Comparison of neonicotinoid residues in soils of different land use types

Neonicotinoid insecticides (NEOs) have attracted particular attention in recent years due to their wide occurrence and potential impacts on the ecosystem and human health. This study aimed to compare the composition and level of NEOs in soils of different land use types. Two rounds of sampling were performed in Tianjin, China, with 158 soil samples in fall and 61 soil samples in spring collected from five types of land, i.e., greenhouse, orchard, farm, park and residential area. The concentrations of eight NEOs, i.e., imidacloprid (IMI), acetamiprid (ACE), thiamethoxam (THX), clothianidin (CLO), thiacloprid (THA), dinotefuran (DIN), nitenpyram (NIT) and flonicamid (FLO), were analyzed in the soil samples using LC-MS/MS. Six NEOs were detected, with IMI, ACE and THX being the most frequently detected ones. Concentrations of NEOs (arithmetic means in fall and spring, respectively) in greenhouse were the highest (2.52×10² and 4.59×10² ng g^-1), followed by in orchard (35.1 and 1.31×10² ng g^-1), park (50.4 and 1.02×10² ng g^-1), residential area (20.2 and 1.38×10² ng g^-1) and farm (25.5 and 84.2 ng g^-1). The contribution of individual NEO varied in soils of different land use types. Both IMI and THX were largely used in greenhouse, while IMI was the main NEO in the other four lands. The NEO levels in soils planted with different crops varied greatly. Extremely high levels of NEOs (>10³ ng g^-1) were observed in soils planted with watermelon, tomato and peach in greenhouse. The ubiquitous presence of NEOs in soils deserves more attention, particularly in greenhouse.