DEPOSITION OF NUTRIENTS AND MAJOR IONS BY PRECIPITATION IN SOUTH-CENTRAL ONTARIO

As part of a study of the substance budgets of lakes in south-central Ontario, a network of precipitation collectors (8 bulk, 7 wet only) was operated to measure the deposition of nutrients and major ions. Results are reported for total P, total Kjeldahl N, NO3--N, NH4+-N, total N, Fe, H+, Ca++, Mg++, Na+, K+, SO4= and CL- for a two year period (August 1976-July 1978). On an equivalent basis the dominant anion in both bulk and wet precipitation was SO4=, with H+ the dominant cation. Precipitation in the study area is more acidic than that analyzed at any other location on the Canadian Shield to date. Concentrations of ions varied by 1 to 3 orders of magnitude between individual precipitation events and annual deposition varied by as much as 2-fold in the two years of study. Annual wet deposition contributed >60% of bulk deposition for all substances except total P. Seasonal trends in deposition with summer maxima were noted for most ions. For Harp Lake, a small Precambrian Lake with a lake area of 12.6% of its total drainage area, precipitation input directly to the lake surface was an important source of nutrients and major ions. This was especially the case for P, N and H+ because these substances were retained by the terrestrial drainage basin. © 1979 D. Reidel Publishing Co.