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1.
— The 96 h TL50 values, the maximum acceptable toxicant concentration (MATC) and the safe concentrations were determined for various aquatic pollutants, viz. thiotox, chlordane, metasystox, dichlorvos, sevin and carbofuran (pesticides), phenol, pentachlorophenol and dinitrophenol (phenolic compounds), cadmium chloride and copper sulphate (heavy metal), swascofix P14, swanic 6 L and swascol 1P (synthetic detergent) using the larvae (the most sensitive stage of the life cycle) of Cyprinus carpio, a fresh water exotic carp. — The estimated MATC ranged between 0.009 and 400 μg/1 for all the pollutants; — the calculated value of the application factor (AF) ranged between 0.0096 and 0.0978. — The safe concentrations were determined for each pollutant by the lowest value of application factor worked out in the present investigation; — safe concentrations were also worked out by different formulae given by different workers. The values obtained were compared with the safe concentrations value worked out by the authors of the present study. 相似文献
2.
In most groundwater applications, measurements of concentration are limited in number and sparsely distributed within the domain of interest. Therefore, interpolation techniques are needed to obtain most likely values of concentration at locations where no measurements are available. For further processing, for example, in environmental risk analysis, interpolated values should be given with uncertainty bounds, so that a geostatistical framework is preferable. Linear interpolation of steady-state concentration measurements is problematic because the dependence of concentration on the primary uncertain material property, the hydraulic conductivity field, is highly nonlinear, suggesting that the statistical interrelationship between concentration values at different points is also nonlinear. We suggest interpolating steady-state concentration measurements by conditioning an ensemble of the underlying log-conductivity field on the available hydrological data in a conditional Monte Carlo approach. Flow and transport simulations for each conditional conductivity field must meet the measurements within their given uncertainty. The ensemble of transport simulations based on the conditional log-conductivity fields yields conditional statistical distributions of concentration at points between observation points. This method implicitly meets physical bounds of concentration values and non-Gaussianity of their statistical distributions and obeys the nonlinearity of the underlying processes. We validate our method by artificial test cases and compare the results to kriging estimates assuming different conditional statistical distributions of concentration. Assuming a beta distribution in kriging leads to estimates of concentration with zero probability of concentrations below zero or above the maximal possible value; however, the concentrations are not forced to meet the advection-dispersion equation. 相似文献
3.
Michael C. Sukop 《Ground water》2000,38(6):836-841
4.
No baseline existed for the radionuclides in Kuwait territorial water. With changing trend in the region to embrace nuclear energy, the baseline study is imperative to create a reference and to record the influence-functioning of upcoming power plants. The first one in Bushehr, Iran is ready to start and several more are likely to come-up in UAE, Saudi Arabia and Kuwait. The present baseline concentration of the four considered radionuclide's show low concentration of tritium, polonium, strontium and cesium; their concentration is comparable to most oceanic waters. 相似文献
5.
J. F. Macqueen 《Advances in water resources》1980,3(4):165-172
The cooling water discharged from a power station may contain dissolved material, in addition to the heat rejected from the station turbines, which must be dispersed away from the power station in a manner which is environmentally acceptable. Mathematical methods are presented for use in the calculation of the rises in background concentration arising from the discharge of such material into lakes, rivers, estuaries or the sea. The calculations take account of factors including the replacement of the receiving water by freshwater, the available volume of water in the system, the rate at which the material may be degraded in the receiving water and some aspects of the design of the cooling water system. Particular calculations emphasize the different levels of concentration which may be expected from similar discharges into the different types of receiving water body. These examples suggest that for conditions representative of some present power station sites the concentration in a lake may be ten times that in an estuary, and that in an estuary may be ten times that in the sea. Of course, this is not a general result and the concentration level must be calculated for each particular case. The analyses also suggest what hydrographic factors must be measured during field surveys at a particular site if the mathematical methods presented here are to be used for the calculation of concentrations of any discharged material. 相似文献
6.
Fog (haze) droplet concentrations and size distributions were measured at five sampling sites representing rural and urban regions and a highly polluted marine-urban environment. Droplet imprints in a thin gelatine layer were evaluated and compared to the measurement by light scattering instruments. This enabled conditions for the application of the logarithmic-normal size distribution and for the classification of typical fog droplet size distributions to be established. In particular, the parameters featuring the width and asymmetry of a size distribution were suggested and calculated. Advantages and drawbacks of the applied droplet sampling and evaluation technique are discussed in more detail. 相似文献
7.
— Atmospheric particulate concentration for total suspended particles (TSP) and for PM10 (particulate matter under 10 micron) was measured in Jalan Braga and ITB campus, Bandung. Six samples were collected over one- or two-day time periods using High Volume Sampler (HVS) for TSP and Low Volume Sampler (LVS) or Anderson Cascade Impactor for PM10. Samples were further analyzed to determine concentrations of metals, sulfate and nitrate. Concentration of NOx (NO and NO2) was also measured hourly and simultaneously during the sampling period. The results from this study show that the atmospheric particulate concentration in Jalan Braga for TSP ranged from 304.04 to 363.17, and for PM10 concentration ranged from 277.02 to 336.44 μg/m3. The lead concentrations were 1.42–2.37 μg/m3 in the TSP and 0.81–1.57 μg/m3 in the PM10. The nitrate concentrations were 5.89–6.51 μg/m3 and 2.27–3.45 μg/m3 for the TSP and PM10, respectively. The hourly NOx concentration varied between 0.14–0.35 ppm. The total elements (metals, sulfate and nitrate) found in the samples contribute from 20 to 25% of the total particulate concentration. 相似文献
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Naoji Sugiura 《Earth and Planetary Science Letters》1979,42(3):451-455
ARM (anhysteretic remanence)/SIRM (saturation isothermal remanence) and TRM (thermoremanence)/SIRM were measured as a function of the concentration (volume fraction) of single-domain magnetite (3 × 10?6 ? C ? 2 × 10?2), ARM/SIRM increases with decreasing concentration, showing that there is magnetic interaction between fine particles. The role of magnetic interaction in TRM acquisition is also important at higher concentrations of magnetite (C ? 0.1%), where the value of TRM/SIRM increases with decreasing concentration. It is only for concentrations ofC ? 0.1% that the value of TRM/SIRM is fairly constant and interactions among magnetite grains seem to be ignored. The ratio TRM/ARM decreases from seven to almost unity as the concentration of magnetite decreases. 相似文献
11.
Radon-222 Concentration and Aquifer Lithology in North Carolina 总被引：1，自引：0，他引：1
Dana P. Loomis 《Ground Water Monitoring & Remediation》1987,7(2):33-39
The presence of the radioactive gas radon (Rn-222) in many ground water supplies is a potentially significant source of public exposure to ionizing radiation. A wide range of radon concentrations has been measured in ground water in North Carolina, including some far in excess of national average concentrations. North Carolina is, however, geologically complex and ground water radon concentrations vary considerably among the state's aquifers. The highest average radon concentrations occur in areas underlain by granites (geometric mean 5910 pCi/l), and the lowest occur in the Atlantic Coastal Plain region (48 pCi/l). Average radon levels intermediate between these extremes are characteristic of the large areas of North Carolina underlain by gneisses, schists and metavolcanic rocks. Relative average radon concentrations in ground water from the rock types surveyed are consistent with relative abundances of uranium, the parent element of radon, in these rocks. Although other geologic and hydrologic factors also have an effect, aquifer lithology is a useful predictor of the concentration of radon in ground water. The occurrence of high radon concentrations in certain aquifer types; such as granites, shows that geologic factors should be considered in estimates of population exposure to radon, and that knowledge of aquifer geology can help to predict ground water radon concentrations in areas where field sampling has not been done. 相似文献
12.
James M. Martin-Hayden 《Ground water》2000,38(1):121-128
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The degradation behaviour of a phenolic waste-water from coking containing easily utilizable carbon sources (volatile fatty acids), substances with toxic effects (phenols and phenolic compounds), and non-biodegradable organic substances (humic-like substances) by an adapted activated sludge is investigated depending on dissolved oxygen concentration (DO) and temperature. In addition, the degradation of an acetate model water with the same population was investigated. The investigations were carried out in a special respiration fermenter system by recording oxygen consumption in DO-static experiments. The oxygen consumption curves were subjected to linear regression analysis, and the maximum oxygen consumption rates were used for further calculations. Evaluation of the degradation kinetics was carried out with non-linear regression analysis via commercial software utilizing the Marquardt-Levenberg algorithm and which tested various kinetic models to obtain the best curve fit. It is shown that the dependence of growth on DO in acetate model water is well represented by Monod kinetics but by contrast can only be described in phenolic wastewater with acceptable goodness by Hill kinetics, modified by a maintenance term. The kinetic constants calculated for the mesophilic range (37 °C) are for the model water as follows: maximum specific growth rate = 0.218 h?1, half saturation constant with respect to oxygen = 0.297 g L?1, and for the waste-water: maximum specific growth rate = 0.387 h?1, half saturation constant with respect to oxygen = 0.013 gL?1 and maintenance coefficient for oxygen = 0.107 g g?1 h?1. For the thermophilic range (55 °C), a higher growth rate but a significant lower yield coefficient are to be observed. The kinetic constants calculated are: maximum specific growth rate = 0.8 h?1, half saturation constant with respect to oxygen = 0.14 gL?1 and maintenance coefficient for oxygen = 0.3 g g?1 h?1. Therefore, it can be concluded that the toxic effect of the biodegradable phenols causes a maintenance metabolism which leads to higher oxygen demand. The diminution of the limiting DO and the increased maintenance metabolism confirm the assumption that a higher maintenance metabolism leads to increased sensitivity with respect to the cosubstrate oxygen. It can be concluded that the experimental and mathematical methods used permit the maintenance metabolism with respect to oxygen caused by toxic substrates and milieu influences to be accurately determined. 相似文献
15.
Purge and pump samples from screened wells reflect concentration averaging and contaminant redistribution by wellbore flow. These issues were assessed in a screened well at the Hanford Site by investigating the vertical profile of a technetium-99 plume in a conventional well under static and pumped conditions. Specific conductance and technetium-99 concentrations were well correlated, and this enabled measurement of specific conductance to be used as a surrogate for technetium-99 concentration. Time-series measurements were collected during purging from three specific conductance probes installed in the well at 1.2, 3.1, and 4.9 m below the static water level in a 7.7-m-deep screened well. The vertical contaminant profile adjacent to the well in the aquifer was calculated using the concentration profile in the well during pumping, the pumping flow rate, and a wellbore flow and mixing model. The plume was found to be stratified in the aquifer—the highest concentrations occurred adjacent to the upper part of the screened interval. The purge and pump sample concentrations were 41% to 58% of the calculated peak concentration in the aquifer. Plume stratification in the aquifer adjacent to the well screen became more pronounced as pumping continued. Extended pumping may have partially reversed the effect of contaminant redistribution in the aquifer by wellbore flow and allowed the stratification of the plume to be more observable. It was also found that the vertical profile of contamination in the well under static (i.e., nonpumping conditions) was not representative of the profile in the aquifer. Thus, passive or micropurge sampling techniques, which sample the wellbore water at different depths, would not yield results representative of the aquifer in this well. 相似文献
16.
A two-dimensional, transient-flow, and transport numerical model was developed to simulate in situ chemical oxidation (ISCO) of trichloroethylene and tetrachloroethylene by potassium permanganate in fractured clay. This computer model incorporates dense, nonaqueous phase liquid dissolution, reactive aquifer material, multispecies matrix diffusion, and kinetic formulations for the oxidation reactions. A sensitivity analysis for two types of parameters, hydrogeological and engineering, including matrix porosity, matrix organic carbon, fracture aperture, potassium permanganate dosage, and hydraulic gradient, was conducted. Remediation metrics investigated were the relative rebound concentrations arising from back diffusion and percent mass destroyed. No well-defined correlation was found between the magnitude of rebound concentrations during postremedy monitoring and the amount of contaminant mass destroyed during the application. Results indicate that all investigated parameters affect ISCO remediation in some form. Results indicate that when advective transport through the fracture is dominant relative to diffusive transport into the clay matrix (large System Peclet Number), permanganate is more likely to be flushed out of the system and treatment is not optimal. If the System Peclet Number is too small, indicating that diffusion into the matrix is dominant relative to advection through the fracture, permanganate does not traverse the entire fracture, leading to postremediation concentration rebound. Optimal application of ISCO requires balancing advective transport through the fracture with diffusive transport into the clay matrix. 相似文献
17.
J.D. MacDougall 《Earth and Planetary Science Letters》1977,35(1):65-70
The uranium content of glass from chilled margins of oceanic tholeiitic basalt flows is generally ≤0.1ppm, even for old samples with highly altered crystalline interiors. Such low values represent the original whole rock concentrations, although subsequent to eruption low-temperature weathering has added uranium, and other elements, to the crystalline portions of these basalts. Consideration of the K/U ratios of altered samples suggests that basalt weathering may provide the major oceanic sink for these two elements. 相似文献
18.
Michael Schöppner Martin Kalinowski Wolfango Plastino Antonio Budano Mario de Vincenzi Anders Ringbom Federico Ruggieri Clemens Schlosser 《Pure and Applied Geophysics》2014,171(3-5):699-705
The general characterisation of the global radioxenon background is of interest for the verification of the Comprehensive Nuclear-Test-Ban Treaty. Since the major background sources are only a few isotope production facilities, their source term has an emphasized influence on the worldwide monitoring process of radioxenon. In this work, two different datasets of source terms are applied through atmospheric transport modelling, to estimate the concentration at two radioxenon detection stations in Germany and Sweden. One dataset relies on estimated average annual emissions; the other includes monthly resolved measurements from an isotope production facility in Fleurus, Belgium. The quality of the estimations is then validated by comparing them to the radioxenon concentrations that have been sampled at two monitoring stations over the course of 1 year. 相似文献
19.
《Acta Geochimica》2021,(4)
While engineered nanoparticles are widely used and maybe eventually released into the environment,natural nanoparticles are also commonly found in the Earth system.Nanoparticles may critically affect the geochemical migration of associated elements and pose potential threats to the ecological environment.It is necessary to establish an accurate and reliable method for measuring the concentration of nanoparticles.AAS is one of the most commonly used methods for the concentration determination of nanoparticles.However,till now,there has been no systematic report on how experimental variables affect AAS measurements.In this study,we used gold nanoparticles(AuNPs) as an example and studied the influences of a list of factors on the concentration determination of AuNPs by AAS,including digestion method,ionization interference,acidic medium,background correction method,and organic matter.We demonstrate that all these factors may have varying degrees of influence on the measured gold concentrations.When the gold colloid is digested at room temperature for more than 8 h or at 60℃ for more than 2 h,and the system contains a low concentration of organic matter,AAS can accurately measure the AuNP concentration at ppm-level.The deuterium lamp background deduction method is not recommended to use for samples with lower gold concentrations. 相似文献