一种pH荧光特性物质的合成及其特性研究

合成并表征了化合物:N,N'-二苯丙氨酸铵-3,4,9,10-苝四羧酸二酰亚胺(PDCDA).研究了pH值变化对其水溶液可见吸收光谱和荧光发射光谱的影响,探讨了荧光强度变化的机理,并利用PDCDA构建了具有“开-关”特性的pH荧光传感器.结果表明,PDCDA化合物水溶性好、荧光量子产率高,荧光强度与pH值间有着强烈的依赖关系,在碱性及中性溶液中荧光强度较强且稳定,而在酸性溶液中荧光被淬灭,PDCDA在一个非常窄的pH范围内荧光强度发生了明显的变化, pH值的改变对发光团π-π堆积产生影响进而导致其荧光发射光谱和可见吸收光谱发生改变.PDCDA可用作水溶液的pH荧光传感器,检测pH值范围为3.8~6.3.     

我国电解锰行业氨氮污染分析与控制

我国"十二五"期间将氨氮纳入总量控制指标,电解锰行业氨氮污染控制变得非常紧迫。介绍了电解锰氨氮污染的现状,分析了电解锰氨氮污染的产生途径以及电解锰生产中的氨氮平衡,依据"源头消减、过程控制、末端循环"的清洁生产理念,提出了电解锰氨氮污染的控制措施。     

Validation of liquid nitrogen vaporisation rate by small scale experiments and analysis of the conductive heat flux from the concrete

The vaporisation of a liquid nitrogen pool spilled on concrete ground was investigated in small scale field experiments. The pool vaporisation rate and the heat transfer from the concrete ground were measured using a balance and a set of embedded heat flux sensors and thermocouples. The ability to predict the concrete's thermal properties based on these measurements was investigated. This work showed that a simple, one-dimensional theoretical model, assuming heat conduction through a semi-infinite ground with ideal contact between the cryogenic liquid and the ground, commonly used to describe the heat transfer from a ground to the LNG, can be used to match the observed vaporisation rate. Though estimated parameters, thermal conductivity and thermal diffusivity, do not necessary represent real values. Although the observed vaporization rate follows a linear trend, and thus can be well represented by the model, the overall model prediction seems to be overestimated. The temperature profile inside the concrete is slightly over-predicted at the beginning and under-predicted at later stage of the spill. This might be an effect of the dependence of the concrete's thermal properties on the temperature or may indicate an incorrect modelling and a varying temperature of the ground surface.     

Nitrogen budget and its environmental loading in an urban ecosystem with the rapid urbanisation of China

A detailed nitrogen (N) budget has been developed for an urban ecosystem based on the method of material flow analysis. How increased human activity and urbanisation influences N cycling have also been analysed. Total N input and output in the urban ecosystem of Zhengzhou City (ZUE) was calculated at 304.8?Gg was 275.3?Gg year^?1, resulting in an N accumulation of 29.5?Gg year^?1. Industry and human life activities, which respectively accounted for 43.8% and 34.2% of total N inputs and 52.6% and 29.1% of total N outputs, were the core of N flow in the urban ecosystem. Humans activities mediated more than 98% N inputs into the ZUE, 73.2% of N was released into the atmosphere and 11.7% into hydrosphere. This very large volume of released N could contribute to regional problems. High energy consumption, insufficient wastewater treatment facility practices, and low N use efficiency are the primary causes of pollution. The major challenge ahead for the urban ecosystem is how to manage high-intensity N pollutant inputs to the urban ecosystems coupled with incomplete N cycling and removal. Based on the analysis of the N budget and loading, this study also proposes an N management strategy for the ZUE.     

Effects of different mowing frequencies on soil carbon and nitrogen changes in leymus chinensis steppe of Hulun Buir北大核心CSCD

Mowing is the main management of Hulun Buir grasslands in Inner Mongolia; therefore, understanding the changes of soil organic carbon (SOC), total nitrogen (TN), and carbon sequestration under different mowing frequencies will provide an important scientific basis for grassland carbon sink management in Inner Mongolia. Three treatment plots were devised in the study area, including enclosed sample (Y), mowing every other year (2G), and mowing once a year (1G), where SOC, TN content and storage were investigated. The results showed that with increased mowing frequency, the SOC and TN content showed a decreasing trend in the 0-30 cm depth soil layer. The SOC and TN content were different in each soil layer, which decreased gradually with increasing soil depth in Y and 2G plots, whereas increased gradually in 1G plots. The soil carbon storage was significantly correlated with the soil nitrogen storage, and both showed a significant linear decrease with increased mowing frequency, which showed as carbon and nitrogen loss. In 2G plots, the soil carbon storage decreased by 17.1% and soil nitrogen storage decreased by 20.8%. In 1G plots, the soil carbon storage decreased by 21.6% and soil nitrogen storage decreased by 29.3%. The results showed that the change of soil carbon and nitrogen was sensitive to mowing frequency for the Hulun Buir grassland. It is possible to reduce the loss of carbon and nitrogen by reasonably controlling mowing frequency, and the sustainable use of grassland could be achieved with appropriate fertilization. Keywords. © 2018 Science Press. All rights reserved.     

吸收液对中空纤维膜接触器回收尿液中氨氮的影响

采用中空纤维膜接触器（Hollow Fiber Membrane Contactor, HFMC）回收尿液中的氨氮,系统研究了吸收液类型（H₃PO₄、H₂SO₄和HNO₃）对氨回收效能、水蒸气的跨膜通量和所获液体肥料的影响.结果表明,使用H₂SO₄作为吸收液时氨氮回收效能最优,其次是H₃PO₄和HNO₃.当采用H₂SO₄为吸收液时,氨氮回收率、氨跨膜通量和传质系数分别为84.49%±0.01%、22.92 g·m^-2·h^-1和2.37×10^-6 m·s^-1.HNO₃的挥发性使其从吸收液侧反向跨膜至料液侧,导致氨跨膜传质驱动力变小;此外,NH₃和HNO₃会在膜孔中反应并生成NH₄NO₃气溶胶,增加氨在膜孔中的传质阻力,导致氨氮的回收效能降低.对采用不同吸收液时膜两侧的水的活度差和理论水通量进行了计算,结果表明,随着氨氮的不断跨膜吸收,膜两侧的活度差和水通量逐渐增大,实验结束时水通量分别为7.44×10^-2 kg·m^-2·h^-1（H₃PO₄）、9.06×10^-2 kg·m^-2·h^-1（H₂SO₄）和2.00×10^-2 kg·m^-2·h^-1（HNO₃）.肥料组分分析表明,以H₂SO₄和HNO₃为吸收液可以获得仅含N素的单一液体肥料,以H₃PO₄作吸收液可获得N-P复合肥,（NH₄）₂HPO₄和NH₄H₂PO₄所占的比例分别为88.33%和11.67%.     

潮白河再生水生态补给河道区浅层地下水氮转化

再生水与天然地下水水质存在差异,利用再生水生态补给河道区可能会带来环境风险.引温济潮工程已运行10余年,为研究再生水长期河道入渗下不同位置地下水氮组分的演化特征与机制,收集近11年的地表水与地下水监测资料.采用聚类分析将地表水划分为不同区域后选择典型地下水监测点分析氮组分的演化差异,并利用Cl-计算混合比得出地下水中目标成分的计算浓度,初步推测地表水入渗后发生的氮转化,并选取DO、TOC、底泥、水文地质条件等环境指标分析证明.结果表明:①地表水明显分为3组,包括减河、土坝以北潮白河段、土坝以南潮白河段,各组间指标存在显著差异,影响水质差异的主要因素为再生水的氮、磷含量及水体流态.②再生水入渗过程中,包气带或黏土层较厚有利于氮的去除,减河和土坝以北潮白河段地表水中的NO₃--N流经包气带时通过反硝化与同化作用衰减,NH₄+-N通过吸附与硝化作用得以去除,入渗后未引起地下水中的氮浓度明显增加.③而土坝以南潮白河段,河道补水后翌年地下水位抬升并趋于稳定,长期地表水入渗使底泥的氮和有机质含量升高,使得该断面于2013年后达到适宜的碳氮比而发生有机氮矿化作用,由于包气带较薄,生成的NH₄+-N较少吸附于土壤介质中,易随水流入渗而引起地下水中ρ（NH₄+-N）升高.研究显示,再生水入渗过程中,包气带或黏土层较厚可有效去除氮组分,但部分地区包气带较薄且发生有机氮矿化作用会增加地下水的氮污染风险.      

沱江流域总氮面源污染负荷时空演变

根据四川省沱江流域水环境受总氮（TN）面源严重污染的现状,采用排污系数法估算2007~2017年该流域来自各面源污染源的TN污染负荷,并利用空间重心统计法和空间分析技术揭示沱江流域TN污染负荷时空分布特征及转移趋势,以期为相关部门精准防控和预警沱江流域面源污染提供理论依据.结果表明,2007~2017年畜禽养殖污染源对整个流域的TN污染负荷贡献率每年均在45%以上,是TN面源污染的主要污染源.农村生活和农村生活垃圾污染源的贡献率呈逐年减少趋势,农田固废和农田径流污染源的贡献率则呈增加趋势.TN总污染负荷总体呈下降趋势,2010年污染负荷最大,达到5.7×10⁴ t,2017年最小,为4.69×10⁴ t.污染负荷在空间上的异质性变化及降雨径流的不均匀分布驱使畜禽养殖、农田固废类和农田径流污染源的TN污染负荷重心由西北向东南方向移动,流域东南部是畜禽养殖、农田固废类和农田径流TN污染的重点防控区域.东南部各区县的农业人口大量向城市人口转化,进而驱动农村生活和农村生活垃圾污染源的TN污染负荷重心由东南向西北方向转移,其转移范围高达66.35 km²,由此确定的最小边界圆是污染源污染负荷变化的重点识别区域,沱江流域西北部则是农村生活和农村生活垃圾TN污染的重点防控区域.本研究拓展了环境科学领域对流域污染负荷时空演变的探究方法,对于改善水环境质量,促进流域经济可持续发展具有重要意义.     

白洋淀夏季入淀区沉积物间隙水-上覆水水质特征及交换通量分析

为揭示白洋淀夏季入淀区上覆水-间隙水氮磷营养盐相互作用,本研究于2019年7月对白洋淀主要6条入淀河流取样,通过分析上覆水、间隙水水质特征以及营养盐在沉积物-水界面的扩散通量,评估了营养盐扩散对沉积物与上覆水的影响.结果表明白洋淀水质呈弱碱性;溶解氧（DO）含量较低,为沉积物内源污染物的释放提供了厌氧环境;氨氮（NH₄⁺-N）浓度在0.35~1.76mg·L^-1,作为主要给水来源的潴龙河淀区最高;硝氮（NO₃^--N）浓度在0.75~1.97mg·L^-1;溶解性总氮（TDN）浓度在0.99~2.70mg·L^-1,位于自然区的S2瀑河含量最高;溶解性总磷（TDP）浓度在0.03~0.15mg·L^-1,靠近居民区的白沟引河含量最高.间隙水氨氮浓度在5.24~10.64mg·L^-1,是上覆水体的10倍,内源污染严重;硝氮浓度在0.36~0.79mg·L^-1;溶解性总氮浓度在5.36~12.02mg·L^-1,是上覆水体的5倍;溶解性总磷浓度在0.03~0.3mg·L^-1.应用综合污染指数法对水质进行评价发现间隙水污染程度远高于上覆水,各采样点呈现出严重污染状态.对NH₄⁺-N、TDN和TDP进行交换通量分析显示,NH₄⁺-N的扩散通量在1.71~7.43mg·（m²·d）^-1,作为保定市纳污河流的府河采样点内源氨氮向上覆水扩散速率最快;TDN的扩散通量除白沟引河较低,其余5个采样点均值达到9.11mg·（m²·d）^-1,夏季水体中溶解氧含量较低且沉积物-水界面TDN浓度差较大,导致沉积物中含氮营养盐在厌氧条件下大量释放到上覆水中,对水质造成严重污染;萍河采样点TDP的扩散通量是负值表示上覆水体的磷污染物向沉积物聚集的状态,剩余5个采样点的扩散通量范围在0.03~0.16mg·（m²·d）^-1,表现出磷营养盐向上覆水释放的状态.扩散通量显示内源污染物是上覆水污染物的重要来源,为有效治理入淀区水质,沉积物氮磷营养盐的清淤处理迫在眉睫.     

低温驯化对自养脱氮颗粒污泥功能活性与菌群结构的影响分析

低温驯化是提高部分亚硝化-厌氧氨氧化（PN/A）组合工艺低温脱氮效能和运行稳定性的有效方法.为探究低温驯化对污泥特性的具体影响,本文从温度敏感性、颗粒外观形态、胞外聚合物（EPS）组成和微生物群落结构等方面,对中高温培养（30℃）和低温驯化（15℃）PN/A颗粒污泥之间的差异性进行了分析.反应热力学的研究结果表明,驯化污泥（G_L）在低温区（10~20℃）的脱氮性能较中高温培养污泥（G_H）有了显著提高,总无机氮去除的表观反应活化能（E_a）降低了28.4%.与G_H相比,G_L的平均粒径减小了25.8%,EPS含量增长了16.6%,颗粒的沉降性能明显下降.由高通量测序结果可知,G_L具有更高的菌群多样性,同时,污泥中好氧氨氧化菌（Nitrosomonas）与厌氧氨氧化菌（Candidatus_Kuenenia）的丰度比值（0.04）远小于G_H的0.34.这意味着颗粒污泥在低温环境中对慢速生长自养菌仍具有较强的截留能力.上述发现为解析PN/A污泥在低温条件下的自适应机制,推动组合工艺的工程化应用提供了重要参考.