Abstract: To evaluate the herbicides residues in rice-crayfish and rice-crab systems in Jiangsu Province, 3 typical breeding bases were selected in these two systems. The dynamic non-target analysis was performed and the occurrence of herbicides residues was tested in biological samples (crayfish and crab) and the environmental samples (field water and field sediment) with ultra-high performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UPLC-Q-TOF MS) during the culture cycle. Accurate screening and ecological risk assessment of 21 herbicides were conducted through a quantitative analysis with high detection frequency and exposure risk. The results show that 12 and 11 herbicides were detected in the rice-crayfish and rice-crab system, respectively with monuron and cyanazine both detected in the two systems. The main residual herbicides in the rice-crayfish system were quinmerac[the frequency deducted was all relatively high in the crayfish, field water and field sediment samples, with the highest value reached to (12.1±0.17) μg·kg^-1, (22.5±2.47) μg·L^-1 and (21.6±1.91) μg·kg^-1, respectively], diuron[the highest value reached to (11.5±1.10) μg·kg^-1, (16.7±1.65) μg·L^-1 and (19.7±0.97) μg·kg^-1, respectively], cyanazine[the highest values reached to (11.2±0.36) μg·kg^-1,(22.5±3.01) μg·L^-1 and (29.5±3.20) μg·kg^-1, respectively], chlorotoluron[the frequency of detection was only relatively high in the field sediment samples and the highest value reached to (20.1±2.99) μg·kg^-1] and nicosulfur[the highest value reached to (15.8±1.05) μg·kg^-1]. The main residual herbicides in the rice-crab system were benzeneacetamide[the frequency of detection was only relatively high in the field sediment samples and the highest value reached to (20.2±2.05) μg·kg^-1], thiobencarb[the frequency of detection were all relatively high in the field water and field sediment samples and the highest values reached to (11.2±1.01) μg·L^-1 and (20.1±3.28) μg·kg^-1, respectively], bensulfuron methyl[the highest value reached to (26.4±3.17) μg·kg^-1], monuron[the highest values reached to (11.7±2.03) μg·L^-1 and (20.1±2.64) μg·kg^-1, respectively], 2,4-D-butyl ester[the highest value reached to (19.5±2.43) μg·kg^-1] and atrazine[as with the benzeneacetamide and the highest value reached to (24.7±1.98) μg·kg^-1]. Herbicide residues were mainly detected in environmental samples, especially in field sediment, less in crayfish and crab, and the residues were mainly concentrated in the early stage of aquaculture, and the frequency and value were controllable during the harvest time. The results of this study show that the comprehensive ecological risk of herbicides in crayfish and crab was at medium level, while the risk of field water and field sediment were both at high level, in particular, 10 of the 11 herbicides detected in field sediment were in high risk. In this study, it was evident that the herbicides pollution in rice-crayfish and rice-crab systems in Jiangsu Province were in the order of field sediment > field water > aquatic product (crayfish and crab). The results indicate that herbicide residues in field sediment have a potential risk to the aquatic environment, and the risk of herbicide residues pollution to aquatic product (crayfish and crab) is at controllable level during the harvest period.

Key words: herbicide, non-target analysis, high-resolution mass spectrometry, occurrence, rice-crayfish system, rice-crab system