Abstract
Urban storm runoff is a major source of pollutants in receiving water bodies. To assess the impact of urban stormwater runoff on an urban river, the runoff process of total suspended solids (TSS), chemical oxygen demand (COD), ammonium (NH4), and total phosphorus (TP) were investigated on road surfaces classified as arterial road (AR), residential area (RA), and industrial area (IA) in the Pingshan River (PSR) watershed in Shenzhen, China. Event mean concentration (EMC) was calculated to analyze the water quality of road runoff, and the dimensionless M(V) cumulative curves were used to estimate the course of decreasing concentration of runoff pollutants during each rainfall event. Multicriteria decision making methods (PROMETHEE-GAIA) were used to identify the linkage between runoff pollutants, land use types, and rainfall intensity. The EMCs of COD and TP in runoff exceeded the class IV level of the water quality standard for surface water (China). RA was a major potential source for NH4, COD, and TP in the river. Controlling the first flush is critical to decrease the effect of road runoff on receiving water bodies, as most runoff pollutants in AR, RA, and IA had a first flush effect during heavy rainfall. The specific management measure for runoff pollution varied with land use type. Reducing road TSS concentrations was effective for controlling runoff pollution in AR and RA because NH4, TP, and COD attached to particulate matter. In IA, the collection and reuse of stormwater in the initial rainfall period were effective for reducing the effect of soluble pollutants in runoff on receiving water bodies. This study provides new information for managing urban road stormwater runoff in different land use types.
Highlights
We examined the variations in runoff pollutants and the related influencing factors in Pingshan
The result showed that the concentrations of pollutants (DOC, total phosphorus (TP), and NH4 ) were high in urban road runoff especially in residential area, and rainfall intensity was the important factor affecting wash-off of these pollutants
Controlling the first flush is a critical measure to reduce the effect of runoff pollution on Pingshan River (PSR) during heavy rainfall because most pollutants showed a strong first flush phenomenon in arterial road, industrial area, and residential area during high intensity rainfall events
Summary
The increasing impervious surface cover (ISC) accompanying urbanization has led to change in watershed hydrology [1,2,3] and to the increase of stormwater runoff and reduction of evapotranspiration and infiltration [4,5], which cause large urban road runoff to flow into rivers during rainfall events [1].Increased ISC has been shown to be closely related to the increased concentrations of urban stream-water nitrogen (N), phosphorus (P), and dissolved oxygen carbon (DOC) because most of these pollutantsWater 2019, 11, 2545; doi:10.3390/w11122545 www.mdpi.com/journal/waterWater 2019, 11, 2545 can be directly transported into urban rivers with surface runoff [1,2,3,6,7]. Surface runoff is one of the major factors influencing water quality in urban rivers [3]. N, P, DOC, and heavy metals have been identified as the major pollutants in urban surface runoff [3,6,8,9,10,11,12]. Some studies have indicated that urban stormwater runoff pollutant loads for TSS, chemical oxygen demand (COD), N, and P usually exceeded the Class V level of the water quality standard for surface water in China (WQS, GB3838-2002) [13]. The highest TSS and heavy metal concentrations at the surface usually appear in AR because of the high traffic volume [15,18,19,20,21]
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