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Biochar-derived water-extractable organic matter (WEOM) was obtained under low-temperature pyrolysis (300 °C) using corncob as raw material. WEOM may affect the mobility and bioavailability of soil heavy metals (HMs) through complexation when biochar was used for soil HM remediation. Herein, the characteristics of complexation between HMs (Cr(III) and Cu(II)) and biochar-derived WEOM were investigated by using spectroscopic techniques in conjunction with parallel factor (PARAFAC) analysis and two-dimensional correlation spectroscopy (2D–COS). Six components were identified by PARAFAC modeling, in which protein-, fulvic- and humic-like components accounted for 48.86%, 25.63% and 25.51%, respectively. A nonlinear model was employed to determine the conditional stability constant (KM) and total ligand concentration (CL) of WEOM-HM complexes. The log KM values were in the range of 4.02–5.04 for WEOM-Cr(III) and 4.04–6.58 for WEOM-Cu(II). The 2D–COS in conjunction with log-transformed synchronous fluorescence spectroscopy (SFS) suggested that WEOM components were preferentially complexed with HMs in the following order: 433/270, 433/335, 496/270, 496/335, 370/335, 433/402, 496/402, 335/290, 402/290 for Cr(III), and 290/280, 390/280, 433/280, 496/280, 433/335, 496/335, 390/335, 433/420, 496/402, 335/290, 316/290 for Cu(II). The results of 2D–FTIR–COS suggested a preferential bonding of Cr(III) to the C–N group of alkyl, and Cu(II) to the C O group of alcohols, ethers and esters. Meanwhile, the C O group of ethers and the C N group of alkyl indicated preferential susceptibilities for the addition of Cr(III) and Cu(II) at different concentrations. In addition, protein-like components had remarkably higher total ligand concentration (CL) than fulvic- or humic-like components.

Four different types of ecological concrete (EC), including an applied concrete (AC), and three kinds of modified concretes (MC1-MC3) were used to study the removal performance of rainfall surface runoff and their impacts on changes in dissolved organic matter (DOM). The results showed that MC3 indicated the best performance of water purification; the removal ratios of total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH4+-N), total organic carbon (TOC), and total suspended solids (TSS) were 58.08%, 95.57%, 92.44%, 91.72%, and 87.62%, respectively. Fluorescence excitation-emission matrix (EEM) spectroscopy combined with parallel factor analysis (PARAFAC) was able to identify five fluorescent components (C1-5), including three humic-like components (C1, C3, and C4) and two protein-like components (C2 and C5). The three MCs could more effectively remove both small-molecular-weight protein-like component C2 and high-molecular-weight humic-like components C1, C3, and C4, compared to the AC. The result of two-dimensional correlation spectroscopy (2D-COS) showed that protein-like components had higher susceptibility than humic-like substances did. Fluorescent components at 330, 305, 410, and 410 nm were found with a preferential change in the AC, MC1, MC2, and MC3 respectively, suggesting that fulvic-like, protein-like, humic-like, and humic-like substances can be removed preferentially in the AC, MC1, MC2, and MC3 respectively. This study is valuable for improving surface runoff purification of rainwater in rural areas and for reducing agricultural non-point source pollution.

An experimental simulation device was used to evaluate the water purification performance of soil improved with two different conditioners, which were cornstalk and zeolite (CSZ), turf and quartz sand (CTS) in this study. The results showed that the removal rates for total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) reached 75.58%, 25.71%, 68.37%, and 64.67%, respectively, for CSZ, and 85.09%, 92.75%, 76.71%, and 98.33%, respectively, for CTS, suggesting that soil improvement showed higher water purification performance with the CTS conditioner than with the CSZ conditioner. The structure, composition, and source of dissolved organic matter (DOM) were probed using ultraviolet visible (UV–Vis) spectra and fluorescence spectra. The spectral parameters indicated that the CTS conditioner-improved soil showed a relatively high humification and aromaticity of DOM, and a relatively higher contribution of organic matter derived from microbial substances. In addition, the results of 2D-COS suggested that the binding sites and sequences can be significantly influenced by soil improvement, and vary between the two kinds of conditioners. The CTS-improved soil was more effective in reducing fluorescent DOM than was the CSW-improved soil. This study can provide a scientific foundation for the treatment of agricultural non-point source (NPS) pollution.

Hydrophyte decomposition caused large amounts of dissolved organic matter (DOM) to enter aquatic environment that influence the migration and transformation of heavy metals (HMs). Six hydrophytes with five dry weight gradients (DWG) were used for the decomposition experiments. The results showed that protein-like materials occupy relatively high content in the hydrophyte-derived DOM. The binding properties of DOM-Cu(II) have been explored by using two-dimensional correlation spectroscopy (2D-COS) in conjunction with synchronous fluorescence spectroscopy (SFS) and log-transformed SFS. The weak signals of binding site can be amplified by the log-transformed 2D-COS analysis. Herein, more binding sites can be identified by the log-transformed 2D-COS analysis. The results reveal that tryptophan-like materials show a preferential sequence of binding Cu(II) in the hydrophyte-derived DOM with a relatively low DWG and sediment DOM, and fulvic-like substances indicate a preferential sequence of binding Cu(II) in the hydrophyte-derived DOM with a relatively high DWG. Meanwhile, the results of binding parameters indicate that the log K is the range of 3.61–4.25, 4.33–4.74, 4.59–4.97, 3.91–4.41, and 4.14–4.78 for D1-D5, respectively, suggesting that hydrophyte decomposition can change the binding affinity between DOM components and Cu(II). The complexes of fluorescent components with Cu(II) showed a high log K value at long wavelength (e.g. humic-like substances), and a relatively low fluorescent ligand proportion (f%) at shorter wavelength in the hydrophyte-derived DOM. However, the log K is the range of 3.08–4.31, 4.09–4.45, 3.93–4.35, 4.39–4.75, and 3.95–4.36 for C1-C5, separately. Protein-like substances with Cu(II) showed a relatively high log K value with the exception of C4. The log-transformed 2D-COS can be an analytical tool to understand the binding heterogeneity of DOM with HMs. The study can provide a guide for managing and controlling the effects of hydrophyte decomposition.

Characteristics of physicochemical parameters, dissolved-phase heavy metals, and polycyclic aromatic hydrocarbons (PAHs) were investigated for 68 urban snowmelt surface runoff and snowpack samples collected from five different functional areas in Beijing, including a business area (BA), a cultural and educational area (CEA), a garden area (GA), a residential area (RA), and a roadside area (RSA). Both snowmelt surface runoff and snowpack were significantly polluted by organic matter, as indicated by their high concentrations of chemical oxygen demand (COD) and total organic carbon (TOC). Among the 11 heavy metals analyzed, Zn was the most enriched in all samples, followed by Mn, Fe, and Cu, whereas the concentrations of Pb, Cr, Cd, As, Ni, Sb, and Co were comparatively low. The results suggested that typical traffic emissions, natural events, industrial practices, and human activities were mainly sources of heavy metals. Low molecular-weight (LMW) PAHs were the dominant sources in snowmelt and snowpack. Anthracene (Ant) and fluorene (Flo) were the most enriched PAHs in both snowmelt surface runoff and snowpack. Coal burning for heating and traffic activities were the most important contributors of PAH pollutants in snowmelt surface runoff and snowpack in Beijing in the winter. Ecological risk assessment demonstrated, however, that heavy metals in snowmelt surface runoff pose little risk to downstream aquatic environments. A middle potential ecological risk could be caused by Ant, Flo, benzo[g, h, i]perylene (BghiP), and benzo[a]pyrene (BaA).

In this research, the adsorptive removal of diclofenac sodium, one of the representative pharmaceuticals and personal care products, from aqueous solution using Fe3O4@MOF-100(Fe) magnetic microspheres was studied for the first time. The Fe3O4@MOF-100(Fe) microspheres exhibit strong magnetism and stability, which were observed as a core-shell structure. The maximum adsorption capacity of Fe3O4@MOF-100(Fe) for diclofenac sodium can reach 377.36 mg L−1, which was higher than most of the adsorbents reported. The adsorption kinetics follows the pseudo-second-order kinetic equation. And the adsorption equilibrium of DCF can be described with Langmuir isotherm. In the cycle experiment, Fe3O4@MOF-100(Fe) material performed high adsorption efficiency for low-concentration diclofenac sodium solution, and the removal rate can still reach 80% after 5 cycles of adsorption without desorption. The mechanisms including electrostatic interaction, H-bond interaction, and π-π interaction that coexisted in the adsorption processes would be of benefit to enhance the adsorption capacity. The Fe3O4@MOF-100(Fe) magnetic microspheres offer exciting opportunities for further application.

The presence of pathogenic microorganisms in water is a great threat to human health, and photocatalysis is promising for disinfection. However, the research on virus inactivation with visible-light photocatalysis is still limited, especially the coexistence of virus and its host bacteria. In this study, bacteriophage f2 and its host E. coil 285 were used as the model microorganisms, and the disinfection performance of prepared Cu-TiO2 nanofibers under visible light was investigated. The result showed that the prepared Cu-TiO2 nanofibers showed a brilliant ability in terms of removing bacteriophage f2 and E. coil 285 under visible light. Series experiments indicated that the initial pH didn't affect the photocatalytic disinfection performance significantly. In the certain range, the removal efficiency of bacteriophage f2 increased with the increase of catalyst dosage, light intensity and temperature, but decreased with the increase of initial virus concentration. In virus/bacteria mixed system, bacteriophage f2 exhibited stronger resistance to photocatalytic oxidation than E. coil 285, and the removal of bacteriophage f2 was obviously affected by being mixed with E. coil 285, while the removal of E. coil 285 almost remained unchanged after being mixed with bacteriophage f2. Further research proved that competitive adsorption in mixed system played a certain role in E. coli 285 inactivation, while the free reactive oxygen species (ROSs) in the bulk phase played a crucial role in phage f2 inactivation.

Chemical and biological pretreatments (with NaOH, HCl, CO(NH2)2 and cellulase) were used to pretreat rice straw at ambient temperature (about 20 °C) to improve its biodegradability and increase anaerobic biogas production. The NaOH and CO(NH2)2 pretreatments reduced the percentage contents of hemicellulose and lignin. The HCl pretreatment mainly dissolved the hemicellulose and resulted in decreases of 12.5–7.1% of the hemicellulose. The percentage content of cellulose showed a dramatic decrease, from 38.3 to 10.9%, after the cellulase pretreatment. Compared with untreated rice straw substrate, the total biogas yield ratios were 3.38–5.91, 1.63–2.99, 1.93–5.22 and 3.62–6.45, with a hydraulic retention time of 30 days, under NaOH, HCl, CO(NH2)2 and cellulose pretreatments, respectively. The highest yields of biogas and methane were obtained from 40 U/g total solids (TS) cellulase-pretreated rice straw (20.433 and 9.918 L respectively). Biogas production yields of volatile solids (VS) were 123.7, 273.8, 318.5, 353.5 mL/g for control, 6% CO(NH2)2-, NaOH- and 40 U/g TS cellulase-pretreated rice straw substrate, respectively. Compared to untreated rice straw substreates, cumulative biogas production yields increased 16–103, 25–122% for NaoH- and cellulase-pretreated rice straw substrate, respectively. The results suggested that the highest removal efficiencies of TS and VS were obtained from 6% NaOH-pretreated (53.80 and 36.80%), 6% CO(NH2)2-pretreated (54.90 and 36.10%) and 40 U/g TS cellulase-pretreated (51.30 and 37.30%) rice straw substrate. In short, NaOH, HCl, CO(NH2)2 and cellulase pretreatment was suitable to enhance the biogas production. However, to choose the optimal treatment, the energy requirements relative to the energy gain as extra biogas production have to be taken into account, as well as the costs of chemicals or enzymes.

Dissolved organic matter (DOM), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) collected from a water intake and a water outlet in a constructed rapid infiltration (CRI) system were investigated. The results indicated a relatively high microbially derived DOM and an increasing humification degree of DOM in the CRI treatment process. The removal rates of dissolved organic carbon (DOC), COD and TN ranged from 15.2 to 74.6%, 58.9 to 80.4% and 44.8 to 73.8%, respectively. TP concentrations showed a marked increase from inflow to outflow. Fluorescence regional integration (FRI) analysis showed that tyrosine-like materials (P I, n) were easily biodegraded, compared to humic- and fulvic-like substances, whose removal rates ranged from 78.4–90.6%. The tryptophan-like materials (P II, n) showed a marked decrease, in the range of 56.1–79.3%. The humic-like substances (P V, n) had relatively low removal rates in the range of 0.3 to 50.9%. The COD, TN, and DOC were positively correlated with the various P i, n values and negatively correlated with the humification degree, indicating that the COD, TN and DOC decreased with the degradation of DOM and the increase of DOM humification degree.

Soil samples were collected from the areas surrounding Wuliangsuhai Lake in China. Dissolved organic matter (DOM) was extracted from the samples and characterized by fluorescence and UV-Vis spectra. Spectral properties and humification degree of DOM were studied. The results indicated that both humic- and protein-like fluorophores were present in the DOM spectra, and the former was the dominant component. The analysis of humification (HIX) and r (A, C) indices revealed that the maximum humification degree in three agricultural soils (AAF, ASC, and ASW) was presented in the second soil layer (20‒40 cm). However, the humification degree of the two Halophytes soils (SSE and GKF) decreased with increasing depth. One index, I344/270, showed that humification degree increased gradually with an increasing proportion of humic-like acid. There was a significant positive correlation between humification degree (HIX) and aromaticity (SUVA254), indicating that a higher aromaticity corresponded to a higher humification degree. Land use was an important factor responsible for the major difference of cation exchange capacity (CEC) in different soils, which led to a higher CEC value in the second soil layer for the three agricultural soils. CEC values and humification degree had the same trend for all five soils. The correlation analysis showed that there was a significant positive correlation between HIX and CEC, and a negative correlation between the r (A, C) index and CEC, indicating that humification degree increases gradually with increasing CEC values.

Dissolved organic matter (DOM) collected from the surface and overlying waters in different functional regions in Lake Baiyangdian were analyzed by spectroscopic techniques combined with principal component analysis (PCA) and hierarchical cluster analysis (HCA), to interpret water quality, and sources of pollutants. The results showed that the deterioration of water quality has intensified at river estuary and aquaculture area. Meanwhile, these regions dominated by plants had relatively low dissolved oxygen concentrations. UV-vis spectra showed lower humification degree and simpler molecular structure in the DOM collected from the pollutant-receiving region. The analysis of PCA combined with synchronous fluorescence spectra yielded two principal components (PCs) that account for 99.44% of the variance. PC1 showed a dominant protein-like fluorophore at 279 nm and PC2 was characterized by dominated fulvic-like fluorophores (325 and 331 nm). The results of PCA indicated that DOM collected from the river estuary, the aquaculture region, and the eutrophication area exhibited a higher protein-like fluorophore, and higher PC1 and lower PC2 loadings (PC1 > 0.7, PC2 0.7). HCA identified four clusters that accorded with the PCA results. This study suggested that water quality and the sources, and spectral characteristics of DOM were influenced mainly by human activities (agriculture, industrial, and domestic wastewater from upstream, food and excrement from aquaculture) and natural processes (aquatic-plant and microorganism activities).

The nano zero valent iron (nZVI) is an efficient environmental remediation material, but it is easy to be oxidized and agglomerated, which limits its application in the environment. In this paper, bacterial cellulose membrane was used as a carrier material to reduce three different concentrations of ferrous ions by in-situ liquid-phase reduction method using sodium borohydride, and three kinds of bacterial cellulose membrane loaded with nanometer zero valent iron (BC-nZVI) samples were successfully prepared. The physical and chemical properties of BC-nZVI before and after the reaction were characterized by SEM, XRD and XPS. The effects of pH, dose and reactive oxygen species (ROS) on the inactivation of bacteriophage MS2 were studied. The results showed that nano-zerovalent iron was successfully loaded on the bacterial cellulose membrane. The particle size of nZVI particles loaded in BC-nZVI was about 200 nm under the condition of low ferrous sulfate, effectively alleviating the agglomeration phenomenon. And the inactivation efficiency of BC-nZVI on MS2 has been improved, reaching 4 log in 5 min. BC-nZVI showed two stages of inactivation characteristics, the first stage was 5 min to achieve 4 log high-efficiency inactivation stage, the second stage was the follow-up slow inactivation stage. At different pH value, the removal rate of MS2 by BC-nZVI increased with the increase of pH value, which was different from that of nZVI. The radical scavenger experiments showed that the main factor affecting the removal rate of MS2 in the first stage was •O2−, followed by Fe (IV), while the effect of •OH was not significant. In the second stage, the main influencing factors was •OH. Under alkaline condition, the yield of •O2− was increased, the reaction time was prolonged, and the deactivation rate of MS2 was increased. These results provide new ideas for the practical application of nZVI in the treatment of pathogenic microorganisms.

Carbamazepine (CBZ) is a worldwide anti-epileptic drug, whose fate and migration can be greatly influenced by contact with dissolved organic matter (DOM). The properties of DOM in road runoff can be greatly changed by grassy swale (GS) treatment, which influences the complexation of CBZ with DOM. Spectroscopic techniques were employed to explore the different binding properties between CBZ and DOM, and to understand the migration and biogeochemistry of CBZ. The two-dimensional correlation spectroscopy (2D-COS)demonstrated that effluent DOM displayed more binding sites for CBZ than influent DOM, and the binding sequencing of CBZ with DOM fluorophores can be greatly influenced by GS treatment. The results also suggest that protein-like materials exhibit higher log KM values than other fluorescent components, indicating that fluorescent protein-like materials play a crucial role in the biogeochemical behavior of CBZ. Meanwhile, the log KM values showed a remarkable increase after GS treatment. GS treatment can also remove most fluorescent DOM, reducing the risk of CBZ in the water environment.

Composting leachates were collected to investigate the fluorescent characteristic and compositional change of dissolved organic matter (DOM) and the effects of the DOM and nutrients on heavy metal distribution during a leachate combination treatment process. Excitation-emission matrix (EEM) fluorescence spectra showed that, with the progress of the treatment units, the content of fulvic-like, humic-like, and protein-like substances gradually decreased. One fulvic-like component (C1), three humic-like components (C2, C3, and C4), and three protein-like components (C5, C6, and C7) were identified in the leachate DOM by parallel factor analysis. Anaerobic-aerobic processes removed a large fraction of the tyrosine-like component (C7) and tryptophan-like component (C6) and a small amount of humic-like component (C2), while the membrane bioreactor showed a good removal effect on protein-like component. The ultra-filtration membrane treatment had a removal effect on fulvic-like and humic-like component and other recalcitrant compounds, while the reverse osmosis treatment had a good removal effect on both humic-like and protein-like components. Correlation analysis indicated that Mn and Cr were primarily associated with protein-like components and nutrients in the composting leachates. Ni and Pb were bound to fulvic-like, humic-like, and protein-like components, Co and Zn interacted with inorganic nitrogen and total phosphorus, and Cd only interacted with inorganic nitrogen.

The goals of this study are to identify the individual fluorophore component in dissolved organic matter (DOM) of saline-alkali soils, to determine the binding capacities and stability constants of Cu (II) with fluorescent DOM components, and to analyze the potential impact on the complexation between Cu (II) and DOM in different soil environment. DOM extracted from five saline-alkali soil samples were studied by fluorescence quenching titrations combined with three-dimensional excitation-emission matrix (3D-EEM) spectra and parallel factor analysis (PARAFAC). Modified Stern–Volmer model was used to calculate the conditional stability constant (K) and the percent of fluorophores (f %) participating in the complexation reaction. Three main fluorescent components in the DOM, e.g., fulvic-like (component 1), humic-like (component 2), and protein-like (component 3) were identified and characterized by fluorescence EEM-PARAFAC. Both the components 1 and 2 showed fluorescence quenching by gradual addition of Cu (II), while component 3 had no marked change in fluorescence intensity. The higher log K of DOM-Cu (II) complexes suggests that the DOM has a high Cu binding affinity. Meanwhile, humic-like components showed higher in the proportion of organic ligands than those of fulvic-like components in the DOM of saline-alkali soils. The fluorescence quenching titration using EEM-PARAFAC analysis allows for the assessment of metal ion interactions with specific fluorophores, and is a good approach to study the geochemical behavior of metal ions in saline-alkali soils and to provide a support for the management of saline-alkali soil environment.

The presence of pathogenic microorganisms in water is a great threat to human health, and photocatalysis is promising for disinfection. However, the research on virus inactivation with visible-light photocatalysis is still limited, especially the coexistence of virus and its host bacteria. In this study, bacteriophage f2 and its host E. coil 285 were used as the model microorganisms, and the disinfection performance of prepared Cu-TiO

The lack of access to clean water remains a severe issue all over the world. Coupling photocatalysis with the membrane separation process, which is known as a photocatalytic membrane reactor (PMR), is promising for water treatment. PMR has developed rapidly during the last few years, and this paper presents an overview of the progress in the configuration and operational parameters of PMRs. Two main configurations of PMRs (PMRs with immobilized photocatalyst; PMRs with suspended photocatalyst) are comprehensively described and characterized. Various influencing factors on the performance of PMRs, including photocatalyst, light source, water quality, aeration and membrane, are detailed. Moreover, a discussion on the current problems and development prospects of PMRs for practical application are presented.

In this study, the water purification performance of grassy swales for treating stormwater runoff was evaluated using a simulated experimental device. The binding properties of dissolved organic matter (DOM) in stormwater runoff samples from Beijing were measured by ultraviolet visible absorbance spectroscopy and excitation–emission matrices, combined with parallel factor analysis (PARAFAC). The concentrations of total nitrogen and phosphorus were significantly decreased after treatment by grassy swales: 50%–95.23% of total suspended solids and total organic carbon were removed, respectively. Additionally, the removal of heavy metal ions was 30.95%–97.39%. The spectral parameters indicated that humification and aromaticity of DOM would be greatly increased by grassy swale treatment. Two humic-like components and one protein-like component were identified in the runoff DOM using excitation–emission matrices coupled to PARAFAC. With progressive grassy swale treatment, the content of humic-like components increased and protein-like substances gradually decreased. Two-dimensional correlation spectroscopy demonstrated that the effluent DOM of grassy swale samples displayed different binding sites for Cu (II). Thus, the binding sequencing of Cu (II) with DOM fluorophores can be greatly influenced by grassy swale treatment. The results may provide a solid foundation for the treatment of urban runoff pollution.

Dissolved organic matter (DOM) is an important component of the carbon cycle and a critical driver in controlling a variety of biogeochemical and ecological processes in aquatic environments. We reported the spatial variability of DOM quantity and composition which collected from Lake Wuliangsuhai in arid and semi-arid region. This study could serve as a useful tool to assess the dynamics of DOM in similar complex wetlands or lakes and provide a support for ecological environment governance and restoration. The results showed that five fluorescent components, including three humic-like (C1, C2 and C4), and two protein-like components (C3 and C5), can be identified by excitation emission matrix (EEM) spectra combined with parallel factor analysis (PARAFAC) in Lake Wuliangsuhai. The spatial variation of the components showed the difference in the dominant fluorescent component. There were dominant protein-like component C5 and humic-like component C2 in water and pore water. Components C3 and C4 were the main fluorescent components in 0–10 cm sediments. In 10–20 cm sediments, C1 and C3 were the dominant humic-like and protein-like component respectively. The PARAFAC–PCA displayed four PCA factors. The humic-like components C2 and C4 concurrently showed positive factor 1 loadings. Factor 2 was mainly explained by terrestrial and marine humic-like component C1. The autochthonous, tryptophan-like, fluorescent component C3, showed positive factor 3 loadings. The autochthonous, tyrosine-like, fluorescence component C5, having a low factor loading in other three factors, showed extremely high factor 4 loading. The EEM–PARAFAC combined with PCA showed varying contributions of terrestrial versus autochthonous DOM sources for the different regions in the wetland, suggesting that differences in human activities control DOM dynamics.

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.

Environmental contextDissolved 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. AbstractDissolved 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.

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 (PC10.9, PC20.3), 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.

In order to find out the heavy metal concentrations and their potential ecological risks on sediments in Baiyangdian Lake, 0-14 cm surface sediments had been collected by the no-disturbance-gravity sampler at seven representative sampling points of Baiyangdian Lake. Optimized BCR sequential extraction procedure was used to carry out the analysis of heavy metal forms in the surface sediments. The heavy metal contents of different forms and in different depths were determined. The relationship between different forms of heavy metal and total organic carbon (TOC) in the sediments was analyzed. The geo-accumulation index (Igeo) was employed to evaluate the extent of heavy metal contamination. The results demonstrated that Co, Fe, Mn, Pb, Zn were mainly in residual form, acid soluble form, Fe-Mn oxide and organic matter bound forms respectively. The tendency of organic bound form of heavy metals and TOC of sediments was greater than the others. The concentration of Co, Pb, Zn decreased with the increase of sediment depth, with the maximal concentration was between 0-2 cm, while the concentration of Mn was the minimal between 6-8 cm and the maximal was at 14 cm. Baiyangdian sediments were not contaminated as a whole by Co, Mn, apart from medium pollution in the entrance of the Fuhe River. The other regions were lightly polluted by Zn and Pb.

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).

Constructed wetlands are widely used to purify wastewater in some developing countries. As filter substrates in such wetland, these substrates play important role on removal of pollutants from wastewater. Selecting suitable substrates is one of the effective ways to improve the performance of constructed wetland on treating wastewater. In this study the phosphorus adsorption capacities of sand, zeolite, vermiculite, two clay soils, two industrial by-products named steel slag and fly ash are examined for their potential use as substrate in constructed wetland. Both Freundlich and Langmuir adsorption isotherms are very fit for describing the adsorption characteristics of these substrates. Two industrial by-products including steel slag and fly ash have higher phosphorus adsorption capacity, which had 50490 and 17934 mg x kg(-1) respectively. Followed vermiculite, two clay soils named yellow cinnamon and xiashu loess with phosphorus adsorption capacity of 3473, 1893.7 and 1582 mg x kg(-1) respectively. The zeolite and sand had the least phosphorus adsorption capacity with 813.7 and 302 mg x kg(-1) respectively. The experiments on purifying phosphorus from synthesize domestic sewage using these substrates also demonstrate this conclusion. The ability of removal phosphorus of these substrates have closely relationship with their makeup and chemical properties such as pH, total calcium and reactive calcium, reactive Fe, Al including poorly coastal and amorphous Fe, Al oxide. The steel slag and fly ash with higher reactive Ca, such as calcium oxide, have better adsorption capacity of phosphorus than other substrates, and the substrates which contained more reactive Fe also have a better ability of adsorption phosphorus than others. To assess the environmental risk for using these substrates above, the phosphorus de-sorption characteristics of these substrates are also studied. The process of phosphorus desorption quickly reached equilibrium in no more than 4 hours in the experiments, the ratio of desorption and adsorption of phosphorus in substrates above is lower except sand. To take suitable measures to manage substrates above, the risk of pollution of phosphorus form these substrates will be controlled.