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Environmental fate & pathways

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An overview of background and ambient selenium concentrations in the environment was made based on monitoring data in order to determine the typical background and reasonable worst case ambient concentration of selenium in water, sediment, soil and air for the EU-27 and Norway (see attached report for details). Only data from high quality international monitoring programs (FOREGS Geochemical Baseline Mapping Program and GEMAS, EuroGeoSurveys geochemical mapping of agricultural and grazing soils) were included and no specific search for Se monitoring data in from other datasets was carried out.

The natural background concentration is the natural concentration of an element in the environment that reflects the situation before any human activity disturbed the natural equilibrium (e.g., the situation a few thousands year ago). Because of historical and current anthropogenic input from diffuse sources, the direct measurement of natural background concentrations is not feasible in the European environment. As an alternative, baseline background concentration are measured. This is the concentration of an element in the present or past corresponding to very low anthropogenic pressure (i.e., close to the natural background). Ambient concentrations are defined as the sum of the natural background of an element with diffuse anthropogenic input in the past or present (i.e., influence of point sources not included). Reasonable worst-case (RWC) ambient concentration levels are used for the regional risk assessment (regional PEC).

 Compartment Unit  Typical median baseline background concentration  Reasonable worst case ambient concentration
Fresh surface water  µg Se/L 0.32 0.85a
Marine water µg Se/L 0.085 no data
Freshwater sediment mg Se/kg dw 0.1b 0.27b
Agricultural soil (0 -20 cm) mg Se/kg dw  no data 0.59
Grazing land (0 -10 cm) mg Se/kg dw  no data  0.71
 Air  ng Se/m3  no data  no data

a based on 90th percentile of baseline selenium concentrations in surface water

b based on the data for surface water and the equilibrium partitioning approach