Neonicotinoid insecticides in well-developed agricultural cultivation areas: Seawater occurrence, spatial-seasonal variability and ecological risks

Abstract

Neonicotinoids (NEOs) are widely used insecticides and have been detected in aquatic environments globally. However, little is known about NEOs contamination in the coastal environments under the terrestrial pressure of multiple planting types simultaneously. This study investigated the occurrence, spatial-seasonal variability, and ecological risks of NEOs along the coast of the Shandong Peninsula during the dry and wet seasons, where located many largest fruit, vegetable, and grain production bases in China. The concentrations of ∑NEOs in seawater were higher in wet seasons (surface: 195.46ng/L; bottom: 14.56ng/L) than in dry seasons (surface: 10.07ng/L; bottom: 8.45ng/L). During the wet seasons, NEOs peaked in the northern and eastern areas of the Shandong Peninsula, where the inland fruit planting area is located. While dry seasons had higher concentrations in Laizhou Bay, influenced by rivers from vegetable-growing areas. Grain crops, fruit, and cotton planting were major NEOs sources during wet seasons, while wheat and vegetables dominated in dry seasons. Moderate or above ecological risks appeared at 53.8% of the monitoring sites. Generally, NEOs caused high risks in the wet seasons mainly by Imidacloprid, and medium risk in the dry seasons by Clothianidin, which should be prevented and controlled in advance. Environmental ImplicationNeonicotinoid pesticides, an emerging contaminant, have been detected in many environmental media and exhibit toxicity to non-target organisms. The coastal waters of the Shandong Peninsula, the center of grain production, were selected as the research object. The temporal and seasonal variation coincides with the local planting types and the usage preference of NEOs. The potential sources of NEOs in wet seasons were generally rain crops, fruit, and cotton planting, whereas wheat and vegetables in dry seasons. Finally evaluated according to risk quotient showed that neonicotinoids were of moderate risk in 58.8% of study areas.