Urbanization is often accompanied by aquatic metal(loid) pollution, which is regulated by dissolved organic matter (DOM). However, the relationships between dissolved metal(loid) concentration and the bulk, chromophoric, and fluorescent DOM in black and odorous urban rivers are still poorly understood. Here, we investigated the dissolved metal(loid) concentrations of Zn, Cu, Cr, As, Pb, and Cd and their correlations with DOM-related parameters in water samples from a polluted urbanized watershed in Shenzhen, China. The results showed that the Zn and Cu concentrations in the mainstream and tributary exceeded the national standards, and the wastewater treatment plant (WWTP) was an important source, as indicated by the abrupt concentration increases downstream of the WWTP. The dissolved metal(loid) concentrations were not always significantly correlated with the dissolved organic carbon (DOC) concentration or the ultraviolet absorbance at 254 nm (UV₂₅₄); however, they were more likely to be correlated with the maximum fluorescence intensity (Fmax) of protein-like fluorescent DOM components. A strong correlation between the Cu/DOC ratio and specific UV₂₅₄ (SUVA₂₅₄) previously reported did not exist in the present study. Instead, the Cu/DOC ratio was positively correlated with the Fmax/DOC ratios for protein-like fluorescent DOM components. Our study highlights that protein-like fluorescent DOM may be more important than humic-like fluorescence DOM and chromophoric DOM in terms of interacting with dissolved metal(loid)s in black and odorous urban rivers.

Fine roots are vital for plant development and carbon biogeochemical cycling in terrestrial ecosystems. Flooding is known to regulate the physiology and morphology in plant roots; however, its impact on molecular-level characteristics of carbon compounds (carbon traits) in fine roots remains largely unexplored, which limits our understanding of root adaptation and decomposition under changing environments. Here, we used a sequential extraction method, starting from nonpolar to polar solvents, in order to obtain dichloromethane- and methanol-extractable (F_DcMe) fractions, base-hydrolyzable (F_KOHhy) fractions, and CuO-oxidizable (F_CuOox) fractions from fine roots of Dysoxylum binectariferum, which is naturally grown in soil and water. Subsequently, we characterized them using targeted gas chromatography–mass spectrometry and nontargeted Fourier transform ion cyclotron resonance mass spectrometry. Also, decomposition experiments were conducted on soil- and water-grown roots under aerobic and anoxic conditions. Results showed a consistent increase in the unsaturation degree and aromaticity of the analytes from F_DcMe to F_CuOox fractions. Both analyses were sufficiently sensitive to show that, compared to soil-grown roots, the water-grown roots developed more polyphenolics with a high unsaturation degree and aromaticity and had more nonstructural compositions. Furthermore, although flooding provided an anoxic condition that slowed down root decomposition, the adaptive strategy of developing more nonstructural labile components in water-grown roots accelerated root decomposition, thereby counteracting the effects of anoxia. This advances our understanding of biogeochemical processes in response to global environmental change.

The adhesion of deleterious bacteria on titanium substrates not only causes economic losses but also endangers human life and health. The study is expected to address the challenging issues of using ZnO as an antibacterial material, including low bactericidal efficiency without lighting, susceptibility to ZnO cluster formation, and easy adhesion of bacteria to its surface. It is proposed that the prepared ZnO nanorod arrays with a hexagonal wurtzite structure on the surface of titanium-based materials can address the issue of ZnO cluster formation. Remarkably, a mere 3.49 g cm⁻² of decorated Ag/AgCl achieves over 99% sterilization efficiency without lighting. The incorporation of FAS (1H,1H,2H,2H-perfluorodecyltrimethoxysilane) molecules with low surface energy enables the prepared Ti@ZnO@Ag/AgCl@FAS to attain a Cassie–Baxter wetting state, thereby imparting exceptional bacterial anti-adhesion properties exceeding 99.50%. Furthermore, antibacterial and anti-adhesion models have been proposed to elucidate the underlying mechanisms. This innovative approach is anticipated to be adaptable for application across various material substrates, which opens up a new avenue for the application of the antibacterial and bacterial anti-adhesion properties on the surface of ZnO materials.

Fine roots constitute a fundamental source of litter decomposition and humus formation in terrestrial ecosystems. However, molecular-level traits of carbonaceous organics in fine roots grown in different media, such as soil and water, remain largely unexplored, which limits our understanding of root adaptation and decomposition under changing environments. Here, we used a sequential extraction method to obtain dichloromethane-and-methanol-extractable (F_DcMe), base-hydrolyzable (F_KOHhy), and CuO-oxidizable (F_CuOox) fractions from fine roots of Dysoxylum binectariferum grown in soil and water and characterized them using targeted gas chromatography-mass spectrometry and non-targeted Fourier transform ion cyclotron resonance mass spectrometry. Also, decomposition experiments were conducted on soil- and water-grown roots under aerobic and anoxic conditions. Results showed a consistent increase in unsaturation degree and aromaticity of the analytes from F_DcMe to F_CuOox fractions. Both analyses were sufficiently sensitive to show that compared to soil-grown roots, the water-grown ones developed more polyphenolics with a high unsaturation degree and aromaticity and had more non-structural compositions. Furthermore, although flooding provided an anoxic condition that slowed down root decomposition, the adaptive strategy of developing more non-structural labile components in water-grown roots accelerated root decomposition, thereby counteracting the effects of anoxia. Our results highlight that the complementary targeted and non-targeted analyses of sequentially extracted fractions can provide the supplementary molecular-level carbon traits of fine roots. It advances our understanding of biogeochemical processes in response to global environmental change.