The interaction between atrazine and the mineral horizon of soil: a spectroscopic study

Purpose: In this paper, an attempt was made to explain the long-lasting occurrence of atrazine in soil. Despite the fact that this herbicide has been banned in European Union 10 years ago, it is still detected in the environment. Materials and methods: Soil samples (organic and mineral horizon), SiO₂ and Al₂O₃ sorbents were spiked with atrazine. The ultrasound-assisted extraction coupled with gas chromatography-electron capture detector was performed to establish the atrazine recovery depending on the type of soil horizon and sorbent. Fourier transform infrared spectroscopy (FTIR) analysis was conducted to determine the type of interactions between atrazine and sorbents. Results and discussion: The atrazine recovery was lower for the mineral horizon (15%) compared to the organic horizon (63%). This finding suggests an interaction between atrazine and the mineral components of soil. Therefore, attempts have been made to explain atrazine’s interaction with the main mineral components of soil, SiO₂ and Al₂O₃, and to investigate the influence of pH on atrazine’s behaviour in soil. The atrazine recoveries were 86.5 and 10.7% for Al₂O₃ and SiO₂, respectively. The obtained results demonstrated that the protonated atrazine exhibits stronger interactions with the soil mineral layer (recovery below 0.1%) in comparison to molecular form of atrazine (recovery 86%). FTIR results suggested interactions between atrazine and SiO₂. FTIR analysis revealed that 1,3,5-azidine ring interacts with SiO₂ molecule. Conclusions: In acidic soil, atrazine remediation is limited, especially if the soil contains minerals with high SiO₂ contents. This situation may cause the long-lasting persistence of atrazine in soil.