Leaching characteristics of heavy metals from New York City biosolids.
Item
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Title
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Leaching characteristics of heavy metals from New York City biosolids.
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Identifier
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AAI9707124
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identifier
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9707124
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Creator
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Liu, Tianqing.
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Contributor
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Adviser: David C. Locke
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Date
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1996
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Analytical | Environmental Sciences | Engineering, Environmental | Engineering, Sanitary and Municipal | Health Sciences, Toxicology
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Abstract
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A unique leaching column apparatus was constructed to study the leaching of heavy metals from sewage sludge products applied to different soil types. Two sewage sludge products from the sewage treatment plants of New York City, composted and thermally dried sludges, which are intended for agricultural and land applications, and two types of soil, sandy and urban organic-rich soils were studied in this research. Synthetic rain water was applied to the leaching columns and the concentrations of 11 heavy metals in the effluent from the columns were monitored continuously. A strongly acidic pH 1.5 leaching solution causes extensive leaching of heavy metals, but no significant leaching was observed between pH 4.0 and 4.5, the common pH values of NYC rain water in summer and winter. Soils with higher organic contents and cation exchange capacity retain heavy metals leached from sewage sludge more strongly and hence can prevent ground water from being contaminated by heavy metals. The mobility of heavy metals from thermally dried sludge is relatively low compared with composted sludge, suggesting the good quality of the thermally dried sludge product. The characteristics of individual heavy metal elements bound to inorganic and organic moieties in sludge and soil were addressed. Safe usage of different sludge products applied to various soil types was predicted based on the results of this research.;The analytical techniques, flame atomic absorption spectrometry (AAS), graphite furnace atomic absorption spectrometry (GFAAS), and inductively coupled plasma-atomic emission spectrometry (ICP-AES) were optimized to analyze the leachate samples. Matrix modifiers in GFAAS was successfully used for analysis of volatile metals in the leachates at the highest sensitivity level. ICP-AES is one of the most reliable analytical techniques, and is applicable to many different types of samples. However, when ICP-AES is applied to environmental samples such as leachates from the sewage sludge products, in which a matrix-matched calibration is extremely difficult, special care must be taken to optimize instrumental sensitivity and detection limits for trace analysis. Signal-to-noise ratio and detection precision were much improved by the use of increased integration time, internal standardization, and background correction and interelement correction techniques.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
