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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...

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Biogenic amines are interesting compounds which may be of use for medical diagnosis or therapeutic monitoring. The present paper deals with the problems that occur with concentration determination of dimethylamine (DMA) and trimethylamine (TMA). These occur in the breath of people suffering from renal disease. The measurement of amines present in trace concentrations requires the application of suitable analytical methods during sampling, storage and preconcentration. This is particularly so due to their polar and basic properties. In this paper, the application of solid phase microextraction (SPME) and thermal desorption (TD) with subsequent measurement by GC-MS for the determination of amines is discussed. For DMA, preconcentration by SPME did not give satisfactory results. TMA may be analysed using SPME preconcentration with an LOD of 1.5 ppb. Thermal desorption with Tenax as the adsorbing material allows reliable concentration determination for TMA (LOD = 0.5 ppb) and DMA (LOD = 4.6 ppb). DMA cannot be stored reliably in Tedlar bags and longer storage on Tenax (with subsequent TD) does not give good repeatability of results. For TMA, storage can be done on Tenax or in bags, the best results for the latter being achieved with Flex Foil bags.