Loss on Ignition-Based Indices for Evaluating Organic Matter Characteristics of Littoral Sediments

Understanding organic matter characteristics （e.g., amount and state） of sediments is necessary for evaluating both the sediment and water environments; however, methods that have been proposed to investigate these characteristics are relatively expensive. This study attempted to evaluate the organic matter characteristics of littoral sediments by employing solely the loss on ignition （LOI） method, which is the most economical and accessible method in developing countries. Different types of sediments were first oven dried at 100 ~C and then continuously burned at 200, 300, 400, 500, and 600 ~C for 4 h at each temperature. The mass LOI at each temperature was calculated and compared with the 100 ℃oven-dried weight. Our results suggested that the mass LOI across the temperature range of 200-300 ℃（LOI200-300）：mass LOI at 600 ℃ （LOI600） ratio （LOI200-300/LOI600） could represent different types of sediments as well as the organic matter：organic C ratio. Compared with the sediments unaffected by wastewater, the sediments that were more influenced by the inflow of domestic wastewater had a higher LOI200-300/LOI600. Interestingly, LOI200-300/LOI600 could also represent changes in the organic matter characteristics as a function of organic matter decomposition in sediments. In conclusion, the organic matter characteristics of littoral sediments could be evaluated using solely the LOI method, particularly with LOI200 - 300/LOI600.