Chemistry

Abstract

Weekly samples of precipitation and stream water are obtained from the experimental watersheds for chemical analysis. Rain and snow are sampled with continuously open plastic collectors (Likens et al., 1967). Samples of stream water are collected approximately 10 m upstream from each weir in clean polyethylene bottles. This is necessary because water collected from the ponding basin above the weir would be contaminated by calcium and bicarbonate from the cement in the weir itself. The concentrations of dissolved chemicals characterizing a period of time are reported as weighted averages. These averages are computed by summing the amount of chemical from individual samples of precipitation or stream water during the period and then dividing this value by the total amount of water during the period. Nutrient flux across ecosystem boundaries is determined (1) by multiplying the measured concentration of dissolved chemicals in the accumulated composite sample of precipitation by the amounts of precipitation during the interval and (2) by multiplying the average of measured concentrations of dissolved chemicals from stream water samples taken at the beginning and at the end of the interval by the amount of stream water during the period.