Combined Effects of Chlorine and Ammonia on Litter Breakdown in Outdoor Experimental Streams

摘要

The response of Potamogeton crispus L. breakdown to controlled doses of different levels of chlorine and chlorine + ammonia was investigated over two years in outdoor experimental streams. In 1985, downstream riffles of 2 streams were dosed (observed in-stream concentrations) at ca. 10 micro g/L Total Residual Chlorine (TRC), one stream at 64 micro g/L TRC and one stream at 230 micro g/L TRC. Two control streams were not dosed and the upstream riffles of each stream served as within stream controls. In Aug-Sep, all three streams with chlorine + ammonia (6, 56 and 146 micro g/L TRC + 2.5 mg/L ammonia) and the 70 micro g/L TRC alone stream had significantly lower decomposition rates in the downstream dosed sites. For these streams, downstream decay rates ranged from 46% (high chlorine + ammonia) to 73% (low chlorine + ammonia) of the upstream control rates. No other up-down pairs were different during the trial. Up and downstream sites of the stream dosed with 2.5 mg/L ammonia alone were nearly identical for both trials (