Donghai Yuan

Detection of dissolved organic matter in saline–alkali soils using synchronous fluorescence spectroscopy and principal component analysis

Dissolved organic matter (DOM) is attributed a key role in soil major biogeochemical processes. Its molecular characteristics can reflect both its source and its biogeochemical history. Saline-alkali soil samples were collected from a field in desert and semi-desert region. DOM was analyzed by synchronous fluorescence spectroscopy. Principal Components Analysis (PCA) of synchronous fluorescence spectra was used to detect and describe changes in the DOM in different soil profiles. The analysis of PCA yielded 2 PCs that account for 97% of the variance. DOM is characterized by a dominant tyrosine-like fluorophore in the Region I (PC1>0.9, PC2<0.3), including soils Ke02, Ke03, Ke04, Rh02, Rh03, Rh04, Sa04 and Sc04. The region II including Kf02, Sa01, Yb01, Yzd01 and Yzd02 obtain higher PC2 (>0.9) and lower PC1 (<0.3) loading, which is dominated humic-like fluorophore. Hierarchical cluster analysis (HCA) identified five main clusters. The results of hierarchical cluster analysis (HCA) were consistent with the PCA. The ratio of fluorescence intensity of humic substances at long wavelengths and short wavelengths was used to indicate the humification of organic matter. Two ratios (I(345/318) and I(362/318).) can be used to indicate the humification of DOM. The humification degree of the remaining soils has no systematic trend because of land use, agricultural irrigation, soil erosion and salinization. Soils obtained a relatively high humification degree in the region II and a relatively low humification degree in the region I.

Spectroscopic techniques for quantitative characterization of Cu (II) and Hg (II) complexation by dissolved organic matter from lake sediment in arid and semi-arid region.

Dissolved organic matter (DOM) was extracted from six sediment samples in arid and semi-arid region, which was characterized by fluorescence excitation-emission matrices (EEMs). The results showed that four fluorescent peak, fulvic-like (peak A), humic-like (peak C) and two tryptophan-like (peaks B and D), were identified in lake sediment DOM. Fluorescence quenching titration showed that peaks B and D were quenched gradually by adding additional Cu (II) and Hg (II), whereas humic-like substances had no systematic trend of the change of fluorescence intensity. Increasing fluorescence intensity value of humic-like substances can also be found. The modified Stern-Volmer model was used to calculate conditional stability constants (logK) and the percent of fluorophores (f %) which participate in the complexation between DOM and Cu (II), and Hg (II). The results showed that DOM-Cu (II) and DOM-Hg (II) complexes had higher logK values of 4.21-5.23 and the logK values of DOM-Cu (II) are much larger than the corresponding values for Hg (II). Peak B showed relatively low logK and high f % values than those of peak D. Different pollution sources which are mainly obtained from the upstream industrial wastewater, domestic sewage and return water of farmland irrigation tend to affect the stability constants and complexing capacities of Cu (II) and Hg (II).

Detection of Copper (II) and Cadmium (II) binding to dissolved organic matter from macrophyte decomposition by fluorescence excitation-emission matrix spectra combined with parallel factor analysis

Fluorescence excitation-emission matrix (EEM) spectra coupled with parallel factor analysis (PARAFAC) was used to characterize dissolved organic matter (DOM) derived from macrophyte decomposition, and to study its complexation with Cu (II) and Cd (II). Both the protein-like and the humic-like components showed a marked quenching effect by Cu (II). Negligible quenching effects were found for Cd (II) by components 1, 5 and 6. The stability constants and the fraction of the binding fluorophores for humic-like components and Cu (II) can be influenced by macrophyte decomposition of various weight gradients in aquatic plants. Macrophyte decomposition within the scope of the appropriate aquatic phytomass can maximize the stability constant of DOM-metal complexes. A large amount of organic matter was introduced into the aquatic environment by macrophyte decomposition, suggesting that the potential risk of DOM as a carrier of heavy metal contamination in macrophytic lakes should not be ignored.

Using fluorescence quenching combined with two-dimensional correlation fluorescence spectroscopy to characterise the binding-site heterogeneity of dissolved organic matter with copper and mercury in lake sediments

Environmental context Dissolved organic matter (DOM) plays an important role in influencing the migration and ultimate fate of metals. Different sources of pollution resulted in changes in the structure of sediment DOM in Lake Wuliangsuhai. We investigate the binding properties of DOM with CuII and HgII using fluorescence quenching combined with two-dimensional correlation spectroscopy (2D-COS) in order to demonstrate the influence of different sources of DOM on metals. Abstract Dissolved organic matter (DOM) was collected from three sampling sites (L1, L2 and L3) in Lake Wuliangsuhai. L1 received upstream industrial wastewater and domestic sewage. L2 had suffered from agricultural non-point source pollution. L3 was situated in the lake outlet area. The complexation of DOM with CuII and HgII was investigated based on fluorescence quenching of the synchronous fluorescence spectra on the addition of CuII and on two-dimensional correlation spectroscopy (2D-COS). The synchronous and asynchronous maps derived from 2D-COS provided a clear picture of the heterogeneous distribution of CuII and HgII binding sites, which was not readily detected using only the synchronous fluorescence spectra. CuII and HgII complexation was stronger at shorter wavelengths than at longer wavelengths. Moreover, fluorescence quenching also occurred intensely in the fulvic-like regions (363nm for DOM-Cu in L2 and 365nm for DOM-Hg in L1). The logarithms of the stability constants (log KM) ranged from 4.42 to 6.23, from 4.75 to 4.86, and from 4.80 to 5.73 for DOM-Cu in L1, L2 and L3, respectively, depending on the wavelength. DOM at the longer wavelengths exhibited a higher log KM than that at the shorter wavelengths, and the f values in the protein-like region were clearly high. These results suggest that the influence of the structural and chemical properties of DOM on CuII binding may differ for DOM from different sources. The combined approach of fluorescence quenching and 2D-COS could be applied as a tool for evaluating the metal binding site heterogeneity of DOM.

Case Study on Incentive Mechanism of Energy Efficiency Retrofit in Coal-Fueled Power Plant in China

An ordinary steam turbine retrofit project is selected as a case study; through the retrofit, the project activities will generate emission reductions within the power grid for about 92,463 tCO2e per annum. The internal rate of return (IRR) of the project is only −0.41% without the revenue of carbon credits, for example, CERs, which is much lower than the benchmark value of 8%. Only when the unit price of carbon credit reaches 125 CNY/tCO2, the IRR could reach the benchmark and an effective carbon tax needs to increase the price of carbon to 243 CNY/tce in order to make the project financially feasible. Design of incentive mechanism will help these low efficiency enterprises improve efficiency and reduce CO2 emissions, which can provide the power plants sufficient incentive to implement energy efficiency retrofit project in existing coal-fuel power generation-units, and we hope it will make a good demonstration for the other low efficiency coal-fueled power generation units in China.

The Green Strategy of Old City Drainage System Reconstruction: A Case of New York City, The US

近年来,随着城市化进程的不断推进,城市建设过程中 不透水面积的比例不断增加,致使城市下垫面的结构发生巨 大变化,严重破坏了原有自然界的水循环系统 。这导致城 市的水安全、水资源、水生态及水环境都遭受了不同程度的 威胁。为了解决城市化所带来的这一系列问题,我国掀起了 海绵城市的建设热潮。在我国两批海绵城市试点申报的政府 文件——财办建 [2015]4 号 [2] 和财办建 [2016]25 号 [3] 中,均对 老城占比作出了指示,北京的试点区面积 19.36 km,老城占 8.77 km ;天津的试点区面积 39.5 km,老城占 17.83 km ; 池州的试点区面积 18.5 km,老城占 10.68 km ;等。这些老 城所面临的地上和地下问题的特殊性,是海绵城市建设的焦 点与难点。例如在地上,老城的人口密度高、车流量大、公 共服务设施密集、市民对公共空间改造存在抵触情绪,以及 绿地有限,造成难以提供充足的空间以布置绿色基础设施等 问题,给工程建设带来了很大阻力 [4] ;在地下,管网设计标 准偏低、雨污管网混接、管网老化失修,以及雨污合流制管 网带来的合流制溢流(CSO: Combined Sewer Overflows)污 染等问题。因此在当前老城的海绵城市建设中,如何降低对 城市正常运转和居民正常生活的影响?如何对老城排水系统 进行提标改造,缓解老城的合流制溢流问题,同时增加城市 的宜居性?如何从制度建设、目标制定、规划设计、监测评 估以及公众参与等方面切实推进海绵城市建设?这一系列问 题有待进一步的深入研究。 纽约市为解决合流制溢流问题,采用绿色基础设施和灰 色基础设施相结合的改造方略,并于 2010 年 9 月发布了《纽 约市绿色基础设施规划》。他山之石,可以攻玉。本文通过 对此规划方案及实施过程中遇到的诸多问题进行回顾与分析, 拟为我国当前老城的海绵城市建设提供参考。 The Green Strategy of Old City Drainage System Reconstruction: A Case of New York City, The US 老城排水系统改造的绿色方略 —— 以美国纽约市为例

Insights into the pollutant-removal performance and DOM characteristics of stormwater runoff during grassy-swales treatment.

ABSTRACT The water purification performance of grassy swales for treating stormwater road runoff was evaluated using a simulated experimental device in two different seasons. The results showed that the removal rates for total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) reached 89.90%, 56.71%, 32.37%, and 19.67%, respectively, in summer, and 34.09%, 7.75%, 56.71%, and 13.33%, respectively, in winter, suggesting that grassy swales showed higher water purification performance in summer than in winter. Soil filtration in grassy swales also showed high removal rates of TSS, COD, TN and TP in summer (98.13%, 59.10%, 33.82%, and 24.59% respectively). The structure, composition and source of dissolved organic matter (DOM) were investigated using ultraviolet visible (UV–Vis) spectra and fluorescence spectra. The spectral parameters indicated a relatively high humification and aromaticity of DOM, and a relatively higher contribution of organic matter derived from microbial substances in summer than in winter. In addition, grassy-swale treatment showed a slight decrease in metal-ion concentrations at the surface, while the removal rates in the bottom samples were 38.42%, 40.59%, 33.81%, and 40.06% for Cu2+, Cd2+, Pb2+, and Zn2+, respectively. The results of 2D-COS suggested that grass swales treatment can change the binding sites and binding sequencing of DOM with heavy metals and further influence the metal speciation, mobility and biotoxicity.