TEQC在河北CORS系统站点环境检测中的应用

介绍河北省卫星定位综合服务系统的建设情况,讨论TEQC软件对参考站周边环境的检测方法,给出了质量控制指标。并针对河北省卫星定位综合服务建设过程中存在问题的几个参考站,应用TEQC软件进行数据质量检查,对处理结果进行分析和探讨。     

Sediment texture and grain-size implications: the Changjiang subaqueous delta

Sediment cores were collected from the subaqueous delta of the Changjiang Estuary. Sediment grain-size profiles and their fractal dimensions were analyzed, to elucidate responses to long-term sedimentary processes. In addition, the environmental sensitive populations of grain size have been extracted. The sediment cores can be divided into two parts, according to the sedimentary structures present. The upper part (0-12 cm) is interpreted as being the active layer, which is influenced frequently by changes i...     

Difficulties in separating hurricane induced effects from natural benthic succession: Hurricane Isabel,a case study from Eastern Virginia,USA

Hurricane Isabel reached the Eastern seaboard of North America on 18 September 2003 causing estimated damage >3 billion US dollars and the death of ∼50 people. Isabel is considered to be one of the most significant tropical cyclones to affect Virginia, since the Chesapeake Potomac Hurricane of 1933 and Hurricane Hazel in 1954. A study of the temporal changes in the benthic fauna pre- and post-hurricane was conducted on an intertidal sandflat within the dynamic barrier island system near Wachapreague, Eastern Virginia. Replicate sediment cores were collected 3 weeks before Isabel made landfall and further samples were collected on 5 occasions over the following 20 months. An immediate effect of Isabel was a doubling in the number of species, a significant increase in invertebrate species diversity (H′) and a rise in opportunistic species and deposit feeders, but a non-significant increase in the total number of organisms. Changes in infauna occurred such that by the end of the study there were significantly increased numbers of species, faunal abundances and community diversity measures, as compared with pre-hurricane samples, suggesting a potentially positive medium-term effect of this hurricane perturbation. The most notable direct effects of the hurricane were on the relative abundances of feeding guilds with a reduction in interface feeders from 87% pre-hurricane to 64% post-hurricane, and an increase in surface deposit feeders from 7% pre-hurricane to 20% post-hurricane. The study highlights potential problems in interpreting post-perturbation data when insufficient pre-perturbation data exist.     

Benthic nitrate biogeochemistry affected by tidal modulation of Submarine Groundwater Discharge (SGD) through a sandy beach face, Ria Formosa, Southwestern Iberia

To investigate both the role of tides on the timing and magnitude of Submarine Groundwater Discharge (SGD), and the effect on benthic nitrogen biogeochemistry of nitrate-enriched brackish water percolating upwards at the seepage face, we conducted a study of SGD rates measured simultaneously with seepage meters and mini-piezometers, combined with sets (n = 39) of high resolution in-situ porewater profiles describing NH₄⁺, NO₃⁻, Si(OH)₄ and salinity distribution with depth (0–20 cm). Sampling took place during two consecutive spring tidal cycles in four different months (November 2005, March, April and August 2006) at a backbarrier beach face in the Ria Formosa lagoon, southern Portugal. Our results show that the tide is one of the major agents controlling the timing and magnitude of SGD into the Ria Formosa. Intermittent pumping of brackish, nitrate-bearing water at the beach face through surface sediments changed both the magnitudes and depth distributions of porewater NH₄⁺ and NO₃⁻ concentrations. The most significant changes in nitrate and ammonium concentrations were observed in near-surface sediment horizons coinciding with increased fraction of N in benthic organic matter, as shown by the organic C:N ratio. On the basis of mass balance calculations executed on available benthic profiles, providing ratios of net Ammonium Production Rate (APR) to Nitrate Reduction Rate (NRR), coupled to stoichiometric calculations based on the composition of organic matter, potential pathways of nitrogen transformation were speculated upon. Although the seepage face occasionally contributes to reduce the groundwater-borne DIN loading of the lagoon, mass balance analysis suggests that a relatively high proportion of the SGD-borne nitrogen flowing into the lagoon may be enhanced by nitrification at the shallow (1–3 cm) subsurface and modulated by dissimilatory nitrate reduction to ammonium (DNRA).     

Biodiversity patterns of free-living marine nematodes in a tropical bay: Cienfuegos, Caribbean Sea

Spatial and temporal biodiversity patterns of free-living marine nematodes were studied in Cienfuegos Bay, a tropical semi-enclosed basin in the Caribbean Sea. Taxonomic (to species level) and functional (biological trait) approaches were applied for describing the assemblage structure and relating it to abiotic environment based on a sampling scheme in six subtidal stations and three months. Biological trait approach added relevant information to species pattern regarding relationships between diversity patterns and the abiotic environment. The most common morphotypes were deposit feeding nematodes, with colonising abilities of 2–3 (in a scale from 1 to 5), tail conical cylindrical or filiforme and body slender; and their abundance were correlated with depth, organic matter and silt/clay fraction. In spite of a high turnover of species, functional diversity of assemblages did not change notably in space and time. A result probably due to sampling of the habitat pool of species and to low heterogeneity of the studied muddy bottoms. Chemical pollution (organic enrichment and heavy metals) and hydrodynamic regime possibly drove the biodiversity patterns. Spatial distribution of assemblages support the existence of two well differentiated basins inside the bay, the northern basin more polluted than the southern one. The low hydrodynamic regime would determine a poor dispersion of nematodes resulting in high spatial variance in the assemblage structure; and also the associated hypoxic conditions and pollutants in sediments can explain the dominance of tolerant nematode species such as Daptonema oxycerca, Sabatieria pulchra, Terschellingia gourbaultae, and Terschellingia longicaudata. A comparison of spatial–temporal patterns of biodiversity between Cienfuegos Bay and other semi-enclosed bays in temperate regions suggests several similarities: nematode assemblages are strongly influenced by anthropogenic disturbance, temporal trends are weak or overridden by spatial ones, and few cosmopolitan genera/species tolerant to pollution and hypoxic conditions are dominant.     

Mangrove expansion and rainfall patterns in Moreton Bay, Southeast Queensland, Australia

Changes in rainfall pattern have been suggested as a mechanism for the landward incursion of mangrove into salt marsh. The aim of the research was to assess the relationship between rainfall patterns and the spatial distribution of mangrove forests at study sites in Moreton Bay, Southeast Queensland, Australia, over a 32-year period from 1972 to 2004. To identify periods of relatively consistent rainfall patterns points at which rainfall patterns changed (change-points) were identified using the non-parametric Pettitt–Mann–Whitney-Statistic and the cumulative sum technique. The change-points were then used to define the temporal periods over which changes to mangrove area were assessed. Both mangrove and salt marsh area were measured by digitizing aerial photographs acquired in 1972, 1990 (the year with the most significant change-point), and 2004. The rates of change in mangrove area pre-1990 (a wetter period) and post-1990 (a drier period) were estimated. A significant positive relationship was demonstrated between rainfall variables and landward mangrove expansion, but not for seaward expansion. We concluded that rainfall variability is one of the principal factors influencing the rate of upslope encroachment of mangrove. However, the rate of expansion may vary from site to site due to site-specific geomorphological and hydrological characteristics and the level of disturbance in the catchment.     

九龙江河口区表层沉积物重金属元素分布特征及其沉积环境

通过对九龙江河口表层沉积物的重金属元素含量、沉积物粒度等要素进行分析,结合相关与聚类分析等统计手段,探讨了九龙江河口地区的沉积环境与重金属元素含量特征的关系.结果表明,即使在沉积环境复杂的河口地区,重金属含量分布与沉积物粒度仍存在明显的对应关系.受沉积动力影响,不同的重金属元素分布在九龙江河口地区表现出较大差异,而嵩屿至屿仔尾一带呈带状南北向展布的重金属相对高值条带值得引起注意.     

地理信息公共服务平台的总体技术设计研究

国家地理信息公共服务平台建设与运行维护是一项超大型地理信息工程。为了切实做好统筹规划、统一设计、规范建设、分步实施,国家测绘局组织开展了总体技术设计研究,制订了技术设计指南。本文介绍了国家地理信息公共服务平台总体设计的基本思路和总体架构。     

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