posted on 2024-01-03, 18:07authored byRonghua Qin, Ziyang Wei, Yingyan Huang, Xueyuan Bai, Ziqi Zhang, Zhiqing Zhong, Duan Gui, Lei Wang, Hongwen Sun, Tao Zhang
This
study investigated the residual levels of eight parent neonicotinoid
insecticides (p-NEOs) and three NEO metabolites (m-NEOs) in surface
waters of river–estuary–ocean systems on a large geographical
scale in South China. Imidacloprid, thiamethoxam, acetamiprid, and
clothianidin were dominant NEOs in surface waters. High levels of
∑NEOs were found in the upper reaches of Guangzhou section
of the Pearl River (PR_GZ), indicating multiple input sources of NEOs
in PR_GZ. Additionally, the decreased influence of terrestrial input
and human activities was observed along with the flow direction, where
the order of ∑NEOs concentration was PR_GZ (inland river, 64.5
ng/L) > Pearl River Estuary (estuary, 33.9 ng/L) > Xisha Islands
of
the South China Sea (SS_XS, open sea area, 27.0 ng/L); and the level
in Northwestern South China Sea (coastal sea, 49.9 ng/L) was also
higher than that in open sea area. The estimated annual fluxes of
NEOs released into the South China Sea totaled 34.8 ± 20.4 tons,
most of which come from the Pearl River basin. To the best of our
knowledge, this is the first study to assess the concentrations, distribution,
and source analysis of NEOs in river–estuary–ocean systems
in South China.