Characterizing Interaction of Copper and Dissolved Organic Matters in Soils from Coal Mine Land Subsidence Areas Using 3D-EEM Fluorescence Spectroscopy.

Underground coal mining often leads to severe environmental issues, such as land subsidence, loss of groundwater, heavy metal contamination of soil and water. In order to perform reclamation in these areas, it is necessary to understand the role of dissolved organic matters (DOMs) in the soil because they are important for transport and transformation of metals. In this study, characteristics and binding capacity with copper by DOMs in soil collected from land subsidence area during coal mining was evaluated using three dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, PARAFAC and fluorescence quenching experiments. DOMs were fractionated based on molecular weight using dialysis method and further divided into two groups, fulvic acid-like components (FACs, <3,500 Da) and protein-like components (PTCs, <3,500 Da). The results showed that four fluorescence peaks were detected from these DOMs, two for FACs and two for PTCs. The capacities of copper bound by DOMs were 190.9, 197.8, 40.3, 53.6, 57.8 and 21.2mg/g for factions of DOMs at <500 Da, 500-2,000 Da, 2,000-3500 Da, 3,500-5,000 Da, 5,000-10,000 Da, and >10,000 Da, respectively. FACs had more metal-binding sites compared to PTCs.