| Along with the dramatic increase in the total amount of municipal solid waste generated in China, the environmental issues accompanied with solid waste disposal processes had aroused wide attention. Landfills, as the dominant MSW treatment way in most cities, are often complained by surrounding communities due to the serious odor pollution caused by landfilling operation; and the working surface is generally regarded as one of the most important odor emission source in landfills. Hence, it is of significant importance to investigate the characterization of odorous gas emission as well as temporal variation of odor concentration on the working surface of the landfills, and also to figure out major odor sources of those significant odorous compounds in solid waste.The temporal variation of trace component emissions from the working surface of a landfill in Beijing was first investigated. Specific days in a year were selected as representatives for all four seasons. Different chemical species were quantified in all four seasons with the following average concentrations: spring: 41 compounds, 2,482.6 μg·m-3; summer: 59 compounds, 4,512.6 μg·m-3; fall: 66 compounds, 2,438.4 μg·m-3; and winter: 54 compounds, 2,901 μg·m-3. The detected compounds included sulfur compounds, oxygenated compounds, aromatics, hydrocarbons, halogenated compounds, and terpenes. Oxygenated compounds were the most abundant compound in most samples. Isobutane, ethyl alcohol, limonene, butane, toluene, and trichlorofluoromethane were recognized as the most abundant compounds on the working surface throughout the year.The daily fluctuations of odor concentration on the working surface in different seasons were then investigated. It was found that most serious odor pollution were found in spring and winter, while lower odor concentrations appeared in summer and winter. 14:00 and 2:00-6:00 turned out to be the most dangerous time in a day that serious odor pollution may happen. There is statistically significant correlation between odor concentrations determined by triangle odor bag method and total VOCs concentrations(r2=0.41, n=42, P < 0.01). Meteorological conditions could also affect odor concentrations on the working surface; temperature and atmospheric pressure were found to be the most important factors. By calculating the theoretical odor concentration as well as the frequency of each odorous compound in different samples, ethyl alcohol, α-piene, hydrogen sulfide, dimethyl sulfide, limoene, methyl mercaptan, dimethyl disulfide diethyl sulfide were selected as odor index compounds on the working surface of MSW landfills.Laboratory experiments were finally performed to make source apportionment for different odorous compounds. Biodegradable composition in solid waste were figured out and classified as food waste(including vegetable waste, fruit waste as well as animal waste), yard waste and paper waste. A total of 11 anaerobic reactors were set as MSW, FW, VGW, FRW, ANW and SLUDGE with different seed ratios. The results showed that oxygenated compounds were mainly emitted from the hydrolysis and acidification processed of starch, protein and fat; while sulfur compounds were often the product of fermentation of S contained waste such as animal waste. Terpenes genaerally came from fruit wastes, and aromatics, halogenated compounds together with alkanes and alkenes were emitted along with methane production. Sulfur compounds and terpnes were figured out as dominant odorous compounds during the methane production period; and controlling the portion of fruit and animal waste in landfilled waste might be of great importance to odor emission reduction in landflls. |
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