Assessing the environmental impact of phenanthrene in different types of land use based on the binding characteristics with dissolved organic matter.

The binding characteristics of phenanthrene with dissolved organic matter (DOM) were studied by the excitation emission matrix fluorescence spectroscopy with parallel factor analysis in four types of land use which derived from forest (F), meadow (M), cropland (C), and greenhouse (G). The results showed that the humification degree and binding characteristics of phenanthrene with DOM were distinct differences in the four soils. The binding capacities of humic-like components with phenanthrene were stronger than those of protein-like components. The log K derived from the Stern-Volmer equation significantly correlated with the humification degree of DOM (p < 0.05) in different types of land use. Besides, correlation analysis demonstrated that the potential binding index (Fk) obtained from the modified Stern-Volmer model was a more accurate parameter to describe the combination degree of DOM with phenanthrene than log K, which presented a decrease order of C > F > M > G. Therefore, the environmental impact of phenanthrene in different types of land use could be assessed deeply based on the Fk and DOM concentration.

Characterization of atrazine binding to dissolved organic matter of soil under different types of land use.

Atrazine is widely used in agriculture. In this study, dissolved organic matter (DOM) from soils under four types of land use (forest (F), meadow (M), cropland (C) and wetland (W)) was used to investigate the binding characteristics of atrazine. Fluorescence excitation-emission matrix-parallel factor (EEM-PARAFAC) analysis, two-dimensional correlation spectroscopy (2D-COS) and Stern-Volmer model were combined to explore the complexation between DOM and atrazine. The EEM-PARAFAC indicated that DOM from different sources had different structures, and humic-like components had more obvious quenching effects than protein-like components. The Stern-Volmer model combined with correlation analysis showed that log K values of PARAFAC components had a significant correlation with the humification of DOM, especially for C3 component, and they were all in the same order as follows: meadow soil (5.68)>wetland soil (5.44)>cropland soil (5.35)>forest soil (5.04). The 2D-COS further confirmed that humic-like components firstly combined with atrazine followed by protein-like components. These findings suggest that DOM components can significantly influence the bioavailability, mobility and migration of atrazine in different land uses.

Novel method of vulnerability assessment of simple landfills area using the multimedia, multipathway and multireceptor risk assessment (3MRA) model, China.

Vulnerability assessment of simple landfills was conducted using the multimedia, multipathway and multireceptor risk assessment (3MRA) model for the first time in China. The minimum safe threshold of six contaminants (benzene, arsenic (As), cadmium (Cd), hexavalent chromium [Cr(VI)], divalent mercury [Hg(II)] and divalent nickel [Ni(II)]) in landfill and waste pile models were calculated by the 3MRA model. Furthermore, the vulnerability indexes of the six contaminants were predicted based on the model calculation. The results showed that the order of health risk vulnerability index was As > Hg(II) > Cr(VI) > benzene > Cd > Ni(II) in the landfill model, whereas the ecology risk vulnerability index was in the order of As > Hg(II) > Cr(VI) > Cd > benzene > Ni(II). In the waste pile model, the order of health risk vulnerability index was benzene > Hg(II) > Cr(VI) > As > Cd and Ni(II), whereas the ecology risk vulnerability index was in the order of Hg(II) > Cd > Cr(VI) > As > benzene > Ni(II). These results indicated that As, Hg(II) and Cr(VI) were the high risk contaminants for the case of a simple landfill in China; the concentration of these in soil and groundwater around the simple landfill should be strictly monitored, and proper mediation is also recommended for simple landfills with a high concentration of contaminants.

[Influence of the Composition of the Initial Mixtures on the Physicochemical and Biological Properties and Spectral Characteristics of Composts].

In this work, biogas residues, the remnant of the anaerobic digestion, was used for composting with livestock manure as the co-substrate. It is important for improving the soil quality in China, because the negative influence of biogas residues being utilized directly as organic fertilizer (a mainstream way of disposing biogas residues in China) on the soil could be eliminated or mitigated via composting. The composition of composting substrate has a great influence on the composting process. To explore the influence of the composition of the initial mixtures on the physicochemical properties and spectroscopic characteristics of composts, fifteen co-composting of biogas residue, pig manure and chicken manure, with different material ratios, were carried out. Physicochemical and biological indicators were determined. Meanwhile, spectroscopic methods, such as UV-Vis, synchronous fluorescence and 3D-EEM spectra were used for identifying characteristic spectral parameters companied with FRI and PARAFAC. Therefore, spectroscopic characteristics of composts were characterized. The relationship between physicochemical properties of composts and the composition of the initial mixtures was established using CCA. Similarly, that between spectroscopic characteristics of composts and the composition of the initial mixtures was also established. The results showed that: physicochemical properties of composts exhibits a significant correlation with the composition of the initial mixtures. A significant correlation between spectroscopic characteristics of composts and the composition of the initial mixtures was also observed. In the two CCA, the former four axes account for 83.9% and 97.5% of the total sample variation. The influence of enviro nmental factors on physicochemical properties of composts was in the order of pig manure amount>chicken manure amount>biogas residue amount and that on spectroscopic characteristics of composts was in the order of biogas residue amount>pig manure amount>chicken manure amount. Carbon-rich raw materials favor the maturation of compost. A high proportion of nitrogen-rich raw materials does not lead to the accumulation of ammonia in compost. A low proportion of biogas residue favors the formation of humic substances during the co-composting of biogas residue and livestock manure. In summary, the evaluation of compost fermentation effect should synthetically consider physic-chemical, biological indicators and spectral parameters instead of a single index.

Assessment of the Fluorescence Spectra Characteristics of Dissolved Organic Matter Derived from Organic Waste Composting Based on Projection Pursuit Classification (PPC).

The characteristics of fluorescence spectra of dissolved organic matter (DOM) derived from composting is one of the key ways to assess the compost maturity. However, the existing methods mainly focus on the qualitative description for the humification degree of compost. In this paper, projection pursuit classification (PPC) was conducted to quantitative assess the grades of compost maturity, based on the characteristics of fluorescence spectra of DOM. Eight organic wastes (chicken manure, swine manure, kitchen waste, lawn waste, fruits and vegetables waste, straw, green waste, and municipal solid waste) composting were conducted, the germination percentage (GI) and fluorescence spectra of DOM were measured during composting. Statistic analysis with all fluorescence parameters of DOM indicated that I436/I383 (a ratio between the fluorescence intensities at 436 and 383 nm in excitation spectra), FLR (an area ratio between fulvic-like region from 308 to 363 nm and total region in emission spectra), P(HA/Pro) (a regional integration ratio between humic acid-like region to protein-like region in excitation emission matrix (EEM) spectra), A4/A1 (an area ratio of the last quarter to the first quarter in emission spectra), r(A,C) (a ratio between the fluorescence intensities of peak A and peak C in EEM spectra) were correlated with each other (p < 0.01), suggesting that this fluorescence parameters could be considered as comprehensive evaluation index system of PPC. Subsequently, the four degrades of compost maturity included the best degree of maturity (I, GI > 80%), better degree of compost maturity (II, 60% < GI < 80%), maturity (III, 50% < GI < 60%), and immaturity (IV, GI < 50%) were divided according the GI value during composting. The corresponding fluorescence parameter values were calculated at each degrade of compost maturity. Then the projection values were calculated based on PPC considering the above fluorescence parameter values. The projection value was 2.01 - 2.22 for I grade, 1.21 - 2.0 for II grade, 0.57 - 1.2 for III grade, and 0.10 - 0.56 for IV grade. Model validation was then carried out with composts samples, the results indicated that the simulated values were agreed with the observed values, and the accuracy of PPC was 75% for four grades of maturity, and 100% for maturity and immaturity, suggesting that PPC could meet the need of the assessment of compost maturity.

[Using UV-Vis Absorbance for Characterization of Maturity in Composting Process with Different Materials].

The present study was conducted to assess the degree of humification in DOM during composting using different raw materials, and their effect on maturity of compost based on UV-Vis spectra measurements and chemometrics method. The raw materials of composting studied included chicken manure, pig manure, kitchen waste, lawn waste, fruits and vegetables waste, straw waste, green waste, sludge, and municipal solid waste. During composting, the parameters of UV-Vis spectra of DOM, including SUVA254 , SUVA280 , E250/E365, E4/E6, E2/E4, E2/E6, E253/E203, E253/E220, A226-400, S275-295 and S350-400 were calculated, Statistical analysis indicated that all the parameter were significantly changed during composting. SUVA254 and SUVA280 of DOM were continuously increased, E250/E365 and E4/E6 were continuously decreased in DOM, while A226-400, S275-295 and S350-400 of DOM at the final stage were significantly different with those at other stages of composting. Correlation analysis indicated that the parameters were significantly correlated with each other except for E2/E4 and E235/E203. Furthermore, principal component analysis suggested that A226-400, SUVA254, S350-400, SUVA280 and S275~295 were reasonable parameters for assessing the compost maturity. To distinguish maturity degree among different composts, hierarchical cluster analysis, an integrated tool utilizing multiple UV-Vis parameters, was performed based on the data (A226-400, SUVA254, S350-400, SUVA280 and S275-295) of DOM derived from the final stage of composting. Composts from different sources were clustered into 2 groups. The first group included chicken manure, pig manure, lawn waste, fruits and vegetables waste, green waste, sludge, and municipal solid waste characterized by a lower maturity degree, and the second group contained straw waste and kitchen waste associated with a higher maturity degree. The above results suggest that a multi-index of UV-Vis spectra could accurately evaluate the compost maturity, and A226-400, SUVA254, S350-400, SUVA280 and S275-295 of DOM could serve as primary parameters when the compost maturity was assessed using UV-Vis spectra.

[Studies on fluorescence spectral characteristics of fulvic acid (FA) from Xingkai Lake sediments].

Four samples (sample No. HXXD, HXXX, HXDX and HXDB) were taken from Xingkai Lake Sediments in Heilongjiang province and fluorescence spectral characteristics of Fulvic acid (FA) from sediments were studied. Conventional and excitation-emission matrix (EEM) all indicated that FA from HXXD sediment exhibited primary peaks at longer wavelengths. The analysis of fluorescence characteristic parameters indicated that the degree of humification of FA from all sample points were in the order: HXXD > HXDX > HXDB > HXXX. Fluorescence index (f450/500) suggested that FA from HXXD mainly originated from terrestrial sources, while the FA from other samples mainly originated from aquatic organism sources and terrestrial sources. Based on EEM fluorescence regional integration (FIR), the percent fluorescence responses (P(i, n)) of five regions in 3EEMs was calculated. The distributions of P(V, n) (humic acid-like region) and P(III, n) (fulvic acid-like region) were the largest in all samples. The conclusion of the degree of humification of FA based on FIR was consistent with the analysis of conventional fluorescence parameters. The correlation analysis showed that, gamma(A, C) was significantly correlative with P(V, n)/P(III, n), (P(V, n) + P(III, n))/(P(I, n) + P(II, n) + P(III, n)) and P(V, n). The results suggest that gamma(A, C) index is a reasonable tool for assessing humification degree of FA from Xingkai Lake sediments.

The composition and mercury complexation characteristics of dissolved organic matter in landfill leachates with different ages.

Dissolved organic matter obtained from landfill leachate was separated into hydrophobic acid, base, neutral (HOA, HOB, HON) and hydrophilic (HIM) fractions. Fluorescence excitation-emission matrix spectra and parallel factor analysis were employed to characterize the composition, and fluorescence quenching titration technique was applied to study the complexation between Hg (II) and HON, HOA, and HIM fractions. Protein-like substances, humic-like compounds and xenobiotic organic matters (XOM) were identified in all fractions. The HOA, HOB and HON fractions comprised mainly XOM, while the HIM fraction consisted primarily of humic-like compounds. The complexation ability of protein-like substances was higher than that of humic-like compounds. The complexation ability of the HIM was highest for protein-like substances, while the complexation ability of the HON fraction was the highest for humic-like substances. The results suggested that the toxicity and bioavailability of the mercury in the young leachates was the highest, and decreased with landfill time.

[Fluorescence spectroscopic characteristics of dissolved organic matters (DOM) from Jingpo Lake water].

Six samples (sample J1-J6) from Jingpo Lake in Heilongjiang province were analyzed by fluorescence and fluorescence excitation-emission matrix regional integration (FIR) to determine the different characteristics of dissolved organic matters (DOM). The results with the traditional method just analyzing the excitation, emission and synchronous fluorescence spectra indicated that DOM molecular condensation degree was highest at sample J4 and sample J5, however, the study with the three-dimensional-excitation emission matrix spectra (3EEMs) method showed that the content of protein-like material was higher in sample J6 than others. In the second method, 3EEMs was divided into five regions, among which Region I, Region II, and Region IV were related to protein-like material, Region II was related to fulvic acid-like material, Region V was related to humic acid-like organics, and then these regions were integrated named as A(I), A(II), A(III), A(IV) and A(V). The integration results showed that the volume of A(V) occupied the largest proportion of the DOM region integration from all samples, and it exhibited the most prominent both in sample J4 and sample J5, while it's opposite in sample J6. Integral ratio, which means humic acid-like region (A(III), A(V)) divided by protein-like region(A(I), A(II), A(IV)), showed that the value of J4(4. 94) was close to J5 (5.18), J1 (3.52) was close to J2 (3.66), and the minimum value appeared in J6 (2.11). From the above analysis, the DOM humification degree could be confirmed as follows: J4, J5 > J1, J2 > J3 > J6.

Predicting the humification degree of multiple organic solid waste during composting using a designated bacterial community.

Microbes are the drivers for disposing of organic solid waste (OSW) during aerobic fermentation. Notwithstanding, the significance of microbes is underestimated in numerous studies on aerobic fermentation product assessments. Here, we investigated the humification degree (HD), and the humic acid content was assessed in terms of the bacterial community. The bacterial communities were useful indicators for making predictions and even correctly determined the categories of OSWs with 94% accuracy. The bacterial codes can also provide a better prediction of HD. Our results demonstrate that the bacteria code is a reliable biological method to assess HD effectively. Bacterial codes can be used as ecological and biological indicators to evaluate the quality of aerobic fermentation of different materials.

[Impacts of different inoculation methods on fluorescence characteristics of DOM in solid waste composting].

In order to determine the best inoculation methods of compound microorganisms in solid waste composting, dissolved organic matter (DOM) during the process of composting under five different inoculation methods, including inoculation at the start, at the high-temperature phase, after the high-temperature phase, at the maturity phase and without inoculation, was tested through spectral analysis to investigate the time variations of DOM components in solid waste composting. Fluorescence spec-tra analysis of DOM indicated that the spectral characteristics of DOM in the composting piles of the five treatments exhibited a certain trend with composting time increasing, in which macromolecules with complex structures and humic substances gradually increased, and the heap materials became more and more stabilized. According to the comparisons of the fluorescence spectroscopy maps and related parameters, the treatment of inoculating compound microorganisms at the start time or after the high-temperature phase could notably speed up the humification process in solid waste composting.

[Fluorescence spectroscopic characteristics of fulvic acid from the long-term located fertilization in black soil].

In order to investigate the effect of long-term located fertilization on soil fulvic acid (FA), in this study, four soil samples were taken from black soil with long-term located fertilization (about 30 year) in Harbin, Heilongjiang province. The fertilization treatments included control (CK), N, P and K fertilization (NPK), horse manure (OM), combination of organic manure and chemical fertilizations (MNPK). Soil FA was extracted from the samples and purified. The excitation, emission, synchronous, and three-dimensional-excitation emission matrix fluorescence spectroscopy (3DEEM) characteristics of the FA were determined. The excitation, emission and synchronous scan spectra all indicated that the main peaks of FA in the NPK treatment exhibited a significantly blue shift compared with CK, while those of MNPK, OM treatment caused a red shift to some extent. 3DEEM spectra of FA in all treatments exhibited four peaks (peak a, peak b, peak c, and peak d), compared with FA in CK, the wavelengths shift tendency of peak a, peak b, and peak c of FA 3DEEM in NPK, MNPK and OM treatments were similar to that of traditional spectra in FA. In order to provide quantitative information of FA humification degree in different treatments, we investigated the fluorescence index f450/500 (FI), area integration (A370-600 nm, A1 370-412 nm, A4 538-600 nm). Compared with CK, the f450/500, ratio of A1/A in NPK and A4/A in MNPK treatment increased by 4.62%, 6.12%, 7.22%, respectively. However, the f450/500, the ratio of A1/A in MNPK and A4/A in NPK treatment decreased by 3.86%, 15.31%, and 7.22% respectively. This indicated that NPK application gave a lower degree of FA humification, and combination of organic manure and chemical fertilizations would lead to a greater degree of FA aromatization in black soil with long-term located fertilization than CK.

[Study on solid surface fluorescence characteristic of saline soils around lakes in arid and semiarid regions].

Fluorescence spectroscopy relies on the fluorescence emitted by rigid conjugated systems and thus has been increasingly used to assess the soil organic matter (SOM) humification. This technique is widely applied to solution samples of humic substances, and so far no information exists about its applicability to solid-phase soil samples. Composite soil samples of different depths (0-20, 20-40 and 40-60 cm) were collected from four different halophyte communities along a saline-impact gradient, namely, Comm. Salicornia europaea (CSE), Comm. Suaeda glauca (CSG), Comm. Kalidium foliatum (CKF) and Comm. Sophora alopecuroides (CSA) located around Wuliangsuhai Lake. A humification index based on solid surface fluorescence spectroscopy (HIX(SSF)) was proposed, and compared with conventional humification indices I400/I360, I470/I360, I465/I399 and A4 /Al. There were close positive linear correlations between HIXass and 1400/1360, 145/I399 and A4/A1, but a poor positive linear correlation existed between the HIX(SSF) and I470/I360. The results indicated that HIX(SSF) can be taken as a tool to assess the soil humi fication. The HIX(SSF) of the CSE and CSG varied inappreciably within soil profiles and there was no trend with depth. However the HIX(SSF) varied appreciably in the CKF and CSA, and the HIX(SSF) of the bottom soil profile was higher than that of the other profiles. As a whole, the soil humification degree was low around Wuliangsuhai Lake, and the ecological environment was relatively fragile. The salinity showed a strong negative linear relationship with the I400/I360, I470/I360, I465/I399 and A4/A1, but a good negative linear relationship with the HIX(SSF). The results indicated that the degree of the SOM humification increased with the drop in the salinity. The HIX(SSF) can be an indicator not only of the degree of SOM humification, but also of the process of the salinisation.

[Quantitative fluorescence characterization of organic matter stability during chicken manure composting].

Due to its high sensitivity, good selectivity and nondestructive nature, fluorescence spectroscopy was widely applied to characterize the nature of dissolved organic matter (DOM) from different source since the last decade. In the present study, dissolved organic matter (DOM) extracted from chicken manure samples during composting progress was quantitatively characterized by fluorescence analysis techniques and mathematical analysis methods. The results showed that, the ratio between the fluorescence intensities at 330 nm (humic-like matter) and 280 nm(protein-like matter) (I330/I280) in synchronous-scan excitation mode spectra, the area of a fluorescence spectrum obtained by excitation at the blue wavelength of 465 nm(A470-640), and the ratio between the area of the last quarter (435-480 nm) and the area of the first quarter (300-345 nm) of the emission spectrum (A435-480 nm/A300-345 nm) by exciting the sample with ultraviolet radiation of 240 nm, all increased during composting, and the humification degree of compost increased as well. Three-dimensional excitation emission matrix fluorescence spectroscopy showed that the intensity of protein-like matter decreased during composting progress and diminished at the end, while that of fulvic-like matter increased all the time. The ratio between the intensity of the ultraviolet fulvic-like fluorescence (Peak A) and that of the visible fulvic-like fluorescence gamma (A, C) showed an overall significant downward trend during composting, but fluctuated in the progress. The correlation analysis showed that, I330/I280, A470-640 and A435-480 nm/A300-345 nm were all significant correlative, while gamma (A, C) was not correlative with the above-mentioned three parameters at 0. 05 level due to effect by other factors. The results show that, I330/I280, A470-640 and A435-480 nm/A300-345 nm can be effectively used in the process of the evaluation of humification degree during composting.

[Study on the characteristic UV absorption parameters of dissolved organic matter extracted from chicken manure during composting].

The characteristic parameters obtained from UV-Visible spectra of dissolved organic matter (DOM) during composting were studied in the present paper. The results showed that, during composting progress, the non-humic substances were translated into humus substances, and the aromatization, humification degree and molecular weight of the humus substances increased, while the fatty chains linked with the benzene ring structure were cleavaged into carbonyl, carboxyl and other functional groups. The correlation analysis showed that, when DOM concentration (DOC) from all samples was the same, the specific ultraviolet absorbance values at 254 and 280 nm (SUVA254 and SUVA280, respectively), and the area of a spectrum obtained from 226 to 400 nm (A(226-400)) showed significant positive correlation, furthermore, they were all significantly negatively correlated with the concentration of DOM (DOC), but the correlation between A(226-400) and DOC was the best; The ratio between the absorbance value at 253 nm and that at 203 nm (E253/E203) was significantly correlative with SUVA254, SUVA280 and A 226-400, though the correlation between E253/E203 and DOC was not as good as the other three characteristic parameters; The ratio between the absorbance value at 250 nm and that at 365 nm (E250/E365) and the ratio between the absorbance value at 465 nm and that at 665 nm(E250/E365) were not correlated with the other parameters. The results showed that, the stability of DOM extracted from chicken manure increased during composting, and the complex ability between DOM and heavy metals enhanced as well; A(226-400) reflects the changes of compost maturity best in all UV-Visible spectral absorption parameters studied in this paper.

[Effect of pH on the fluorescence characteristic of dissolved organic matter in landfill leachate].

Due to its high sensitivity, good selectivity and nondestructivity nature, fluorescence technique is suitable to the study of DOM. In the present study, fluorescence characteristics of dissolved organic matter (DOM) from three different ages of landfill leachate (1a, 5a, 10a) under different pH value were investigated. The fluorescence synchronous scan spectroscopy showed that, in addition to the characteristic each age of landfill leachate owned separately, DOM from three ages of landfill leachate shared some common characteristics with the change in pH as follows: the fluorescence peaks of DOM exhibited in synchronous scan spectroscopy from 1 and 5-year-old leachate showed the maximum fluorescence intensity at pH 5, while that of DOM from 10-year-old landfill leachate appeared at pH 12, and the fluorescence intensity of most fluorescence peaks of DOM from 10-year-old landfill leachate exhibited in synchronous scan spectroscopy at pH 4 ranked second. The three-dimensional fluorescence excitation-emission matrix spectroscopy (3DEEM) suggested that the fluorescence intensity of the protein-like peaks of DOM from all three ages of landfill leachate increased with pH value increasing, and the maximum fluorescence occurred at pH 10, while that of DOM from 10-year-old appeared at pH 8; the fluorescence intensity of the visible fulvic-like peaks of DOM from all three ages of landfill leachate was enhanced with pH increasing, and exhibited the maximum fluorescence intensity at pH 10, while the relation curve between the fluorescence intensity of the UV fulvic-like and pH value of DOM from all three year ages of landfill leachate exhibited two peaks, one occurred at pH 4, and the other appeared at pH 10. 3 DEEM also indicated that compared to the fluvic-like matter, the protein-like matter was more easily influenced by pH value. The relation between the r(A,C) value and pH value suggested that the former relied on the latter. If we would compare the r(A,C) values of DOM originating differently, the authors should compare each other under the same pH value.

Parallel faction analysis combined with two-dimensional correlation spectroscopy reveal the characteristics of mercury-composting-derived dissolved organic matter interactions.

Dissolved organic matter (DOM) is regarded as the environmentally friendly substance. Strong complexes could be formed between DOM and heavy metals. Thus, the distribution, bioavailability, toxicity, and fate of heavy metals could be controlled in the environment. The widely spread method for characterizing metal-organic interactions is restricted to combine parallel faction analysis (PARAFAC) with the complexation model. However, a DOM PARAFAC component always contains two or more peaks. Therefore, the traditional method cannot reveal the inner changes of PARAFAC components or whether all the DOM peaks in one PARAFAC component are bound with metal during the metal-organic binding process. In this work, two-dimensional correlation spectroscopy (2DCOS) combined with PARAFAC and the complexation model were employed to reveal the binding speed and ability of different fluorescent peaks from DOM PARAFAC components during the binding process of mercury (Hg2+) to DOM. The results in this study showed that during the Hg2+-DOM binding process, fluorescent peaks in tryptophan-like component all presented Hg2+-binding ability. However, only humic-like component ligands showed Hg2+-binding ability. With these promising results, the true Hg2+ binding rate and ability of different DOM ligands can be revealed, which is helpful for addressing environmental pollution.

[Spectroscopic characterization indicator of landfill in the process of stabilizing].

In the present study, dissolved organic matter (DOM) extracted from landfill of four different ages was studied with fluorescence and ultraviolet-visible spectroscopy in order to explore the possibility of using spectral characteristic changes of DOM as stabilization indicators for landfill. The three-dimensional fluorescence excitation-emission matrix spectroscopy (EEM) displayed that DOM of 0-year-old contained mainly protein-like matter, while DOM extracted from 1, 5 and 10-year-old consisted chiefly of humic matter-like substance, and the intensity change of DOM of 1, 5 and 10-year-old landfill was disordered. Besides, the fluorescence spectroscopy also showed that the r(A,C) value and the fluorescence index f(450/500) of DOM of four different years both decreased with landfill age, which indicated that the low molecular weight fraction of DOM was translated into the high molecular aromatic matter and the degree of humification was enhanced with the time increasing. In addition, the specific ultraviolet-visible absorbance (SUVA) increased with landfill age, which also revealed the law that the degree of humification strengthened with the time increasing, but the change regularity of E4/E6 value of DOM was unconspicuous since the E4/E6 value was easily impacted by some other factors. Therefore, the r(A,C) value, the fluorescence index f(450/500) and the SUVA value of DOM extracted from aged refuse reflected effectively the law of how landfill changed, and could be employed as simple stabilization indicators for aged refuse and closed landfill compartments.

[Fluorescence spectroscopic chracterization of the complexation between mercury(II) and dissolved organic matter].

In this study, conventional fluorescence spectroscopy in the excitation, emission and synchronous scan modes and three-dimensional fluorescence spectroscopy in the form of excitation-emission matrix of fluorescence intensity as a function of excitation and emission wavelengths were applied to study the complexation between DOM extracted from landfill leachates and Hg(II) ions. The emission spectrum of DOM exhibited a broad peak with a center at 425 nm and a disorder change of the peak with increasing Hg(II) concentrations, which suggested that the structure of DOM was comparatively simple and the fluorescence character of DOM-Hg(II) complexes resulted from interaction of all fluorescence groups. The excitation spectrum of DOM showed that the intensities of two peaks at 392 and 458 nm both decreased with the addition of Hg(II), indicating that different sources, hydroxy and amido groups, were all involved in the DOM-Hg(II) complexation process. Synchronous-scan excitation spectra of DOM-Hg(II) complexation showed that Hg(II) not only produced fluorescence quenching effect, but also enhanced the rigid structure of DOM at a low concentration. The three-dimensional fluorescence spectra of DOM-Hg(II) showed that the peaks A and B reduced strongly and the two peaks tended to shift toward longer wavelength with the concentrations of Hg(II) increasing. These results indicated that protein-like matter reacted with Hg(II) and there was a charge-transfer transition either between energy level in its ligand and a mercury energy level or between two mercury energy levels at the same time. Besides, the decrease in fluorescence intensity of peaks C and D in three-dimensional fluorescence spectra suggested that carbonyl and carboxyl formed bonds with Hg(II) when DOM was complexed with Hg(II).

[Study on three-dimensional fluorescence spectroscopy characteristics of humic acid during composting with microbes inoculation].

Composting is one of the municipal solid wastes (MSW) treatment ways. In order to increase composting humification process, in the present study, inoculation microbes were used in MSW composting. The experiment design included RUNck with no microbes inoculation and RUNmic with microbes inoculation. The inoculation microbes were composed of Bacillus casei, Lactobacillus buchneri, Candida rugopelliculosa and Trichoderma. During composting, samples were taken from MSW composting, and humic acid (HA) was extracted from composting and purified, the three-dimensional-excitation emission matrix fluorescence spectroscopy (3DEEM) characteristics and elemental analysis of the HA were determined, and the effect of inoculation microbes on the degree of humification of composting was studied. At initial stage of MSW composting, HA 3DEEM exhibited a peak of fulivc-like at an Ex/Em wavelength pair of 330/440 nm (peak a), and with MSW composting process, the excitation wavelength of peak a shifted from 330 to 350 nm. And a new peak of humic-like reformed nearby an Ex/Em wavelength pair of 390/470 nm (peak b). At 336 h of MSW composting, compared with RUNck (with no micromial inoculation), the fluorescence intensity of peak a (fulivc-like) nearby an Ex/Em wavelength pair of 350/440 in RUNmic (with microbial inoculation) was decreased, while that of peak b (humic-like) nearby an Ex/Em wavelength pair of 390/470 was slightly increased; the excitation and emission wavelength of peak a and peak b all shifted to long wavelengths. Elemental analysis indicated that C/H and O/C of HA molecule in RUNck increased by 9.68% and 10.91% respectively; and those of RUNmic increased by 11.11% and 20.37% at 336 h of MSW composting, respectively. The changes in HA 3DEEM and parameters of elemental analysis occurred in RUNmic at the final stage of composting, because degraded molecules, by the intense microbiological activity during composting, became reorganized to form more condensed compounds, richer in aromatic components. These results all led to the similar conclusion that inoculation microbes composting would accelerate the degree of HA humification, and increase the efficiency of composting.