黑龙江省五大连池近百年环境变化研究

ENVIRONMENTAL CHANGES OF WUDALIANCHI LAKE INFERRED FROM LAKE SEDIMENTS IN THE PAST CENTURY

2009年6月用重力采样器在黑龙江省五大连池的三池和五池分别采集岩芯钻孔(wdlc-3孔和wdlc-5孔),运用核素^(210)Pb和^(137)Cs进行定年,同时分析了岩芯沉积物的理化指标,包括烧失量(LOI_(550℃))、总磷(TP)、总氮(TN)、粒度、金属元素和磁化率,研究近代五大连池湖泊环境演化过程以及人类活动的影响。结果表明:1920s～1950s,湖泊沉积物中值粒径较大,LOI_(550℃)和TN呈增长趋势,两孔Al和Fe含量呈增长趋势或处于高值阶段,可能与该期人类活动如开垦荒地有关;1950s～1980s,中值粒径较小或呈减少趋势,而TN,Al和Fe及重金属的含量呈增加趋势,人类活动如毁林、毁草开荒开始成为湖泊环境变化的主导因素;1980s～2000s阶段氮、磷增加更为迅速,重金属的含量也呈快速增长趋势,这可能与化肥、农药、含磷物品、含铅汽油的大量使用以及增强的工业活动有关;2000s以来,湖泊主要面临营养水平增加导致的富营养化问题。

Wudalianchi Lake（48°40′N - 48°47′N, 126°06′E - 126°15′E） is located in Wudalianehi City, Heilongjiang Province, China. The lake is composed of five small lakes,with the third lake area being 8.2km^2 ,and the fifth lake area being 5.3km^2. Two sedimentary cores,named wdlc-3 and wdlc-5 ,were collected from the third and fifth lake （wdlc-3, 48°43′39.72″ N, 126°12′56.84″ E, 49cm; wdlc-5, 48°46′31.19″ N, 126°8′19.61″ E, 43cm ） using gravity corer in June 2009, respectively. Both cores were sectioned at an interval of 1.0cm.LOI550℃ （loss on ignition） , total phosphorus （ TP）, total nitrogen （ TN ） , susceptibilitie, grain size distribution and elements were analyzed to construct environmental changes of Wudalianchi Lake. Sediment chronology was established based on the highest 137Cs activity peak （ 1963A. D. ） , the first ^137Cs activity appearance （ 1952A. D. ） and ^210Pb data. The average sediment rate is 0.28g/cm^2· a or 0.59cm/a, and 0.25g/cm^2· a or 0.55cm/a for the wdlc-3 and wdlc-5 cores in the past century. Combined with the sediment age, environmental changes of Wudalianehi Lake were reconstructed. The results showed that the environmental history could be divided into four stages as follows： 1920s- 1950s, median diameter of sediments was large, TN and LOI550℃ showed increased trends, Al and Fe contents of core sediment also increased,which indieats that lake environmental changes were possibly related with human activity such as land reclamation. 1950s - 1980s, human activity （such as deforestation, destruction of grassland） became the main influences which led to TN, Al and Fe contents to increase. However, median diameter was small. 1980s - 2000s, total nitrogen and phosphorus increased more rapidly, heavy metals also showed an increase trend, which could be attributed to extensive use of fertilizers, pesticides, phosphorus-containing items, leaded gasoline,and development of industry. Since 2000s,eutrophication has been the most important problem due to extensive input of nutrient loads to Wudalianehi Lake.