Canuel Elizabeth A, Lerberg Elizabeth J, Dickhut Rebecca M, Kuehl Steven A, Bianchi Thomas S, Wakeham Stuart G
Virginia Institute of Marine Science, School of Marine Science, College of William and Mary, P.O. Box 1346, Gloucester Point, VA 23062, USA.
Mar Pollut Bull. 2009;59(4-7):154-63. doi: 10.1016/j.marpolbul.2009.03.025. Epub 2009 May 5.
We used the Sacramento-San Joaquin River Delta CA (Delta, hereafter) as a model system for understanding how human activities influence the delivery of sediment and total organic carbon (TOC) over the past 50-60 years. Sediment cores were collected from sites within the Delta representing the Sacramento River (SAC), the San Joaquin River (SJR), and Franks Tract (FT), a flooded agricultural tract. A variety of anthropogenic tracers including (137)Cs, total DDE (Sigma DDE) and brominated diphenyl ether (BDE) congeners were used to quantify sediment accumulation rates. This information was combined with total organic carbon (TOC) profiles to quantify rates of TOC accumulation. Across the three sites, sediment and TOC accumulation rates were four to eight-fold higher prior to 1972. Changes in sediment and TOC accumulation were coincident with completion of several large reservoirs and increased agriculture and urbanization in the Delta watershed. Radiocarbon content of TOC indicated that much of the carbon delivered to the Delta is "pre-aged" reflecting processing in the Delta watershed or during transport to the sites rather than an input of predominantly contemporary carbon (e.g., 900-1400 years BP in surface sediments and 2200 yrs BP and 3610 yrs BP at the base of the SJR and FT cores, respectively). Together, these data suggest that human activities have altered the amount and age of TOC accumulating in the Delta since the 1940s.
我们以加利福尼亚州萨克拉门托 - 圣华金河三角洲（以下简称三角洲）作为一个模型系统，以了解在过去50 - 60年里人类活动是如何影响沉积物和总有机碳（TOC）的输送的。从三角洲内代表萨克拉门托河（SAC）、圣华金河（SJR）以及一片被淹没的农业区——弗兰克斯区域（FT）的地点采集了沉积物岩芯。使用了多种人为示踪剂，包括铯 - 137（¹³⁷Cs）、总滴滴涕（ΣDDE）和溴化二苯醚（BDE）同系物来量化沉积物堆积速率。这些信息与总有机碳（TOC）剖面相结合，以量化TOC的堆积速率。在这三个地点，1972年之前沉积物和TOC的堆积速率要高出四到八倍。沉积物和TOC堆积的变化与几个大型水库的建成以及三角洲流域农业和城市化的增加同时发生。TOC的放射性碳含量表明，输送到三角洲的大部分碳是“预老化的”，这反映了在三角洲流域或运输到这些地点的过程中的处理情况，而不是主要输入的当代碳（例如，表层沉积物中为公元前900 - 1400年，SJR和FT岩芯底部分别为公元前2200年和3610年）。总之，这些数据表明自20世纪40年代以来，人类活动已经改变了在三角洲积累的TOC的数量和年代。
