To roll or not to roll: nyctinastic behavior in young leaves of sacred lotus,Nelumbo nucifera

The Science of Nature -     

基于生物膜序批式反应器工艺的城市污水磷酸盐富集实验研究

基于生物膜序批式反应器（BSBR）工艺,对模拟城市污水中的磷酸盐进行高效去除、回收.实验在探究不同蓄磷量和碳源对反应器效能、磷回收效率影响的基础上,进一步分析了两者的共同作用对厌氧释磷速率和释磷量的影响.结果表明,在反应器低碳源投加(仅厌氧投加200mg·L^-1)和低磷进水(10 mg·L^-1)工况下,磷回收液浓度随着蓄磷量增加而增大,磷回收液浓度最高可达到225.5 mg·L^-1,蓄磷量可达159.6mg·g^-1;同时探究了磷回收液浓度与平均磷回收效率间的关系,在以（6±1）d为回收周期的循环下,磷富集液浓度达到（106.6±10）mg·L^-1,此时平均磷回收效率为78.62%±2.3%;而且提高3.6倍蓄磷量可提高1.9倍释磷量,较之4倍碳源投加量时的1.79倍释磷量更为高效.因此,本反应器能基于更低碳源投加量获取高浓度磷回收液,从而为未来废水处理厂中磷的回收提供新的方向.     

中国兜兰属宽瓣亚属植物生存现状及保护成效

为明确兜兰属(Paphiopedilum)宽瓣亚属(Subgenus.Brachypetalum)植物各物种在我国的生存现状与濒危状况,在大量的野外调查和文献、标本数据收集的基础上,对其种群分布、数量、生境特征、市场贸易、受威胁因素、保护现状与保护成效进行统计分析,并依据《IUCN红色名录等级和标准(3.1版)》对该类群的濒危等级进行重新评估.结果表明,野外调查到硬叶兜兰(Paphiopedilum.micranthum)、麻栗坡兜兰(P.malipoense)、杏黄兜兰(P.armeniacum)、白花兜兰(P.emersonii)、巨瓣兜兰(P.bellatulum)、文山兜兰(P.wenshanense)、同色兜兰(P.concolor)7个目标物种,已知分布于我国50个县(市、区),共计194个自然分布点.宽瓣亚属植物在我国水平方向上主要分布于滇东南、黔西南、黔东北、滇西北、桂北与黔南交界处以及桂西北至桂西南等地区;垂直方向上集中分布于中高海拔段(780~1267m),平均海拔997m;在全国大尺度上,该亚属整体呈零散分布,区域小尺度上个体呈聚集生长;其小生境具有高海拔、透水、透气、喜阴、喜钙的特点.市场调查的贸易率为36.67%,贸易价格高低不等,具有较强的随机性;贸易来源主要为野外采挖,占贸易数量的88.32%,具有较强的地域性;贸易方式为现场和线上网络交易,具有较强的灵活性.该类群主要受到采挖和生境退化的威胁,分别占所有分布点的44.85%、29.83%.宽瓣亚属整体就地保率仅为34.53%,保护成效为一般保护;调查的29个保育地中,有20个保育地对该类群累计保育98次,除文山兜兰和绿叶兜兰外,其他7种迁地保护成效被评估为合适.巨瓣兜兰、文山兜兰由原来的濒危(EN)评估为极危(CR);麻栗坡兜兰、白花兜兰、杏黄兜兰评估等级未发生变化,仍为极危(CR);硬叶兜兰和同色兜兰由原来的易危(VU)评估为濒危(EN);德氏兜兰、绿叶兜兰被评为数据缺乏(DD).     

低NOx环境异戊二烯促进甲苯生成甲基丁烯二醛的模拟实验

在低NO_x浓度条件下开展甲苯和异戊二烯复合体系的烟雾箱模拟实验,使用高时间分辨率的在线质子转移反应飞行时间质谱(PTR-TOF-MS)实时监测混合体系中反应物与产物的浓度变化情况,探究人为源与天然源交汇过程中, 自然源挥发性有机物 (BVOCs)对人为挥发性有机物(AVOCs)化学降解的影响.结果表明,异戊二烯与甲苯竞争OH自由基,从而抑制了甲苯的化学降解,该竞争反应开始得越早,抑制效果越显著.研究还发现异戊二烯会增强甲苯RO₂降解途径产物的产量,生成更多1,4不饱和-二羰基化合物(如丁烯二醛和甲基丁烯二醛)与二羰基化合物(如乙二醛和甲基乙二醛),其中甲基丁烯二醛增量最高可达38.6%.此外,异戊二烯快速氧化生成的RO₂自由基碳数更少,可能与甲苯氧化生成的RO₂自由基发生了快速的交叉反应,有利于甲苯RO自由基的生成及裂解,最终导致甲苯RO₂途径裂解产物的增加.     

Ambient volatile organic compounds at a receptor site in the Pearl River Delta region: Variations, source apportionment and effects on ozone formation

We present the continuously measurements of volatile organic compounds（VOCs） at a receptor site（Wan Qing Sha, WQS） in the Pearl River Delta（PRD） region from September to November of 2017. The average mixing ratios of total VOCs（TVOCs） was 36.3 ± 27.9 ppbv with the dominant contribution from alkanes（55.5%）, followed by aromatics（33.3%）. The diurnal variation of TVOCs showed a strong photochemical consumption during daytime,resulting in the formation of ozone（O₃）. Five VOC sources were ...     

Hydrothermal-treated Pt/Al2O3 as an excellent catalyst for toluene total oxidation

The preparation of highly active supported noble metal catalysts with a low noble metal loading has always been the ultimate goal of researchers working on catalysis. Hydrothermally treated Pt/Al₂O₃ (Pt/Al₂O₃-H) exhibits better catalytic activity than that (Pt/Al₂O₃-C) treated via the conventional calcination approach. At the high space velocity of 100,000 mL/(g∙hr), the temperature that correspond to 50% toluene conversion (T₅₀) of Pt/Al₂O₃-H is 115°C lower than that of Pt/Al₂O₃-C, and the turnover frequency (TOF) value can reach 0.0756 sec⁻¹. The mechanism by which the hydrothermal approach enhances Pt/Al₂O₃ activity has been investigated. The structure associated with the high catalytic activity of Pt nanoparticles (NPs) can be retained via hydrothermal treatment. Furthermore, the support is transformed to AlO(OH) with numerous surface hydroxyl groups, which in turn can facilitate the adsorption of toluene. And the synergistic effects of Pt NPs and AlO(OH) increases the contents of Pt in oxidation state and active oxygen, which are beneficial for toluene oxidation.     

Impact of pre-oxidation on the formation of byproducts in algae-laden water disinfection: Insights from fluorescent and molecular weight

Pre-oxidation has been reported to be an effective way to remove algal cells in water, but the released algal organic matter (AOM) could be oxidized and lead to the increment in disinfection by-product (DBP) formation. The relationship between pre-oxidation and AOM-derived DBP formation needs to be approached more precisely. This study compared the impact of four pre-oxidants, ozone (O₃), chlorine dioxide (ClO₂), potassium permanganate (KMnO₄) and sodium hypochlorite (NaClO), on the formation of nitrogenous (N-) and carbonaceous (C-) DBPs in AOM chlorination. The characterization (fluorescent properties, molecular weight distribution and amino acids concentration) on AOM samples showed that the characterization properties variations after pre-oxidation were highly dependent on the oxidizing ability of oxidants. The disinfection experiments showed that O₃ increased DBP formation most significantly, which was consistent with the result of characterization properties variations. Then canonical correspondent analysis (CCA) and Pearson's correlation analysis were conducted based on the characterization data and DBP formation. CCA indicated that C-DBPs formation was highly dependent on fluorescent data. The formation of haloacetic acids (HAAs) had a positive correlation with aromatic protein-like component while trichloromethane (TCM) had a positive correlation with fulvic acid-like component. Pearson's correlation analysis showed that low molecular weight fractions were favorable to form N-DBPs. Therefore, characterization data could provide the advantages in the control of DBP formation, which further revealed that KMnO₄ and ClO₂ were better options for removing algal cells as well as limiting DBP formation.     

Short-term inhalation exposure evaluations of airborne antibiotic resistance genes in environments

Antibiotic resistance is a sword of Damocles that hangs over humans. In regards to airborne antibiotic resistance genes (AARGs), critical knowledge gaps still exist in the identification of hotspots and quantification of exposure levels in different environments. Here, we have studied the profiles of AARGs, mobile genetic elements (MGEs) and bacterial communities in various atmospheric environments by high throughput qPCR and 16S rRNA gene sequencing. We propose a new AARGs exposure dose calculation that uses short-term inhalation (STI). Swine farms and hospitals were high-risk areas where AARGs standardised abundance was more abundant than suburbs and urban areas. Additionally, resistance gene abundance in swine farm worker sputum was higher than that in healthy individuals in other environments. The correlation between AARGs with MGEs and bacteria was strong in suburbs but weak in livestock farms and hospitals. STI exposure analysis revealed that occupational intake of AARGs (via PM₁₀) in swine farms and hospitals were 110 and 29 times higher than in suburbs, were 1.5 × 10⁴, 5.6 × 10⁴ and 5.1 × 10² copies, i.e., 61.9%, 75.1% and 10.7% of the overall daily inhalation intake, respectively. Our study comprehensively compares environmental differences in AARGs to identify high-risk areas, and forwardly proposes the STI exposure dose of AARGs to guide risk assessment.     

Dosing low-level ferrous iron in coagulation enhances the removal of micropollutants, chlorite and chlorate during advanced water treatment

Drinking water utilities are interested in upgrading their treatment facilities to enhance micropollutant removal and byproduct control. Pre-oxidation by chlorine dioxide (ClO₂) followed by coagulation-flocculation-sedimentation and advanced oxidation processes (AOPs) is one of the promising solutions. However, the chlorite (ClO₂^–) formed from the ClO₂ pre-oxidation stage cannot be removed by the conventional coagulation process using aluminum sulfate. ClO₂^– negatively affects the post-UV/chlorine process due to its strong radical scavenging effect, and it also enhances the formation of chlorate (ClO₃^–). In this study, dosing micromolar-level ferrous iron (Fe(II)) into aluminum-based coagulants was proposed to eliminate the ClO₂^– generated from ClO₂ pre-oxidation and benefit the post-UV/chlorine process in radical production and ClO₃^– reduction. Results showed that the addition of 52.1-µmol/L FeSO₄ effectively eliminated the ClO₂^– generated from the pre-oxidation using 1.0 mg/L (14.8 µmol/L) of ClO₂. Reduction of ClO₂^– increased the degradation rate constant of a model micropollutant (carbamazepine) by 55.0% in the post-UV/chlorine process. The enhanced degradation was verified to be attributed to the increased steady-state concentrations of HO^· and ClO^· by Fe(II) addition. Moreover, Fe(II) addition also decreased the ClO₃^– formation by 53.8% in the UV/chlorine process and its impact on the formation of chloro-organic byproducts was rather minor. The findings demonstrated a promising strategy to improve the drinking water quality and safety by adding low-level Fe(II) in coagulation in an advanced drinking water treatment train.     

Chemical characterization and source identification of PM2.5 in Luoyang after the clean air actions

Luoyang is a typical heavy industrial city in China, with a coal-dominated energy structure and serious air pollution. Following the implementation of the clean air actions, the physicochemical characteristics and sources of PM_2.5 have changed. A comprehensive study of PM_2.5 was conducted from October 16, 2019 to January 23, 2020 to evaluate the effectiveness of previous control measures and further to provide theory basis for more effective policies in the future. Results showed that the aerosol pollution in Luoyang in autumn and winter is still serious with the average concentration of 91.1 μg/m³, although a large reduction (46.9%) since 2014. With the contribution of nitrate increased from 12.5% to 25.1% and sulfate decreased from 16.7% to 11.2%, aerosol pollution has changed from sulfate-dominate to nitrate-dominate. High NO₃⁻/SO₄²⁻ ratio and the increasing of NO₃⁻/SO₄²⁻ ratio with the aggravation of pollution indicating vehicle exhaust playing an increasingly important role in PM_2.5 pollution in Luoyang, especially in the haze processes. Secondary inorganic ions contributed significantly to the enhancement of PM_2.5 during the pollution period. The high value of Cl⁻/Na⁺ and EC concentration indicate coal combustion in Luoyang is still serious. The top three contributor sources were secondary inorganic aerosols (33.3%), coal combustion (13.6%), and industrial emissions (13.4%). Close-range transport from the western and northeastern directions were more important factors in air pollution in Luoyang during the sampling period. It is necessary to strengthen the control of coal combustion and reduce vehicle emissions in future policies.