Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research, IDÆA-CSIC, 08034 Barcelona, Catalonia, Spain.
Environ Sci Technol. 2012 Mar 6;46(5):2624-32. doi: 10.1021/es2038189. Epub 2012 Feb 24.
Settling particles were collected by an array of sediment trap moorings deployed along the Cap de Creus (CCC) and Lacaze-Duthiers (LDC) submarine canyons and on the adjacent southern open slope (SOS) between October 2005 and October 2006. This array collected particles during common settling processes and particles transferred to deep waters by dense shelf water cascading (DSWC). Polychlorobiphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), chlorobenzenes (CBzs)--pentachlorobenzene and hexachlorobenzene--and hexachlorocyclohexanes were analyzed in all samples. The results show much higher settling fluxes of these compounds during DSWC than during common sedimentation processes. The area of highest deposition was located between 1000 and 1500 m depth and extended along the canyons and outside them showing their channelling effects but also overflows of dense shelf water from these canyons. Higher fluxes were observed near the bottom (30 m above bottom; mab) than at intermediate waters (500 mab) which is consistent with the formation and sinking of dense water close to the continental shelf and main displacement through the slope by the bottom. DSWC involved the highest settling fluxes of these compounds ever described in marine continental slopes and pelagic areas, e.g., peak values of PCBs (960 ng · m(-2) · d(-1)), DDTs (2900 ng · m(-2) · d(-1)), CBzs (340 ng · m(-2) · d(-1)) and lindane (180 ng · m(-2) · d(-1)).
沉降颗粒由 2005 年 10 月至 2006 年 10 月期间沿卡普德克鲁兹（CCC）和拉卡泽-迪图埃斯（LDC）海底峡谷以及相邻的南部开阔坡（SOS）部署的一系列沉降捕集器收集。该系统在普通沉降过程和通过密集陆架水级联（DSWC）转移到深海的颗粒中收集颗粒。多氯联苯（PCBs）、滴滴涕及其代谢物（DDTs）、氯苯（CBzs）——五氯苯和六氯苯——以及六氯环己烷均在所有样本中进行了分析。结果表明，在 DSWC 过程中，这些化合物的沉降通量远高于普通沉降过程。沉积量最高的区域位于 1000 至 1500 米深度之间，并沿着峡谷延伸，显示出它们的通道效应，但也有来自这些峡谷的密集陆架水溢出。在靠近底部（距底部 30 米；mab）处观察到的通量高于在中间水域（500 mab）处观察到的通量，这与在大陆架附近形成和下沉密集水以及通过底部主要通过斜坡置换的过程一致。DSWC 涉及到海洋大陆斜坡和远洋地区这些化合物的沉降通量的最高值，例如 PCB（960ng·m(-2)·d(-1)）、DDTs（2900ng·m(-2)·d(-1)）、CBzs（340ng·m(-2)·d(-1)）和林丹（180ng·m(-2)·d(-1)）的峰值。
