A model for lead, zinc, and copper in lakes

We present a budget for lead, zinc, and copper in Lough Neagh, Northern Ireland, and use the results from this and seven other lakes in Europe and the United States to develop two simple, generic models for heavy metals in lake water. The models, based on retention coefficient and sedimentation coefficient, are assessed by comparing the modeled and measured steady-state lake concentrations. The results show that deposition from the atmosphere is an important source of contamination of the lakes by Pb (56.3 % of total inputs) and Zn (34.8%), but not Cu (8.3%). The mean retention coefficient in five of the lakes is 0.70 (RSD 5 29%), 0.72 (24%), and 0.24 (133%) for Pb, Zn, and Cu, respectively; mean total residence time is 0.21 (RSD 5 64%), 0.36 (61%), and 0.77 (97%) yr; and mean sedimentation residence time 0.34 (RSD 5 73%), 0.91 (99%), and 0.05 (95%) yr. The goodness of fit of the two models are similar, with root mean square error of prediction of 60.14, 1.9, and 1.6 mg L21 for Pb, Zn, and Cu, respectively. The magnitude of the errors in relation to the ranges of concentration suggests that the models for Pb and Zn can be used as fate models for these metals in lake water. The amount of research into the fate and effects of heavy metals at the surface of the Earth has increased over the last 5 yr. There are three reasons for this. First, the 1998 Protoco