云贵高原湖泊沉积物─水界面碱度扩散通量研究

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ＨＣＯ３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不体碱度的影响程度，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地。

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

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 HCO₃^- and alkalinity fluxes which had been corrected by using the upward oxidation fluxes of Fe²⁺ and Mn²⁺ ions in pore water at the sediment water interface were studied. The extent of the effect of diffusion on the overlying water was calculated quantitatively for the first time. The extent is related to the alkalinity diffusion flux (J_a), the water residence time (T_w), water depth (h) and alkalinity concentration (C) in overlying water. This study showed that there was obvious gradient of many ions such as Fe²⁺, Mn⁺, Ca²⁺, Mg²⁺, K⁺, Na⁺, SO₄^2-, NO₃^- and HCO₃^-, and molecular diffusion near the interface, resulting from biogeochemical processes during diagenesis, including sulfate reduction, denitrification, reduction-dissolution of iron, manganese 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 Lake, 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 Lake and Baihua Lake, and only 0.52 percent in Aha Lake came from interface diffusion.