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|Title: ||Environmental geochemistry of antimony in Chinese coals and two typical mines|
|Other Titles: ||Ti zai Zhongguo mei ji dian xing kuang qu zhong de huan jing di qiu hua xue|
|Authors: ||Qi, Cuicui (齐翠翠)|
|Department: ||Department of Biology and Chemistry|
|Degree: ||Doctor of Philosophy|
|Issue Date: ||2010|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Antimony -- Environmental aspects.|
Environmental geochemistry -- China.
Coal mines and mining -- Environmental aspects -- China.
|Notes: ||CityU Call Number: QE516.S3 Q25 2010|
xvi, iii, 127 leaves : ill. 30 cm.
Thesis (Ph.D.)--City University of Hong Kong, 2010.
Includes bibliographical references.
|Abstract: ||Antimony (Sb) is a trace element in the Earth's crust. Significant quantities of Sb are used by several industries in modern times. The toxicity of Sb compounds in the environment has been increasingly recognized recently. However, Sb is a potentially toxic trace element and is a cumulative poison with unknown biological functions that may produce adverse effects in humans and the environment. In spite of its environmental impact, geochemical cycles, environmental fate and the impact of anthropogenic activities related to Sb have not received as much attention as other elements of environmental concern, such as As, Cr, Hg, Pb and Sn. The presence of Sb in the atmosphere may be due to natural and anthropogenic inputs. Major anthropogenic sources are fossil fuel combustion, non-ferrous metals refining, waste incineration, and incineration of sewage sludge. Antimony is commonly enriched in practically all metal sulfide ores (especially those of Pb and Cu) as well as in coal. Coal is one of the most important sources of energy. Its worldwide use will continue to expand during next several decades, particularly in rapidly developing countries, including China. With the increasing use of coal, there is an urgency to enhance the knowledge of Sb in coals and its behavior during coal mining, treatment, and usage.
The distribution, modes of occurrence, geological processes and environmental effect of Sb in Chinese coals were reviewed. 1058 coal samples were collected from Chinese sources and the average Sb content in Chinese coals was 2.27 μg g-1. Based on average Sb content, coal from provinces, cities and autonomous regions may be divided into three groups. Group 1 has a low average Sb content (lower than 1 μg g-1), Group 2 has a medium average Sb content (1-3 μg g-1), and Group 3 has a high average Sb content (>3 μg g-1). Sb is extremely enriched in the Guizhou and Inner Mongolia Coals. The amount of Sb in coal varies with coal-forming periods and coal ranks. There are several modes of occurrence of Sb in coal. It occurs in discrete pyrite grains and is dispersed in the organic matter as tiny sulfide particles. During coal combustion Sb is partly released to the atmosphere and partly partitioned into the solid residues. Sb in the environment brings about definite harm to human health.
Environmental impact of a trace element in coal is related to its concentration and modes of occurrence. Abundance of Sb in bulk samples was determined in five selected coals, of which three coals were from Huaibei Coalfield, Anhui, China, and the other two from Illinois Basin, USA. The Sb abundance in these samples was in the range of 0.11 μg g-1 - 0.43 μg g-1. The forms of Sb in coals were studied by sequential solvent extraction. The Sb forms include water soluble, ion-changeable, organic matter-bound, carbonate-bound, silicate-bound, and sulfide-bound. Results of sequential extraction showed that the silicate-bound Sb was the most abundant form in these coals. Silicate plus sulfide-bound Sb accounted for more than half of the total Sb in all coals. Bituminous coals were higher in organic matter-bound Sb than anthracite and natural coke, indicating that the Sb in the organic matter may be incorporated into silicate and sulfide minerals during metamorphism.
Thirty-three soil samples were collected from the Luling, Liuer, and Zhangji coal mines, in the Huaibei and Huainan areas, Anhui Province, China. The samples were analyzed for Sb by ICP-OES method. The average Sb content in 33 samples was 4.0 μg g-1, which is lower than that recorded in coals from this region (6.2 μg g-1). More than 75% of the soils sampled show a significant degree of Sb pollution (EFs 5-20). The soils collected near the gob pile and coal preparation plant were higher in Sb content than those collected from residential areas near the mines. The gob pile and tailings from the preparation plant were high in mineral matter content and high in Sb. They are the sources of Sb pollution in surface soils in the vicinity of coal mines. The spatial dispersion of Sb in surface soil in the mine region shows that Sb pollution could reach out as far as 350 m. Crops in rice paddies may adsorb some Sb and reduce the Sb content in soils from paddy fields. Vertical distribution of Sb in two soil profiles indicates that Sb is relatively immobile in soils.
Sb distribution and accumulation in plants in Xikuangshan Sb deposit area, the only super-large Sb deposit in the world, Hunan, China, were investigated. Results show that soils were severely polluted with the average Sb concentrations up to 5949.20 μg g-1. Sb widely occurred in 34 plants with various concentrations ranging from 3.92 μg g-1 to 143.69 μg g-1. Equisetaceae family has the highest concentration (98.23 μg g-1) while Dryopteridacea family has the lowest one (6.43 μg g-1). H. ramosissima species of Equisetaceae family had the highest average Sb concentration of 98.23 μg g-1 and P. vittata species of Pteridaceae family showed high abilities of accumulating Sb from the contaminated environment (Biological Accumulation Coefficient, BAC=0.08). Almost all species enriched Sb in their upground part such as shoot, leaf and flower (Biological Transfer Coefficient, BTC > 1), which may
attribute to the high acropetal coefficient and Sb transformation from the atmosphere to the plants. P. phaseoloides and D. indicum showed predominant accumulation of Sb in the upground part with BTC of 6.65 and 5.47, respectively.
From the low bioavailable fraction in soils and weak relationship between total concentrations in soils and plants, it seems that the bioavailability of Sb was limited and varied with different soil types (sites) as well as plant species. Those observations would be significant to the phytoaccumulation and phytoremediation of Sb in plants and ecological attribute to the high acropetal coefficient and Sb transformation from the atmosphere to the plants. P. phaseoloides and D. indicum showed predominant accumulation of Sb in the upground part with BTC of 6.65 and 5.47, respectively.
From the low bioavailable fraction in soils and weak relationship between total concentrations in soils and plants, it seems that the bioavailability of Sb was limited and varied with different soil types (sites) as well as plant species. Those observations would be significant to the phytoaccumulation and phytoremediation of Sb in plants and ecological and environmental risk assessment of Sb in contaminated areas.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b3947505|
|Appears in Collections:||BCH - Doctor of Philosophy |
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