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551.
Sansone U Belli M Jeran Z Kanivets VV Radojko J Riccardi M Voitsekhovitch OV 《Journal of environmental radioactivity》2002,59(3):257-271
Suspended particle adhesion on aquatic biota can significantly increase the apparent concentration of radionuclides above their endogenous value, leading to an overestimation of the uptake rate and concentration ratios. This study is an attempt to assess quantitatively the importance of suspended particle adhesion on periphyton samples (biological material coating submerged surfaces). The concentrations of 137Cs and stable Cs (133Cs) in periphyton, suspended particles and filtered water were measured to determine the net water-to-periphyton concentration ratios for 137Cs and stable Cs. The net amount of 133Cs (or 137Cs) taken up by periphyton was calculated by subtracting from the total amount of 133Cs (or 137Cs) on the collected material (periphyton + inorganic particles), the 133Cs (or 137Cs) due to the inorganic particles adhering to periphyton. The mass of suspended particles adhering to the periphyton surface was calculated using scandium as an indicator of the mineral fraction of the suspended particles. The relationship between the concentration ratios for 137Cs and stable Cs and suspended particle adhesion on periphyton external surfaces is discussed. 相似文献
552.
These investigations present qualitative and quantitative assessments of the 222Rn contributing potential of the technologically modified sources, e.g. mine exhausts and tailings piles, arising due to the mining and processing of uraniferous minerals at Jaduguda, India. The overall geometric mean of the 222Rn flux from low-grade uranium (U) mill tailings being 1.19 Bq m-2 s-1, requisite attenuation of 37.8% to the recommended limit of 0.74 Bq m-2 s-1 can be attained by a typical clay coverage of 20 cm. Theoretically, feasible options for selection of overburden materials for stabilisation of the tailings piles are examined. Extrapolation studies with a turbulent diffusion model yield an atmospheric dispersion pattern of 222Rn in reasonable correspondence with the prevailing concentrations, especially for locations beyond a 4 km radius. The overall 222Rn contribution of the U complex to the ambient air is the same as that contributed by the adjoining land mass of 2.75 km radius in this mineralised terrain. 相似文献
553.
Estimates of soil N2O and NOemissions at regional and country scales arehighly uncertain, because the most widely usedmethodologies are based on few data, they do notinclude all sources and do not account forspatial and seasonal variability. To improveunderstanding of the spatial distribution of soilNO and N2O emissions we have developedsimple multi-linear regression models based onpublished field studies from temperate climates.The models were applied to create spatialinventories at the 5 km2 scale of soil NOand N2O emissions for Great Britain. The N2O regression model described soilN2O emissions as a function of soil N input,soil water content, soil temperature and land useand provided an annual N2O emission of 128 kt N2O-N yr-1. Emission rates largerthan 12 kg N2O-N ha-1 yr-1 werecalculated for the high rainfall grassland areasin the west of Great Britain.Soil NO emissions were calculated using tworegression models, which described NO emissionsas a function of soil N input with and without afunction for the water filled pore space. Thetotal annual emissions from both methods, 66 and7 kt NO-N yr-1, respectively, span the rangeof previous estimates for Great Britain. 相似文献
554.
The inflow and stock (amount in use) of heavy metals (cadmium(Cd), chromium (Cr), copper (Cu), lead (Pb), mercury (Hg), nickel (Ni) and zinc (Zn)) in goods in 1995 have been quantifiedin the anthroposphere of Stockholm, Sweden. Statistics on national, regional and local level were used. Contacts were established with representatives from production and constructionin the industrial sector and with authorities. The results show that the stock of Cd is 0,2 kg per capita. For the other heavymetals the corresponding result per capita is: Cr 8, Cu 170, Hg 0,01, Ni 4, Pb 73 and Zn 40 kg. The inflow varies between2–8%of the stock indicating the importance of the stock. The lowestlevels are for Cu and Pb. Heavy metal levels in solid waste are high, between 15–45% of the amount in the inflow (Hg excluded), the lowest values were for Cu and Pb. Thus, recyclingis incomplete. Long life expectancy goods form the majority of the stock but there is a tendency that short life expectancy goods increase their importance in the inflow. Concealedgoods are also more frequent in inflow than in the stock. 相似文献
555.
Small cephalopods of the genus Heteroteuthis are the most pelagic members in the family Sepiolidae. This study examines the reproductive biology of Heteroteuthis dispar (Rüppell, 1844), the first such study on any member of the genus, based on 46 specimens (27 females and 19 males) collected
during the Mar-Eco cruise in the North Atlantic in the region of the Mid-Atlantic Ridge in 2004, and compares it with reproductive
features in the less pelagic members of the family. The unusually large spermatophores of the males have a very small ejaculatory
apparatus and cement body, relative to the size of the sperm mass. Females first mate when they are still maturing: a large
sperm mass (up to 3.4% of the female body mass), consisting of one to several spermatangia, was found in an internal seminal
receptacle of the majority of the females examined regardless of their maturity state. The seminal receptacle has a unique
form and position in this species. The receptacle is a thin-walled sac at the posterior end of the visceral mass that is an
outpocketing of, and opens into, the visceropericardial coelom. Spermatangia and sperm from the spermatangia apparently enter
into the visceropericardial coelom (which is mostly occupied by the ovary) from the seminal receptacle indicating that ova
are fertilised internally, a strategy unknown for decapodiform cephalopods (squid and cuttlefish), but present in most octopods.
Fecundity of Heteroteuthis dispar (1,100–1,300 oocytes) is much higher than in other sepiolids whereas the egg size (mean max. length ∼1.6 mm) is the smallest
within the family. Spawning is continuous (sensu Rocha et al. in Biol Rev 76:291–304, 2001). These and other reproductive traits are discussed as being adaptations to an oceanic lifestyle. 相似文献
556.
Mercury is recognized internationally as an important pollutant since mercury and its compounds are persistent, bioaccumulative and toxic, and pose human and ecosystem risks. A critical aspect of mercury cycling is its bioaccumulation, mainly as methylmercury, along the aquatic food web resulting in high risk of human exposure through contaminated fish consumption. Since lake acidity (pH) and mercury methylation are correlated, control of lake pH through lake liming is a possible option to mitigate mercury bioaccumulation. This work proposes to use optimal control theory to derive time-dependent lake liming strategies for a tighter control of lake pH. Since the behavior of the freshwater ecosystems such as lakes is often associated with considerable uncertainties, a robust and realistic analysis should incorporate such uncertainties. This work models the time-dependent uncertain variations in the basic lake pH value and derives the liming profiles in the presence of such seasonal pH fluctuations. Established techniques from real options theory are employed for modeling the uncertainty as a stochastic process, and stochastic optimal control is used for deriving liming profiles. The approach is critically evaluated through applications to various case study lakes. Considering the substantial costs associated with liming operations, the work formulates a multi-objective problem highlighting the tradeoff between accurate pH control and liming cost. The results of the control problem solution are also compared with heuristics based liming. The results, while highlighting the success of using time-dependent liming, put forth certain interesting aspects that might be helpful to a decision maker. The analysis is expected to make liming operation more reliable, thereby presenting one more tool to manage the harmful effects of mercury pollution. 相似文献
557.
GVO-Pollenmonitoring zum Bt-Maisanbau im Bereich des NSG/FFH-Schutzgebietes Ruhlsdorfer Bruch 总被引:1,自引:1,他引:0
F. Hofmann R. Epp A. Kalchschmid L. Kruse U. Kuhn B. Maisch E. Müller S. Ober J. Radtke U. Schlechtriemen G. Schmidt W. Schröder W. v. d. Ohe R. Vögel N. Wedl W. Wosniok 《Environmental Sciences Europe》2008,20(4):275-289
Aim and Background Precautionary regulations for the production of genetically modified crops (Gentechnik-Pflanzenerzeugungsverordnung, GenTPflEV 2008) provide isolation distances for the cultivation of genetically modified maize – Bt-maize – in the vicinity of conventional maize cultivation (150?m) as well as of organic maize cultivation (300?m). Nature reserves are not included. The aim of this study was to investigate whether maize pollen of surrounding fields were dispersed in the Flora-Fauna-Habitat (FFH) Ruhlsdorfer Bruch. In the vicinity of the nature reserve Bt-maize species MON 810 as well as conventional maize was grown. The survey should provide appropriate isolation distances for the cultivation of Bt-maize with regard to sustainable protection of non-target-organisms (NTO) in the Ruhlsdorfer Bruch. Materials and Methods The collection of maize pollen in the Ruhlsdorfer Bruch was carried out at three sampling sites in the FFH or rather in the immediate vicinity in July and August 2007 by means of twelve technical and three biological pollen samplers. The technical samplers Sigma-2/PMF enable point sampling. They are primarily influenced by wind and topography and provide information about the effective entry, the maize pollen flow and the maize pollen deposition at the location of the sampler. Honey bees roam over longer distances and are hence planar collectors. Thus, they also provide information about the plants blooming in a distinct area. Furthermore, the biological preferences during the collection are captured, whereas a technical sampler does not perform a species dependent selection. Hence, both the technical and the biological samplers complement one another in their scope of application. The pollen samples were identified microscopically, enumerated quantitatively, and the pollen-DNA was analysed by means of the PCR-method. Results All monitoring sites at the Ruhlsdorfer Bruch revealed maize pollen entries. The pollen deposition reached values of 1.75 million maize pollen/m² in the close-up range. The monitoring sites located 120?m within the protected area still featured 99,000 maize pollen/m². As shown by the statistical analysis, at a distance of 1,000?m still 28,000 maize pollen/m² must be expected. The results of the microscopic pollen analysis of the pollen pellets proved that the bees collect maize pollen at all three sites. Although maize pollen is not the main food source the high collection efficiency of the bees resulted in large amounts of introduced pollen. The biomolecular proof of pollen-DNA in the field samples was corroborated by analogue results for both the technical and biological pollen sampling by two independent laboratories. The results of these quality controlled analyses gave unambiguous evidence that under the cultivation conditions in 2007 an entry of Bt-maize pollen into the FFH Ruhlsdorfer Bruch was existent. Discussion The maize pollen deposition at the Ruhlsdorfer Bruch corresponds with additional supra-regional investigations which were conducted over several years with the same method. However, the pollen entries into the Ruhlsdorfer Bruch are above-average. Possible reasons are the size of the maize fields (>?10?ha), the geographical collocation between maize fields and protected area (lee location, through-shaped, thermal currents) as well as weather conditions and maize bloom during the sampling period July and August 2007. A distance of 1,000?m or more is necessary to avoid maize pollen deposition of more than 100,000/m² with a probability of 90?%. Conclusions The results of this investigation prove an entry of Bt-maize pollen into the FFH under the cultivation and weather conditions in summer 2007. According to the results of this and related studies and considering precautionary principle and the effect terms defined in the Federal Immission Protection Law, it becomes clear that reasonable isolation distances between Bt-maize fields and protected areas have to be introduced in order to minimise the entry of GM-maize pollen and to prevent adverse effects on protected NTOs. Recommendations Due to the fact that no toxicological investigations are available for the butterflies occurring in the FFH, highest protection standards should be implemented to avoid Bt-maize pollen entries into the Ruhlsdorfer Bruch. That implies that highest possible isolation distances for Bt-maize cultivation have to be considered, but at least a distance of 1,000?m is recommended. Following this a maize pollen deposition of more than 100,000 maize pollen/m² should be pevented with a certainty of 90?% as well as an exceeding exposure of foraging insects. Outlook By means of the pollen monitoring it becomes possible to survey empirically defined limits of pollen exposure. This should be performed in the nature reserve area at sites of expected maximum exposure, e.?g. at the boundaries of the FFH towards the maize fields and at exposed sites. 相似文献
558.
A health risk assessment for fluoride in Central Europe 总被引:4,自引:0,他引:4
Fordyce FM Vrana K Zhovinsky E Povoroznuk V Toth G Hope BC Iljinsky U Baker J 《Environmental geochemistry and health》2007,29(2):83-102
Like many elements, fluorine (which generally occurs in nature as fluoride) is beneficial to human health in trace amounts,
but can be toxic in excess. The links between low intakes of fluoride and dental protection are well known; however, fluoride
is a powerful calcium-seeking element and can interfere with the calcified structure of bones and teeth in the human body
at higher concentrations causing dental or skeletal fluorosis. One of the main exposure routes is via drinking water and the
World Health Organisation currently sets water quality guidelines for the element. In Central Europe, groundwater resources
that exceed the guideline value of 1.5 mg l−1 are widespread and effects on health of high fluoride in water have been reported. The aim of the current project was to
develop a geographic information system (GIS) to aid the identification of areas where high-fluoride waters and fluorosis
may be a problem; hence, where water treatment technologies should be targeted. The development of the GIS was based upon
the collation and digitisation of existing information relevant to fluoride risk in Ukraine, Moldova, Hungary and Slovakia
assembled for the first time in a readily accessible form. In addition, geochemistry and health studies to examine in more
detail the relationships between high-fluoride drinking waters and health effects in the population were carried out in Moldova
and Ukraine demonstrating dental fluorosis prevalence rates of 60–90% in adolescents consuming water containing 2–7 mg l−1 fluoride. 相似文献
559.
Critically evaluating best management practices for preventing freshwater turtle extinctions 下载免费PDF全文
Ex situ conservation tools, such as captive breeding for reintroduction, are considered a last resort to recover threatened or endangered species, but they may also help reduce anthropogenic threats where it is difficult or impossible to address them directly. Headstarting, or captive rearing of eggs or neonate animals for subsequent release into the wild, is controversial because it treats only a symptom of a larger conservation problem; however, it may provide a mechanism to address multiple threats, particularly near population centers. We conducted a population viability analysis of Australia's most widespread freshwater turtle, Chelodina longicollis, to determine the effect of adult roadkill (death by collision with motor vehicles), which is increasing, and reduced recruitment through nest predation from introduced European red foxes (Vulpes vulpes). We also modeled management scenarios to test the effectiveness of headstarting, fox management, and measures to reduce mortality on roads. Only scenarios with headstarting from source populations eliminated all risks of extinction and allowed population growth. Small increases in adult mortality (2%) had the greatest effect on population growth and extinction risk. Where threats simultaneously affected other life‐history stages (e.g., recruitment), eliminating harvest pressures on adult females alone did not eliminate the risk of population extinction. In our models, one source population could supply enough hatchlings annually to supplement 25 other similar‐sized populations such that extinction was avoided. Based on our results, we believe headstarting should be a primary tool for managing freshwater turtles for which threats affect multiple life‐history stages. We advocate the creation of source populations for managing freshwater turtles that are greatly threatened at multiple life‐history stages, such as depredation of eggs by invasive species and adult mortality via roadkill. 相似文献
560.
Effects of land clearing techniques and tillage systems on runoff and soil erosion in a tropical rain forest in Nigeria 总被引:2,自引:0,他引:2
This work reports runoff and soil loss from each of 14 sub-watersheds in a secondary rain forest in south-western Nigeria. The impact of methods of land clearing and post-clearing management on runoff and soil erosion under the secondary forest is evaluated. These data were acquired eighteen years after the deforestation of primary vegetation during the ‘ West bank’ project of the International Institute for Tropical Agriculture (IITA). These data are presented separately for each season; however, statistical analyses for replicates were not conducted due to differences in their past management. Soil erosion was affected by land clearing and tillage methods. The maximum soil erosion was observed on sub-watersheds that were mechanically cleared with tree-pusher/root-rake attachments and tilled conventionally. A high rate of erosion was observed even when graded-channel terraces were constructed to minimize soil erosion. In general there was much less soil erosion on manually cleared than on mechanically cleared sub-watersheds (2.5 t ha−1 yr−1 versus 13.8 t ha−1 yr−1) and from the application of no-tillage methods than from conventionally plowed areas (6.5 t ha−1 yr−1 versus 12.1 t ha−1 yr−1). The data indicate that tillage methods and appropriate management of soils and crops play an important role in soil and water conservation and in decreasing the rate of decline of soil quality. 相似文献