A comparison of selected chemical characteristics in runoff from different land types

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Virginia Polytechnic Institute and State University

This study was conducted in order to obtain information that would permit comparisons of six nutrient parameters, both organic and inorganic, in runoff from five different land types. Sampling and laboratory determinations were conducted on runoff samples collected during the summer of 1973, in and around the town of Blacksburg, Virginia.

The five different types of runoff that were studied were construction, residential, commercial, agricultural, and forest. The six parameters investigated during the study were five-day biochemical oxygen demand (BOD₅), chemical oxygen demand, orthophosphorous, total phosphorous, nitrate, and total organic carbon. The major interest was in BOD₅ concentrations because of the importance of land runoff in stream assimilation modeling. Analyses were also performed during low flow periods to permit a comparison with runoff collected during storm events.

Concentrations of BOD₅ in runoff from all six land types were higher than the 2 mg/l normally assumed as a value for runoff in stream assimilation models. Also, nitrogen and phosphorous concentrations in all runoff samples were high enough to constitute a significant contribution of fertilizer elements to streams. Of the types of runoff tested, commercial and construction runoff were greater sources of pollution than residential, agricultural, or forest runoff.