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Yao‐Tung Lin, Chih‐Huang Weng, Sheng‐You Lee
Journal of Environmental Engineering, April 2011
Abstract
Some paddy rice field in central Taiwan had been exposed to metal‐containing irrigation water for over 20 years. This study was carried out to evaluate the spatial distribution of heavy metal in soils examplied by Cr, Cu, and Zn. Four sites were studied and each site was divided into a regular grid of 5 m × 5 m in the sampling process. At the surface, total metal concentrations were not normally distributed, showing rather positively skewed profile. The concentration of Cr, Cu, and Zn away from irrigation channel inlet around 20 m decreased by approximately more than 40 % with respect to that of at the entrances. Findings revealed that a linear relationship between logarithm of the metal concentration and irrigation distance for each site was found. Vertically, the content of Cr, Cu, and Zn in soil decreased in two stages with respect to depth. The first stage was from the surface (0 ̃ 15 cm depth) to the bottom horizon (15 ̃ 30 cm depth) and the second stage was from the bottom horizon to the deeper horizon (30 ̃ 45 cm depth). The highest concentrations were observed at the irrigation inlets, and the concentration decreased with increasing distance from the irrigation inlet until 40 m. The lowest concentrations were found at the irrigation outlets. A linear relationship between the logarithmic metal concentration and irrigation distance for each site was found. In the case of soil exposed to metal‐containing irrigation water, the patent of water flow on the soil surface and in the subsurface was a determining factor in the redistribution of Cr, Cu, and Zn within the sites studied.
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