Method for assessing the chronic toxicity of marine and estuarine sediment-associated contaminants using the amphipod Corophium volutator     

Scarlett A  Rowland SJ  Canty M  Smith EL  Galloway TS 《Marine environmental research》2007,63(5):457-470

Acute sediment toxicity tests do not test key life stage events such as moulting and reproduction and therefore do not reveal the longer-term effects of contaminant exposure. A laboratory method is described for determining the chronic toxicity of contaminants associated with whole sediments. The test is conducted using neonates of the estuarine amphipod Corophium volutator at 15 degrees C, salinity 25 psu and a 12 h light:12 h dark photoperiod. The endpoints are survival and growth after 28 days and survival, growth and reproduction of amphipods upon termination of test i.e. reproduction within all control vessels (ca 75 days). The sediment chronic toxicity test was used to investigate the effects of sediments spiked with environmentally relevant preparations of slightly weathered Alaskan North Slope crude oil, including a water-accommodated-fraction (WAF) and a chemically-dispersed (Corexit 9527) WAF. Sediment oil concentrations were quantified using ultra-violet fluorescence. The amphipods exposed to chemically dispersed oil had higher mortality and lower growth rates than control-, Corexit 9527- and WAF-exposed organisms, resulting in reduced reproduction. The described method supplements the standard acute sediment test and would be particularly useful when long-term ecological effects are suspected but acute tests reveal no significant mortality. The sediment chronic test reported herein has shown that sediment that was not evidently toxic during 10-day acute tests could have population-level effects on sediment-dwelling amphipods.  相似文献   

Vegetation monitoring for Guatemala: a comparison between simulated VIIRS and MODIS satellite data     

Vijendra K. Boken  Gregory L. Easson  James Rowland 《国际地球制图》2013,28(8):617-627

The advanced very high resolution radiometer (AVHRR) and moderate resolution imaging spectroradiometer (MODIS) data are being widely used for vegetation monitoring across the globe. However, sensors will discontinue collecting these data in the near future. National Aeronautics and Space Administration is planning to launch a new sensor, visible infrared imaging radiometer suite (VIIRS), to continue to provide satellite data for vegetation monitoring. This article presents a case study of Guatemala and compares the simulated VIIRS-Normalized Difference Vegetation Index (NDVI) with MODIS-NDVI for four different dates each in 2003 and 2005. The dissimilarity between VIIRS-NDVI and MODIS-NDVI was examined on the basis of the percent difference, the two-tailed student's t-test, and the coefficient of determination, R ². The per cent difference was found to be within 3%, the p-value ranged between 0.52 and 0.99, and R ² exceeded 0.88 for all major types of vegetation (basic grains, rubber, sugarcane, coffee and forests) found in Guatemala. It was therefore concluded that VIIRS will be almost equally capable of vegetation monitoring as MODIS.  相似文献   

EVALUATION OF MODEL PERFORMANCE WHEN THE OBSERVED DATA ARE SUBJECT TO ERROR     

R. D. Moore  J. D. Rowland 《自然地理学》2013,34(4):379-392

In many cases of model evaluation in physical geography, the observed data to which model predictions are compared may not be error free. This paper addresses the effect of observational errors on the mean squared error, the mean bias error and the mean absolute deviation through the derivation of a statistical framework and Monte Carlo simulation. The effect of bias in the observed values may either decrease or increase the expected values of the mean squared error and mean bias error, depending on whether model and observational biases have the same or opposite signs, respectively. Random errors in observed data tend to inflate the mean squared error and the mean absolute deviation, and also increase the variability of all the error indices considered here. The statistical framework is applied to a real example, in which sampling variability of the observed data appears to account for most of the difference between observed and predicted values. Examination of scaled differences between modelled and observed values, where the differences are divided by the estimated standard errors of the observed values, is suggested as a diagnostic tool for determining whether random observational errors are significant.  相似文献   

Overview and status of estuarine microphytobenthos ecological research in South Africa     

T Dalu  JB Adams  JC Taylor  GC Bate  M Nunes  PW Froneman 《African Journal of Marine Science》2018,40(1):1-12

This article presents a historical overview of estuarine microphytobenthos (MPB) research in South Africa published over the period 1950 to the present, highlighting major milestones, challenges and estuarine management problems, as well as future research needs within the South African context. The studies that were covered comprise peer-reviewed books and journal articles on relevant research conducted in any estuarine environment during the period reviewed. There was a general increase in MPB research outputs over the decades, from only two publications in the 1950s, to over 20 outputs between 2010 and the present. Whereas the MPB studies in South Africa cover a broad spectrum of themes, the research priorities in these works have changed from taxonomically biased studies to those of ecologically based research. Research in the 1950s and 1960s was exclusively taxonomic in nature, with the first ecological investigation incorporating MPB being produced in the 1970s. By the 1980s, ecological studies dominated the research outputs and this trend has persisted to the present. The 1990s and 2000s saw the rise of research into the role of fresh water as a driver of MPB dynamics, whereas the period 2010 to the present saw an increase in more diverse ecological themes, ranging from an autecological investigation to food-web studies and the assessment of multiple drivers of MPB dynamics. However, the majority of studies have focused on either diatoms or estimates of overall MPB biomass. Moreover, there is a regional underrepresentation that runs broadly along biogeographic lines, with the bulk of the work having been conducted in the warm-temperate and subtropical zones of South Africa. Challenges and future research needs for the region are outlined, as is the need to expand MPB research to include other aspects of the biology and ecology of this flora.  相似文献   

Records of subantarctic fur seals in New Zealand (Note)     

Rowland H. Taylor 《新西兰海洋与淡水研究杂志》2013,47(4):499-502

Subantarctic fur seals (Arctocephalus tropicalis) appear as stragglers on New Zealand coasts. Four records are noted, the most recent at Antipodes Island in December 1989.  相似文献   

Aircraft Measurements of Dimethyl Sulfide (DMS) Using a Whole Air Sampling Technique     

I. J. Simpson  J. J. Colman  A. L. Swanson  A. R. Bandy  D. C. Thornton  D. R. Blake  F. S. Rowland 《Journal of Atmospheric Chemistry》2001,39(2):191-213

We present a technique for the measurement of dimethyl sulfide (DMS) from airborne and ground-based platforms, using whole air sampling followed by gas chromatography with mass spectrometer and flame ionization detection. DMS measurements that were obtained during the 1999 NASA Pacific Exploratory Mission-Tropics B showed excellent agreement with independent in-flight DMS measurements, over a wide range of concentrations. The intercomparison supports two key results from this study, first that DMS can be accurately quantified based on ethane and propane per-carbon-response-factors (PCRFs), and second that DMS is stable in water-doped electropolished stainless steel canisters for at least several weeks. In addition, our sampling frequency and duration are flexible and allow detail in the vertical structure of DMS to be well captured. Sampling times as fast as 8 s were achieved and these data are suitable for DMS flux calculations using the mixed-layer gradient technique. Correlations between DMS and other marine tracers can also be readily investigated by this whole air sampling technique, because DMS is analyzed together with more than 50 simultaneously sampled hydrocarbons, halocarbons, and alkyl nitrates. The detection limit of the DMS measurements is 1 part per trillion by volume (pptv), and we conservatively estimate the accuracy to be ±20% or 3 pptv, whichever is larger. The measurement precision (1 ) is 2–4% at high mixing ratios (> 25 pptv), and 1 pptv or 15%, whichever is larger, at low mixing ratios (<10 pptv).  相似文献   

Evaluating cost-effective strategies for meeting regional CO₂ targets     

JC Bollen  AMC Toet  HJM de Vries 《Global Environmental Change》1996,6(4):359-373

Various climate protocol proposals oblige different industrialized countries to reduce CO₂ and other greenhouse gas emissions. In principle, the total costs of these obligations could be substantially reduced if emission reductions are implemented in regions with low marginal costs for CO₂ reduction. This has been difficult to quantify because of lack of models with suitable regional and sectoral detail. In this paper we perform these calculations by taking advantage of the capability of the IMAGE 2 model to compute regional emissions and costs. Two main options are examined for allocating emission reductions required of industrialized regions in a cost effective manner: (1) allocating them among industrialized regions (2) allocating them among all world regions. The cost savings for each of these options are presented. The main conclusions are that (a) it is of great importance for the cost comparisons of protocols to use a well defined baseline scenario and clearly formulated targets, and (b) large economic benefits, in the order of 35–65%, can accrue from joint-implementation agreements which allocate investments on the basis of net marginal costs of CO₂ emission reduction.  相似文献   

FLOWGO: a kinematic thermo-rheological model for lava flowing in a channel   总被引：2，自引：0，他引：2  

Andrew J. Harris  S. Rowland 《Bulletin of Volcanology》2001,63(1):20-44

We present a kinematic, self-adaptive, numerical model to describe the down-flow thermal and rheological evolution of channel-contained lava. As our control volume of lava advances down a channel it cools and crystallizes, an increasingly thick and extensive surface crust grows, and its heat budget and rheology evolve. By estimating down-flow heat and velocity loss, our model calculates the point at which the control volume becomes stationary, giving the maximum distance lava flowing in the channel can extend. Modeled effusion rates, velocities, widths, surface crust parameters, heat budget, cooling, temperature, crystallinity, viscosity, and yield strength all compare well with field data collected during eruptions at Mauna Loa, KOlauea, and Etna. Modeled lengths of 25-27, 2.5-5.7, and 0.59-0.83 km compare with measured lengths of 25-27, 4, and 0.75 km for the three flows, respectively. Over proximal flow portions we calculate cooling, crystallization, viscosity, and yield strength of 1-10°C km^-1, 0.001-0.01 volume fraction km^-1, 10³-10⁴ Pa s, and 10^-3-10² Pa, respectively. At the flow front, cooling, crystallization, viscosity, and yield strength increase to >100°C km^-1, 0.1 volume fraction km^-1, 10⁶-10⁷ Pa s, and 10³-10⁴ Pa, respectively, all of which combine to cause the lava to stop flowing. Our model presents a means of (a) analyzing lava flow thermo-rheological relationships; (b) identifying important factors in determining how far a channel-fed flow can extend; (c) assessing lava flow hazard; and (d) reconstructing flow regimes at prehistoric, unobserved, or remote flows.  相似文献   

Seasonal oxygen depletion in Chesapeake Bay     

Jay L. Taft  W. Rowland Taylor  Eric O. Hartwig  Randy Loftus 《Estuaries and Coasts》1980,3(4):242-247

The spring freshet increases density stratification in Chesapeake Bay and minimizes oxygen transfer from the surface to the deep layer so that waters below 10 m depth experiece oxygen depletion which may lead to anoxia during June to September. Respiration in the water of the deep layer is the major factor contributing to oxygen depletion. Benthic respiration seems secondary. Organic matter from the previous year which has settled into the deep layer during winter provides most of the oxygen demand but some new production in the surface layer may sink and thus supplement the organic matter accumulated in the deep layer.  相似文献   

On geography as science     

Rowland P. Moss 《Geoforum》1979,10(3):223-233

The paper attempts a preliminary exploration of some of the issues raised if we choose to account geography a “science”. The inherent equivocation of the notion of “science” is first examined, and the methodological implications are emphasised, leading into a brief consideration of inductivism and deductivism; it is concluded that deductivism, despite some valid questions which hang over it, represents the more secure methodological framework, and some of the implications of this conclusion for geographical study in general are explored. The importance of deductivism in physical geography is then considered, and the special problems of human geography are also examined, notably the significance of human volition and of value judgments in social, economic and cultural geography. The methodological implications of human perception are also reviewed. Regional geography is then briefly evaluated, and the possibilities of applying techniques of systems analysis to its problems are developed, viewing these techniques as a special phase of scientific method. Some issues relating to the notion of causality are then raised, with special reference to the crucial distinctions between the notion of causality in natural science and the related concept in historical study, and, by extension, in certain aspects of geography also. The paper concludes with a brief evaluation of the quantitative movement in geography, paying particular attention to the role of mathematics in science in general and in geography in particular.  相似文献