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1.
In the winter of 2006/2007 approximately 200,000 m3 of high quality sand from the dredging of the local marina were placed at the ocean-side beaches in the vicinity of a tourism development in Tróia, Portugal. The beach-quality sediment provided a source of “sand of opportunity” which was used to increase the dry-beach width of the highly used coastal stretch. The sediment was placed along approximately 600 m of shoreline and a monitoring program has since being carried out twice a year. High-resolution topographic surveys and sediment analysis are being conducted to evaluate the performance and response of the fill to the local forcing factors and ultimately to evaluate the effectiveness of the fill project. Two years after the nourishment, the sediment has been distributed both cross-shore and alongshore. The pre-nourishment beach slope was attained and the new shoreline has acquired a natural shape. Berm width increased by a maximum of 100 m, and a set of new dune ridges has developed, due to sand accumulation promoted by the settlement of vegetation. In conclusion, 2 years after its completion, the beach nourishment in Tróia can be viewed as a successful project in which the beneficial use of dredged material resulted in: 1) area for increased dune field growth and development, 2) enhancement of potential shorebird nesting areas and habitat, and 3) increased area for recreation purposes.  相似文献   

2.
Spatial distributions of sand beach arthropods were studied at Zouara (Nefza), a beach dune system along the northwestern coast of Tunisia. Two transects with pitfall traps, perpendicular to the shoreline and placed from sea towards land, captured spontaneously crawling arthropods. The pitfalls were used to obtain data on horizontal zonations for 2 days during different seasons (April, October). In April, in order to assess local, long-shore distributions of surface-active beach invertebrates, ten transects with pitfall traps were placed every 100 m, for 2 days. Core samples were also taken in correspondence with each of the ten transects to obtain the distribution of burrowing individuals. Sand samples were taken for successive laboratory analyses (salinity, grain size and organic contents). Local climatic conditions were also recorded. One isopod (Tylos europaeus, subdivided into three different size classes), two amphipods (Talitrus saltator, Talorchestia brito and indistinguishable juveniles) and four coleopteran species (Eurynebria complanata, Scarites laevigatus, Phytosus nigriventris, Phaleria acuminata) were considered. Mean zonations perpendicular to the shoreline showed that crustaceans were found closer to the sea-line limits than coleopterans and that between seasons some species changed their mean zonation more than others. Local, long-shore distributions of active and burrowing individuals showed that most species were unevenly distributed along the shore. These discontinuous distributions differed according to the species and age class and were mainly related to specific microclimatic conditions and to nutrition.  相似文献   

3.
The size-specific burrowing capacity of Olivella semistriata, an extremely abundant surfing gastropod of exposed sandy beaches in the tropical East Pacific, was investigated in terms of sediment grain size. For all investigated sand classes, there was a significant increase in burial time with size. Burrowing was fastest in sand with grain size between 150 and 355 μm, as well as in native sediment (median grain size 209 μm) and in field conditions (median grain size 223 μm). Values of the burrowing rate index (BRI) were found to be between 3 and 7, rating the burrowing capacity of O. semistriata to be fast to very fast. Data from previous qualitative and quantitative sampling campaigns were used to identify the macroscale (i.e., between beaches) distribution of O. semistriata in terms of sediment grain size and swash conditions. Swash period was shorter than burial time, excluding this as a factor limiting the distribution. Swash standstill time (the time between uprush and backwash), however, was just long enough on the beaches, where O. semistriata was present to allow for securing firm anchorage. On reflective beaches, the swash standstill time is as short as 1 or 2 s, denying O. semistriata the time to burry itself before being swept away by the backwash. As such, swash standstill time is advocated as a valuable part of the swash exclusion hypothesis. A survey of the available literature on the burrowing of surfers shows that mole crabs are by far the fastest burrowers and the only surfers that burrow sufficiently fast to withstand the extremely short swash standstill time on reflective beaches. Burrowing ability of surfing gastropods is found in the same range as surfing bivalves, both being insufficient to cope with coarse sediment on steep beaches. Finally, we suggest that neither burial time nor BRI, yet rather the minimal burial time—the time needed to anchor securely in a certain sand at a given swash velocity—should be used to judge the limitations of burial in terms of sediment and swash conditions.
T. VanagtEmail:
  相似文献   

4.
~~Presentation and background  相似文献   

5.
Water — and nutrient and energy — systems in urbanizing watersheds   总被引:3,自引:3,他引:0  
Driven by considerations of sustainability, it has become increasingly difficult over the past 15?C20 years ?? at least intellectually ?? to separate out the water infrastructure and water metabolism of cities from their intimately inter-related nutrient and energy metabolisms. Much of the focus of this difficulty settles on the wastewater component of the city??s water infrastructure and its associated fluxes of nutrients (N, P, C, and so on). Indeed, notwithstanding the massive volumes of these materials flowing into and out of the city, the notion of an urban nutrient infrastructure is conspicuous by its absence. Likewise, we do not tend to discuss, or conduct research into, ??soilshed?? agencies, or soilshed management, or Integrated Nutrient Resources Management (as opposed to its most familiar companion, Integrated Water Resources Management, or IWRM). The paper summarizes some of the benefits (and challenges) deriving from adopting this broader, multi-sectoral ??systems?? perspective on addressing water-nutrient-energy systems in city-watershed settings. Such a perspective resonates with the growing interest in broader policy circles in what is called the ??water-food-energy security nexus??. The benefits and challenges of our Multi-sectoral Systems Analysis (MSA) are illustrated through computational results from two primary case studies: Atlanta, Georgia, USA; and London, UK. Since our work is part of the International Network on Cities as Forces for Good in the Environment (CFG; see www.cfgnet.org), in which other case studies are currently being initiated ?? for example, on Kathmandu, Nepal ?? we close by reflecting upon these issues of water-nutrient-energy systems in three urban settings with quite different styles and speeds of development.  相似文献   

6.
<正>Water-related diseases,including diarrhea,are a leading cause of death in children of developing countries.However,they can be prevented and controlled by improving access to safe drinking water and sanitation,  相似文献   

7.
An accurate, simple and cheap extraction and cleanup procedure for capillary GC analysis of organo‐chlorine insecticides (OCs) in vegetables (cabbage and carrots) at the ng/g level, and for soil at the μg/g level is presented. The cleanup is carried out on solid‐phase extraction (SPE) cartridges, filled with 500 mg silica, 1 g of deactivated Florisil (10% w/w water), and 100 mg of anhydrous sodium sulphate. Recoveries >90% are obtained. The cleanup of OCs in fatty samples on an HPLC LiChrosorb Si 100 column is evaluated for subsequent capillary GC analysis. Fractionation of OCs and Aroclor 1254 and 1260 on an HPLC Nucleosil 100 column appears to be satisfactory.  相似文献   

8.
Eusociality in mammals is defined in the present paper by the following criteria: reproductive altruism (which involves reproductive division of labor and cooperative alloparental brood care), overlap of adult generations, and permanent (lifelong) philopatry. We argue that additional criteria such as the existence of castes, colony size, reproductive skew, and social cohesion are not pertinent to the definition of eusociality in mammals. According to our definition of mammalian eusociality, several rodent species of the African family Bathyergidae can be considered eusocial, including the naked mole-rat (Heterocephalus glaber), Damaraland mole-rat (Cryptomys damarensis), and several additional, if not all, species in the genus Cryptomys. Furthermore, some species of social voles (like Microtus ochrogaster) may also fulfill criteria of mammalian eusociality. Understanding the evolution of eusociality in mole-rats requires answers to two primary questions: (1) What are the preconditions for the development of their eusocial systems? (2) Why do offspring remain in the natal group rather than dispersing and reproducing? Eusociality in mammals is by definition a special case of monogamy (more specifically: monogyny one female breeding), involving prolonged pair bonding for more than one breeding period. We argue that eusociality in mole-rats evolved from a monogamous mating system where cooperative brood care was already established. A tendency for group living is considered to be an ancestral (plesiomorph) trait among African bathyergid mole-rats, linking them to other hystricognath rodents. A solitary lifestyle seen in some genera, such as Bathyergus, Georychus, and Heliophobius, is assumed to be a derived trait that arose independently in different lineages of bathyergids, possibly as a consequence of selective constraints associated with the subterranean environment. In proximate terms, in eusocial mole-rats either puberty is assumed to be developmentally delayed so that under natural conditions most animals die before dispersal is triggered (e.g., in the case of Heterocephalus) or dispersal is induced only by an incidental encounter with an unfamiliar, yet adequate sexual partner (e.g., in the case of Cryptomys). Ultimately, a combination of strategies involving either dispersal and/or philopatry can be beneficial, especially in a highly unpredictable environment. If genetic relatedness among siblings is high (e.g., a coefficient of relatedness of 0.5 or more), then philopatry would not invoke an appreciable loss of fitness, especially if the cost of dispersing is higher than staying within the natal group. High genetic relatedness is more likely in a monogamous mating system or a highly inbred population. In this paper, we argue that the preconditions for eusociality in bathyergid mole-rats were a monogamous mating system and high genetic relatedness among individuals. We argue against the aridity food-distribution hypothesis (AFDH) that suggests a causal relationship between cooperative foraging for patchily distributed resources and the origin of eusociality. The AFDH may explain group size dynamics of social mole-rats as a function of the distribution and availability of resources but it is inadequate to explain the formation of eusocial societies of mole-rats, especially with respect to providing preconditions conducive for the emergence of eusociality.  相似文献   

9.
The carcinogenicity of metals has received extensive study, both epidemiologically and in the laboratory. These have included case reports of occasional human occurrence or clusters of cancer cases as well as extensive epidemiologic studies; in addition, there has been significant laboratory research on the whole animals and in vitro systems. This body of information will be examined selectively.

I will not in this paper attempt a comprehensive review of the mutagenicity and carcinogenicity of metals and their compounds. Rather, I will attempt to set forth some historical perspectives, and to comment on some current gaps and needs.

Other papers in this workshop have presented thorough and very current reviews of most of the topics briefly noted in this presentation and do not require repetition here.

The cancer issue has been studied and reported on far more extensively than that relating to heritable mutations. There has been in recent years increasing interest in the use of short term tests for mutagenicity and cell transformation. These, however, are primarily with respect to their relationship to cancer production rather than to germ cell injury. Interest in cancer from metal compounds goes back a long time; in fact, one of the earliest reports was on the carcinogenicity of arsenic not many decades after the pioneering report of Sir Perceval Pott on cancer in chimney sweeps. Since then cancer has been definitely associated in humans with chromium compounds, nickel, and with less assurance but probably definitely with beryllium and cadmium. The confirmation of these findings in laboratory animals has been uneven. In the case of arsenic, for example, there has been only limited success in the production of cancer in laboratory animals with arsenic.

Many other metals have been found in laboratory studies to produce cancer, although with most of these, evidence of production of cancer in humans is either absent or extremely uncertain.

The extensive body of recent information relating to the testing of metals with a variety of short term tests will be briefly reviewed.  相似文献   

10.
Environmental pollution and climate change are requiring new methods to clean pollutants and produce sustainable energy. Aerogels and metal organic frameworks are emerging as advanced porous materials with higher functionality, high surface area, high porosity and flexible chemistry. Aerogels are dried gels prepared using the sol–gel procedure, whereas metal organic frameworks are networks of organic ligands and metal ions connected by coordination bonds. Applications of aerogels include the removal of heavy metals, CO2 capture and reduction, photodegradation of pollutants, air cleanup and water splitting. This article reviews the synthesis and types of aerogels and metal organic frameworks, and the application to pollutant removal, energy production including hydrogen, methane reforming, CO2 conversion and NOx removal.  相似文献   

11.
Summary.  ((no summary.))A corrected version of the appendix is available for free download from  相似文献   

12.
The common occurrence of food transfers within human hunter–gatherer and forager–horticulturalist groups presents exciting test cases for evolutionary models of altruism. While kin biases in sharing are consistent with nepotism based on kin selection, there is much debate over the extent to which reciprocal altruism and tolerated scrounging provide useful explanations of observed behavior. This paper presents a model of optimal sharing breadth and depth, based on a general non-tit-for-tat form of risk-reduction based reciprocal altruism, and tests a series of predictions using data from Hiwi and Ache foragers. I show that large, high variance food items are shared more widely than small, easily acquired food items. Giving is conditional upon receiving in pairwise interactions and this correlation is usually stronger when the exchange of value rather than quantities is considered. Larger families and low producing families receive more and give less, consistent with the notion that marginal value may be a more salient currency than quantity.
Michael GurvenEmail: Phone: +1-805-8932202
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13.
The interaction of HCH (50 mg/kg) and dietary protein levels on microsomal drug metabolizing enzymes system and liver lipids were studied in the rats for 90 days. The results indicated that rats fed a lower protein diet and HCH has a higher rate of mortality, lower rate of growth and an increased liver weight. A significant induction in the hepatic microsomal aminopyrine‐N‐demethylase, p‐nitroanisole‐O‐dealkylase, benzo(a)pyrene hydroxylase and glutathione‐S‐transferase activity was observed in pesticide treated animals as compared to control animals. The pathological changes observed in liver of HCH treated animals consisted mainly of necrosis and fatty degeneration of hepatocytes. HCH also induced the significant accumulation of cholesterol, triglycerides, phospholipid and total lipid in liver in low protein diet animals. Protein accelerates the metabolism of HCH, resulting in a decrease of HCH concentration with the increase of dietary protein level. A close correlation existed between lipid accumulation, induction of drug metabolizing enzyme system and deposition of HCH in liver.  相似文献   

14.
Summary. Qualitative and quantitative differences among pear cultivars were found in constitutive and Cacopsylla-induced volatiles, depending on experimental treatment of the trees (i.e., uninfested and partly or completely infested by psyllids). Blend differences were also found between pear cultivars and wild-type pear, alder and hawthorn–the latter trees are frequently present in pear orchard hedgerows. ?Interesting differences were found in the presence of methyl salicylate and (E,E)-α-farnesene, two compounds previously found to mediate attraction of predatory bugs towards psyllid-infested pear trees. Methyl salicylate is expressed constitutively and is induced systemically by infestation in the whole plant of all four cultivars. (E,E)-α-farnesene on the other hand showed also systemic induction in Bartlett, NY10355 and Beurré Hardy, but in partially infested Conference trees it was induced locally, only in herbivore-damaged leaves. No methyl salicylate or (E,E)-α-farnesene were identified in honeydew. In field collected headspace samples of alder leaves infested by aphids and leaf beetles we found methyl salicylate but no (E,E)-α-farnesene, whereas in uninfested hawthorn neither were identified. Insight in the variability of damage-related pear volatiles will have important implications for integrated pest management in the field. Received 27 August 2002; accepted 28 November 2002 R1D=" Correspondence to: Petru Scutareanu, e-mail:scuterea@science.uva.nl  相似文献   

15.
Ammonium concentrations of ∼1 M are commonly cited as being the threshold for inhibition of NO3 uptake, but the applicability of this threshold to phytoplankton from different taxonomic classes has rarely been examined. Additionally, little is known about the influence of environmental variables (e.g. growth temperature) on the interaction between ambient NH4 + and NO3 uptake. Four species of estuarine phytoplankton, two diatom [Chaetoceros sp., and Thalassiosira weissflogii (Grunow) Fryxell et Hasle] and two dinoflagellate [Prorocentrum minimum (Pavillard) Schiller, and Gyrodinium uncatenum Hulburt], were grown on NO3 at several different temperatures (4, 10, 15, or 20 °C), and the impact of NH4 + additions on NO3 uptake/assimilation (non-TCA-extracted) and assimilation (TCA-extracted) was assessed. For all species at all temperatures, NO3 uptake/assimilation and assimilation rates decreased in a roughly exponential manner with increasing NH4 + concentrations but were not completely inhibited even at elevated NH4 + concentrations of 200 μM. Estimated half-inhibition concentrations (K i) were significantly greater in the diatom species (mean ± SE; 2.70 ± 0.67 μM) than in the dinoflagellate species (1.26 ± 0.55 μM). Half-inhibition constants were positively related to temperature-limited relative growth rate although not significantly. The observed inhibition of NO3 uptake and assimilation, as a percentage of NO3 uptake in the absence of NH4 +, averaged about 80% and ranged from 49 to 100%. For all species, a significant (P < 0.001) positive correlation was found between percent inhibition of NO3 assimilation and temperature-limited relative growth rate. Two experiments on Chesapeake Bay phytoplankton during an April 1998 diatom bloom showed that in short-term (∼1 h) temperature manipulation experiments, percent inhibition of NO3 uptake/assimilation was also positively related (P = 0.05) to experimental temperature. The observed relationships between temperature-limited relative growth rate and percent inhibition of NO3 assimilation rates for the species tested suggest that at the enzyme level, the inhibitory mechanism of NO3 assimilation is similar among species, but at the whole cell level may be regulated by species-specific differences in the accumulation of internal metabolites. These findings add not only to our understanding of species-specific variability and the role of growth temperature, but also provide additional data with which to evaluate current models of NH4 + and NO3 interactions. Received: 31 August 1998 / Accepted: 7 December 1998  相似文献   

16.
Sampling of PCDDs/Fs in flue gas from a MSW incinerator was conducted using a modified apparatus of the 5 train method, which has been widely used for the sampling of PCDDs/Fs emission. In the atmosphere a high volume air sampler with special packings was used. Collection efficiencies of PCDDs/Fs were more than 98% for both samplers, using 13C12—PCDD reference standard isomers. It was suggested that these sampling methods were adaptable for the measurements of PCDDs/Fs at sources and in the environment. To validate the applicability of existing methodologies on the PCDD/F determination, interlaboratory comparisons were undertaken. From high resolution GC/MS analysis, 2,3,7,8‐TCDD concentrations in reference ash samples were 0.052±0.013 ng/g as comparable results between the laboratories. In addition, the daily intakes of PCDDs/Fs for exposed persons in the MSW incineration facilities in Japan were estimated ranging of 0.053 to 0.28 pg/kg/day by the international toxic equivalent calculations.  相似文献   

17.
Air quality in schools is an important public health issue because children spend a considerable part of their daily life in classrooms. Particulate size and chemical composition has been associated with negative health effects. We studied levels of trace element concentrations in fine particulate matter (PM2.5) in indoor versus outdoor school settings from six schools in Chañaral, a coastal city with a beach severely polluted with mine tailings. Concentrations of trace elements were measured on two consecutive days during the summer and winter of 2012 and 2013 and determined using X-ray fluorescence. Source apportionment and element enrichment were measured using principal components analysis and enrichment factors. Trace elements were higher in indoor school spaces, especially in classrooms compared with outdoor environments. The most abundant elements were Na, Cl, S, Ca, Fe, K, Mn, Ti, and Si, associated with earth’s crust. Conversely, an extremely high enrichment factor was determined for Cu, Zn, Ni and Cr; heavy metals associated with systemic and carcinogenic risk effects, whose probably origin sources are industrial and mining activities. These results suggest that the main source of trace elements in PM2.5 from these school microenvironments is a mixture of dust contaminated with mine tailings and marine aerosols. Policymakers should prioritize environmental management changes to minimize further environmental damage and its direct impact on the health of children exposed.  相似文献   

18.
19.
Ammonia oxidation, the first and rate-limiting step of nitrification, is mainly performed by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, the activities of AOA and AOB in soil and their relative contribution to ammonia oxidation are unclear, and whether there is a significant correlation between the quantity of AOA and AOB and the ammonia oxidation rate is also controversial. In this study, quantitative PCR combined with acetylene (C2H2) and 1-octyne inhibition methods were used to determine the quantity and activity of AOA and AOB in wheat, highland barley, and oilseed rape soils in Nyingchi, Lhatse, Sangzhuzi, and Sangri counties on the Qinghai-Tibet Plateau. The results showed that the quantity of AOB ((2.34 ± 0.84) ×105 - (2.65 ± 1.07) ×106 copies g-1 dry soil) was significantly higher than that of AOA ((0.20 ± 0.10) ×104 - (4.02 ± 0.39) ×104 copies g-1 dry soil) in all the soil samples. Soil pH was the key factor affecting the quantity of AOB, and the total phosphorus and ammonium nitrogen in soil were the key factors affecting the quantity of AOA. The rates of ammonia oxidation in the farmland soils of Lhatse (2.42 ± 0.73 mg kg-1 d-1) and Sangzhuzi (3.24 ± 1.15 mg kg-1 d-1) were significantly higher than those in the soils of Nyingchi (1.17 ± 0.43 mg kg-1 d-1) and Sangri counties (0.88 ± 0.57 mg kg-1 d-1). The rates of ammonia oxidation in the farmland soils of Lhatse and Sangzhuzi were dominated by AOB, while those in the farmland soils of Nyingchi and Sangri counties were dominated by AOA. For crops, the ammonia oxidation rates of wheat and oilseed rape soils in all four regions were significantly higher than those of highland barley soil, whereas the activity of AOA and AOB was not influenced by crops. The ratio of nitrogen to phosphorus was the key factor influencing AOA activity, whereas soil pH and total carbon were the main factors influencing AOB activity. Additionally, the quantities of AOA and AOB were not significantly correlated with the total ammonia oxidation rates and AOA and AOB activity. Overall, our study suggests that both AOA and AOB play important roles in ammonia oxidation in farmland soils of the Qinghai-Tibet Plateau. Moreover, it is unreliable to predict the activity of AOA and AOB and their relative contribution to ammonia oxidation directly based on their number of amoA genes, and the activity of AOA and AOB should be directly and accurately measured. These results are important for understanding ammonia nitrogen removal processes, slowing nitrate loss, and reducing the emission of the greenhouse gas nitrous oxide in the farmland ecosystem of the Qinghai-Tibet Plateau. © 2022 Science Press. All rights reserved.  相似文献   

20.
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