Risk-Based Prioritization Method for the Classification of Groundwater Pollution from Hazardous Waste Landfills.

Hazardous waste landfill sites are a significant source of groundwater pollution. To ensure that these landfills with a significantly high risk of groundwater contamination are properly managed, a risk-based ranking method related to groundwater contamination is needed. In this research, a risk-based prioritization method for the classification of groundwater pollution from hazardous waste landfills was established. The method encompasses five phases, including risk pre-screening, indicator selection, characterization, classification and, lastly, validation. In the risk ranking index system employed here, 14 indicators involving hazardous waste landfills and migration in the vadose zone as well as aquifer were selected. The boundary of each indicator was determined by K-means cluster analysis and the weight of each indicator was calculated by principal component analysis. These methods were applied to 37 hazardous waste landfills in China. The result showed that the risk for groundwater contamination from hazardous waste landfills could be ranked into three classes from low to high risk. In all, 62.2 % of the hazardous waste landfill sites were classified in the low and medium risk classes. The process simulation method and standardized anomalies were used to validate the result of risk ranking; the results were consistent with the simulated results related to the characteristics of contamination. The risk ranking method was feasible, valid and can provide reference data related to risk management for groundwater contamination at hazardous waste landfill sites.

Degradation of toluene-2,4-diamine by persulphate: kinetics, intermediates and degradation pathway.

In this study, the degradation of toluene-2,4-diamine (TDA) by persulphate (PS) in an aqueous solution at near-neutral pH was examined. The result showed that the degradation rate of TDA increased with increasing PS concentrations. The optimal dosage of PS in the reaction system was determined by efficiency indicator (I) coupling in the consumption of PS and decay half-life of TDA. Calculation showed that 0.74 mM of PS was the most effective dosage for TDA degradation, at that level the maximum I of 24.51 was obtained. PS can oxidize TDA for an extended reaction time period. Under neutral condition without activation, four degradation intermediates, 2,4-diamino-3-hydroxy-5-sulfonicacidtoluene, 2,4-diaminobenzaldehyde, 2,4-bis(vinylamino)benzaldehyde and 3,5-diamino-4-hydroxy-2-pentene, were identified by high-performance liquid chromatography-mass spectrometry. The tentative degradation pathway of TDA was proposed as well. It was found that hydroxyl radical played an important role in degradation of TDA with the activation of Fe2+, whereas PS anion and sulphate radicals were responsible for the degradation without activation of Fe2+.

The independent prokaryotic origins of eukaryotic fructose-1, 6-bisphosphatase and sedoheptulose-1, 7-bisphosphatase and the implications of their origins for the evolution of eukaryotic Calvin cycle.

BACKGROUND: In the Calvin cycle of eubacteria, the dephosphorylations of both fructose-1, 6-bisphosphate (FBP) and sedoheptulose-1, 7-bisphosphate (SBP) are catalyzed by the same bifunctional enzyme: fructose-1, 6-bisphosphatase/sedoheptulose-1, 7-bisphosphatase (F/SBPase), while in that of eukaryotic chloroplasts by two distinct enzymes: chloroplastic fructose-1, 6-bisphosphatase (FBPase) and sedoheptulose-1, 7-bisphosphatase (SBPase), respectively. It was proposed that these two eukaryotic enzymes arose from the divergence of a common ancestral eubacterial bifunctional F/SBPase of mitochondrial origin. However, no specific affinity between SBPase and eubacterial FBPase or F/SBPase can be observed in the previous phylogenetic analyses, and it is hard to explain why SBPase and/or F/SBPase are/is absent from most extant nonphotosynthetic eukaryotes according to this scenario. RESULTS: Domain analysis indicated that eubacterial F/SBPase of two different resources contain distinct domains: proteobacterial F/SBPases contain typical FBPase domain, while cyanobacterial F/SBPases possess FBPase_glpX domain. Therefore, like prokaryotic FBPase, eubacterial F/SBPase can also be divided into two evolutionarily distant classes (Class I and II). Phylogenetic analysis based on a much larger taxonomic sampling than previous work revealed that all eukaryotic SBPase cluster together and form a close sister group to the clade of epsilon-proteobacterial Class I FBPase which are gluconeogenesis-specific enzymes, while all eukaryotic chloroplast FBPase group together with eukaryotic cytosolic FBPase and form another distinct clade which then groups with the Class I FBPase of diverse eubacteria. Motif analysis of these enzymes also supports these phylogenetic correlations. CONCLUSIONS: There are two evolutionarily distant classes of eubacterial bifunctional F/SBPase. Eukaryotic FBPase and SBPase do not diverge from either of them but have two independent origins: SBPase share a common ancestor with the gluconeogenesis-specific Class I FBPase of epsilon-proteobacteria (or probably originated from that of the ancestor of epsilon-proteobacteria), while FBPase arise from Class I FBPase of an unknown kind of eubacteria. During the evolution of SBPase from eubacterial Class I FBPase, the SBP-dephosphorylation activity was acquired through the transition "from specialist to generalist". The evolutionary substitution of the endosymbiotic-origin cyanobacterial bifunctional F/SBPase by the two light-regulated substrate-specific enzymes made the regulation of the Calvin cycle more delicate, which contributed to the evolution of eukaryotic photosynthesis and even the entire photosynthetic eukaryotes.

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.

Elemental and spectroscopic methods with chemometric analysis for characterizing composition and transformation of dissolved organic matter during chicken manure composting.

Dissolved organic matter was extracted from chicken manure after 1, 8, 16, 28 and 40 days of composting and characterized by combining elemental and spectroscopic methods with chemometric analysis to investigate the evolution of composting materials. The elemental and spectroscopic analysis results showed that the composting process was characterized by the biodegradation of aliphatics, polysaccharide and proteins, as well as by the synthesis of aromatic structures, humic-like substances and macromolecules. Principal component analysis and correlation analysis indicated that the data from elemental and spectroscopic analysis fell into three main groups, and corresponded to the biodegradation, aromatization, and humification and polymerization state of the composting materials. Hierarchical cluster analysis indicated rapid biodegradation of organic matter during the first eight days, and the formation of aromatic structures, humic-like materials and macromolecules in dissolved organic matter after eight days.

[The remove characteristics of dissolved organic matter in landfill leachate during the treatment process].

In order to investigate remove characteristics of dissolved organic matter in landfill leachate, leachates were sampled during the process (i. e. , adjusting tank, anaerobic zone, oxidation ditch and MBR processing). Dissolved organic matter was extracted and its content and structure were characterized by fluorescence excitation-emission matrix spectra, UV-Vis specrtra and FTIR spectra. The results showed that an amount of 377.6 mg x L(-1) dissolved organic carbon (DOC) was removed during the whole treatment process, and the total removal rate was up to 78.34%. The 25.56% of DOC in the adjusting tank was removed during the anaerobic zone, 41.58% of DOC in anaerobic effluent was removed during the oxidation ditch, while 50.19% of DOC in the oxidation ditch effluent decreased in the MBR process. The anaerobic process increased the content of unsaturated compound and polysaccharides in leachate DOM, which improved the leachate biochemical characteristics. The unsaturated compound and polysaccharides were removed effectively during being in oxidation ditch. Protein-like and humic-like fluorescence peaks were observed in the adjusting tank and anaerobic zone, while humic-like fluorescence peaks were just presented in the oxidation ditch and MBR processing. Protein-like and fulvic-like substances were biodegraded in the adjusting tank and anaerobic zone, while humic-like materials were removed in the MBR process.

[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.

[Different Responses of Soil Microbial Community Structure to Irrigation with Treated Wastewater from Domestic and Industrial Sources].

To investigate the long-term effects of irrigation with treated domestic and industrial wastewater on the microbial community structure of the soil, Illumina MiSeq high-throughput sequencing technology was applied. Groundwater irrigated soil was used as a control. The effects of soil environmental factors and their interactions on the microbial community structure were investigated. Compared with the groundwater irrigation, irrigation with treated domestic wastewater can significantly increase the contents of TOC, DOC, Eh, NH4+-N, and TP, whereas irrigation with treated industrial wastewater can increase the contents of Cd, Cr, Cu, Pb, and Zn in the soil. Irrigation with treated wastewater also increases the relative abundance of Acidobacteria and Planctomycetes, and reduces the relative abundance of Firmicutes and Tectomicrobia. The effects of treated wastewater from different sources on functional microorganisms in soil are also different; irrigation with treated domestic wastewater can increase the relative abundance of Chloroflexi and Nitrospirae, whereas irrigation with treated industrial wastewater has negative effects on the abundance of Actinobacteria. The results of db-RDA analysis show that TN, TP, DOC, and Eh are the main factors that impact the microbial communities in soils irrigated with treated domestic wastewater (P<0.05), and heavy metals are the main factors that impact the microbial communities in soils irrigated with treated industrial wastewater (P<0.05). Compared with groundwater irrigation, treated wastewater irrigation can change the correlations between soil environmental factors, which in turn affect the microbial community structure. The growth of microorganisms in soils irrigated with treated domestic wastewater is mainly controlled by the increase in the nutrients such as DOC, TN, and TP and changes in soil redox conditions. The abundance of microorganisms in soil irrigated with treated industrial wastewater is significantly correlated with the accumulation of heavy metals.

[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.

[Study on fluorescence characteristic of dissolved organic matter from municipal solid waste landfill leachate].

In the present study, the samples of leachate of 0, 5, 10-years-old landfill were respectively taken from landfill plant, the dissolved organic matter (DOM) was extracted from landfill leachate, and the fluorescence spectra of DOM were determined. The fluorescence synchronous scan spectra of DOM in 0-year-old leachate exhibited a primary peak at 335 nm, a secondary peak at 455 nm, and a shoulder peak at 385 nm. While the fluorescence intensities of DOM at different peaks were decreased for 5-year-old leachate, especially those of the peaks at shorter wavelengths (335 and 385 nm) which may be ascribed that the simpler structural components were decreased sharply. Compared with 5-year-old leachate, the fluorescence intensity of DOM in 10-year-old leachate decreased slightly. Three-dimensional excitation emission matrix fluorescence spectra (3DEEM) of DOM in 0-year-old leachate exhibited two peaks at Ex/Em wavelength pairs of 270/355 and 220/350, respectively, which were all associated with protein-derived compounds, while the peaks of protein-like disappeared in 5-year-old leachate, and new peaks of complex structural fulvic acid-like were formed at Ex/Em wavelength pair of 330/412.5 and 250/416.5, respectively. This indicated the component of DOM in the leachate of 5-year-old landfill led to a decrease in low molecular compound, and an increase in high molecular compound compared to that of the 0-year-old. 3DEEM of DOM of 10-year-old leachate was similar to that of DOM in the 5-year-old, but the fluorescence intensity of the peaks of fulvic acid-like in DOM was different, and compared with that of 5-year-old leachate, the peak of DOM in 10-year-old leachate shifted from Ex/Em wavelength pair of 250/416.5 to 250/427.5. This indicated that the DOM formed similar structures, but the structure of fulvic acid-like in DOM of 10-year-old leachate had a greater degree of aromatization and quantity than that of 5-year-old leachate. The results obtained from fluorescence synchronous scan spectroscopy and 3DEEM indicate that aromatic structures of DOM are enriched with the age of landfill leachate.

[Study on dynamic spectral characteristics of humic acid in municipal solid wastes composting].

In the present study, the compost consisted of residual MSW with metal, plastic and glass removed. The composting process was assisted using industrial technology. During the composting, humic acid (HA) was extracted and purified. The spectroscopic characteristics of the HA were determined by using UV, FTIR, and fluorescence spectroscopy. During the composting process, the HA fluorescence spectra exhibited a sharp reduction in relative fluorescence intensity at the short wavelength region, and the primary peak shifted from 335 nm at the initial stage to 458 nm at the final stage of composting, thereby approaching the main peak at 460-480 nm for HA in soil. The FTIR spectra exhibited a reduction in polysaccharides and aliphatic components, and a relative increase in aromatic components; while the HA UV spectra revealed an increase in conjugation and the degree of humification. However, compared with the E4 /E6 value and the spectroscopic characteristics of HA in soil, the HA in the MSW compost has a relatively low molecular weight, a simpler structure and a relatively low degree of aromatic condensation, which also implies that the HA in compost is highly active.

Risk-based prioritization method for the classification of groundwater pesticide pollution from agricultural regions.

Agricultural regions are a significant source of groundwater pesticide pollution. To ensure that agricultural regions with a significantly high risk of groundwater pesticide contamination are properly managed, a risk-based ranking method related to groundwater pesticide contamination is needed. In the present paper, a risk-based prioritization method for the classification of groundwater pesticide pollution from agricultural regions was established. The method encompasses 3 phases, including indicator selection, characterization, and classification. In the risk ranking index system employed here, 17 indicators involving the physicochemical properties, environmental behavior characteristics, pesticide application methods, and inherent vulnerability of groundwater in the agricultural region were selected. The boundary of each indicator was determined using K-means cluster analysis based on a survey of a typical agricultural region and the physical and chemical properties of 300 typical pesticides. The total risk characterization was calculated by multiplying the risk value of each indicator, which could effectively avoid the subjectivity of index weight calculation and identify the main factors associated with the risk. The results indicated that the risk for groundwater pesticide contamination from agriculture in a region could be ranked into 4 classes from low to high risk. This method was applied to an agricultural region in Jiangsu Province, China, and it showed that this region had a relatively high risk for groundwater contamination from pesticides, and that the pesticide application method was the primary factor contributing to the relatively high risk. The risk ranking method was determined to be feasible, valid, and able to provide reference data related to the risk management of groundwater pesticide pollution from agricultural regions. Integr Environ Assess Manag 2017;13:1052-1059. © 2017 SETAC.

[Simulation of nitrate pollution in groundwater using pump-and treat optimization method].

To study the groundwater polluted by nitrate in a landfill site in Beijing, with the pump-and-treat technology, genetic algorithms (GA) and simulated annealing (SA) were used to optimize the cases of 18 planned pumping wells in the groundwater nitrate plume. The optimization method was run to determine the minimum total costs, as a result of the optimal number of wells with the optimal locations and pumping rates. The results of optimization showed that, both GA and SA optimization conditions could reach the desired results, which means that the concentration of nitrate could be reduced to 10 mg x L(-1) after 100 days pumping. However, under the GA optimization conditions, the pumping rates of well 8 and well 14 were 155 m x d(-1) and 10 m3 x d(-1), respectively. In contrast, under the SA optimization conditions, the pumping rate of well 8 was 82 m3 x d(-1), and that of well 14 was 39 m3 x d(-1). Based on the GA and SA optimized pumping rate, the total mass removal rates of nitrate were 76.89% and 84.92%, respectively. The results showed that the best location of the well was in the central axis of either midstream or downstream of the nitrate contamination plume. The pumping rate of midstream was larger than downstream. Comparison of the two optimization algorithms showed that the optimized system management cost of SA was 6.8%, which was lower than that of GA. Meanwhile, SA was easily convergent with smaller volatility.

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.

[Simulation on contamination forecast and control of groundwater in a certain hazardous waste landfill].

On the basis of site investigation and data collection of a certain hazardous waste landfill, the groundwater flow and solute transport coupled models were established by applying Visual Modflow software, which was used to conduct a numerical simulation that forecast the transport process of Cr6+ in groundwater and the effects of three control measures (ground-harden, leakage-proof barriers and drainage ditches) of contaminants transport after leachate leakage happened in impermeable layer of the landfill. The results show that the contamination plume of Cr6+ transports with groundwater flow direction, the contamination rang would reach the pool's boundary in 10 years, and the distance of contamination transport is 1 450 m. But the diffusion range of contamination plume would not be obviously expanded between 10 and 20 years. While the ground is hardened, the contamination plume would not reach the pool's boundary in 20 years. When the leakage-proof barrier is set in the bottom of water table aquifer, the concentration of Cr6+ is higher than that the leakage-proof barrier is unset, but the result is just opposite when setting the leakage-proof barrier in the bottom of underlying aquifer. The range of contamination plume is effectively controlled by setting drainage ditches that water discharge is 2 642 m3 x d(-1), which makes the monitoring wells would not be contaminated in 20 years. Moreover, combining the ground-harden with drainage ditches can get the best effect in controlling contaminants diffusion, and meanwhile, the drainage ditches' daily discharge is reduced to 1 878 m3 x d(-1). Therefore, it is suggested that the control measure combining the ground-harden with drainage ditches should apply to prevent contamination diffusion in groundwater when leachate leakage have happened in impermeable layer of the landfill.

[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.

[Degradation effect and mechanism of 2,4-DNT by reduction-ZPF catalytic oxidation].

ZPF(zeoliteartificial pillared by alpha-FeOOH) which prepared in the laboratory and characterized by FTIR and XRD was used as catalyst, and was tested for its activity in catalytic H2O2, of 2,4-DNT, which is persistent and difficult to be degraded in groundwater. The degradation of 2,4-DNT was examined at different pHs in the reduction, catalytic oxidation and combination technology of reduction-catalytic oxidation reaction systems. Moreover, the removal effect of 2,4-DNT was compared by these three approaches and the catalytic oxidation mechanism was analyzed. The results demonstrated that the removal effect of 2,4-DNT reduced to 2,4-DAT was up to 96.6% in 120 min at pH = 5, which was 1.2, 2.0 times of the rate at pH 7, pH 9 respectively. The catalytic effect was various at different pHs and more significant when the pH close to the zero point of charge of alpha-FeOOH. The order of removal effect of 2,4-DNT at different pHs was pH = 7 > pH = 9 > pH = 5. Compared to single reduction or catalytic oxidation, the removal effect of combination technology was 57.4%, which was evidently improved on the base of 2,4-DNT reduced to 2,4-DAT. The degradation of 2,4-DNT in the presence of ZPF/H2O2 follows a first-order kinetic model and the k(obs) was 0.002 7 min(-1). Due to the concentration of dissolved Fe ion was far less than 0.07 mmol/L, the mechanism was heterogeneous Fenton reaction acting on the surface of the catalyst. Therefore the combination technology was superior to the single treatment of reduction or catalytic oxidation.