Interaction of heavy metals and biocide/herbicide from stormwater runoff of buildings with dissolved organic matter

Stormwater runoff from roofs and facades can be contaminated by heavy metals and biocides/herbicides. High efficiency on-site treatment methods are now urgently needed to safeguard the ecosystem. The basis for developing such treatment facilities is an in-depth understanding of their interactions with dissolved organic matter (DOM), as this affects their migration in the environment. Hence, the interactions between copper (Cu), zinc (Zn), benzyldimethyl-tetradecylammonium chloride dihydrate (BAC), mecoprop-P (MCPP) and DOM at pH 5 to 9 were investigated separately in this study. The evaluation of the interaction processes was achieved by applying excitation emission matrix and parallel factor analysis (EEM-PARAFAC) to titration samples; obtained data were fitted by two different models. Mechanisms involved in BAC/MCPP-DOM interactions were revealed by Fourier-transform infrared spectroscopy (FTIR) and two-dimensional correlation spectrum (2D-COS) analysis. Results showed that the applied DOM was composed of the two different fluorescent components C1 and C2. More interaction with C1 than with C2 was observed for both Cu/Zn and BAC/MCPP. Increasing the pH enhanced the interactions between Cu/Zn and DOM. At pH 5 with a maximum quencher addition, the remaining fluorescence of CuC1 and ZnC1 were 15.7% and 87.1%, respectively. Corresponding data at pH 9 decreased to 3% and 69.5%. Contrarily, interactions between BAC/MCPP and DOM were impaired by high pH conditions. The increase of pH from 5 to 9 with maximum BAC and MCPP added raised the remaining fluorescence of BAC-C1 and MCPP-C1 by 15.9% and 21.3% separately. The fitting outcomes from the Ryan-Weber equation (Cu/Zn titration) and the Stern-Volmer equation (BAC/MCPP titration) corresponded well with the titration studies. FTIR coupled with 2D-COS analysis revealed that mechanisms involved in BAC/MCPP titration include hydrogen bonding, pi-pi interaction, and electrostatic effect. The order of mechanisms taking effect during the interaction with DOM is affected by the molecular structure of BAC and MCPP.

Automated summary

This study investigates the interactions between copper, zinc, BAC, MCPP, and dissolved organic matter at different pH levels, and evaluates and reveals these interactions using various analytical methods. The results show that the interactions between different substances and dissolved organic matter vary and are influenced by the pH of the solution.