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Natural colloids (NCs) are heterogeneous mixtures of particles in the aquatic environments that are strongly influenced by land use and hydrochemical properties between terrestrial and aquatic environments. However, the relevant study was paid little attention to the difference among the waters with different sizes of particles (e.g., suspended particulate matter-SPM, NCs, and the truly dissolved phase). In this study, the spectral properties of these different waters were investigated from different land-use types in the Yuan River basin, China. Results of the UV-visible absorption spectral showed that with the particle size increased, the aromaticity, chromophoric dissolved organic matter, and humification degree of organic matter increased, while the condensation degree decreased. Data analysis from the fluorescence indices indicated that the source and the autochthonous feature of the truly dissolved water differed from that of NCs and SPM. Whereas the protein-like component was mainly combined with the relatively larger size of particles (i.e., SPM and NCs), especially in the downstream. Redundancy analysis revealed that the spectral characteristics of the water samples were strongly influenced by the hydrochemical parameters (>45%) with comparison to land-use type (nearly 10%). Furthermore, the impact of land-use type on the spectral properties was differed between the large and small scale of the buffer strips and between the mainstream and the tributaries. And this effect was more significant on the fluorescence properties in the mainstream and the spectral properties for NCs than for SPM. The study helps to understand the biogeochemical effects of the waters with different particle sizes.

Natural colloids (NCs) are heterogeneous mixtures of particles in the aquatic environments that are strongly influenced by land use and water quality between terrestrial and aquatic environments. However, the relevant study paid little attention to the difference among the waters with different sizes of particles (e.g., suspended particulate matter (SPM), NCs, and the truly soluble substances). In this study, the spectral properties of these different waters were investigated from different land-use types in the Yuan River basin, China. Results of the UV-visible absorption spectral showed that with the particle size increased, the aromaticity, chromophoric dissolved organic matter, and humification degree of organic matter increased, while the condensation degree decreased. Data analysis from the fluorescence indices indicated that the source and the autochthonous feature of the truly soluble substances differed from that of NCs and SPM, whereas the protein-like component was mainly combined with the relatively larger size of particles (i.e., SPM and NCs), especially the downstream. Although the spectral characteristics of the water samples were strongly influenced by the water quality ( 45%), the land-use type might be the real potential impactor. Furthermore, the influence of land-use type on the spectral properties differed between the large and small scale of the buffer strips and between the mainstream and the tributaries. And this effect was more significant on the fluorescence properties in the mainstream and the spectral properties for NCs than for SPM. The study helps to understand the biogeochemical effects of the waters with different particle sizes.

Solar irradiation (λ ≥ 290 nm) has been introduced into a traditional Fe2+ activated persulfate (PS) system (Fe2+/PS). The combination system of solar light, Fe2+ and PS system (solar/Fe2+/PS) exhibited a rapid and continuous oxidation of chloramphenicol (CAP) in solution, and showed great advantages over the Fe2+/PS process by accelerated degradation efficiency. A presumed reason is that Fe2+ was slowly and continuously recycled by solar light, and the reductive photolysis Fe3+ to Fe2+ was promoted concomitantly with the production of additional hydroxyl radical (HO ). The optimal dosages of PS and Fe2+ were determined by batch experiments. pH significantly influenced CAP degradation, and an acidic condition favored the reaction. Both HO and sulfate radical (SO4 −) were considered to be the mainly oxidant to remove CAP, and HO had a higher contribution than SO4 −. The presence of HCO3−, NO3−, NO2−, H2PO4−, HPO42− demonstrated adverse effects on CAP decay in solar/Fe2+/PS process. Coexisting Cl− ions slightly accelerated the CAP degradation rate at an appropriate concentration (0.6–6 mM) but gradually inhibited at a higher Cl− (12–36 mM) content. The results clearly showed that CAP presented the slowest degradation rate in wastewater, and the colloids should be taken into consideration prior to the application of solar/Fe2+/PS for wastewater treatment. Nonetheless, up to 89.7%, 94.7%, and 65.4% of CAP were removed from the filtrate, permeate, and retentate within 100 min, respectively. It is expected that the modified process could be applied for CAP removal from wastewater containing a considerable colloids/organic content. Finally, 8 major intermediate products were identified and the preliminary degradation pathways were proposed.