重庆市主城区大气中NO2浓度时空分布特征

利用2017年1月1日～2017年12月31日重庆市主城区17个国控空气质量监测站24 h自动连续采样的二氧化氮(NO_2)浓度小时数据,探讨九个主城区大气中NO_2浓度的时空分布特征、与气象参数之间的关系和气团运动的影响。结果表明,主城区大气NO_2浓度全年北碚区达标率较高(76.16%),渝中区达标率低(3.84%),日均浓度呈夏季前下降、夏季后上升的趋势;月均浓度表现为冬季月份浓度高,其次为春季、秋季和夏季月份;周六、周日、周一和周二的浓度均值较高,周三、周四和周五的较低;小时浓度基本呈5:00～11:00和16:00～20:00上升、其余时间段下降的变化趋势;大气NO_2浓度空间分布差异显著,西北地区(北碚)大气NO_2浓度偏低、渝中区及其附近区域浓度偏高。影响大气中的NO_2浓度的主要气象因素有:气温、降水量、气压、日照和相对湿度;四季气流输送中,春冬季气流轨迹相似,主要源自西部、西北部气流,春季气流轨迹的ρ(NO_2)最高,夏季最低。研究结果可为今后重庆市大气的治理提供研究基础。     

2005~2016年中国大气边界层SO2的时空变化趋势

利用臭氧观测仪（OMI）卫星遥感反演的大气边界层（PBL）SO₂柱含量（PBL SO₂）数据分析了自2005年以来中国PBL SO₂柱含量数据的空间分布特征、变化趋势及其影响的原因.从长时间尺度上,PBL SO₂柱含量呈现明显的下降趋势.2005年中国区域年平均PBL SO₂柱含量为0.317DU,2016年为0.276DU,减少了0.041DU,大约为13.2%.SO₂柱含量呈现明显的周期变化特征.冬季浓度较高,夏季较低,最小值和最大值分别出现在7和12月,分别为0.246和0.404DU.小波分析显示SO₂的变化在10个月的尺度水平上存在明显的主振荡周期,在40个月的尺度水平上存在明显的次周期变化.中国区域SO₂污染严重的高值区主要出现在京津冀鲁环渤海地区、关中平原（山西省和陕西省）、河南省大部分地区、四川盆地、长江三角洲地区和珠江三角洲.最大的SO₂柱含量值可达1.1DU以上.京津冀鲁环渤海地区的高值区已经延伸到长江三角洲地区,有向南延伸和珠江三角洲连在一起的趋势.由于地形和天气特征的影响,四川盆地地区SO₂出现次高值区.在青藏高原和西北地区,SO₂浓度较低,呈现背景值特征,多年平均的SO₂约在0.05DU的水平.中国区域SO₂变化趋势在空间分布上存在明显的区域差异,变化的范围在-0.70~0.15DU之间.SO₂出现逐渐减少的地区主要是在高值区,如京津冀鲁环勃海地区、关中平原、四川盆地,长江中下游和珠江三角洲.减幅最大的是四川盆地和珠江三角洲,大约减少了61%.四川盆地2005~2016年约减少了0.55DU;珠江三角洲约减少了0.45DU.出现增长的地区主要是西部和北部地区,以及东南沿海除珠三角外的大部分区域,最大增长大约为0.15DU.     

酰胺基两性分子对二硫化钨吸附铀容量的影响机制

含铀废水中铀的回收主要是基于材料与[UO₂(H₂O)₅]²⁺中UO₂ ²⁺之间的络合,但H₂O的电偶极矩对络合有显著弱化作用。采用酰胺基两性分子N,N-二甲基-9-癸烯酰胺（NADA）氢键作用与[UO₂(H₂O)₅]²⁺形成UO₂[(H₂O)_xC₁₂H₂₃NO]_n ^*（x<5,UO₂-Coordination Compound,简称UO₂-CC）,选取惰性物质WS₂为吸附材料,通过静态吸附试验（不同pH、接触时间、浓度和温度）分别研究其对UO₂ ²⁺和UO₂-CC的吸附量。动力学拟合结果表明,二者的吸附反应是化学吸附过程,UO₂ ²⁺经NADA重构后,吸附时间从240 min缩短至180 min,准二级动力学吸附常数提高1.35倍。等温吸附研究结果表明,WS₂与UO₂-CC络合过程符合Langmuir吸附等温模型,且NADA的加入使吸附由自发吸热过程转变为自发放热过程,吸附反应过程有序度增加。NADA原位重构[UO₂(H₂O)₅]²⁺后,WS₂对UO₂ ²⁺的平衡吸附量由45.03 mg/g（WS₂/UO₂ ²⁺体系）提高到122.14 mg/g（WS₂/UO₂-CC体系）。采用光谱分析（X射线光电子能谱法）从分子水平深入研究NADA原位重构[UO₂(H₂O)₅]²⁺后在WS₂上的吸附机制,揭示静电、氢键和U—S共价键等作用力对吸附的贡献,特别是NADA的氢键作用。

     

纳米二氧化钛与磷互作对莱茵衣藻砷累积与生物转化的影响

纳米材料因其较大的比表面积以及较强的反应活性,对砷（As）的环境行为具有一定的调控作用,而这可能对微藻As吸收代谢产生潜在的影响。以模式生物莱茵衣藻（Chlamydomonas reinhardtii）为研究对象,探究不同磷酸盐（PO₄ ³⁻）浓度下,纳米二氧化钛（nano-TiO₂）对莱茵衣藻中As(Ⅴ)累积和生物转化的影响。结果表明：暴露初期（第1天）nano-TiO₂作为载体显著促进了0.013、0.100和0.500 mmol/L PO₄ ³⁻处理组藻细胞对As的累积,但随着暴露时间的延长,nano-TiO₂的载体效应呈下降趋势;暴露结束后（第8天）,nano-TiO₂添加组中,进入藻细胞的As(Ⅴ)除了还原成As(Ⅲ)及甲基化成二甲基砷外,还能进一步转化为一种可能为砷糖的未知化合物,且随着PO₄ ³⁻浓度的降低,藻细胞内这种砷糖所占比例逐渐增加,这可能会抑制As(Ⅲ)的外排;暴露结束后（第8天）,培养基中主要检测到的As形态为As(Ⅴ)和As(Ⅲ),1.0和0.5 mmol/L处理组还有少量二甲基砷。nano-TiO₂的添加降低了培养基中As(Ⅲ)的浓度,尤其是0.5和1.0 mmol/L PO₄ ³⁻处理组。研究结果表明,纳米材料与PO₄ ³⁻的互作可显著改变微藻As的累积与代谢过程。

     

Enhanced cyanogen chloride formation after UV/PS and UV/H2O2 pre-oxidation and chlorination in natural river water

Ultraviolet/persulfate (UV/PS) and Ultraviolet/hydrogen peroxide (UV/H₂O₂) have attracted much attention in recent years as advanced oxidation processes for water treatment. However, it is not all clear how these two methods affect the formation of cyanogen chloride (CNCl) in the subsequent water chlorination process. In this study, it was found that both UV/H₂O₂ and UV/PS pre-oxidation promoted the formation of CNCl in six actual water samples collected from urban rivers. Glycine, uric acid, arginine and histidine were investigated as the model compounds to explore the effects of different methods on the production of CNCl. The results showed that compared with chlorination alone, pre-oxidation by UV/H₂O₂ and UV/PS can reduce the production of CNCl for glycine and uric acid by up to 95% during post-chlorination process. However, they can greatly promote the formation of CNCl for arginine and histidine by up to 120-fold. In a more detailed investigation, pre-oxidation of histidine formed highly reactive intermediates to chlorine, leading to increased CNCl formation and chlorine consumption. The results showed that the precursors of CNCl was altered after pre-oxidation, and need to be re-evaluated.     

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO2 reduction: A review

Photocatalytic CO₂ reduction is an appealing strategy for mitigating the environmental effects of greenhouse gases while simultaneously producing valuable carbon-neutral fuels. Numerous attempts have been made to produce effective and efficient photocatalysts for CO₂ reduction. In contrast, the selection of competitive catalysts continues to be a substantial hindrance and a considerable difficulty in the development of photocatalytic CO₂ reduction. It is vital to emphasize different techniques for building effective photocatalysts to improve CO₂ reduction performance in order to achieve a long-term sustainability. Metal-organic frameworks (MOFs) are recently emerging as a new type of photocatalysts for CO₂ reduction due to their excellent CO₂ adsorption capability and unique structural characteristics. This review examines the most recent breakthroughs in various techniques for modifying MOFs in order to improve their efficiency of photocatalytic CO₂ reduction. The advantages of MOFs using as photocatalysts are summarized, followed by different methods for enhancing their effectiveness for photocatalytic CO₂ reduction via partial ion exchange of metal clusters, design of bimetal clusters, the modification of organic linkers, and the embedding of metal complexes. For integrating MOFs with semiconductors, metallic nanoparticles (NPs), and other materials, a number of different approaches have been also reviewed. The final section of this review discusses the existing challenges and future prospects of MOFs as photocatalysts for CO₂ reduction. Hopefully, this review can stimulate intensive research on the rational design and development of more effective MOF-based photocatalysts for visible-light driven CO₂ conversion.     

Heterojunctioned CuO/Cu2O catalyst for highly efficient ozone removal

In recent years, near surface ozone pollution, has attracted more and more attention, which necessitates the development of high efficient and low cost catalysts. In this work, CuO/Cu₂O heterojunctioned catalyst is fabricated by heating Cu₂O at high temperature, and is adopted as ozone decomposition catalyst. The results show that after Cu₂O is heated at 180°C conversion of ozone increases from 75.2% to 89.3% at mass space velocity 1,920,000 cm³/(g·hr) in dry air with 1000 ppmV ozone, which indicates that this heterojunction catalyst is one of the most efficient catalysts reported at present. Catalysts are characterized by electron paramagnetic resonance spectroscopy and ultraviolet photoelectron spectroscopy, which confirmed that the heterojunction promotes the electron transfer in the catalytic process and creates more defects and oxygen vacancies in the CuO/Cu₂O interfaces. This procedure of manufacturing heterostructures would also be applicable to other metal oxide catalysts, and it is expected to be more widely applied to the synthesis of high-efficiency heterostructured catalysts in the future.     

基于地统计模型的上海大气污染物多建模方法的比较

地统计模型被广泛应用于环境空气污染物暴露模拟,但不同建模方法及其模拟结果之间的对比研究较少.基于上海2016~2019年55个环境空气监测点位的NO₂和PM_2.5观测数据,以及交通路网、排放源兴趣点和卫星数据等地统计变量,应用偏最小二乘回归（PLS）、监督学习线性回归（SLR）和机器学习随机森林（RF）这3种建模方法创建年暴露模型,并进一步应用普通克里金插值（OK）法分析模型残差,构建复合模型.应用交叉验证对模型的模拟效果进行检验,选取每一种建模方法的最优模型结构（是否应用OK）作为最终模型.结果表明,NO₂模型中表现最好的是RF-OK （R_mse²为0.70~0.82）和PLS-OK模型（R_mse²为0.78~0.84）;PM_2.5模型中PLS模型（R_mse²为0.62~0.71）优于SLR-OK （R_mse²为0.40~0.79）和RF-OK （R_mse²：0.31~0.56）模型.应用3种建模方法对上海1 km网格开展年暴露模拟和对比,NO₂模型间模拟结果的相关性（r为0.82~0.91）高于PM_2.5模拟结果的相关性（r为0.66~0.96）.基于3种模型2019年的模拟结果,评估了上海NO₂和PM_2.5的人群暴露水平.     

中国水泥行业通过CCUS技术的减排潜力评估

中国水泥行业面临巨大的碳达峰与碳中和压力.CO₂捕集利用与封存（CCUS）技术是能够实现化石资源低碳利用的碳减排技术.在中国水泥企业数据基础上,采用全流程CCUS系统模型（ITEAM-CCUS）评估CCUS的碳减排潜力对水泥企业碳中和非常重要.模型从源汇匹配距离、捕集率、CCUS技术和技术水平这4个方面设置了10种情景,完成了水泥行业的企业筛选、场地筛选、CCUS技术经济评估和源汇匹配,初步回答了水泥企业结合CCUS的封存场地、减排规模、成本范围和优先项目分布等关键问题.在250 km匹配距离、85%净捕集率、CO₂-EWR技术和当前技术水平情景,44%的水泥企业可以利用CO₂强化地下水开采（CO₂-EWR）技术开展碳减排,累计年碳减排量为6.25亿t,平准化成本为290~1838元·t^-1;具有全流程CO₂-EWR早期示范优势的地区为新疆、内蒙古、宁夏、河南和河北等.水泥企业开展全流程CCUS项目技术可行,可以实现大规模CO₂减排,低成本项目具有早期示范机会.研究结果可为水泥行业低碳发展和CCUS商业化部署提供定量参考.     

Anoxic phosphorus removal in a pilot scale anaerobic-anoxic oxidation ditch process

The anaerobic-anoxic oxidation ditch (A²/O OD) process is popularly used to eliminate nutrients from domestic wastewater. In order to identify the existence of denitrifying phosphorus removing bacteria (DPB), evaluate the contribution of DPB to biological nutrient removal, and enhance the denitrifying phosphorus removal in the A²/O OD process, a pilot-scale A²/O OD plant (375 L) was conducted. At the same time batch tests using sequence batch reactors (12 L and 4 L) were operated to reveal the significance of anoxic phosphorus removal. The results indicated that: The average removal efficiency of COD, NH₄⁺, PO₄³⁻, and TN were 88.2%, 92.6%, 87.8%, and 73.1%, respectively, when the steady state of the pilotscale A²/O OD plant was reached during 31–73 d, demonstrating a good denitrifying phosphorus removal performance. Phosphorus uptake took place in the anoxic zone by poly-phosphorus accumulating organisms NO₂⁻ could be used as electron receptors in denitrifying phosphorus removal, and the phosphorus uptake rate with NO₂⁻ as the electron receptor was higher than that with NO₃⁻ when the initial concentration of either NO₂⁻ or NO₃⁻ was 40 mg/L.