Humic acid nature and compound structure together determine the capacity of soil to sorb Avermectin B1a and its derivatives

•Sorption/desorption of Avermectin B1a and derivatives by three soils and HA were investigated.•13C NMR and PCA revealed the positive correlation of N-alkyl/O-alkyl carbon on the sorption.•Aliphatic/aromatic carbon showed a negative correlation on sorption.•Polar functional group of HA is the main sorption site for Avermectin B1a and derivatives.•H-bonding is the main mechanism of pesticide sorption by HA.