Fate and Transport of Hydrophobic Organic Chemicals in the Lower Passaic River: Insights from 2,3,7,8-Tetrachlorodibenzo-p-Dioxin

The fate and transport of hydrophobic organic chemicals (HOCs) is particularly complex in estuaries because of bidirectional longitudinal currents, density stratification, the tendency to trap sediments, and significant dilution in the downstream bay or ocean. Investigations of HOCs in estuaries are further complicated because HOCs typically enter from multiple sources. The distribution of contaminants in estuarine sediment beds reflect a time integration of a complex balance of time- and space-variable fate and transport processes and loading history. A unique opportunity to study HOC fate and transport exists in the Lower Passaic River (LPR), where a pesticide manufacturer was the dominant source of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) to the estuary and the distribution of this “tracer of opportunity” provides insights about fate and transport processes in estuarine systems. This paper presents observed sediment 2,3,7,8-TCDD patterns within the LPR and the adjacent Newark Bay, and interprets them in terms of fate and transport processes that likely distributed the contaminant from its dominant source, drawing upon other physical datasets as needed. Major observations include that estuarine transport processes have distributed 2,3,7,8-TCDD approximately 18 km upstream of the source and downstream across Newark Bay, and that, generally, HOC trapping processes within the LPR have been highly effective, particularly near the 2,3,7,8-TCDD source and in downstream areas. The present LPR surface sediment 2,3,7,8-TCDD distribution indicates spatially variable recovery, which appears broadly driven by historical net sedimentation patterns, though the dominant processes may be shifting as the system continues to evolve.     

Reconstructing historical trends in metal input in heavily-disturbed,contaminated estuaries: studies from Bilbao,Southampton Water and Sicily

Estuaries may be important reservoirs for contaminants as they tend to act as sinks for fine, contaminant-reactive sediments, and, historically, they have acted as centres for industrial and urban development. Analysis of dated sediment cores from these areas may allow historical trends in heavy metal input to be reconstructed, and recent and historical inputs of metal contaminants to be compared. Undisturbed saltmarsh settings have been used widely in the reconstruction of historical trends in metal input as saltmarshes provide a stable, vegetated substrate of dominantly fine sediments, and are less prone to erosion and reworking than adjacent mudflat areas. In comparison, much less research on historical pollution trends has been undertaken at estuarine sites which are prone to severe local disturbance, such as intertidal areas which are routinely dredged or where sedimentary processes have been modified by human activities such as shipping, salt working, port activities, land claim etc. This paper assesses the usefulness of ²¹⁰Pb and ¹³⁷Cs dating, combined with geochemical studies, in reconstructing historical trends in heavy metal input and sediment accretion in 3 heavily-modified, industrialised estuarine areas in Europe: the Bilbao estuary (Spain), Southampton Water (UK), and the Mulinello estuary (Sicily). Of these sites, only a salt marsh core from the Mulinello estuary provides a high-resolution record of recent heavy metal inputs. In Southampton Water only a partial record of changing metal inputs over time is retained due to land-claim and possible early-diagenetic remobilisation, while at Bilbao the vertical distribution of heavy metals in intertidal flats is mainly controlled by input on reworked sediment particles and variations in sediment composition. Where ¹³⁷Cs and ²¹⁰Pb distributions with depth allow a chronology of sediment deposition to be established, and early-diagenetic remobilisation has been minimal, mudflat and saltmarsh cores from even the most heavily-disturbed estuarine sites can provide useful information on variations in historical contaminant input. When the sediments have been vigorously mixed or reworked, large-scale compositional variations are present, or significant early-diagenetic remobilisation has occurred, however, only general information on the scale of contamination can be obtained.     

Heavy metal distribution and accumulation in two Spartina sp.-dominated macrotidal salt marshes from the Seine estuary (France) and the Medway estuary (UK)

The upper intertidal zone, and salt marshes in particular, have been shown by numerous authors to be effective medium to long-term storage areas for a range of contaminants discharged or transported into the estuarine environment. A detailed understanding of the specific controls on the trapping and storage of contaminants, however, is absent for many estuarine systems. This paper examines heavy metal distribution and accumulation in two contrasting Spartina sp.-dominated macrotidal salt marsh systems – a rapidly prograding, relatively young marsh system at the Vasiere Nord, near the mouth of the Seine estuary, France, and a more mature, less extensive marsh system in the Medway estuary, UK. The spatial distribution of the heavy metals Zn, Cu, Pb, Ni and Co is assessed and compared in both systems via detailed surface sampling and analysis, while the longer-term accumulation of these metals and its temporal variability is compared via analysis of dated sediment cores. Of the two sites studied, the more extensive marsh system at the Vasiere Nord in the Seine estuary shows a clear differentiation of heavy metals across the marsh and fronting mudflat, with highest metal concentrations found in surface sediments from the more elevated, interior marsh areas. At Horrid Hill in the Medway estuary, the spatial distribution of heavy metals in surface sediments is more irregular, and there is no clear relationship between heavy metal concentration and site elevation, with average concentrations similar in the marsh and fronting mudflats. Sediment core data indicate that the more recent near-surface sediments at Horrid Hill are clearly more contaminated than those at greater depth, with most heavy metal contamination confined to the upper 20 cm of the sediment column (with peak metal input in the late 1960s/early 1970s). In contrast, due to extremely rapid sediment accretion at the mouth of the Seine, heavy metal distribution with depth at the Vasiere Nord site is relatively erratic, with metal concentrations showing a general increase with depth. These sediments provide little information on temporal trends in heavy metal loading to the Seine estuary. Overall, heavy metal concentrations at both sites are within typical ranges reported for other industrialised estuaries in NW Europe.     

Reactive Transport Modeling of Subaqueous Sediment Caps and Implications for the Long-Term Fate of Arsenic, Mercury, and Methylmercury

A 1-D biogeochemical reactive transport model with a full set of equilibrium and kinetic biogeochemical reactions was developed to simulate the fate and transport of arsenic and mercury in subaqueous sediment caps. Model simulations (50?years) were performed for freshwater and estuarine scenarios with an anaerobic porewater and either a diffusion-only or a diffusion plus 0.1-m/year upward advective flux through the cap. A biological habitat layer in the top 0.15?m of the cap was simulated with the addition of organic carbon. For arsenic, the generation of sulfate-reducing conditions limits the formation of iron oxide phases available for adsorption. As a result, subaqueous sediment caps may be relatively ineffective for mitigating contaminant arsenic migration when influent concentrations are high and sorption capacity is insufficient. For mercury, sulfate reduction promotes the precipitation of metacinnabar (HgS) below the habitat layer, and associated fluxes across the sediment–water interface are low. As such, cap thickness is a key design parameter that can be adjusted to control the depth below the sediment–water interface at which mercury sulfide precipitates. The highest dissolved methylmercury concentrations occur in the habitat layer in estuarine environments under conditions of advecting porewater, but the highest sediment concentrations are predicted to occur in freshwater environments due to sorption on sediment organic matter. Site-specific reactive transport simulations are a powerful tool for identifying the major controls on sediment- and porewater-contaminant arsenic and mercury concentrations that result from coupling between physical conditions and biologically mediated chemical reactions.     

Spatio-temporal dynamics of heavy metals in sediments of the river estuarine system: Mahanadi basin (India)

Dynamics of heavy metals in the surface sediments of Mahanadi river estuarine system were studied for three different seasons. This study demonstrates that the relative abundance of these metals follows in the order of Fe > Mn > Zn > Pb > Cr > Ni ≥ Co > Cu > Cd. The spatial pattern of heavy metals supported by enrichment ratio data, suggests their anthropogenic sources possibly from various industrial wastes and municipal wastes as well as agricultural runoff. The metal concentrations in estuarine sediments are relatively higher than in the river due to adsorption/accumulation of metals on sediments during saline mixing, while there is a decreasing trend of heavy metal concentrations towards the marine side. The temporal variations for metals, such as Fe, Mn, Zn, Ni and Pb exhibit higher values during monsoon season, which are related to agricultural runoff. Higher elemental concentrations are observed during pre-monsoon season for these above metals (except Ni) at the polluted stations and for metals, such as Cr, Co and Cd at all sites, which demonstrate the intensity of anthropogenic contribution. R-mode factor analysis reveals that “Fe–Mn oxy hydroxide”, “organic matter”, “CaCO₃”, and “textural variables” factors are the major controlling geochemical factors for the enrichment of heavy metals in river estuarine sediment and their seasonal variations, though their intensities were different for different seasons. The relationships among the stations are highlighted by cluster analysis, represented in dendrograms to categorize different contributing sites for the enrichment of heavy metals in the river estuarine system.     

Storage of sediment-associated nutrients and contaminants in river channel and floodplain systems

Samples of fine-grained channel bed sediment and overbank floodplain deposits were collected along the main channels of the Rivers Aire (and its main tributary, the River Calder) and Swale, in Yorkshire, UK, in order to investigate downstream changes in the storage and deposition of heavy metals (Cr, Cu, Pb, Zn), total P and the sum of selected PCB congeners, and to estimate the total storage of these contaminants within the main channels and floodplains of these river systems. Downstream trends in the contaminant content of the <63 μm fraction of channel bed and floodplain sediment in the study rivers are controlled mainly by the location of the main sources of the contaminants, which varies between rivers. In the Rivers Aire and Calder, the contaminant content of the <63 μm fraction of channel bed and floodplain sediment generally increases in a downstream direction, reflecting the location of the main urban and industrialized areas in the middle and lower parts of the basin. In the River Swale, the concentrations of most of the contaminants examined are approximately constant along the length of the river, due to the relatively unpolluted nature of this river. However, the Pb and Zn content of fine channel bed sediment decreases downstream, due to the location of historic metal mines in the headwaters of this river, and the effect of downstream dilution with uncontaminated sediment. The magnitude and spatial variation of contaminant storage and deposition on channel beds and floodplains are also controlled by the amount of <63 μm sediment stored on the channel bed and deposited on the floodplain during overbank events. Consequently, contaminant deposition and storage are strongly influenced by the surface area of the floodplain and channel bed. Contaminant storage on the channel beds of the study rivers is, therefore, generally greatest in the middle and lower reaches of the rivers, since channel width increases downstream. Comparisons of the estimates of total storage of specific contaminants on the channel beds of the main channel systems of the study rivers with the annual contaminant flux at the catchment outlets indicate that channel storage represents <3% of the outlet flux and is, therefore, of limited importance in regulating that flux. Similar comparisons between the annual deposition flux of specific contaminants to the floodplains of the study rivers and the annual contaminant flux at the catchment outlet, emphasise the potential importance of floodplain deposition as a conveyance loss. In the case of the River Aire the floodplain deposition flux is equivalent to between ca. 2% (PCBs) and 36% (Pb) of the outlet flux. With the exception of PCBs, for which the value is ≌0, the equivalent values for the River Swale range between 18% (P) and 95% (Pb). The study emphasises that knowledge of the fine-grained sediment delivery system operating in a river basin is an essential prerequisite for understanding the transport and storage of sediment-associated contaminants in river systems and that conveyance losses associated with floodplain deposition exert an important control on downstream contaminant fluxes and the fate of such contaminants.     

Sediment evolution and habitat function of organic-rich muds within the Albemarle estuarine system,North Carolina

The analyses of 248 samples have revealed that the composition and distribution patterns of sediments within the Albemarle estuarine system (AES) represent a complex interaction between multiple sediment sources, basin morphology and evolution, and associated estuarine processes. Three sediment end-member types are dominant: sand, peat, and organic-rich mud (ORM). Throughout the AES, shallow perimeter platforms and associated sediment-bank shorelines are eroded into Pleistocene units. Shoreline recession supplies sand to the platforms and mud to the central basins; these sediments mix with suspended sediment from the fluvial drainages. Swamp forest-peat and marsh-peat shorelines are actively eroding and supply fine organic detritus to produce the dominant ORM sediment in the central basins. Perimeter platform sands grade into ORM on the platform slope. ORM constitutes about 70% of the benthic habitats within the AES and has an average composition of 76.2% inorganic mud, 13.1% sand, and 10.7% organic matter. The characteristics of ORM greatly affect the benthic community structure, chemical quality of the sediments, and the water quality of the estuary. ORM readily moves in and out of the water column in response to natural and anthropogenic activities, affecting water column turbidity and trace and major element geochemistry. Organic matter and clay minerals in ORM are chemically reactive and interact with the water column to adsorb or release contaminants, nutrients, and gases. Thus, ORM acts as both a sink and source for many different chemical constituents in the water column and plays important, but poorly understood, functions in the physical and chemical dynamics of estuarine ecosystems.     

人类活动影响下伶仃洋沉积格局演变特征

根据2016年伶仃洋128个表层沉积物粒度参数以及前人对伶仃洋表层沉积物的研究成果,结合Flemming沉积动力判别图解和粒径趋势分析模型（GSTA）,分析伶仃洋40年来的沉积格局演变特征,并探讨了人类活动在伶仃洋沉积格局演变中的作用。结果显示:1）2016年,伶仃洋表层沉积物中粉砂组分含量最多（56.67%）,黏土组分含量其次（26.08%）,砂含量最少（17.23%）,湾内表层沉积物总体较细,主要有砂、砂—粉砂—黏土、砂质粉砂、粉砂质砂和黏土质粉砂5种类型,各类型沉积物呈现斑块状分布。2）近40年来,伶仃洋表层沉积物的平均粒径、粒级组分的空间格局发生了显著变化,从之前的条带状分布变为斑块状分布,但沉积格局的剧烈演变主要集中于2004—2016年这十多年间,Flemming三角图分区变化显示出40年来伶仃洋沉积环境整体表现出动力增强的趋势。3）受人类大规模采砂影响,中滩区域原有的完整沉积中心被分散,分别向北和向南形成“两格局、三中心”的新型沉积模式,从而改变伶仃洋的沉积物源—汇过程。4）伶仃洋沉积物空间分布、沉积动力环境、运移趋势等特征的变化与采砂、航道浚深等人类活动有着密切的联系,反映出人类工程活动已成为影响伶仃洋沉积格局演变的重要因素。     

亚热带中小型山溪性河流—宽陆架系统“源—汇”过程

中小型山溪性河流易受极端事件和人类活动影响,且对环境变化响应敏感,在大陆边缘物质循环过程中发挥着十分重要的作用,但学术界对它们的重视程度不够。以闽江—东海陆架系统为例,通过资料收集、遥感解译、样品采集与分析等方法,系统研究了亚热带中小型山溪性河流—宽陆架系统的“源—汇”过程。研究结果表明,人类活动引起的土地利用变化使得闽江入海径流量和泥沙通量在波动中略有增加,但水库的建设显著减少了入海泥沙通量,并且减弱了水沙通量的季节差异,河流入海泥沙通量变化对流域人类活动敏感且响应迅速;河口水体环境、悬浮体浓度、沉积物粒度组成及陆源有机碳埋藏的空间分布格局均显示,闽江入海泥沙主要分布在闽江河口附近海域,其中粗颗粒泥沙在水动力的作用下主要堆积在河口水下三角洲平原及前缘,细颗粒泥沙主要堆积在水下三角洲前缘斜坡及前三角洲附近海域,仅有少量细颗粒泥沙沿岸向外输运并沿途沉积,与大河流—宽陆架系统及中小型山溪性河流—窄陆架系统显著不同。河口人类活动及极端事件通过改变沉积物组成、环境动力、入海泥沙通量等方式对河流—陆架系统的“源—汇”过程产生显著影响。在当前流域来沙量锐减、河口地区海砂开采等人类活动强度增大的情况下,有必要加强相关研究。     

Effects of estuarine organic matter biogeochemistry on the bioaccumulation of PAHs by two epibenthic species

Polycyclic aromatic hydrocarbon (PAH) biota-sediment accumulation factors (BSAF) were quantified in sediments from two sites in southeastern Louisiana in a 14 d microcosm study usingPalaemonetes pugio, andRangia cuneata and two radiolabeled PAHs, phenanthrene and benzo[a]pyrene (b[a]p). For both PAHs studied, mean BSAFs were significantly higher (p<0.0001) in both organisms in sediments from Bayou Trepagnier, (BSAF=0.628 g OC g TLE⁻¹), a brackish swamp, compared to Pass Fourchon (0.065 g OC g TLE⁻¹), a coastal salt marsh. In order to explain observed patterns in BSAFs, organic carbon-normalized PAH distribution coefficients between the sediment and freely dissolved phases (K_OC)_OBS were determined as well as the various geochemical variables of particulate and dissolved organic matter (POM and DOM, respectively). These included analyses of particle surface area, total organic carbon (TOC), carbon to nitrogen ratios (C∶N), and dissolved organic carbon (DOC). Bayou Trepagnier was higher in surface area, TOC, C∶N, as well as DOC suggesting that the difference in BSAFs may be attributed to compositional differences in POM and DOM between sites. We can not exclude the possibility that other factors (such as differences in organism behavior resulting from contrasting sediment characteristics) were responsible for BSAFs varying between the two sites. Phenanthrene BSAFs were typically higher than b[a]p BSAFs, suggesting contaminants were limited in their desorption from sediment particles as a function of PAH molecular weight. Mean BSAFs for both PAHs were higher on Day 7 than on Day 14. The reason for this decrease is unclear, but did not appear to be due to organisms becoming increasingly stressed in the microcosms. Visual observations indicated that animals remained feeding while no decreases in organism total lipid levels were detected. The trends in BSAFs between sites and over the time course of this experiment suggest that contaminant bioaccumulation in estuarine systems should not be considered to be an equilibrium process.     

Relationship between organic matter and mercury in recent lake sediment: The physical–geochemical aspects

This study addresses the physical geochemical aspects of the relationship between Hg and organic matter in recent sediment from eutrophic lakes in central Alberta, Canada. The types of organic matter in the sediment are classified based on their degree of thermal degradation and their petrographical characteristics. This study uniquely applies the methods conventionally used in petroleum geosciences (Rock-Eval^® analyses and organic petrology) to investigate the relationship between various types of organic matter and the concentration of Hg in sediment.The results show that the total organic carbon (TOC) in sediment represents the sum of various organic compounds, which may play a completely different role in the distribution and accumulation of Hg. Strong correlations between TOC and the concentration of Hg in the studied sediment arise mainly from the thermally labile portion of organic matter released during pyrolysis under 300 °C. These compounds primarily consist of easily degradable algal-derived lipids and various pigments, which are petrographically described as soluble organic matter (SOM). The preserved SOM in sediment is commonly entrapped within the cell walls of phytoplankton and also appear as surface coating on sediment particles. The strong affinity between Hg and SOM is due not only to its chemical reactivity, but also to the physical characteristic of these labile compounds. The SOM may provide a substrate with enormous surface area by concentrating on the finer sediment size fractions and potentially acting as a “concentrator” for Hg and other organic-associated elements. Lastly, the quantity of the SOM has been calculated as an “elemental concentrator” portion of the TOC, which plays the most important role in the distribution of Hg in sediment.     

Models of natural organic matter and interactions with organic contaminants

Adsorption of organic contaminants onto soils, sediments and other particulates has the potential to be a major controlling factor in their bioavailability, fate and behavior in the environment. Models for estimating the amount and stability of sorbed organic contaminants based on the fraction of organic carbon in a soil or sediment can oversimplify the process of sorption in the environment. In order to help understand sorption of organic contaminants in soils and sediments, we modeled various components of natural organic matter (NOM) that are possible substrates for sorption. These substrates include soot particles, lignin, humic and fulvic acids. The molecular scale interactions of selected aromatic hydrocarbons with different substrates were also simulated. Results of the simulations include the 3-D structures of the NOM components, changes in structure with protonation state and solvation and the sorption energy between PAH and substrate. This last parameter is an indicator of the amount of contaminant that will sorb and the energy required to free the contaminant from the substrate. Although the simulation results presented in this paper represent a first-order examination of NOM and contaminant interactions, the findings highlight a number of essential features that should be included in future molecular models of NOM and contaminant sorption.     

The role of bioindicators in estuarine management

Estuarine organisms can be considered three ways as bioindicators—first, as indicators of a defined set of environmental conditions, second, as indicators of contaminant loads on the system, and third, as indicators of the overall health of the system. By their very nature, estuarine organisms are eurytolerant and this, along with the various stratagems that have evolved to cope with the problems of life in estuaries results in a confusing picture for the estuarine manager. The recommended bioindicators for estuarine conditions are plankton; for contaminant loads, a range of species with different feeding types; and for system status, a eurytolerant species, such as the musselMytilus edulis for laboratory monitoring or a “target” species such as the clamMacoma balthica for field monitoring. However, it would be unwise to rely on a single indicator, and the recommendation is that the final choice, and preferably choices, be tailored to the desired goal.     

Episodic and Long-Term Sediment Transport Capacity in The Hudson River Estuary

A tidally averaged model of estuarine dynamics is used to estimate sediment transport in the Hudson River estuary over the period 1918 to 2005. In long-term and seasonal means, along-channel gradients in sediment flux depend on the estuarine salinity gradient and along-channel depth profile. Lateral depth variation across the estuary affects the near-bottom baroclinic circulation and consequently the direction of net sediment flux, with generally up-estuary transport in the channel and down-estuary transport on the shoals. Sediment transport capacity in the lower estuary depends largely on river discharge, but is modified by the timing of discharge events with respect to the spring–neap cycle and subtidal fluctuations in sea level. Sediment transport capacity also depends on the duration of high-discharge events relative to the estuarine response time, a factor that varies seasonally with discharge and estuarine length. Sediment fluxes are calculated with the assumption that over long periods, the system approaches morphological equilibrium and sediment accumulation equals sea level rise. The inferred across- and along-channel distributions of sediment erodibility correspond with observations of bed properties. Equilibrium is assumed at long time scales, but at annual to decadal time scales the estuary can develop an excess or deficit of sediment relative to equilibrium. On average, sediment accumulates in the estuary during low- and high-discharge periods and is exported during moderate discharge. During high-discharge periods, maximum export coincides with maximum sediment supply from the watershed, but the nearly cubic discharge dependence of fluvial sediment supply overwhelms the roughly linear increase in estuarine transport capacity. Consequently, sediment accumulates in the estuary during the highest flow conditions. Uncertainty remains in the model, particularly with sediment properties and boundary conditions, but the results clearly indicate variability in the sediment mass balance over long time scales due to discharge events.     

Relationships Among Exceedences of Sediment Guidelines,the Results of Ambient Sediment Toxicity Tests,and Community Metrics in Estuarine Systems

To use bioassessments to help diagnose or identify the specific environmental stressors affecting estuaries, we need a better understanding of the relationships among sediment chemistry guidelines, ambient toxicity tests, and community metrics. However, this relationship is not simple because metrics generally assess the responses at the community level of biological organization whereas sediment guidelines and ambient toxicity tests generally assess or are based on the responses at the organism level. The relationship may be further complicated by the influence of other chemical and physical variables that affect the bioavailability and toxicity of chemical contaminants in the environment. Between 1990 and 1993, the U.S. Environmental Protection Agency (USEPA) conducted an Environmental Monitoring and Assessment Program (EMAP) survey of estuarine sites in the Virginian Province of the eastern United States. The surveys collected data on benthic assemblages, physical and chemical habitat characteristics, and sediment chemistry and toxicity. We characterized these estuarine sites as affected by sediment contamination based on the exceedence of sediment guidelines or on ambient sediment toxicity tests (i.e., 10-day Ampelisca abdita survival). Then, benthic invertebrate metrics were compared among affected and unaffected sites to identify metrics sensitive to the contamination. A number of benthic invertebrate metrics differed between groups of sites segregated using the organism-level measures whereas other metrics did not. The difference among metrics appears to depend on the sensitivity of the individual metrics to the stressor gradient represented by metals or persistent organic toxics in sediments because the insensitive metrics do not effectively quantify the changes in the benthic invertebrate assemblage associated with these stressors. The significant relationships suggest that a relationship exists between the organism-level effects assessed by chemistry or ambient toxicity tests and the community-level effects assessed by community metrics and that the organism-level effects are predictive, to some extent, of community-level effects.     

水体沉积物环境质量基准建立方法研究进展

近20年来,不同的研究机构和研究者先后提出了多种水体沉积物环境质量基准建立方法,这些方法大多产生于北美地区,都是以底栖动物为保护目标,直接或间接地以污染物的生物效应为依据,可划分为2类：即基于沉积物毒性试验、现场生物效应观察和效应发生频率统计的方法;基于平衡分配理论,污染物在沉积物固相—间隙水相间的分配关系的方法。各种方法都有其适用范围和局限性。目前研究中存在的主要问题是：无法明确污染物—生物效应间的因果关系,难以确定影响污染物生物有效性的因素及其影响程度。因此,至今还没有提出一种可广泛应用的沉积物环境质量基准建立方法。建立统一的沉积物毒性试验、测定标准,提高数据的可靠性,重视不同基准建立方法的结合,将是今后研究的重点和发展方向。     

Distributions of pesticides and organic contaminants between water and suspended sediment,San Francisco Bay,California

Suspended-sediment and water samples were collected from San Francisco Bay in 1991 during low river discharge and after spring rains. All samples were analyzed for organophosphate, carbamate, and organochlorine pesticides; petroleum hydrocarbons; biomarkers; and polynuclear aromatic hydrocarbons. The objectives were to determine the concentrations of these contaminants in water and suspended sediment during two different hydrologic conditions and to determine partition coefficients of the contaminants between water and sediment. Concentrations of hydrophobic contaminants, such as polynuclear aromatic hydrocarbons, varied with location of sample collection, riverine discharge, and tidal cycle. Concentrations of hydrophobic contaminants in suspended sediments were highest during low river discharge but became diluted as agricultural soils entered the bay after spring rains. Polynuclear aromatic hydrocarbons defined as dissolved in the water column were not detected. The concentrations sorbed on suspended sediments were variable and were dependent on sediment transport patterns in the bay. In contrast, the relatively hydrophilic organophosphate pesticides, such as chlorpyrifos and diazinon, has a more uniform concentration in suspended sediment. These pesticides were detected only after spring rains. Most of the measured diazinon, at least 98% for all samples, was in the dissolved phase. Measured partition coefficients for diazinon generally were uniform, which suggests that suspended-sediment concentrations were close to equilibrium with dissolved concentrations. The concentration of diazinon sorbed to suspended sediments, at any given sampling site, was driven primarily by the more abundant solution concentration. The concentrations of diazinon sorbed to suspended sediments, therefore, were independent of the patterns of sediment movement.     

Sedimentary processes and trace metal contaminants in the buccaneer oil/gas field,northwestern gulf of Mexico

Sediments are the ultimate sink for contaminants in the marine environment, and physical processes of sedimentation influence the distribution and accumulation of these contaminants. Evaluation of contaminant levels in sediments is one approach to assessing environmental impact; data interpretation depends on consideration of sediment texture and mineralogy, however, which profoundly influence chemical composition. In this study, comparison of potentially contaminated sediments from the production field with control populations was done only within the context of similar (as to texture and organic carbon and carbonate content) sample groups as determined by cluster analysis. Ba, Cd, and Sr are identified as contaminants. Supported by the identification of a well-crystallized expandable clay—possibly bentonite—drilling fluids are a potential source of Ba. Ba and Sr may be unnaturally high because of their abundance in discharged produced formation waters, but may also be naturally controlled by the unique faunal assemblage associated with the structures. Cd is probably derived from corrosion of the structures and assorted debris on the seafloor. In general, contamination is limited to an area within 100 m of the platforms. Furthermore, substantial erosion around platforms has probably effectively removed and dispersed the bulk of the contaminants introduced into the marine environment by the offshore exploration/production operations.     

Drivers of Change in Shallow Coastal Photic Systems: An Introduction to a Special Issue

Coastal ecosystems are characterized by relatively deep, plankton-based estuaries and much shallower systems where light reaches the bottom. These latter systems, including lagoons, bar-built estuaries, the fringing regions of deeper systems, and other systems of only a few meters deep, are characterized by a variety of benthic primary producers that augment and, in many cases, dominate the production supplied by phytoplankton. These “shallow coastal photic systems” are subject to a wide variety of both natural and anthropogenic drivers and possess numerous natural “filters” that modulate their response to these drivers; in many cases, the responses are much different from those in deeper estuaries. Natural drivers include meteorological forcing, freshwater inflow, episodic events such as storms, wet/dry periods, and background loading of optically active constituents. Anthropogenic drivers include accelerated inputs of nutrients and sediments, chemical contaminants, physical alteration and hydrodynamic manipulation, climate change, the presence of intensive aquaculture, fishery harvests, and introduction of exotic species. The response of these systems is modulated by a number of factors, notably bathymetry, physical flushing, fetch, sediment type, background light attenuation, and the presence of benthic autotrophs, suspension feeding bivalves, and fringing tidal wetlands. Finally, responses to stressors in these systems, particularly anthropogenic nutrient enrichment, consist of blooms of phytoplankton, macroalgae, and epiphytic algae, including harmful algal blooms, subsequent declines in submerged aquatic vegetation and loss of critical habitat, development of hypoxia/anoxia particularly on short time scales (i.e., “diel-cycling”), fish kills, and loss of secondary production. This special issue of Estuaries and Coasts serves to integrate current understanding of the structure and function of shallow coastal photic systems, illustrate the many drivers that cause change in these systems, and synthesize their varied responses.     

多年冻土区石油污染物迁移过程试验研究

中俄原油管道原油泄漏造成的环境污染和环境岩土工程问题是目前迫切需要解决的重要问题。通过淋滤作用下的石油污染物迁移过程室内模拟试验,研究了石油污染物在冻土区的迁移过程和迁移特征,研究发现：石油污染物在迁移过程中,油、水、气三相流体存在一个动态的平衡过程,其三者共同占据土样中的孔隙空间;石油污染物在冻土区迁移主要经历3个过程：吸附、迁移和聚集;石油污染物在迁移过程中,其各个成分和各烃类化合物迁移能力都有所不同,烃类化合物中碳数和烃类结构影响其迁移速度;冻土层对石油污染物的迁移具有明显的阻碍作用,可有效防治土壤深层次污染。研究成果为冻土区石油污染物多相流（油、水、气）水热质迁移动力学模型的建立以及石油污染引起的岩土工程特性变化等研究奠定了重要的基础