Spatial scales and evolution of stormwater plumes in Santa Monica Bay

Rainfall during winter storms produces extensive turbid, freshwater plumes in the coastal waters of the Southern California Bight. When the plumes result from urban runoff they contain toxic pollutants along with pathogenic bacteria and viruses, often resulting in closure of public beaches. We examined the spatial structure and evolution of stormwater plumes in Santa Monica Bay in 1996. The plumes resulted from freshwater discharge from the Ballona Creek and Malibu Creek watersheds which supply approximately 60% of the freshwater runoff to Santa Monica Bay. The spatial scales of the plumes were determined using shipboard measurements of water properties obtained from towyo transects and surface underway sampling. Salinity maps showed that the plumes typically extended 4-7 km offshore, consistent with scaling by the internal Rossby radius of deformation. Plumes extended along shore 10 km or more. Generally the plumes occupied the upper 10 m of the water column. The persistence time of a plume offshore of Ballona Creek was about three days based on a sequence of surveys in March 1996 following rainfall of about 21 mm. Limited comparison of plumes from Ballona Creek, which drains a developed watershed, and Malibu Creek, which drains a rural watershed, suggested that Malibu Creek required greater rainfall to produce an offshore plume. A stormwater plume offshore of Malibu Creek was observed on both sides of the creek mouth, possibly due to freshwater discharge from smaller surrounding watersheds or advection of freshwater discharges from the east and south. Plumes offshore of Ballona Creek mainly resulted from the creek itself and usually extended northward from the creek mouth, consistent with the wind forcing and the Coriolis acceleration.     

Water quality impacts of stormwater discharges to Santa Monica Bay

Urban stormwater runoff is a major source of contaminants to southern California's coastal waters, yet little is known about the fate and effects of these discharges. A 3-year multidisciplinary project was conducted to investigate the dispersion of stormwater plumes in Santa Monica Bay and the resultant impacts on the water column and benthos. This paper describes the toxicity component of the study. Sea urchin fertilization toxicity tests were conducted on stormwater from the two largest discharges into the bay: Ballona Creek, which drains a highly urbanized watershed, and Malibu Creek, which receives runoff from a largely undeveloped watershed. Every sample of Ballona Creek stormwater tested was toxic (usually >5 toxic units), while Malibu Creek stormwater had a lower frequency and magnitude of toxicity (usually <4 toxic units). Surface water samples collected within the Ballona Creek stormwater discharge plume were always toxic whenever the concentration of stormwater in the plume exceeded 10%. The toxic portion of the Ballona Creek stormwater plume extended more than 4 km offshore on one occasion. Toxicity identification studies indicated that zinc was the primary cause of toxicity in both Ballona Creek stormwater and the discharge plume. No acute sediment toxicity (10-day amphipod survival) was present in the study area, although interstitial water toxicity was present at some stations located near the mouth of Ballona Creek. Differences in watershed characteristics likely were responsible for the greater toxicity of the Ballona Creek stormwater discharge plume. The Ballona Creek watershed contained a greater degree of urbanization (83% versus 12% for Malibu Creek) and the presence of a network of concrete flood control channels resulted in a stormwater plume containing elevated concentrations of toxins that received less initial dilution (compared to Malibu Creek) in the nearshore environment.     

江苏弶港盐沼风车河潮沟地貌与动力演化

联合国环境署(1990)在题为“海相环境的状况”的报告中指出,世界人口约一半集中在海岸地区,因而这些地区人口压力巨大,同时受到污染、风暴潮、地面沉降的威胁,以及高地灌溉水资源枯竭的影响;在低地海岸、河滩和湿地,海平面的上升将会给沿岸城市的工农业生产及人民生活带来极其严重的后果。而盐沼-潮沟体系则是淤泥质海岸缓冲、削减波浪-潮流能量的重要地貌系统,对海岸的保护起着至关重要的作用。潮沟常常贯穿盐沼与泥坪(或沙坪),成为沟通盐沼-泥坪体系物质能量交换的纽带;在淤涨型淤泥质海岸上,细颗粒泥沙被涨潮流沿潮沟输送到盐沼上,结果使盐沼不断向海淤进。而当海平面上升时,盐沼-潮沟系统功能又发生改变,成为削减潮汐能量的“装置”。Pethick(1980,1992)研究了英国Norfolk盐沼潮沟水流的特征,并提出了流速的预报模型;Healey等(1981)在观测中发现了一些与模型不符的情况。本文从地貌和动力方面研究了江苏淤泥质海岸弶港盐沼风车河潮沟的地貌演变与动力演化的关系,以及水动力与地貌因素之间的相互响应机制。     

Structure and chemistry of sediments in Belfast Lough,a semi-enclosed marine bay

In a study of the benthic environment of Belfast Lough the structure of the subtidal sediment was examined along with its content of organic matter and selected metals (Cr, Mn, Ni, Cu, Zn, Pb). A wide range of sediment types occurred within the lough but the mean grain sizes for individual sites lay predominantly within the size classes of fine sand, very fine sand and silt. The content of organic matter and metals in the sediments showed strong positive correlations with each other and with the content of silt/clay. Both organic matter and metals decreased in concentration in a seawards direction. The content of organic matter lay generally within the range of 1–5% which is normally associated with shelf sediments, but constituted up to 12% of the sediment in the docks area. Likewise, metals were usually within the range reported within other nearshore coastal waters of the U.K., but sediments in the docks area and inner lough were enriched with several metals. Cluster analysis identified four major subdivisions in the lough which were distinctly different in their contents of silt/clay, organic matter and metals.     

Sewage sludge impact on sediment quality and benthic assemblages off the Mediterranean coast of Israel-a long-term study

The distributions of benthic assemblages, heavy metals and organic carbon (Corg) in sediments were examined during a long-term study at a sewage sludge disposal site off the Mediterranean coast of Israel. The disposal of sewage sludge has a marked but localized, seasonally dependent, impact on the benthic assemblages and sediment quality. Elevated concentrations of Corg, Hg, Cd, Cu, Zn, Pb, and to a lesser degree Ni in the sediments were detected mostly northward of the sewage outfall, in the direction of the prevalent longshore current. High concentrations of Corg and metals were reflected by elevated populations of tolerant and opportunistic polychaetes in spring and by an azoic zone in fall. The impacted area extended mainly towards the north (up to ca. 4 km) and to a lesser extent south of the outfall (up to ca. 2.5 km). No evidence of increased accumulation of sewage sludge with time was found, nor of pollutants associated with it. Principal component analysis (PCA) grouped the anthropogenic metals and Corg with infaunal abundance for the spring surveys, while biotic diversity was negatively correlated with the pollutants. In the PCA of fall surveys, abundance was negatively correlated with the pollutants, decreasing with increased concentration of Corg and anthropogenic metals. We suggest that the seasonal pattern shown by infaunal abundance, anthropogenic metals and Corg is due to the stratification of the water column from spring to fall on one-hand and winter storms on the other. Winter storms resuspend and disperse the fine organic particles, sweeping the site clean of sludge; accumulation of sludge takes place throughout the quiescent periods of the year, when stratification is reestablished. The disposal site is dispersive and the spatial extent of the impacted area varies seasonally and interannually. This monitoring study, in addition to addressing specific questions about sewage sludge impact, represents an unusually large and unique set of long-term measurements that will serve as a basis to evaluate the site recovery following the cessation of disposal.     

Heavy metals in Changjiang estuarine and offshore sediments: responding to human activities

The Changjiang (Yangtze) estuarine and offshore sediments were analyzed for total heavy metals concentrations and chemical fractions.Distributions of heavy metals show typical banded diffusion pattern,with high concentrations near the river mouth and following a decreasing trend in the offshore direction.According to chemical fractions,Fe/Mn oxide fraction is the major non-residual fraction in the Changjiang estuarine and offshore sediments.Higher percentage of non-residual fraction of Pb implies that,the industrial contaminations transported via the atmosphere and river input,may affect the non-residual fraction of heavy metals.Over past fifteen years,the concentration of Pb normalizing to Al presents significant increasing trend,corresponding to the effect of human activities.By comparison of heavy metals fractions in 2003 to 2006,it has been realized that increasing water and sediment may cause a higher percentage non-residual fraction of Cu in the southern part of offshore muddy sediments.     

夏季珠江口沉积物?水界面重金属分布特征及其影响因子研究

珠江口受复杂径?潮动力耦合作用的影响,河口重金属迁移转化机制复杂多变。本文基于2018年夏季珠江口及其邻近海域海水和沉积物的调查资料,研究了珠江口多动力因子驱动下7种重金属元素汞、砷、锌、镉、铅、铜和铬的沉积、迁移和积累机制。结果表明:相比于溶解态重金属（水体中）的赋存状况,吸附态重金属（沉积物中）更稳定,污染也更严重;采用皮尔逊相关分析和主成分分析计算出重金属元素与环境因子之间的响应关系,溶解态重金属主要以稀释混合过程为主,吸附态重金属受有机碳和氧化还原作用的影响较大;沉积物?水界面重金属的分配系数显示出铅和铬易被吸附在颗粒物上,而镉和汞易溶解在水体中,揭示了河口复杂动力影响下元素在不同介质的形态转换特征;除了镉?铬、镉?铜和铬?砷这3组元素间不显著相关,其他元素间的显著相关性表明了重金属元素具有相似的来源,并采用主成分分析探讨了重金属元素的潜在来源,主要来源为工业废水,农业和大气沉降次之。研究结果可为有效控制重金属的排放和河口污染治理提供重要支撑。     

Environmental status of Daya Bay surface sediments inferred from a sequential extraction technique

The chemical partitioning of 12 trace metals (Ba, Cd, Co, Cu, Mn, Mo, Ni, Pb, Sc, Sr, U, Zn) in 9 surface sediments from Daya Bay, northern South China Sea, was studied by a four-step sequential extraction technique to assess their environmental/pollution status. The studied metals take on different fraction composition patterns, and some of them show significant spatial variation especially for Cd. A majority of the studied metals can be considered immobile because of their high percentages in the residual fraction. It seems that the Daya Bay surface sediments have not yet been polluted by the studied heavy metals which are used as parameters to classify marine sediment quality, i.e., Cd, Cu, Ni, Pb and Zn. For all metals except for Pb, the extent of anthropogenic influences on their total concentrations in the Daya Bay surface sediments is generally imperceptible. The metals’ potential risks to the environment were assessed, and the results showed that they have generally no risk or low risk except for Cd, Mn and Sr.     

Accumulation of sediment,organic matter and trace metals with space and time,in a creek along Mumbai coast,India

Two core sediment samples; one from inner part (ManI) and the other closer to the mouth (ManII); were collected from the intertidal regions of Manori, a tidally influenced creek near Mumbai, India. Both the cores were subjected to various geochemical analyses to determine parameters such as pH, sediment components, total organic carbon, total nitrogen, total phosphorus and selected metals viz., Fe, Mn, Cu, Pb, Co, Ni, Zn, Cr, Al, Ca and V. Analysis of ²¹⁰Pb activity was employed to assess the sediment deposition trend of the area. The data was further processed using factor and cluster analyses. The results indicate that the sediments from site ManI, had finer sediment composition, higher porosity, organic matter and metal contents but exhibited an erratic decline in ²¹⁰Pb activity downcore. Also ManI showed higher C:N ratio and enrichment factor values as compared to site ManII. The inner area (ManI) probably received a greater input of organic matter from the erosion of terrestrial matter as well as domestic and industrial discharge. Sediments from site ManII had typical marine organic matter composition (lower C:N ratio). The concentration of metals at this site was also low indicating the contents were getting diluted by freshwater and seawater mixing.     

Effects of fish farming on the biological and geochemical properties of muddy and sandy sediments in the Mediterranean Sea

The aim of this paper was to test how benthic fauna and biogeochemical properties of sediment will vary in response to similar levels of organic enrichment (induced by fish farming) as a function of bottom-habitat type (i.e., mud versus seagrass/coarse sediments), distance from the enrichment source and depth. Our results showed that samples from silty sediments in the vicinity of fish farms have higher TOC and TON values, higher oxygen consumption, higher PO₄ release and lower benthic diversity. In this context muddy sites are more likely to be identified as impacted/critical, than coarse sediment ones.     

南澳岛海域表层沉积物重金属分布、富集与污染评价

南澳岛是广东南澳县的主岛, 周边海域的环境保护被置于当地社会经济发展的重要位置。为此, 2004年 5月、7月选择以水产养殖为主的后江湾和白沙湾及以旅游为主的青澳湾作为研究对象, 对南澳岛海域重金属的 含量、分布、富集及污染状况进行了调查与评价。结果表明该海域重金属元素的平均含量为Cd: 0.19mg.kg-1, Cr: 26.86mg.kg-1, Cu: 20.71mg.kg-1, Ni: 22.78mg.kg-1, Pb: 35.67mg.kg-1, Zn: 79.48mg.kg-1, 低于近岸经济发达海域, 但高于受人类活动影响较小的外海; 在分布特征上表现为湾口高于湾内, 养殖区高于非养殖区的总趋势, 但在各海湾之间重金属含量并无显著差异, 表明南澳岛海域重金属主要来源于地表径流输入。该海域以城市污水中代表元素Cu (Cf = 2.75), Pb (Cf = 2.27)富集为主; 以海洋沉积物质量标准、沉积物质量基准和美国太平洋沿岸基线值评价, 南澳岛海域环境质量均处于健康状态, 但其潜在污染效应仍值得关注。     

江苏大丰海岸碱蓬滩潮沟及滩面的沉积动力特征

根据2002年7月在江苏大丰碱蓬滩潮沟观测的水文、悬沙、底质等资料,分析了潮沟的输水、输沙特征及悬沙和底质在粒径组成上的关系,结果表明,潮沟在流速、悬沙浓度、输水、悬沙输运、底质活动性等方面具有明显的涨落潮不对称.滩面归槽水占潮沟落潮输水量的33%,由此造成的悬沙输运量占潮沟落潮悬沙输运量的20%,这是导致潮沟涨落潮输水输沙不对称的主要因素.在一个潮周期中潮沟的净输水、净悬沙输运方向与滩面相反,指向落潮方向.悬沙和底质组成以粉砂和黏土为主,潮沟和滩面的悬沙粒径组成差别很小.悬沙是滩面底质的主要物质来源,两者在粒径组成上存在着必然联系,沉积物粒径与该粒级在底质中的含量与在悬沙中的含量之比具有明显的幂函数关系.     

Mechanisms of land–sea interactions – the distribution of metals and sedimentary organic matter in sediments of a river-dominated Mediterranean karstic estuary

This paper examines disposal of metals and the origin, characteristics, and distribution of sedimentary organic matter (SOM) in a Mediterranean karstic estuary in the north-eastern Adriatic. This environment offers a real-time, small model system for studies of geochemical processes in microtidal Mediterranean estuaries that are infilling with sediments and classified as river-dominated disequilibrium estuaries. The results have shown that the longitudinal distribution of heavy metals in sediments follows the sedimentation dynamics and deposition pattern of river-borne, clay mineral particles. The highest concentration of metals was found in the restricted upper part of the estuary, characterized by rapid deposition of clay particles and terrestrial sedimentary organic matter, and decreases toward the open sea. The vertical distribution of metals in sediment cores depends on the prevailing pH and Eh conditions. Significant increases of the concentrations of metals in the uppermost strata are the result of recent anthropogenic inputs. The share of the terrestrial component in SOM, estimated by N/C_org atomic ratios and δ¹³C values, decreases with distance from the river mouth. The small vertical variation in δ¹³C values of SOM indicates that a fast sedimentation rate overrides the diagenetically determined decomposition. The results obtained indicate that river-borne inorganic particles, natural terrigenous organic material, and anthropogenic metal loads are trapped in sediments of the estuarine system. Under the prevailing conditions, there is negligible transport towards the open sea.     

Historical contamination of PAHs, PCBs, DDTs, and heavy metals in Mississippi River Delta, Galveston Bay and Tampa Bay sediment cores

Profiles of trace contaminant concentrations in sediment columns can be a natural archive from which pollutant inputs into coastal areas can be reconstructed. Reconstruction of historical inputs of anthropogenic chemicals is important for improving management strategies and evaluating the success of recent pollution controls measures. Here we report a reconstruction of historical contamination into three coastal sites along the US Gulf Coast: Mississippi River Delta, Galveston Bay and Tampa Bay. Within the watersheds of these areas are extensive agricultural lands as well as more than 50% of the chemical and refinery capacity of the USA. Despite this pollution potential, relatively low concentrations of trace metals and trace organic contaminants were found in one core from each of the three sites. Concentrations and fluxes of most trace metals found in surface sediments at these three sites, when normalized to Al, are typical for uncontaminated Gulf Coast sediments. Hydrophobic trace organic contaminants that are anthropogenic (polycyclic aromatic hydrocarbons, DDTs, and polychlorinated biphenyls) are found in sediments from all locations. The presence in surface sediments from the Mississippi River Delta of low level trace contaminants such as DDTs, which were banned in the early 1970's, indicate that they are still washed out from cultivated soils. It appears that the DDTs profile in that sediment core was produced by a combination of erosion processes of riverine and other sedimentary deposits during floods. Most of the pollutant profiles indicate that present-day conditions have improved from the more contaminated conditions in the 1950-1970's, before the advent of the Clean Water Act.     

Radiotracer estimates of benthic activity effects on trace metal diffusion into mangrove sediments

Potential influences of the whole benthic organisms' activity (i.e., coupled faunal and microbial effects) on ⁵⁸Co, ⁵¹Cr and ⁶⁵Zn diffusion into surface mangrove sediment layers (0–6 cm depth) were evaluated in 36 h experiments. Benthic activity indices (BAI) were proposed, calculated as the relative percent difference between untreated sediments and formaldehyde-treated sediments data in relation to untreated sediments data. Benthic activity was estimated as responsible for 32%–44% of total inventories within sediments, being the chromate anion spiked the less affected radiotracer, while ⁶⁵Zn was the most sensitive. Benthic activity was quantitatively evidenced as a control on trace metal diffusion into the sediments, contributing to determine the sediment role as a metal sink. This influence can also affect metal potential bioavailability, considering that recently diffused metals can be more readily available to biological uptake.     

Preliminary results on suspended sediment transport by tidal currents in Gomso Bay,Korea

This study briefly investigated sediment transport by tidal currents in Gomso Bay, on the mid-west coast of Korea during the summer season. Hydrodynamic measurements with benthic tripods (TISDOSs) show that near-bed suspended sediments are transported toward the bay mouth along the low-water line of tidal flats in the southern part of the bay, while they are directed offshore in front of the major tidal channel at the bay mouth according to tidal asymmetry. However, suspended sediments in the main body of sea water, observed from transect and anchor-site measurements, indicate a consistent incoming toward the uppermost tidal flats. A brief episode of relatively strong winds from the west and southeast displays that wind waves can yield the near-bed suspended sediment concentrations (SSC) overwhelming the SSC by tidal currents alone in the remaining duration.     

秋季长江口水体颗粒有机碳年际变化及影响因素分析

根据2007—2012年长江口及其邻近海域4个航次(11月)调查资料,探讨了长江口秋季颗粒有机碳(POC)时空分布特征;结合长江口环境要素和陆源输入(径流、输沙),分析了秋季POC分布的主要影响因素。结果表明:(1)2007—2012年秋季长江口POC浓度范围为0.03—16.95mg/L,均值2.30mg/L,底层POC浓度高于表层。长江口表层POC浓度存在显著的年际变化特征。(2)长江口区POC分布呈现沿长江径流入海方向降低的趋势,高值区出现在口门附近偏南部水域。口门内和近岸水域POC显著高于近海水域。口门水域POC年际间相对稳定,近岸和近海水域年际变化显著。(3)长江口POC分布与盐度呈非保守性变化,悬浮物是POC分布的主要控制因素,多数年份POC与叶绿素a相关程度较弱。(4)河口来水来沙量对POC浓度具有较强的制约性,径流的主要影响区域在口门内和近岸区,输沙的主要影响区域在最大浑浊带和长江口北部水域。(5)入海输沙量与长江口水域POC相关性最强。咸淡水交汇引起的悬浮物沉积和沉积物的再悬浮强度决定口门内水域POC浓度,浑浊度较高的近岸水体POC对陆源输入泥沙的依赖性较强,长江口外侧海域初级生产力水平成为POC浓度的重要影响因素。     

Hydrocarbons in the sediments of Port Valdez,Alaska: Consequences of five years' permitted discharge

Hydrocarbons have been investigated in the sediments of Port Valdez, Alaska after three to five years of oil terminal operation with a routine daily discharge of 170 kg of petroleum residue in an otherwise undeveloped area. Surficial benthic sediments (0–5 cm) and core segments down to 30 cm have been analyzed. Information about total hydrocarbons, unresolved complex mixture, normal alkanes, pristane, phytane, hopanes and polycyclic aromatic hydrocarbons indicates that petroleum, biogenic hydrocarbons, and combustion-derived aromatic hydrocarbons are present in sediments around the terminal at concentrations up to 218 μg g^?1 dry sediment. The vertical, horizontal and temporal distributions of anthropogenic hydrocarbons indicate that most of the sedimentary hydrocarbon accumulation has occurred within 1 km of the terminal. A simple calculation suggests that less than 3% of the total oil discharged during routine operations of the terminal has entered the sediments of Port Valdez. For comparison sediment hydrocarbon accumulation associated with a nearby small boat harbor was also examined.     

锦州湾沾污沉积物急性毒性的海洋端足类检验

１９９２年９月￣１９９３年１月对锦州湾沾污沉积物的海洋端足类急性毒性效应进行了研究。从锦州湾湾顶到湾口沿西南－－东北方向每２ｋｍ等距离采集２７个表层沉积我校 品,应用海洋端足类Ａ ｍｐｅｌｉｓｃａ ａｂｄｉｔａ对这些样品进行了１０ｄ直流式急性毒性检验,检验指标为死亡率。结果表明,五里河河口处受试生物死亡率最高,为１００％,从湾顶该河口处沿东北方向随着距离增加,死亡率逐渐递减,笔架山处最低,仅为２．     

Acid-leachable trace metals in sediments from an industrialized region (Ennore Creek) of Chennai City,SE coast of India: An approach towards regular monitoring

The article presents the results for enrichment of acid-leachable trace metals (ALTMs) from Ennore Creek in north Chennai, a metropolis on the southeast coast of India. ALTMs Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn and Cd along with sediment texture, OC and CaCO₃ were analyzed in surface sediments collected during two different seasons, pre-monsoon (PRM) and post-monsoon (POM) seasons to identify and observe the input of trace metals in the creek from various sources in the city limits. The most prominent feature of the ALTMs is the enrichment of Fe, Cr, Cu, Ni, Pb and Zn in the sediments, which is mainly attributed to the intense industrial activities around Chennai, and to the rapid industrialization policies. The ALTMs also indicate their association with the finer fractions, OC and Fe–Mn oxyhydroxides. The enrichment is very well supported by the correlation, grouping and clustering of ALTMs in statistical analysis. The differential behavior of ALTMs in POM season compared to PRM season is possibly due to the excess level of industrial effluents in the channel feeding Ennore Creek. Comparative results of ALTMs with other estuarine regions also indicate that the study area has been enriched with trace metals during the past two decades. The results of the present study suggest the need for a regular monitoring program which will help to improve the quality of Ennore Creek.