Risk reduction measures of large wood accumulations at bridges

Environmental Fluid Mechanics - Bridges with and without piers are prone to large wood (LW) accumulations during floods, possibly resulting in an upstream backwater rise, local scour, or...     

Coupling check dams with large wood retention structures in clean water

Environmental Fluid Mechanics - The performance of a rake for large wood retention has been analysed in clean water and for the case of a slit check dam. An experimental investigation was conducted...     

Use of the “Acetylene blockage” technique for assaying denitrification in a salt marsh

The acetylene blockage technique was evaluated for measurement of denitrification in salt-marsh sediments (near Halifax, Nova Scotia, Canada). N₂O in the gas phase of closed Spartina alterniflora marsh-sediment systems was analyzed with use of a thermal conductivity gas chromatograph sensitive to approximately 0.1 nmoles ml^-1 gas. No N₂O was detected for unfertilized sediment samples taken through the growing season and incubated in sealed buckets with 10% C₂H₂. For sediment samples amended with nitrate and for enrichments, initial rates of N₂O evolution were higher in the presence of 10% C₂H₂ than in the absence of C₂H₂, but after longterm incubation N₂O was consumed in some samples containing C₂H₂ as well as in samples without C₂H₂. In addition, total gaseous nitrogen (N₂ and N₂O) production in the absence of C₂H₂ was higher than in the presence of C₂H₂. Acetylene appears to be an inconsistent inhibitor of N₂O reduction in salt-marsh sediments. The usefulness of the acetylene-denitrification technique in this habitat is, therefore, questionable.     

Integral projection models for finite populations in a stochastic environment

Continuous types of population structure occur when continuous variables such as body size or habitat quality affect the vital parameters of individuals. These structures can give rise to complex population dynamics and interact with environmental conditions. Here we present a model for continuously structured populations with finite size, including both demographic and environmental stochasticity in the dynamics. Using recent methods developed for discrete age-structured models we derive the demographic and environmental variance of the population growth as functions of a continuous state variable. These two parameters, together with the expected population growth rate, are used to define a one-dimensional diffusion approximation of the population dynamics. Thus, a substantial reduction in complexity is achieved as the dynamics of the complex structured model can be described by only three population parameters. We provide methods for numerical calculation of the model parameters and demonstrate the accuracy of the diffusion approximation by computer simulation of specific examples. The general modeling framework makes it possible to analyze and predict future dynamics and extinction risk of populations with various types of structure, and to explore consequences of changes in demography caused by, e.g., climate change or different management decisions. Our results are especially relevant for small populations that are often of conservation concern.     

Fate of turbid glacial inflows in a hydroelectric reservoir

Environmental Fluid Mechanics - Turbidity from glacial meltwater limits light penetration with potential ecological consequences. Using profiles of temperature, conductivity, and turbidity, we...     

Carbon black-benzo(a)pyrene complex-induced apoptosis and autophagy blockage in rat alveolar macrophages

Abstract

Cooking of foods and the burning of biomass and fossil fuels in stoves are the main sources of cooking fumes, with carbon black and polycyclic aromatic hydrocarbons as main components. The toxicity of carbon black and polycyclic aromatic hydrocarbons has been well studied individually, but the combined toxicity is much less understood. Carbon black can adsorb benzo(a)pyrene to form a complex which displays an altered physical form which in this study has been constructed to simulate particles in the cooking fumes and explore the combined toxic effect on rat alveolar macrophages. The complex-induced cell apoptosis and blocked cell autophagy flux compared with both individually. The mechanism of toxicity may be by intracellular reactive oxygen species generation, impairing the mitochondrial membrane potential and activating apoptosis signaling pathways.     

Seaweeds as a reservoir of Candida yeasts in inshore waters

The yeast populations on 9 species of seaweeds and in seawater were estimated by cultural methods over a 16-month period in Narragansett Bay, Rhode Island (USA). Maximal numbers occurred on rhodophytes and a chlorophyte, while the lower numbers on phaeophytes were attributed to the release of inhibitory polyphenolic materials. All divisions of algae showed a similar seasonal variation in yeast populations, correlated with trends in solar radiation and water temperature which would affect both the host and its microflora. The exposure of intertidal algae to unseasonable air temperatures apparently has a detectable effect on their microflora. The population changes in the water surrounding the seaweeds paralleled those on the plants. Only colorless yeasts of the genus Candida were observed, except for brief occurrences of the pink yeast Rhodotorula in late spring, when it accounted for 3 to 35% of the yeast community. Ninety five percent of the 362 representative isolates were strains of Candida. The published properties of the 84 species accepted in the genus Candida were compared with those of the marine isolates using numerical analysis. There were 7 groups: 1 solely of named species, 3 small groups with both named species and marine isolates, and 3 large groups with only one or two named species that contained 75% of the seaweed and sea-water isolates. An apparent successional sequence for three groups may be due to differences in their biochemical activity. The same three groups were preferentially enriched by 5 of the algal species. The role of this persistent yeast population as a reservoir of inshore yeasts is discussed.     

Lead in a residential environment in Jamaica

The background levels of lead in Jamaica in soils and sediments, estimated at 37 mg kg^–1, are relatively high compared with world averages. Several areas have values in excess of this due to mineralisation and pollution. One such is the residential Hope Flats/Kintyre area in which levels of lead up to 2.5% are found in the soils and up to 8 g kg^–1 in the water of the nearby Hope River. The blood lead levels of a sample of children were in the range 5.7–57 g dl^–1. The high lead levels suggest a potential health risk, particularly for the children. This can be minimised by programmes which include community education, case management and abatement to reduce the lead exposure.     

A simulation model of carbon and oxygen dynamics in a reservoir

The CORES model represents the long-term carbon and oxygen dynamics of the Conowingo Reservoir. The model, formulated using subsetted historical data, is readily validated using the remaining historical data for all state variables of importance. Sensitivity analyses make it clear that the flux of particulate organic carbon from upstream sources and its subsequent “trapping” and metabolism in the deeper regions of the reservoir are the major factors controlling the oxygen declines historically observed in the summer months. Increased natural vertical mixing (i.e., transport of oxygen from shallow to deep waters) can increase deep-water oxygen concentrations to some extent, but not to the degree necessary to meet water quality standards. Air-to-water diffusion adds substantial quantities of oxygen to surface waters in these mixing events. Simple solutions, such as requiring continuous flow, do not appear to adequately increase the dissolved oxygen levels in the deeper portion of the reservoir.     

Optimal energy use in a polluted environment

Some of the basic issues involved in the optimal intertemporal use of energy resources when there are environmental spillovers are examined at a macroeconomic level and in a world of certainty. Several scenarios are considered with varying assumptions concerning the depletability of the energy resource stock and the nature of pollution production. In particular, with an accumulating form of pollution it is shown that initially the energy resource should be used more slowly to reduce environmental damage and over the plan the rate of use should be increased—a counter-Hotellian result.     

Adaptation of a four-arm olfactometer for behavioural bioassays of large beetles

Summary. We adapted a four-arm olfactometer (55 × 55 × 5.5 cm) for bioassays of large insects and its usefulness was evaluated by testing the responses of three beetles, the palm weevil Rhynchophorus palmarum (L.) (Coleoptera: Curculionidea) and two Dynast scarabs Strategus aloeus (L.) and Oryctes rhinoceros (L.) (Coleoptera: Scarabaeidae) to plant odours and aggregation pheromones. This olfactometer was coupled to a volatile delivery system dispensing highly volatile semiochemicals at constant concentrations. We materialized airflows in the olfactometer by discolouring sensitive papers with acid vapours under various conditions (air straighten by stainless steel grids in inputs and output, 500 ml/min per arm) to visualize air turbulence and to test air-tightness. The volatile delivery system can be used to mix and dispense a broad range of concentrations of semiochemicals in air from diluted aqueous solutions. It was calibrated by measuring the release of the pheromone using solid phase-microextraction (SPME). Dose-response curves to synthetic pheromone were obtained for O. rhinoceros of both sexes. Coupling the volatile delivery system to the fourarm olfactometer provided a system with which the responses of R. palmarum and S. aloeus to their synthetic aggregation pheromones and to natural plant volatiles could be readily observed and studied.     

Modeling and interpreting the accuracy assessment error matrix for a doubly classified map

This paper considers two maps having the same spatial extent and the same mapping categories but where each map is subject to classification error. An overlay of the maps yields a (dis)similarity matrix whose (i, j)-entry is the areal proportion placed into category i by the first map and into category j by the second map. A parametric model, called the latent truth model, is proposed which specifies the dissimilarity matrix in terms of the true (but unknown) proportions for the mapping categories as well as the unknown error rates for the two maps. The number of parameters in the model exceeds the degrees of freedom in the dissimilarity matrix. However, a method of regularization is applied to effectively reduce the dimension of the parameter space and to permit model fitting. From the fitted model, one obtains estimates for the true mapping proportions as well as estimated error matrices for each of the maps. Accuracy assessment characteristics for each map (such as user's accuracy, producer's accuracy, overall accuracy, and the kappa coefficient) can be computed from the estimated error matrices. Methods are illustrated with two landcover maps of Wicomico County, Maryland.     

Red soil geochemistry in a semiarid Mediterranean environment and its suitability for vineyards

A geochemical study of a red soil derived from plioquaternary materials was carried out. The soil was located in a region of complex geomorphology and pedologic evolution, with particular characteristics of a Mediterranean climate associated with processes of alteration, rubification, gleying (hydromorphism) and argillization. The depth distribution of 27 trace elements was studied in order to determine the amounts of these elements in the soil and its tendency. The mineralogy of the clay fraction was also studied along with other physico-chemical properties to elucidate in terms of attributes meaningful for viticulture. The geochemical composition of the horizons was studied. The effect of human activities on the soil was investigated as well as the geographical origin of Mancha wines. It was found that these activities did not give rise to significant variations of trace elements, although a discontinuity related to the accumulation of new materials was detected. Ultimately, using established productivity standards, suitability for the cultivation of vines on these soils was determined.     

Tetracycline antibiotics in the environment: a review

Tetracycline antibiotics are one of the primarily antibiotics groups used for veterinary purposes, for human therapy and for agricultural purposes. Amongst the different antibiotics used, more attention is paid to tetracycline’s as it exhibits serious environmental problems including ecological risks and human health damages. Due to their extensive usage, most of the actual evidence suggests that tetracycline antibiotics are omnipresent compounds found in different ecological compartments. After medication, more than 70 % of tetracycline antibiotics are excreted and released in active form into the environment via urine and feces from humans and animals. Their highly hydrophilic character and low volatility have resulted in significant persistence in the aquatic environment. Very few studies describe the fate and toxicity of tetracycline antibiotics in the environment. Here, we review several important issues with regard to: (1) the toxicity of these compounds on aquatic and terrestrial organisms; (2) their estrogenic effects; (3) their behavior in different ecological systems and; (4) the by-products generated during water treatment. These antibiotics residues promote the development of antibiotic resistant microorganisms, which can induce adverse effect to human health by increasing the risk of certain infections. Based on recent research results, the occurrence of tetracycline antibiotics in the environment inhibits the growth of some terrestrial and aquatic species. Besides, the residual concentrations of such drugs could affect steroidogenic pathway and consequently may cause endocrine disruption of aquatic species. Most of the wastewater treatment plants are not capable of removing effectively the tetracycline antibiotics. Therefore, there is a need to develop alternative processes to remove them from waters. Advanced oxidation processes have been proposed as alternative methods to ensure higher degradation and mineralization of tetracycline antibiotics are present in waters.     

水库流域生态补偿标准测算体系研究——以大伙房水库流域为例

生态补偿标准的测算是建立生态补偿机制的核心问题,也是难点所在。研究在对现有生态补偿标准计算方法进行总结分析的基础上,分别从供给方和需求方的角度探索建立了水库流域生态补偿标准测算体系。该体系对基于水库上游水源涵养区生态系统服务功能、生态保护建设总成本和基于下游用水城市意愿支付价格的补偿标准进行了比较分析,最终选择一个既能使水消费者承受得起,又能使生态保护者体会到有所回报的补偿金数额作为上下游协商确定补偿标准的依据。此体系较为全面地对补偿标准进行了测算,使得补偿标准更为公平、合理,进一步完善了水库流域生态补偿标准测算方法。并以大伙房水库流域为例,对其补偿标准进行测算,得出基于研究区生态系统服务功能的补偿标准为64661.3万元,基于研究区生态保护建设总成本的补偿标准为9221.4万元,基于下游用水城市意愿支付价格的补偿标准分别为8637.6万元、12956.4万元,最终认为10000万元是令补偿双方都比较容易接受的一个价格,可作为确定补偿标准的依据。