Review of highway runoff characteristics: comparative analysis and universal implications.

This review interprets highway runoff characterization studies performed on different continents. The results are synthesized to discuss the historical trends, first flush effects of pollutants, pollutant form as dissolved vs. particulate, and to identify surrogate water quality parameters. The information presented in this review showed that: (1) variability has been observed in all quality parameters from each continent and among continents; (2) with a few exceptions the variability seems to be within the expected range; (3) inconsistent monitoring data as well as inconsistent quality assurance and quality control measures were reported among studies, which may be partially responsible for variability of water quality results; (4) compared with historic data, the concentration of total Pb decreased exponentially, which can mostly be credited to leaded gasoline phase-out regulation; (5) first flush effects of pollutants based on concentration have been reported consistently (however, mass first flush effects for pollutants have been reported inconsistently compared with concentration first flush effect); (6) most metal pollutants and phosphorus are present in both the particulate and dissolved forms; and (7) strong correlations were observed between TSS, TDS, TOC and iron (Fe) and 13 other constituents and water quality parameters (turbidity, O&G, TPH, DOC, TKN, EC, Cl, Cd, Cr, Cu, Ni, Pb, Zn).