交通限行对大气颗粒物及PM2.5中二NFDA1英的影响

为了研究北京大气颗粒物和二NFDA1英(PCDD/Fs)的污染状况以及评估交通限行对大气颗粒物和PCDD/Fs的影响。利用同位素稀释高分辨率气相色谱/高分辨率质谱(HRGC/HRMS)联用法和USEPA 1613B 标准方法,以中国地质大学(北京)东门为采样点,采集大气PM_2.5、PM₁₀、TSP样品,对北京市交通限行期间以及交通限行前后等不同交通状况下颗粒物浓度及大气PM_2.5中17种2,3,7,8-PCDD/Fs污染特征进行了监测。结果表明,PM_2.5、PM₁₀、TSP的日均质量浓度在交通限行前分别为126、202、304 μg/m³,限行期间分别为39、78、93 μg/m³,限行结束后分别为79、126 μg/m³。PM_2.5中17种PCDD/Fs的质量浓度(毒性浓度)3个时段分别为1 804 fg/m³(70 fg I-TEQ/m³)、252 fg/m³ (9 fg I-TEQ/m³)和1 196 fg/m³ (48 fg I-TEQ/m³)。北京市交通限行期间颗粒物浓度和二 NFDA1 英浓度显著低于交通限行前后,交通源减排措施的实施是大气颗粒物和二 NFDA1英污染水平降低的主要原因,从减排效果看,交通源减排措施对大气细颗粒物(PM_2.5)的控制效果明显好于大气粗颗粒物。     

生活垃圾与危险废物焚烧二噁英类排放特征研究

对某省52家焚烧企业(21家生活垃圾和31家危险废物)排放烟气数据进行了分析,结果表明,两类焚烧企业二噁英类17种单体分布有所不同,生活垃圾焚烧烟气中浓度较高的是O8CDD和O8CDF;危险废物焚烧烟气中较大的是2,3,4,7,8-P5CDF、2,3,7,8-T4CDD和1,2,3,7,8-P5CDD;两类焚烧企业二噁英类单体对I-TEQ贡献最高的都是2,3,4,7,8-P5CDF,贡献率分别为0. 7%～45%和10%～67%;两者的17种二噁英类与I-TEQ的相关性分析表明,1,2,3,7,8-P5CDF在2类焚烧炉中与I-TEQ均存在较高的相关性,其相关系数分别0. 932和0. 927,可以作为潜在的测定指示物。     

MoS_2/Bi_2S_3异质结光催化剂的制备及其光催化性能

以五水硝酸铋为铋源、钼酸钠为钼源、硫脲为硫源,采用简单的一步水热法合成了MoS_2/Bi_2S_3异质结光催化剂,采用XRD,SEM,TEM,BET,UV-Vis DRS技术对其进行了表征。表征结果显示,MoS_2纳米片在Bi_2S_3微棒表面生长,增加了比表面积和活性位点,并形成异质结构,促进了光生载流子的迁移,抑制了电子-空穴对的再复合。实验结果表明:钼酸钠与五水硝酸铋的质量比为1∶2时制备的复合光催化剂性能最好,反应180min时对亚甲基蓝的去除率可达96.4%,明显高于MoS_2和Bi_2S_3,且具有较高的稳定性;该催化剂对罗丹明B、甲基橙和4-硝基苯酚的去除率分别为97.1%、93.1%和90.5%,表明其对污染物具有普适性。     

萃取法分离回收不锈钢酸洗污泥硫酸浸出液中的重金属

采用非皂化P204和皂化P204萃取剂对不锈钢酸洗污泥的硫酸浸出液进行萃取。在浸出液pH为0.80、非皂化P204体积分数为25%、萃取剂与浸出液体积比为1∶2、萃取时间为5 min的条件下,Fe~(3+)萃取率达99.64%,Cr~(3+)和Ni~(2+)萃取率为3.98%和6.99%,一次萃余液pH为0.64。采用皂化P204对除Fe~(3+)后的一次萃余液进行萃取,在P204体积分数为25%、萃取剂与浸出液体积比为1∶2、萃取剂皂化率为60%、一次萃余液pH为1.50、萃取时间为5 min的条件下,Ni~(2+)萃取率为93.12%,Cr~(3+)萃取率为20.69%,二次萃余液pH为2.63。     

g-C_3N_4/C@Bi_2MoO_6复合光催化剂的制备及其光催化活性

通过水热合成法和液相沉积法制备g-C_3N_4/C@Bi_2MoO_6复合光催化剂,并采用X射线衍射、扫描电子显微镜、氮气吸脱附、紫外-可见漫反射等技术对其进行表征。研究了可见光下g-C_3N_4/C@Bi_2MoO_6催化降解罗丹明B(Rh B)的影响因素,并对其光催化反应机理进行初步探讨。实验结果表明:g-C_3N_4掺杂量为60%(w)时g-C_3N_4/C@Bi_2MoO_6的光催化活性最高;在60%g-C_3N_4/C@Bi_2MoO_6的投加量为1.00 g/L、初始Rh B质量浓度为2.50 mg/L、可见光照射150 min的条件下,Rh B的降解率达到97.90%;在g-C_3N_4/C@Bi_2MoO_6光催化降解体系中,h~+和·O_2~-是主要活性物种。     

Supporting Diverse Data Providers in the Open Water Data Initiative: Communicating Water Data Quality and Fitness of Use

Shared, trusted, timely data are essential elements for the cooperation needed to optimize economic, ecologic, and public safety concerns related to water. The Open Water Data Initiative (OWDI) will provide a fully scalable platform that can support a wide variety of data from many diverse providers. Many of these will be larger, well‐established, and trusted agencies with a history of providing well‐documented, standardized, and archive‐ready products. However, some potential partners may be smaller, distributed, and relatively unknown or untested as data providers. The data these partners will provide are valuable and can be used to fill in many data gaps, but can also be variable in quality or supplied in nonstandardized formats. They may also reflect the smaller partners' variable budgets and missions, be intermittent, or of unknown provenance. A challenge for the OWDI will be to convey the quality and the contextual “fitness” of data from providers other than the most trusted brands. This article reviews past and current methods for documenting data quality. Three case studies are provided that describe processes and pathways for effective data‐sharing and publication initiatives. They also illustrate how partners may work together to find a metadata reporting threshold that encourages participation while maintaining high data integrity. And lastly, potential governance is proposed that may assist smaller partners with short‐ and long‐term participation in the OWDI.     

Recent Changes in Stream Flashiness and Flooding,and Effects of Flood Management in North Carolina and Virginia

The southeastern United States has undergone anthropogenic changes in landscape structure, with the potential to increase (e.g., urbanization) and decrease (e.g., reservoir construction) stream flashiness and flooding. Assessment of the outcome of such change can provide insight into the efficacy of current strategies and policies to manage water resources. We (1) examined trends in precipitation, floods, and stream flashiness and (2) assessed the relative influence of land cover and flow‐regulating features (e.g., best management practices and artificial water bodies) on stream flashiness from 1991 to 2013. We found mean annual precipitation decreased, which coincided with decreasing trends in floods. In contrast, stream flashiness, overall, showed an increasing trend during the period of study. However, upon closer examination, 20 watersheds showed stable stream flashiness, whereas 5 increased and 6 decreased in flashiness. Urban watersheds were among those that increased or decreased in flashiness. Watersheds that increased in stream flashiness gained more urban cover, lost more forested cover and had fewer best management practices installed than urban watersheds that decreased in stream flashiness. We found best management practices are more effective than artificial water bodies in regulating flashy floods. Flashiness index is a valuable and straightforward metric to characterize changes in streamflow and help to assess the efficacy of management interventions.     

A study on oxidative degradation of polyacrylamide in wastewater with UV/FENTON/C4H4O62−

The degradation of polyacrylamide (PAM) in simulate wastewater was studied in UV/Fenton/C₄H₄O₆^2? system. The factors such as molecular ratio of H₂O₂/Fe²⁺/C₄H₄O₆^2?, pH, and the dosage of Fenton reagent that could affect the PAM degradation in the UV/Fenton/C₄H₄O₆^2? system were investigated. The experimental results showed that adding C₄H₄O₆^2? to UV/Fenton system could form photosensitive ferrous complexes, which led to higher degradation efficiency of PAM. The degradation rate of PAM could be up to 95.2% under the following conditions: the concentration of H₂O₂, Fe²⁺, and C₄H₄O₆^2? were 22.5, 2.25, and 2.25 mmol/L, respectively (i.e., molecular ratio of H₂O₂/Fe²⁺/C₄H₄O₆^2? was 10:1:1), the pH value was 3.0.     

Comparative study on performances of a heat-pipe PV/T system and a heat-pipe solar water heating system

The heat-pipe solar water heating (HP-SWH) system and the heat-pipe photovoltaic/thermal (HP-PV/T) system are two practical solar systems, both of which use heat pipes to transfer heat. By selecting appropriate working fluid of the heat-pipes, these systems can be used in the cold region without being frozen. However, performances of these two solar systems are different because the HP-PV/T system can simultaneously provide electricity and heat, whereas the HP-SWH system provides heat only. In order to understand these two systems, this work presents a mathematical model for each system to study their one-day and annual performances. One-day simulation results showed that the HP-SWH system obtained more thermal energy and total energy than the HP-PV/T system while the HP-PV/T system achieved higher exergy efficiency than the HP-SWH system. Annual simulation results indicated that the HP-SWH system can heat the water to the available temperature (45°C) solely by solar energy for more than 121 days per year in typical climate regions of China, Hong Kong, Lhasa, and Beijing, while the HP-PV/T system can only work for not more than 102 days. The HP-PV/T system, however, can provide an additional electricity output of 73.019 kWh/m², 129.472 kWh/m², and 90.309 kWh/m² per unit collector area in the three regions, respectively.     

Photovoltaic-thermal (PV/t) panel to minimize electrical and air conditioning energy consumption of a typical office in Beirut

A combined photovoltaic–thermal (PV/t) panel is proposed to produce simultaneously electricity and heat from one integrated unit. The unit utilizes effectively the solar energy through achieving higher PV electrical efficiency and using the thermal energy for heating applications. To predict the performance of the PV/t at a given environmental conditions, a transient mathematical model was developed. The model was integrated in a heating application for a typical office space in the city of Beirut to provide the office needs for electricity, heating during winter season, and dehumidification and evaporative cooling during the summer season. To minimize the yearly office energy (electrical and heat) needs, the PV/t panel cooling air flow rate and the dehumidification regeneration temperature were determined for opimal unit operation. Thermal energy savings of up to 85% in winter and 71% in summer were achived compared to conventional systems at a payback period of 8 years for the panels.