Critical Limits for Hg(II) in soils, derived from chronic toxicity data.
Published chronic toxicity data for Hg(II) added to soils were assembled and evaluated to produce a data set comprising 52 chronic end-points, five each for plants and invertebrates and 42 for microbes. With end-points expressed in terms of added soil Hg(II) contents, Critical Limits were derived from the 5th percentiles of species sensitivity distributions, values of 0.13 microg(g soil)(-1) and 3.3 microg(g soil organic matter)(-1) being obtained. The latter value exceeds the currently recommended Critical Limit, used to determine Hg(II) Critical Loads in Europe, of 0.5 microg(g soil organic matter)(-1). We also applied the WHAM/Model VI chemical speciation model to estimate concentrations of Hg(2+) in soil solution, and derived an approximate Critical Limit Function (CLF) that includes pH; log [Hg(2+)](crit)=-2.15 pH -17.10. Because they take soil properties into account, the soil organic matter-based limit and the CLF provide the best assessment of toxic threat for different soils. For differing representative soils, each predicts a range of up to 100-fold in the dry weight-based content of mercury that corresponds to the Critical Limit.
Tipping
E
E
Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LA1 4AP, United Kingdom. et@ceh.ac.uk
Lofts
S
S
Hooper
H
H
Frey
B
B
Spurgeon
D
D
Svendsen
C
C
D000818:Animals; D004784:Environmental Monitoring; D008628:Mercury / Q000032:analysis*; D012987:Soil / Q000032:analysis*
D012987:Soil; D008628:Mercury