Characterization and Modeling of Pesticide Transport in Urbanized Areas
25 oktober 2017
VUB, Campus Etterbeek, Promotiezaal D2.01 - Pleinlaan 2 - 1050 Brussel
P. Seuntjens, A. van Griensven, J. Bronders
Doctoraatsverdediging dubbeldoctoraat Ting TANG - Faculteit Wetenschappen, Departement Bio-ingenieurswetenschappen
Population growth and urbanization lead to substantial land conversion to urban areas and increase of (semi-)impervious hard surfaces. Such hard surfaces alter the natural hydrological cycle and result in faster transport of larger amounts of water and pollutants (including pesticides) to surface water than pervious surfaces, such as soil. Despite that pesticides are mostly used in agricultural areas, pesticides are also often used in urban areas on lawns, gardens, roadsides, driveways, building foundations, facades and roofs for weed removal, pest control and structural maintenance. Consequently, pesticides and their metabolites are frequently found at potentially risk-relevant levels in urban water systems, such as drainage systems, wastewater treatment plant effluent, rivers and drinking water. Compared to agricultural pesticides, urban pesticide uses and transport behavior have rarely been studied and are poorly understood. Because of this, few pesticide models realistically consider urban use, transformation and transport of pesticides to urban water. The limited understanding and lack of models are particularly true for pesticide behavior on artificial (semi-)impervious hard surfaces, such as concrete and asphalt.
This thesis aims to develop an urban pesticide runoff model that accounts for the spatial heterogeneity of urban areas and pesticide behaviors on urban (semi-)impervious surfaces. Pesticide monitoring dataset from field and experimental studies were used to characterize pesticide behaviors in urban environments, particularly on hard surfaces. A conceptual framework was thereafter developed with six mathematical representations (model structures) to describe pesticide wash-off behaviors on (semi-)impervious hard surfaces, accounting for the physico-chemical interactions between the pesticide and the hard surface. Based on the characterization and the hard-surface conceptual framework, an urban pesticide runoff model was developed to simulate pesticide transport in urban environments, namely WetSpa-PST (Water and Energy Transfer between Soil, Plants and Atmosphere model for PeSTicides). WetSpa-PST is the first catchment-scale spatially-distributed model that accounts for the physico-chemical interactions between pesticide and urban hard surfaces. The strongest feature of WetSpa-PST is its flexibility, including easy coupling with additional processes or other models, flexible spatio-temporal resolution and mathematical representation for pesticide processes of interest. The developed model helps to improve quantitative understanding of the runoff and environmental occurrence of urban pesticides and to define appropriate pesticide management practices in urban areas.
This work advances our knowledge on urban pesticide behaviors and the underlying influencing factors. The hard-surface wash-off modeling framework and WetSpa-PST pesticide runoff model help us to better estimate pesticide from urban sources.