摘要
从波罗的海西北部和斯德哥尔摩群岛采集两个年度纹层沉积物岩心,对其中所含多氯联苯(PCB)和滴滴涕(DDT)的时间趋势进行研究,研究结果表明,纹层沉积物是检测疏水性有机污染物(HOC)时间趋势的有效手段。基于干物质重量,这两个岩心的PCB和DDT含量趋势与所报道波罗的海本体西北部深海生物群内的趋势十分相似,尽管从29世纪70年代以来含量降低的量仅约为深海生物群中降低量之半。这类物质在沉积物中的累积趋势与深海生物群中的浓度趋势并不一致,但与气候相关的侵蚀/再悬浮动力过程密切相关。与波罗的海本体西北部相比,已证实群岛区的总累积速率高出8倍多(分别为885和108g/m^2·a)。因在近海区和沿岸区PCB和DDT含量相似,而且PCB和DDT的埋藏速率与总累积速率密切相关,与近海区域相比,群岛区的污染沉积物埋藏高出好几倍。群岛PCB和DDT的高埋藏量表明,污染物是由外海向群岛输入的。尽管富营养过程引起污染物的清除在波罗的海也可能发生,但自然进程使得该证据变得模糊不清。
Temporal trend studies of PCBs and DDTs in two annually laminated sediment cores from the offshore NW Baltic proper and the Stockholm archipelago demonstrate that studies of laminated sediments are useful tools for detecting time trends of HOCs. The concentration trends of PCBs and DDTs, on a dry weight basis, from the two cores show quite large similarities to trends reported in pelagic biota from the NW Baltic proper, although the reduction in concentrations from the 1970s and onwards is approximately half of the reductions seen in biota. The sediment accumulation trend for these substances was not coupled to the concentration trend in biota but is closely linked to climate-related erosion/resuspension dynamics. The gross accumulation rate in the archipelago area proved to be 8 times higher compared to that of the offshore NW Baltic proper (885 and 108 g m-2 water area yr-1, respectively). Since PCB and DDT concentrations were similar in offshore and coastal areas, and the burial rates of PCB and DDT were closely linked to gross accumulation rates, the sediment burial of contaminants in relation to water area was severalfold higher in the archipelago compared to the offshore area. The high burial of sPCB and sDDT in the archipelago indicated an import of contaminants from the open sea to the archipelago. Although eutrophication-induced scavenging of contaminants may have occurred in the Baltic Sea, natural processes have obscured evidence of this.
