The Degradation Process of Typical Neonicotinoid Insecticides in Tidal Streams in Subtropical Cities: A Case Study of the Wuchong Stream, South China

Abstract

Neonicotinoid insecticides (NEOs) are commonly used to prevent unwanted insects in urban fields. Degradation processes have been one of the important environmental behaviors of NEOs in an aquatic environment. In this research, hydrolysis, biodegradation, and photolysis processes of four typical NEOs (i.e., thiacloprid (THA), clothianidin (CLO), acetamiprid (ACE), and imidacloprid (IMI)) were examined through the adoption of response surface methodology–central composite design (RSM-CCD) for an urban tidal stream in South China. The influences of multiple environmental parameters and concentration levels on the three degradation processes of these NEOs were then evaluated. The results indicated that the three degradation processes of the typical NEOs followed a pseudo-first-order reaction kinetics model. The primary degradation process of the NEOs were hydrolysis and photolysis processes in the urban stream. The hydrolysis degradation rate of THA was the highest (1.97 × 10−5 s−1), and that of CLO was the lowest (1.28 × 10−5 s−1). The temperature of water samples was the main environmental factor influencing the degradation processes of these NEOs in the urban tidal stream. Salinity and humic acids could inhibit the degradation processes of the NEOs. Under the influence of extreme climate events, the biodegradation processes of these typical NEOs could be suppressed, and other degradation processes could be further accelerated. In addition, extreme climate events could pose severe challenges to the migration and degradation process simulation of NEOs.

Status Report on Neonicotinoid Pollution in Japan: Emphasis on Human, Animal, and Environmental Health

“…In water, neonicotinoid residues may undergo degradation through hydrolysis, biodegradation, and photolysis; however, these processes may be greatly influenced by temperature, salinity, and humic acids (Jia et al, 2023). Under neutral or acidic p H conditions, neonicotinoid residues resist hydrolysis in water; however, these chemicals degrade rapidly in the water medium in adequate sunlight (Thompson et al, 2020).…”