Thursday, 13 July 2006

Effect of Dust from Magnesite Calcination on Soil Physical and Chemical Properties.

Wang Qiubing, Wang Jingkuan, Zhang Xinyu, Li Jun, Chen Xinzhi, and Zhang Yulong. Land and Environment College,Shenyang Agricultural University, No.120,Dongling Road, Shenyang, 110161, China

China is an important base of producing and processing magnesite in the world. However, a lot of dust came from the mining and calcination of magnesite settle into the soils around the mining areas and seriously polluted farmland, orchard and woodland, which resulted in soil deterioration. Up to now, no detail reports have been found on the mechanism of soil pollution by the dust. The objectives of this research were to explore the effect of dust from magnesite calcination on soil properties. Soil samples were collected from 9 different site around the magnesite mining area at Pailou town, Haicheng of Liaoning province. The soils before pollution were Udalfs and Fluvents. The properties of soils were determined. The methods were referred to Yu Renpei (1984). The results obtained showed that soil properties changed greatly after the dust settled into the soil, especially the soil pH went from 6.83 in unpolluted soils to 9.52 in heavily polluted soils. The increase of pH values led to the lower availability of phosphorus and microelements such iron and zinc. Meanwhile, the ratios among different nutrients were imbalanced in polluted soils, e.g. Ca2+/Mg2+ was 3.43 in normal soils, but 0.04 in heavily polluted soils, which led to little absorption of Ca2+ and K+ by plants due to their competitiveness. In addition, a hard crusty top layer with different thickness appeared in polluted soil profiles, which destroyed soil structure. It was found that percentage of 0.01-0.25mm microaggregates decreased from 32.63 in unpolluted soils to 10.67 in heavily polluted soils, but percentage of the microaggregates less than 0.001mm increased from 23.10-32.13. This resulted in the increase in soil compaction and bulk density and the decrease in porosity and permeability. It was found that the beginning percolating speed was 2.00mm/min in unpolluted soils, but 0.60mm/min in heavily polluted soils. The stable percolating speed in unpolluted and polluted soils was 0.48 and 0.06mm/min, respectively.

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