Bay Steven M, Zeng Eddy Y, Lorenson Thomas D, Tran Kim, Alexander Clark
Southern California Coastal Water Research Project, 7171 Fenwick Lane, Westminster, CA 92683, USA.
Mar Environ Res. 2003 Jul-Aug;56(1-2):255-76. doi: 10.1016/S0141-1136(02)00334-3.
Contaminant inputs from wastewater discharge, a major source of contamination to Santa Monica Bay (SMB), have declined drastically during the last three decades as a result of improved treatment processes and better source control. To assess the concomitant temporal changes in the SMB sediments, a study was initiated in June 1997, in which 25 box cores were collected using a stratified random sampling design. Five sediment strata corresponding to the time intervals of 1890-1920, 1932-1963, 1965-1979, 1979-1989, and 1989-1997 were identified using (210)Pb dating techniques. Samples from each stratum were analyzed for metals, 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its metabolites (DDTs), polychlorinated biphenyls (PCBs), and total organic carbon (TOC). Samples from the 1965-1979, 1979-1989, and 1989-1997 strata were also analyzed for polycyclic aromatic hydrocarbons (PAHs) and linear alkylbenzenes (LABs). Sediment metal concentrations increased from 1890-1979 and were similar during the time intervals of 1965-1979, 1979-1989, and 1989-1997, although the mass emissions of trace metals from sewage inputs declined substantially during the same time period. Trace organic contamination in SMB was generally highest in sediments corresponding to deposition during the years of 1965-1979 or 1979-1989 and showed a decline in concentration in the 1989-1997 stratum. Temporal trends of contamination were greatest in sediments collected from areas near the Hyperion Treatment Plant (HTP) outfall system and on the slope of Redondo Canyon. The highest contaminant concentrations were present in sediments near the HTP 7-mile outfall in the 1965-1979 stratum. Elevated trace metal and organic concentrations were still present in the 1989-1997 stratum of most stations, suggesting that sediment contaminants have moved vertically in the sediment column since sludge discharges from the 7-mile outfall (a dominant source of contamination to the bay) ceased in 1987. The widespread distributions of DDTs and PCBs in SMB and highly confined distribution of LABs around the HTP outfall system were indicative of a dispersal mechanism remobilizing historically deposited contaminants to areas relatively remote from the point of discharge.
废水排放是圣莫尼卡湾（SMB）的主要污染源，由于处理工艺的改进和更好的源头控制，在过去三十年中，污染物输入量已大幅下降。为了评估SMB沉积物中随之而来的时间变化，1997年6月启动了一项研究，采用分层随机抽样设计收集了25个箱式岩芯。利用（210）Pb测年技术确定了与1890 - 1920年、1932 - 1963年、1965 - 1979年、1979 - 1989年和1989 - 1997年时间间隔相对应的五个沉积层。对每个层的样品进行了金属、1,1,1 - 三氯 - 2,2 - 双（对氯苯基）乙烷（DDT）及其代谢物（DDTs）、多氯联苯（PCBs）和总有机碳（TOC）的分析。还对1965 - 1979年、1979 - 1989年和1989 - 1997年层的样品进行了多环芳烃（PAHs）和线性烷基苯（LABs）的分析。沉积物金属浓度从1890年至1979年有所增加，在1965 - 1979年、1979 - 1989年和1989 - 1997年时间间隔内相似，尽管同期污水输入的痕量金属排放量大幅下降。SMB中的痕量有机污染通常在对应于1965 - 1979年或1979 - 1989年沉积的沉积物中最高，并且在1989 - 1997年层中浓度有所下降。污染的时间趋势在从海波龙处理厂（HTP）排水口系统附近区域和雷东多峡谷斜坡采集的沉积物中最为明显。1965 - 1979年层中HTP七英里排水口附近的沉积物中污染物浓度最高。在大多数站点的1989 - 1997年层中仍存在痕量金属和有机物浓度升高的情况，这表明自1987年七英里排水口（该海湾的主要污染源）停止排放污泥以来，沉积物中的污染物已在沉积柱中垂直移动。DDTs和PCBs在SMB中的广泛分布以及LABs在HTP排水口系统周围的高度局限分布表明存在一种扩散机制，将历史沉积的污染物重新转移到相对远离排放点的区域。
