Abstract:A comprehensive study of a sandy aquifer of deltaic origin in southern Poland included water chemistry, isotopes, dissolved trace gases and transport modelling. Tritium, sulphur hexafluoride (SF 6 ) and freons (F-11, F-12 and F-113) showed the presence of modern waters in the recharge areas and shallow confined parts of the aquifer. The presence of older Holocene waters farther from the recharge areas was indicated by lack of 3 H, SF 6 contents Ä0Ð02 fmol l 1 and relatively low 14 C values. The discharge from the system is by upward seepage in the valley of a major river. Pre-Holocene waters of a cooler climate, identified on the basis of υ 18 O, υ 2 H, 14 C, Ne and Ar data, were found in some distant wells. Concentrations of N 2 , Ne and Ar determined by gas chromatography were used for calculating the noble gas temperatures, air excess needed for correction of SF 6 , and nitrogen content released by denitrification process. The time series of 3 H content available for some wells supplied quantitative information on age distributions and the total mean ages of flow through the unsaturated and saturated zones. The derived 3 H age distributions turned out to be very wide, with mean values in the range of about 30 to 160 years. For each well with determined 3 H age, the SF 6 data showed either a lower age range or the possibility of a lower age as expected due to shorter travel times of SF 6 through the unsaturated zone, which most probably also resulted in different types of age distributions of these tracers. Freons appeared to be of little use for individual age determinations. A quantitative estimation of two-component mixing from SF 6 -3 H relations is not possible unless the travel time of 3 H through the unsaturated zone is comparable to that of SF 6 . The ratio of integrals of the response function over the age range with tracer and the whole response function yields the ratio of water with tracer to total flow of water. That ratio is a tracer-dependent function of time. Transport modelling of SF 6 tracer done with MT3D code yielded initially large discrepancies between calculated and measured tracer concentrations. Some discrepancies remained even after calibration of the transport model with SF 6 . Simulation of tritium contents with a calibrated transport model yielded reasonable agreement with measured contents in some wells and indicated a need for further investigations, particularly in the eastern part of the aquifer. The existence of distinct hydrochemical zones is consistent with the tracer data; young waters with measurable 3 H and SF 6 contents are aerobic and of HCO 3 -Ca or HCO 3 -SO 4 -Ca types. Slightly elevated Na and Cl contents, as well as the highest concentrations of SO 4 and NO 3 within this zone are due to anthropogenic influences. Anaerobic conditions prevail in the far field, under the confining cover, where pre-bomb era Holocene waters dominate. In that zone, dissolved oxygen, NO 3 and U contents are reduced, and Fe, Mn and NH 4 contents increase. In the third zone, earl...
Abstract. This paper undertakes the description and assessment of various solutions applied for the design of photobioreactors as the type of apparatus, which can provide high output of green algae biomass. The design of such apparatus plays an important role in the context of the concurrent fulfillment of ecological and economic requirements, which are necessary to conduct an efficient and effective technology using cheap and easily accessible resources to produce different goods. Nowadays, algae is seen as one of the most promising sustainable way to produce energy in the future (biofuels, electricity, thermal energy) but technologies of biomass production and processing are still under development particularly to increase biomass and energy output. The cultivation costs in closed systems are still high, limiting their commercial applications to high-valued compounds but they can be reduced by efficient bioreactor designs, which are able to achieve high areal biomass productivities. This paper focuses on the advantages and drawbacks associated with the application of the particular types of bioreactors in algae production, description of their operation parameters and area for practical application, pointing of the constructions (tubular, flat panel, bubble column) that can contribute to improvement the profitability of large-scale production.
consumption and groundwater-dependent ecosystems as two receptors with respect to which groundwater should be protected from deterioration and chemical pollution. From this perspective it is even more appropriate to assess groundwater vulnerability not for the whole groundwater body but for particular receptors like abstraction wells or groundwater-dependent ecosystems.A fundamental difficulty in assessing groundwater vulnerability is the complexity of groundwater systems. The intertwined processes of groundwater flow and pollutant transport occur in three spatial dimensions, in the inherently heterogeneous and anisotropic geological media, over a great range of distances and times, and are typically nonstationary. Also, the pressures on groundwater quality have complex or unknown spatial and temporal distribution characteristics. The vulnerability of a particular groundwater receptor is therefore a complex function of the following:spatial and temporal distribution of pressures, for example, location of source areas of pollution, pollutant loads, fertilization levels, location of pumping wells and their pumping regimes, patterns of land-use change; distribution of water flow paths in the groundwater body; dilution, retardation, attenuation, and transformations of contaminants in the subsurface that affect their levels at the receptor; rates at which impacts of pressures propagate along the flow paths, that is, time lags associated with the responses of the receptor to the commencement or cessation of pressures. The task of assessing groundwater vulnerability can thus be seen as essentially equivalent to predicting contaminant concentrations within the groundwater body or at the groundwater receptors. A direct and comprehensive assessment of groundwater vulnerability is in most cases not feasible due to insufficient availability of monitoring data and the inherent complexity of groundwater systems. Instead, groundwater vulnerability indicators are defined, quantified, and mapped in order to reflect the actual or to predict the potential severity of human-induced deterioration in groundwater quality. Furthermore, because of time lags inherent to the groundwater flow and contaminant transport, responses in groundwater quality to changes in contaminant inputs may not be visible over short periods of time of the order of years that are typically considered by policy makers, ground-water managers, and the general public. Setting up of deadlines for the improve-ment of surface water quality-as, for example, in programs of measures required by the Water Framework Directive-involves consideration of such time lags (Witczak et al., 2007;Fenton et al., 2011;Aquilina et al., 2012;Hamilton, 2012; Herrman et al., 2012; Stumpp et al., not published yet).This work presents different understandings of the groundwater vulnerability concept and gives an overview of methods for assessing the intrinsic vulnerability. Among those, only the physically based methods can provide physically meaningful and operational indicators of the i...
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