Quantitative structure-toxicity relationships of halobenzoquinone isomers on DNA reactivity and genotoxicity.

Halobenzoquinones (HBQs) are an emerging class of drinking water disinfection byproducts that have been predicted as bladder carcinogens. However, data on the genotoxicity of HBQs are still scarce. This study performed a quantitative structure-toxicity relationship (QSTR) analysis of HBQ isomers on DNA reactivity and genotoxicity. The interaction of HBQs with calf thymus DNA (ct-DNA) was studied using multi-spectroscopic and molecular docking techniques. UV-Vis absorption spectra observed a significant hyperchromic effect with the increase of HBQ concentration. The fluorescence intensity of both probe-ct-DNA decreased with the increasing concentration of HBQs, indicating that the interaction mode between each HBQs and DNA was quite complicated, and there were both minor groove binding and intercalation binding. Molecular docking showed that HBQs interacted with DNA predominantly via hydrogen bond at guanine-rich areas in the minor groove of DNA. The genotoxicity of HBQs on human hepatocytes (L-02) was evaluated by micronucleus test, and the results showed that HBQs could cause significant chromosomal damage. The rank order of HBQ isomers on DNA reactivity and genotoxicity was 2,5-HBQs > their corresponding 2,6-HBQs. QSTR analysis found that dipole moment is the key structural descriptor influencing both DNA reactivity and genotoxicity of HBQ isomers. This study suggested that HBQs have caused genotoxicity which was influenced by their isomeric effects, warranting a comprehensive understanding of the genotoxic and carcinogenic risks associated with HBQs exposure.

Particle size distribution and pollutant dissolution characteristics of road-deposited sediment in different land-use districts: a case study of Beijing.

The high pollutants loading of road-deposited sediment (RDS) make it the main threat to receiving water bodies in stormwater management; however, the characteristics of RDS have not yet been sufficiently studied. In this study, samples were collected from three different land-use type areas (campus, residential, and commercial) in Beijing, China, and analyzed for particle size distribution, chemical compositions, and dissolution characteristics. The results revealed that RDS in the sampling sites mainly consisted of particles < 63 µm, which accounted for 40.3%, 30.5%, and 30.3% of the total in samples from campus, residential, and commercial sites, respectively. In addition, the mass percentage of sediments decreased with increasing particle size in all three sampling sites. The highest pollutants loading were mainly found in particles between 125 and 250 µm. The pollutant loading occurred in the following order: commercial > residential > campus for COD and heavy metals (Cr, Cd, Pb, Cu), and campus > residential > commercial for TN, NH4+-N, and PO43--P. The pollutants dissolved capacity (DC) and pollutants dissolved velocity (DV) both decreased with increasing particle size. Overall, the results of this study highlight the importance of removing fine particles to controlling road runoff pollution.