Reclamation of land disturbed by tin mining

Tanavud, Charlchai (1992). Reclamation of land disturbed by tin mining PhD Thesis, School of Land, Crop and Food Sciences, The University of Queensland.

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Author Tanavud, Charlchai
Thesis Title Reclamation of land disturbed by tin mining
School, Centre or Institute School of Land, Crop and Food Sciences
Institution The University of Queensland
Publication date 1992
Thesis type PhD Thesis
Total pages 203
Language eng
Subjects 290701 Mining Engineering
300801 Environmental Management and Rehabilitation
Formatted abstract This thesis is concerned with the feasibility of reclaiming lands disturbed by tin mining. The wastes produced as a result of many years of tin ore extraction in Thailand and Australia are similar being sand tailings, consisting mainly of coarse sand, and slime tailings consisting of silt and clay particles. These two types of tailings result from the use of flowing water to extract ore from the soil in the mining process. The sand tailings are deposited near the palong (elevated sluice box), while the slime is deposited further away.

Both the sand and slime tailings are unable to support growth of vegetation, even many years after cessation of mining. This is a major problem for the reclamation of tin mine tailings in a densely populated country such as Thailand. Both sand and slime tailings, collected from an abandoned tin mine in Inverell, New South Wales, possessed several chemical and physical limitations to plant growth. Acidity and nutrient deficiencies were chemical limitations in both types of tailings. The experiments reported in this thesis demonstrated that such limitations can be alleviated by liming and fertilization. Sand and slime tailings required 1 and 6 ton/ha of lime respectively to bring the pH to 7 . The optimal level of fertilizer for sand and 11 slime tailings were approximately 200 to 400 kg N/ha and 200 kg P/ha if all other nutrients were satisfied. 

The physical limitations on the sand tailings were largely associated with low water holding capacity in the order of 3 % by weight and high saturated hydraulic conductivity (2.86*10-3 cm/s), whereas inadequate aeration ( 9.9 % air filled porosity at field capacity ) was the main physical limitation on the slime tailings. Methods to alleviate the physical limitations of water stress and aeration problem were investigated by the mixing of sand and slime tailings in various proportions. The laboratory analysis of these sand-slime mixtures and the response of Rhodes grass (Chloris qayana cv. Pioneer) in pots and long columns indicated that a mix of 70 % sand and 30 % slime tailings by weight was most suitable. In the long columns a mixture of 70 % sand and 30 % slime by weight resulted in yield of 1.8 to 3.5 times that of sand alone depending on the frequency of watering. The increase in yield is directly related to increase amount of water available to the plant.

Often there are insufficient quantities of slime tailings available for a 70:30 mix because the slime have often been discharged into streams and river. Therefore, it was necessary to develop methods which required less amount of slime to increase water holding capacity of the sand tailings. It was found that a subsurface placement of 3 cm thick slime layer in the sand profile was effective. Based on a 90 cm depth profile only 2 % of slime by weight was required, compared to 30 % slime in a complete sand : slime mix, to increase plant available water to the same extent (i.e. an increase of 100%).

Another possible means of increasing plant available water capacity of the sand tailings is to use an organic amendment such as peat. The responses of plants to peat addition were not assessed in this thesis, however addition of 10% peat may increase plant available water capacity by 184%.

The ramification of this study to the tin mining industry is that it is feasible to successfully reclaim tin mine spoils. Furthermore, for ease of future reclamation it would be better for the sand and slime tailings to be discharged together or discharged in alternating layers.
Keyword Reclamation of land.
Tin mines and mining -- Environmental aspects.
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