Investigating the pollutant-removal performance and DOM characteristics of rainfall surface runoff during different ecological concrete revetments treatment

Four different types of ecological concrete (EC), including an applied concrete (AC), and three kinds of modified concretes (MC1-MC3) were used to study the removal performance of rainfall surface runoff and their impacts on changes in dissolved organic matter (DOM). The results showed that MC3 indicated the best performance of water purification; the removal ratios of total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH4+-N), total organic carbon (TOC), and total suspended solids (TSS) were 58.08%, 95.57%, 92.44%, 91.72%, and 87.62%, respectively. Fluorescence excitation-emission matrix (EEM) spectroscopy combined with parallel factor analysis (PARAFAC) was able to identify five fluorescent components (C1-5), including three humic-like components (C1, C3, and C4) and two protein-like components (C2 and C5). The three MCs could more effectively remove both small-molecular-weight protein-like component C2 and high-molecular-weight humic-like components C1, C3, and C4, compared to the AC. The result of two-dimensional correlation spectroscopy (2D-COS) showed that protein-like components had higher susceptibility than humic-like substances did. Fluorescent components at 330, 305, 410, and 410 nm were found with a preferential change in the AC, MC1, MC2, and MC3 respectively, suggesting that fulvic-like, protein-like, humic-like, and humic-like substances can be removed preferentially in the AC, MC1, MC2, and MC3 respectively. This study is valuable for improving surface runoff purification of rainwater in rural areas and for reducing agricultural non-point source pollution.