Urban Soil Contamination by Current-Use Pesticides and Their Transformation Products: Insights from Targeted Analysis and Suspect Screening

Urban soils are increasingly recognized as sources and reservoirs of current-use pesticides in the urban environment, yet the scope of contamination remains poorly characterized. This study combined targeted analysis and suspect screening to investigate 60 soil samples from four urban land use types (parks, vacant lots, residential lots, and urban farms) and three socioeconomically distinct residential communities in Metro Detroit, Michigan, United States. Targeted analysis identified 20 pesticides, including 4 insecticides, 13 herbicides, and 3 fungicides, and each site contained 4 to 15 pesticides. Significant differences existed among land use types and residential communities. Residential lots exhibited the highest concentration of current-use pesticides, particularly imidacloprid (up to 78 ng g⁻¹), bromoxynil (up to 46 ng g⁻¹), and 2,4-D (up to 84 ng g⁻¹). The high-income community had the highest detection frequencies of insecticide imidacloprid, pre-emergent herbicide prodiamine, and fungicide propiconazole. The middle- and low-income communities were dominated by post-emergent herbicides 2,4-D and bromoxynil and fungicides such as azoxystrobin and carbendazim. Suspect screening identified over 100 probable pesticides and possible transformation products in urban soils. Some transformation products were detected at levels significantly exceeding their parent compounds. These findings reveal distinct variations in pesticide profiles by land use types and socioeconomic statuses. This study also underscores the importance of including transformation products in risk assessments of urban pesticides.