Risk assessment of runoff sediments in an experimental catchment in Bogotá related to hydrological and granulometric characteristics

Introduction. Urban runoff sediments contain heavy metals that generate risk to the environment. Several risk assessment indexes for heavy metals have been developed, which show the level of contamination of particles in the environment and their origin. Besides, sediment risk is also associated with the particle size distribution and hydrometeorological characteristics. Objective. This work seeks to evaluate the risk of contamination from runoff sediments collected in an experimental catchment, related to their size distribution and hydrological characteristics of the area of influence. Materials and methods. The field and laboratory experiments were carried out on the constructed-wetland/ storage-tank structure from Pontificia Universidad Javeriana, Bogotá. The hydrological data were obtained from a nearby El Paraíso rain gauge station. The geoaccumulation (Igeo), pollution index (PI), and enrichment factor (EF) rates were calculated. Furthermore, Principal Component Analysis was used in order to determine the relationships between the risk, hydrological and granulometric variables. Results. There is a low/medium risk for Cu and Cr, in contrast to the high risk for Pb and Zn. According to multivariate statistical analysis, there is a relationship between risk indexes and average particle diameters (D50): These indexes increase for fine particles and periods of high rainfall intensity. Conclusions. The hydrological variables are important to determine the risks of urban runoff sediments. In this study, we found that the variable of dry weather is related to the values of geo-accumulation indexes and contamination. The findings of this work reinforce the possibility of developing early warning systems for sediment risks using key hydrological and sedimentological variables.