Human activities impose important disturbances on both organic and inorganic chemistry in fluvial systems. In this study, we investigated the intra-annual and downstream variations of dissolved organic carbon (DOC), dissolved organic matter (DOM) excitation-emission matrix fluorescence (EEM) with parallel factor analysis (PARAFAC), major ions, and dissolved inorganic nitrogen (DIN) species in a mountainous tributary of the Yellow River, China. Both DOM quantity and quality, as represented by DOC and DOM fluorescence respectively, changed spatially and seasonally in the studied region. Fluorescence intensity of tryptophan-like components (C3) were found much higher at the populated downstream regions than in the undisturbed forested upstream regions. Seasonally, stronger fluorescence intensity of protein-like components (C3 and C4) was observed in the low-flow period (December) and in the medium-flow period (March) than in the high-flow period (May), particularly for the downstream reaches, reflecting the dominant impacts of wastewater pollution in the downstream regions. In contrast to the protein-like fluorescence, humic-like fluorescence components C1 and C2 exhibited distinctly higher intensity in the high-flow period with smaller spatial variation indicating strong flushing effect of increasing water discharge on terrestrial-sourced humic-like materials in the high-flow period. Pollution-affected dissolved inorganic ions, particularly Na, Cl, and NH-N, showed similar spatial and seasonal variations with protein-like fluorescence of DOM. The significant positive correlations between protein-like fluorescence of DOM and pollution-affected ions, particularly Na, Cl, and NH-N, suggested that there were similar pollution sources and transportation pathways of both inorganic and organic pollutants in the region. The combination of DOM fluorescence properties and inorganic ions could provide an important reference for the pollution source characterization and river basin management.

To understand the effects of an acidic environment on the internal structure of sandstone from the Yungang Grottoes, Datong, China, the physicochemical properties of fresh and weathered sandstone samples and their compressional wave (P-wave) velocities in response to different concentrations of H 2 SO 4 and HNO 3 solution were investigated. X-ray diffraction (XRD) and a scanning electron microscope equipped with energy dispersive X-ray spectrometer (SEM-EDX) were used to determine grain morphology and chemical composition. The results show that the sandstone, which mainly consists of silicon dioxide and calcium carbonate, became more complicated in composition after weathering. A nonmetallic ultrasonic detector was used to measure the P-wave velocities of sandstones in a natural state and soaked with ultrapure water and with H 2 SO 4 and HNO 3 at concentrations of 0.2 mol L −1 , 0.4 mol L −1 , and 0.8 mol L −1 , respectively. For the acid-treated groups, with increasing acidity, P-wave velocity decreased significantly, compressive strength decreased and effective porosity increased; these behaviours are different from those of the water-treat group, implying that the acid solutions damaged the microstructure of the sandstone. The results suggest that the deterioration risk of H 2 SO 4 and HNO 3 , or sulfates and nitrates converted from ambient SO 2 , NO x and PM 2.5 , on the stone relics in the Yungang Grottoes should be a cause for concern.

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UV absorption is one of the important properties of chromophoric dissolved organic matter (CDOM). The UV absorption spectral characteristics of dissolved organic matter (DOM) were analyzed to infer the main components in Taiyuan urban section. Based on the UV absorption spectral characteristics of the CDOM, and relationship between DOC concentration and UV absorbance, conclusions were drawn: (1) Content of DOM in the treated section was at a low degree and constituent.The anthropogenic pollution accounted for a major role. (2)DOM constituents in Taiyuan section in May, July and November were relatively simple. The molecular structure of mainly CDOM was simple with mostly two or three species among the hydroxyl, carboxyl and phenyl. However, DOM constituent in September was more complicated, there were more non-fluorescent substances besides CDOM.