Reconnaissance of imidacloprid in select Virginia streams, 2024–2025

This data release presents concentration results obtained using an enzyme-linked immunosorbent assay (ELISA) method for imidacloprid and other neonicotinoid insecticides from samples collected in 30 urban streams across Virginia between August 2024 and July 2025. ELISA analyses were conducted at the U.S. Geological Survey Strategic Laboratory Science Branch in Boulder, Colorado. The ELISA method uses antibodies to detect target compounds and is designed for imidacloprid; however, the antibodies also respond to structurally similar compounds to varying degrees, a phenomenon known as cross-reactivity. Reported cross-reactivity values indicate the relative sensitivity of the assay to other neonicotinoids compared to imidacloprid (100%). For example, clothianidin exhibits 121% cross-reactivity, meaning the assay is slightly more sensitive to clothianidin than imidacloprid, while thiacloprid (13%), acetamiprid (4%), and thiamethoxam (<0.1%) show progressively lower responses. These values are important for interpreting results because the reported concentrations represent the combined response from all compounds that cross-react with the antibody, not just imidacloprid. Quality assurance results, which include blank, replicate, laboratory reagent spikes, and environmental matrix spikes, are provided. Additionally, the dataset provides water-quality measurements recorded at the time of sampling, including water temperature, specific conductance, dissolved oxygen, turbidity, pH, and gage height.