Influence of UVB radiation on the capacity of dissolved organic carbon to protect freshwater phytoplankton from metal toxicity.

Abstract

Water samples from the Raisin River, Grand River, Lake Simcoe and St. Lawrence River were irradiated in the laboratory for up to 10 d under fluorescent lamps with maximum irradiance in the ultraviolet B waveband (at 310 nm). These waters were chosen to represent a range of dissolved organic carbon (DOC - 30.3, 17.4, 4.4 and 1.9 mg C L-1, respectively). Changes in toxicity of Cu, Zn, Co, Pb, Ni and Cd to Pseudokirchneriella subcapitata in response to irradiation depended on sample source and on the metal tested. Newington Bog water (35.5mg C L-1) was irradiated for 20 d under UVB lamps in the laboratory and under natural solar radiation. Further experiments were performed using a second sample of Raisin River water (20.7 mg C L-1) exposed to 20 d artificial UVA and UVB radiation at or below the maximum irradiance of natural solar radiation. (Abstract shortened by UMI.)