Colloids in Lake Michigan Water: Nature, Size Distribution, Seasonal Variation and Reaction with Metals

摘要

Lake Michigan water samples were collected both at-shore near Chicago, Illinois and approximately 20 miles off-shore near Grand Haven, Michigan. Colloidal matter in all samples was concentrated by ultrafiltration and the number and size of the colloids were measured by transmission electron microscopy and evaluated chemically. Over 90% of the colloidal matter was organic. The seasonal variation in number of colloids, phytoplankton numbers, and primary productivity were similar. The maximum number, volume, and surface area of colloids appeared in September while the minimum values for these parameters appeared in January and February. The vertical distribution of colloids markedly decreased from the surface throughout the water column. The colloids were able to adsorb trace metals, especially at metal concentrations below 1 micro g/l. At 0.5 micro g/l of added cadmium or lead, approximately 24% of the cadmium was adsorbed by colloids while approximately 33% of the lead was adsorbed.