Quantifying the temporal dynamics of wood in large rivers: field trials of wood surveying,dating, tracking,and monitoring techniques

Wood plays an important role in stream ecology and geomorphology. Previous studies of wood in rivers have quantified spatial distributions but temporal dynamics remain poorly documented. The lack of such data is related to limitations of existing methods, especially when applied to large rivers. Five techniques are field‐tested to assess their utility for quantifying the temporal dynamics in rivers: repeated high‐resolution aerial surveys, the measurement of wood physical characteristics as proxies for ¹⁴C dating, passive and active radio frequency identification (RFID) tags, radio transmitters, and video. The spatial distribution of wood is surveyed using aerial imagery with a resolution finer than 0·10 m. The estimation of temporal trends by repeated aerial‐based surveys needs to consider vegetation growth and hiding. Wood residence times can be calculated using ¹⁴C analysis, but the assessment of wood physical characteristics including decay status and wood density offers a cheaper, if less accurate, alternative. Wood resistance to penetration is tested but results are not significant. Radio transmitters are reliable for multi‐year (～5 year) surveys and can be detected at 800 m. Passive RFID tags are limited by a read range of 0·30 m but are reliable for longer term (>5 year) studies. Active RFID tags combine a moderate read range (10–300 m) and low cost with in‐flood detection but require more testing. Video monitoring of wood passing on the surface of a river is successfully implemented. For a single flood on the Ain River (France), wood transport rates are an order of magnitude higher on the rising limb of the hydrograph than on the falling limb. Overall, the techniques improve the ability to gather the data needed to understand wood transfer processes and calibrate budgets of wood in rivers. Copyright © 2009 John Wiley & Sons, Ltd.     

Chemical and isotopic compositions of thermal springs,fumaroles and bubbling gases at Tacaná Volcano (Mexico–Guatemala): implications for volcanic surveillance

This study presents baseline data for future geochemical monitoring of the active Tacaná volcano–hydrothermal system (Mexico–Guatemala). Seven groups of thermal springs, related to a NW/SE-oriented fault scarp cutting the summit area (4,100m a.s.l.), discharge at the northwest foot of the volcano (1,500–2,000m a.s.l.); another one on the southern ends of Tacaná (La Calera). The near-neutral (pH from 5.8 to 6.9) thermal (T from 25.7°C to 63.0°C) HCO₃–SO₄ waters are thought to have formed by the absorption of a H₂S/SO₂–CO₂-enriched steam into a Cl-rich geothermal aquifer, afterwards mixed by Na/HCO₃-enriched meteoric waters originating from the higher elevations of the volcano as stated by the isotopic composition (δD and δ¹⁸O) of meteoric and spring waters. Boiling temperature fumaroles (89°C at ~3,600m a.s.l. NW of the summit), formed after the May 1986 phreatic explosion, emit isotopically light vapour (δD and δ¹⁸O as low as −128 and −19.9‰, respectively) resulting from steam separation from the summit aquifer. Fumarolic as well as bubbling gases at five springs are CO₂-dominated. The δ¹³C_CO2 for all gases show typical magmatic values of −3.6 ± 1.3‰ vs V-PDB. The large range in ³He/⁴He ratios for bubbling, dissolved and fumarolic gases [from 1.3 to 6.9 atmospheric ³He/⁴He ratio (R _A)] is ascribed to a different degree of near-surface boiling processes inside a heterogeneous aquifer at the contact between the volcanic edifice and the crystalline basement (⁴He source). Tacaná volcano offers a unique opportunity to give insight into shallow hydrothermal and deep magmatic processes affecting the CO₂/³He ratio of gases: bubbling springs with lower gas/water ratios show higher ³He/⁴He ratios and consequently lower CO₂/³He ratios (e.g. Zarco spring). Typical Central American CO₂/³He and ³He/⁴He ratios are found for the fumarolic Agua Caliente and Zarco gases (3.1 ± 1.6 × 10¹⁰ and 6.0 ± 0.9 R _A, respectively). The L/S (5.9 ± 0.5) and (L + S)/M ratios (9.2 ± 0.7) for the same gases are almost identical to the ones calculated for gases in El Salvador, suggesting an enhanced slab contribution as far as the northern extreme of the Central American Volcanic Arc, Tacaná.     

Variability of shallow overland flow velocity and soil aggregate transport observed with digital videography

Field experiments at Tiramoana station 30 km north of Christchurch, New Zealand using an erosion plot 16·5 m long, 0·6 m wide, and with a slope of 14–14·5° on rendzina soil aimed to measure the variability of flow velocity and of soil aggregates transport rate in shallow overland flow. Discharge/cross‐section area ratio was used to estimate mean velocity, and high‐speed digital video camera and image analysis provided information about flow and sediment transport variability. Six flow runs with 0·5–3·0 L s^?1 discharges were supercritical with Froude numbers close to or more than 1. Mean flow velocity followed Poiseuille law, float numbers were more than 1·5 and hydraulic resistance was an inverse proportional function of the Reynolds number, which is typical for laminar flows. Hence actual velocity varied through time significantly and the power spectrum was of ‘red‐noise’, which is typical for turbulent flow. Sediment transport rates had even higher variability, and soil aggregates transport was a compound Poisson process. Copyright © 2008 John Wiley & Sons, Ltd.     

Visualization of spatial patterns and temporal trends for aerial surveillance of illegal oil discharges in western Canadian marine waters

This paper examines the use of exploratory spatial analysis for identifying hotspots of shipping-based oil pollution in the Pacific Region of Canada’s Exclusive Economic Zone. It makes use of data collected from fiscal years 1997/1998 to 2005/2006 by the National Aerial Surveillance Program, the primary tool for monitoring and enforcing the provisions imposed by MARPOL 73/78. First, we present oil spill data as points in a “dot map” relative to coastlines, harbors and the aerial surveillance distribution. Then, we explore the intensity of oil spill events using the Quadrat Count method, and the Kernel Density Estimation methods with both fixed and adaptive bandwidths. We found that oil spill hotspots where more clearly defined using Kernel Density Estimation with an adaptive bandwidth, probably because of the “clustered” distribution of oil spill occurrences. Finally, we discuss the importance of standardizing oil spill data by controlling for surveillance effort to provide a better understanding of the distribution of illegal oil spills, and how these results can ultimately benefit a monitoring program.     

TDE系列地震数据采集器

ＴＤＥ系列地震数据采集器是一套１６位（ＴＤＥ－２１６Ｃ）／２４位（ＴＤＥ－２２４Ｃ）地震数据采集器。该采集器为低功耗、程控增益、现场模数转换,其带宽为（０～２０Ｈｚ）,动态范围为９０ｄＢ（ＴＤＥ－２１６Ｃ）／１２０ｄＢ（ＴＤＥ－２２４Ｃ）。采集器通过接收ＧＰＳ信号产生精确定时。介绍了该采集器的技术设计方案、性能及实际应用效果。     

暴雨及其衍生灾害的三维影视模拟技术初探

由于暴雨常具有和危险性,难以及时拍摄到暴雨灾害的现场画面,本文基于大气降水粒子的物理特征,采用Maya、Reanlflow、AfterEffects、Premier等软件运用刚体碰撞、流体、粒子等动画技术,对暴雨及其引发的城市积涝、山体滑坡和泥石流灾害的发生和演变过程进行影视模拟,初步建立了相关技术流程及技术指标,可用于指导气象灾害类科普影视节目的制作,宣传防灾减灾知识。     

莒县国土资源局信访工作探析

莒县国土资源局干部职工通过走进基层、走进群众中间,摸排国土资源信访矛盾,查找信访苗头线索,及时制定应对方案,筑牢接访三道防线,努力将矛盾化解在萌芽状态,信访工作取得明显成效。     

The spatial structure of local surficial sediment characteristics on Georges Bank,USA

Georges Bank is one of the world’s most productive marine ecosystems, but the lack of accurate broad-scale sediment maps presently limits habitat assessments and spatial fisheries management. From 1999 to 2009 we surveyed 36,669 km² of Georges Bank using 2.8 and 0.6 m² quadrats viewed with live underwater video (video quadrats). The sediment types observed in 61,604 quadrats were used to map and evaluate spatial structure of local surficial sediment coarseness, dominance, heterogeneity, and maximum size characteristics at a 1 km² spatial resolution. Sand dominated sediment covered 62% of the study area, and there was a logarithmic decline in coverage by larger, coarser and more heterogeneous sediments. Gravel dominated sediments covered 38% of the study area and were more than twice as abundant as previously estimated. A 12,890 km² swath of gravel dominated seabed stretched from Cape Cod to northeastern Georges Bank consistent with estimates of prehistoric glacial extent. Within the swath there were 14 large gravel outcrops (15–2743 km²) . This work increases the spatial resolution of sediment information available for habitat assessments and spatial fisheries management on Georges Bank by two orders of magnitude. The four sediment characteristics we evaluated support further detailed investigations of the Bank’s benthos, including the influences of surficial sediment characteristics on species and community distributions, and more spatially accurate estimates of seabed roughness. Finally, this work demonstrates the use of video quadrats as an alternative to traditional grab sampling and modern acoustic sampling for continental shelf-scale mapping.     

全国地震应急视频会议系统建设及应用

地震应急体系随着国家"十五"重大项目"中国数字地震观测网络"项目的验收初步确立,应急指挥系统建设逐步完善,视频会议系统在地震应急响应中发挥了日益重要的作用。本文简要介绍了视频会议系统的基本组成和关键技术,详细阐述了全国地震应急视频会议系统的网络拓扑结构、主要功能以及在地震应急中的实际应用情况。本文对将来地震应急视频会议应用模式的流程化、规范化有一定实际意义。