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Little information is available about the occurrence of neonicotinoid insecticides in surface water and sediment of the metropolitan regions around the rivers in China. Here we investigate the residual level of neonicotinoids in the Guangzhou section of the Pearl River. At least one or two neonicotinoids was detected in each surface water and sediment, and the total amount of neonicotinoids (∑ 5 neonics) in surface water ranged from 92.6 to 321 ng/L with a geometric mean (GM) of 174 ng/L. Imidacloprid, thiamethoxam and acetamiprid were three frequently detected neonicotinoids (100%) from surface water. As for the sediment, total concentration was varied between 0.40 and 2.59 ng/g dw with a GM of 1.12 ng/g dw, and acetamiprid and thiacloprid were the common sediment neonicotinoids. Western and Front river-route of the Guangzhou section of the Pearl River suffered a higher neonicotinoids contamination than the Rear river-route, resulting from more effluents of WWTPs receiving, and intensive commercial and human activities. Level of residual neonicotinoids in surface water was significantly correlated with the water quality (p < 0.01), especially items of pH, DO and ORP, and nitrogen and phosphorus contaminants. Compared with reports about residual neonicotinoids in water and sediment previously, the metropolitan regions of the Guangzhou could be confronted with a moderate contamination and showed serious ecological threats (even heavier than the Pearl Rivers). Our results will provide valuable data for understanding of neonicotinoids contamination in the Pearl River Delta and be helpful for further assessing environmental risk of neonicotinoids. Image 1 • Occurrence of neonicotinoids in the Guangzhou section of the Pearl River is examined. • At least one or two neonicotinoids was detected in each water and sediment sample. • IMI, THM and ACE were frequently detected (100%) neonicotinoids from surface water. • Western- and Front-suffered a higher neonicotinoids contamination than Rear river-route. • The Guangzhou section of the Pearl River could be confronted with a moderate neonicotinoid contamination. This article evaluates the residual level and distribution of neonicotinoids in the Guangzhou section of the Pearl River, South China. It is of great significance to fully understand the migration, transformation, contamination situation and ecological risk of neonicotinoid insecticides. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diverse people groups are confronted with distinct risks of neonicotinoid intake. • Boiling has negligible effect on the elimination of neonicotinoids. • The most frequently detected neonicotinoid was imidacloprid in the tap water. • Human activity and weather play important roles in neonicotinoids in the tap water. • Humans in 9 months –2 years are subjected to the highest drinking neonicotinoids. Neonicotinoids (NEOs) are the most widely used pesticides and have posed a serious threat to human health. However, data on human exposure to NEOs are extremely scarce. To bridge this gap, human exposure potential of NEOs through drinking water consumption and percutaneous penetration was evaluated with the influences of 17 age groups, 4 seasons, 6 regions, and 2 genders. The results showed that drinking water in the present study had an upper middle level of NEO contamination. Anthropogenic activity and weather condition played important roles in the regional distribution of NEOs in tap water. For both children and adults, N EOs intake from d rinking water e xposure (NDE) and p ercutaneous e xposure (NPE) in the south regions of China are significantly higher than those in the north regions, while the order of NDE and NPE by season is summer > spring = autumn > winter. Furthermore, human age and gender also have remarkable impacts on NDE and NPE. The age groups of children subjected to the highest NDE and NPE were 9 months – 2 years old and 9–12 years old, respectively. This study provides insights into the role of seasonal and regional influence, age and gender in the risk of drinking water and percutaneous exposure to NEOs. [ABSTRACT FROM AUTHOR]

• At least one neonicotinoid was detected in all soil, water and sediment samples. • Transport of raw agricultural products could be a source of NEOs in urban areas. • Pollution of NEOs in rural areas was significantly higher than that in urban areas. • Correlation and migration of NEOs residue in soil-water-sediment systems were studied. • Exposure to the current NEOs residue level of Guangzhou suggests a serious threat to sensitive non-target invertebrates. Residues and distribution of neonicotinoid insecticides (NEOs) in soil-water-sediment systems of the urban and rural areas of Guangzhou, South China were investigated. A total of 104 soil samples from 7 different functional zones and 29 water/sediment samples from creeks were collected. The results showed that at least one neonicotinoid insecticide was detected in all samples. The summed levels of five target neonicotinoids (∑ 5 neonics) were in the range of 0.003–229 ng/g dw for soil samples, 7.94–636 ng/L for water samples, and 0.017–31.3 ng/g dw for sediment samples, with a geometric mean of 0.59 ng/g dw, 153 ng/L and 1.11 ng/g dw, respectively. Soils from agricultural areas contained the highest residual NEOs, followed by commercial, traffic, residential, industrial, educational zones and parks. Among the seven different functional zones studied, imidacloprid was the most dominant NEO in the agricultural areas and commercial zones, whereas acetamiprid was dominant in the other five functional zones with different land-use types. Thiamethoxam and acetamiprid were the main NEOs in water and sediment samples collected from 29 creeks. The pollution of NEOs in soils, water and sediments from rural areas was higher than that in the counterparts from urban areas. Residual concentration of NEOs detected in soils, water and sediments showed significant correlations with each other. The distribution of NEOs in soil-water-sediment systems indicated that NEOs tended to concentrate in water, followed by sediments and soils, especially in urban areas. An evaluation of the exposure to the current level of the ∑ 5 NEOs in Guangzhou suggests a significant risk for aquatic and soil organisms, particularly under chronic exposures. The results of the present study offer valuable data to better understand the contamination and ecological risks of neonicotinoid insecticides in the rapidly developing urbanized region of South China. [ABSTRACT FROM AUTHOR]

Abstract Occurrence and distribution of five neonicotinoids (NEOs) in surface water and sediment were studied in the Pearl Rivers, including three trunk streams, Dongjiang, Beijiang, Xijiang River (DR, BR and XR), South China. At least one neonicotinoid was detected in surface water and sediment of the Pearl Rivers, with imidacloprid (IMI) and thiamethoxam (THM) being the frequently detected NEOs. Total amount of NEOs (∑ 5 neonics) in surface water and sediment ranged from 24.0 to 322 ng/L, and from 0.11 to 11.6 ng/g dw, respectively. Moreover, the order of contamination level of NEOs in the Pearl Rivers was as follows: XR > DR > BR for surface water, and BR > DR > XR for sediment. Local agricultural activities and effluents of wastewater treatment plants (WWTPs) could be major sources of NEOs in the Pearl Rivers. Solubilization and dilution of NEOs between surface water and sediment during different seasons (spring and summer) could be attributed to rainfall intensities or climate of the Pearl River Delta. An ecological risk assessment of the exposure to current environmental concentration of imidacloprid and ∑ 5 NEOs suggests a threat to sensitive non-target invertebrates, including aquatic invertebrates. Results would provide a better understanding of NEOs contamination in the Pearl Rivers, as well as being a reliable dataset for decision-making in contamination control and environmental protection. Graphical abstract Image 1 Highlights • At least one NEO was detected in water and sediment of the Pearl Rivers. • Imidacloprid and thiamethoxam were the most frequently detected NEOs. • Local agricultural runoff and effluents of WWTPs could be the main sources. • Seasonal differences of NEOs contamination could be attributed to rainfall intensities. • Exposure to current level would pose a potential threat to sensitive non-target invertebrates. [ABSTRACT FROM AUTHOR]