黄河泛滥平原全新世沙尘暴活动的历史记录——以颖河上游一典型剖面为例

研究了淮河支流颖河上游嵩山东麓一典型全新世黄土-古土壤剖面,获得了较高时间分辨率的磁化率、粒度成分和>0.063mm粒级百分比含量等环境代用指标系列。通过地层对比研究,确定了该剖面的基本年代框架。分析了颖河上游全新世黄土-土壤磁化率、粒度特征,论证了颖河上游全新世黄土-土壤物质粒度成分与黄河泛滥沉积沙尘暴活动关系,揭示了颖河上游全新世黄河泛滥平原沙尘暴活动特征。3100aBP以来气候趋于干旱,黄河下游泛滥频率增加,风沙活动范围显著扩大,沙尘暴活动强烈。     

Assessing the Link Between Coastal Urbanization and the Quality of Nekton Habitat in Mangrove Tidal Tributaries

To assess the potential influence of coastal development on habitat quality for estuarine nekton, we characterized body condition and reproduction for common nekton from tidal tributaries classified as undeveloped, industrial, urban or man-made (i.e., mosquito-control ditches). We then evaluated these metrics of nekton performance, along with several abundance-based metrics and community structure from a companion paper (Krebs et al. 2013) to determine which metrics best reflected variation in land-use and in-stream habitat among tributaries. Body condition was not significantly different among undeveloped, industrial, and man-made tidal tributaries for six of nine taxa; however, three of those taxa were in significantly better condition in urban compared to undeveloped tributaries. Palaemonetes shrimp were the only taxon in significantly poorer condition in urban tributaries. For Poecilia latipinna, there was no difference in body condition (length–weight) between undeveloped and urban tributaries, but energetic condition was significantly better in urban tributaries. Reproductive output was reduced for both P. latipinna (i.e., fecundity) and grass shrimp (i.e., very low densities, few ovigerous females) in urban tributaries; however a tradeoff between fecundity and offspring size confounded meaningful interpretation of reproduction among land-use classes for P. latipinna. Reproductive allotment by P. latipinna did not differ significantly among land-use classes. Canonical correspondence analysis differentiated urban and non-urban tributaries based on greater impervious surface, less natural mangrove shoreline, higher frequency of hypoxia and lower, more variable salinities in urban tributaries. These characteristics explained 36 % of the variation in nekton performance, including high densities of poeciliid fishes, greater energetic condition of sailfin mollies, and low densities of several common nekton and economically important taxa from urban tributaries. While variation among tributaries in our study can be largely explained by impervious surface beyond the shorelines of the tributary, variation in nekton metrics among non-urban tributaries was better explained by habitat factors within the tributary and along the shorelines. Our results support the paradigm that urban development in coastal areas has the potential to alter habitat quality in small tidal tributaries as reflected by variation in nekton performance among tributaries from representative land-use classes.     

Response of Tidal Creek Fish Communities to Dredging and Coastal Development Pressures in a Shallow-Water Estuary

To investigate the effects of dredging and associated development pressures (i.e., shoreline armoring, developed land use) on fish, three sets of paired dredged and undredged tidal creeks were surveyed within Lynnhaven River, Virginia. Fish species diversity, community abundance, biomass, and size structure were compared among creeks and related to watershed, shoreline, and physicochemical characteristics. Mean fish community characteristics (e.g., abundance) were similar among creeks; however, species-specific analysis revealed subtle differences. Species biomass differed between dredged and undredged creeks, though species abundance was similar. Turbidity highly influenced differences in species abundance among creeks, while organic matter, dissolved oxygen, turbidity, and shoreline hardening may be influencing biomass patterns. The most recently dredged creek appeared to provide less suitable nursery habitat for some species than historically dredged creeks, suggesting initial adverse effects with eventual recovery. Protective measures, such as preservation of marshes, dredge depth, and time-of-year restrictions, may be moderating development and dredging pressures.     

Near-Surface Larval and Juvenile Fish in Coastal Habitats: Comparisons Between the Inner Shelf and an Estuary in the New York Bight During Summer and Fall

Exchanges of fish larvae between the inner continental shelf and estuaries can be critical to the functional significance of these habitats as nurseries. We sampled near-surface fishes on the inner continental shelf off New Jersey and in an adjacent estuary during the summer and fall of 2005 and 2006 to evaluate the occurrence and variation in these connections. Very few of the abundant taxa (Anchoa mitchilli, Brevoortia tyrannus, Urophycis regia, Etropus microstomus, Peprilus triacanthus, and Pomatomus saltatrix) were exclusive to either habitat but some did change in relative habitat affinity among seasons. For some species, this was indicative of a departure from the ocean for estuaries (e.g., Micropogonias undulatus) while others used both habitats during the summer and fall (e.g., Syngnathus fuscus, Scophthalmus aquosus, and A. mitchilli). Together, these observations confirm the high degree of connectivity between the near-surface larval fishes from the inner continental shelf and estuaries.     

Responses of Native and Invasive Floating Aquatic Plant Communities to Salinity and Desiccation Stress in the Southeastern US Coastal Floodplain Forests

Low-lying coastal ecosystems along the northern Gulf of Mexico are already experiencing the effects of elevated salinity from sea-level rise and are predicted to face extreme events such as extended saltwater inundation, intense Atlantic hurricanes, and episodic drought. The ability of coastal plant communities to survive stresses from these events depends largely on how these communities respond to the stresses. Our understanding of how plant communities dominated by native vs. invasive plants respond to extreme events is limited. Utilizing controlled greenhouse experiments, we assessed the responses of floating aquatic macrophyte communities, dominated by native or invasive plants, of the coastal floodplains, Louisiana, USA, to a gradient of chronic salinity, mimicking sea-level rise; a gradient of acute salinity, mimicking hurricane storm surges; and a gradient of desiccation stress, mimicking episodic drought. We found that salinity and desiccation stress effects on plant communities depended on the degree of plant invasion; plant community cover decreased precipitously as severity of stress increased. Specifically, extreme salinity led to a decrease in plant cover of >?90% when communities were dominated by invasive plants, whereas increased desiccation stress led to decreased plant cover of 100% when communities were dominated by native species. At low to moderate salinity, invasive dominated plant communities performed better than native dominated. These responses to salinity and desiccation stress may drive large-scale shifts in plant community structure, including loss of species. Our results underscore the importance of evaluating plant community responses to environmental extremes to determine the potential for future effects on dynamics and functioning of low-lying coastal floodplain ecosystems experiencing effects of climate change.     

A Model Framework to Determine the Production Potential of Fish Derived from Coastal Habitats for Use in Habitat Restoration

Metrics of fish production are often used to guide habitat restoration in coastal ecosystems. In this study, we present a general model framework to estimate the absolute production potential of fish (i.e., fish and large decapods) derived from coastal habitats. Production potential represents lifetime production, whether or not the fish uses the habitat of interest for their entire lifespan. The framework uses an age-structured Leslie population matrix with length-dependent survival and fecundity, coupled with growth and length-weight functions. Uncertainty quantification was also included and accounted for parameter dependencies using copulas. Given the limited abundance data available, we made the simplifying assumptions of steady-state populations and a direct scaling of the resultant proportional stable age distribution with observed fish density (in at least one age class). Literature values for regional estimates of mortality and growth were used. We applied our model using data of fish density from seagrass (Zostera marina, eelgrass) beds and bare soft-sediment bottom on the Atlantic coast of Nova Scotia, Canada. A total of 22 species of fish was collected. Species-specific estimates of fish production potential from seagrass ranged from 8.6 × 10^?3 to 50.0 g WW m^?2 year^?1, with uncertainty estimates being within the same order of magnitude as the median. Production potential of most fishes was enhanced by seagrass relative to adjacent bare sediment. The model framework can be adapted and extended to include increasing complexity (e.g., time dependencies) as more extensive data are acquired, and thus has application beyond that presented here.     

Wetland Plant Community Responses to the Interactive Effects of Simulated Nutrient and Sediment Loading: Implications for Coastal Restoration Using Mississippi River Diversions

The Mississippi River Delta Complex (MRDC) has experienced extensive wetland loss in the last century due, in part, to flood control levees that have isolated the lower Mississippi River and its sediment resource from adjacent wetlands. Reconnecting the River to these wetlands through diversions is being used and proposed on a larger scale for the future, to reduce wetland loss rates. However, some currently operating diversions (e.g., Caernarvon and Davis Pond) have been implicated in causing negative impacts on wetland ecosystem structure and function due to increased nutrient loads in diverted Mississippi River water combined with insufficient sediment delivery. Initial assessments of these concerns were carried out in a greenhouse setting where six nutrient enrichment treatment levels (control, NO₃, NH₄, PO₄, SO₄, and Combo [NO₃?+?NH₄?+?PO₄?+?SO₄]) were applied with and without sediment addition to 60 marsh sods from a Sagittaria lancifolia-dominated oligohaline wetland at rates simulating the Davis Pond Diversion of the Mississippi River. After 25 months, independent enrichment with N (regardless of form) and sediment was generally beneficial to wetland structure and function, while SO₄ enrichment had the opposite effect, regardless of sediment addition. Simultaneous application of N and P (i.e., the Combo treatment level) ameliorated the negative impacts of SO₄-loading, but the concurrent application of sediment did not, likely because the loading rate was based on a diversion that was designed to deliver water and not to maximize sediment input. Nonetheless, sediment input is critical to the sustainability of MRDC wetlands experiencing high rates of deterioration. Thus, optimizing future diversions to maximize sediment delivery, along with continued surveillance of negative nutrient effects, are recommended management decisions.     

Phytoplankton Biomass and Production in Subtropical Hong Kong Waters: Influence of the Pearl River Outflow

The size-fractionated phytoplankton biomass and primary production were investigated in four contrasting areas of Hong Kong waters in 2006. Phytoplankton biomass and production varied seasonally in response to the influence of the Pearl River discharge. In the dry season, the phytoplankton biomass and production were low (<42 mg chl m⁻² and <1.8 g C m⁻² day⁻¹) in all four areas, due to low temperatures and dilution and reduced light availability due to strong vertical mixing. In contrast, in the wet season, in the river-impacted western areas, the phytoplankton biomass and production increased greater than five-fold compared to the dry season, especially in summer. In summer, algal biomass was 15-fold higher than in winter, and the mean integrated primary productivity (IPP) was 9 g C m⁻² day⁻¹ in southern waters due to strong stratification, high temperatures, light availability, and nutrient input from the Pearl River estuary. However, in the highly flushed western waters, chl a and IPP were lower (<30 mg m⁻² and 4 g C m⁻² day⁻¹, respectively) due to dilution. The maximal algal biomass and primary production occurred in southern waters with strong stratification and less flushing. Spring blooms (>10 μg chl a L⁻¹) rarely occurred despite the high chl-specific photosynthetic rate (mostly >10 μg C μg chl a ⁻¹ day⁻¹) as the accumulation of algal biomass was restricted by active physical processes (e.g., strong vertical mixing and freshwater dilution). Phytoplankton biomass and production were mostly dominated by the >5-μm size fraction all year except in eastern waters during spring and mostly composed of fast-growing chain-forming diatoms. In the stratified southern waters in summer, the largest algal blooms occurred in part due to high nutrient inputs from the Pearl River estuary.     

红河盆地的化学风化作用:主要和微量元素地球化学记录

河流沉积物的元素含量有助于反映其流域的自然风化过程。红河是世界上重要的河流之一,但其沉积物的地球化学研究却几乎没有。本文通过开展红河盆地干流和主要支流40个样品的主要和微量元素地球化学分析,发现红河流域硅酸盐岩的化学风化作用为中等强度,与长江及亚马逊河的风化强度相近,而高于黄河,低于珠江;且化学风化作用受该区域的气候和构造作用控制。     

Contribution of Viral Lysis and Nanoflagellate Grazing to Bacterial Mortality at Surface Waters and Deeper Depths in the Coastal Ecosystem of Subtropical Western Pacific

Since nanoflagellate grazing and viral lysis differ in their impact on the microbial food web, it is important to assess their relative importance on bacterial mortality fractions. This study investigated the abundance of microbial assemblages and the loss of bacteria due to viral lysis and nanoflagellate grazing at two different depths (3 and 135 m) in the coastal waters of subtropical western Pacific during summer (July, August, and September 2012). The bacterial growth rates in the surface waters varied from 0.07 to 0.09 h^?1, a range higher than those found in the deep waters (0.013 to 0.016 h^?1). The grazing rates of nanoflagellates on bacteria ranged from 0.051 to 0.058 h^?1 and from 0 to 0.004 h^?1 in the surface and deep waters, respectively. During the study period, nanoflagellate grazing was responsible for most of bacterial mortality (81–87 %) relative to viral lysis in the surface waters, while viral lysis was responsible for 67–75 % of the total bacterial mortality in the deep waters.     

Using hyperspectral reflectance to detect different soil erosion status in the Subtropical Hilly Region of Southern China: a case study of Changting, Fujian Province

Hyperspectral reflectance is widely used for determining important properties of soil erosion. However, there have been few studies which focus on the influence of soil erosion intensity on the characteristics of hyperspectral reflectance, and such information would provide a new tool to improve quantitative understanding of soil erosion. In this study, 35 soil samples were collected from three regions with different erosion intensities in Changting County, a typical severely eroded county in the ferralic cambisol region of southern China, and classified into three groups according to different erosion controlling status. All the samples were scanned at wavelengths from 400 to 2,498 nm by an ASD Field Spec Portable Spectrometer, and the erosion intensity of each sample was calculated using the Revised Universal Soil Loss Equation. Multivariate stepwise linear regression was then employed to model the soil erosion intensity based on reflectance. The results suggested that the absorption peaks of each sample were in a similar wavelength range, while the absorption depth varied with different erosion status, and the reflectance of extremely eroded soil samples were the highest. During modelling of erosion intensity, the result was poor when all the samples were combined, but improved greatly at certain wavelength ranges when samples were classified into three groups based on different erosion controlling status. The extreme erosion group markedly outperformed the other two groups, in which the R ² values between the actual and predicted erosion intensity were 0.67, 0.85 and 0.80 for each spectral type. The results indicated that hyperspectral reflectance is a promising method for accurately monitoring erosion intensity.     

近海营养盐和微量元素的大气沉降

受气候变化和人类活动的影响,传输和沉降到全球近海的大气污染物急剧增加.1997年后对近海营养盐和微量元素大气沉降的众多研究表明,通过大气沉降至近海的氮和磷分别为13～73 mmol N/(m2·a)和0.11～1.6 mmol P/(m2·a),微量元素的沉降通量具有显著的时空变化特征,在不同海区最高可相差3个数量级.对于很多近海包括东海(East China Sea)和黄海(Yellow Sea),大气沉降的营养盐和部分微量元素可能超出了其河流输入量.大气沉降除了对近海富营养化有重要贡献之外,其事件性特征可使初级生产力在短期内大幅度增加,从而影响赤潮发生.微量元素沉降还可能抑制某些藻类生长,对初级生产力和生态系统结构产生更为复杂的影响.未来研究重点是准确估算近海各物质的大气沉降通量,了解其对浮游植物生长的影响机制.     

Coupling Between the Coastal Ocean and Yaquina Bay,Oregon: Importance of Oceanic Inputs Relative to Other Nitrogen Sources

Understanding of the role of oceanic input in nutrient loadings is important for understanding nutrient and phytoplankton dynamics in estuaries adjacent to coastal upwelling regions as well as determining the natural background conditions. We examined the nitrogen sources to Yaquina Estuary (Oregon, USA) as well as the relationships between physical forcing and gross oceanic input of nutrients and phytoplankton. The ocean is the dominant source of dissolved inorganic nitrogen (DIN) and phosphate to the lower portion of Yaquina Bay during the dry season (May through October). During this time interval, high levels of dissolved inorganic nitrogen (primarily in the form of nitrate) and phosphate entering the estuary lag upwelling favorable winds by 2 days. The nitrate and phosphate levels entering the bay associated with coastal upwelling are correlated with the wind stress integrated over times scales of 4–6 days. In addition, there is a significant import of chlorophyll a to the bay from the coastal ocean region, particularly during July and August. Variations in flood-tide chlorophyll a lag upwelling favorable winds by 6 days, suggesting that it takes this amount of time for phytoplankton to utilize the recently upwelled nitrogen and be transported across the shelf into the estuary. Variations in water properties determined by ocean conditions propagate approximately 11–13 km into the estuary. Comparison of nitrogen sources to Yaquina Bay shows that the ocean is the dominant source during the dry season (May to October) and the river is the dominant source during the wet season with watershed nitrogen inputs primarily associated with nitrogen fixation on forest lands.     

中国天山乌鲁木齐河源冰芯pH和电导记录的现代环境过程研究

Analyses of pH and conductivity in precipitation sampled during June 1995 to June 1996, in snow pits sampled during the winter of 1995-1996 and during the summer of 1996, and in shallow ice core retrieved in May 1996 from the headwaters of the rmqi River are presented in this paper. Though a certain degree of shift appears for pH and conductivity in the post-deposition and firnification processes, a relationship between pH and conductivity is still preserved in the ice core records, which validates the application of the ice core pH and conductivity records from the areas with strong melting for paleoclimate reconstruction.     

高寒山区河水与地下水相互作用的温度示踪:以黑河上游葫芦沟流域为例

高寒山区的地表水与地下水相互作用的定量研究对水资源的评价及管理等具有重要意义,而目前在高寒山区开展的地表水与地下水相互作用的定量研究相对较少.以黑河上游葫芦沟流域为研究区域,采用温度示踪方法对高寒山区河水与地下水的相互作用进行了研究,并对温度示踪方法在高寒山区的适用性进行了讨论.监测了研究区两个时段的地温、河水水位、地下水水位以及河床沉积物底部不同深度处的温度,并对温度系列数据进行定量分析,计算了不同位置处河水入渗流速.结果表明:研究区河水水位普遍高于地下水水位;河床底部温度在9月份整体低于7月;流速计算结果表明监测时段内主要为河水入渗补给地下水,入渗速率整体介于2×10-6~5×10-5 m/s.温度示踪法在高寒山区的适用性分析表明:在地下水受多途径补给时,温度示踪法仅指示河水对地下水的补给,而其他水源对地下水的补给还要通过同位素方法和数值模拟等其他手段进行计算.影响高寒山区河水对地下水补给的因素主要有:河水与地下水水位、河床沉积物的水力传导系数与热容.      

某傍河污染场地排污河与地下水水力联系模拟研究

为研究常见地表排污河对地下水造成的影响,选择安徽省淮北市濉河某傍河区域进行研究。在对研究场地开展野外调查、抽水试验、微水试验等工作的基础上,从水动力学角度对研究场地地下水进行系统研究。应用Processing Modflow建立了该研究场地的水文地质模型,根据各均衡区间水量交换情况揭示了排污河、深浅含水层间的水力联系状况。模拟结果表明,排污河与浅层含水层之间没有明显的水力联系;深、浅含水层之间的水力联系微弱。     

A Numerical Comparison of the Behavior of a Braced Excavation Using Two and Three-Dimensional Creep Plastic Analyses

Current study deals with investigating the effects of both time factor and the selection of a constitutive model type on predicting deformations of an excavation braced by nailing using two and three-dimensional finite element analyses. In addition, the effects of stress path and the type of defined initial conditions of the analytical model on deformations of the floor and walls of the excavation are also studied. Time factor, in the form of earth materials’ creep, can largely be entered into calculation of deformations of excavations by conducting viscoelastic and viscoplastic analyses. On the other hand, there hasn’t been done a comprehensive study regarding the creep behavior of excavations through comparing the results of two-dimensional and three-dimensional numerical analyses so far. The results showed that it’s largely possible to approach the actual deformation behavior of an excavation by considering the constitutive model of soft soil creep, SSC model, in the numerical plastic analyses. The effects of stress path on the deformation behavior of the excavation walls and excavation floor are investigated by using OCR stress ratio and POP stress difference; These two factors, both of which are also analogous, represent a boundary value for swelling behavior of the excavation floor and an increasing rate for the deformation behavior of the excavation walls since the increase in OCR or POP is equal to the increase in the soil lateral pressure coefficient at rest.     

介绍与简评《地层中地震记录(古地震)》一书

地质历史中有无地震？回答是肯定的。现代板块构造机制解决了地震的构造成因,同样地史中的板块运动也必然诱发地震。遗憾的是有关地史中地震（古地震）的报道实在是太少了,究其原因：①不认识地史中的地震记录;②缺乏有效的研究手段和方法;③忽视这一研究领域,或者将地震记录作其他成因解释。因此古地震研究就成了地质调查中的薄弱环节。     

Hypoxia in a Coastal Embayment of the Chesapeake Bay: A Model Diagnostic Study of Oxygen Dynamics

Two distinct hypoxic patterns were revealed from high-frequency dissolved oxygen (DO) data collected from North Branch of Onancock Creek, a shallow coastal estuary of the Chesapeake Bay, from July to October 2004. Diurnal hypoxia developed associated with large DO swings during fair weather and hypoxia/anoxia developed for prolonged 2–5-day periods following rainfall events. A simplified diagnostic DO-algae model was used to investigate DO dynamics in the creek. The model results show that the modeling approach enables important features of the DO dynamics in the creek to be captured and analyzed. Large anthropogenic inputs of nutrients to the creek stimulated macroalgae blooms in the embayment. High DO production resulted in supersaturated DO in daytime, whereas DO was depleted at night as the high respiration overwhelmed the DO supply, leading to hypoxia. Unlike deep-water environments, in this shallow-water system, biological processes dominate DO variations. High macroalgae biomass interacting with low light and high temperature trigger the development of prolonged hypoxic/anoxic postrainfall events.