Influence of rural land use on streamwater nutrients and their ecological significance   总被引：1，自引：0，他引：1  

Helen P. Jarvie  Paul J.A. Withers  Robin Hodgkinson  Adam Bates  Margaret Neal  Heather D. Wickham  Sarah A. Harman  Linda Armstrong 《Journal of Hydrology》2008,350(3-4):166-186

Concentrations and loads of N and P fractions were examined for lowland rivers, the Wye and Avon, draining a range of representative agricultural land-use types in two major UK river basins. Data collected over a 2-year period demonstrated important diffuse agricultural source contributions to N and P loads in these rivers. Ground water provided a major source of total dissolved nitrogen (TDN) loads, whereas near-surface sources provided a major contribution to total phosphorus (TP) loads. In terms of aquatic ecology, concentrations of nutrients, at times of eutrophication risk (spring and summer low flows) were of key environmental and management significance. Agricultural diffuse sources provided the major source of long-term P loads across the two basins. However, the results demonstrated the dominance of point-source contributions to TP and SRP concentrations at times of ecological risk. Point sources typically ‘tip the balance’ of dissolved inorganic P (soluble reactive P, SRP) above the 100 μg l⁻¹ guideline value indicative of eutrophication risk. The significance of point sources for TP and SRP concentrations was shown by (a) the strong correlations between TP, SRP and B concentrations, using B as a tracer of sewage effluent, (b) the dominant contribution of SRP to TP concentrations and (c) the predominant pattern of dilution of SRP and B with flow. The clean Chalk streams draining low intensity grassland in areas of the Avon with sparse human settlement were oligotrophic and P limited with low SRP concentrations under spring and summer baseflows attributable to groundwater sources. The data provide important insights into the ecological functioning of different lowland stream systems. There was evidence of greater SRP losses and N-limitation in a stream which drains a pond system, demonstrating the importance of longer water residence times for biological nutrient uptake.  相似文献   

Interrupting a multi-species bioinvasion vector: the efficacy of in-water cleaning for removing biofouling on obsolete vessels     

Davidson IC  McCann LD  Sytsma MD  Ruiz GM 《Marine pollution bulletin》2008,56(9):1538-1544

Vector management is the primary method for reducing and preventing nonindigenous species (NIS) invasions and their ecological and economic consequences. This study was the first to examine the efficacy of in-water scrubbing using a submersible cleaning and maintenance platform (SCAMP) to prevent invertebrate species transfers from a heavily fouled obsolete vessel. Initially, prior to treatment, 37 species were recorded in a biofouling matrix that reached 30cm depth in some locations. The bryozoan Conopeum chesapeakensis, and bivalves Mytilopsis leucophaeata and Ischadium recurvum, were dominant sessile species that created structure, supporting mobile biota that included crabs and the associated parasitic barnacle Loxothylacus panopae. Scrubbing had the effect of significantly reducing organism extent and the number of species per sample, but a substantial and diverse (30 species) residual fouling community remained across the entire vessel. Further assessments of management options are needed to prevent potentially damaging NIS transfers. Additional measures taken within an integrated vector management (IVM) strategy may further improve invasion prevention measures.  相似文献   

Diet of winter flounder in a New Jersey estuary: Ontogenetic change and spatial variation     

Linda L. Stehlik  Carol J. Meise 《Estuaries and Coasts》2000,23(3):381-391

Juvenile and adult winter flounder,Pseudopleuronectes americanus Walbaum (Pleuronectidae), from the Navesink River and Sandy Hook Bay, New Jersey, U.S., were examined for ontogenetic, seasonal, and spatial variation in dietary content. Fish (n=1291 non-empty) were placed by cluster analysis of dietary content into three size groups: 15–49, 50–299, and ≥300 mm total length. Clear ontogenetic patterns were revealed, in particular the disappearance of calanoid copepods from the diet as fish grew >50 mm and an increase in number of taxa in the diet with growth. Fish in size group 1 fed upon spionid polychaetes, the calanoid copepodEurytemora affinis, and ampeliscid amphipods. Fish in size group 2 added various species of polychaetes, amphipods, and siphons of the bivalveMya aremaria to their diets. Size group 2 was present during all months of the survey, but only minor seasonal differences in their diet were apparent. One obvious change was the increase in consumption of the shrimpCrangon septemspinosa in summer and fall. Size group 3 fish, collected mainly in fall, ate large volumes ofM. arenaria and glycerid polychaetes. Cluster analysis showed a largescale spatial pattern in diet among fish of size group 1, related to the presence ofE. affinis in winter flounder diets in the river and a marsh cove in the bay. Small-scale spatial differences in diets of fish in size group 2 were possibly related to prey distribution.  相似文献   

Structural damage in the cities of Reggiolo and Carpi after the earthquake on May 2012 in Emilia Romagna   总被引：2，自引：2，他引：0  

Marco Andreini  Anna De Falco  Linda Giresini  Mauro Sassu 《Bulletin of Earthquake Engineering》2014,12(5):2445-2480

This paper addresses the structural damage to the main buildings of the cities of Reggiolo and Carpi after the primary earthquake shocks on May 20th and 29th, 2012, in Emilia Romagna. The damage survey, performed via form-based methods, highlights the different seismic behaviour of several types of buildings, especially those having historical features, and the consequences of the damage in terms of costs. Moreover, an analysis of some failure mechanisms activated in Reggiolo enables the evaluation of the local peak ground acceleration, due to the soil amplification.  相似文献   

Exploring the significance of Polish shops within the Irish foodscape     

Coakley L 《Irish geography : bulletin of the Geographical Society of Ireland》2010,43(2):105-117

Since 2004, Polish food has become firmly embedded in the Irish foodscape as Polish shops opened up in cities and towns across Ireland. The aim of this article is to develop an understanding of the significance and meaning of these Polish shops within the Irish foodscape. In order to achieve this I will take a more-than-representational approach focusing on the practices, sensory reactions and material interactions Poles have within these stores and with their food products. The article will draw on ethnographic observations and semi-structured interviews with Polish migrants to explore their experiences. Attention to these details reveals how Polish shops become meaningful within the Irish foodscape for providing a sense of home to Polish migrants living in Ireland.  相似文献   

Modelling diatom responses to climate induced fluctuations in the moisture balance in continental Antarctic lakes   总被引：3，自引：0，他引：3  

Elie Verleyen  Dominic A. Hodgson  Wim Vyverman  Donna Roberts  Andrew McMinn  Koenraad Vanhoutte  Koen Sabbe 《Journal of Paleolimnology》2003,30(2):195-215

The water chemistry of lake systems on the edge of the Antarctic continent responds quickly to changes in the moisture balance. This is expressed as increasing salinity and decreasing lake water level during dry periods, and the opposite during wet periods. The diatom composition of the lakes also changes with these fluctuations in salinity and lake water depth. This is important, as their siliceous remains become incorporated into lake sediments and can provide long-term records of past salinity using transfer functions. In order to develop transfer functions, diatoms and water chemistry data were inter-calibrated from five different East Antarctic oases, namely the Larsemann Hills, the Bølingen Islands, the Vestfold Hills, the Rauer Islands and the Windmill Islands. Results indicate that salinity is the most important environmental variable explaining the variance in the diatom flora in East Antarctic lakes. In oligo- saline lakes the variance is mainly explained by lake water depth. This dataset was used to construct a weighted averaging transfer function for salinity in order to infer historical changes in the moisture balance. This model has a jack-knifed r² of 0.83 and a RMSEP of 0.31. The disadvantage of this transfer function is that salinity changes in oligo-saline lakes are reconstructed inaccurately due to the edge effect and due to the low species turnover along the salinity gradient at its lower end. In order to infer changes in the moisture balance in these lakes, a second transfer function using weighted averaging partial least squares (with two components) for depth was constructed. This model has a jack-knifed r² of 0.76 and a RMSEP of 0.22. Both transfer functions can be used to infer climate driven changes in the moisture balance in lake sediment cores from oligo-, hypo-, meso- and hyper-saline lakes in East Antarctic oases between 102–75°E. The transfer function for lake water depth is promising to track trends in the moisture balance of small freshwater lakes, where changes in shallow and deep-water sediments are readily reflected in changing diatom composition.  相似文献   

The Origin of the Nebulae Surrounding Luminous Blue Variable Stars     

Linda J. Smith 《Astrophysics and Space Science》1997,251(1-2):349-354

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Distribution of arsenic and other minor trace elements in the groundwater of Ischia Island (southern Italy)     

Linda?DanieleEmail author 《Environmental Geology》2004,46(1):96-103

The island of Ischia belongs to the active volcanic area of Naples. It is formed from Quaternary volcanic rocks and exhibits intense hydrothermal activity, which is manifested through numerous springs, fumaroles and sporadic geysers. The content of minor and trace elements in groundwater has been analyzed, including some elements that are considered toxic for humans. Mean concentrations of As, B, Fe, Mn, Sb, and Se in samples from 43 aquifer points exceed the WHO recommended values and the limits set by European and Italian legislation (98/83/CE and DM 471, respectively). In general, the spatial distribution of the elements follows a common pattern: it is governed by a marked structural control, which favors hydrochemical processes that liberate the elements into the water.  相似文献   

A study of fluted moraines in the Torridon area,NW Scotland     

D. M. Hodgson 《第四纪科学杂志》1986,1(2):109-118

A study of certain small-scale fluted moraines, all less than 4m high but up to 400m long, in the Torridon area has shown that they are subglacial features composed of a clast-rich till, and formed in the Loch Lomond Stadial beneath ice with a maximum depth of 100-200m. The evidence from lithological analysis of till samples from the fluted moraines suggests that they were formed by subglacial deformation of a pre-existing till with little in the way of net down-glacier movement of the material.  相似文献   

A comparison of a GCM response to historical anthropogenic land cover change and model sensitivity to uncertainty in present-day land cover representations   总被引：5，自引：1，他引：5  

Johannes Feddema  Keith Oleson  Gordon Bonan  Linda Mearns  Warren Washington  Gerald Meehl  Douglas Nychka 《Climate Dynamics》2005,25(6):581-609

This study assesses the sensitivity of the fully coupled NCAR-DOE PCM to three different representations of present-day land cover, based on IPCC SRES land cover information. We conclude that there is significant model sensitivity to current land cover characterization, with an observed average global temperature range of 0.21 K between the simulations. Much larger contrasts (up to 5 K) are found on the regional scale; however, these changes are largely offsetting on the global scale. These results show that significant biases can be introduced when outside data sources are used to conduct anthropogenic land cover change experiments in GCMs that have been calibrated to their own representation of present-day land cover. We conclude that hybrid systems that combine the natural vegetation from the native GCM datasets combined with human land cover information from other sources are best for simulating such impacts. We also performed a prehuman simulation, which had a 0.39 K ~higher average global temperature and, perhaps of greater importance, temperature changes regionally of about 2 K. In this study, the larger regional changes coincide with large-scale agricultural areas. The initial cooling from energy balance changes appear to create feedbacks that intensify mid-latitude circulation features and weaken the summer monsoon circulation over Asia, leading to further cooling. From these results, we conclude that land cover change plays a significant role in anthropogenically forced climate change. Because these changes coincide with regions of the highest human population this climate impact could have a disproportionate impact on human systems. Therefore, it is important that land cover change be included in past and future climate change simulations.  相似文献