Yonghai Jiang

Fluorescence excitation-emission matrix spectroscopy with regional integration analysis for characterizing composition and transformation of dissolved organic matter in landfill leachates.

Dissolved organic matter (DOM) obtained from landfill leachates was separated into hydrophobic base, hydrophilic matter (HIM), hydrophobic acid (HOA), and hydrophobic neutral fractions. The composition and transformation of the DOM and its fractions were investigated. The results show that the DOM isolated from young, intermediate, and old landfill leachates were mainly composed of tyrosine-, tryptophan-, and humic- and fulvic-like substances, respectively. The primary fractions of the DOM in leachates were HOA and HIM. The HOA and HIM fractions from young leachates predominantly contained tryptophan- and tyrosine-like materials, respectively. The HOA fractions in intermediate and old leachates were mainly composed of humic- and fulvic-like materials, whereas the HIM fractions were dominated by tryptophan-like materials and humic- and fulvic-like substances. The hydrophobic organic fractions and humic- and fulvic-like substances increased with time, whereas the HIM and the tyrosine-like materials decreased during the landfill process, rendering biological processing of leachates ineffective.

Physicochemical and spectroscopic characteristics of dissolved organic matter extracted from municipal solid waste (MSW) and their influence on the landfill biological stability

For the purpose of evaluating the stability of municipal solid waste (MSW) excavated from a landfill, dissolved organic matter was extracted and characterized by physicochemical and spectroscopic methods. Results showed that dissolved organic carbon concentration, ratio of dissolved organic carbon to dissolved organic nitrogen, and specific ultraviolet absorbance at 254 nm were in the range of 0.383-3.502 g kg(-1), 0.388-3.693 and 2.700-4.629 L mg(-1) m(-1), respectively, indicating the stability of MSW. Results obtained from Fourier transform infrared spectra have demonstrated that the stability of excavated MSW was characterized by disappearance of some easily biodegradable compounds; and the 1635/1406 ratio varied from 0.979 to 1.840 and was higher than that of the matured compost. The excitation-emission matrix spectra have shown that the principal components in excavated MSW comprised humic substances and the MSW was stable by the presence of a peak with wavelength pair of ∼280/420 nm.

Distribution and ecological risk of antibiotics in a typical effluent-receiving river (Wangyang River) in north China.

In this study, the occurrence and distribution of sixteen antibiotics belonging to four groups in surface water, sediment and groundwater samples from the Wangyang River (WYR), a typical river receiving sewage discharges were investigated. Laboratory analyses revealed that antibiotics were widely distributed in the studied area. The aqueous samples were unavoidably contaminated with antibiotics, and the target antibiotics present in high levels were oxytetracycline, tetracycline, chlortetracycline, ofloxacin, sulfamethoxazole, and trimethoprim, with maximum concentrations of the individual contaminant at 3.6×10(5), 9.7×10(3), 6.9×10(4), 1.2×10(4), 4.8×10(3), and 1.1×10(3) ng L(-1), respectively. Oxytetracycline, tetracycline, ciprofloxacin and roxithromycin were the most frequently detected compounds in sediment samples, with maximum concentrations of the individual contaminant at 1.6×10(5), 1.7×10(4), 2.1×10(3) and 2.5×10(3) ng g(-1), respectively. The results also revealed that the high intensity of aquaculture activities could contribute to the increasing levels of antibiotics in the area. According to the ratios of measured environmental concentration (MEC) to predicted no-effect concentration (PNEC), chlortetracycline, tetracycline, ofloxacin, ciprofloxacin, erythromycin-H2O and sulfamethoxazole may present possible environmental risk to Pseudokirchneriella subcapitata, Synechococcus leopoliensis and M. aeruginosa. Attention should be given to the long-term ecological effects caused by the continuous discharge of antibiotics in the WYR area.

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.

Effect of water-extraction on characteristics of melting and solidification of fly ash from municipal solid waste incinerator

This study was conducted to investigate the effect of water-extraction process on the removal of major elements and heavy metals in the fly ash from Municipal Solid Waste Incinerator (MSWI), and their thermal stability in the following melting process. The water-extraction was first applied to extract soluble elements and heavy metals from the fly ash from MSWI at different liquid-to-solid rates (L/S) of 2, 5, and 10, respectively. The extracted fly ash and the raw fly ash were then melted at the temperatures of 1000-1350 degrees C in an electrically heated furnace. The results showed that the compounds of Ca, Na, K, and Cl achieved high removal rates of 30.7-72.8% at L/S=10, respectively, Cr was the most extractable heavy metal with removal rate of 12.3% among the several heavy metals tested. The water-extracted fly ash had better stability as compared to raw one, which was indicated by lower weight loss and better immobilization ability of heavy metals such as Zn, Cu, and Pb in the melting process. The results showed that combing water-extraction and melting process could provide one of the alternatives for treating MSWI fly ash in China for reutilization.

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.

Sources of groundwater salinity and potential impact on arsenic mobility in the western Hetao Basin, Inner Mongolia

The quality of groundwater used for human consumption and irrigation in the Hetao Basin of Inner Mongolia, China is affected by elevated salinity as well as high arsenic (As) concentrations. However, the origin of high salinity and its potential impact on As mobility in the Basin remain unclear. This study explores both issues using stable isotopic compositions and Cl/Br ratios of groundwater as well as the major ions of both groundwater and leachable salts in aquifer sediments. Limited variations in δ18O and δ2H (-11.13 to -8.10, -82.23 to -65.67) with the wide range of Total Dissolved Solid (TDS, 351-6734mg/L) suggest less contribution of direct evaporation to major salinity in groundwater. Deuterium excess shows that non-direct evaporation (capillary evaporation, transpiration) and mineral/evaporite dissolution contribute to >60% salinity in groundwater with TDS>1000mg/L. Non-direct evaporation, like capillary evaporation and transpiration, is proposed as important processes contributing to groundwater salinity based on Cl/Br ratio and halite dissolution line. The chemical weathering of Ca, Mg minerals and evaporites (Na2SO4 and CaSO4) input salts into groundwater as well. This is evidenced by the fact that lacustrine environment and the arid climate prevails in Pleistocene period. Dissolution of sulfate salts not only promotes groundwater salinity but affects As mobilization. Due to the dissolution of sulfate salts and non-direct evaporation, groundwater SO42- prevails and its reduction may enhance As enrichment. The higher As concentrations (300-553μg/L) are found at the stronger SO42- reduction stage, indicating that reduction of Fe oxide minerals possibly results from HS- produced by SO42- reduction. This would have a profound impact on As mobilization since sulfate is abundant in groundwater and sediments. The evolution of groundwater As and salinity in the future should be further studied in order to ensure sustainable utilization of water resource in this water scarce area.

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.

Identification of nitrate sources in groundwater using a stable isotope and 3DEEM in a landfill in Northeast China

The groundwater was sampled in a typical landfill area of the Northeast China. Coupled stable isotope and three dimensional excitation-emission matrix (3DEEM) were applied to dentify diffused NO3(-) inputs in the groundwater in this area. The results indicated that combined with the feature of groundwater hydrochemistry and three-dimensional fluorescence technology can effectively identify the nitrate pollution sources. The nitrate was derived from manure and sewage by δ(15)N and δ(18)O-NO3(-) values of groundwater in the different periods. The excitation-emission matrix fluorescence spectroscopy was further evidence of groundwater DOM mainly which comes from the landfill. The protein-like was very significant at the sampling points near the landfill (SPNL), but only fulvic acid-like appeared at downstream of the landfill groundwater sampling points (DLGSP) in the study area. Partial denitrification processes helped to attenuate nitrate concentration in anaerobic environment.

Analysis for remedial alternatives of unregulated municipal solid waste landfills leachate-contaminated groundwater

A groundwater flow and solute transport model was developed using Visual Modflow for forecasting contaminant transport and assessing effects of remedial alternatives based on a case study of an unregulated landfill leachate-contaminated groundwater in eastern China. The results showed that arsenic plume was to reach the pumping well in the downstream farmland after eight years, and the longest lateral and longitudinal distance of arsenic plume was to reach 200 m and 260 m, respectively. But the area of high concentration region of arsenic plume was not to obviously increase from eight years to ten years and the plume was to spread to the downstream river and the farmland region after 20 years; while the landfill’s ground was hardened, the plume was not to reach the downstream farmland region after eight years; when the pumping well was installed in the plume downstream and discharge rate was 200m3/d, the plume was to be effectively restrained; for leakage-proof barriers, it might effectively protect the groundwater of sensitive objects within an extent time range. But for the continuous point source, the plume was still to circle the leakage-proof barrier; when discharge rate of drainage ditches was 170.26 m3/d, the plume was effectively controlled; the comprehensive method combining ground-harden with drainage ditches could get the best effect in controlling contaminant diffusion, and the discharge rate was to be reduced to 111.43 m3/d. Therefore, the comprehensive remedial alternative combining ground-harden with drainage ditch will be recommended for preventing groundwater contamination when leachate leakage has happened in unregulated landfills.