Pollutant Washoff Characterization of Expressway Runoff in Shanghai.

Pollutant washoff loads from an expressway in Shanghai, China were investigated during a 1-year study program. The median washoff load during an rainfall event for total solids, chemical oxygen demand, total nitrogen and total phosphorus were 4,389.8, 2,123.0, 47.6 and 1.6 mg/m², respectively. Through principal factor analysis, three factors that represent the influence of pollutant source availability, rainfall volume and rainfall intensity account for 89% variance of the monitoring data. The result of multiple regression analysis reveals that antecedent dry period significantly influences the washoff load, while peak rainfall intensity and runoff volume may have some influence, which correlates well with the principal factor analysis results. [ABSTRACT FROM AUTHOR]