Dissolved beryllium in rainfall, stream and shallow groundwaters in the Upper River Severn catchments, Plynlimon, mid Wales.

This paper examines the temporal changes in dissolved beryllium in deposition (rainfall and cloud water), stream water and groundwater for the upper River Severn catchments at Plynlimon in mid-Wales. There are two main themes to the study. Firstly, time series records are examined to see if anomalous behaviour occurred during 1996, when remarkably high concentrations were unexpectedly observed in the UK lowland rivers (Neal, Sci Total Environ, 2003). The results show (a) Beryllium concentrations in rainfall and stream water remained low throughout the period (mean 0.02 and 0.07 microg l(-1) in rainfall and stream water, respectively) and were often less than the lowest quotable value for a single determination (0.05 microg l(-1)). (b) Beryllium concentrations in the streams declined between 1983 and 1996 from a mean of approximately 0.07 to a mean of 0.04 microg l(-1). This was followed by a brief increase in the autumn of 1995 (up to values of approx. 0.2 microg l(-1) and a more sustained increase to approximately 0.12 microg l(-1) from 1997 to the end of monitoring late in 1998. (c) Rainfall concentrations of Beryllium were indistinguishable from zero throughout most of the monitoring period although concentrations increased late in the study in line with patterns observed in the stream when concentrations averaged approximately 0.08 microg l(-1). (d) Beryllium concentrations are much lower than observed in the UK lowlands where concentrations as high as 29 microg l(-1) were recorded. For the exceptionally high values occurring in the lowlands, there was the potential for environmental damage to aquatic organisms such as fish at levels greater than approximately 1 microg l(-1). There are no potential problems for the upper River Severn. Secondly, while Neal et al., [J Hydrol, 136 (1992) 33-49] provided information on the hydrogeochemistry of beryllium in the upper River Severn using available information at that time (rainfall, cloud water, stemflow, throughfall and stream water), there was no information available on groundwater chemistry. Since the publication of Neal et al. [J Hydrol, 136 (1992) 33-49], such information is now available and this paper makes up this shortfall. The results show that beryllium concentrations in groundwater are typically approximately 2-3 times higher than those found within the streams (mean 0.14 microg l(-1), range 0.06-1.56 microg l(-1)). This feature probably reflects the increased leaching of beryllium from the bedrock. The findings presented in this study combined with the earlier information of Neal et al. [J Hydrol, 136 (1992) 33-49] are used to provide an overview on dissolved beryllium for the upper River Severn, the most complete and extensive record for the UK.