Characteristics of dissolved organic matter in urban road runoff under different traffic densities in Beijing, China

Removal of dissolved organic matter in road runoff with sludge-based filters from the drinking water treatment plant

Road runoff underwent treatment using a filter filled with sludge from drinking water treatment plants to assess its capacity for removing dissolved organic matter (DOM). This evaluation utilized resin fractionation, gel permeation chromatography, three-dimensional excitation-emission matrix fluorescence spectroscopy, and UV-Visible spectroscopy. The filter demonstrated enhanced efficiency in removing dissolved organic carbon, achieving removal rates between 70 and 80%. It effectively targeted macromolecular DOM components present in road runoff, with hydrophobic organic compounds showing higher removal rates than hydrophilic ones. Additionally, acidic and neutral organic substances were preferentially removed over basic organic compounds. Fluorescent substances identified in road runoff DOM included fulvic acid-like, humic acids, and protein-like substances, all of which exhibited significantly reduced intensities in fluorescence peaks after filtration. Furthermore, filtration led to a decrease in the aromatization and humification of runoff DOM due to the effective removal of aromatic compounds and macromolecular structural components.

Binding capacity and co-migration potential of Pb(II), Cu(II), and Cd(II) on colloids in road runoff

To evaluate the co-migration potential between heavy metal ions and road runoff colloids, the influence of contact time, temperature, initial concentration of metal ions, pH, humic acid (HA), and polymetallic coexistence on the binding capacity of heavy metals onto runoff colloids were investigated. The adsorption of heavy metals by runoff colloids was extremely rapid, approximately 80% of the equilibrium adsorption capacity was achieved in the first 30 min. The binding capacity exhibited an increasing trend with the initial concentration of metal ions increasing, and the maximum adsorption capacities of Pb(II), Cu(II), and Cd(II) achieved 159.13, 56.06, and 78.35 mg/g at 298 K, respectively. The adsorption capacity of Cu(II) and Cd(II) by runoff colloids increased with temperature increasing, while it displayed a converse trend for Pb(II). Neutral pH facilitated the combination of metal ions and runoff colloids. The presence of humic acid increased the binding capacity of Pb(II), Cu(II), and Cd(II) onto runoff colloids by 72.19, 63.31, and 13.83mg/g, respectively. Compared to the monometallic systems, the binding capacity of Pb(II), Cu(II), and Cd(II) by runoff colloids decreased by 18.44%, 22.35%, and 56.06% in polymetallic systems, respectively. Pb(II) bounded with colloids in the road runoff should be controlled preferentially to avoid their migrations to aquatic environments.

Advancing illicit connection diagnosis of urban stormwater pipes: Comprehensive analysis with EEM fluorescence spectroscopy

Urban drainage systems are significant contributors to the issue of black-odorous water bodies. The current application of stormwater pipe inspection technologies faces substantial limitations, especially in industrial areas with diverse wastewater. This study introduced an innovative approach using excitation-emission matrix (EEM) fluorescence spectroscopy for rapid and accurate diagnosis, providing a new perspective for diagnosing illicit connections. In single wastewater-type areas like residential zones, the method achieved a remarkable 91.5 % accuracy solely through spectra observation and fluorescence peak intensity comparison, outperforming conventional NH3-N-based techniques, which reached an accuracy of only 68.1 %. For regions with complex wastewater scenarios, after EEM subtraction, the residual spectra can be roughly categorized into four distinctive categories based on characteristics. This provides a preliminary assessment and helps in initially identifying the types and sources of inflowing wastewater. Furthermore, the least squares (LS) method refines diagnosis results, offering calculated coefficients reflecting the probability and severity of suspected wastewater intrusion. Simulation experiments and field sample analyses validated the feasibility and accuracy of the EEM-based method, highlighting its advantages for diagnosing illicit connections in both single and mixed wastewater scenarios. The results can significantly narrow down the investigation scope and enhance the confirmation of wastewater sources, exhibiting promising application prospects.

Fluorescence fingerprint as an indicator to identify urban non-point sources in urban river during rainfall period

Nowadays, the urban non-point source (NPS) pollution gradually evolved as the main contributor to urban water contamination since the point source pollution was effectively controlled. It was imperative to perform urban NPS identification in urban river to meet the requirements of precise source governance. In this study, the real-time detection about water quality parameters and fluorescence fingerprints (FFs) was performed for BX River and its outlets during rainfall period. EEM-PARAFAC and component similarity analyses discovered that the pollution encountered by BX River mainly came from road runoff and untreated municipal wastewater (UMWW) overflow. The C1 (tryptophan-like) and C3 (terrestrial humic-like) components located at Ex/Em = ∼230(280)/340 and ∼275/430 nm were both detected in these two kinds of urban NPS. The C2 components of road runoff and UMWW overflow displayed remarkable differences, which located at Ex/Em = 250/385 and 245/365 nm, respectively, thus could be served as indicators for distinguishing them. During rainfall period, the outflow from rainwater outlets (RWOs) constantly showed similar FF features to road runoff, while the FFs of outflow from combined sewer outlets (CSOs) alternated between those of road runoff and UMWW overflow. The FF features of sections in BX River changed in response to the dynamic variations in FFs of the outlets, which revealed real-time pollution causes of BX River. This work not only realized the identification and differentiation of urban NPS, but also elucidated the dynamic variations of pollution characteristics throughout the entire process of "urban NPS-outlets-urban river", and demonstrated the feasibility of FF technique in quickly diagnosing the pollution causes of urban river during rainfall period, which provided important guidance for urban NPS governance.

Occurrence of traffic related trace elements and organic micropollutants in tunnel wash water

Substantially polluted tunnel wash water (TWW) is produced during road tunnel maintenance. Previous literature has reported the presence of trace elements and polycyclic aromatic hydrocarbons (PAHs). However, it was hypothesized that other organic pollutants are present, and more knowledge is needed to prevent environmental harm. This study reveals for the first time the presence of four short- and 17 long-chained per- and polyfluoroalkyl substances (PFASs), three benzothiazoles (BTHs), six benzotriazoles (BTRs), four bisphenols, and four benzophenones in TWW from a Norwegian road tunnel over a period of three years. Concentrations of PAHs, PFASs, BTHs, and BTRs were higher than previously reported in e.g., road runoff and municipal wastewater. Trace elements and PAHs were largely particulate matter associated, while PFASs, BTHs, BTRs, bisphenols, and benzophenones were predominantly dissolved. 26 of the determined contaminants were classified as persistent, mobile, and toxic (PMT) and are of special concern. It was recommended that regulations for TWW quality should be expanded to include PMT contaminants (such as PFPeA, PFBS, BTR, and 4-OH-BzP) and markers of pollution (like 2-M-BTH, 2-OH-BTH, and 2-S-BTH from tire wear particles). These findings highlight the need to treat TWW before discharge into the environment, addressing both, particulate matter associated and dissolved contaminants.