Investigation of Gas Generation by Riverine Sediments: Production Dynamics and Effects of Sediment Properties

Abstract

Due to microbial activities, the anaerobic degradation of organic matter happens in the sediments and leads to considerable gas production. Especially for low flow areas gas production is more easily fostered. To prevent the potential problems caused by gas production from the riverine sediments, this study focuses on magnitude of gas formation and its relation with soil properties. Nine locations of known at Port of Hamburg were sampled; for each location the fresh sediment samples were collected at different depths and on different seasons. Samples were stored and transported to several institutes for various analyses, including analysis on sediment standard properties, and on gas production by incubation.

Being part of the BIOMUD project, this study analyzed data from several research institutes. A strong correlation was found between magnitude of gas production and some of the soil properties including content of TOC, TN, ratio of TOC/P, TOC/S, density fractionation, and content of various types of metal elements. A clear relationship was found between magnitude of short-term and long-term gas production, providing possibilities for estimation work on gas formation in the future. The modified Afvalzorg multi-phase model was applied in analyzing gas production on the timeline, which played a key role in describing and predicting gas production in the long-term. The total gas potential of the river sediments at the Port of Hamburg was then predicted as 105.3 mg C/g TOC on average, relating to 10.5% of the organic matter being degraded. By temperature experiment a Q10 value of 2.06 was determined for assessing the sensitivity of gas production to temperature. Gas composition inside the bottles was also measured after four months’ incubation in the temperature experiment, with the results of CH4/CO2 ratio ranged from 0.92 to 1.86 for different temperature conditions. Parts of the results acquired from the experiments mentioned above were also compared with the results from previous studies made by other researches.