Bathymetric segregation of sea urchins on reefs of the Canarian Archipelago: Role of flow-induced forces

We examined whether adults of three species of sea urchins species (Diadema antillarum, Arbacia lixula, and Paracentrotus lividus) exhibit a consistent depth-dependent partitioning pattern on rocky reefs of the Canarian Archipelago (eastern Atlantic). Hydrodynamic experiments were carried out to quantify the resistance to flow-induced dislodgement in these three species. We tested the model that different morphology can result in habitat partitioning among these sea urchins. Abundances of D. antillarum increased with depth. In contrast, A. lixula and P. lividus showed the opposite zonation pattern, coexisting in high abundances in the shallowest depths (<5 m), and occurring in low densities in the deepest part of reefs (>7 m). Both A. lixula and P. lividus had greater adhesion-surface to body-height ratios than D. antillarum. Similarly, A. lixula and P. lividus showed a greater ability to resist flow-induced dislodgement compared with D. antillarum. The mean “velocity of dislodgement” was 300% and 50% greater for A. lixula and P. lividus, respectively, relative to D. antillarum, for any particular size. As a result, A. lixula and P. lividus are better fitted to life in high-flow environments than D. antillarum. We conclude that the risk of dislodgement by water motion likely play a relevant role in the vertical distribution patterns of these sea urchins in the eastern Atlantic.     

Detecting multi-scale urban growth patterns and processes in the Algarve region (Southern Portugal)

The importance of urban growth processes and their spatial characteristics has led to a growing interest in monitoring these phenomena. Spatial metrics are widely employed for this purpose, appearing in an increasing number of studies where they are used to characterise growth patterns and their evolution over time. This paper presents an analysis of urban growth patterns using spatial metrics in the Algarve (southern Portugal), an area of considerable urban dynamics associated with tourism. Two datasets were used (CORINE 1:100,000 maps and COS 1:25,000 maps) and two time periods (1990 and 2006–2007) in order to compare the different urban land use patterns detected and their evolution over time. The results show differences in urban land use patterns and associated processes at each scale, with stable land use patterns predominating at the 1:100,000 scale whereas the 1:25,000 scale showed a move towards more dispersed patterns. These results have enabled an assessment of the principal differences in urban growth patterns observed at both scales, and the implications for planning these entail.     

镇江雷暴气候特征及天气学预报方法分析

雷暴是严重的气象灾害之一,给人民生命财产带来严重影响。雷暴的发生发展地域性强,因此加强镇江本地雷暴特征的研究和预警工作十分必要。利用镇江市1959--2010年的雷暴气候资料,通过气候倾向率、小波分析等统计方法,对其周期性、时空分布特征及年（代）际、季节变化特征等进行了分析,得出以下结论：1）镇江市雷暴呈现出市区少、周边地区多的特点,其中句容雷暴发生频率最多且持续时间长。2）镇江市平均雷暴日数存在4a、6a、10～12a左右、准20a的长周期振荡信号。从长周期分析,镇江市近几年的年平均雷暴日数处于偏多周期时段。3）年平均雷暴日数距平,20世纪60年代、70年代、21世纪的00年代是正距平,特别是2006--2010年连续5a的平均雷暴日数都大于气候值,是雷暴频发时期;80年代、90年代为负距平。1963年的雷暴日数最多,有53．3天;1979年的最少,为15天。通过对1999--2008年镇江市地面观测资料的194个雷暴天气过程个例进行统计分析,对影响镇江市的雷暴天气系统进行了分型,在此基础上提出了预报镇江市雷暴天气的思路,为开展雷暴预报预警业务提供理论依据。     

Biogeochemical patterns in the Atlantic Inflow through the Strait of Gibraltar

The effects of tidal forcing on the biogeochemical patterns of surface water masses flowing through the Strait of Gibraltar are studied by monitoring the Atlantic Inflow (AI) during both spring and neap tides. Three main phenomena are defined depending on the strength of the outflowing phase predicted over the Camarinal Sill: non-wave events (a very frequent phenomenon during the whole year); type I Internal wave events (a very energetic event, occurring during spring tides); and type II Internal wave events (less intense, occurring during neap tides).During neap tides, a non-wave event comprising oligotrophic open-ocean water from the Gulf of Cádiz is the most frequent and clearly dominant flow through the Strait. In this tidal condition, the inflow of North Atlantic Central Water (NACW) provides the main nutrient input to the surface layer of the Alboran Sea, supplying almost 70% of total annual nitrate transport to the Mediterranean basin. A low percentage of active and large phytoplankton cells and low average concentrations of chlorophyll (0.3–0.4 mg m⁻³) are found in this tidal phase. Around 50% of total annual phytoplankton biomass transport into the Mediterranean Sea through the Strait presents these oligotrophic characteristics.In contrast, during spring tides, patches of water with high chlorophyll levels (0.7–1 mg m⁻³) arrive intermittently, and these are recorded concurrently with the passage of internal waves coming from the Camarinal Sill (type I internal wave events). When large internal waves are arrested over the Camarinal Sill this implies strong interfacial mixing and the probable concurrent injection of coastal waters into the main channel of the Strait. These processes result in a mixed water column in the AI and can account for around 30% of total annual nitrate transport into the Mediterranean basin. Associated with type I internal wave events there is a regular inflow of large and active phytoplankton cells, transported in waters with relatively high nutrient concentrations, which constitutes a significant supply of planktonic resources to the pelagic ecosystem of the Alboran Sea (almost 30% of total annual phytoplankton biomass transport).     

斑岩-浅成低温热液型Cu-Au矿H2O-Cl-S流体性质和演化方式对成矿的制约

斑岩—浅成低温热液型Cu—Au成矿流体最具代表性的是H2O—Cl—S流体。流体的性质强烈控制着Cu、Au的成矿行为,包括溶解性、迁移形式和气—液分配。流体的氧逸度和流体中Cl、S物种相对含量决定金属在流体中的溶解形式,高氧逸度的高温高盐度流体中Cu、Au主要和Cl络合,S-3也可能是促进Au溶解的重要S物种形式。而过量的S有利于Cu、Au等元素以含S离子络合物进入液相流体,与含S中性络合物配分进入气相流体并迁移Au至浅成低温热液环境形成矿床。岩浆需要经历充分的分异,出溶成分和性质有利于金属迁移的流体,形成高品位的斑岩型Cu、Au矿体;上覆叠加浅成低温热液型Au矿体可能需要初始的成矿流体状态进入NaCl—H2O的超临界区、有效的演化方式、良好的流体缓冲环境和有利的Au沉淀场所。相分离和流体—流体反应是沉淀斑岩—浅成低温热液型Cu—Au矿体最重要的流体演化方式。气相流体具有独特的流体性质和演化方式,可能成为十分重要的成矿流体。     

降雨类型对浅层滑坡稳定性的影响

在降雨与浅层滑坡稳定性关系的研究中, 目前的研究往往忽略了降雨类型的影响.因此, 选取4种具有代表性的降雨类型: 均匀型、递增型、递减型以及峰值型为对象, 基于Rosso提出的降雨强度与地下水关系模型, 构建考虑降雨类型的浅层滑坡地下水位高度随降雨时间的变化关系, 研究不同降雨类型对浅层滑坡地下水位变化的影响.进而, 结合无限边坡理论, 建立浅层滑坡的稳定性计算模型, 研究不同降雨类型对浅层滑坡稳定性的影响.研究结果表明: 降雨类型对浅层滑坡稳定性的影响是明显的, 递增型降雨作用下的浅层滑坡安全系数最小, 其次是均匀型降雨, 再次是峰值型降雨, 最大的是递减型降雨; 同时在确定浅层滑坡临界降雨量和进行区域浅层滑坡易发性研究时降雨类型的影响不容忽视.      

2000—2020年中国省际人口迁移格局的演化特征及影响因素

准确认识和把握21世纪前20年中国人口迁移的地理格局和影响因素,是推动新型城镇化建设及区域均衡发展的关键科学问题。借助特征向量空间滤波泊松伪最大似然估计（ESF PPML）引力模型,基于第六次和第七次全国人口普查数据、2005年和2015年全国1%人口抽样调查数据,研究了2000—2020年中国省际人口迁移的时空演化特征及影响因素。主要结论为：① 2000—2020年间人口迁移格局总体稳定,具有较强的不平衡性和网络溢出效应,大量人口从中部、西部、东北地区迁移至东部地区;② 人口迁移格局稳中有变,不平衡程度和空间集聚程度逐渐减弱,人口迁移和人口分布显现出南北分异趋势,东北地区人口迁出强度不断增强; ③ 传统引力模型因素（人口规模、地理距离）、地区社会经济发展因素（工资差异、科技教育投入占比、医疗水平）、社会网络因素、环境舒适度（PM_2.5浓度）以及生活成本（住宅价格占比）共同影响人口迁移格局;④ 区域经济差异对省际人口迁移的影响作用逐步弱化,人口迁移逐渐转变为对工资收入、高质量公共服务、环境舒适度等多因素考虑的决策过程,生活成本逐渐对人口迁移产生显著影响。     

Mapping collective human activity in an urban environment based on mobile phone data

Identifying and characterizing variations of human activity – specifically changes in intensity and similarity – in urban environments provide insights into the social component of those eminently complex systems. Using large volumes of user-generated mobile phone data, we derive mobile communication profiles that we use as a proxy for the collective human activity. In this article, geocomputational methods and geovisual analytics such as self-organizing maps (SOM) are used to explore the variations of these profiles, and its implications for collective human activity. We evaluate the merits of SOM as a cross-dimensional clustering technique and derived temporal trajectories of variations within the mobile communication profiles. The trajectories’ characteristics such as length are discussed, suggesting spatial variations in intensity and similarity in collective human activity. Trajectories are linked back to the geographic space to map the spatial and temporal variation of trajectory characteristics. Different trajectory lengths suggest that mobile phone activity is correlated with the spatial configuration of the city, and so at different times of the day. Our approach contributes to the understanding of the space-time social dynamics within urban environments.     

Microtopography,water storage and flow patterns in a fine‐textured soil under agricultural use

Agricultural use of soils implies tillage and often compaction and therefore influences processes on soil surface and affects infiltration of water into the subsoil. Although many studies on soil surface processes or flow patterns in soils exist, works relating both are rare in literature. We did two tracer experiments with Brilliant Blue FCF on a tilled and compacted plot and a non‐tilled one to investigate water storage on the soil surface during simulated rainfall and changes of soil microtopography, to analyse the associated flow patterns in the soil and to relate both to tillage and compaction. Our results show that storage was larger on the tilled and compacted plot than on the non‐tilled one. After tillage, transport processes above the plough pan were partly disconnected from those underneath because macropores were disrupted and buried by the tillage operation. However, preferential flow along cracks occurred on both plots and the macropores buried below the tillage pan still functioned as preferential flow paths. Therefore, we conclude that the studied soil is susceptible to deep vertical solute propagation at dry conditions when cracks are open, irrespective of tillage and compaction. Copyright © 2012 John Wiley & Sons, Ltd.     

Groundwater dating with 3H and SF6 in relation to mixing patterns,transport modelling and hydrochemistry

A comprehensive study of a sandy aquifer of deltaic origin in southern Poland included water chemistry, isotopes, dissolved trace gases and transport modelling. Tritium, sulphur hexafluoride (SF₆) and freons (F‐11, F‐12 and F‐113) showed the presence of modern waters in the recharge areas and shallow confined parts of the aquifer. The presence of older Holocene waters farther from the recharge areas was indicated by lack of ³H, SF₆ contents ≤0·02 fmol l⁻¹ and relatively low ¹⁴C values. The discharge from the system is by upward seepage in the valley of a major river. Pre‐Holocene waters of a cooler climate, identified on the basis of δ¹⁸O, δ²H, ¹⁴C, Ne and Ar data, were found in some distant wells. Concentrations of N₂, Ne and Ar determined by gas chromatography were used for calculating the noble gas temperatures, air excess needed for correction of SF₆, and nitrogen content released by denitrification process. The time series of ³H content available for some wells supplied quantitative information on age distributions and the total mean ages of flow through the unsaturated and saturated zones. The derived ³H age distributions turned out to be very wide, with mean values in the range of about 30 to 160 years. For each well with determined ³H age, the SF₆ data showed either a lower age range or the possibility of a lower age as expected due to shorter travel times of SF₆ through the unsaturated zone, which most probably also resulted in different types of age distributions of these tracers. Freons appeared to be of little use for individual age determinations. A quantitative estimation of two‐component mixing from SF₆ ³H relations is not possible unless the travel time of ³H through the unsaturated zone is comparable to that of SF₆. The ratio of integrals of the response function over the age range with tracer and the whole response function yields the ratio of water with tracer to total flow of water. That ratio is a tracer‐dependent function of time. Transport modelling of SF₆ tracer done with MT3D code yielded initially large discrepancies between calculated and measured tracer concentrations. Some discrepancies remained even after calibration of the transport model with SF₆. Simulation of tritium contents with a calibrated transport model yielded reasonable agreement with measured contents in some wells and indicated a need for further investigations, particularly in the eastern part of the aquifer. The existence of distinct hydrochemical zones is consistent with the tracer data; young waters with measurable ³H and SF₆ contents are aerobic and of HCO₃ Ca or HCO₃ SO₄ Ca types. Slightly elevated Na and Cl contents, as well as the highest concentrations of SO₄ and NO₃ within this zone are due to anthropogenic influences. Anaerobic conditions prevail in the far field, under the confining cover, where pre‐bomb era Holocene waters dominate. In that zone, dissolved oxygen, NO₃ and U contents are reduced, and Fe, Mn and NH₄ contents increase. In the third zone, early Holocene and glacial waters occur. They are of HCO₃ Ca Na or HCO₃ Na types, with TDS values higher than 1 g l⁻¹ and Na content higher than 200 mg l⁻¹, due to either small admixtures of ascending or diffusing older water or freshening of marine sediments, a process that is probably occurring till the present time. Copyright © 2005 John Wiley & Sons, Ltd.