Effects of dinotefuran and humic acid on cadmium migration and transformation in sediments

Abstract The heavy application of dinotefuran (DNT) pesticide in agricultural production and the humic acid (HA) ubiquitous in the aqueous systems have burdened the environment as a new pollutant. The chemical fraction and mobility of cadmium (Cd) in sediments of urban river environments in which DNT and HA coexist are poorly understood. In this study, sequential extraction, ultraviolet-visible spectroscopy (UV-vis), fluorescence excitation-emission matrix (EEM), fourier transform infrared spectrometer (FTIR) techniques, and the Stern-Volmer equationwere integrated to identify the effects of DNT, pH, concentration and molecular weight (Mw) fractions of HA on the content and chemical fraction of Cd in sediments. The DNT dosage strongly affected the Fe–Mn oxide-associated Cd chemical fraction in sediments. HA facilitated migration of Cd from sediments to water. Cd release from sediments was also promoted by a lower pH of 5–6 compared to pH 8–9. Increasing concentrations of higher molecular weight HAs of >100 kDa, 30–100 kDa, and 30–10 kDa reduced total Cd, exchangeable/acid soluble fraction, and reducible fraction content in sediments, while 1–10 kDa and <1 kDa HA did not significantly influence Cd chemical fraction or content. The present study provides new insights into the environmental risks and partitioning of Cd in sediments under co-exposure to DNT and HA.