The use of measured boron concentration data from the GREAT-ER UK validation study (1996-1998) to generate predicted regional boron concentrations

The concentrations of boron in the Aire and Calder which have been measured in order to validate the GREAT-ER model have been used to derive a predict ed environmental concentration (PEC) for boron in the Aire catchment in Yor kshire. The data have been obtained from 33 sites, with monthly sampling ov er a 2-year period. The 90th percentile of the means of measured concentrat ions (242 mu g l(-1)) is higher than the 90th percentile predicted by the G REAT-ER model (186 mu g l(-1)), if river stretches are normalised by their flow volumes, and unpolluted headwaters are included in the catchment avera ging procedure. However, if the river stretches are normalised by the lengt h of the respective stretch, and unpolluted headwaters are included, a lowe r regional PEC of 28 mu g l(-1) is obtained. If normalisation by stretch le ngth is appropriate for regional risk assessment, then the 90th percentile of the means of the measured data will overpredict the regional boron conce ntration in a catchment such as the Aire, with a low natural level of boron in the headwaters. Monitoring data for boron in the effluents from sewage treatment works in the Aire catchment, and for boron in the Went and Rother catchments, with a higher background boron level, are also given. (C) 2000 Elsevier Science B.V. All rights reserved.