi  Loago Molwalefhe 《水文科学杂志》2019,64(1):105-120

The origin and the chemical and isotopic evolution of dissolved inorganic carbon (DIC) in groundwater of the Okavango Delta in semi-arid Botswana were investigated using DIC and major ion concentrations and stable oxygen, hydrogen and carbon isotopes (δD, δ¹⁸O and δ¹³C_DIC). The δD and δ¹⁸O indicated that groundwater was recharged by evaporated river water and unevaporated rain. The river water and shallow (<10 m) groundwater are Ca–Na–HCO₃ type and the deep (≥10 m) groundwater is Na–K–HCO₃ to HCO₃–Cl–SO₄ to Cl–SO₄–HCO₃. Compared to river water, the mean DIC concentrations were 2 times higher in shallow groundwater, 7 times higher in deep groundwater and 24 times higher in island groundwater. The δ¹³C_DIC indicate that DIC production in groundwater is from organic matter oxidation and in island groundwater from organic matter oxidation and dissolution of sodium carbonate salts. The ionic and isotopic evolution of the groundwater relative to evaporated river water indicates two independent pools of DIC.  相似文献   

微塑料与水中污染物的联合作用研究进展   总被引：1，自引：0，他引：1  

张哿  邹亚丹  徐擎擎  王宇擎  刘成  李锋民 《海洋湖沼通报》2019,(2):59-69

微塑料(直径<5mm的塑料)因其吸附、迁移性能和生物毒性成为目前研究的热点。微塑料进入水体后,会与水中的持久性污染物和重金属进行相互作用,与它们单独作用于生物的毒性效应不同。本文从微塑料对污染物的富集、迁移以及微塑料与污染物的联合毒性效应方面,对微塑料与污染物的联合作用进行了总结。环境中的微塑料能通过吸附作用富集水中有机污染物和金属离子,该过程主要受微塑料自身性质、塑料的老化程度、污染物的空间分布和其他环境条件的影响。污染物能以微塑料为载体在环境和生物体间迁移,包括空间上的转移和生物体内的转移。微塑料与污染物联合作用于生物体时,会通过增加摄入浓度、加剧组织损伤和降低机体抗性等方式增强污染物对生物体的毒性效应,或者通过降低污染物接触浓度、污染物或共污染物的生物可利用性减缓污染物对生物体的毒性效应。未来应对微塑料的吸附行为、相互作用机制以及评价方法、生物积累和慢性毒性进行探究。  相似文献   

养护期介入电迁阻锈保障混凝土耐久性试验研究     

吴凯  罗林  毛江鸿  金伟良  潘崇根  樊玮洁 《海洋工程》2019,37(4):117-123

沿海地区氯盐侵蚀会对混凝土结构造成严重的耐久性问题,混凝土设计使用寿命难以保障。对于新建工程,若在自由水含量较高混凝土养护期进行电迁阻锈处理,则有利于电迁移性阻锈剂在钢筋周围聚集以达到更佳的阻锈效果。为此,针对两种电迁移性阻锈剂对处于氯盐侵蚀环境中的混凝土适用性展开研究,并测试了干湿循环前后混凝土内钢筋电化学参数、氯离子扩散特征及钢筋周围电迁移性阻锈剂含量研究两种电迁移性阻锈剂对混凝土耐久性保障的作用。结果表明,试验中养护期介入电迁阻锈后试件阻锈效果良好,经过干湿循环后钢筋腐蚀电位正向高于-162.6 m V,同时,钢筋附近出现明显的阻锈剂聚集现象,能保持钢筋的钝化状态。  相似文献   

Getting by: The ethnomethods of everyday cycling navigation     

Michael Lloyd 《New Zealand geographer》2020,76(3):207-220

Cycling is often carried out in public places, meaning that it is easy to both observe and video-record cycling in action. Within sociology, ethnomethodology focuses on practical activities, often by collecting and analysing video data. Geographers have also used video data in researching cycling, but the two perspectives have little crossover. This article showcases an ethnomethodological analysis of video data on everyday cycling navigation, presenting three empirical examples. We see that cycling, accomplished by real interacting people, needs analysing in fine detail. Further knowledge of the mundane aspects of cycling mobility can usefully build upon such a videographic approach.  相似文献   

江汉盆地始新世中、晚期气候变化周期性的孢粉学证据   总被引：6，自引：0，他引：6  

童国榜  贾秀梅  郑绵平  袁鹤然  刘俊英  王伟铭 《地球学报》2002,23(2):159-164

采用时间序列分析方法对江汉盆地明钾1孔的孢粉数据进行了处理，发现在中、晚始新世时期孢粉植物群的波动存在各种周期成分。长周期有1.2Ma、2.0Ma及5.0Ma，中周期有0.2Ma、0.4Ma、0.6Ma、0.8Ma，其中1.2Ma及0.2Ma、0.4Ma、0.6Ma的周期成分在第四纪孢粉植物群的演化中也存在，且与8.0Ma B.P.以来的构造气候旋回，亚旋回的准1.2Ma及0.4Ma周期相一致。这表明地球运动轨道变化对气候的制约作用由来已久。该孔孢粉时间序列的趋成分显示最少有4个水平，反映了孢粉植物群演化的4个阶段。曲线还揭示36Ma B.P.前后的波动周期及振幅都有明显的变异，可能预示了一次大的环境变革。这一变化在很大程度上与喜马拉雅一期运动和地球南半球一次大的海洋和气候变冷事件相吻合。  相似文献   

俯冲带中水流体的化学性质研究进展     

邓鹤鸣  苏根利  李和平  代立东  孟宪武 《矿物岩石地球化学通报》2006,25(2):189-195

俯冲带中的水在壳幔演化和物质交换中起重要作用。本文就俯冲带中水的物理化学性质、溶液中的离子缔合、混溶、主量元素与微量元素组成等方面进行了阐述。重点剖析:1)超临界态下温度压力条件的改变导致水微观结构与性质的变化,扩散系数、粘度等性质随之改变,进而对水岩反应产生影响;2)富水流体中离子缔合影响着金属配合物数量,很大程度制约流体中矿物的溶解行为;3)低Cl流体中微量元素配分模式与岛弧玄武岩类似,意味着富水贫氯碱性硅酸盐成分的流体在地幔楔元素运移中起关键作用。并展望了俯冲带中流体化学性质研究的新手段。  相似文献   

长江口盐沼滩面发育对有机碳深度分布的制约   总被引：1，自引：0，他引：1  

陈庆强  孟翊  周菊珍  顾靖华  胡克林 《地球科学进展》2007,22(1):26-32

通过对长江口崇明东滩高潮滩、中潮滩以及光滩柱状样的有机碳含量与碳稳定同位素组成（δ13C）、粒度组成等的测定,研究盐沼有机碳深度分布特征与形成机制。结果表明,盐沼土壤颗粒有机碳（POC）主要赋存于粒径小于0.016 mm的颗粒中,POC含量对粒径在0.002~0.004 mm区间的颗粒含量变化最敏感,说明盐沼POC主要来自长江径流悬移质,这与有机碳稳定同位素结果一致。土壤POC含量与不同粒径区间颗粒含量相关关系表明,高潮滩与中潮滩柱样的泥沙级配较为接近;光滩柱样POC含量与不同粒径区间颗粒含量相关关系特征与高、中潮滩柱样的基本类似,主要不同表现在粒径大于0.016 mm的粗颗粒,这很可能受控于盐沼不同高程部位动力沉积过程。盐沼植被对高、中潮滩柱样POC的贡献相当可观,个别层段高达55.6%;植被对土壤POC的贡献受到滩面过程的明显制约。滩面动力沉积过程形成盐沼垂向上独特的沙、泥纹层构造,其优良的封堵效能显著影响土壤有机碳的垂向分布。盐沼滩面动力沉积过程是塑造有机碳深度分布特征的关键因素。  相似文献   

Evaluation of nitrogen cycling associated with agricultural production and environmental load in a mountain region,in Hokkaido,Japan     

Lei Liang  Datian Jin  Ning Hu 《山地科学学报》2008,5(2):130-139

This study examined the nitrogen cycling associated with agricultural production and environmental load in central Hokkaido. The nitrogen （N） budget analysis model offers a new set of tools for evaluating N cycling in agro-ecosystems. The cycling index （CI） is a useful tool for estimating optimal N flows in farmlands. The fertilization index （FI） is a useful indicator for characterizing the N flows related to farms. Using these parameters, we analyzed all farm systems to estimate the optimal N cycling for minimizing N pollution in groundwater and maximizing agricultural production in mountain regions of Japan. The results showed that the critical N application rate （chemical fertilizer ＋ manure） was 143.3 kg N ha^-1 y^-1. The critical inter-system input （chemical fertilizer N, imported food and feed N, and natural supplied N） was 169.2 kg N ha^-1y^-1.  相似文献