1991年皮纳图博火山灰沉降物对南海海洋环境及硅藻生长的影响

通过对菲律宾皮纳图博(Pinatubo)火山1991年6月爆发前后南海表层沉积物及沉降颗粒物中的硅藻丰度及群落组成进行分析,试图揭示皮纳图博火山爆发对南海硅藻生长的影响。研究发现,火山爆发后南海沉积物中硅藻相对丰度显著减少,原因主要在于皮纳图博火山喷发物大量沉积于南海深海,显著提高了南海沉积速率,同时稀释了沉积物中生源物质的含量。进一步对火山爆发前后同期南海中部深海沉降颗粒物开展研究发现,火山爆发次年同期沉降颗粒物总通量以及生物硅通量明显增加,而硅藻及其他硅质生物相对丰度和通量均显著降低,其中硅藻相对丰度从2.20×10^(8)枚·g^(-1)降到5.48×10^(7)枚·g^(-1),通量从2.90×10^(7)枚·m^(-2)·d^(-1)降到8.57×10^(6)枚·m^(-2)·d^(-1)。1年后的南海中部深海沉降颗粒物中仍然有大量火山玻璃的存在,可能是导致湿化学法测量生物硅含量明显增加的主要原因,而硅藻乃至所有硅质生物通量及丰度的显著降低可能与火山灰沉降的负面影响有关,也可能与1991年厄尔尼诺对南海海洋环境的影响有关。总之,1991年6月皮纳图博火山爆发后南海的沉积物硅藻及沉降颗粒物硅藻丰度都出现了显著降低,但具体的环境调控机制仍有待进一步深入研究。

Evidence of the 1991 Pinatubo volcanic eruption in South Polar snow

Traces of tephra and increased sulfate (SO42-) concentrations were identified in the1992-1994 snow layers in 2 firn cores from South Pole. The deposition of the Pinatubo SO42-aerosol was delayed due to the long transport to the high south latitudes and its initial existence at high altitudes in the Antarctic atmosphere. Electron microscopic analyses show that the element composition of the tephra is identical to that of volcanic ash found near the Pinatubo volcano in Philippines. Detailed stratigraphic snow sampling resolved the Pinatubo signal from that of Cerro Hudson eruption during August 1991 in Chile. The South Pole sulfate flux from Pinatubo is calculated to be (10.9 ±1.1) kg·km-2, while the Hudson sulfate flux is (3.2 ± 1.1) kg·km-2. This information will be useful to estimating the magnitudes of the past volcanic eruptions recorded in Antarctic ice core.