A novel method has been developed for determining the natural decay series radionuclides (NDS), 210Pb, 210Bi, and 210Po, in seawater by way of state-of-the-art liquid scintillation spectrometry. For 210Pb analysis, the method makes use of a 212Pb yield tracer, prepared by ion exchange separation from aged Th(NO3)4. 210Bi recovery is determined using 207Bi as the yield tracer, and 210Po is determined using the conventional 208Po yield tracer. The limits of detection for this method are 0.32, 0.34, and 0.004 mBq 1-1 for 210Pb, 210Bi, and 210Po, respectively. The analysis can be completed within 10 days, as compared with up to one year for traditional methods. Results are presented for a preliminary study of 210Pb, 210Bi, and 210Po in the dissolved and particle-bound phases of Irish Sea water.

and hydrological events. In the Lambourn, the radon budget is controlled by diffuse 10 groundwater inputs, supporting the hypothesis that the alluvial aquifer plays a greater 11 role during periods of high accretion. The Pang is more complex than the Lambourn 12 having a combination of diffuse and point source inputs, with spring inputs dominating 13 both flow and radon signatures in the lower part of the catchment. Significant temporal 14 and spatial variations were determined for C I in both catchments reflecting their 15 differing geologies and flow regimes. One use of radon in hydrology is the 16 determination of groundwater discharges to rivers, but the observed variations in C I 17 mean this approach may not be appropriate to all situations and that changes in source 18 need further evaluation. Nonetheless, radon is shown to be a useful tracer of flow paths 19 and processes within these catchments. 20 21

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Radon is a powerful tracer of stream-aquifer interactions. However, it is important to consider the source and behaviour of radon in groundwater when interpreting observations of river radon in relation to groundwater discharge. Here we characterise the variability in groundwater radon concentrations in the riparian zone of a Chalk catchment. Groundwater 222 Rn (radon) concentrations were determined in riparian zone boreholes at two sites in the Lambourn catchment, Berkshire, UK, over a two year period. In addition, borehole core material was analysed for 226 Ra (radium) and to determine radon emanation. Radon and radium concentrations and radon emanation were found to change with depth and temporal variations in groundwater radon concentrations were found at different scales. The abundance of radium and emanation of radon increased nearer the surface leading to greater groundwater radon concentrations. It is shown that seasonal changes in water table elevation can to lead to variable radon concentrations in groundwater as zones of radon production become hydraulically active. Groundwater radon concentrations in shallow piezometers were found to respond to both seasonal changes in the water table and individual rainfall events. Riparian sources of radon can be variable and are therefore potentially influential in the radon signals observed in rivers and should be properly characterised when interpreting river radon inputs.