By multi-proxy analysis of grain-size, magnetic susceptibility (MS), Fe/Mn and Rb/Sr ratios, TOC and other chemical elements, environmental changes in the Hongjiannao Lake over the past 80 years were discussed. It is ...By multi-proxy analysis of grain-size, magnetic susceptibility (MS), Fe/Mn and Rb/Sr ratios, TOC and other chemical elements, environmental changes in the Hongjiannao Lake over the past 80 years were discussed. It is revealed that the lake formed during 1928-1952 A.D., characterized by relatively high Fe/Mn ratio and lower Rb/Sr ratio, MS value and lake productivity. During this period sandstorms were prevalent with three extremes occurring in 1936, 1939 and 1941 A.D., respectively. In the short time period of 1952-1960 A.D., the water level of the lake rose remarkably, as shown by a sharp increase in coarse slit and MS value, as well as the obvious dilution of geochemical element concentrations in lake sediments. The lake expansion is ascribed to both much more rainfall and human activities, especially in about 1958 A.D., when a great deal of channeled-off water from the around swamps was let to inpour into the lake. The lithological characteristics and sediment proxies reflect that the Hongjiannao Lake has already developed into a stable deep lake since the 1960s, characterized by the higher lake productivity and Rb/Sr ratio and lower Fe/Mn ratio. The frequency and intensity of sandstorms have also reduced greatly since the 1960s due to natural conservation activities. The drop of water level since the middle of the 1990s may be related to a warm and dry climate.展开更多
文摘By multi-proxy analysis of grain-size, magnetic susceptibility (MS), Fe/Mn and Rb/Sr ratios, TOC and other chemical elements, environmental changes in the Hongjiannao Lake over the past 80 years were discussed. It is revealed that the lake formed during 1928-1952 A.D., characterized by relatively high Fe/Mn ratio and lower Rb/Sr ratio, MS value and lake productivity. During this period sandstorms were prevalent with three extremes occurring in 1936, 1939 and 1941 A.D., respectively. In the short time period of 1952-1960 A.D., the water level of the lake rose remarkably, as shown by a sharp increase in coarse slit and MS value, as well as the obvious dilution of geochemical element concentrations in lake sediments. The lake expansion is ascribed to both much more rainfall and human activities, especially in about 1958 A.D., when a great deal of channeled-off water from the around swamps was let to inpour into the lake. The lithological characteristics and sediment proxies reflect that the Hongjiannao Lake has already developed into a stable deep lake since the 1960s, characterized by the higher lake productivity and Rb/Sr ratio and lower Fe/Mn ratio. The frequency and intensity of sandstorms have also reduced greatly since the 1960s due to natural conservation activities. The drop of water level since the middle of the 1990s may be related to a warm and dry climate.
