Assessment of waters and sediments impacted by drainage at the Young Dong coal mine site, South Korea.

INTRODUCTION: This study focused on the assessment of the geochemistry and hydrology of the Imgok Creek-Young Dong tributary for the design of a field coal mine drainage treatment system. METHODS AND RESULTS: Examination of this site showed that the pH was greatly lowered by the addition of the Young Dong water, except in the month of March. The alkalinity was also affected; the concentrations of iron, aluminum, and sulfate were elevated at sites below the confluence; of these, iron was particularly problematic. High iron concentrations were primarily restricted to the acid rock drainage (ARD) (YD-9) water sources, whereas high aluminum concentrations were seen in both the ARD and in some of the upstream water sources. The acidity was primarily due to ferrous and ferric iron with a lesser amount of aluminum acidity. Except for the sampling in March, the flow was dominated by the ARD. This hydrologic condition resulted from the loads of iron, aluminum, sulfate, and acidity, among other constituents, that were dominated by the ARD. CONCLUSION: Finally, treatment activities should primarily focus on the ARD and specifically seek to remove ferrous and ferric iron from the treatment system.

Optical transmission through double-layer metallic subwavelength slit arrays.

We present measurements of transmission of infrared radiation through double-layer metallic grating structures. Each metal layer contains an array of subwavelength slits and supports transmission resonance in the absence of the other layer. The two metal layers are fabricated in close proximity to allow coupling of the evanescent field on individual layers. The transmission of the double layer is found to be surprisingly large at particular wavelengths, even when no direct line of sight exists through the structure as a result of the lateral shifts between the two layers. We perform numerical simulations using rigorous coupled wave analysis to explain the strong dependence of the peak transmission on the lateral shift between the metal layers.