洱海大气氮素湿沉降特征

通过对2020年位于洱海湖区周边4个站点大气降水的实地监测，定量揭示了大气湿沉降不同形态氮素（TN、DTN、AN、NN、NIT、PN）的浓度和时空分布规律，探讨了氮素沉降通量的变化特征及其主要影响因子，进而明确了大气氮湿沉降对湖区外源性氮素输入的贡献程度，评估了氮素湿沉降入湖负荷对湖区水环境的影响。结果表明：各监测点降水中氮素浓度年内总体呈先升后降再升的趋势，总氮浓度为0.18～8.73 mg/L，平均浓度为1.34±0.686 mg/L，氮素浓度呈现干季高湿季低的变化规律；氮素湿沉降通量月际变化大致呈M双峰型，沉降通量峰值出现在浓度最低但降雨量最大的8月，最小值出现在12月，沉降通量与降雨量呈极显著正相关，沉降通量AN/NN为1.97，农业生产活动的氮素排放是湿沉降的主要来源；2020年洱海湖面湿沉降总氮直接输入负荷量约为170.11 t，其中铵态氮86.86 t，硝态氮51.58 t，总氮直接入湖负荷约占流域农业面源排放量的6.18%。     

森林地区持久性有机污染物的沉降和释放

持久性有机污染物（POPs）是一类具有毒性、难降解性和生物富集性的污染物。由于具有半挥发性，POPs可以随大气进行长距离传输并富集到极地等寒冷的偏远地区。大气沉降和挥发是POPs全球传输的关键过程。森林是POPs的重要储库，其POPs的强吸收能力加速了POPs的沉降，使得森林成为POPs大气沉降研究的重要介质。本文综述了当前森林POPs沉降研究的主要成果，重点阐述了大气POPs向植被（树冠）沉降和植被POPs向林下土壤迁移沉降这两大关键过程的特征和机制，并简要总结了林下POPs的后沉降过程（循环及再释放）和机制。最后，提出森林POPs沉降研究应着眼于观测技术开发、微观机制解析、关键规律总结、释放特征观测和多污染物耦合等方向，进而拓展大气污染物干湿沉降研究范围、丰富大气污染物干湿沉降研究的理论和方法，力争为气候变化背景下污染防治提供科学依据和理论支撑。     

Use of catalytic wet air oxidation (CWAO) for pretreatment of high-salinity high-organic wastewater

Catalytic wet air oxidation (CWAO) coupled desalination technology provides a possibility for the effective and economic degradation of high salinity and high organic wastewater. Chloride widely occurs in natural and wastewaters, and its high content jeopardizes the efficacy of Advanced oxidation process (AOPs). Thus, a novel chlorine ion resistant catalyst B-site Ru doped LaFe_1-xRu_xO_3-δ in CWAO treatment of chlorine ion wastewater was examined. Especially, LaFe_0.85Ru_0.15O_3-δ was 45.5% better than that of the 6%RuO₂@TiO₂ (commercial carrier) on total organic carbon (TOC) removal. Also, doped catalysts LaFe_1-xRu_xO_3-δ showed better activity than supported catalysts RuO₂@LaFeO₃ and RuO₂@TiO₂ with the same Ru content. Moreover, LaFe_0.85Ru_0.15O_3-δ has novel chlorine ion resistance no matter the concentration of Cl⁻ and no Ru dissolves after the reaction. X-ray diffraction (XRD) refinement, X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and X-ray absorption fine structure (XAFS) measurements verified the structure of LaFe_0.85Ru_0.15O_3-δ. Kinetic data and density functional theory (DFT) proved that Fe is the site of acetic acid oxidation and adsorption of chloride ions. The existence of Fe in LaFe_0.85Ru_0.15O_3-δ could adsorb chlorine ion (catalytic activity inhibitor), which can protect the Ru site and other active oxygen species to exert catalytic activity. This work is essential for the development of chloride-resistant catalyst in CWAO.

1. Download : Download high-res image (171KB)
2. Download : Download full-size image