Tidal river sediments in the Washington,D.C. area. I. Distribution and sources of trace metals

Thirty-three bottom sediments were collected from the Potomac and Anacostia rivers, Tidal Basin, and Washington Ship Channel in June 1991 to define the extent of trace metal contamination and to elucidate source areas of sediment contaminants. In addition, twenty-three sediment samples were collected directly in front of and within major storm and combined sewers that discharge directly to these areas. Trace metals (e.g., Cu, Cr, Cd, Hg, Pb, and Zn) exhibited a wide range in values throughout the study area. Sediment concentrations of Pb ranged from 32.0 μg Pb g^?1 to 3,630 μg Pb g^?1, Cd from 0.24 μg Cd g^?1 to 4.1 μg Cd g^?1, and Hg from 0.13 μg Hg g^?1 to 9.2 μg Hg g^?1, with generally higher concentrations in either outfall or sewer sediments compared to river bottom-sediments. In the Anacostia River, concentration differences among sewer, outfall, and river sediments, along with downriver spatial trends in trace metals suggest that numerous storm and combined swers are major sources of trace metals. Similar results were observed in both the Tidal Basin and Washington Ship Channel. Cadminum and Pb concentrations are higher in specific sewers and outfalls, whereas the distribution of other metals suggests a more diffuse source to the rivers and basins of the area. Cadmium and Pb also exhibited the greatest enrichment throughout the study area, with peak values located in the Anacostia River, near the Washington Navy Yard. Enrichment factors decrease in the order: Cd>Pb>Zn>Hg>Cu>Cr. Between 70% and 96% of sediment-bound Pb and Cd was released from a N₂-purged IN HCl leach. On average, ≤40% of total sedimentary Cu was liberated, possibly due to the partial attack of organic components of the sediment. Sediments of the tidal freshwater portion of the Potomac estuary reflect a moderate to highly components area with substantial enrichments of sedimentary Pb, Cd, and Zn. The sediment phase that contains these metals indicates the potential mobility of the sediment-bound metals if they are reworked during either storm events or dredging.     

Tidal river sediments in the Washington,D.C. area. III. Biological effects associated with sediment contamination

Sediment toxicity and benthic macroinvertebrate community structure were measured as one component of a study cohceived to determine the distribution and effect of sediment contamination in tidal freshwater portions of the Potomac and Anacostia rivers in the Washington, D.C., area. Samples were collected at 15 sites. Analyses included a partial life cycle (28 d) whole sediment test using the amphipod Hyalella azteca (Talitridae) and an assessment of benthic community structure. Survival and growth (as estimated by amphipod length) were experimental endopoints for the toxicity test. Significant mortality was observed in 5 of 10 sites in the lower Anacostia River basin and at the main channel Potomac River site. Sublethal toxicity, as measured by inhibition of amphipod growth, was not observed. Toxicity test results were in general agreement with synoptically measured sediment contaminant concentrations. Porewater total ammonia (NH₃+NH₄ ⁺) appears to be responsible for the toxicity of sediments from the Potomac River, while correlation analysis and simultaneously extracted metals: acid volatile sulfide (SEM∶AVS) results suggest that the toxicity associated with Anacostia River sediments was due to organic compounds. Twenty-eight macroinvertebrate taxa were identified among all sites, with richness varying from 5 to 17 taxa per site. Groups of benthic assemblages identified by group-average cluster analysis exhibited variable agreement with sediment chemical and sediment toxicity results. Integration of toxicological, chemical, and ecological components suggests that adverse environmental effects manifest in the lower Anacostia River benthos result from chemical contamination of sediment.     

Distribution and sources of phosphorus in tidal river sediments in the Washington, DC, Area

 Sediments in the rivers and basins around Washington, DC, have high concentrations of phosphorus, which, based on geographic distributions, is largely derived from urban runoff and municipal sewage. Dissolved-particulate phosphate exchange reactions and biological uptake of dissolved phosphorus from the water column may be an added source of phosphorus to the sediments. Concentrations of total sedimentary phosphorus ranged from 24 to 56 μm P/g-dw, and were highest in areas near combined sewer outfalls. As a part of this study, sedimentary phosphorus was fractionated into Fe-P, Ca-P, Al-P, and organic phases using a selective-sequential leaching procedure. The distribution of the phases in all sediments analyzed follow the order , Fe-P>Ca-P>Al-P. Spatial variations in the amounts of phosphorus in the different phases is related to the sources of phosphorus to the area. The proportions of occluded Al-P and organic P are 10–20% of the total P, respectively. This suggests that phosphorus from natural sources is small compared to anthropogenic inputs in this area. The high leachable Fe-P and Ca-P in these sediments might contribute a substantial amount of P to the water column under conditions of remobilization. Received: 20 February 1996 · Accepted: 2 April 1996     

Magnetic properties of river sediments and their relationship with heavy metals and organic matter in the urban area in Lanzhou, China

As the largest industrial city locating in the Northwestern China, Lanzhou has become one of the most seriously polluted cities in the world. In this study, investigations were performed on the magnetic properties, heavy metals and organic matter contents of a total of 23 sediment samples collected from eight selected rivers in the Lanzhou urban area. The results of the study indicate that the magnetic properties of the sediment samples are predominated by low-coercivity magnetite. The river sediments are classified into three types, i.e., downstream polluted, upstream polluted, and less affected, based on the contribution from anthropogenic activities in different segments of the river as indicated by the variation of magnetic mineral concentration parameters. Moreover, a strong linear positive correlation exists among some of the magnetic parameters and organic matter content, heavy metals (Cr, Ni, Pb, Zn, Fe) and total enrichment factor (R) of the bulk deposit samples, which indicates that environmental magnetic technology may be an effective method for distinguishing source apportionment and monitoring river sediment pollution in urban areas.     

Compositions and sources of extractable organic matter in Mesopotamian marshland surface sediments of Iraq: II. Polar compounds

The concentrations of polar organic compounds including n-alkanoic acids, n-alkanols, steroids and triterpenoids were determined in extracts of shallow sediments from the Mesopotamian marshlands of Iraq. The sediments were collected by a stainless steel sediment corer, extracted with a dichloromethane and methanol mixture (3:1 v:v) by ultrasonic agitation and then analyzed by gas chromatography–mass spectrometric (GC–MS). The analysis results showed that the n-alkanoic acids ranged from C₈ to C₂₀ with concentrations of 7.8 ± 1.2 μg/g sample, whereas the concentrations of n-alkanols, which ranged from C₁₂ to C₃₉ were from 28.6 ± 4.3 to 121.7 ± 18.3 μg/g sample. The steroids and triterpenoids included stenols, stanols, stenones, stanones, tetrahymanol, tetrahymanone and extended ββ-hopanes. The total concentrations of steroids and triterpenoids ranged from 26.8 ± 4.1 to 174.6 ± 26.2 μg/g and from 0.74 ± 0.11 to 11.2 ± 1.7 μg/g sample, respectively. The major sources of these lipids were from natural vegetation, microbial (plankton) residues and bacteria in the sediments, with some contribution from anthropogenic sources (livestock, sewage and petroleum). Further studies of these wetlands are needed to characterize the input rate, transformation and diagenesis of the organic matter and to assess its various sources.     

Effects of organic matter heterogeneity on sorption and desorption of organic contaminants by soils and sediments

This review highlights the major progress over the last decade on characterization of geochemically heterogeneous soil/sediment organic matter (SOM) and the impacts of SOM heterogeneity on sorption and desorption of hydrophobic organic contaminants (HOCs) under equilibrium and rate limiting conditions. Sorption and desorption by soils and sediments are fundamental processes controlling fate and transport of less polar and nonpolar organic pollutants in surface aquatic and groundwater systems. Recent studies have shown that soils and sediments exhibit an array of HOC sorption phenomena that are inconsistent with an early partition model based on an assumption of homogeneous gel-like SOM. Increasing data have revealed that isotherm nonlinearity, varied sorption capacity, sorption–desorption hysteresis, and slow rates of sorption and desorption are characteristics for HOC sorption by soils and sediments. These phenomena have been shown to result from different types of condensed SOM that exhibit capacity limiting sorption processes. Recent findings of glass transition phenomena and the nonlinear HOC sorption by humic acids provide a scientific foundation for drawing an analogy between humic acids and synthetic organic polymers that supports a dual mode model for sorption by soils and sediments. Humic acid is glassy or rigid at temperatures lower than its glass transition temperature and exhibits relatively nonlinear sorption isotherms for HOCs. Fractionation and quantification of SOM indicate that soils and sediments contain significant amounts of black carbon and kerogen of different origins. These particulate organic materials have rigid 3-dimensional structures and are often less polar compared to humic substances. Limited studies show that black carbon and kerogen exhibit nonlinear sorption for HOCs and may dominate the overall nonlinear sorption by soils and sediments.     

Organic matter in the bottom sediments of the Ob Bay: Distribution,nature, and sources

The lateral variability of main geochemical parameters of dispersed organic matter (DOM) in the bottoms sediments of the Ob Bay was studied using materials of areal geological survey. It was found that they correspond to background compositions of estuarine-delta facies of the Western Arctic shelf, being mainly determined by the influx of river run-off and coastal abrasion. The distribution of DOM and its components is controlled by the hydrodynamic regime of the water area and grain-size composition of sediments. The molecular composition of hydrocarbon markers (n-alkanes, cyclanes, and arenes) confirms the dominant role of terrigenous humic material in the formation of DOM of the bottom sediments, while temporal stability of quantitative and qualitative geochemical characteristics indicates the stability of the Ob Bay ecosystem.     

金沙江(攀枝花段)水系沉积物中重金属的形态特征

采用连续提取法,并用原子吸收光谱法进行分析研究了金沙江攀枝花段水系沉积物中重金属的形态及分布特征。研究发现:①各重金属的形态以残渣态为主,离子交换态含量很少;②各元素的形态有自己的特点。铜在有机硫化物结合态中的含量较高,钴在碳酸盐结合态中的含量较高,铅锌钴的铁锰氧化物结合态均较高;③有效态对水环境质量具有潜在的危害。     

Distribution and sources of carbon,nitrogen, phosphorus and biogenic silica in the sediments of Chilika lagoon

The present study investigated the spatial and vertical distribution of organic carbon (OC), total nitrogen (TN), total phosphorus (TP) and biogenic silica (BSi) in the sedimentary environments of Asia’s largest brackish water lagoon. Surface and core sediments were collected from various locations of the Chilika lagoon and were analysed for grain-size distribution and major elements in order to understand their distribution and sources. Sand is the dominant fraction followed by silt + clay. Primary production within the lagoon, terrestrial input from river discharge and anthropogenic activities in the vicinity of the lagoon control the distribution of OC, TN, TP and BSi in the surface as well as in the core sediments. Low C/N ratios in the surface sediments (3.49–3.41) and cores (4–11.86) suggest that phytoplankton and macroalgae may be major contributors of organic matter (OM) in the lagoon. BSi is mainly associated with the mud fraction. Core C5 from Balugaon region shows the highest concentration of OC ranging from 0.58–2.34%, especially in the upper 30 cm, due to direct discharge of large amounts of untreated sewage into the lagoon. The study highlights that Chilika is a dynamic ecosystem with a large contribution of OM by autochthonous sources with some input from anthropogenic sources as well.     

Terrigenous organic matter sources in mid-pleistocene sediments from the orphan knoll,Northwest Atlantic Ocean

The concentration and composition of lignin-derived phenols, which are often used as biomarkers for terrigenous organic matter (OM) inputs, were examined in North Atlantic Ocean sediments from IODP core U1302A (50°9.985′N, 45°38.271′W, 3568 m water depth), Orphan Knoll, 650 km NE of St. John’s, Newfoundland, Canada for the period of ca. 1100–810 ka BP. Lignin-derived phenols were extracted from sediments using CuO oxidation which yielded eight characteristic phenols. The majority of sediments have low syringyl phenol to vanillyl phenol (S/V) ratios and high cinnamyl phenol to vanillyl phenol (C/V) ratios, suggesting predominant concentrations of gymnosperm-derived organic matter inputs from adjacent continents (most likely eastern Canada and possibly southern Greenland). The S/V values were lower for the period of ca. 958–840 ka BP relative to ca. 1090–1078, 1042–958 and 840–818 ka BP, indicating fluctuations in the proportion of angiosperm- and gymnosperm-derived lignin delivery to the ocean. The greater fraction of gymnosperms for the period of 958–840 ka BP likely reflects the response of vegetation in source regions to climate cooling in the early part of the mid-Pleistocene. Lignin-derived phenol concentrations also displayed high variability during the investigated period, which did not show positive correlations with magnetic susceptibility or Gamma Ray Attenuation density. Considering that a fundamental climate change (41–100 ka cyclicity) occurred within the mid-Pleistocene, large variations in abundance and composition of lignin-derived phenols in core U1302A is likely indicative of dynamic environmental conditions, reflected by the variability in both concentrations and types of vegetation on adjacent continents and/or different mechanisms to transport terrigenous organic matter to the deep ocean.     

Mercury in river sediments, floodplains and plants growing thereon in the drainage area of the Idrija mine, Slovenia

Half a millennium mercury production at Idrija is reflected in increased mercury contents in all environmental segments. The bulk of roasting residues from the middle of the 19th century to 1977 was discharged directly into the Idrijca River, and the material was carried at high waters to the Soca River and farther into the Adriatic Sea. It has been estimated that 45500 tons of mercury were emitted into the environment during the operating period of the mine, which ceased production in 1994. In the lower reaches of the Idrijca the riverine deposits with high mercury contents have been, and will be in the future a source of mercury polluted sediment. Stream sediments were monitored at the same locations along the Idrijca and Soca rivers （70 kin） every 5 years since 1991 （1991-2005）. Grain size distribution was determined by dry sieving and fractions for geochemical analysis were prepared （〈0.04 and 〈0.125 mm）. Soils on river terraces were sampled at 5 localities in the lower course of Idrijca. At two locations of the terrace profiles the samples of averaged meadow forage and plantain （Plantago lanceolata） were collected within a 50-meters radius. We found that there was no decrease in mercury concentration in active river sediments during the last 20 years. Upstream from the Idrija Town the mercury concentrations in active river sediments vary from 1 to 10 mg/kg （average 3.3 mg/kg）. From Idrija to Spodnja Idrija the mercury concentrations increase extremely and vary greatly （32-4,121 mg/kg, the average is 734 mg/kg）. From Spodnja ldrija to the Idrijca-Soca confluence is the average 218 mg/kg, and 57 mg/kg downstream in the Soca River sediments.     

Temporal variability in sources of dissolved organic carbon in the lower Mississippi river

Here we report on the temporal changes in the composition of dissolved organic carbon (DOC) collected in the tidal freshwater region of the lower Mississippi River. Lignin-phenols, bulk stable carbon isotopes, compound-specific isotope analyses (CSIA) and ¹³C nuclear magnetic resonance (NMR) spectrometry were used to examine the composition of high molecular weight dissolved organic matter (HMW DOM) at one station in the lower river over 6 different flow regimes in 1998 and 1999. It was estimated that the annual input of DOC delivered to the Gulf of Mexico from the Mississippi River was of 3.1 × 10⁻³ Pg, which represents 1.2% of the total global input of DOC from rivers to the ocean. Average DOC and HMW DOC were 489 ±163 and 115 ± 47 μM, respectively. ¹³C-NMR spectra revealed considerably more aliphatic structures than aromatic carbons in HMW DOC. Lignin phenols were significantly ¹³C-depleted with respect to bulk HMW DOM indicating that C₄ grass inputs to the HMW DOM were not significant. It is speculated that C₄ organic matter in the river is not being converted (via microbial decay) to HMW DOM as readily as C₃ organic matter is, because of the association of C₄ organic matter with finer sediments. The predominantly aliphatic ¹³C NMR signature of HMW DOM suggests that autochthonous production in the river may be more important as a source of DOC than previously thought. Increases in nutrient loading and decreases in the suspended load (because of dams) in the Mississippi River, as well as other large rivers around the world, has resulted in significant changes in the sources and overall cycling of riverine DOC.     

Distribution of selected trace elements in sediments of Pamlico river estuary,north Carolina

Sixty-eight samples of sediment collected on a variably-spaced grid pattern from Pamlico River Estuary of North Carolina were analyzed for As, Cd, Co, Cr, Cu, F, Ni, Pb, U, Zn, clay, and organic matter. The major objectives of the study were to determine background and anomalous levels of trace elements in the sediments, and the effects of human activities on concentration and distribution of trace elements in the sediments. Clay and organic matter are more concentrated near the center of the estuary. This causes the highest concentration of trace elements in the sediments to be located there also owing to their preferential uptake of these elements. Highest trace element concentrations were observed in clay and organic matter near industrial sites, housing developments, and tributary mouths that drain areas of human activity. The apparent increase in trace element contents of fine sediments in Pamlico River Estuary owing to human activities is 4 to 1,750 times normal background levels.     

Polycyclic aromatic hydrocarbons in sediments from the Pearl river and estuary,China: spatial and temporal distribution and sources

Polycyclic aromatic hydrocarbons (PAHs) were measured in surface sediments and dated core sediments from the Pearl river and estuary, China, to investigate the spatial and temporal variability of anthropogenic pollutants. The sediments from the sampling stations at the Guangzhou channel have the highest concentrations of PAHs, owing to contributions from the large amount of urban/industrial discharges from the city of Guangzhou. The significant decrease of PAHs concentrations in sediments from the Shiziyang channel is mainly attributed to the increasing degradation and desorption of low molecular weight PAHs and alkyl PAHs, and the dilution by less contaminated water and particles from the East river. The PAH contaminants were concentrated on the western side in the Lingding bay of the Pearl river estuary because of the hydrodynamic and sedimentation conditions. Based on the characteristics of the parent compound distributions (PCDs) and the alkyl homologue distributions (AHDs) of PAHs, the potential source of PAHs in sediments from each sampling station was identified. Results indicated that the pyrogenic (combustion) source, characterized by the abundance of parent PAHs, were predominant in the heavily contaminated station (ZB01) near the aging industrial area, and the petrogenic (petroleum- derived) PAHs were more abundant in the stations (ZB02, ZB03) adjacent to the petrochemical plant and shipping harbor. Sediments from Lingding bay show variable distributions of PAH composition and variety in the proportion of combustion and petrogenic sources for the PAHs in different stations. Perylene, a naturally derived PAH, was found to be highly abundant in less contaminated stations. Analysis of the dated sediments (²¹⁰Pb) indicates that higher PAH concentrations occurred in the sediments deposited after 1980, and higher fluxes of PAHs discharged to the Pearl river are found after 1990.     

δC and δD identification of sources of lipid biomarkers in sediments of Lake Haruna (Japan)

Organic materials in lacustrine sediments are from multiple terrestrial and aquatic sources. In this study, carbon (δ¹³C) and hydrogen isotopic compositions (δD) of phytol, various sterols, and major n-fatty acids in sediments at Lake Haruna, Japan, were determined in their solvent-extractable (free) and saponification-released forms (bound). The δ¹³C-δD distributions of these lipid molecules in sediments are compared with those of terrestrial C3 and C4 plants, aquatic C3 plants, and plankton to evaluate their relative contributions. δ¹³C-δD of free phytol in sediments is very close to that of phytol in plankton samples, whereas δ¹³C-δD of bound phytol in sediments is on a mixing line between terrestrial C3 plant and plankton material. Unlike phytol, no significant δ¹³C-δD difference between free and bound forms was found in sterols and n-fatty acids. δ¹³C-δD values of algal sterols such as 24-methylcholesta-5,22-dien-3β-ol in sediments are close to those of plankton, whereas δ¹³C-δD of multiple-source sterols such as 24-ethylcholest-5-en-3β-ol and of major n-fatty acids such as n-hexadecanoic acid in sediments are between those of terrestrial C3 plants and plankton samples. Thus, δ¹³C-δD distributions clearly indicate the specific source contributions of biomarkers preserved in a lacustrine environment. Free phytol and algal sterols can be attributed to phytoplankton, and bound phytol, multiple source sterols, and major n-fatty acids are contributed by both terrestrial C3 plants and phytoplankton.     

白音诺尔铅锌矿区河流沉积物重金属的形态分布特征

为了研究内蒙古赤峰市巴林左旗白音诺尔铅锌矿区采矿对哈力黑河生态环境造成的影响,从上游向下游采集了6个河流沉积物样品,测定其pH、LOI、粒度以及As、Cu、Pb、Zn、Cd等5种重金属的总量和赋存形态,并对测试结果进行分析。研究结果表明:（1）1#尾矿库是造成沉积物中Pb、Zn和Cd等重金属显著升高的主要原因。（2）沉积物重金属与粗粉砂（16~63 μm）的相关系数为0.79~0.95,表明重金属易富集于粗粉砂上,而沉积物的pH和有机质对重金属总量的变化影响不显著。（3）沉积物中As和Pb以残渣态和铁锰结合态为主,分别占总量的78.82%~89.87%和36.96%~78.20%。Cu和Zn以残渣态、强有机结合态和铁锰结合态为主,分别占总量的76.38%~85.96%和74.94%~90.34%。Cd则以离子交换态、碳酸盐结合态和强有机结合态为主,占总量的51.15%~79.53%,而离子交换态Cd占了总量的5.72%~49.63%。因此,Cd对河流生态环境的潜在威胁最大。（4）离子交换态Cd与沉积物pH相关系数为-0.813,两者呈极强负相关性。当沉积物pH由弱酸性转化为弱碱性时,离子交换态Cd含量从33.44%降低至5.72%,显著减小。