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.

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.

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.

A novel method for contributing to composting start-up at low temperature by inoculating cold-adapted microbial consortium.

Low temperature climate presented a technical challenge to start-up composting in northern region of China. This study investigated if the cold-adapted microbial consortium (CAMC) could promote composting start-up at low temperature. In this work, the CAMC was inoculated when food waste was composted at 10°C. The results showed that inoculating CAMC accelerated the piles temperature effectively, the piles passed through the start-up period within 37h. Moreover, the inoculants could enhance the abundances of dominant strains related to organic matters degradation rate. Redundancy analysis (RDA) indicated that the relationships among indigenous bacteria, organic substrates degradation and temperature evolution were influenced by the inoculants. Furthermore, the heat generation value and degradation rate of the hydrolysable carbohydrate, lipids and protein were significantly enhanced with CAMC inoculated. This work demonstrated that inoculating CAMC was beneficial to composting self-heating, it provided a novel biotechnology support to ensure the normal start-up of winter composting.

Assessment of phytotoxicity grade during composting based on EEM/PARAFAC combined with projection pursuit regression.

Improper treatment of organic waste may result in environmental pollution and harm to plant growth due to the high concentration of phytotoxin. Composting has widely been used for recycling organic waste and reducing phytotoxin to improve soil properties. Assessing the phytotoxicity grades of compost products is essential for achieving high quality compost to guarantee its marketability. In this study, a technique combined parallel factor (PARAFAC) of excitation-emission matrices (EEMs) spectroscopy with projection pursuit regression (PPR) was applied to improve the sensitivity of phytotoxicity assessment during composting. Results showed that composting reduced the concentration of phytotoxin, and increased the germination index (GI). Composts were divided into four grades based on GI values. Five components containing simple DOM (component C1 and C2) and complex DOM (component C3-C5) were successfully developed by PARAFAC. Correlation analysis between phytotoxicity, chemical indices and fluorescence components demonstrated that C1, C4, complex DOM, and the ratio of simple/complex DOM components were more suitable to assess phytotoxicity of composting products. These results revealed that PARAFAC/PPR enabled a rapid and accurate method to assess the phytotoxicity of compost materials for composting plant.

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.

[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.

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.

[Composition and transformation of leachates during municipal solid waste composting].

The composition and evolution characteristics of inorganic anions, ammonia, heavy metals and organic compounds in leachates with different composing times were studied in a composting plant in order to clarify its composition and evolution and search for a suitable processing technology. The results showed that concentrations of EC, F-, Cl-, SO4(2-) and NH4(+) -N decreased during the composting process, while the contents of NO2(-) -N, NO3(-) -N and Org-N were related to the oxidation reduction atmosphere of leachates. The Pb, Cd, Cu, Zn and As concentrations in leachates exhibited a decrease trend during the composting process, while contents of heavy metals Cr, Ni, Fe, Mn showed an increase trend with increasing composting time. The composting leachate organics comprised mainly of protein-like substance, but also consisted of humic-like substances. The leachate organics were suitable to be treated by biochemical process firstly, and then by physico-chemical technique. The relative content of protein-like substances firstly increased and then decreased, while that of humic-like matter exhibited an opposite trend. The contents of salinity and heavy metal in compost leachates were high, which caused the improper reflux utilization of leachates. The compost leachates should be treated by the combined biochemical and physico-chemical process before emission.

[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.

[Characteristics of organic nitrogen mineralization in organic waste compost-amended soil].

A laboratory aerobic incubation experiment was conducted under a constant temperature to investigate the differentiation rule of nitrogen form among soils amended with different organic wastes composted with food waste, chicken manure, cow manure, domestic waste, vegetable residue, sludge, turf and tomato residue. Experiment utilized soils amended with 0%, 5% and 50% (m/m) of eight organic waste composts. The purpose was to understand the effect of different organic wastes on nitrogen mineralization in soil. This study deals with eight organic waste compost treatments could rapidly increase NH4(+) -N concentrations, reduce the NO3(-)-N concentrations and promote nitrogen mineralization in soil after 3-4 weeks incubation. All parameter tended to be stable. The improved amplitude of the same compost-amended soil: 30% compost treatments > 15% compost treatments > 5% compost treatments. Within the same proportion, chicken manure compost, turf compost and sludge compost product treatments' relative N mineralization was higher than other compost product treatments, and the chicken manure compost treatment's relative N mineralization was significantly higher than other compost product treatments. Food waste compost and vegetable residue compost product treatments' mineralization was low, the lowest was domestic waste compost product treatment. All compost treatments could significantly improve the values of potentially mineralizable nitrogen(N(0)), mineralization rate (k), and promote nitrogen mineralization in soil. The results illustrated that the effect of organic waste compost on the mineralization of nitrogen varied with types of compost and the amount of input compost.

[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.

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.

[Regional heterogeneity of lake eutrophication effects in China].

Although biomass of algae (Chl-a) were in variant levels between different lake regions in China under the same nutrients conditions, it demonstrated that efficiencies of TN/TP used by algae had regional differences. In order to clarify the differences, curve estimation in SPSS was used to analyze the linear relationship between Ig Chl-a and Ig TN/lg TP. The slopes of these linear equations were identified as the efficiencies of TN/TP used by algae. The slopes of linear equations from Mengxin Plateau, Yungui Plateau, Northeast Mountain-Plain, lower reach of Yangtze River Plain and North Plain were 1.002, 0.817, 0.761, 0.545, 0.250, orderly. The efficiencies of TN used by algae ranged from the highest to the lowest were lower reach of Yangtze River Plain, Yungui Plateau, North Plain, Northeast Mountain-Plain, Mengxin Plateau, and the slopes of linear equations were 1.401, 1.058, 0.447, 0.239, 0. 099, respectively. Consequently, in Northeast Mountain-Plain, Mengxin Plateau the efficiencies of TP used by algae were higher than those of TN, and in Yangtze River Plain, Yungui Plateau, North Plain, the efficiencies of TN used by algae were higher than those of TP. On the other hand, in order to describe the effects of algae on transparency in different lakes, the relationships between Chl-a and SD were analyzed. The results showed that in Yungui Plateau the effect of algae on transparency was the most obvious as the variation of SD explained by Chl-a was the highest, and Northeast Mountain-Plain, Mengxin Plateau and North Plain followed. However, in lower reach of Yangtze River Plain, the relationship between Chl-a and SD was not significant.

[Research based on 3MRA model about the risk assessment methods and applications of the landfill waste].

Seven major contaminations of the landfill were selected from northeast of China, and the migration and transformation of contaminations environmental medias were studied by using the multimedia multipathway and multireceptor risk assessment (3MRA) model. The results show, the order of the radical concentration of the seven contaminations is Ni2+ > Benzene > Cd > Pb > Cr6+ > As > Hg. The radical concentration of benzene, As and Hg in human is similar to that of ecology, respectively. The radical concentration of Cd and Ni2+ in human is higher than that of ecology, while the radical concentration of Cr6+ in ecology is higher than that of human. The risk and hazard quotient of the groundwater in the landfill is 5.06 x 10(-7), 2.3 x 10(-1), respectively.

Effect of inoculation methods on the composting efficiency of municipal solid wastes.

Four types of inoculation methods were studied during the composting of municipal solid wastes and dry grass (MSWG). The methods included a control group as well as initial-stage, two-stage, and multi-stage inoculations. Fulvic acids were extracted from the composting materials and characterized by spectroscopic techniques. The results showed that inoculation of microbes in MSWG enhanced the biodegradation of aliphatics, proteins, and polysaccharides. The inoculation also increased the molecular weight, humic- and fulvic-like compound content, as well as humification degree of the composting products. The inoculation of microbes in MSWG significantly improved composting process and efficiency. The improvement efficiency was in the order of initial-stage < two-stage < multi-stage inoculations. Inoculation of microbes based on composting organic matter composition and temperature enhanced composting efficiency.

[Effects of multi-stage strengthening inoculation on bacterial community diversity during composting].

Effects of multi-stage strengthening inoculation on bacterial community diversity were analyzed using PCR-DGGE method in municipal solid waste composting combined with Cluster analysis and changes of Shannon-Weaver index, and the changes of lignocellulose's degradation rate were also detected during the process. The results showed that Multi-stage inoculation of composting can improve the temperature of cooling and the secondary fermentation period. And the hemicellulose, cellulose and lignin degradation rate increased by 7.19%, 10.89% and 8.98% compared to general inoculation composting. The analysis of bacterial community diversity indicated that the diversity index of the two inoculation showed significant differences, the microbial inoculation could live well in the pile. It could avoid competition between different inoculated agents and competition between inoculated and indigenous microorganisms, and could improve bacterial community diversity during composting especially for maturity stage. It could speed up the composting process of stabilization.

[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.