美國霍爾海洋科學研究所(Woods Hole Oceanographic Institution, WHOI)的科學家，最近在墨西哥灣超過海面下900公尺深的地方量測到一條超過35公里長的碳氫化合物污染柱，這條污染柱是BP深水地平線油井漏油的殘留物。
海面上的油污沉下去以後，到底跑到哪裡去了？這條2公里寬、200公尺高的碳氫化合物污染柱，可以部份回答這個近來引起熱烈關切的的問題。「這些量測結果顯示，這條污染油柱必須列入漏油污染物的流向記錄。」霍爾海洋科學研究所的海洋地質化學專家、同時也是調查漏油的專家瑞迪(Christopher Reddy)表示。瑞迪與同事們發表的這篇污染油柱研究論文，8月19日刊登於學術界的權威期刊《科學》(Science)期刊中。
這些研究學者量測並比對了污染柱內的石油碳氫化合物，用這些碳氫化合物當成調查工具，發現了這條污染物的來源就是爆炸的油井，而不可能是天然滲出的石油。不僅如此，他們更報告了深海微生物分解污染柱的速度比平常慢，很有可能這條污染柱已經出現了一陣子，並且還會持續存在一段時間。
霍爾海洋科學研究團隊用兩項先進的科技完成了他們的研究：可在深達海底4500公尺運作的水底獨立載運哨艇，以及名為TETHYS的水底質譜儀，尺寸相當於鞋盒的大小，可以在海水中立即辨識出微量的石油及其他化合物。
「我們已經明確地發現油柱不僅存在，而且還找出油柱的來源跟近場結構。」霍爾海洋科學研究院的應用海洋物理與工程系的卡密理(Richard Camilli)說道，卡密理是調查艇中首席科學家，也是這篇研究論文的主筆。
卡密理說，「六月的時候，我們觀察到油柱在油井爆炸地點的西南方以每小時約270公尺的緩慢速度遷移。」研究學者從油井附近5公里的地方開始追蹤，一直追蹤到離油井約35公里的地方，直到颶風Alex逼近，迫使他們不得不離開研究的地點。
瑞迪說，研究結果證實了一條沿續的污染柱確實存在，這條污染柱的石油碳氫化合物濃度不但「值得注意，並且測量得到」。石油碳氫化合物的濃度及分佈顯示了墨西哥灣中「污染柱不是因為天然滲出石油引起的」，卡密理補充。
污染柱的存在是否對墨灣造成重大威脅仍不明朗。瑞迪說，「我們不知道污染柱毒性有多強；我們也還不知道油柱是如何形成的，或為什麼形成的。但是知道油柱的尺寸、深度，以及油柱的去向將對回答許多這些問題來說極為重要。」
Scientists from the Woods Hole Oceanographic Institution have detected a plume of hydrocarbons that is at least 22 miles long and more than 3,000 feet below the surface of the Gulf of Mexico, a residue of the BP Deepwater Horizon oil spill.
The 1.2-mile-wide, 650-foot-high plume of trapped hydrocarbons provides at least a partial answer to recent questions asking where all the oil has gone as surface slicks shrink and disappear.
"These results indicate that efforts to book keep where the oil went must now include this plume" in the Gulf, said Christopher Reddy, a WHOI marine geochemist and oil spill expert and one of the authors of the study, which appears in the August 19 issue of the journal "Science."
The researchers measured distinguishing petroleum hydrocarbons in the plume and, using them as an investigative tool, determined that the source of the plume could not have been natural oil seeps but had to have come from the blown out well.
Moreover, they reported that deep-sea microbes were degrading the plume relatively slowly, and that it was possible that the plume had and will persist for some time.
The WHOI team accomplished their research using two advanced technologies: the autonomous underwater vehicle Sentry that can explore the ocean down to a depth of 14,760 feet; and an underwater mass spectrometer known as TETHYS, small enough to fit in a shoebox, that can instantly identify minute quantities of petroleum and other chemical compounds in seawater.
"We've shown conclusively not only that a plume exists, but also defined its origin and near-field structure," said Richard Camilli of WHOI's Applied Ocean Physics and Engineering Department, chief scientist of the cruise and lead author of the paper.
"In June, we observed the plume migrating slowly [at about 0.17 miles per hour] southwest of the source of the blowout," said Camilli.
The researchers began tracking it about three miles from the wellhead and out to about 22 miles (35 kilometers) until the approach of Hurricane Alex forced them away from the study area.
The study confirms that a continuous plume exists "at petroleum hydrocarbon levels that are noteworthy and detectable," Reddy said.
The levels and distributions of the petroleum hydrocarbons show that "the plume is not caused by natural seeps" in the Gulf of Mexico, Camilli added.
Whether the plume's existence poses a significant threat to the Gulf is not yet clear, the researchers say. "We don't know how toxic it is," said Reddy, "and we don't know how it formed, or why. But knowing the size, shape, depth, and heading of this plume will be vital for answering many of these questions."
