云贵高原湖泊沉积物─水界面碱度扩散通量研究

STUDY ON ALKALINITY DIFFUSION FLUX AT THE INTERFACE OF SEDIMENT AND WATER OF LAKES FROM YUNGUI PLATEAU, CHINA

于1991-1995年间5次在云贵高原泸沽湖、洱海湖和贵州阿哈湖、百花湖的湖心采集沉积物柱芯、界面水和湖水样品，通过其pH值和HCO-3浓度剖面及界面碱度扩散通量的研究，首次定量评估高原湖泊界面扩散作用上覆水体碱度的影响程度。研究结果表明，云贵高原某些湖水寄宿时间相对较长、湖水深度相对小的湖泊，界面扩散作用是水体碱度的重要来源之一;湖水寄宿时间较短、深度较小的湖泊，界面扩散对上覆水体的影响可以忽略不计。

In 1991-1995, sediment was cored and interface water and overlying water are sampled several times in the center area of 4 lakes from southwestern Plateau of China Seasonal profiles of pH value and HCO, and alkalinity fluxes which had been corrected by using the upward okidation fluxes of Fe2+ and Mn2+ ions in porewater at the sediment water interface were studied' The extent of the effeet of diffusion on the overlying water was calculated quantitatively for the first time' The extent is related to the alkalinity diffusion flux (Ja), the water residence time (TJ, water depth (h) and alkalinity concentration (C) in overiying water. ms study showed that there was obvious gradient of many ions such as Fe+, Mn+, Ca2+, Mg2+, K+, Na+, SO24-, NO, and HCO3, and molecular diffusion near the interface, resulting from biogeochemcal processes during diagenesis,including sulfate reduction, denitrification, reduction-dissolution of iron, maganese oxidation, decomposition of organic matter, and carbonate dissolution. Upward alkalinity diffusion fluxes from the sediments is an important source to the overlying water in lakes with lOng residence time and shallow depth' For example, in Lugu mke,33% of the alkalinity came from diffusion from deep sediments, but it can be negligible for lakes with short residence time and deep water depth, 10 percent of water alkalinity in Erhai hake and Baihua Lake, and only O'52 percent in Aha Lake came from interface diffusion.