[Water Quality and Three-Dimensional Fluorescence of Stormwater Runoff from Lined Bioretention Field Cells].

Bioretention cells have become one of the most popular devices in urban stormwater runoff management for their high efficiency in reducing runoff volume and pollution loads. However, bioretention cells are unstable in nutrient pollutant removal, as is verified by many cases, especially at low temperatures. Dissolved organic matters (DOMs) plays an important role in denitrification, but the three-dimensional fluorescence characteristics of stormwater runoff in bioretention field cells are poorly understood, so to improve the performance of bioretention cells in nutrient pollutants control, the authors determined that it was necessary to clarify the characteristics of three-dimensional fluorescence of stormwater runoff from bioretention cells and explain their relationship to water quality. To be applicable to urban landuse in mountainous cities, two field lined bioretention cells were constructed, and, from March to April in 2017, while temperatures were still low, water quality and three-dimensional fluorescence of stormwater runoff were analyzed during low rainfall intensity precipitation events. Analysis results showed that the effluent pollutant concentrations had low fluctuation after purification by the bioretention cells, and both cells showed relatively stable removal rates for NH4+-N and total phosphorus (TP; i. e., 78.38%-95.03% and 72.04%-76.04%, respectively). Analysis of fluorescence spectra showed that the DOMs in the runoff from the two cells was mostly made up of protein and humic substances, mainly of biological origin or aquatic bacterial metabolites. Both cells performed well in the removal of protein at I, protein at Ⅱ and fulvic acid (i. e., the removal rates could reach 57.33%-61.30%, 29.82%-31.28%, and 35.55%-43.16% respectively). Correlation analyses between water quality and DOM showed that total Nitrogen (TN), TP and total organic carbon (TOC) were positively correlated with the protein content in runoff from the biorentention cells, while NO3--N and NH4+-N were negatively correlated with protein content. Meanwhile, TN was negatively correlated with DOMs in regions Ⅳ and Ⅴ of the cells.

[Influence of Reaction Time on Titanate Nanomaterials and Its Adsorptioi Capability for Lead in Aqueous Solutions].

Titanate nanomaterials (TNs) were synthesized via a simple hydrothermal method using TiO2 (ST-01) and NaOH as the raw materials, and presented different morphologies by adjusting the reaction time. The physico-chemical properties of the as-prepared TNs, such as morphology, structure, surface area, and chemical composition were characterized by XRD, SEM and BET. The adsorption capability and rules of Pb(II) in aqueous solutions were tested in the static system. The results showed that the TNs prepared with 12-72 h reaction time were pure monoclinic phase titanate and their specific surface areas were in the range from 243.05 m2 x g(-1) to 286.20 m2 x g(-1). TNs with reaction time between 12-36 h mainly showed sheet structure, and those with reaction time higher than 48 h showed linear structure. The adsorption capacity of Pb(II) by TNs-12, TNs-24, TNs-36, TNs-48, TNs-60 and TNs-72 was 479.40, 504.12, 482.00, 388.10, 364.60 and 399.00 mg x g(-1), respectively. The sheet TNs had a better adsorption capacity than the linear TNs. TNs-24 had the highest adsorbing capacity. The adsorption kinetics of Pb(II) by TNs-24 followed the pseudo-second-order model, and the equilibrium data was best fitted with the Langmuir isotherm model. The equilibrium adsorption time of TNs-24 was 120 min, and the adsorption was an exothermic process, with a high adsorption capacity at low temperature or room temperature; the optimal adsorption pH was 5.0. When pH was 1.0, the desorption rate of TNs-24 could reach 99.00%, and the removal efficiency of Pb(II) by regenerated TNs was still more than 97% after six times of usage. Therefore, TNs could efficiently remove Pb(II) in aqueous solutions, and the optimal reaction time should be controlled to 12-24 h. When Cd(II) or Ni(II) existed in the solution, the equilibrium adsorption capacity and removal rate of TNs-24 were decreased. The adsorption mechanism was mainly ion-exchanged between Pb(II) and H+/Na+ in TNs.