Tryptophan-like Component Research Articles

Analysis of Fluorescence and Biodegradability of Wastewater

Three-dimensional fluorescence spectrometer was adopted for the content analysis of different types of organics in coking wastewater before biochemical treatment and through biochemical treatment, and the model of parallel factors was employed to analyze fluorescence components and contents. It was found that tryptophan-like components were the most easily degraded by biology, while humic-like components were the least easily degraded. Meanwhile, it had been seen that the change trends over time of total fluorescence densities of proteinoid fluorescence, and degradable organic fluorescence were highly consistent with that of parameter values of COD, NH3-N in this wastewater after analyzing the trends of the two indexes. It was proved that the three-dimensional fluorescence spectrum method was appropriate for the accurate degradation analysis of wastewater components.

Composition of dissolved organic matter controls interactions with La and Al ions: Implications for phosphorus immobilization in eutrophic lakes

Applications of aluminium (Al) salt or lanthanum (La) modified bentonite (LMB) have become popular methodologies for immobilizing phosphorus (P) in eutrophic lakes. The presence of humic substances, has been shown to inhibit this form of treatment due to the complexation with La/Al. However, the effects of other dissolved organic matter (DOM), especially that derived from phytoplankton (the dominant source in eutrophic lakes) are unknown. In this study, the interaction with La/Al of Suwannee River Standard Humic Acid Standard II (SRHA) and algae-derived DOM (ADOM) were investigated and compared. Differed to SRHA which was dominated by polyphenol-like component (76.8%, C1-SRHA), majority in ADOM were protein-like substance, including 41.9% tryptophan-like component (C2-ADOM) and 21.0% tyrosine-like component (C3-ADOM). Two reactions of complexation and coprecipitation were observed between SRHA/ADOM and La/Al. Complexation dominated at low metal inputs less than 10 μM and coprecipitation was the main reaction at higher metal inputs. For ADOM, the tryptophan-like component (C2-ADOM) was the important component to react with metal. The reaction rate for C2-ADOM with La were about two-third of that for C1-SRHA, indicating that the influence of C2-ADOM was significant during the P immobilization by La/Al-based treatment in eutrophic lakes. The P removal data in the presence of ADOM confirmed the significant inhibition of ADOM. In addition, based on the composition of coprecipitates and relatively biodegradable character of tryptophan-like substances (C2-ADOM), the coprecipitation of ADOM was assumed to reduce the stability of precipitated P in eutrophic lakes. The release of P from the potential biodegradation of the coprecipitates and thus the possible decline of the performance of P immobilization by La/Al-based treatments is an important work in the future.

Ca2+ complexation of dissolved organic matter in arid inland lakes is significantly affected by drastic seasonal change of salinity

CaCO3 precipitation is one of the most common and important geochemical processes in the arid inland waters and it can be significantly affected by interaction of DOM with Ca2+. Effects of the drastic seasonal change of water salinity on interaction of DOM with Ca2+ in the arid inland waters were completely unknown. In the present study, complexation of DOM with Ca2+ in the freshwater (0.5‰ salinity) and hypersaline water (70‰ salinity) were comparatively examined by excitation-emission matrix (EEM) fluorescence quenching titration and isothermal titration calorimetry (ITC). The complexation of DOM with Ca2+ was significantly influenced by the drastic change of salinity. The ITC complexation is exothermic at 0.5‰ salinity but turns to an endothermic process at 70‰ salinity. More energy is needed for the complex reaction between DOM and Ca2+ under the hypersaline condition than in the fresh water. Fluorescence quenching titration indicates that DOM has stronger binding ability toward Ca2+ in the freshwater than in the saline water, and more fractions of DOM in the freshwater are accessible to Ca2+ than in the saline water. Ca2+ complexation in the DOM is dominated by the tryptophan-like components at both salinities and the complexation of Ca2+ with fulvic acid-like components is ignorable. The findings is important for understanding the aquatic geochemical processes in some lakes that seriously affected by irrigation water use in the arid zone.

A combined heterotrophic and sulfur-based autotrophic process to reduce high concentration perchlorate via anaerobic baffled reactors: Performance advantages of a step-feeding strategy

The combined anaerobic baffled reactors (ABRs) of heterotrophic and sulfur-based autotrophic processes were first investigated for the removal of high perchlorate concentration under different feeding strategies. The removal efficiency of the step-feeding ABR (SF-ABR) reached 97.56% at 800 mg/L perchlorate, which was significantly superior to the normal-feeding ABR (NF-ABR). In three components of the extracellular polymeric substances (EPS), the fluorescence intensity of the tryptophan-like component were identified by fluorescence excitation–emission matrix (EEM) spectra with parallel factor (PARAFAC) analysis, and exhibited a positive relationship with the perchlorate removal rate in the heterotrophic perchlorate reduction unit (HPR unit) of the SF-ABR (R2 = 0.9791) and NF-ABR (R2 = 0.9860). Bacterial community analysis suggested the dominating perchlorate reducing bacteria and the diversity in two ABRs. Principal component analysis indicated that the electron donor affected the microbial community structures. The study confirms that the SF-ABR is a powerful bioreactor for the combined heterotrophic and sulfur-based autotrophic process.

Spatial Distribution and Degradation of CDOM in the Minjiang River in Summer

The composition, distribution, and degradation of chromophoric dissolved organic matter (CDOM) in the lower reach and estuary of the Minjiang River were analyzed using fluorescence excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC) and microbial and photochemical degradation experiments. The results show that there are three types of fluorescence components in the study area:humic-like, tyrosine-like, and tryptophan-like. The humic-like components are the main components in the river zone, while the protein-like components become dominant with increasing salinity in the estuary. The change of the CDOM abundance shows a notable spatial distribution pattern. The absorption coefficient a(280) of CDOM is lower in the river, increases after entering the urban area, shows a decreasing trend in the suburbs, and rapidly declines in the estuary. A conservative estimate of the contribution of the Fuzhou urban area to the CDOM of the Minjiang River is 8%. The a(280) in the river is susceptible to microbial and photochemical degradation and the degradation percentages are (28±8)% and (44±7)%, respectively. The bioavailability and photochemical reactivity of a(280) are much higher in the river than in the estuary. The humic-like, tyrosine-like, and tryptophan-like components show a higher photochemical reactivity in the river, with degradation percentages of (75±0.5)%, (58±21)%, and (73±3)%, respectively. The fluorescent components are not labile with respect to microbial degradation and humic-like components are accumulated after 28 days of microbial culture.

Photodegradation response of humic acid using UV-Visible absorption and Excitation-Emission Matrix Spectra

湖泊生态系统作为自然界重要的碳库，光照强度的变化对于湖泊的碳循环过程可能产生重要的影响.以云南老君山高山湖泊天才湖周边土壤中的腐殖酸作为外源溶解性有机物（DOM）的代表物，通过腐殖酸模拟光降解实验，考察光照强度对外源DOM光降解过程的影响.研究结果表明：腐殖酸光吸收系数a₄₄₀、465 nm和665 nm波长处吸光度比值E₄/E₆的下降幅度均为：对照组 < 20 W光照组 < 40 W光照组，a₄₄₀、E₄/E₆和光谱斜率S_R显著相关，表明紫外辐射使得腐殖酸溶液浓度降低、相对分子量下降，且光照强度越强，腐殖酸的光降解程度越大.通过EEM-PARAFAC模型识别出光降解过程中腐殖酸溶液中含有5种荧光组分：UV类腐殖质（C1）、UVA类腐殖质（C2）、类色氨酸（C3）、UVC类腐殖质（C4）和类络氨酸（C5）.40 W光照组中4种荧光组分的降解程度与降解速率均大于20 W光照组，降解程度均为：C4 > C3 > C2 > C1，降解速率为C2 > C4 > C3 > C1，说明不同的荧光组分对光照强度的响应不同.该研究有助于阐明外源DOM的光降解途径与归趋.;UV irradiation intensity changes have great influence on carbon cycle in lake, which is one of the most important carbon pools in nature. To understand the effects of UV irradiation on allochthonous dissolved organic matter(DOM)in lakes, simulated photodegradation experiments were conducted. We extracted humic acid from soil surrounding an alpine Lake Tiancai as allochthonous DOM. During the photo-irradiation process, the order of decreasing level of a₄₄₀ and E₄/E₆ was 40 W group, followed by 20 W group and control group. Moreover, S_R, a₄₄₀ and E₄/E₆ were significantly correlated, suggesting that the concentration and relative molecular weight of humic acid decreased with increasing UV irradiation intensity. Five fluorescent components were identified through using EEM-PARAFAC models, included UV humic-like component (C1), UVA humic-like component (C2), tryptophan-like component (C3), UVC humic-like component (C4), tyrosine-like component (C5). The photodegradation rate and degree of four fluorescent components in 40 W group were greater than 20 W group, the order of photodegradation rate was C4 > C3 > C2 > C1 and the order of photodegradation degree was C2 > C4 > C3 > C1, indicating that fluorescent components response diversely to different UV irradiation intensities.

Unraveling the sources and fluorescence compositions of dissolved and particulate organic matter (DOM and POM) in Lake Taihu, China

Organic matter (OM), a complex entity with diverse functional groups and molecular sizes, has important effects on aquatic systems. We studied the optical compositions and sources of dissolved organic matter (DOM) and particulate organic matter (POM) in Lake Taihu, a large, shallow and eutrophic lake in China. Significant differences in optical compositions and sources occurred between the POM and DOM. The temporal-spatial distribution of the fluorescence indices suggested that the POM in Lake Taihu was mainly from autochthonous sources, but more exogenous characteristics were shown in POM in the river mouths compared with other regions. The chromophoric DOM in Lake Taihu mainly displayed autochthonous characteristics. The POM-DOM PARAFAC model was used to examine OM optical composition and five components were identified, which contained three protein-like components (C1, C2, and C5), a microbial humic-like component (C3), and a terrestrial humic-like component (C4). The POM was dominated by C5 in summer and autumn and C3 in winter and spring, and the DOM was dominated by protein-like components (C1, C2, and C5) through the entire year. The algae-dominated region had a relative higher contribution of tryptophan-like components of POM compared with the macrophyte-dominated region. A conceptual model based on the theory of "four phases of cyanobacteria bloom development" was proposed to fully describe the relationship between POM-DOM exchanges and cyanobacteria bloom development.

Using dissolved organic matter fluorescence to identify the provenance of nutrients in a lowland catchment; the River Thames, England

Catchment based solutions are being sought to mitigate water quality pressures and achieve multiple benefits but their success depends on a sound understanding of catchment functioning. Novel approaches to monitoring and data analysis are urgently needed. In this paper we explore the potential of river water fluorescence at the catchment scale in understanding nutrient concentrations, sources and pathways. Data were collected from across the River Thames basin from January 2012 to March 2015.Analysing emission excitation matrices (EEMs) using both PARAFAC and optimal area averaging produced consistent results for humic-like component 1 and tryptophan-like component 4 in the absence of a subset of samples that exhibited an unusual peak; illustrating the importance of inspecting the entire EEM before using peak averaging methods. Strong relationships between fluorescence components and dissolved organic carbon (DOC), soluble reactive phosphorus (SRP), and ammonium clearly demonstrated its potential, in this study basin, as a field based surrogate for nutrients. Analysing relationships between fluorescence, catchment characteristics and boron from across the basin enabled new insights into the provenance of nutrients. These include evidence for diffuse sources of DOC from near surface hydrological pathways (i.e. soil horizons); point source inputs of nutrients from sewage effluent discharges; and diffuse contributions of nutrients from agriculture and/or sewage (e.g. septic tanks).The information gained by broad scale catchment wide monitoring of fluorescence could support catchment managers in (a) prioritising subcatchments for nutrient mitigation; (b) providing information on relative nutrient source contributions; and (c) providing evidence of the effectiveness of investment in pollution mitigation measures. The collection of high resolution fluorescence data at the catchment scale and, in particular, over shorter event timescales would complement broad scale assessments by enhancing our hydro-biogeochemical process understanding.

Terrestrial humic-like fluorescence peak of chromophoric dissolved organic matter as a new potential indicator tracing the antibiotics in typical polluted watershed

Natural surface waters are threatened globally by antibiotics pollution. In this study, we analyzed antibiotics and CDOM (Chromophoric dissolved organic matter) fluorescence in different water bodies using HPLC method and Excitation Emission Matrix- Parallel factor analysis, respectively. A combination of field studies in the Yinma River Watershed were conducted in rivers, reservoirs and urban rivers, and 65 CDOM and antibiotic samples were taken in April, May, July, and August 2016. EEM-PARAFAC analysis identified two components; a humic-like (C1) component and a tryptophan-like (C2) component. The redundancy analysis (RDA) demonstrated that CDOM could explain 38.2% (two axes) of the five antibiotics in reservoirs (N = 31), and 26.0% (two axes) of those in rivers and urban water (N = 30). Furthermore, the Pearson correlation coefficient between Sulfamethoxazole and C1 in reservoir water was 0.91 (t-test, 2-tailed, p < 0.01), and that between Sulfamethoxazole and C2 was 0.68 (t-test, 2-tailed, p < 0.01). This indicated that the humic-like component of CDOM PARAFAC fluorescence could detect Sulfamethoxazole contamination levels in the homogenized reservoir waters. Our results identified Sulfamethoxazole and Quinolones (Norfloxacin, 16.5 ng L−1; Enrofloxacin, 0.3 ng L−1; Ciprofloxacin, 30.9 ng L−1) at mean concentrations of 369.5 ng L−1 and 15.9 ng L−1, respectively, which were the higher levels in natural surface waters. The FTIR spectroscopy of the mixture of humic acid and sulfamethoxazole showed that the absorbance at 3415 cm−1 linked to OH stretching of OH groups and at 1386 cm−1 because of OH bending and vibration of COOH groups became weaker, indicating that COOH groups of humic acid can adsorb and react with –NH2 of sulfamethoxazole. The CDOM PARAFAC components can be adapted for online or in situ fluorescence measurements as an early warning of Sulfamethoxazole distribution and contamination in similar aquatic environments.

Composition, Spatial Distribution Characteristics and Source Analysis of Chromophoric Dissolved Organic Matter in the Lanzhou Reach of the Yellow River

Chromophoric dissolved organic matter (CDOM) in riverine systems can be affected by environmental conditions and land-use, and can thus provide important information regarding anthropogenic activities in surrounding landscapes. It can modify the optical properties of waters and affect the balance and availability of dissolved nutrients and metals in water bodies. However, the characteristics of CDOM in the Lanzhou reach of the Yellow River have not yet been reported. In this study, the optical properties of water samples collected at 32 locations during April 2017 across the Lanzhou reach of the Yellow River were examined using UV-VIS and excitation-emission matrix fluorescence spectroscopy-parallel factor analysis (EEM-PARAFAC), to determine CDOM compositional changes, spatial distribution characteristics, and sources. Cluster analysis was used to categorize samples into groups of similar pollution levels within a study area. Results showed that CDOM was primarily comprised of low molecular weight organic substances with aromatic structure belonging to complex "protein-like-humic-like" substances, and dominated by protein-like substances (organism sources). Two humic-like components (C1, C4), one tryptophan-like component (C2), and one non-humic-like component (C3) were identified by PARAFAC. Tryptophan-like substances were predominant in the components of CDOM, accounting for 51.06% of average total fluorescence intensity. Humic-like materials and non-humic-like substances accounted for 36.74% and 12.20%, respectively. Weak correlations were observed between protein-like substances and humic-like substances, indicating different sources of these components. The distribution of total fluorescence intensity showed a distinct spatial pattern; trends in fluorescence intensity were weak-strong-weak along an upstream to downstream continuum, mainly affected by changes in the content of protein-like substances. The spatial variation of the CDOM in the Lanzhou reach of the Yellow River can therefore be assessed based on protein-like materials dynamics. Public spaces along rivers offer opportunities for community gatherings and recreational activities. However, high-intensity anthropogenic activities strongly influence CDOM concentration and composition in this area in different ways; sources include increased residential/commercial wastewater, catering, water recreation facilities pollution, shipping, and a small amount of industrial discharge. In addition, it was concluded that endogenetic pollution may become the main source of internal loading in the Lanzhou reach of the Yellow River, implying that stronger endogenetic pollution control is needed to alleviate CDOM pollution and improve water quality.

Evaluation of CDOM sources and their links with antibiotics in the rivers dividing China and North Korea using fluorescence spectroscopy.

Rivers act as carriers where active cycling of chromophoric dissolved organic matter (CDOM) affected by anthropogenic activities and land cover variation may occur. Little is known about the optical properties of CDOM in relation to antibiotics; these properties could provide valuable insights into CDOM transformation processes and biogeochemical reactivity. The spatial distribution of CDOM absorption, fluorescence intensities of CDOM components, and correlations between fluorescence indices (FI370, humification index (HIX)) and biological index (BIX)) with water quality and antibiotics were investigated in three rivers, namely, two rivers (Yalu River and Tumen River) dividing China and North Korea, and the Songhua River. Four humic-like components (C1 and C3-5), and one tryptophan-like component (C2), were identified via fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC). The correlation between Fmax for five EEM-PARAFAC extracted CDOM components, C1-C5, FI370, HIX, BIX, and water quality parameters, and four antibiotics (i.e., Norfloxacin, Enrofloxacin, Sulfamethoxazole and Metronidazole), were determined through a redundancy analysis (RDA), with species-environment correlations of 0.887 and 0.833, respectively. The results showed that spatial variation in land cover, pollution sources, and terrestrial contribution in water quality affected Fmax for the fluorescent components C1-C5 and the fluorescence indices, indicating a high diverse chemical composition and transformation history. The Fmax for terrestrial humic-like components, C4 and C5, showed spatial variation depending on land cover and anthropogenic impacts. Further correlation and regression analyses indicated that CDOM soil fulvic-like component C5 correlated with Sulfamethoxazole and Metronidazole (t test, p < 0.01). Our results indicate that the spatial distributions of Fmax for CDOM fluorescent terrestrial components, evaluated by EEM-PARAFAC, have potential implications for the monitoring of Sulfamethoxazole and Metronidazole in surface waters. Further, these findings can be used to understand the biogeochemical cycling of CDOM and its effects on antibiotics pollution in the environment.

Seasonal Variations of Dissolved Organic Matter in the East China Sea Using EEM-PARAFAC and Implications for Carbon and Nutrient Cycling

Dissolved organic matter (DOM) plays a very important role in the dynamics of different biogeochemical processes in the global marine carbon cycle. Seasonal variations of DOM were investigated using dissolved organic carbon (DOC), absorption spectroscopy, and fluorescence excitation emission matrix–parallel factor analysis (EEM-PARAFAC) in Niushan Island in the East China Sea, off southeast Zhejiang, in winter, spring, and summer 2017. A strong positive correlation between temperature and salinity was observed in winter, whereas negative correlations were obtained in spring and summer. The results suggest that the water in the study area originates from the Changjiang River water coinciding with the direction of winds in winter. On the other hand, the Taiwan Strait water flows northward on the eastern part of the study area in summer and spring. The DOC concentration showed significant seasonal variations and was much lower in summer than in winter, but largely independent of the temperature, degree of absorption and intensity of the fluorescence component. Three tryptophan-like components (C1, C2 and C4) and one humic-like component were identified by the PARAFAC model in winter, while two tryptophan-like components (C1 and C2) and two humic-like components were illustrated in summer. The seasonal variations of DOC concentrations and intensities of the fluorescence components in the study area from winter to summer suggest that the waters in this area were influenced mainly by mixing water of the Changjiang River and the Taiwan Strait. A strongly linear relationship was found between the nutrient and the fluorescence intensities of different components in winter, reflecting the profound impacts of the dynamics of DOM on nutrient cycling.

Fluorescent characteristic and compositional change of dissolved organic matter and its effect on heavy metal distribution in composting leachates.

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.

Seasonal and downstream alterations of dissolved organic matter and dissolved inorganic ions in a human-impacted mountainous tributary of the Yellow River, China.

Human activities impose important disturbances on both organic and inorganic chemistry in fluvial systems. In this study, we investigated the intra-annual and downstream variations of dissolved organic carbon (DOC), dissolved organic matter (DOM) excitation-emission matrix fluorescence (EEM) with parallel factor analysis (PARAFAC), major ions, and dissolved inorganic nitrogen (DIN) species in a mountainous tributary of the Yellow River, China. Both DOM quantity and quality, as represented by DOC and DOM fluorescence respectively, changed spatially and seasonally in the studied region. Fluorescence intensity of tryptophan-like components (C3) were found much higher at the populated downstream regions than in the undisturbed forested upstream regions. Seasonally, stronger fluorescence intensity of protein-like components (C3 and C4) was observed in the low-flow period (December) and in the medium-flow period (March) than in the high-flow period (May), particularly for the downstream reaches, reflecting the dominant impacts of wastewater pollution in the downstream regions. In contrast to the protein-like fluorescence, humic-like fluorescence components C1 and C2 exhibited distinctly higher intensity in the high-flow period with smaller spatial variation indicating strong flushing effect of increasing water discharge on terrestrial-sourced humic-like materials in the high-flow period. Pollution-affected dissolved inorganic ions, particularly Na+, Cl-, and NH4+-N, showed similar spatial and seasonal variations with protein-like fluorescence of DOM. The significant positive correlations between protein-like fluorescence of DOM and pollution-affected ions, particularly Na+, Cl-, and NH4+-N, suggested that there were similar pollution sources and transportation pathways of both inorganic and organic pollutants in the region. The combination of DOM fluorescence properties and inorganic ions could provide an important reference for the pollution source characterization and river basin management.

Differences in fluorescence characteristics and bioavailability of water-soluble organic matter (WSOM) in sediments and suspended solids in Lihu Lake, China.

The spectral characteristics, spatial distribution, and bioavailability of water-soluble organic matter (WSOM) in suspended solids and surface sediments of Lihu Lake, China, were investigated through excitation-emission matrix spectra and parallel factor analysis. The average content of dissolved organic carbon (DOC) in the sediments reached 643.28 ± 58.34mg C/kg and that in suspended solids was 714.87 ± 69.24mg C/kg. The fluorescence intensity of WSOM totaled 90.87± 5.65 and 115.42 ± 8.02 RU/g for the sediments and suspended solids, respectively. The DOC and fluorescence intensity of the WSOM showed an increasing trend moving from the west to the east of the lake. The WSOM in sediments and suspended solids contained two humic-like (C1 and C2) and one tryptophan-like (C3) components. These components had different fluorescent peaks and relative proportions. In the sediments, the relative proportions of C1, C2, and C3 were 33.71% ± 0.71, 26.83% ± 0.68, and 39.50% ± 0.71%, respectively. Meanwhile, C1 (35.77 ± 0.84%), C2 (34.07 ± 0.61%), and C3 (30.16 ± 0.75%) had similar relative percentages in suspended solids. The sediments had a lower humification index (3.02 ± 0.08) than the suspended solids (4.04 ± 0.15). Exchangeable nitrogen for the sediments and suspended solids was dominated by exchangeable ammonium nitrogen and soluble organic nitrogen, respectively. WSOM plays an important role in migration and transformation of nitrogen in sediments and suspended solids. The sediment-derived WSOM exhibited higher lability and biological activity than did the suspended solid-derived WSOM. The relative ratio of the intensity of protein-like fluorescent component to that of the humic-like one can be used as a reference index to evaluate the lability and biological activity of WSOM in sediments and suspended solids.

Changes in spectroscopic signatures in soluble microbial products of activated sludge under different osmotic stress conditions

Spectroscopic techniques were used to examine the subtle changes in soluble microbial products (SMP) of batch activated sludge bioreactors working at different salinities (i.e., 0%, 1%, 3%, and 5% NaCl). The changes in different fluorescent constituent were tracked by excitation-emission matrix combined with parallel factor analysis (EEM-PARAFAC), and the sequential production was further identified by two-dimensional correlation spectroscopy (2D-COS). Greater enrichment of tryptophan-like component and large-sized biopolymer were found in SMP for higher saline bioreactors, suggesting the SMP sources from bound extracellular polymeric substances and excreted intercellular constituents. 2D-COS revealed the opposite sequences of the fluorescence changes in SMP between the low and the high saline bioreactors, following the order of “tyrosine-like > tryptophan-like > humic-like fluorescence” for the latter. This study clarified the dominant mechanisms involved in SMP formation during elevating salinity, which were well supported by the changes in SMP spectroscopic features, microbial activity, and organic degradation rates.

Effects of COD/N ratio on soluble microbial products in effluent from sequencing batch reactors and subsequent membrane fouling

The relative ratios of chemical oxygen demand (COD) to nitrogen (N) in wastewater are known to have profound effects on the characteristics of soluble microbial products (SMP) from activated sludge. In this study, the changes in the SMP characteristics upon different COD/N ratios and the subsequent effects on ultrafiltration (UF) membrane fouling potentials were examined in sequencing batch reactors (SBR) using excitation emission matrix-parallel factor analysis (EEM-PARAFAC) and size exclusion chromatography (SEC). Three unique fluorescent components were identified from the SMP samples in the bioreactors operated at the COD/N ratios of 100/10 (N rich), 100/5 (N medium), and 100/2 (N deficient). The tryptophan-like component (C1) was the most depleted at the N medium condition. Fulvic-like (C2) and humic-like (C3) components were more abundant with N rich wastewater. Greater abundances of large size biopolymer (BP) and low molecular weight neutrals (LMWN) were found under the N deficient and N rich conditions, respectively. SMPs from various COD/N exhibited a greater degree on membrane fouling following the order of 100/2 > 100/10 > 100/5. C1 and C2 had close associations with reversible and irreversible fouling, respectively, while the reversible fouling potential of C3 depended on the COD/N ratios. No significant impact of COD/N ratio was observed on the relative contributions of SMP size fractions to either reversible or irreversible fouling potential. However, the COD/N ratios likely altered the BP foulants' composition with greater contribution of proteinaceous substances to reversible fouling under the N deficient condition than at other N richer conditions. The opposite trend was observed for irreversible fouling. Our results provided further insight into changes in different SMP constitutes and their membrane fouling in response to microbial activities under different COD/N ratios.

Impacts of cyanobacterial blooms outbreak and decline on chromophoric dissolved organic matter in Lake Taihu

利用平行因子分析（PARAFAC）技术对藻华暴发季节太湖梅梁湾和开敞区水样中有色可溶性有机物（CDOM）的三维荧光光谱进行分析，获得代表类酪氨酸、类色氨酸和类腐殖酸等3种荧光组分，这3个组分的荧光得分值均与叶绿素a浓度呈极显著正相关，其中类腐殖酸物质荧光得分值占总分值的比例也与叶绿素a浓度极显著正相关，由此可以推测，蓝藻水华可能是太湖CDOM的一个重要来源，并极大地影响了湖泊CDOM的组成结构.为进一步探索蓝藻水华对湖泊CDOM的影响，于太湖梅梁湾湖岸进行藻华暴发和衰亡模拟试验.PARAFAC结果显示，模拟试验水样CDOM的三维荧光图谱同样含有3个组分，其中类酪氨酸和类色氨酸荧光峰位置与湖泊水样基本相同，而类腐殖酸物质荧光峰则有一定程度的蓝移，表明培养试验中有新的内源类腐殖酸物质产生.利用PARAFAC模型中的得分值计算后发现，初始叶绿素a浓度越高，类腐殖酸物质所占比例越大，而实验结束时添加了高浓度和中等浓度藻的2个处理中类腐殖酸物质对荧光的贡献率也有显著提高.因此，藻华的长期暴发可以显著改变湖泊CDOM的组成，导致类腐殖酸物质比例提高.;Parallel Factor Analysis (PARAFAC) was applied to assess the composition of chromophoric dissolved organic matter (CDOM) from the excitation-emission matrix (EEM) fluorescence spectra of the water samples collected from Meiliang Bay and the open area in Lake Taihu during a cyanobacterial bloom event, and three fluorescent components were identified:a tyrosine-like component, a tryptophan-like component and a humic-like component. Correlation analysis showed that the concentrations of chlorophyll-a(Chl.a) were significantly correlated with the fluorescence intensities of the three components, respectively, as well as the proportion of humic-like to total fluorescence intensities, suggesting that cyanobacteria might be an important source of CDOM and can greatly change the composition of CDOM in Lake Taihu. For further investigation, a simulation experiment was performed on the shore of Meiliang Bay. PARAFAC model showed that the number of components and the spectral characteristics of CDOM EEM data from the simulation experiment are similar in terms of the number of fluorescence peaks and their position to previously identified components in the water samples from Lake Taihu, except that the fluorescence peaks of humic acids showed a certain degree of blue shift, which suggested that endogenous humic substances were produced during the simulation experiment. It was found that the higher initial concentrations of Chl.a, the greater contribution of humic acids to total CDOM fluorescence intensity derived by the PARAFAC model. Moreover, at the end of the experiment, the ratios of humic substances to total fluorescent substances increased significantly in the two treatments with relatively high concentrations of cyanobacteria. Thus, the long-term outbreak of cyanobacterial blooms can significantly alter the composition of the CDOM in lakes, resulting in an increase of the proportion of humic-like substances.

Aerobic Biodegradation Characteristic of Different Water-Soluble Azo Dyes.

This study investigated the biodegradation performance and characteristics of Sudan I and Acid Orange 7 (AO7) to improve the biological dye removal efficiency in wastewater and optimize the treatment process. The dyes with different water-solubility and similar molecular structure were biologically treated under aerobic condition in parallel continuous-flow mixed stirred reactors. The biophase analysis using microscopic examination suggested that the removal process of the two azo dyes is different. Removal of Sudan I was through biosorption, since it easily assembled and adsorbed on the surface of zoogloea due to its insolubility, while AO7 was biodegraded incompletely and bioconverted, the AO7 molecule was decomposed to benzene series and inorganic ions, since it could reach the interior area of zoogloea due to the low oxidation-reduction potential conditions and corresponding anaerobic microorganisms. The transformation of NH3-N, SO42− together with the presence of tryptophan-like components confirm that AO7 can be decomposed to non-toxic products in an aerobic bioreactor. This study provides a theoretical basis for the use of biosorption or biodegradation mechanisms for the treatment of different azo dyes in wastewater.

Composition of Extracellular and Intracellular Polymeric Substances Produced by Scenedesmus and Microcystis

Abstract Algal extracellular and intracellular polymeric substances (EPS and IPS) are widely applied in fields such as food, cosmetics, and wastewater treatment. Algal IPS content was much higher than EPS and thus extracting IPS from algal biomass may greatly improve the commercial value of algal cultivation. This study was to provide a basis for development of algal IPS by comparing composition of algal IPS and EPS. EPS and IPS produced by Scenedesmus and Microcystis, which commonly dominates the freshwater ecosystems, were analyzed using fluorescence excitation-emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC). The IPS concentration of Scenedesmus obliquus and Microcystis aeruginosa was 1.2 to 2.1 times higher than EPS concentration. The maximum EPS concentration was 145.7 mg C/L but the maximum IPS concentration reached 206.1 mg C/L. Seven components including five humic-like components (C1, C2, C3, C4, and C7) and two tryptophan-like component (C5 and C6) were identifie...